Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 1 Acta geológica lilloana Volumen 21 — Suplemento — Abstracts of the 9th International Conference on Fluvial Sedimentology Fundación Miguel Lillo — 2009 — 2 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 Acta geológica lilloana Serie publicada por la Fundación Miguel Lillo, que tiene como objetivo divulgar trabajos originales sobre ciencias geológicas y afines. Los trabajos son evaluados por árbitros externos e internos. Correo electrónico: actageologicalilloana@gmail.com I S S N 0 5 6 7 – 7 5 1 3 © 2009, Fundación Miguel Lillo. Todos los derechos reservados. Fundación Miguel Lillo Miguel Lillo 251 (4000) San Miguel de Tucumán Argentina Telefax +54 381 433 0868 www.lillo.org.ar Editora de Acta geológica lilloana: Ana Fogliata Secretaria editorial: Lucía Ibañez Secretaria del Área Geología: Rosa Molina Editor gráfico: Gustavo Sánchez Comité editorial: Dra. Ana S. Fogliata (Coordinadora) (Fundación Miguel Lillo, Facultad de Cs. Naturales, UNT) Dra. Lucía Ibañez (Secretaria) (Fundación Miguel Lillo, Facultad de Cs. Naturales, UNT) Dra. Judith Babot (Prosecretaria) (Fundación Miguel Lillo, Facultad de Cs. Naturales, UNT) Dr. Pablo Grosse (Fundación Miguel Lillo, CONICET) Dr. Hugo A. Carrizo (Fundación Miguel Lillo) Dr. Sergio Georgieff (Facultad de Cs. Naturales, UNT, CONICET) Editores asociados: Dr. Carlos L. Azcuy (CONICET) Dr. Eduardo Piovano (CONICET, Universidad Nacional de Córdoba) Dr. Franco M. Tortello (CONICET, Universidad Nacional de La Plata) Publicación indexada en las siguientes bases de datos: Bulletin Signalétique, Biosis Previews, Latindex, Periodica, Referativnyi Zhurnal Canjes: Centro de Información Geo-Biológico del Noroeste Argentino, Fundación Miguel Lillo, Miguel Lillo 251, (4000) San Miguel de Tucumán, Argentina. Correo electrónico: biblioteca@lillo.org.ar Ref. bibliográfica: Acta geol. lilloana 21, Suplemento, 2009. Periodicidad: un volumen anual en dos números. Impresión: Artes Gráficas Crivelli. Propiedad intelectual Nº 315450. Prohibida su reproducción total o parcial. Impreso en la Argentina. P r i n t e d i n A r g e n t i n a . Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 3 Abstracts of the 9th International Conference on Fluvial Sedimentology 24-28 August, 2009 San Miguel de Tucumán, Argentina Organization: Universidad Nacional de Tucumán Fundación Miguel Lillo ORGANISING COMMITTE Sergio M. Georgieff — Convenor — Sebastián Moyano — Secretary — María Soledad Bustos — Finance — Gerardo E. Bossi — Scientific Coordinator — Lucía M. Ibañez — Publication Coordinator — María Eugenia Vides — Scientific Programme Organizer — Guillermo F. Aceñolaza — Excursion Coordinator — 4 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 9th ICFS is sponsored by AGENCIA NACIONAL DE PROMOCIÓN CIENTÍFICA Y TÉCNICA ASOCIACIÓN ARGENTINA DE SEDIMENTOLOGÍA ASOCIACIÓN PALEONTOLÓGICA ARGENTINA COLEGIO DE GRADUADOS EN CIENCIAS GEOLÓGICAS DE TUCUMÁN CONSEJO DELIBERANTE DE SAN MIGUEL DE TUCUMÁN ENTE CULTURAL TUCUMÁN ENTE TUCUMÁN TURISMO FACULTAD DE CIENCIAS NATURALES E INSTITUTO MIGUEL LILLO FUNDACIÓN MIGUEL LILLO HONORABLE LEGISLATURA DE TUCUMÁN INSTITUTO DE ESTRATIGRAFÍA Y GEOLOGÍA SEDIMENTARIA GLOBAL INSTITUTO NACIONAL DE AGUA DE LA NACIÓN INTERNATIONAL ASSOCIATION OF SEDIMENTOLOGISTS MUNICIPALIDAD DE SAN MIGUEL DE TUCUMÁN SECRETARIA DE CULTURA DE TUCUMÁN UNIDAD DE NEGOCIOS DE LA UNIVERSIDAD NACIONAL DE TUCUMÁN Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 5 Preface and Acknowledgements This volume contains abstracts presented to the 9th International Con- ference on Fluvial Sedimentology, held at the Universidad Nacional de Tucumán in San Miguel de Tucumán, Argentina between 24th and 28th August, 2009. The 9th ICFS was co-organized between Universidad Na- cional de Tucumán and Fundación Miguel Lillo. This volume is a Suplemento, Special Publication, of the Acta Geológica Lilloana Journal, Miguel Lillo Foundation. We should like to thank all those involved in the organization of the 9th ICFS: The abstracts were printed due to the generous support of Miguel Lillo Foundation; special thanks to the Honorable Advisor Commission, its President Dr. Jorge L. Rougés, the General Director, Lic. Ana María Frías de Fernández, the Director of Geology, Dr. Ana Lía Ahumada, the former Director, Dr. Hugo A. Carrizo, and the Chief Editor of Acta Geológica Lilloana, Dr. Ana S. Fogliata. The volume has been edited by Dr. Lucía M. Ibañez. Special thanks to Lic Gustavo Sánchez, who provided the final fit to print this volume. Mrs. Macarena Cárdenas Ypa realized a hard and tireless work in the organization of Conference venue, travels and accommodations of Key Note Lecturers. Lecturers provided interesting keynotes and agreed to form the Award Committee. Field excursion leaders are thanked for the time and effort they devot- ed to planning, running and preparing the excursions and the field guides. The Agencia Nacional de Promoción Científica y Técnica supported the organization and travels of Lecturers. The International Association of Sedimentologists sponsored travel grants for students. The Ente Tucumán Turismo de Tucumán provided hotel accommoda- tions for Lecturers. The Instituto de Estratigrafía y Geología Sedimentaria Global spon- sored the Conference Venue and others additional supports involved in the organization. The Unidad de Negocios of the Universidad Nacional de Tucumán helped the organizers with the finances; special thanks to its Director, Dr. Andrea Guraiib, Ms. Andrea Cavanna and Mr. Mario Abaca. The Municipalidad de San Miguel de Tucumán provided posters and pamphlets. SERGIO M. GEORGIEFF Convenor, 9th ICFS 6 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 Field Excursion Leaders Pre – Conference Field Excursions 1.- From the Cretaceous rift to the Pliocene Foreland basins (NW Ar- gentina): Tectonic and Sedimentation Cecilia Del Papa - CONICET. 2.- Evolution of the Fluvial System in The Tertiary Andean Foreland Basin (Precordillera, Argentina) Carlos O. Limarino. Universidad de Buenos Aires – CONICET. 3.- Fluvial Syntectonic Features in Cenozoic Pampean Deposits Gerardo E. Bossi, Sergio M. Georgieff and Sebastián Moyano, Universidad Nacional de Tucumán – CONICET. Mid – Conference Field Excursions 4.- Mezoic and Cenozoic Fluvial Deposits of Northern Tucumán Gerardo E. Bossi and Sebastián Moyano, Universidad Nacional de Tucumán - CONICET. 5.- San Javier - Raco, Precambrian, Creaceous-Neogene Guillermo Aceñolaza, INSUGEO - CONICET. Universidad Nacional de Tucumán 6.- Tafí and Amaicha Valleys: Paleoclimatic and Paleoenvironmental Neogene Evolution Miriam M. Collantes, Lucía M. Ibañez, and José Busnelli, Universidad Nacional de Tucumán – Fundación Miguel Lillo. Post – Conference Field Excursions 7.- Paraná River, Miocene to Present Oscar Orfeo, CONICET – Universidad Nacional del Nordeste. 8.- Sedimentary Evolution of the Golfo San Jorge Basin, Central Pata- gonia, Argentina José Paredes, Universidad Nacional de la Patagonia San Juan Bosco. Responsibility for the contents of these abstracts rests upon the authors and not the Miguel Lillo Foundation nor Universidad Nacional de Tucumán. Data presented and conclusions developed by the authors are for infor- mation only and are not intended for use without independent substantiating investigation on the part of the potential user. When conference abstracts are cited, this volume should be referred to as: Lucía M. Ibañez (Ed.), Abstracts, 9th International Conference on Fluvial Sedimentology. Acta geológica lilloana 21 (2), Suplemento, 2009. San Miguel de Tucumán. Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 7 Keynotes generated in different sized bed sediment. ON THE INTERACTIONS BETWEEN The talk will conclude with examples of how TURBULENT FLOWS, SEDIMENT bedforms are key in understanding some of TRANSPORT AND BEDFORM the larger-scale aspects of river channel mor- DEVELOPMENT IN ALLUVIAL CHANNELS: phodynamics, and highlight some areas of 28 YEARS ON current research that raise issues concerning Jim Best bedform development in both laminar and Departments of Geology and Geography and Ven Te turbulent flows and the scaling of bedforms Chow Hydrosystems Laboratory, University of Illinois, within unidirectional flows. Urbana, Illinois 61801, USA. jimbest@illinois.edu References Understanding the interactions between the trinity of turbulent flow, mobile sediment Jackson, R.G. (1976) Sedimentological and flu- and bedform development lies at the heart of id-dynamic implications of the turbulent interpreting fluvial form and process. This bursting phenomenon in geophysical flows. J. Fluid Mech. 77, 531-560. ‘trinity’ was used as the basis of the seminal Leeder, M.R. (1983) On the interactions be- paper by Leeder (1983) that arose from the tween turbulent flow, sediment transport 2nd ICFS, held in Keele, UK, in 1981. These and bedform mechanics in channel ized ideas were grounded in the exciting develop- flows. In: Int. Ass. Sedimentol. Spec. Publ. ments that were made in turbulent boundary (Eds. Collinson, J.D. and Lewin, J.), 6, 5- 18. layer research in the late 1970’s, with the paper of Jackson (1976) being one of the first that attempted to link turbulent bound- ary layer structure with sediment transport, ROLE OF CONTINENTAL MARGIN INCISED- bedform generation and stability. Since these VALLEY SYSTEMS IN THE EMERGING advances in our thinking in the 1980’s, the SOURCE-TO-SINK PARADIGM tools that we can use to investigate the com- Mike Blum plex feedbacks in this trinity have improved ExxonMobil Upstream Research Company, Houston, beyond our 1970/80’s dreams! - in laborato- Texas ry technology, field methods and numerical tools. Where has this brought us and what The emerging source-to-sink paradigm are the key issues that now face us in quanti- seeks to develop a holistic understanding of fying, understanding and predicting the mor- sediment production, transport, and storage phodynamics of alluvial bedforms? from source regions in tectonic hinterlands This talk will review some of the key de- to sinks within deep ocean basins. River sys- velopments in the field of alluvial bedform tems are an important component, the “to” morphodynamics over the past 28 years, and in source-to-sink: this presentation discusses show results from the laboratory (using a how the evolution of incised-valley systems range of optical and acoustic techniques), in response to allogenic controls play a fun- field (highlighting acoustic methods) and damental role in modulating sediment trans- computational modelling (LES realizations of fer across continental margins. flow over bedforms). This review will encom- Continental margins incised valleys form pass the feedbacks between bed morphology in response to sea-level fall, as fluvial sys- and large-scale vorticity, the interactions be- tems extend across newly emergent shelves to tween bedforms, the influence of fine-grained the lowstand shoreline and shelf margin. sediment on turbulence modulation within the But what is the shelf, anyway? It has long flow, and some commonalities of bedforms been recognized that modern shelf margins 8 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 correspond with the depth of sea-level fall enhance incision, whereas sea-level rise and during late Pleistocene lowstands, and nu- flooding of the shelf will have the opposite merous studies illustrate the important role effect. Second, the development of incised of deltaic progradation during lowstands to valleys results in sediment unloading and construct the shelf margin. However, a grow- loading, which likely produces a cyclical ing body of evidence now suggests that pattern of isostatic uplift and subsidence as shelves are fundamentally terrestrial land- well. Cyclical uplift and subsidence, either scape elements (although they clearly have a due to hydroisostasy or sediment unloading marine overprint). The view taken here is and loading, should amplify valley incision that shelves are essentially the lowstand and filling, play a key role in development of coastal plain, river long profiles are graded valley-fill architecture, and play and impor- to shelf margins, and shelf margins are sim- tant role in sediment export or storage. ply the end of the fluvial sediment dispersal system. In this view, the surface across which rivers extend during sea-level fall is a UNIT-BAR DEPOSITS IN ANCIENT RIVER- byproduct of the fluvial system itself, part of CHANNEL ALLUVIUM the equilibrium profile, rather than a surface John Bridge inherited from a different suite of processes. Department of Geological Sciences, Binghamton Uni- The evolution of linked coastal-plain and versity, Binghamton, NY 13902-6000. cross-shelf incised-valley systems modulates source-to-sink sediment routing from ero- Modern river-channel deposits comprise sional continental interiors to deepwater en- flood-generated sedimentation units, unit-bar vironments through the storage and export deposits, and compound-bar deposits. Al- of sediments. Incised valleys form in a step- though all of these scales of deposits are rec- wise manner, with short periods of incision ognized in all modern river-channel depos- punctuated by extended periods of lateral its, unit-bar deposits are not commonly re- channel migration and valley widening, and ported from ancient river-channel deposits. with contemporaneous deposition of chan- However, unit-bar deposits have been recog- nel-belt sands. Short periods of incision like- nized explicitly in ancient river-channel de- ly produce an insignificant amount of sedi- posits by McCabe, Jones, Bridge et al, and ment export, but periods of lateral channel Haszeldine. Ancient unit-bar deposits have migration, valley widening, and channel- also been misinterpreted by Allen, Roe and belt deposition significantly increase down- Hermanson. One of the reasons for the ap- stream flux, such that periods of fluvial dep- parent lack of unit-bar deposits in ancient osition within incised valleys correspond to alluvium is because they are very similar to increased sediment delivery to the shelf mar- flood-generated units. Similarities include: gin and beyond. Moreover, drainage basins both types of stratasets are dominated by commonly merge as channels extend across medium-scale trough cross strata formed by the shelf, such that signals of increased or dunes superimposed on bar surfaces; decreased flux of sediment to the shelf mar- stratasets are decimeters to meters thick; gin and beyond may reflect geomorphic re- stratasets commonly fine upward from an sponse to sea-level change —the merging of erosional base; stratasets commonly have drainages as they transit a broad shelf— stratal discontinuities with overlying and rather than changes in sediment supply from underlying stratasets. Differences are: unit- the hinterland. bar stratasets are commonly mound-shaped High-frequency cyclical isostatic adjust- or dip downstream, and; bases of medium- ments to changes in water and sediment scale trough cross sets are variable in dip loads may be intrinsic to the evolution of and rarely approach the angle of repose, incised-valley systems. First, isostatic uplift thus giving rare large-scale cross strata asso- of the shelf in response to sea-level fall will ciated with the avalanche face of a unit bar. Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 9 Here, ancient unit-bar deposits are recog- The sandstone bodies hydrocarbon-bear- nized in re-interpreted ancient alluvium. ing belong to the Castillo and Bajo Barreal Formations (Chubut Group). These units are formed by fluvial channel belts with thick- SEDIMENTOLOGICAL AND STRATIGRAPHIC nesses from 2m to 10-12m and widths be- MODELS: INTEGRATION AMONG SCIENCE, tween few tens of meters to 600m. The TECHNOLOGY AND OIL INDUSTRY. channel belts flowed onto a silt-sandstone EXAMPLES IN OIL FIELD OF GOLFO SAN floodplain toward east or southeast as iso- JORGE BASIN, CHUBUT AND SANTA lated fluvial belts. The floodplain deposits CRUZ PROVINCES, ARGENTINA are represented by splays and splay-channels Luciano Di Benedettto with a high proportion of volcanic ashes and YPF SA, Av. Libertador 520, Km3, 9000 - Comodoro volcaniclastic deposits like surges and la- Rivadavia, Argentina. ldibenedettor@ypf.com hars. Even channel belts show high propor- tion of volcaniclastic and pyroclastic materi- At the present, Argentina has five main als. Thus, the poro-permeability characteris- oil basins and even some new efforts are con- tics are very variable into the same sand- ducted to explore its marine platform. YPF stone bodies and the induced fractures are SA is working in the all basins and has also normal in the primary oil recovery. realized exploration in the named frontier The sedimentological and stratigraphic basins. studies allowed to understand the deposition- Since 1907, the Golfo San Jorge Basin al setting of Chubut Group in the The Guad- (GSJB) is the pioneer oil basin in Argentina al Area through the merge of surface and and already has produced 0,3 Mbbl/days and subsurface data (outcrops, wells, 3D seismic, 14,713Mm3/days gas. The main production geochemistry of oils, mudstone composition, of oil is coming from Cretaceous fluvial de- petrography, and poro-permeability studies). posits. The principal characteristic of the oil field production is a rapid development, for instance since middle ’90 the drillings were AN OVERVIEW OF EROSION AND around 200 wells per year, only by YPF SA. SEDIMENTATION PROBLEMS IN FLUVIAL These intensive developments become a daily SYSTEMS OF NORTHERN ARGENTINA challenge to optimization the production Hector Daniel Farias and keep hydrocarbon reserves. Instituto de Recursos Hídricos, Universidad Nacional The GSJB was an extensional basin dur- de Santiago del Estero, Argentina. ing Early Jurassic and Middle Cretaceous; it became compressive from Late Cretaceous The North-West region of Argentina but mainly during Tertiary. The sedimentary shows a variety of fluvial systems and associ- column is formed by fluvial, lacustrine, vol- ated erosion-sedimentation problems. Most caniclastics and volcanic deposits. The basin of the large scale watersheds have their hosts deposits of economic importance in heads along the Andean and Sub-Andean the sandstone sequences in all of their Creta- zones, and they are characterized by a very ceous lithostratigraphic units. heavy sediment yield. On the other hand, the The studies realized in these deposits are lower reaches of the rivers, mainly located focused to understand the external and inter- on the Grand Chaco plain area, are charac- nal controls of the plays. The development terized by a wide range of morphological of quantitative models and the comprehen- processes, among others, net sedimentation sion of tectonosedimentary evolution using and channel aggradation. new technologies and optimizing the avail- Several problems related with erosion able resources (field, lab and research) are and sedimentation processes in the study the main goals to improve the prediction of area are examined from an engineering new plays. point of view. 10 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 For instance, the continuous aggradation Large river systems have posed a consid- of the Pilcomayo River, which defines the erable challenge to Science, owing to the international boundary between Argentina magnitude and complexity of factors that and Paraguay countries, causes several prob- regulate their dynamics. For instance, the lems. In fact, channel shifting and avulsion Paraná has vast volumes of solid and liquid processes difficult the river water resources discharge, a subtropical climate with a management for several uses in both coun- range of temporal and spatial variability, a tries and define a challenge to river engi- diversity of relief and basin lithology, rapid neers about the location and features of dis- changes in the fluvial form, extensive flood- charge diversion works. plains, and considerable influence of both Bermejo River also flows from the Andes autochthonous and allochthonous tributar- to Chaco and the sediment yield of its water- ies. Additionally, many human imparted shed is among the world highest ones. The changes have already exerted significant in- lower reaches of the river show a meander- fluence on the system, including the effect of ing pattern with a remarkable trend to devel- large dams, rectified channels, dredged op lateral migration processes, which causes channels, fluvial transit alterations, intensive a lot of problems in works located in the riv- development of ports, building of hydroelec- er environment, such as water intakes, tric plants, the rapid development of cities, bridge crossings, agriculture land loss due to and changes in land-use, have or are compli- bank erosion, etc. cating the functioning of the entire system. Most of these problems are discussed in The study of modern large fluvial envi- the presentation, along with erosion-sedi- ronments is very much an incipient activity. mentation aspects observed in other interest- This paper provides an outline of the re- ing fluvial systems in the region, such as Ju- search conducted by a large multi-national ramento-Salado and Salí-Dulce. group of scientists, who have begun to iden- tify some key processes operating within the Paraná System. This research for example FATHER OF THE WATERS: UNLOCKING THE has begun to address questions over mixing SECRETS rates and flow structure at the Paraná-Para- Oscar Orfeo,1 Daniel Parsons2 guay confluence, the influence of bedforms 1 CONICET and Universidad Nacional del Nordeste. on channel scale flow processes and the 2 University of Leeds, UK. morphodynamics and sedimentology of large compound bars. This synthesis will highlight The Paraná River System, the “Father of key findings and point to future research the Waters” (in translation from aboriginal that aims to unlock more secrets of this Guaraní), is the 6th largest river system in wonderful fluvial system. the world and as such is the most significant in southern South America. The Paraná, as well posing as a flooding risk for millions of HISTORICAL PLANIMETRIC CHANNEL people who live on its floodplain, also pro- CHANGES IN AN ITALIAN RIVER: THE vides a water supply, hydro-power, and a CECINA RIVER major trade conduit in the region. Despite Liliana B. Teruggi,1 Massimo Rinaldi2 its clear economic and social importance we 1 Dipartimento di Ingegneria Civile e Ambientale, have a limited understanding of how many Università degli Studi di Firenze, Via S. Marta, 3 components of the system functions and there – 50139 Florence, Italy. lteruggi@dicea.unifi.it is thus a vital need to improve our knowl- 2 DICeA, Università degli Studi di Firenze. edge of channel morphodynamics and im- prove our predictive capacity and thus ensure Fluvial planimetric form is affected by sustainable development of this immense continuous changes as a consequence of watershed. channel adjustments in response to varia- Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 11 tions in the balance between sediment supply mogeneous reaches, and a series of basic and transport capacity. Channel changes may planimetric parameters, such as channel be caused by geomorphic response to natu- width, sinuosity and braiding index, have ral changes (e.g. climate) or human distur- been measured. This analysis has made it bances. Human activities have had a strong possible to measure temporal and spatial impact on most of the European alluvial riv- changes in Cecina River channel. In some ers over the last centuries. representative reaches, changes in land-use Nowadays, advances in Geographical In- and forest cover floodplain were analyzed formation System (GIS) technology has sig- and quantified by comparing aerial photo- nificantly increased the contribution that his- graphs using GIS data processing. torical data can give to the analysis of chan- Results indicate that all reaches have nel planform changes. been subjected to progressive channel nar- The aims of this study are twofold: (1) to rowing since 1883. Channel width measures develop and apply a systematic methodology indicate that the total channel narrowing for measuring and analyzing channel changes varies between 60-80% of the initial width in by remote sensing and GIS technology; (2) to the period of time analyzed. This adjustment describe and interpret in a case study the spa- is characterized by two phases: the first one tial and temporal patterns of channel changes started at the end of 19th century, the second which have affected the Cecina River. and more intensive one began at the end of The Cecina River is located in southern 20th century. The main causes of Cecina Tuscany (Central Italy). It is a gravel bed channel changes are associated with man- river with large alternating lateral bars, 79 induced activity such as sediment mining km long, and has a drainage area of about and catchment land use changes (e.g. refor- 900 km² characterized by a Mediterranean estation). It is observed that channel narrow- climate. ing is associated with a progressive increase A Geographical Information System has in sinuosity, in some reaches with a change been developed, and historical maps and from a multithread pattern towards a sinu- aerial photographs of different scales and ous-meandering configuration. All the mea- dates have been used to identify, measure and surements are used to analyze in detail the analyze planimetric channel changes. spatial and temporal trends in planimetric The active channel was defined and digi- adjustments and ultimately to derive a con- talized from all the aerial photographs. The ceptual evolution model illustrating the spa- river course was divided into relatively ho- tial and temporal trends of adjustments. 12 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 Abstracts sedimentary depositional heterogeneity of LOWER PALEOZOIC FLUVIAL DEPOSITS OF these formations has its impacts on their ARABIA: FACIES, ENVIRONMENTS AND aquifer and reservoir characteristics. DEPOSITIONAL STYLES, SAUDI ARABIA Osman Abdullatif Earth Sciences Department, KFUPM. FLUVIAL DYNAMICS, ALLUVIAL osmanabd@kfupm.edu.sa ARCHITECTURE AND PALAEOHYDROLOGY OF AXIAL AND TRANSVERSE DRAINAGE The fluvial deposits in the lower Paleozoic SYSTEMS IN AN EXTENSIONAL SETTING: succession in Saudi Arabia are dominantly LOS ADOBES FORMATION (APTIAN), siliciclastic sediments that are mostly sand- CAÑADÓN ASFALTO BASIN, ARGENTINA stone dominated with subordinate siltstone or José Oscar Allard,1 José Matildo Paredes,1 Raúl mudstone facies. These lower Paleozoic rocks Eduardo Giacosa1, 2 are exposed locally nonconformably on the 1 Dpto. de Geología, Facultad de Ciencias Naturales, Arabian Shield basement complex rocks and Universidad Nacional de la Patagonia ¨San Juan also as a long, curve-linear belt around the Bosco¨, Ruta Provincial Nº 1 S/N Km. 4, (9000) Arabian Shield in central Saudi Arabia. On Comodoro Rivadavia, Chubut Argentina. and around the Arabian Shield, the main low- 2 SEGEMAR, Delegación Regional Comahue, CC 228 er Paleozoic siliciclastic fluvial deposits in- (8332), General Roca, Río Negro, Argentina. clude the Siq Formation, Yatib Formation, Quweira Formation and Saq sandstone For- The recognition of axial and transverse mation in the central and northwestern parts drainage systems in extensional settings re- and the Wajid Formation in the southwestern quires a careful analysis of distribution and part. The Arabian Shield, which consists of scale of fluvial sandstone bodies, palaeocur- igneous and metamorphic metasedimentary rent data and changes in fluvial styles across and metavolcanic rocks, is the main sediment the depocentre. The variable slope and extent detrital sources. In addition, recycled sedi- of the channels network can be interpreted by ments represent a secondary source. These variations in sediment flow and discharge of fluvial formations show similarities and dif- both systems. The fieldwork is based on the ferences in their facies, lithology, texture and analysis of 114 fluvial sandbodies of the Bar- composition, however, all seem to be charac- das Coloradas Member (Los Adobes Forma- terized by sand dominated stream system tion) in the Paso de Indios depocenter of the with little or scarce fine sediments. Moreover, Cañadón Asfalto Basin, covering an area of the fluvial formations show variations in fa- 420 km2. Major normal faults of the area are cies types, architecture and their abundances NNW-SSE oriented, and the palaeocurrent and their vertical and lateral stacking pat- analysis reveals three main regional sediment terns. Different factors appear to have influ- flow directions: W-NW (transverse), S-SW enced the sedimentation of these formations (axial) and E-SE (major trunk system). The in terms of facies and depositional styles of succession consists of five lithofacies associa- their stream systems. These factors include tions (bar deposits, talweg fill deposits, complex controls varying from tectonics, sed- abandoned channel, proximal floodplain and iment source/basin relief, climate, weather- distal floodplain) and eight architectural ele- ing history and sediment supply. All these fac- ments (channel, gravel bed form, sand bed tors, in addition to stream autocyclic process- form, dowstream and lateral accretion mac- es, have contributed to facies and sequence de- roforms, hollow, top bar hollow and overbank velopment of these formations from their fines). Dominance of multi-storey, broad rib- proximal to distal depositional setting. The bons (61%) and narrow sheets (38%) reflect Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 13 bank resistance and rapid filling. Braided San Jorge basin. Ground Penetrating Radar sandstone bodies (85%), low sinuosity fluvial and vertical trenches were carried out in the sandstone bodies (12%) and meandering valley to characterize the subsurface stratig- channels (3%) were recognized. Axial sand- raphy. GPR transects allowed us to identify stone bodies show a mean thickness (T) of six radar facies: 1) subhorizontal, 2) low 5.9m, the mean true width (W) increases angle, 3) high angle, 4) concave, 5) convex, downstream from 25m to 109m, and their W/ 6) irregular and discontinuos. Three radar T ratio changes from 14.8 to 42.2 and a me- facies associations were defined: 1) channel, andering system develops downdip. The mean 2) channel fill deposits and 3) bar deposits. discharge of the axial system decreases The three-dimensional organization of radar downdip from 83 m3/s to 49m3/s, as result facies and superficial features (e.g. braid of infiltration and evaporation. The thickness bars) are consistent with a braided pattern. of transverse systems increases downstream The width of the river varies from 40 m to from 3.5m to 6.2m; their mean width (W) 260 m, braid bars ranges from 50 m to 77 range from 40m to 86m. A maximum bank- m in width and are 79 m-266 m long. full discharge (mbd) of 1535m3/s was ob- Specific stream power index (SSP) is de- tained at the downstream point of the conflu- fined as the Stream Power/Width of the ence zone with a transverse tributary system channel belt. SSP data were obtained in five that have a mbd of 1314 m3/s. In a basinward positions along the course of the river. Al- direction the axial channel network links to a though the river behaves as a braided river regional trunk system draining to the E-SE, the along their entire course, it shows systemat- later having a mbd of 4143 m3/s. The pro- ical change in the braiding index and SSP, posed sedimentary model is characterized by defining aggradational and degradational transverse tributaries that join an axial drain- zones along the course. Degradational zones age system, and a major trunk system basin- are characterized by narrow valley widths, ward. The fluvial system records very impor- they have values of SSP of 0.0156 m2/s and tant changes in water discharge (short and 0.00547 m2/s. The largest SSP value is ob- sharp floods) and migration by avulsion tained where the river crosses the volcanic mechanism. basement, which is also the place where the valley river is narrowest. Aggradational zones show wider valleys, and have SSP val- VOLCANIC BEDROCK MORPHOLOGY AS A ues of 0.00049 m2/s, 0.00315 m2/s and CONTROL ON FLUVIAL PATTERN IN A 0.000317 m2/s. SEMI-ARID SETTING The spatial distribution of aggradational José Oscar Allard,1 Alejandro Montes,1, 2 and degradational zones along the course of José M. Paredes,1 Gustavo Gabriel Bujalesky2 the braided river is interpreted as a response 1 Dpto. de Geología, Facultad de Ciencias Naturales, of the river to the location of the volcanic Universidad Nacional de la Patagonia ¨San Juan basement along the course. Both the braided Bosco¨, Ruta Provincial Nº 1 S/N Km. 4, (9000) pattern and the SSP values evidence the de- Comodoro Rivadavia, Chubut Argentina. velopement of degradational zones where the 2 Centro Austral de Investigaciones Científicas (CA- resisting power stream power. Downstream changes in the fluvial pat- tern can be imposed by lateral changes in the nature of the substrate, or bedrock proximity. This study analyzes an ephemer- al, braided channel that cross an uplifted block of Jurassic basement at Bahía Busta- mante, in the northern margin of the Golfo 14 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 other stratigraphic intervals mainly from the ALTERNATING FLUVIAL STYLES WITHIN early to middle Pennsylvanian, while fluvial THE MARITIMES BASIN COMPLEX OF styles characteristic of semiarid to arid envi- ATLANTIC CANADA: A RECORD OF ronments are dominant in the lowermost and EQUATORIAL CLIMATE CHANGE DURING uppermost portion of the studied interval. THE LATE PALEOZOIC ICE AGE The recognition of these changes in fluvial Jonathan P. Allen,1 Christopher R. Fielding,1 Martin style from one stratigraphic interval to the R. Gibling,2 Michael C. Rygel3 next suggests that systematic changes in pa- jonathan.allen@huskers.unl.edu leoclimate of at least regional extent are pre- 1 Department of Geosciences, University of Nebras- served within the Maritimes Basin. Addition- ka-Lincoln, Nebraska, 68588, USA. ally, these intervals broadly coincide with 2 Department of Earth Sciences, Dalhousie University, major periods of southern hemisphere glaci- Halifax, Nova Scotia B3H 3J5, Canada. ation. Similar periods of fluvial instability 3 Department of Geology, SUNY Potsdam, Potsdam, are recognized within low latitude fluvial New York, 13676, USA. systems within the Cenozoic during periods of major climatic transitions and the fluvial The Maritimes Basin complex of Atlantic successions within the Maritimes may record Canada preserves a thick stratigraphic suc- a similar, although highly time-averaged, cession deposited within a low latitude, pre- response. The recognition of punctuated peri- dominantly continental setting during the ods of strongly seasonal paleoclimate repre- Late Paleozoic. Within the Maritimes Basin, sented by the newly described fluvial style a newly recognized fluvial style has been uti- may aid in refining the paleoclimate evolu- lized in order to interpret paleoclimatic tion of similar successions elsewhere in the changes during the Late Paleozoic. This flu- paleotropics. vial style is characterized by 1) erosionally based sandstone bodies that display complex and abrupt lateral variations of sandstone MULTIPLE VALLEY FILLS FROM THE LATE and pedogenic mudstones, 2) an abundance QUATERNARY RECORD OF THE TUSCAN of sedimentary structures deposited by high COASTAL PLAIN (ITALY) flow conditions such as plane bedding and Alessandro Amorosi,1 Veronica Rossi,1 Giovanni convex-upward antidune stratification, 3) Sarti,2 Roberto Mattei,2 Serena Giacomelli2 complex internal stratification produced by 1 Dipartimento di Scienze della Terra e Geologico- plant sediment interactions, and 4) in situ Ambientali, Università di Bologna, Via Zamboni 67, arborescent trees preserved within densely 40127, Bologna, Italy. alessandro.amorosi@unibo.it, spaced groups that are consistently tilted in veronica.rossi4@unibo.it a downflow orientation. These characteris- 2 Dipartimento di Scienze della Terra, Università di tics have been interpreted to represent fluvial Pisa, Via Santa Maria 53, 56126 Pisa, Italy. sandbodies deposited under a tropical cli- sarti@dst.unipi.it matic regime characterized by flashy, strongly seasonal discharge. Three consecutive, time-equivalent valley The recognition of this distinct fluvial fills of Lateglacial-Holocene age (13 to 8 cal style has allowed for a refinement of the pa- kyr BP) were identified in the Tuscan coastal leoclimatic evolution of the Maritimes Basin. plain, across a 30 km long transect approx- Four discrete stratigraphic intervals have imately parallel to the present Tyrrhenian been recognized lasting from 3-6 m.y. where Sea shoreline. From South to North, the Arno this fluvial style is prominent, suggesting valley fill is 35-40 m thick and 5-7 km wide, that a subhumid, strongly seasonal paleocli- the Serchio valley fill is 15-20 m thick and 7- mate was the dominant imprint on these pre- 8 km wide, while the Camaiore valley fill is served successions. Fluvial channel bodies 20-30 m thick and 8-10 km wide. The three characteristic of humid conditions dominate valley fills display remarkably similar facies Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 15 architecture, with basal fluvial deposits over- lain by a variety of transgressive, mud-dom- DEVELOPMENT AND EVOLUTION OF A inated coastal plain and estuarine deposits. LATE QUATERNARY FLUVIAL CHANNEL The valley bodies are capped by a sheet-like, BELT: IMPLICATIONS FOR THE late transgressive succession of shoreline INTERPRETATION OF ANCIENT sands grading vertically into offshore clays. ANALOGUES Beneath present Arno River, the valley Alessandro Amorosi,1 Giovanni Sarti2 body consists internally of three superposed 1 Dipartimento di Scienze della Terra e Geologico- millennial-scale cycles bounded by flooding Ambientali, Università di Bologna, Via Zamboni 67, surfaces (parasequences). These cycles dis- 40127, Bologna, Italy. alessandro.amorosi@unibo.it play a similar facies architecture, with 2 Dipartimento di Scienze della Terra, Università di sharp-based central/outer estuarine clays Pisa, Via Santa Maria 53, 56126 Pisa, Italy. grading upward into inner-estuary, bay-head sarti@dst.unipi.it delta and coastal-plain deposits. Overall, the three parasequences display an aggradation- Defining age of ancient fluvial deposits is al, rather than retrogradational stacking generally a very difficult task, owing to lack pattern, which is interpreted to reflect the of reliable chronological indicators. In con- complex relation between eustatic sea-level trast, Quaternary stratigraphy, due to a well rise and sediment supply during the post- known climatic and eustatic history com- LGM transgression. Diagnostic changes in bined with radiometric dating, may provide vegetation patterns, driven by opposite cli- a well constrained chronostratigraphic mate conditions, enable documentation of framework. parasequence development as a function of Detailed stratigraphic analysis of middle- climate change. Pollen spectra invariably late Quaternary fluvial deposits from the Po show expansions of broad-leaved forests at River Basin, in Northern Italy, reveals dis- parasequence boundaries, suggesting that tinctive cyclic changes in lithofacies and rapid shifts to warmer climate conditions channel stacking patterns, falling in the Mi- accompanied episodes of sea-level rise. In lankovitch (100 kyr) band . Stratigraphic contrast, stillstand phases saw the develop- correlations with the coeval nearshore suc- ment of cold-temperate communities, sug- cessions document that the lower portions of gesting transition to temporary colder cli- fluvial cycles, characterized by isolated sand mate conditions. bodies, were deposited during phases of rel- Stratigraphic architecture beneath the atively high-accommodation (episodes of Lateglacial-Holocene valley bodies shows sea-level rise under interglacial conditions). that the coastal system of Tuscany experi- In contrast, accumulation of laterally amal- enced multiple cycles of fluvial incision and gamated fluvial bodies (channel belts) took subsequent valley filling in response to late place during phases of relatively low accom- Quaternary sea-level fluctuations. Below the modation, marking the “regressive” maxima LGM fluvial deposits, an older set of estua- (i.e., OIS 2 and OIS 6). A well constrained rine clays is observed at depths ranging from chronostratigraphic framework indicates 40 to 90 m. Based upon physical correla- that eight major channel belts (aquifer sys- tions with nearshore deposits, these valley tems), separated by thick mud-prone flood- fills are likely to record an older phase of plain successions, were deposited during the generalized fluvial incision, which is tenta- last 870 ka, while development of the young- tively assigned to the MIS 6-5 transition. est (LGM) channel-belt took place during an interval of time of about 20 ka. Comparison of the late Quaternary suc- cession of the Po Basin with the fluvial ana- logue Escanilla Formation, an Eocene forma- tion commonly applied for reservoir studies, 16 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 documents striking analogies in terms of (Catamarca Province, Northwest of Argenti- both tectonic setting and fluvial architecture. na). Aerial photographs (from 1969), satel- These include: i) sedimentation in a highly lite images (from 1996 to 2004) and theodo- subsiding, actively folded basin; ii) overall lite and gps mappings (from 2006 to 2008) thickness of about 800 m; iii) similar cyclic form the database use to compare seasonal architecture (100 m-thick cycles), with de- river stages. velopment of 6-8 laterally extensive channel Rivers are coming from the boundary be- belts. tween Puna and Pampean Ranges, flow to- Whilst new data are increasingly capable wards south along tectonic valleys and join of providing a refined stratigraphic frame- near the San Fernando Village. The climate work for the Escanilla Formation, no direct is semi-arid with summer torrential rains, dating is available, and duration of its depo- noticeable thermal amplitude and poor veg- sition (1.5 or 7 Ma?) is still problematic. etal cover. These characteristics determine Based upon similarities with modern channel important changes in dynamics and hydrau- belts, we suggest that most of the Escanilla lics of both rivers, e.g.: variations in the Formation (i.e., the 550 m-thick Olson Mem- channel belt width (banks erosion), bar mi- ber) is likely to span less than 1 My, and grations (lateral and downstream move- that the unconformities with both underlying ments) and changes in their patterns after Mondot Member and overlying Collegats the confluence zone. Formation could account for major strati- In particular, the Corral Quemado River graphic hiatuses. This interpretation is con- is an ephemeral stream, torrential regime, sistent with the remarkable homogeneity in and the grain size is predominantly sandy terms of both lithology and facies architec- (very fine to medium sand, with little contri- ture observed across the Olson member, bution of gravel and pebbles); whereas the along with lack of highly mature palaeosols Hualfín River is semi–permanent stream and throughout the formation. the grain size is dominantly coarse (pebbles and cobbles). The maps overlapping define erosion and FLUVIAL EVOLUTION AND SEQUENCE MAPS deposition areas, changes in the channel belt OF INTRAMOUNTAIN BRAIDED RIVERS, width, bar migrations and results of the man CATAMARCA PROVINCE, ARGENTINA management as intent to avoid floods. 3D Karina B. Anis,1, 2 Gustavo E. Rizo,1, 2 Lucía M. maps of the study area were performed by Ibañez,1, 2 Sergio M. Georgieff2, 3 using field measurements, which allow visu- 1 Fundación Miguel L i l lo, Miguel L i l lo 205, alizing better the morphologic changes. T4000JFE, San Miguel de Tucumán, Tucumán, Therefore, some results are: a) the relief and Argentina. the climatic variability of the region deter- 2 IESGLO – UNT, Miguel Lillo 205, T4000JFE – San mine that both rivers and their confluence Miguel de Tucumán, Argentina. present a high rate of erosion and therefore 3 Consejo Nacional de Investigaciones Científicas y a continuous internal morphologic variation; Técnicas, CONICET. b) the greater rate of erosion corresponds to the Hualfín River and would indicate a low The systematic study of sedimentary pro- potential of preservation of its deposits in cesses in the present day rivers allows identi- comparison to the Corral Quemado River. fying the influence of the individual con- The preservation rate is even smaller down- trols, allocyclic and/or autocyclic, in the flu- stream of the confluence zone. vial evolution of intramountain braided riv- ers (Moyano et al. 2005, Grignola et al. 2006, Georgieff, 2006). A series of thematic maps were recorded for the Hualfín and Corral Quemado Rivers Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 17 quén Group as a succession of red layers en- UPPER CRETACEOUS - SEDIMENTARY tirely continental formed during a period of PALEOENVIRONMENTS IN THE total disconnection with the Pacific Ocean. NORTHEASTERN MARGIN OF THE This work allows establishing the Neuquén NEUQUINA BASIN – THE ANACLETO Group is characterized by typical deposits of FORMATION AND THE LOWER MEMBER marine littoral environments. The contact OF THE ALLEN FORMATION. ARGENTINA between the Neuquén and Malargüe Groups Paula Armas,1 María Lidia Sánchez,2 Estefanía was interpreted as the beginning of the Asurmendi2 Maastrichtian Atlantic ingression. 1 CONICET - Departamento de Geología, UNRC - Based on the detailed study and correla- parmas@exa.unrc.edu.ar tion of the outcrops at regional scale, this 2 Departamento de Geología, UNRC-Ruta 8 Km 603 work shows that the Anacleto Formation has (5800) Río Cuarto- msánchez@exa.unrc.edu.ar the first evidences of the Atlantic ingression. Thus, the concepts at regional level of the A detailed sedimentary analysis of Upper extension and influence of the eustacy during Cretaceous deposits, especially those that the late Cretaceous in the ambit of the Neu- correspond to the Anacleto Formation and to quina Basin are modified. One of the main the lower member of the Allen Formation, aspects that must now be established is the was carried out in the northeastern margin age of the Neuquén Group top or redefining of the Neuquina Basin (Neuquén and Río the age of the Atlantic ingression. Negro Provinces). The study area is located in the boundary sector between the provinc- es of Neuquén and Río Negro and the out- TECTONIC GEOMORPHOLOGY OF crops are located at the north of the Neu- RAMHORMOZ WATERSHED AREA IN THE quén City (Neuquén Province), along the ZAGROS FOLD BELT OF SOUTHWESTERN Route 234 and in the proximity of Cinco Sal- IRAN tos (Río Negro Province) on the left margin Arash Barjasteh of the Neuquén River. Head of Geology group, Khuzestan Water & Power The definition of lithofacies and architec- Authority (KWPA), Ahvaz, IRAN. tural elements allowed the interpretation of P.O. Box 61335-137, barjasteh@hotmail.com sedimentary paleoenvironments and the real- ization of a depositional model. Ramhormoz watershed is part of the Za- Using information obtained from the fa- gros Fold Belt in Khuzestan Province of cies association, the following fluvial archi- southwestern Iran. It includes three main riv- tectural elements were determined: channel, ers namely Rud Zard, Rud Talkh and A’la riv- lateral accretion, downstream accretion ers which combine together to form Ramhor- macroforms, crevasse (channel and splay moz River which in turn joins with Jarahi deposits) and floodplain. Elements influ- River which enters the Persian Gulf south- enced by tides were also defined: tidally in- ward. The geomorphology of the catchment fluenced fluvial channel, tidal channels, area as part of the Zagros Simple Fold Belt levee, supratidal flats, intertidal flats, sub- is highly influenced by the local and region- tidal flats and tidal bars. The paleoenviron- al tectonic of the area. Tectonic and structur- mental reconstruction for the Anacleto For- al controls on the Ramhormoz watershed are mation consists of a fluvial system with the main targets of this study due to the braided, anastomosing and high sinuosity build of three dams in next future. The tec- channels; besides of both upper and middle tonic setting is characterized by large thrust estuary system. Meanwhile a lower estuary faults and the occurrence of several land- system or estuary mouth is characteristic of slides, which involve deformable and low the lower member of the Allen Formation. competent sediments (especially marl, silt Previous works have defined to the Neu- and evaporitic deposits). The most rivers are 18 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 tranverse-type which can be geomorphologi- stratigraphy. The existence of upstream allo- cally classified as antecedent drainage. In genic controls (tectonic and climate – Catu- some parts, the rivers run parallel to the neanu 2006) and others associated with the strike of anticlines being locally coincident dynamics of the own system (autogenic) give with fault traces. The river courses through a very complex scenario in which is not al- the mountainous part of the studied area are ways easy to recognize the prevalence of generally SE-NW (Zagros trend) whereas they one above the other. change to NE-SW or N-S (Arabian trend) in The existence in the continental rock the plain part. The location of the landslides record of different frequency cycles with high is related to the fault junctions. Thrusting of and low accomodation or humid and dry conformable over more competent ones fa- conditions alternated are very common. cilitated sliding in the area. This study Therefore we can predict that the exter- shows the importance to analyze the tectonic nal controls (allocyclic) are systematically geomorphology in order to improve the fu- present in continental deposition. ture watershed management projects related In the Neuquén basin the fluvial – eolian to geotechniques of the future dam reser- Tordillo Fm. is a very good example of the voirs. The results also show that lithological presence of different hierarchic cycles where diversity and complexity of the geological the predominance of humid (fluvial – humid structures have key roles on the geomorphol- eolian intervals) or dry conditions (dry eo- ogy of the area. lian systems) is of paramount importance in the reservoir behavior of the rocks and the References prediction of hydrocarbon productivity. The change in the correlation philosophy Barjasteh, A., 2003. Morphotectonics of Allah from a lithostratigraphic to a chronostrati- River and its application in the rehabilitation graphic style have produced a very deep im- study of Ramhormoz region, southwest of pact in the comprehension and predictability Iran. Proc., 6th. Int Conf. River Engineering, Ahvaz University, Ahvaz, Iran, 6p. of the local to regional distribution of pro- Barjasteh, A., 2006. Investigation of the engi- duction zones in the most important reser- neering geomorphologic properties of Allah voir interval of the Basin. River, nor theast of Ramhormoz city ( in Persian). Proc.,10th Symp.Geol.Soc.Iran, References Tarbiat Modarres University, Tehran, Iran, p.2368-2373 Barjasteh, A., 2007. Investigation of the rela- Catuneanu, O. (2006) Principles of Sequence tionship of drainage network to fracture Stratigraphy. Ed. Elsevier. system in Gachsaran Formation (Ramhormoz region) (in Persian), Proc.,1st Applied Geol- ogy Congress of Iran. Azad Islamic University THE PROCESSES AND DEPOSITIONAL of Mashad, Mashad, Iran, pp.868-872. ARCHITECTURE OF BIG RIVERS: THE RIO PARANÁ, ARGENTINA Ashworth, P. J.,1 Amsler, M. L.,2 Best, J. L.,3 HIGH FREQUENCE CICLICITY IN Hardy, R. J.,4 Lane, S. N.,4 Nicholas, A. P.,5 Orfeo, CONTINENTAL SYSTEMS: EXAMPLE OF O.,6 Parsons, D. R. ,7 Reesink, A. J. H. ,1, 8 FM. TORDILLO, UPPER JURASSIC Sambrook Smith, G. H.,8 Sandbach, S. D.,4, 5 NEUQUÉN BASIN ARGENTINA Szupiany, R. N.2 Arregui Carlos Daniel 1 School of Environment and Technology, University of J.J. Lastra 6000, Neuquén (8300). Brighton, UK, email: p.ashworth@brighton.ac.uk carlos.arregui@petrobras.com 2 Universidad Nacional del Litoral, Facultad de Inge- niería y Ciencias Hídricas, Centro Internacional de The genesis of the cyclicity in continental Estudios de Grandes Ríos, C.C. 217 - (3000) sediments without connection with the sea Santa Fe, Argentina. has been intensively studied in modern Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 19 3 Departments of Geology and Geography and Ven migration of low-relief bedforms with di- Te Chow Hydrosystems Laboratory, University of Illi- mensions similar to unit bars observed in the nois, Urbana-Champaign, IL, USA. field (height ~3-5 m, wavelength 1-2 km). 4 Department of Geography, University of Durham, Field-model data suggest a need to: (i) un- Durham, UK. derstand the contribution of unit bars to big 5 Department of Geography, University of Exeter, Exe- river sedimentology, and (ii) establish why ter, UK. the majority of the Paraná channel-belt is 6 Centro de Ecologia Aplicada del Litoral, Consejo stable over decadal time scales. Nacional de Investigaciones Cientificas y Tecnicas, Corrientes, Argentina 7 School of Earth and Environment, University of FACIES CHARACTERISTICS AND ORIGIN Leeds, Leeds, UK. OF THE QUATERNARY SEDIMENTS IN THE 8 School of Geography, Earth and Environmental NILE VALLEY, EGYPT Sciences, University of Birmingham, UK. Awad, M.H. Dept. of Geology, Dean Faculty of Science, Al-Azhar Little is known about the processes, dy- Univ., Cairo, Egypt. namics and deposits of the world’s largest multi-thread rivers and whether they are dif- The lithostratigraphic studies of the ex- ferent from smaller (less than 1 km wide) posed Quaternary sequence at Idfu, Qena rivers. This paper reports on a combined and Beni Suef in the Nile valley of Egypt al- field and numerical modelling campaign on lowed to differentiate it into six rock units the sandy Rio Paraná, Argentina – the namely, Idfu, Armant, Abbassia, Makhadma world’s 6th largest river. and Warsha Formations. Bathymetric and 3D flow data were taken Representative samples were subjected in a 38 km long, 4 km wide reach using sin- for size analysis, heavy mineral separations gle-beam echo sounders, acoustic Doppler and petrographic investigations. current profilers and dGPS. Results demon- The studied Quaternary sediments reflect strate that the main channels of the Paraná aqueous sedimentation processes. The gravel at low flow are dominated by dunes up to of Idfu Formation are mainly rounded to 3.5 m high and less common unit bars 2-5 m well rounded reflecting long way run derived high with some up to 10 m high. The depos- from different basement rock types of the its of eight km-scale mid-channel bars were Eastern Desert mixed with short way run characterised by 43 km of Ground 4~Pene- sediments of Nile load origin. trating Radar (GPR) with penetration down The gravel of Armant, Makhadma and to 10 m, and 28, m-deep suction cores. The Issawia Formations are angular to subangu- internal structure of mid-channel bars is dom- lar indicating short way run derived from the inated by (i) decimetre to sub-m high, surrounded and nearby sedimentary sequenc- stacked dune sets, (ii) up to 7 m thick, high- es. The Warsha gravels which are mainly angle, bar margin sets, and (iii) decimetre- angular to subangular and rounded to sub- thick ripple sets, most commonly, but not rounded pebbles and granules of sedimenta- exclusively found at the bartop. Re-activa- ry and fewly volcanic origin indicate deriva- tion surfaces on bar margins are common. tion from nearby Eocene and volcanic rocks Between 2-7 stacked unit bars make up a of the Eastern Desert. mid-channel bar. Zircon, epidote, staurolite, kyanite, gar- Numerical modelling of flow, sediment net, rutile and tourmaline are the main transport and morphological change in the heavy minerals detected in the sands of Idfu 38 km study reach show a good match be- and Armant Formations with varying degrees tween field and model flow distributions. of abundance. Simulated channel change is characterised The combination of sedimentological by talweg shifting and the formation and characteristics of the studied Quaternary sed- 20 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 iments indicate that during the Quaternary commodation space- and calcic paleosoils – (Pleistocene) torrential activities in the East- less accommodation space. ern Desert together with Nile flooding led to It’s worth saying that channels in this the deposition of the studied rock units. lower section are amalgamated vertically with channels developed in the upper sec- tions, constituting multistorey channels. Be- HIGH-FREQUENCY VARIATIONS IN cause of this, some areas are dominated by ACCOMMODATION SPACE IN PUNTA SAN tabular geometries of floodplain deposits ANDRÉS ALLOFORMATION (PLIO- and others by channelized geometries which PLEISTOCENE), BUENOS AIRES PROVINCE, reflect areas that remained preferentially in- ARGENTINA cised during Plio-Pleistocene times. Elisa Beilinson The middle section is characterized by Centro de Investigaciones Geológicas – 1 #644, La coarser floodplain deposits and is much Plata (B1900TAC), Argentina. more dissected by channels, which have mul- beilinson@cig.museo.unlp.edu.ar tiepisodic filling and a complex geometry. This section is interpreted as a floodplain The continental deposits of the Punta San proximal to the heads. Paleosoils in this sec- Andrés Alloformation (Plio-Pleistocene) tion are represented by hydromophic hori- crop-out in the marine cliffs of south-eastern zons with little participation of calcic facies. Buenos Aires Province (Mar del Plata City, Accommodation during this period is inter- Argentina). Deposits of this unit have been preted to have been positive but reduced assigned to different sub-environments such when compared to the lower section. as floodplains, fluvial channels and tempo- The upper section is characterized by de- rary water bodies according to their facies posits of mobile, high-sinuosity channels. association and geometry (tabular, wedge- Floodplain deposits are barely represented shaped or lenticular). Their lateral and ver- and highly dissected. Development of fluvial tical arrangement allows to identify three channels is related to periods of diminishing different sections, each of which represents a accommodation space, probably due to a different sedimentary sub-environment and drop in local base level and/or an increase different accommodational conditions. in precipitations. Filling of the channels in- The first and lower section is character- dicates a subsequent raise in local base level ized by floodplain deposits (crevasse-splay and re-establishment of positive accommoda- deposits and paleosoils). The few channel tion space. bodies found in this lower section have a To summarize, the geometric and facial simple geometry, with width/length ratio < analysis of Punta San Andrés Alloformation 10 in all cases and monoepisodic filling. deposits allowed to identify depositional en- This lower section is considered to represent vironments which vertical and lateral distri- an area distal form the heads, where pale- bution show a progressive change in accom- otopography, fluctuating climate and drain- modation and plaeoclimatic conditions. Dry age design lead to the development of exten- and arid periods related to little accommo- sive floodplains cut by episodic, short-lived dation space alternate with wetter periods straight or low sinuosity channels associated related to higher accommodation space and to food events or storms. Regarding the pa- finally to a more important drop in local leosoils, a cyclic alternation was found be- base level leading to general fluvial incision tween calcic paleosoils and hydromorfic pa- and negative accommodation space. leosoils which was interpreted as cyclicity between dry and humid climates. Accommo- dation during this period was positive, but high-frequency fluctuations were defined be- tween hydromorphic paleosoils – higher ac- Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 21 between the two rivers (Bermejo: Paraguay) ON THE INFLUENCE OF DENSITY was 0.17 (combined discharge ~ 2800 m3s- DIFFERENCES BETWEEN MIXING FLOWS 1) and 0.23 (combined discharge ~ 5050 AT RIVER CONFLUENCES m3s-1) respectively. However, in 2007 the Best, J. L.,1 Parsons, D. R.,2 Amsler, M. L.,3 density excess of the Río Bermejo over the Kostaschuk, R. A.,4 Lane, S.N.,5 Orfeo, O.,6 Río Paraguay was 5.1 kg m-3, whilst in the Szupiany, R.N.,3 Hardy, R.J.5 study period in 2005 it was 2.2 kg m-3. Flu- 1 Departments of Geology and Geography and Ven id mixing at this site is dominated by a den- Te Chow Hydrosystems Laboratory, University of Illi- sity underflow from the Río Bermejo that nois, Urbana, IL 61820, USA penetrates underneath the fluid of the Río 2 University of Leeds, UK; d.parsons@see.leeds. Paraguay and then upwells at the outer bank ac.uk of the Río Paraguay downstream from the 3 Universidad Nacional del Litoral, Facultad de Inge- confluence. Mixing occurs through instabili- niería y Ciencias Hídricas, Centro Internacional de ties along the shear layer between the two Estudios de Grandes Ríos, C.C. 217 - (3000) flows, fluid instabilities along the top of the Santa Fe, Argentina. underflow current, topographic forcing over 4 University of Guelph. bedforms and interactions with the channel 5 Durham University, UK. banks. This paper will illustrate these mech- 6 CECOAL, CONICET, Arg. anisms of mixing and the possible signifi- cance of density contrasts between confluent Channel confluences form key nodes flows in determining the morphodynamics at within all alluvial networks and extensive such channel junctions. research over the past 25 years has shown how the dynamics of mixing at these sites, and nature of the bed morphology, are con- VISUALIZATION OF DUNE AND BAR- trolled by the junction angle, the momentum GENERATED TURBULENCE AND SEDIMENT ratio between the two confluent flows, the SUSPENSION: IMAGES FROM THE SOUTH junction planform shape and the nature of SASKATCHEWAN RIVER, CANADA, AND any bed height discordance between the two IMPLICATIONS FOR SUSPENDED channels. Although remote sensing of many SEDIMENT RATING CURVES open channel confluences, particularly of Jim L. Best, R.E. Thomas, P.J. Ashworth, S.N. larger rivers, often reveals a difference in Lane, I.A. Lunt, G.H. Sambrook Smith, C.J. Simpson turbidity between the two flows, there has Departments of Geology and Geography and Ven Te been little work conducted on how the densi- Chow Hydrosystems Laboratory, University of Illinois, ty differences that such turbidity contrasts Urbana, IL 61820, USA. may generate may influence the dynamics of mixing at confluences. It has long been known that form rough- This paper presents results from a field ness, such as dunes and bars, can generate study of flow and bed morphology at the large-scale turbulence that can dominate the confluence of the Río Bermejo and Río Para- temporary suspension of sediment within guay, Argentina, where the sediment load, many rivers. Several studies have linked such and thus bulk density, of the Río Bermejo large-scale turbulence to high instantaneous flow is always greater than that of the Río sediment fluxes, and shown how the fluid Paraguay. The Río Bermejo is an important upwellings produced by form roughness river in the Paraná basin as, although it may may dominate the flow structure of many only contribute ~5% of the fluid discharge channels, especially those with high to the Río Paraná, it may contribute up to width:depth ratios. Such upwellings are ~80% of the total wash load. Surveys of the commonly seen as ‘boils’ on the surface of confluence were undertaken in May 2005 many rivers and range from decimetres to and April 2007, when the discharge ratio metres in diameter. 22 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 This paper presents images of form- that of the Holocene. On a global scale, it is roughness generated macroturbulence that well known that channel gradients correlate were recorded from low-level aerial photo- inversely to drainage basin areas: similarly, grammetric surveys that were flown over the shelf gradients and width correlate to on- sand-bedded South Saskatchewan River, shore fluvial gradients and drainage areas, Canada. The South Saskatchewan River was such that >50% of the variance in shelf dammed upstream of the study reach in width for the midlatitudes and tropics is ex- 1964 and hence is now relatively clear, en- plained by contributing drainage basin area abling suspended sediment fluxes to be visu- alone. alized within the water column at most stag- In an icehouse world, high-frequency cli- es. We will present images, taken at a range mate changes are coupled to changes in ice of flow stages, which show the form of such volume, and unsteadiness of sediment supply upwellings associated with sand dunes and due to climate change is modulated by the with the fronts of unit and compound bars. transit of river mouths across the shelf. Dunes are seen to provide periodic point- Moreover, transit of river mouths across a source ejections of sediment that erupt on the broad shelf results in the merger of drainage flow surface, and are manifested as a trail basins that, in a highstand world, discharge of circular/ovoid upwellings on the water separately to the coastal oceans: merging of surface. Sediment suspension over bar fronts drainage basins increases individual point- occurs over a greater width and appears to source sediment supply, but there will be few- generate a more continuous source of par- er river mouths and delta systems at the shelf tially-suspended sediment. The suspended margin than there are during highstand sediment rating curve for the river now time. These relationships must be different in shows an increase in its slope at 330-403 a Greenhouse world because the high fre- m3s-1, and it is suggested this break corre- quency, long distance transit of river sponds to the increased influence of form mouths, and merger of drainage basins roughness in generating sediment suspen- should not occur to the same degree. In an sion. Icehouse world, major high-frequency chang- es in fluvial-deltaic, shelf-margin, slope, and basin-floor stratal packages will reflect fluvi- CONTINENTAL SHELVES AS THE al responses to sea-level change. By contrast, LOWSTAND FLUVIAL LONGITUDINAL in a Greenhouse world, high-frequency PROFILE stratigraphic packaging should be closely Mike Blum coupled to unsteadiness in sediment supply ExxonMobi l Upstream Research Company. due to climate change, rather than modulat- mike.blum@exxonmobil.com ed by fluvial transit of the shelf, and merging of drainages. Lowstand fluvial profiles represent the first-order morphodynamic state for conti- nental shelves, and river long profiles are ROLE OF INCISED-VALLEY SYSTEMS IN fundamentally graded to shelf margins. Over SOURCE-TO-SINK SEDIMENT ROUTING the last 10^6 yrs mean sea level has been - AND STORAGE: EXAMPLES FROM THE 60 to 65 m, with a mode at -85 to -90: for LATE QUATERNARY NORTHERN GULF OF most of this time, the majority of shelves MEXICO MARGIN would have been subaerial. Long profiles for Mike Blum, Matt Garvin river systems have equilibrium times >10^4 ExxonMobil Upstream Research Company. to 10^5 yrs: they should be adjusted to mike.blum@exxonmobil.com mean conditions over time scales that are = equilibrium times, and insensitive to the Incised-valley systems form in response anomalous and infrequent highstands like to sea-level fall, as fluvial systems extend Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 23 across newly subaerial shelves to the low- gins with broad shelves, like those of the stand shoreline and shelf margin. Recent Late Quaternary Gulf of Mexico, drainage work on Late Quaternary systems of the Gulf basins merge as channels extend across the of Mexico passive margin illustrate how sed- shelf, which in turn increases drainage areas iment supply might change over the course that contribute to single point sources at the of a glacio-eustatic cycle, and how the evo- shelf margin. Apparent signals of increased lution of incised-valley systems modulates or decreased flux of sediment to the shelf source-to-sink sediment routing to deepwater margin and beyond may reflect geomorphic environments. response to sea-level change - the merging of First, empirical data that links sediment drainages as they transit the shelf - rather supply to climate suggests supply from the than changes in supply from the hinterland. hinterlands should decrease during glacio- eustatic sea-level fall and lowstand due to temperature depression. Hence, supply from LAS CUMBRES FORMATION (EARLY the hinterland may be (a) at a maximum PLEISTOCENE), AN EXAMPLE OF THE when river mouths reside in highstand posi- OROGENY CLIMAX TECTOFACIES IN THE tions, and sediment storage takes place on PAMPEAN RANGES the coastal plain and inner shelf, and (b) at Gerardo E. Bossi,1 Sergio M. Georgieff,1, 2 Lucía a minimum when river systems are extended M. Ibañez1, 3 to the shelf margin lowstand shoreline and 1 IESGLO – UNT, Miguel Lillo 205, T4000JFE – San directly feeding the slope and basin floor. Miguel de Tucumán, Argentina. Second, studies of late Quaternary sys- 2 CONICET. tems, where deposits can be mapped and dat- 3 Fundación Miguel Lillo, Miguel Lillo 251, T4000JFE ed independent of sea-level change, make it – San Miguel de Tucumán, Tucumán, Argentina. clear that incised valleys form in a step-wise gbossi@arnet.com.ar manner in response to sea-level fall and low- stand, with short periods of incision punctuat- Las Cumbres Formation is an Early Pleis- ed by extended periods of lateral channel mi- tocene coarsening-upward succession com- gration, valley widening, and deposition of posed mainly by conglomerates laying over channel-belt sands. Step-wise incision and the Salicas (Pliocene) sandstones. The top of lateral channel migration is the process that the unit is the original geomorphic deposition- creates the basal valley-fill surface, as well as al surface. In some places like, in Villa Mer- controls the overall dimensions of the incised vil, the unit lays disconformably over the Sal- valley. The timing of incision and channel- icas Formation but in others, like in Alpas- belt deposition on the evolving valley-fill sur- inche, the formational limit is a long transi- face varies between river systems due to a va- tion. At the northeast extreme of the Velasco riety of controls. The total volume of sediment Range, a ring of low hills (named Cumbres de exported during the period of incised-valley Los Pozuelos) shows to the Las Cumbres For- formation is a relatively small value com- mation as a complex system of allounits sep- pared to the ongoing flux from the hinter- arated by angular unconformities, which are lands, and short periods of incision likely pro- related to Uscamayo Fault, an active synsedi- duce an insignificant amount. However, peri- mentary fault in Pleistocen times. ods of lateral channel migration and valley Las Cumbres Formation is one of the typ- widening significantly increase the export of ical conglomerate units developed as very sediment, perhaps by 25% over background extensive alluvial bahada coming down rates, such that periods of fluvial deposition from the emerging ranges during the climax during sea-level fall and lowstand corre- of the tectonic inversion of the area. The sponds to increased sediment delivery to the conglomerates entered deep into the “Bolson shelf margin. de Pipanaco”, the biggest intramountain ba- Finally, for low-gradient continental mar- sin of the Pampean Ranges. The sedimentary 24 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 succession shows an alternation of lenticular ed shales. Conglomerates are scarce and bodies of either massive or graded coarse concentrated near the base of the succession. conglomerates and ill-laminated better sort- Isolated small and rounded pebbles occur in ed fine conglomerates. The coarser facies the channel facies. The clasts are mainly form tabular bodies with occasional over- from granite and low grade metamorphic sized blocks and were interpreted as debris rocks, with minor proportion of volcanic flows while the better sorted facies were as- rocks and tuff paraclasts. Associated with signed to water laid deposits related to the water laid facies there are also very thick ephemeral channels and chutes forming a horizons of crossbedded sandstones, laying distributary system. Texture, angularity and over a flat erosive surface. Fine grain fall composition of the pebbles indicate a com- lamination alternates with grain flow thick- bined provenance from the Velasco (South), er lamina indicates an eolian origin. Vinquis and Zapata (North) and Paimán Most indirect age evidence located the sed- (West) Ranges, according to the measured imentation time in the Paleogene, in a time paleocurrents. Paleocurrent and maximum previous to the developping of the near basin pebble size maps composition indicate dis- eastern volcanic arc of the Puna. In the Hua- placements of the compositional facies from lfín Range and in the Campo del Arenal, the the location of their source areas, which sedimentation of the unit was controlled by a could be related to the activity of a regional normal synsedimentary fault system oriented left transcurrent fault (known as Lineamien- NE-SW, that imposed local variation of the to Tucumán), and moved the whole sedi- thickness of the unit (between 50 to 200 m). mentary system during the deposition of the Dominant facies indicates sheetflood sed- conglomerates. imentation in a very extensive plain near sea level, under an arid climate with distant and low relief source areas, strongly oxidizing. THE RED BEDS OF HUALFÍN FORMATION Channel deposits are thin lenticular units IN THE SYNRIFT STAGE OF PAMPEAN composed of trough cross - bedding sand- RANGES, NORTHWEST OF ARGENTINA: stone with minor indication of channel and PALEOGEOGRAPHIC AND bar developpings. The eolian horizons are ENVIRONMENTAL IMPLICATIONS located in the upper part of the unit when Gerardo E. Bossi,2 Sebastián Moyano1, 2 these sandy units reached the maximum de- gbossi@arnet.com.ar velopment The normally ephemeral and dry 1 IESGLO – UNT, Miguel Lillo 205, T4000JFE – San fluvial system was an excellent repository Miguel de Tucumán, Argentina. for the dune fields formed by better sorted 2 Consejo Nacional de Investigaciones Científicas y sandstones. Técnicas, CONICET. Another unit of similar age with exten- sive dune fields interstratified with the same Hualfín Formation represents the early fluvial facies is known as Quebrada de los infill of the Santa María – Hualfín Basin in Colorados Formation, outcropping about the Northwestern Pampean Ranges of Argen- 300 km to the north of the study area, in the tina. The unit is composed of well indurated Calchaquí Valley. In some places where the dark red sandstones alternating with minor unit is absent, as in El Cajón Valley, the sur- shale’s, laying over the Pampean Peneplain. face of the Pampean Peneplain is full of im- Facies associations are dominated by massive pact marks generated by wind erosion. to parallel laminated medium to fine The low land paleogeography of the area grained sandstones forming tabular lateral during Paleogene times associated with the extensive beds (80%), irregularly cut by len- convergence of the Hadley-Ferrel atmospher- ticular medium sandstones with trough cross ic cells is a well fitted scenario for the highly bedding (15%), assumed to be shallow oxidized arid fluvial facies alternating with channel facies and thin tabular fine laminat- eolian field. Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 25 19) were analyzed to detect changes in veg- NATURAL AND ANTHROPICAL FACTORS etative cover, specifically deforestation, and AFFECTING MODERN RIVERS AND changes from natural vegetative cover to RESERVOIRS IN A SEMIARID BASIN. agricultural lands, for the last 30 years. TAPIA - TRANCAS BASIN, TUCUMÁN, LandSat images were analyzed to record also ARGENTINA changes in the delta of Sali River at the res- Bustos, María Soledad ervoir. Consejo Nacional de Investigaciones Científicas y Expansion of agricultural lands was ob- Técnicas, CONICET. Fundación Miguel Lillo, Miguel Lillo served mainly in lowland areas along the 205, T4000JFE, San Miguel de Tucumán, Tucumán, Sali river Valley and in the east region of the Argentina. solbustos81@gmail.com basin (piedmont areas of the Sierras de Me- dina). Changes in river morphology at the Present day rivers are certainly affected by delta, sediment deposits and stabilization of human activity and natural factors. In the same deposits with vegetation were observed com- way, the dam construction increases the impact paring Landsat 5 TM for different dates. on the modern rivers. Among others anthropi- Changes observed could be related to both, cal factors, mainly agriculture and deforesta- natural and anthropical factors. First, tion, the amount of runoff and sediment trans- change in base level due to the presence of ported to rivers and deposited in reservoirs are the reservoir and the adaptation of the fluvi- increasing during the last decades. al system to the new base level, also in- Celestino Gelsi reservoir is the biggest creased rainfall amount an its consequent reservoir in the Tucumán Province, Argenti- raise in sediment yield. In second place mis- na. Since 1966, sediment deposition and loss management practices related to land use of impoundment capacity were documented could have affected the balance of sediment and referred as consequences of mismanage- leaving the basin area. ment practices, on agricultural lands and, deforestation in the Tapia – Trancas up- stream area (Adler, 2004). PALEOFLUVIAL SYSTEMS IN THE RUSLE model, (Renard et al., 1997), was WESTERN CHACO PLAIN, TUCUMÁN applied to quantify soil loss for the basin PROVINCE, ARGENTINA area. R-factor was calculated, according to Collantes, M.M.,1 Sayago, J.M.,1, 2 Busnelli, J.1, 2 Renard and Freimund (1994), two periods 1 Geosciences and Environment Institute, National were considered: 1) from 1935 to 1962 and, University of Tucumán, Miguel Lillo 205, (4000) 2) from 1963 to 1990. The values of R fac- Tucuman (Argentina); mcollantes@arnet.com.ar tor, obtained were greater in the period 2 National Council of Scientific and Technical Resear- 1963-1990 than in the period of 1935-1962, ch (CONICET). probably related to an increase in mean an- nual and monthly rainfall in the source area The aims of the work was study de evolu- during the second period. Same trend in tion of the western fluvio-eolian plain in the rainfall amount was reported by Minetti and Tucumán Province. The analysis of the pale- Gonzales (2006) for other areas in NW re- ofluvial features of the study area, using gion of Argentina and Piovano et al. (2002) photointerpretation and field observations, for central area of Argentina. Also increased allowed mapping and classifying the geo- amounts of discharge entering the Reservoir forms created by past river dynamics. Pale- were registred for the period 1967 to 1996, ochannels with structural control, migrating according to the database from Hydrologic paleochannels and paleochannels turned into Resources Department (Dirección de Recur- ravines by human-induced erosion were sos Hidricos of Tucumán). characterized according to their morphology Satellite images (Landsat 5 TM and/or genesis. from1988/08/15, 1997/08/24 and 2007/07/ The paleochannels with structural control, 26 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 are elongated flat-bottom valleys run down to the plain as shallow, sometimes buried. The THE RIERA DE SOBIRANS (NE, SPAIN) morphology of the paleoforms suggests that MODEL OF OVERELEVATED TORRENTIAL they were developed by NW-SE running CHANNELS: SEDIMENTARY streams with moderate energy and high com- CHARACTERISTICS petence. Although they are presently inactive, Ferran Colombo,1 Oriol Riba,1 Lluis Rivero2 subsurface or even surface runoff during heavy 1 Dept. Estratigrafia, Paleontología y Geociencias rain periods might occur. River behavior Marinas. Fac. Geología. Universidad de Barcelona, seems to be related to paleofluvial conditions, C/ Martí-i-Franquès s/n, E-08028, Barcelona, together with fault and fracture control. España. colombo@ub.edu The migrating paleochannels are frequent 2 Dept. Geoquímica, Petrología y Prospección Geoló- throughout the fluvio-eolian plain, occurring gica. Fac. Geología. Universidad de Barcelona, C/ as shallow channeled depressions generally Martí-i-Franquès s/n, E-08028, Barcelona, España. masked by crops or artificial drenaige. Such channels can be attributed to relatively re- In the Quaternary of the Maresme there cent overflows from the Tajamar river. They are a number of natural overelevated served as local collectors of excess water straight streams of torrent channels located during heavy rain periods, when the region at a level higher than the surrounding flood- was still covered by Chaco forest. Nowadays, plains. These overelevated streams show a they behave as local areas of runoff storage distinct morphology and a channelized con- on soils having high capacity for moisture vex-up sedimentary body where the vertical retention that plays an important role during accretion and the levee growth episodes are drought periods. coeval. These streams are characterized by The fluvial paleovalleys, are located in episodic water discharges that are interrupt- the western sector of the study area, large ed by prolonged dry periods with no superfi- elongated depressions, similar to real fluvial cial water discharge. valleys, start in the fluvio-eolian on the west The ”Riera” type stream corresponds to a and extend southward over several tens of single channel of a sandy braided river. It is kilometers and disappear in the saline de- short with steep gradient from 3.2% to 3.4% pressions of Santiago del Estero province. in the Riera d’Arenys (Sobirans). The source They seem to be related to intensive head- area is made up of granitic rocks that supply retreat erosion during the moist Holocene large amounts of sandy sediments. The periods, with runoff increase from the west, “Ramblas”, located in the Barcelonès and and/or to changes in the eastern base level Maresme areas, are good examples of over- by neotectonic reactivation. In all cases, ra- elevated streams. vine heads are located in the plain, not in The term “Sobirans” is proposed for this the piedmont. This could be related to the new model. existence of an area depressed by tectonics that would have diminished river incision, and/or be caused by decrease in water sup- ESTIMATION OF SUSPENSION SEDIMENT ply from the west due to climatic change. All VOLUME IN TO THE FUTURE DAM OF these channels coincide, in some stretch of POTRERO DE LAS TABLAS ON RIO LULES. their courses, with structural features caus- TUCUMAN PROVINCE. REPUBLICA ing slightly asymmetric margins. Additional- ARGENTINA ly, mass movements might have contributed Anibal Comba, Julian Soto not only to channel widening but also to Faculty of Exact Sciences and Technology. National channel stabilization through creeps and University of Tucumán. Independence Avenue 1800. flows from the hillsides. (4000). San Miguel de Tucumán (0381) 4354502- 155057213. anibalcombaa@yahoo.com.ar Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 27 The application of the methods of USLE, val. The sandstones are interpreted as storm MUSLE, GAVRILOFF and MATHEMATICAL washover deposits. In these sequences we CORRELATION OF LIQUID AND SOLID VOL- have found numerous disarticulated remains UMES is made, to estimate expectable future of fishes (Pycnodontiforms and Siluriforms), volume of suspension sediment in dam of Po- fragments of tetrapods? (Tetrapoda), a tooth trero de las Tablas, on the Lules River in the of crocodile (Crocodylidae), preserved mol- Province of Tucumán, Argentine Republic. lusks (Gastropods and Bivalves) of problem- The necessary parameters for the application atic taxonomy, stromatolites (LLHC, LLHS of the mentioned methods are determined and and dome type). Also was identified a set of the hypotheses of work and the results ob- fossil traces integrated by traces of birds tained with each one are compared. (Avipedidae) and Skolitos ichnofacies , be- The information to use is included in the sides a Domichnia trace on an estromatolitic topics of morphology, hydrometric, hydrom- rock, caused by a perforant bivalve, also eteorology, land use and fluvial hydraulics. preserved. The study of the fossils assem- The results of the comparison are ex- blage, traces, sediments, and sedimentary pressed graphically and in percentage. structures indicates a brackish mixed envi- Conclusions are obtained about the effec- ronment, of low depth and high energy, prob- tiveness of the methods applied in mountain ably estuarine. river basins as the one of the Lules River and the consequences of the sediment deposit in the future dams are analyzed. GRADUAL LATERAL RIVER MIGRATION INDUCED BY LATERAL FLOODPLAIN TILTING; A 3D NUMERICAL SIMULATION AN ESTUARINE FOSSIL ASSEMBLAGE Arjan de Leeuw,1 Quintijn Clevis,2 Greg Tucker,3 FROM THE YACORAITE FORMATION Poppe L. de Boer1 (MAASTRICHTIAN-DANIAN) AND ITS 1 Department of Earth Sciences, P.O. Box 80.021, PALEOENVIRONMENTAL SIGNIFICANCE. 3508 TA Utrecht, The Netherlands. adeleeuw@ JUJUY - NORTHWESTERN ARGENTINE geo.uu.nl, pdeboer@geo.uu.nl Cónsole Gonella, C. A.,1, 2 L.R. Horta,1 P.E. Herrera 2 Shell International Exploration and Production B.V., Oviedo ,1 M. Grif f in,2 S.M. Georgief f,1, 3 F.G. Kessler Park 1, 2288 GS, Rijswijk, The Nether- Aceñolaza1 2 lands Quintijn.Clevis@shell.com 1 Facultad de Ciencias Naturales e IML. Universidad 3 Cooperative Institute for Research in Environmental Nacional de Tucumán. Miguel L i l lo 205, Sciences (CIRES) and Dept. of Geological Sciences, T4000JFE, San Miguel de Tucumán, Argentina. University of Colorado, Boulder, CO 80309-0399, 2 INSUGEO (Instituto Superior de Correlación Geoló- USA gtucker@cires.colorado.edu gica) – CONICET. Miguel Lillo 205 (4000). S.M. de Tucumán, Argentina. Counter-intuitively meandering rivers 3 IESGLO (Instituto de Estratigrafía y Geología Sedi- may migrate laterally upslope (Nanson, mentaria Global). Miguel Lillo 205, T4000JFE, San 1980; Peakall et al., 2000). Using the Chan- Miguel de Tucumán, Argentina. nel Hillslope Integrated Landscape Develop- ment Model (CHILD; Tucker et al, 2001; Cle- We describe a brackish water fossil as- vis et al., 2006) the effects of different tilt- semblage from Yacoraite Formation (Maas- ing rates were analysed. During relatively trichtian – Danian), in the localities of strong tilting (3.10-5 rad/1000 yr) river mi- Maimará and Jueya, Jujuy - Northwest Ar- gration was found to be down-slope, and at gentine. The dominant lithology of the study lower tilting rates (2.10-5 rad/1000 yr) ups- levels is characterized by a calcareous sand- lope migration occurs, while avulsions and stones succession, with ripplestratified struc- crevasses were not considered in the model. ture, fining-upward. Fine to very fine sand- A faster rate of meander expansion on the stone lenses occur in this fossiliferous inter- lower side and the resulting preferential 28 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 meander cut-off was identified as one of the The Prosperança Formation consists of con- mechanisms behind upslope migration (Nan- glomerates, arkosic sandstones and mud- son, 1980). Another potential element in up- stones, which fill graben structures. This slope migration suggested by the numerical unit is overlain unconformably by carbonate simulations is the relatively fast overbank rocks of the Acari Formation (Neoproterozo- accumulation on the lower side floodplain. ic) observed only in cores. These formations This may reverse the slope near the locus of represent the basement of the oil producing the river bed and thus the direction of lateral Paleozoic basins of Amazonia and the pre- migration. cise characterization and paleoenvironmen- tal reconstruction is important for their dis- References tinction from Paleozoic units. The strati- graphic analysis of the Prosperança Forma- Clevis, Q. Tucker, G.E., Lock, G., Lancaster, S.T., Gasparini, N., Desitter, A. & Bras, R.L. tion was carried out along the margin of the (2006) Geoarchaeological Simulation of Negro and Jaú rivers at the northern part of Meandering River Deposits and Settlement State of Amazonas. Three facies associations Distr ibut ions: A Three-Dimensional Ap- were recognized and interpreted as products proach. Geoarchaeology: An International of a fluvial-deltaic system: 1) prodelta/lacus- Journal 21, 843–874. Nanson, G.C. (1980) A regional trend to mean- trine, exhibiting laterally extensive sand- der migration. Journal of Geology 88, 100- stones/mudstones rhythmites and mudstones 108. interbedded with decimeter thick lenses of Peakall, J., Leeder, M.R., Best, J. & Ashworth, climbing ripple cross-laminated sandstones; P. (2000) River response to lateral ground 2) delta front, consisting of fine sandstones tilting: a synthesis and some inplications for the modelling of fluvial architecture in with complex cross-stratification character- extensional basins. Basin Research 12, ized by sigmoidal strata, low angle to pla- 413-424. nar and climbing ripple cross-laminations, Tucker, G.E., Lancaster, S.T., Gasparini, N.M. & locally associated with deformational sedi- Bras, R.L. (2001) The Channel–Hillslope mentary structures; and 3) fluvial braided integrated landscape development model (CHILD). In: W.W. Doe (Ed.) Landscape plain, comprised of medium to coarse sand- Erosion and Sedimentation Modelling, Klu- stones with planar and trough-cross bedding. wer, New York, NY, pp. 349–388. The sigmoidal lobes of the delta front were fed by braided distributaries that migrated mainly to SW, under hyperpycnal flow condi- NEOPROTEROZOIC FLUVIAL-DELTAIC tions. Rhythmites and mudstones distributed DEPOSITS OF THE AMAZON CRATON: THE along several kilometers suggest a wide- PROSPERANÇA FORMATION, STATE OF spread sedimentary basin probably of lacus- AMAZONAS, BRAZIL trine origin. Lenticular medium to coarse Roberto César de Mendonça Barbosa,1 Afonso César sandstones are related to migration of sub- Rodrigues Nogueira,2 Werner Truckenbrodt2 aqueous dunes, associated to fluvial-braided 1 Programa de Pós-graduação em Geologia e Geoquí- processes. The top of the Prosperança For- mica, IG, UFPa, Brasi l . robertocmbarbosa@ mation is marked by an expressive erosional yahoo.com.br surface interpreted as a sequence boundary. 2 Instituto de Geociência, UFPa, Brasil. anogueira@ This interpretation is reinforced by the oc- ufpa.br; trucken@ufpa.br currence of an iron-rich sandy-pelitic mottled to columnar horizon attributed to a paleo- Neoproterozoic sedimentary rocks repre- sol. The trough cross-bedded sandstones, sented by the Prosperança Formation, cover- possibly of Paleozoic age, which overlies ing the Guianas Shield in the northern part unconformably the Prosperança Formation of the Amazon craton, are poorly exposed migrated to NE and is in contrast to the SW- when compared with the Paleo to Mesoprot- directed cross-stratification of the Prosper- erozoic sedimentary record of this craton. ança sandstones Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 29 ular sandy channels interbedded in flood- FLUVIAL RESPONSE TECTONIC FOLDING plain siltstones. The channels’ position shift- AND TILTING IN THE EOCENE FORELAND ed step by step up section suggesting pulsate BASIN, NW ARGENTINA migration of the thalweg of the valley. This Cecilia del Papa,1 Fernando Hongn1 stratigraphic relation is interpreted as conse- 1 CONICET-Universidad Nacional de Salta, Av. Bolivia quence of local slow lateral cross-valley tilt- 5150, 4400 Salta, Argentina. delpapacecilia@ ing. yahoo.com, fhongn@aol.com References The Andean foreland basin (Middle Eocene-Present) in northwest of Argentina is Hongn, F., del Papa, C., Powell, J., Petrinovic, characterized by very thick (ca. 8000 I., Mon, R. and Deraco, V. (2007). Middle meters) and coarsening upwards sequences Eocene deformation and sedimentation in the Puna-Eastern Cordi l lera transit ion deposited in fluvial and alluvial fan environ- (23º-26ºS): Control by preexisting hetero- ments. The Middle Eocene basal deposits are geneities on the pattern of initial Andean well-recorded in the Puna-Cordillera Oriental shortening. Geology, 35, 271-274. transition, where syn-tectonic sedimentation in a complex style basin has been recently documented (Hongn et al., 2007). INTEGRATED MODELING OF FLUVIAL FAN These basal orogenic sequences are char- FRINGE SHEET SANDSTONE: TEN BOER acterized by thick reddish siltstones and fine- CLAYSTONE MEMBER, SOUTHERN to coarse- grained sandstones and conglom- PERMIAN BASIN, NW EUROPE eratic levels deposited in extensive flood- M.E. Donselaar,1 I. Overeem,2 J.H.C. Reichwein,3 plains and moderately sinuous channels and C.A. Visser3 bar- braided alluvial settings. Notwithstand- 1 Dept. of Geotechnology, Delft Univ. of Technology, ing local tectonic activity produced varia- Delft, P.O. Box 5048, 2600 GA Delft, The Nether- tions in the fluvial drainage. lands. Email: m.e.donselaar@tudelft.nl Well-exposed tectonic structures at Sala- 2 Institute of Arctic and Alpine Research, Univ. of dillo (northern Calchaquí valley) permit con- Colorado, Campus Box 450, Boulder, 80309-0450, fidence fluvial architectural reconstructions. Colorado, USA. A west-vergent growth fold produced pro- 3 Nederlandse Aardolie Maatschappij B.V., Assen, gressive unconformity surfaces and cumula- The Netherlands. tive wedge-fan strata geometry. Strata are sandy fluvial channels and are characterized The secondary reservoir potential of fluvi- by fined-grained sandstones and very shal- al sheet sandstone beds in the Ten Boer Clay- low channels in the pre-growth levels to stone Member (TBCM) was investigated, coarse-grained sandstones and narrowing of with the aim to boost gas production in de- channels in the sin-growth levels. Once the clining smaller fields surrounding the giant folding processes ceased the sedimentation Dutch Rotliegend Slochteren Gas Field. The re-establish it previous equilibrium with TBCM is a 40-110-m-thick shale-prone suc- fined-grained sedimentation in the post- cession with thin fluvial sheet sandstone beds growth levels. In this case, the coeval fold- deposited on a mud flat at the edge of the ing aroused local migration, and steepening Silverpit Desert Lake in the Southern Permi- of the fluvial gradient. an Basin of northwest Europe. Sedimentary On the other hand, in the Tres Cruces structures in the 5-50 cm thick, very-fine to area (Jujuy province), the sin-sedimentary medium-grained sandstone beds are wave deformation is only evident by the careful ripple lamination, climbing-ripple and observation of channels position up se- trough cross-lamination. Sand injection quence. In this area, basal Andean foreland structures are common. Combined core and sequences are characterized by highly lentic- well-log analysis allowed for the subdivision 30 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 of the succession in lithofacies cycles. Each both the onset of the hyperarid climate re- cycle comprises a shaley base, a sandy-silty gime that currently prevails along western middle part and a shaley top, interpreted as coast of South America and the beginning of the result of wet-dry-wet climate cyclicity. Andean uplift. The surface is formed due to Log correlation of the TBCM succession in a alluvial-fluvial processes and is well devel- 300 by 160 km area resulted in a 3-D static oped on the western flank of the High Andes reservoir architecture model of the fluvial where it can be traced westwards from over sheet sandstone and showed the development 3000 m to 1000 m in the Longitudinal Valley in space and time of nested sandstone sheets of northern Chile and close to sea-level in at the end of widely spaced south-north elon- northernmost Chile and southern Peru. It gated fluvial pathways. ranges from 30 to 100 km in width and dips Challenges were to assess the size, shape, westwards at between 1.5 and 3°. The pe- spatial distribution and connectivity of the diplain comprises 1 to 10 m thick gravels sheet sandstone. To achieve this, an outcrop that unconformably overlie a 3 to 8° westerly analogue study and process-driven forward dipping erosion surface developed on under- modeling experiments were carried out. The lying Oligo-Miocene sediments and Pale- outcrop study in the distal part of the Hues- ocene and older igneous rocks. Age con- ca Fluvial Fan (Miocene, Spain) provided a straints based on stratigraphic relationships depositional model and size and shape data bracket the age of formation as between 16 of terminal sheet and crevasse splay and as- and 8.3 Ma. sociated meandering river sandstone. The Analysis of satellite imagery, aerial pho- data sets were used as input in forward mod- tographs and field studies reveal the presence eling experiments. Depositional scenarios of extensive alluvial-fluvial networks devel- were performed for two populations of fluvi- oped on the surface. These surfaces were al channels: larger channels representative characterised and correlated from Southern for the lower floodplain and smaller, distrib- Peru through to the Central Depression. By utary channels at the most distal fringes of using cross cutting relationships, previous the fluvial fan. The model results provided studies of the planation surfaces, cosmogen- insight in plume depositional thickness, area ic isotope exposure ages and the age of su- and volumes and distribution of sand depos- pergene enrichment located on each surface ited at the mouth of these channels. the chronostratigraphy of the planation sur- The results of this study provide scenarios face can be reconstructed. These observa- to assess volume and connectivity potential tions for planation surface formation indi- of thin-bedded distal fluvial reservoir sand- cate that it is a composite feature compris- stone bodies in the TBCM. ing a number of depositional and erosional events superimposed on each other which predate Andean uplift and formed during a GEOMORPHOLOGICAL DEVELOPMENT OF number of ‘wetter’ phases related to global THE ATACAMA PLANATION SURFACE climatic events dating back to 23 Ma. L.A. Evenstar,1 A.J. Hartley1 1 Depar tment of Geology & Petroleum Geology, School of Geosciences, University of Aberdeen, A SEDIMENTARY QUANTITATIVE MODEL Aberdeen, AB24 3UE. Email; l.evenstar@abdn.ac.uk FOR THE BAJO BARREAL FORMATION (CRETACEOUS): INTEGRATION BETWEEN The Atacama Planation Surface forms an OUTCROPS AND SUBSURFACE DATA. SAN extensive westerly dipping, planar surface JORGE BASIN, SANTA CRUZ, ARGENTINA developed between 17°S and 27°S along the Leonor Ferreira,1 Sergio M. Georgieff,2 Agustina Pacific margin of South America. The plana- Santangelo,1 Yanko Kamerbeek1 tion surface is assumed to have formed at a 1 YPF SA, Av. Libertador 520, Km3, 9000 - Como- single time and has been used to constrain doro Rivadavia, Argentina. Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 31 2 IESGLO – UNT, Conicet, Miguel L i l lo 205, these values were 25% higher to those mea- T4000JFE – San Miguel de Tucumán, Argentina. sured in outcrops and seismic horizons. The data coming from different sources The outcrops around the La Sin Nombre (surface and subsurface) allow optimizing Lake belong to the Bajo Barreal Formation the quantitative sedimentary model for the (Cretaceous, Chubut Group). These deposits Bajo Barreal Formation and improve the oil are analogs to the hydrocarbon-bearing res- and gas production. ervoirs in the adjacent Cerro Guadal Norte oil field (YPF SA). At the present day, the References Bajo Barreal Formation is the major oil unit in the San Jorge Basin (Santa Cruz Prov- Santangelo, A.; Ferreira L.; Georgieff, S. (2009) ince, Argentina). The distance between out- Characterization of fluvial geoforms from crops and the nearest oil well is about 600m 3D seismic: examples for Cerro Guadal Norte oil field, Chubut Group (Cretaceous), and this one is towards the East-Northeast San Jorge Basin, Argentina. 9th ICFS, Tu- direction of the outcrops. cuman, Argentina. In the outcrops, the dip ranges from 45ºE Bridge John S. and Tye Robert S., (2000).Inter- (in the base) to 15ºE (at the top). A vertical preting the dimensions of ancient flucial stratigraphic profile was measured in the out- channel bars, channels, and channel belts fron wireline-logs and cores. AAPG Bulletin, crops and 15 fluvial sandstone bodies were V.84, Nro. 84, P.1205-1228. recorded. The thicknesses of the sandstone bodies vary from 1.5 to 3 m and the width from tens to hundreds meters. The paleocur- A FACIES MODEL FOR FLUVIAL SYSTEMS rent measurements indicate that the outcrops IN THE SEASONAL TROPICS AND are normal to oblique to the paleoflow direc- SUBTROPICS tion and the sinuosities were obtained. Christopher R. Fielding,1 Jonathan P. Allen,1 Jan In the other hand, a detailed analysis was Alexander,2 Martin R. Gibling3 performed in the oil-well by using microre- 1 Department of Geosciences, 214 Bessey Hall, Uni- sistive log images, cuttings and a set of log- versity of Nebraska-Lincoln, Nebraska 68588-0340, curves. The log images allowed defining the USA (cfielding2@unl.edu) synthetic sandstone-bodies; besides, the sed- 2 School of Environmental Sciences, University of imentary structures, the thickness, and esti- East Anglia, Norwich, Norfolk, NR4 7TJ, UK. mations of paleocurrent directions were re- 3 Department of Earth Sciences, Dalhousie University, corded. By comparing the surface deposits Halifax, Nova Scotia B3H 3J5, Canada. with the images, it was possible to make a facies analysis and define the presence of flu- Facies models that summarize the depos- vial bars and channels. its of fluvial systems are well-established for Thus, the stratigraphic correlation be- humid climate settings and for desert envi- tween outcrops and the oil well mentioned ronments, but the deposits of rivers in the above is performed by using the seismic sec- sub-humid and semi-arid seasonal tropics tions. A set of seismic horizons were devel- have been largely ignored. Yet, such rivers oped, which is considering the amplitude as drain large portions of Australia, Asia, South a seismic attribute and useful tool to define America, and Africa. These rivers experience fluvial geoforms (Santangelo et al., 2009). strongly seasonal discharge, and drain land- The integration among data (outcrops, scapes where there is a considerable excess oil-well and 3D seismic) allowed obtaining of evaporation over precipitation and high important fluvial parameters. The width is surface temperatures. One consequence of from 150 to 250 m, while the sinuosity varies this is that trees colonize the beds of rivers from 1.15 to 1.35. The Bridge and Tye’s to utilize the reliable water source, and are (2000) equation was applied to calculate the adapted to this unusual ecological niche channel-width from log images, although where they are intermittently inundated by 32 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 fast-flowing water. It follows from their under high flow stage, and 5) an abundance abundance today and from the past position of in situ trees that colonize channel floors of continental landmasses that the deposits and are adapted to inundation by fast-flow- of seasonal tropical rivers must be well-rep- ing water. We illustrate examples of this flu- resented in the stratigraphic record, but per- vial style from the rock record, and set out a haps are under-represented in the literature new facies model. The recognition of such a because they are in some respects transition- distinctive fluvial character, and of changes al between humid and arid end members. in character through vertical successions, Several major rivers drain large, sub-hu- will aid paleoclimate and reservoir analysis. mid to semi-arid areas of NE Australia in- cluding the Burdekin River which drains an area of 129,000 km2 and discharges onto SHEET-LIKE FLUVIAL ARCHITECTURE ON the Great Barrier Reef shelf. Much of the REGIONAL SCALES: EXAMPLES FROM THE catchment experiences mean annual rainfall CRETACEOUS WESTERN INTERIOR of 500–700 mm. Precipitation is very strong- SEAWAY OF NORTH AMERICA ly seasonal, variable from year to year, and Christopher R. Fielding,1 Matthew J. Corbett,1 controlled by the passage of tropical cy- Lauren P. Birgenheier2 clones and monsoonal depressions. Intense 1 Department of Geosciences, 214 Bessey Hall, Uni- rainfall events cause short-duration, high- versity of Nebraska-Lincoln, Nebraska 68588-0340, magnitude runoff events (20,000 – 30,000 USA (cfielding2@unl.edu) m3s-1 discharge events have a 10-16 yr re- 2 Energy & Geoscience Institute, University of Utah, turn period). Event hydrographs for this and 423 Wakara Way, Suite 300, Salt Lake City, Utah other rivers of NE Australia rise extremely 84108, USA. rapidly to a sharp peak and decline almost as rapidly. During the falling stage, riverbed Extant sequence stratigraphic models for macroforms and mesoforms formed under lowland/coastal plain fluvial successions Froude-supercritical flow conditions, and emphasize vertical changes in stratal stack- large scale dunes formed in deep subcritical ing patterns through a cycle of relative sea- flow are frequently preserved as there is in- level change. According to these models, in- sufficient time for them to adapt to falling cised valley surfaces form during drawdown stage conditions. Whereas the hydrology of and lowstand of relative sea-level, are filled these rivers is similar to those in other and then pass upward into more isolated flu- strongly seasonal climatic settings, the com- vial sandstone bodies formed during rising bination of strongly variable discharge and relative sea-level, and in turn become more river bed vegetation growth gives rise to dis- amalgamated during highstand. It is appar- tinctive characteristics. Our observations and ent, however, that not all lowland fluvial data from modern streams and recent depos- successions conform to this pattern, with its in NE Australia show how such rivers, many showing sequence boundaries of more with extremely variable discharge, have dis- planar cross-sectional geometry (ie., lacking tinctive deposit characteristics that are sub- significant valleys). Here, we draw attention stantially different from conventional fluvial to this under-appreciated stacking pattern facies models. These properties include 1) by documenting the stratal architecture of erosionally-based channel-fill lithosomes three Upper Cretaceous formations, broadly that exhibit complex lateral facies changes, of coastal plain origin, from the Henry with 2) abundant, pedogenically-modified Mountains of south-central Utah, USA. The mud partings, 3) complex internal architec- succession as a whole represents a con- ture that may lack the macroform elements densed equivalent of the better-known Book (lateral/downstream accretion structure) typ- Cliffs succession 100 km to the north. ical of other fluvial sediment bodies, 4) an In the Henry Mountains, the Ferron Sand- abundance of sedimentary structures formed stone comprises a stack of progradational Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 33 deltaic bodies, overlain by a series of dis- Bosco”, Ruta Provincial N° 1 S/N Km. 4, (9005) tributary channel sandstones and coastal Comodoro Rivadavia, Chubut, Argentina - CONICET. floodbasin deposits. The channel bodies in Consejo Nacional de Investigaciones Científicas y the latter appear to be amalgamated lateral- Técnicas. ly to form single- to locally multi-storey channel complexes of 10’s of km extent in a The upper Paleocene Río Chico Formation depositional strike orientation. Lateral ex- in the Golfo San Jorge basin (Central Pat- tent of these composite bodies is at least an agonia) is a 150-180m thick fluvial succes- order of magnitude greater than the channel sion. This work consists of a description and belt width predicted from paleohydraulic interpretation of stratigraphic sections of the calculations or channel form dimensions. North Flank of the basin, from the northern Accordingly, the stack of sheet-like channel basin margin to the southern depocenters. complexes, separated by equally laterally The palaeoenvironment analysis is primarily extensive floodbasin intervals, may be inter- based on the identification of lithofacies and preted as a series of sequences, forced by rel- lithofacies associations. Spatial and tempo- ative sea-level fluctuation. The overlying ral variations in the fluvial dynamic were Muley Canyon Sandstone contains two inter- also analyzed by means of a detailed archi- vals of tidally-influenced fluvial deposits en- tectural analysis. Six lithofacies associations closed by shoreface sandstones. Again, these were identified in the Río Chico Formation: intervals are of regional extent (>20 km) 1) sheet-flood deposits; 2) braided channels; and sheet-like, with modest erosional relief 3) straight to low-sinuosity channels; 4) me- (<10 m) on basal sequence boundaries. The andering channels, 5) proximal floodplain most spectacular example of the sheet-like and 6) distal floodplain. fluvial stacking pattern occurs in the overly- At the northern basin-margin (e.g. Estan- ing Masuk Formation, where several cycles cia Las Violetas, Estancia Chapital, Meseta of fluvial channel bodies and intervening del Curioso) the Río Chico Formation con- coastal floodplain facies can be traced over sists of a sandstone-rich succession (up to >10 km as continuous sheets, again strongly 75%) of sandy-gravelly channels with tabu- suggesting an external forcing control on lar appearance (W/Th=300-850) and low their cross-sectional geometry. The common palaeocurrent dispersion (S<1.3), interpret- factors among these three formations are the ed as a braided system. Tabular, single-event prevalence of a sheet-like architecture to flu- sandbodies containing high-regime structures vial units, and their enclosing stratal inter- were interpreted as sheet-flood deposits, ac- vals, the condensed and incomplete nature of cumulated during high-discharge flood sequences, and the lack of significant inci- events. sional relief at the base of sequences. These In a basinward direction (e.g. Pto. Visser, patterns suggest that fluvial channel com- Punta Peligro Norte) channel sandbodies rep- plexes apparently lacking incised valley fills resent ~25% of the sections and multi-storey may in some cases nonetheless be records of sandbodies are narrow sheets with W/Th ~ external forcing and may be of great lateral 30. Most of the sandbodies show abundance extent. of cut-fill structures and lack of lateral mi- gration, displaying low palaeocurrent disper- sion (S<1.5), being interpreted as straight to SEDIMENTOLOGY AND STRATIGRAPHIC low-sinuosity channels. Some channels con- ARCHITECTURE OF THE UPPER PALEOCENE tain lateral accretion surfaces and show RÍO CHICO FORMATION, GOLFO SAN high palaeocurrent dispersion, being inter- JORGE BASIN, PATAGONIA ARGENTINA preted as high-sinuosity fluvial channels Nicolás Foix, José M. Paredes (5>S>1.7). Dpto. de Geología, Facultad de Ciencias Naturales, Lateral/vertical changes in the alluvial Universidad Nacional de la Patagonia “San Juan architecture of the Río Chico Formation are 34 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 recognized by: 1) spatial and temporal vari- transport occurred during Lateglacial and ations in fluvial styles, 2) changes in the ge- early Holocene and stopped around 8.0-7.0 ometry of sandbodies and 3) changes in ka cal. BP. Since 7.0 ka cal. BP some aban- channel/floodplain ratio across the basin. doned incisions were drowned by marine Tabular, braided systems with high channel/ transgression; this process led to the forma- floodplain ratio are recognized close to the tion of 15-km long tidal inlets and to the basin margin, while in a basinward direc- deposition of lagoon and estuarine sediments tion the channel/floodplain ratio reduces inside the incisions. This particular palaeo- and sandbodies show meandering and geographic setting played a major role in straight to low-sinuosity patterns. These constraining the ancient human settlements. stratigraphic changes are interpreted as spa- Valley formation has been mainly con- tial/temporal variations in the accommoda- trolled by the dramatic change of sedimenta- tion rate, controlling the aggradation rate of ry supply occurred at the LGM/post-LGM the alluvial system and fluvial styles. boundary, due to the transition from fluvio- glacial to fluvial processes. Also the valley lakes, triggered by the large landslides oc- POST-LGM INCISED VALLEYS IN THE curred in the mountain catchments after de- VENETIAN-FRIULIAN PLAIN (NE ITALY) glaciation, largely contributed to stop the Alessandro Fontana sedimentary flux towards the plain. The IVFs Department of Geography - University of Padova, Via have been affected by the internal evolution Del Santo 26, 35123 Padova (Italy). of the fluvial systems and specially by the alessandro.fontana@unipd.it avulsions, which activated and/or deactivat- ed different sectors of the megafans, and, Recent geological surveys and cores al- thus, different incisions. Sea-level rise influ- lowed to identify several incised valleys in enced the filling of the valleys only since 8.0 the distal sector of the alluvial megafans ka cal. BP, but this factor had a paramount between Venice Lagoon and the Karst Range. importance in the last millennia. The phase From East to West, at least 2 incisions exist of fluvial ridges formation which interested in the Isonzo-Torre River megafan, 5 in the the Venetian-Friulian coastal plain during Tagliamento River megafan and 4 in the Pi- late Holocene, specially since 3.0 ka cal BP, ave River megafan. brought to silt-up the valleys almost com- A major depositional phase occurred in pletely. the area during LGM, when sedimentary sup- ply fed by glaciers debouching in to the plain supported a large and widespread aggrada- POROSITY PREDICTION FOR FLUVIAL tion. Along the present coastal plain, LGM SAND-GRAVEL MIXTURES deposits are mud-dominated and have an Frings, R.M.1 average thickness of 20-30 m. These sedi- 1 Dept of Physical Geography, Utrecht University, PO ments are cut by valleys which have a depth box 80115, 3508 TC Utrecht, Netherlands. of 15-30 m and a width of 600-2000 m. The 1 Dept M3, Bundesanstalt für Gewässerkunde, PO studied incised-valley fills (IVF) display a box 200253, D-56002 Koblenz, Germany. similar internal architecture, characterized 1 R.Frings@geo.uu.nl by coarse gravel deposits at bottom and a general fining-upward trend. Several phases The porosity, defined as the ratio of pore of abandonment and re-activation are re- volume to total volume, is one of the key prop- corded, but gravels are almost lacking in the erties of sediment mixtures. It determines the upper part of the IVF and their diameter is storage capacity for oil, gas and groundwa- considerably finer than the basal gravel. ter, the pressure fluctuations leading to initia- Radiocarbon datings demonstrate that tion of sediment motion, the oxygen flow into fluvial entrenchment and coarse-gravel the hyporheic zone, the efficiency of measure- Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 35 ment devices and affect many other processes. of the river Rhine and by incorporating the The porosity of fluvial sediments can be mea- predictors into the morphological modelling sured with standard well-logging techniques, software Delft3D. such as neutron probes, but also be predicted with porosity predictors. The objective of this study was to determine the accuracy of such CHARACTERIZATION OF FLUVIAL porosity predictors for modern, fluvial, sand- SANDSTONES IN CERRO GUADAL NORTE gravel mixtures. OIL FIELD, GOLFO SAN JORGE BASIN, To obtain an accurate, independent data- SANTA CRUZ, ARGENTINA base of porosity data, we collected 52 large, Sergio M. Georgieff,1, 2 José A. Sosa Gómez,1 homogeneous sediment samples from the Leonor Ferreira,3 María Eugenia Vides,4 Lucía M. channel bed of the river Rhine. A diving bell Ibañez,1,4 Ramona Ovejero,1 Gerardo E. Bossi,1 was applied to prevent sediment loss by Agustina Santangelo,3 Guillermo A.V. Richter,5 flowing water during sampling. Sediment Karina B. Anis,1 Esteban M. Pieroni,3 Sebastián size ranged from 0.06 mm to 125 mm, with Moyano,1 Yanko Kamerbeek3 distributions varying from unimodal to bimo- 1 IESGLO – UNT, Conicet, Miguel L i l lo 205, dal. The porosity was determined in-situ T4000JFE – San Miguel de Tucumán, Argentina. with the water-saturation method and found 2 Consejo Nacional de Investigaciones Científicas y to vary between 10 and 40 percent. Labora- Técnicas, CONICET. tory analysis included determination of grain 3 YPF SA, Av. Libertador 520, Km3, 9000 - Como- size, grain shape and ex-situ porosity. doro Rivadavia, Argentina. The capability to reproduce the measured 4 Fundación Miguel L i l lo, Miguel L i l lo 251, porosity values was tested for six porosity pre- T4000JFE, San Miguel de Tucumán, Tucumán, dictors, using the median grain size (D), the Argentina. sediment standard deviation (s) or the full 5 Minera Aguilar SA, Jujuy, Argentina. grain size distribution (GSD) as input param- eter. Whereas the D-based predictors were The extensive Cretaceous fluvial outcrops, found to be theoretically unsound, the s-based around the La Sin Nombre Lake, allow per- predictors realistically predict a decrease of forming stratigraphy, sedimentology and tec- porosity with mixture bimodality. The sophis- tonic studies. The outcrops belong to Bajo ticated GSD-based predictors, however, per- Barreal Formation and correspond to the form best. Although these predictors tend to sides and the plunge of an asymmetrical an- underestimate the porosity slightly, they pro- ticline oriented North-South. The study area duce equally good results as empirical predic- is an active oil field belonging to YPF SA at tors based on the Rhine data. the north of Santa Cruz Province in the Golfo The relatively high error variance of the San Jorge Basin, Argentina. predictions illustrates that apart from grain One hundred fifteen sandstones and twen- size, other parameters have a distinct influ- ty mudstones were sampled from three ence on porosity. Especially the angularity of stratigraphic profiles; all the samples were the grains seems to be important, as it deter- georeferenced with gps and sandstones were mines the bridging tendency during packing. oriented to the magnetic north. Petrography The mechanism of deposition is thought to and porosity studies were realized from thin play a vital role too, because it governs the section and the mineralogy of mudstones, magnitude and direction of forces during the cements and matrixes of sandstone were packing. searched using X ray diffractions (Ibañez et Despite their shortcomings, porosity pre- al. 2009; Vides et al. 2009, in this volume). dictors provide valuable insights into the The structural geology was studied spatial variability of porosity in rivers and through field works and seismic line analy- river deposits. This is demonstrated by apply- sis, and it shows the interplay between ex- ing the predictors to 4,500 measured GSDs tensive and compressive stresses contempo- 36 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 raneous with the sedimentation (Sosa itation and mass wasting. It has been debat- Gómez et al. 2008). The faults produced a ed if this precipitation-enhanced erosion is stacking of sandstone bodies in the western also influencing the kinematics of the orogen side of the anticline (Gutierrez et al. 2009, and a lack of consensus highlights the need in this volume). for more comprehensive understanding. The stratigraphic profiles were correlated As a part of multidisciplinary initiatives according their lithostratigraphic character- to understand the interplay between different istics and the interpretation is also support- earth processes, this study employs terrain ed with seismic data. The paleocurrent di- analysis techniques to estimate the pattern of rections show local orientations toward erosion across a major part of the Himalay- north (in the southern outcrops) either east an orogen. The spatial interrelationships or southeast (in the northern outcrops) but between the erosion pattern, precipitation all of them converge to the center-east area and the disposition of litho-tectonic units are of the oil field. This dispersion could be re- investigated in this study. lated to the activity of the faults during the The technique when applied to digital deposition. The sinuosity of channels is low elevation datasets identifies three major between 1.1 and 1.3. classes of hinterland catchment basins that The width of sandstone bodies range supplies sediment and water to the foredeep. from some few tens to 200 m or 300 m, only These classes are distinct by their size, fre- at the top of the sequence and in some few quency and “drained-litho-type”. These three channel belts the width could reach 600 m. classes of basins are disposed in three oro- The mean thickness varies from 1.6 to al- gen parallel bands. Moreover, the estimates most 3 m. of erosion are found to vary significantly The fluvial architectural studies indicate both across and along the orogen. It has lenticular isolated channel belts, mainly been noted that the erosion estimates for the monochannel but some multichannel belts interior parts the catchment basins are larger were also described. The thicker sandstone compared to that for their downstream ends. bodies represent permanent rivers, while the On the other hand, the central part of the thinner ones are interpreted as ephemeral orogen is found to be most intensely denuded crevasse channels with evidences of organic compared to its eastern and western extrem- activity onto a mud floodplain. ities. This pattern of denudation show signif- icant spatial correlation with the pattern of precipitation and the disposition of the litho- AN ESTIMATE OF THE PATTERN OF tectonic units of the Himalayas. FLUVIAL EROSION FOR THE HIMALAYAS Parthasarathi Ghosh Geological Studies Unit, Indian Statistical Institute, TRANSITION OF THE MIDDLE AMAZON 203 B.T. Road, Kolkata, India, pghosh@isical.ac.in RIVER IN THE CONTEXT OF CLIMATIC CHANGE The present-day physiography of the Hi- Jose Max Gonzalez Rozo ,1, 2 Afonso César malayan mountain belt, an active orogen, is Rodrigues Nogueira,2 Werner Truckenbrodt2 an expression of complex interplay between 1 Programa de Pós-graduação em Geociências, De- the tectonic and erosional processes. It has partamento de Geociências, Universidade Federal been hypothesized that the orographic barri- do Amazonas, Brasil. jmaxgr@ufam.edu.br er initially produced by the tectonic uplift 2 Programa de Pós-graduação em Geologia e Geoquí- was sufficiently large to induce monsoonal mica, Instituto de Geociências, Universidade Fede- circulation leading to enhanced precipitation ral do Pará, Brasil. over the orogen. After the last deglaciation a major part of the orogen is being denuded by The Amazon River is the main component fluvial processes aided by monsoonal precip- of a complex ecosystem characterized by Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 37 high biodiversity in the Amazon rainforest. sebasgrignola@hotmail.com The evolution of this system, especially dur- 2 Consejo Nacional de Investigaciones Científicas y ing the Holocene, is still not well under- Técnicas, CONICET. stood, with only a few detailed characteriza- 3 YPF SA, Av. Libertador 520, Km3, 9000 - Como- tions of small sections of the system report- doro Rivadavia, Argentina. mlferreirap@ypf.com ed. In this context we studied the middle Amazon River between Manaus and the The interpretation of resistivity imaging mouth of the Madeira. The use of remote logs allows identifying sedimentary struc- sensing tools and geomorphologic and tures, thicknesses, contacts hierarchies, pale- stratigraphic analysis allowed the identifica- ocurrent directions and other details (e.g. tion of an anastomosing pattern of the Ama- bioturbation, intraclasts, root fragments and zon River, based on a very low gradient, clay an inference of grain size). These data were dominated, vegetated, rather permanent is- compared with cutting samples and outcrops lands, whose heights roughly correspond to data in order to improve the sedimentologi- those of the adjacent floodplain, steep-sided cal model for Bajo Barreal and Castillo For- channel margin with locally displaced mations (Cretaceous). blocks (“terra caída”). Also indicative of this The Cañadón Vasco oil field is located in patterns are great water-depth near the bank the southern border of the Golfo San Jorge and outlines of islands and channels that Basin (Argentina); near to the oil field, the have remained largely unchanged over the Ballena Hill shows extensive fluvial deposits period from 1986 to 2001. Beyond classify- belonging to Bajo Barreal Formation. Thus, ing this reach of the Amazon River as anas- a stratigraphic correlation between them tomosing, evidence is provided for its evolu- was proposed by using seismic lines. The tion from meandering during the mid Ho- Ballena Hill and the Cañadón Vasco oil locene. This evidence is strongly supported fields show a strong tectonic control pro- by the presence of inclined heterolithic strat- duced by a NW-SE normal fault reversed dur- ification of point bars. Additionally, the point ing Late Cretaceous. bars exhibit distinctive morphological sets of The integration of cutting samples (grain scroll bars indicating a multistory lateral size and color) and resistivity imaging log migration of the Amazon River before evolv- allowed obtaining a stratigraphic log. ing into an anastomosing pattern. Twelve sandstone bodies belonging to Bajo We propose that climate change leading Barreal and Castillo Formations were ana- to increased humidity as recorded between lyzed following this method and ten litho- 6000 and 4000 yr BP, correlated with a rela- facies were defined from this study. The tive base-level (sea-level) rise, influenced the litho-facies assemblages were assigned to development of the fluvial pattern change. channel, crevasse channel, channel bar, splay and floodplain deposits. The sandstone bodies thickness (trough cross stratification) INTERPRETATION AND FLUVIAL and paleocurrent directions were used to PARAMETERS OF SUBSURFACE apply the Mackey and Bridge’s equation SANDSTONE BODIES, CASTILLO AND (1995) and obtain the channel belt width. BAJO BARREAL FORMATIONS The sandstone bodies were also associated (CRETACEOUS) IN THE CAÑADÓN VASCO with the SP and resistivity wire-logs to de- OIL FIELD, GOLFO SAN JORGE BASIN, fine a group of electro-facies. Finally, seis- SANTA CRUZ, ARGENTINA mic horizon slices related to the sandstone Sebastián Grignola,1 Sergio M. Georgieff,1, 2 Leonor bodies studied were also analyzed as intent Ferreira3 to merge litho– and electro-facies assem- 1 Facultad de Ciencias Naturales – Universidad Na- blages and seismic geoforms. cional de Tucumán, Miguel Lillo 205, T4000JFE, As paleocurrent directions coming from San Miguel de Tucumán, Tucumán – Argentina. imaging log as seismic horizon slices are 38 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 coincident in to point out several changes in dry and fluid oil impregnations. The sand- the channel pattern and sinuosity. Most no- stone bodies appear isolated in the base of ticeable change occurs for those strata be- the stratigraphic log and they are stacked at longing to the lower section of Bajo Barreal the top of the sequence. The main geometry Formation (informally named “tobácea sec- is lenticular and frequently both margins are tion”). The sinuosity increases from 1.15 to exposed, but in few cases the geometry is around 2 and the channel belt wide reaches tabular. The strike of the strata is N10ºW 500m. and the dip varies from 6° to 12°W. The sedimentary model of electro-facies The area was recorded by gps, the base may apply to wells (in the same or another and top of all sandstone bodies, major and oil field) without assistance of imaging log secondary faults were mapped. The major but with available 3D seismic information. faults show dextral strike-slip motion, and they are listric faults. Short lateral logs, measurements of pale- TECTOSEDIMENTATION AND COMBINED ocurrent directions and photomosaics were TRAPS IN THE SANDSTONE recorded for the fourteen sandstone bodies in HYDROCARBON-BEARING OF THE BAJO order to reconstruct the geometries, orienta- BARREAL FORMATION (CRETACEOUS) AT tions and channel patterns of those Creta- LA SIN NOMBRE LAKE, GOLFO SAN ceous rivers. The grain size of channel belt JORGE BASIN, SANTA CRUZ, ARGENTINA deposits is medium to coarse sandstone and Raul Gutierrez,1, 2 Agustina Santangello3 fine gravel (mainly clasts of tuff), which are 1 Facultad de Ciencias Naturales e IML – Universi- associated to the faults activities. The main dad Nacional de Tucumán. Miguel Li l lo 205, sedimentary structure is trough cross strata T4000JFE, San Miguel de Tucumán, Argentina. but planar stratification and ripple marks 2 IESGLO (Instituto de Estratigrafía y Geología Sedi- were also observed at the top of the channel mentaria Global). Miguel Lillo 205, T4000JFE, San belt deposits. The mean thickness of sand- Miguel de Tucumán, Argentina. stones bodies is 1.23m and the standard de- 3 YPF SA, Av. Libertador 520, Km3, 9000 - Como- viation 0.98 but two main modes were ob- doro Rivadavia, Argentina. tained: 0.5-1m and 2-2.5 m; the first repre- sent crevasse channels and the second the The main purpose of this contributionis to main channels. The apparent width ranges proposes a sedimentary model that explains from 15m to 105 and the mean width is the syntectonic deposition of fluvial sand- 41.44 m and the standard deviation of 30.3. stone bodies in the Bajo Barreal Formation In order to obtain the paleocurrent direc- in the Golfo San Jorge Basin (Argentina). tions, fifty five trough cross strata were The study area is located in the western side measured in the stratigraphic profile and of La Sin Nombre Lake at the north of the from ten channel belts. The mean paleocur- Santa Cruz Province, approximately 46 ° 30 rent direction is toward N110º but varies ’51.8 “S and 69 ° 25' 48.1” W. The zone was from N320º to N193º. The facies and facies folded and faulted during the Late Creta- assemblages indicate sandy channel belts ceous and mainly during Tertiary. The axis flowed onto a silt-clayed floodplain. The of the anticline is oriented in north-south di- channel belts are formed by main and sec- rection. The deposits crop out on the western ondary channels, lateral- and mid-bars. side of the anticline. The deposits have been The deposition of the sandstones bodies assigned to the Bajo Barreal Formation (Cre- (high connectivity of channel belts), and the taceous) through lithostratigraphic correla- migration patterns were controlled by the tion and seismic data (Santangelo et al. main faults, which also behave as seals. 2009, in this volume). Along the stratigraph- ic log it is possible to recognize fourteen sandstone bodies; most of them show both Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 39 very well rounded and comprise a range of SEDIMENTOLOGICAL AND lithologies including mainly quartzite, PALAEOHYDROLOGICAL CONSTRAINTS ON andesite, metasediments and granites. Max- THE DEVELOPMENT OF A LATE SILURIAN imum long axis clast sizes range from 5 to TO EARLY DEVONIAN ‘SYN-RIFT’ FLUVIAL 100 cm. Similar clast types and palaeocur- SUCCESSION IN THE MIDLAND VALLEY rents indicating derivation from the north- BASIN, SCOTLAND east, are present in both the underlying Adrian Hartley, Stuart Archer, Stephanie Davidson, sandstones and the conglomerates indicating Tim Davis, Laura Evenstar, Sophie Leleu no obvious change in source area composi- Department of Geology & Petroleum Geology, Univer- tion or location across this major grain size sity of Aberdeen, Aberdeen, AB24 3UE, U.K. transition. Palaeohydrological data derived a.hartley@abdn.ac.uk from Manning’s equation, which uses clast dimensions to estimate discharge, suggest The approximately 9000 m thick Upper that the conglomerates were deposited by Silurian to Lower Devonian fluvial succes- high magnitude flood events. A comparison sion in the Midland Valley Basin, Scotland with modern day systems in which similar (referred to as the Lower Old Red Sand- flood events occur indicates a basinal loca- stone), has been studied extensively over the tion immediately adjacent to a high relief last 150 years. Deposition is thought to have catchment. This suggests the presence of a occurred in an active extensional/transten- high relief catchment immediately NE of the sional basin and a number of models have basin in contrast to previously published been proposed to explain the documented models. In addition, whilst this is a prelimi- facies and provenance data. Two end-mem- nary study, it appears that palaeohydrologi- ber models have emerged that include either, cal information can greatly enhance our un- 1) derivation from a large-scale axial fluvial derstanding of ancient fluvial successions. system that drained a source area located to the east on the Baltic Shield or 2) deposition on alluvial fans that formed along an active DISTRIBUTIVE FLUVIAL SYSTEMS (DFS): A fault (the Highland Boundary Fault) along RE-EVALUATION OF FLUVIAL FACIES the northern flank of the basin. In order to MODELS assess which, if either, of these models may A.J. Hartley,1 G.S. Weissmann,2 G.J. Nichols3 be appropriate we have undertaken a sedi- 1 Department of Geology & Petroleum Geology, mentological study of the lower part of the School of Geosciences, University of Aberdeen, Lower Old Red Sandstone succession with the Aberdeen, AB24 3UE, U.K. a.hartley@abdn.ac.uk aim of identifying the nature of the alluvial 2 University of New Mexico, Department of Earth and system and to apply palaeohydrological tech- Planetary Sciences, MSC03 2040, 1 University of niques to determine possible discharge esti- New Mexico, Albuquerque, NM 87131-0001, mates from which to provide information on U.S.A. the drainage basin. 3 Department of Geology, Royal Holloway, University The Lower Old Red Sandstone succession of London, Egham, Surrey, TW20 0EX, U.K. shows a rapid transition from discrete sand- stone bodies that form channel packages 1 Analysis of ~700 modern continental sed- to 3 m thick separated by mudstones, into 1 imentary basins from around the world (i.e., to 10 m thick packages of pebble and boul- those that may be preserved in the rock der conglomerates with sandstone interbeds record) reveals that rivers in these basins are (the latter comprise < 5% of the total out- not tributary in nature; rather they form ei- crop). The conglomerates are organised into ther (1) distributive fluvial systems (DFS), 1 to 5 m thick coarsening or fining upwards commonly called megafans, fluvial fans, and packages and display extensive imbrication. alluvial fans, or (2) axial stream systems Clasts within the conglomerates are well to that parallel the basin trend, with the vast 40 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 majority of sedimentation in the basin occur- Utrecht University, P.O. Box 80.115, 3508 TC, the ring on the DFS (up to 95%). Yet, most fluvi- Netherlands. al facies models are based on rivers in tribu- mphijma@hotmail.com, m.hijma@geo.uu.nl tary, degradational settings. In these conti- nental sedimentary basins, we identified This paper focuses on the palaeogeo- ~400 fluvial megafans (defined as DFS > graphic development of the Rhine-Meuse riv- 30 km in length), with numerous smaller er mouth (the Netherlands) in the early-mid- DFS filling the basins. Thus, most sedimenta- dle Holocene. During the Holocene transgres- ry basins undergoing aggradation do not sion, an area of 800 km2 transformed from contain tributary fluvial systems except in valley to estuary within 200 years (8.5-8.3 the axial position. ka BP: sea-level jump; Hijma and Cohen, Characteristic features of DFS that differ subm.). Initially, overbank deposition started from tributary systems include: 1) a radial to increase (fluvial onlap of lowstand system pattern of channels away from an apex (or tract) accompanied by widespread peat for- intersection point), 2) a downstream de- mation. The transition to the transgressive crease in channel width and discharge, 3) system tract (transgressive surface) is diach- floodplains dominated by avulsion deposits, ronous, but mainly occurred during the 4) greater preservation of floodplain deposits jump. The surface predominantly separates associated with braided streams. fluvial from fluvial-tidal deposits and is Studies of modern DFS indicate that gen- characterized by a gyttjaic deposit. Farther eral trends and relationships between plan- landward, the environment remained fluvial, form type, length, gradient, tectonic setting, but with subaqueous deposition within per- climate (in the catchment and basin) and manently flooded flood basins. After ~6 ka termination style can be observed in DFS. BP retrogradation of the coastline halted DFS length is controlled by the available and subsequently most tidal inlets closed and horizontal accommodation space which in extensive peat formation began at the base turn is strongly related to tectonic setting. of the highstand system tract. We will illus- The longest DFS occur in peripheral foreland trate the changing facies and transition with basins and cratonic settings where lateral several photos and detailed maps. systems can develop across an extensive bas- The study area is situated in a long term inwards slope. Extensional, strike-slip and subsiding basin (North Sea). Towards and intra-thrust belt basins are narrower and during the Last Glacial Maximum it was lo- have much more limited horizontal accom- cated just south of a zone of maximum fore- modation space. Consequently DFS devel- bulge upwarping and consequently in an oped in these settings are shorter with radii area of accelerated subsidence in Late Gla- often less than 30 km. DFS dominate in cial and early-middle Holocene times aggradational settings such as actively sub- (Busschers et al., 2007). Rates of relative siding sedimentary basins and will therefore sea-level rise were therefore high (> 1 m/ form a significant proportion of alluvial sed- 100 yr) and between 8.5-8.3 ka BP reached imentary successions preserved in the rock rates of > 2 m/100 yr. In the case of the record. Rhine-Meuse mouth, this is well reconstructa- ble because of 1) favourable antecedent to- pography and subsidence setting; 2) long his- FROM RIVER VALLEY TO ESTUARY: tory of coring, mapping, dating, establish- EUSTATIC AND GLACIO-TECTONIC ing facies models; 3) New 3D-techniques of CONTROLS ON THE EARLY-MIDDLE dealing with the wealth of data and 4) key HOLOCENE RHINE-MEUSE SYSTEM, THE papers produced in recent years: Busschers NETHERLANDS et al. (2007; last glacial), Hijma et al. Marc P. Hijma (2009; last glacial - Holocene) and Hijma Dept. of Physical Geography, Faculty of Geosciences, and Cohen (subm.; sea-level history). This Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 41 research increases our knowledge of the re- geographic contexts and compares the facies sponse of fluvial-estuarine systems to rapid in their distal floodplains. sea-level rise and therefore will benefit plan- 1) The first case is the Gómara Fm. in ning and designing coastal protection works the Palaeogene succession of the Almazán during the expected future sea-level rise. basin (Spain) which shows a thick (> 3000 m) fluvial record. The Gómara Fm. in the A3 References depositional sequence of the basin displays a highly vertical connected sheet like conglom- Busschers, F.S., Kasse, C., van Balen, R.T., erate bodies. These bodies are 20-30 m thick Vandenberghe, J., Cohen, K.M., Weerts, and 500-3000 m width, and the channel H.J.T., Wallinga, J., Johns, C., Cleveringa, body/floodplain proportion is 50.2 %. Later- P. and Bunnik, F.P.M. (2007) Late Pleis- tocene evolution of the Rhine-Meuse sys- ally, on the distal floodplain, there is an im- tem in the southern North Sea basin: portant development of mature calcretes. imprints of climate change, sea-level oscil- Sometimes several (3-5) calcrete profiles lation and glacio-isostacy. Quaternary Sci- occur stacked vertically. 2) The second case ence Reviews, 26, 3216-3248. is the Plio-Pleistocene (s.l.) fluvial fan depos- Hijma, M.P. and Cohen, K.M. (Submitted) Timing and magnitude of the sea-level jump pre- its of the Duero basin (Rañas), which are luding the 8,200 yr event. sheet like conglomerate bodies with high lat- Hijma, M.P., Cohen, K.M., Hoffmann, G., Van der eral connectivity that are associated with Spek, A.J.F. and Stouthamer, E. (2009) red muddy sands in the proximal areas From river valley to estuary: the evolution These deposits are several (5-20) km width, of the Rhine mouth in the early to middle Holocene (western Netherlands, Rhine- and commonly 2-5 m thick. The length from Meuse delta). Netherlands Journal of Geo- the mountain front (spill point) to the most sciences - Geologie en Mijnbouw, 88, 13- distal conglomerate outcrops ranges from 15 53. to 70 km. In the most of the cases the distal floodplain deposits has been eroded and evacuated, and only some relics are pre- SHEET LIKE CHANNEL BODIES, served in karstic depressions within the un- WEATHERING AND CALCRETES. A derlying upper Miocene limestones. The COMPARISON BETWEEN TWO EXAMPLES Raña deposits underwent intense weathering OF THE DUERO AND ALMAZÁN BASIN and pedogenesis, the most spectacular prod- (SPAIN) uct being the lateral washing of the finer Pedro Huerta, Ildefonso Armenteros, Pablo Gabriel matrix with subsequent residual gravel accu- Silva mulations toped by well-developed red soils. Dpt. Geology, University of Salamanca, EPS Ávila, The sheet-like conglomerates record the 05003 Ávila Spain. phuerta@usal.es stage of reduced accommodation space pre- ceding the Quaternary fluvial dissection of The way external forcing controls large the Neogene endorheic Duero Basin. scale fluvial architecture is even today a de- In both cases, tectonic uplift, eventual bate matter. The LAB (Leeder-Allen-Bridge) basin overfilling, stable planation surfaces models interpret high-density channel sys- linked to intense weathering (under different tems as the result of decreasing accommoda- climatic conditions), are linked to the epi- tion space and qualitative models predict sodes of decreasing accommodation space. In sheet like channel geometries for this stages. the latter case preceding the eventual fluvial However, some experimental models show dissection of the ancient sedimentary basin. linkage between development of high densi- Acknowledgements: this study has been ty channel belts and increasing basin ac- supported by the Spanish Research Projects commodation space. This study analyzes two CGL2005-05953 C02-01 and CGL2008- field examples with highly connected sheet 05584-C02-01. like channel bodies in two different palaeo- 42 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 reaches of active distributaries, the inactive CHANNEL ABANDONMENT PROCESSES IN distributaries and estuaries. THE MAHAKAM DELTA, EAST BORNEO, This study suggests that the channel INDONESIA abandonment processes in the Mahakam Salahuddin Husein,1 Joseph J. Lambiase2 Delta is sequential. As the tidal processes 1 Dept. of Geological Engineering, Faculty of Enginee- become more dominant, fluvially-supplied ring, Universitas Gadjah Mada, Jl. Grafika 01, sand is being stored onshore in the distribu- Yogyakarta 55281, Indonesia. shddin@gmail.com taries and tidal processes are modifying dis- 2 Lambiase Geoscience PTE LTO, 5000J Marine Pa- tributary morphology and dominating sedi- rade Road #24-42, Singapore 449291, Republic of mentary facies progressively further land- Singapore. ward. These processes influence the distribu- tion of the potential reservoir in the delta The modern Mahakam Delta has been plain. acknowledged as a typical example of a tropical mixed fluvial and tide-dominated delta. Its subaerial delta plain has a fan- PETROGRAPHY AND POROSITY IN shaped morphology and is dissected by nu- FLUVIAL HYDROCARBON–BEARING merous distributary and estuary channels. As SANDSTONES. BAJO BARREAL distributaries branch seaward out from the FORMATION (CRETACEOUS), SAN JORGE delta apex, they can be grouped into the BASIN, ARGENTINA northern and southern areas, while the cen- Lucía M. Ibañez,1, 2 Ramona Ovejero,2 Sergio tral area is only occupied by estuaries. Some Georgieff,2, 3 Leonor Ferreira,4 Gerardo E. Bossi2 morphological evidences suggest that distrib- 1 Fundación Miguel Lillo. Universidad Nacional de utaries can be abandoned and converted into Tucumán. estuaries. 2 Facultad de Ciencias Naturales e IML – Universi- This study investigates the distributary dad Nacional de Tucumán. Miguel Li l lo 205, abandonment processes in the northern area T4000JFE, San Miguel de Tucumán, Argentina. which has 3 distributaries and 3 estuaries. 3 CONICET – Consejo Nacional de Investigaciones Channels morphology was studied by 85 high Científicas y Tecnológicas. resolution echo-sounding profiles, bottom 4 YPF SA, Av. Libertador 520, Km3, 9000 - Como- sedimentary facies was reconstructed by 143 doro Rivadavia, Argentina. grab sediment samples and hydrodynamics data were systematically measured at 10 loca- Petrography and porosity studies were tions for complete spring and neap tidal cy- performed to improve the knowledge about cles. Distributaries exhibit relatively straight fluid migrations throughout Cretaceous fluvi- channels with flaring mouths while estuaries al sandstones in the Cerro Guadal Norte oil are more sinuous and have deeper and small- field (San Jorge Basin, Santa Cruz Province, er mouths. Sand is more distributed in the Argentina) and the additional hydrocarbon bottom of, and thus covered a larger part of, recovery projects. the active distributaries than in the aban- Upper section of the Bajo Barreal Forma- doned distributaries and gradually fines sea- tion (Turonian) is composed of fine and me- ward but does not extend to the channel dium sandstones which show mainly cross mouths while mud dominates the estuaries trough stratification but also planar, massive and the distal reaches of the distributaries. and ripple lamination. Occasionally, a silt Hydrodynamic data indicates that the inter- parallel lamination is observed at the top of action of fluvial and tidal processes is dy- sandstone bodies. namically active along the entire length of the The fluvial sandstone bodies are well ex- distributaries. Fluvial processes dominate the posed around La Sin Nombre small Lake, sandy reaches of the distributaries, while tides where two stratigraphic logs were described. are the most important process in the lower Besides, architectural descriptions in some Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 43 representative sandstones bodies, fully ex- aggradation by sanders and Gilbert-type del- posed, and additional short detailed logs sep- ta’s occurred at the margins of the lakes due arated by tens of meters each were recorded. to local high base levels. The associated Forty nine orientated medium sandstones glaciolacustrine varves enable to reconstruct were sampled along the vertical logs and in the duration of this high base level phase. a laterally described body. Two petrographic During deglaciation the ice dams disap- slides were prepared from each sample. One peared and the large proglacial lake in the is parallel to the plane formed by the strati- Ain valley drained almost instantaneously. fication surface and the North, and the other This rapid base level fall resulted in dissec- perpendicular to the North direction. There- tion of the deltas and formation of a wide- by ninety six slides were described. spread gravel sheet on the former lake bot- The sandstones are mainly feldspar lith- tom. Further incision by the Ain formed a arenites and there are some litharenites and terrace staircase in the deltaic and glaciola- feldspar wackes. Almost all of them are sub- custrine high-stand deposits. The upper ter- matures. The mean porosity is around 18 % races may be related to ice-recessional phas- which varies from homogeneous to hetero- es. This case study enlarges our understand- geneous. Clays, zeolitic, siliceous and car- ing of the impact of base-level changes on bonatic cements are present in different pro- the preservation of high-stand deposits portions. (coastal prisms). A comparison among petrography, poros- ity and architectural studies indicates an in- crease of zeolitic cements at the top of sand- WHY LARGE RIVERS HAVE LOW-ANGLE stone body; while the clays are predominant DUNES in the base of channels. Furthermore, the Ray Kostaschuk porosity decrease from main channel to ad- Department of Geography, University of Guelph, Guel- jacent bars and cross over bar-channel. In ph, ON, Canada, N1G 2W1 rkostasc@uoguelph.ca the bar deposit, the porosity decreases down- stream and upward. Dunes in flumes are Classic High-Angle Dunes (CHADs)dominated by bedload trans- port andcharacterized by steep (>30o) lee LATE WEICHSELIAN DEGLACIATION, BASE side slope angles and a separation zone with LEVEL CHANGES AND FLUVIAL flow reversalBed load is transported up the RESPONSE, AIN RIVER, JURA, FRANCE stoss side of the dune and accumulates at the C. Kasse brinkpoint. Bed load deposited at the brink- Department of Climate Change and Landscape Dyna- point periodically avalanches down the lee mics, Faculty of Earth and Life Sciences, VU Univer- slope, maintaining a steep angle of repose. sity Amsterdam, The Netherlands, emai l Field measurements however have shown kees.kasse@falw.vu.nl that dunes in large, deep rivers are not CHADS, but are Low-Angle Dunes (LADs) The behaviour of fluvial systems is con- with low lee side slope angles (often <10o) trolled by changes in climate, sediment sup- and a separation zone that is characterized ply, tectonics and base level which often op- by deceleration in streamwisevelocity rather erate simultaneously. In the present contribu- than flow reversal. LADS are believed to re- tion the effects of base level changes on the sult from deposition of suspended sand on the Ain river in eastern France during the last lee side slope and in the trough, resulting in glacial-interglacial transition will be evalu- a lower slope angle. ated. During the Last Glacial Maximum the This study uses reach-averaged data from river catchment was partially glaciated and seven rivers and two flume studies to test the blocked by the Jura ice cap leading to devel- LAD hypothesis. Flumes dunes are CHADs, opment of large proglacial lakes. Rapid with lee side slope angles from 38-51o, but 44 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 the field dunes are LADs, with lee slopes Discharge increased downstream from from 5-23o. Lee slope angle decreases as about 500 m3s-1 in the Bermejo to nearly dune size (height and length) increases, and 20,000 m3s-1 at Corrientes, due to the in- increases with height/length. Application of crease in watershed area and addition of an excursion length shows that sand sus- flow from tributaries. Wash load samples pended at dune crests in the flume bypasses were composed entirely of silt and clay and dune lee slopes, but it is captured on the lee particle size increased slightly downstream. slope in rivers. The deposition of suspended Wash load concentrations decreased down- sand on the lee sides of large dunes supports stream from nearly 8000 mgL-1 in the Berme- the LAD hypothesis. The critical factor in the jo to around 140 mgL-1 at Corrientes. Wash capture of suspended sand appears to be the load flux decreased by 50% between the Ber- streamwise length of the dune lee slope – mejo and Paraguay and then remained con- greater lengths result in increased sand cap- stant downstream to Corrientes. These pre- ture. Large rivers have large dunes with long liminary results suggest that wash load is lee slopes and hence lower lee slope angles. being diluted downstream in response to in- creasing discharge, but is also being deposit- ed in the Paraguay River between the Berme- WASH LOAD IN THE PARANÁ RIVER, jo and Paraná. ARGENTINA Ray Kostaschuk,1 Oscar Orfeo2 1 Department of Geography, University of Guelph, SEDIMENTATION SETTING AND Guelph, ON, N1G 2W1, Canada. QUATERNARY DEPOSITION rkostasc@uoguelph.ca Hasan Kuliçi,1 Jakup Hoxhaj2 2 Centro de Ecologica Applicada del Littoral (CECOAL), 1 Albanian Geological Survey. Corrientes 3400, Argentina. 2 Geosciences Institute, Polytechnic University of Tirana. The Paraná River has one of the largest hkulici@yahoo.com, jakuph2001@yahoo.com watersheds in the world, draining significant portions of Argentina and Brazil. The main The quaternary depositions, as in the oth- tributary of the Paraná is the Paraguay River. er regions, also in Albania, are related to Virtually the entire wash load, defined as many processes, which are created long time fine sediment (usually <64 ìm) in permanent before, but they continue until today (gla- suspension, present in the middle and lower ciers, sloppy, end sloppy, river net, sea and reaches of the Paraná originates in the Ber- lagoon processes). mejo River, which is a tributary of the Para- Quaternary depositions in general and so guay. do their sedimentation settings are very rep- Surveys in May 2008 were undertaken to resented and developed along the Albanian determine the discharge and wash load con- geological structures, beginning from these centrations at three sites in the middle reach continental, marine and their intermediate. of the Paraná: Bermejo River 50 m upstream The most completed conception for the set- of the confluence with the Paraguay River, tings, relates not only to the dimensions of Paraguay River 50 m upstream of the conflu- the basin development, but also with the re- ence with the Paraná River, and Paraná River lations which are created between them. So 300 m upstream of Corrientes Bridge. Veloc- the relation between river-sea-land and the ity and discharge at each site was deter- climatic changes of Plio-Quaternary to today mined with an acoustic Doppler current pro- gets many values. There are rivers which filer. Surface samples of wash load were tak- with their abrasive and conveyer activity fur- en at each site and analysed for concentra- nish the seas with water and sediments, and tion and particle size using a portable laser are these sediments that elaborate, according system. to circumstances in favour or disfavour, of Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 45 forming of the new land. In the dynamic point of view, it is evidently, these settings DETERMINATION OF RELATIONS BETWEEN and processes of the depositions are not THE TRANSPORT OF BOTTOM MATERIAL closed systems, but they are open systems AND SUSPENDED MATERIAL IN A LARGE that develop in neighbour areas, something RIVER, BASING ON GRAIN SIZE displacing one to the other some other times ANALYSIS OF DEPOSITS IN ARTIFICIAL extending in disfavour of one of them. WATER RESERVOIRS (THE VISTULA In this aspect, almost all the relief, oro- CATCHMENT BASIN, POLAND) genesis and the new Plio-Quaternary deposi- Adam Lajczak tions and Quaternary one, in Albania are Faculty of Earth Sciences, University of Si lesia, aggradations of the regressive marine pro- Bedzinska Str. 60, 41-200 Sosnowiec, Poland. cesses. Almost in up 80 % of the surface in Al- The results of grain size analysis of de- banian territories, these settings and deposi- posits accumulated in most of artificial wa- tions in them are consolidated under a dila- ter reservoirs of different size in Poland indi- tory elevator process, associated with consid- cate a considerable predominance of trans- erable erosion. Just in lower flows of the port of material suspended over the bottom. rivers, in their embouchures and along all Only some reservoirs (in the mountains and the shore, the processes are very dynamic and lowlands) lose their capacity as a result of are distinctly, minimally during two yearly the supply of bottom accumulation. With the cycles. river course, the grain size in both forms of transport increases, however, the increase of References bottom material transport occurs faster. The increase of the share of bottom material in Hoxhaj, J., Hysenaj, R., Bojaxhiu, M., Abazi, S., total transport of clastic material with the Kul iç i , H. and Gjoni V. ( 2005 ) S ome river course results for example from in- geolog-morphological estimations about the creasing in this direction size of sand frac- Albanian main rivers dynamic. Geological Science Bulletin. Nr.2. tion transport, which in upper sections of Hoxhaj, J., Hysenaj, R., Bojaxhiu, M., Abazi, S., rivers is rather transported as a suspension. Gjoni, V., Kuliçi, H. (2005) Monocracies This trend increases with the course of Car- and negative effects of the sea and river pathian tributaries of the Vistula river, and cooperation with mainland. Conference for further, with the course of this river, which sea setting, organized from the Environ- mental Ministry of Albania, July 2005 drains susceptible to erosion flysch areas, Hoxhaj, J., Hysenaj, R., Bojaxhiu, M., Abazi, S., areas covered by loess deposits, moraines Kuliçi, H. (2005) The Albanian river net and fluvioglacial deposits. As a result, in the and assessment of their basins. In Delft, lower course of the Vistula river (central The Netherland for 8th International, Con- and northern Poland) transport of bottom ference on Fluvial Sedimentology, August 7-12. material considerably exceeds transport of Hoxhaj, J., Hysenaj, R., Gjoni, V., Kuliçi, H., suspended material. Leka, P. The influence of the geological The results of investigations complete the condit ions in environmental dynamic of gap in the knowledge of the relations be- Adriatic river basins.. 5th European con- tween the transport of bottom material and gress on regional geoscientific cartography ad Earth Information and wate system, suspended material in the whole course of in Barcelona, Spanje the Vistula river and its Carpathian tributar- Hoxhaj, J., Kuliçi, H. Quaternary depositions ies. The suspended material represents over along the geological structure of the 95% of clastic material transported in the Albanides. Fourth International Conference upper sections of Carpathian rivers, about on the Geology of the Tethys (17-24 No- vember, 2008, Cairo University). 90% in the middle sections, about 70% in the Vistula at the Carpathian foreland, 50% in the middle section of the Vistula, and 46 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 about 25% in the lower section of this river. the grains into bed morphological features. These proportions between the transport of The tracers were inserted in the upstream bottom material and suspended material are section of the reach, in both bars and local different than the generally accepted model scour pools after the debris flow in 2005. of fluvial transport in the longitudinal pro- They were tracked in 2006 and 2008. file of a large river draining mountain, up- The results show that three years after the land and lowland areas. debris flow, preferred deposition areas were located along the margins of the channel. Sediment movements are limited considering CHANNEL BED ADJUSTMENTS that the slope of the channel could have ini- FOLLOWING A MAJOR DEBRIS FLOW IN A tiated, by itself, gravitational movements. MOUNTAIN STREAM Average displacements are short (12 m) and Hélène Lamarre,1 Geneviève Marquis,1 André G. decrease with an increase in median grain Roy,1 Thomas Buffin-Bélanger,2 Jay Lacey,3 Bruce size until the grain size reaches 800 mm. MacVicar4 Clasts that moved longer distances are de- 1 Université de Montréal, CP 6128, Succ. Centre- posited on the channel margins, a pattern of Vi l le, Montréal, Qc, H3C 3J7. Canada deposition that fits the results obtained from helene.lamarre@umontreal.ca topographic maps. As bed elevations in- 2 Université du Québec à Rimouski, 300 Allée des crease at the insertion point, the displace- Ursulines, Rimouski, Qc, G5L 3A1. Canada. ment distances are longer, suggesting that 3 Wageningen University, PO Box 9101, 6700 HB, clasts initially located on bars are more Wageningen, The Netherlands. mobile. This is not surprising considering 4 University of Waterloo, 200 University Avenue their lack of imbrication and their exposition West, Ont, N2L 3G1, Canada. to the flow after the flood. The stability ob- served in the reach suggests that the avail- In the absence of consensus on a bedload ability of sediment is limited, thus insuffi- sediment transport conceptual model and cient to observe bed sediment reorganization predictive equations in mountain streams, into structured morphological features on a particles tagging may appear an obvious short time-scale. approach to determine transport rates and grain displacement lengths. It gives unique information on the processes involved in sed- FLOW VELOCITY FIELDS OVER A 15-KM iment transfer within the channel. This study LONG DUNEBED IN THE LOWER presents a unique dataset on sediment trans- MISSISSIPPI RIVER DURING SPRING HIGH port in a mountain stream after a high-mag- DISCHARGES nitude flood, a rapid release of bed material, Suzanne F. Leclair1 and bed degradation. Department of Earth and Environmental Sciences, The experiment was carried out in a Tulane University, New Orleans, Louisiana, U.S.A.1 mountain stream located in the French Alps. Now a consultant geologist at Environnement Illimité., The 100-m selected reach has a slope 43%. 1453 Saint-Thimothée, Montréal, QC, Canada. Bed material is heterometric essentially com- suzanne.leclair@envill.com ing from hillslopes and travelling in the channel through gravitational and nival pro- Recent results on large-river morphody- cesses under conditions of moderate dis- namics revealed that these rivers do not be- charges. Topographic measurements were have exactly like smaller systems. Yet to this used to quantify channel bed adjustments day, data are still sparse on bedform and flow over a three-year period following a debris dynamics of large rivers. Surveys were con- flow event. We also used passive integrated ducted over a 15-km long line in a stretch of transponders inserted into clasts to track the Mississippi River, which comprises a particles and follow the reorganization of straight reach and a meander bend located at Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 47 about 370-385 km from the river mouth. This paper reports data from three surveys NORTH ATLANTIC TRIASSIC RIFT BASIN conducted during the falling limb of one of FILLS: CONTROLS ON THE EVOLUTION the Spring hydrograph peaks, when dis- FROM FLUVIAL TO PLAYA STAGE charge decreased from 22,750 m3/s, to Sophie Leleu, Adrian J. Hartley 17,900 m3/s, to 13 470 m3/s (respectively University of Aberdeen, King’s College, Aberdeen, 1.7, 1.3, and 0.98 of mean annual discharge Scotland – UK; email: sophie.leleu@abdn.ac.uk at the closest upstream river gage station). Bed elevation was measured with a 1 MHz, The continental deposits of Triassic rift single, narrow (1.7°) beam transducer and a basins developed along the Central and high-resolution echosounder coupled with a North Atlantic margins display a similar DGPS and a motion-sensor compensating for sedimentological evolution. Classically, two roll, pitch and heave. A RDI 1200 kHz phases of sedimentation can be recognised: ADCP was installed on the same mount as 1) a lower sand-prone phase characterised the other instruments, providing data for es- by fluvial deposits including alluvial fan and timating sediment transport parameters. fluvio-aeolian deposits and 2) an upper fine- Results show that the largest dunes are grained phase which is a mud-prone unit not systematically observed in the deepest and may include evaporites which record part of the channel. The straight reach is deposition in playa/ lacustrine dominated shallower and often covered with larger environments. Triassic basins that display dunes than the bend scour. ADCP 2-D results this sedimentological evolution include those show that although large dunes (up to 4-5 m of the UK, Ireland, Portugal, Morocco and high) affect the entire column of the flow North America. Although the sedimentologi- over their migrating path, there are channel- cal evolution of these basins is similar, the scale flow structures -alternate faster or timing and duration of the phases of fluvial slower flow-velocity zones that may affect and playa deposition vary from one to an- their development. Signal intensity from the other. Characterising the transition between instruments show ejections over dune crests the fluvial and playa dominated episodes of and related spatial variability of the flow basin development is important in terms of velocity field. understanding what the controls are on this The present study is embedded in a re- widespread architectural signal within Trias- search that aims at linking morphodynamic sic continental basins. to stratigraphic models (e.g. Paola & Borg- This work presents a section from the man, 1991; Leclair & Bridge, 2001), and Minas Sub-Basin (Fundy Basin, Nova Scotia) hence at improving our understanding of where the transition from the fluvial to the modern systems as well as ancient fluvial playa/ lacustrine stage is exposed. The fluvi- records. al phase is represented by the Wolfville For- mation beneath the lacustrine/playa phase of References the Blomidon Formation. The Wolfville For- mation presents three fluvial units which Leclair, S.F. and Bridge, J.S. (2001) Quantita- show well organized and repetitive cycles tive interpretation of sedimentary struc- developed at different scales. In the upper tures formed by river dunes. J. Sedim. part of the succession an increase in ephem- Res., 71, 713-716. Paola, C. and Borgman, L. (1991) Reconstruct- eral fluvial/playa-lacustrine deposits and ing random topography from preserved preservation of aeolian sediments prior to stratification. Sedimentology, 38, 553-565. playa deposition of the Blomidon Formation is present. Overall the Wolfville Formation records retrogradation of a fluvial system within which cycles are considered to be cli- matically driven. Despite a possible climatic 48 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 control on the retrogradation of the sedi- began at Qingtongxia reservoir and then mentary succession, the diachronous nature gradually developed downstream to the of the transition in different north Atlantic reach below Sanhuhekou cross-section. basins suggests that additional controls are Since the joint operation of Longyangxia, important in defining continental Triassic Qingtongxia and Liujiaxia reservoirs in Atlantic basin evolution, such as drainage 1986, the three-stage change trend has be- basin evolution or fault array development come less evident than that in the time peri- related to internal rift basin re-organisation. od between 1969 and 1986 when only Qing- tongxia and Liujiaxia reservoirs were put into operation alone. In addition, since CHANNEL CROSS-PROFILE CHANGE AT 1987, the extent of lateral migration and TOUDAOGUAI STATION AND ITS talweg elevation change at Toudaoguai RESPONSE TO THE OPERATION OF cross-section has reduced dramatically, UPSTREAM RESERVOIRS IN THE UPPER cross-sectional profile and location tended to YELLOW RIVER be stable, which is beneficial to the normal Lishan Ran,1, 2 Suiji Wang,1 Xiaoli Fan1, 2 living for local people. 1 Key Laboratory of Water Cycle and Related Land Key words: cross-sectional profile; medi- Surface Processes, Institute of Geographical Scien- an diameter; reservoir; Toudaoguai cross- ces and Natural Resources Research, Chinese section; the upper Yellow River. Academy of Sciences, Beijing 100101, China; ranlishan@gmail.com 2 Graduate University of Chinese Academy of Scien- LATE QUATERNARY ALLUVIAL SEQUENCES ces, Beijing 100049, China. IN THE ARID PIEDMONT OF CORDILLERA FRONTAL (33º-34º S) MENDOZA, The application of dams built upstream ARGENTINA will change the input conditions, including Mehl Adriana,1 Zárate Marcelo1 water and sediment, of downstream fluvial 1 INCITAP (CONICET-UNLPam) Av. Uruguay 151, system, and destroy previous dynamic quasi- 6300 Santa Rosa, la Pampa. adrianamehl@ equilibrium reached by channel streamflow, gmail.com so indispensable adjustments are necessary for downstream channel to adapt to the new The piedmont of Cordillera Frontal, be- water and sediment supply, leading the fluvi- tween 33°-34° S, is located within the do- al system to restore its previous equilibrium main of the South American Arid Diagonal or reach a new equilibrium. Using about 50- (AD), an area climatically sensitive to the year-long hydrological, sediment and cross- Late Pleistocene-Holocene climate changes. sectional data, temporal response process of Within this setting, nearly 600 metres of Late Toudaoguai cross-section located in the up- Quaternary deposits are deposited in the per Yellow River to the operation of reser- Tunuyán tectonic basin from which only the voirs built upstream was analyzed. The re- uppermost 30 metres crop out, mainly along sults showed that the Toudaoguai cross-sec- the bankfulls of arroyo La Estacada basin tion change was influenced strongly by the and its tributary arroyo Anchayuyo. The ex- operation of upstream reservoirs and down- posed deposits, including four main facies stream channel armoring thereafter occurred and two facies associations, make up three gradually and extended to the reach below geomorphological units, an aggradational Sanhuhekou cross-section. Besides, median plain (Late Pleistocene- Early Holocene), a diameter of suspended sediment load experi- cut and fill terrace (Middle to Late Ho- enced a three-stage change that was charac- locene) and the present floodplain environ- terized by an increase at first, then a de- ment (last 400 yrs. BP). Facies A represents crease and an increase again finally, which channel deposits, it includes lag deposits reflects the process of channel armoring that (lithofacies Gmm) and channel bars (lithofa- Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 49 cies Gh). Its participation in the alluvial se- quences is secondary, being present at the RESERVOIR ARCHITECTURE MODELING OF lower stratigraphic section of both the FLUVIAL POINT BARS: LORANCA BASIN, aggradational plain and the cut and fill ter- SPAIN race. Facies D is composed of stacked layers L.A. Meijer, K.A. van Toorenenburg, M.E. Donselaar (0.4 to 2.5 m) of medium to fine sand and Dept. of Geotechnology, Delft University of Technology, silty sand (lithofacies Sm, Sr y Src) making P.O. Box 5048, 2600 GA Delft, The Netherlands. up several meter high sets. It is best repre- sented at the aggradational plain, suggesting Hydrocarbon and water recovery in fluvi- an overbank environment affected by hyper- al sandstone reservoirs are complex due to concentrated overflows proximal to the main low net-to-gross ratios and internal litholog- stream. Facies E includes horizontal layers of ical and permeability heterogeneity. Model- sandy silts laterally continuous (lithofacies ing of subsurface fluvial architecture is ham- Fl and Fsm), as well as lithofacies Sm. Fa- pered by the sparse data of wide-spaced cies E, which represents overflows reaching wells and therefore has an inherent uncer- distal sectors of the floodplain, is the domi- tainty. Outcrop analogue studies with focus nant facies at the cut and fill terrace and sec- on the size, shape and spatial distribution of ondarily at the aggradational plain. Over- the fluvial elements and their internal perme- bank areas (Facies E and D) register several ability distribution may yield the quantita- alluvial buried soils (lithofacies Pa) that rep- tive data sets needed to reduce the modeling resent intervals of stability during the aggra- uncertainty. dation process; limnic levels (lithofacies c) The aim of the present study is to gain a are also present, being very common in the better insight in the complex reservoir archi- cut and fill terrace deposits. The aggrada- tecture of fluvial point-bar sandstones and its tional plain and the cut and fill terrace units implications for fluid flow. To this end three- are covered by a blanket of eolian sand dimensional static grain size and permeabil- (lithofacies Sme) that set up Facies J. Mas- ity models were created, based on an outcrop sive silty fine sands (circa 1 meter thick) of study of composite point bars in the distal eolian origin accumulated by the end the area of the Tórtola fluvial system in the Lo- Late Glacial are also present at the lower ranca Basin (U. Oligocene – L. Miocene, stratigraphic section of the aggradational central Spain). Lithofacies characteristics of plain. the outcrops were compared with earlier-re- The facies association (Facies A, D and J) corded outcrop permeability measurements. of the aggradational plain is interpreted as a Qualitative microscopic sample analysis was distal alluvial fan dominated by overflows carried out to study the relation between per- and secondarily sinuous streams. The cut meability values and diagenetic processes. and fill terrace facies association (Facies A, E The study yielded that the composite and J) corresponds to a fining upward se- point bars consist of various units of fining quence of a sinuous to meandering stream. up sequences of sandstone and siltstone Preliminary results obtained point to a cli- beds. The point-bar architecture and associ- matic control of the degradation episodes ated grain-size distributions were created by that gave way to the formation of the cut lateral migration of a meandering river and and fill terrace and the present floodplain, vertical stacking of its deposits. Gradual sometimes during the Middle and the Late aggradational phases were interrupted by Holocene respectively. abrupt channel migration, meander loop cutoff and channel fill. Subsequent aggrada- tion partly eroded such channel fills to vary- ing extents. Finer grained and/or better ce- mented point-bar sections do not compart- mentalize the studied composite point-bar 50 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 sediment bodies but form baffles to flow. imentation style of the main active channel These baffles do not compromise fluid flow of the Pilocomayo ?uvial fan covering over completely, but force it to follow a tortuous 210000 km2, has been studied using high- pathway. Late-diagenetic dissolution of gyp- resolution satellite images and detailed sum grains as a result of uplift and subse- DEM. A detailed geomorphological analysis quent surface water percolation has largely of the downstream channel evolution from increased the permeability. apex to toe (ca. 680 km), indicates a strong Hydrocarbon recovery from subsurface variability of channel pattern, type of inci- reservoirs may be less than expected from sion, occurrence of levees and aggrading reservoir dimensions only, due to the occur- and distribution of flood plains. Specifically, rence of permeability baffles that force hy- the latter associated with high sinuosity drocarbons to follow a tortuous flow path. channels occurs in the upper third of the fan, The studied point-bar outcrop can serve a fluvial style that is commonly considered as an analog for fluvial point bar reservoirs to be associated with the lower gradients and can thus enhance 3-D reservoir architec- occurring at the toe of the fan. In this case, ture modeling of these structures. the unexpected changes in channel patterns occur in correspondence of the active fore- bulge which most likely caused a decrease in VARIABILITY OF CHANNEL MORPHOLOGY gradient inducing the generation of a ‘mini OF LARGE FLUVIAL FAN SYSTEMS IN ponded basin’ in the upstream direction. ACTIVE FORELAND TECTONIC SETTINGS: Ultimately, this study highlights that the VARIABILITY OF CHANNEL MORPHOLOGY fluvial pattern of the Pilcomayo fluvial fan OF LARGE FLUVIAL FAN SYSTEMS IN does not follow the classic proximal-to-distal ACTIVE FORELAND TECTONIC SETTINGS: channel style schemes commonly described IMPACT ON RESERVOIR ARCHITECTURE and accepted in the literature for fluvial sys- AND CONNECTIVITY tems. Grain-size distribution, facies, facies Andrea Moscariello, Chris Bugg, Niels Hovius associations, sand body geometry, internal Delft University of Technology. a.moscariello@tudelft.nl architecture and sand connectivity are in- stead dependent on local external factors Large fluvial fans accumulations result- such as, in this case, the tectonic evolution of ing from dispersive sediment deposition gen- the deeply seated forebulge underneath the erally from a single main individual river fluvial fan accumulation. stream, represent ideal natural laboratories to observe and describe the variability of flu- vial channel morphology and assess the ef- THE FLOODPLAIN SEDIMENTOLOGY OF fects that external factors such as i.e. tecton- COOPER CREEK. WHY BILLABONGS ic, preexisting topography, relative base level (WATERHOLES) IN THE CHANNEL changes, etc., can have on channel down- COUNTRY START AND STOP stream evolution. Gerald C. Nanson, Josh R. Larsen, Dioni I. Cendon, In the South American Andean foreland Simon D. Fagan, Brian G Jones region, where contiguous fans occupy an University of Wollongong. area up to 750000 km2, it is not uncommon to observe coeval development of different The Channel Country of western Queen- types of channel style (e.g. Paranetí, Piloco- sland consists of a low gradient anastomos- mayo fans). This can be related to a variety ing channels inset in muddy floodplains in a of reasons such as range of different deposi- desert climate. Annual transmission losses tional processes, downstream and lateral are large, averaging 75-80% of total volume changes in slope and channel con?guration, along a ~400 km reach of Cooper Creek. variability of sediment source, etc. Billabongs (waterholes) are common and As an example, the morphology and sed- consist of local channel expansions in the Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 51 mud-lined anastomosing network, as well as in the absence of sediment load. Using isolated scour-channels on a floodplain that Rhodes ternary diagram, comparisons are is formed of 2-3m of clay-rich mud. Both made with hydraulic geometry data from the primary anabranching and overbank self-forming channels carrying bedload in flood channels carry water during large alluvial settings elsewhere. Despite con- floods but only the billabongs store water straints on channel depths caused at some for long periods of drought, making them locations by the restricted depth of peat, vital to the ecology and agriculture of the most stations have cohesive, near-vertical, region. Despite penetrating a very extensive well-vegetated banks and optimal w/d ratios underlying Pleistocene-age sand body, they of ~2. Because both depth and width are to are impermeable much of the time. However, some extent constrained, adjustments to dis- transects away from several billabongs re- charge are accommodated largely by chang- veal marked increases in salinity and pro- es in velocity. These findings for the move- vide compelling evidence that they act as ment of sediment free water are consistent fresh-water ‘entry valves’ through an other- with the model of maximum flow efficiency wise impermeable muddy floodplain. The and the overarching least action principle in base of each billabong is scoured during open channels. Importantly, the depth of floods, enabling large volumes of surface peat in these swamps rarely exceeds that re- water to be dumped into the 10 m deep sa- quired to form a bankfull channel of opti- line aquifer. As flows decline the billabongs mum w/d ratio. The bankfull depth of freely self-seal with mud such that fresh water can adjusting laterally-active channels in clastic be stored for a year or more. Transmission alluvium is well known to be related to the losses along Cooper Creek were initially be- thickness of floodplain alluvium. A similar lieved to be due to evaporation, however, condition appears to apply to these swamps the lack of any solute concentration between that grow in situ and are formed almost en- gauging stations along the ~400 study tirely of organic matter. Swamp vegetation reach, suggests that of the ~1.8 km3 of sur- is highly dependent on proximity to the wa- face flow lost from the ~3.0 km3 entering tertable. To maintain a swamp-channel and the upper end of the study reach, most leaks floodplain system, the channels need to flow through the base of the billabongs. Such with abundant water much of the time; they massive losses also account for why the bill- not only offer an efficient morphology for abongs in the form of large and efficient flow but do so in a way that enables bankfull channels, terminate after just a few kilome- conditions to occur many times a year. They tres. They reform repeatedly at locations also prevent the swamp from growing above where conditions are suitable, but their num- a level linked to the depth of the channel. bers decline downstream in accordance with Once the channel attains the most efficent the loss of total flow-volume. cross-section, further growth of the swamp vertically is restricted by enhanced flow ve- locities and limited flow depths: the volume HYDRAULIC GEOMETRY OF NARROW of peat in such swamps is determined by the DEEP CHANNELS IN PEATLAND hydraulic efficiency of their self-forming FLOODPLAINS; EVIDENCE FOR channels. The development and maintenance OPTIMISATION of the hydraulic geometry of these swamp Gerald Nanson, Rachel A. Nanson, He Qing Huang channels is bio-geomorphic and bio-hydrau- University of Wollongong. lic in nature and yet accords to the same optimising principles that govern the forma- At-a-station and bankfull hydraulic ge- tion of self-adjusting channels and flood- ometry analyses of peatland channels at Bar- plains in clastic alluvium. rington Tops, New South Wales, Australia, reveal adjustments in self-forming channels 52 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 data were manipulated using the ILWIS soft- FLOOD RISK ON FLUVIAL MARGINS AND ware and the hydrological and flood risk URBAN AREAS. TUCUMÁN. ARGENTINA and soil use cartography were obtained Neder, Liliana del Valle,1 Busnelli, José1, 2 through this GIS. North-South and West-East 1 INGEMA (Instituto de Geociencias y Medio Ambien- cross sections were mapped using GPS. te), Facultad de Ciencias Naturales e IML. UNT. Flood areas, due to rain excess on the Miguel Lillo 205. Tel. 0381 4239456. Fax 0381 Gran San Miguel de Tucumán, are located a 4330633. 4000. Tucumán. few meters from the North and West-South 2 CONICET, Consejo de Investigaciones Científicas y collector channels, which were affected by Técnicas. flood processes during the extreme rains, ananeder@yahoo.com.ar; jose.busnelli@gmail.com such as the ones occurred in January of 2007 and 2008. San Miguel de Tucumán city, capital of the Province of Tucumán, belongs to the sub- tropical Northwestern region of Argentina. MAIN CONTROLS ON THE EVOLUTION OF The city is located on the eastern foothill of DISTAL VOLCANICLASTIC SUCCESSIONS IN San Javier range towards a north-south river, CONTINENTAL ENVIRONMENTS: CASTILLO Salí River, which is the main fluvial collec- FORMATION (ALBIAN) OF THE GOLFO SAN tor of the province. The urban growth since JORGE BASIN, ARGENTINA 1950 was accelerated yielding an urban ag- José Matildo Paredes,1 Nicolás Foix,1,2 José Oscar glomerate joining several nearby towns and Allard,1 Ferrán Colombo3 represents a metropolitan area that settled 1 Universidad Nacional de la Patagonia San Juan almost the entire foothill from the apical to Bosco, Ruta Provincial nº 1 s/n, Km. 4 (9005) distal zones. Comododo Rivadavia, Chubut, Argent ina. The Salí River, which is the main source paredesj@unpata.edu.ar of fresh water and irrigation supplying, splits 2 CONICET (Consejo de Investigaciones Científicas y two districts, one is the San Miguel de Tu- Técnicas). cumán city westwardly and the other is Ban- 3 Dpto. de Estratigrafía, Paleontología y Geociencias da del Río Salí eastwardly, where a great Marinas, Facultad de Geología, Universidad de urban expansion took place on the river Barcelona. (08028) Barcelona, España. flood plain, through poor neighbourhoods and illegal settlements for low income peo- Volcaniclastic successions in distal posi- ple. tions in relation to the source of pyroclastic The aims of the current research focus on detritus are controlled by the interplay establishing flood risk categories on the flu- among intermittent-variable volume of fine vial margins of the Salí River, mainly on the ash transported by atmospheric winds during urban areas affected by channel overflowing syn-eruptive stages, contemporary subsidence under extraordinary pluvial conditions, mod- of the basin and superficial processes of re- eling the water level onto the urban sectors. working of ash and sediments during inter- The lack of territorial planning, multiannual eruptive stages. Those controls were evaluat- climatic variations, intraurban paleochannel ed in the Castillo Formation (Albian) in the (masked by urbanization), insufficient col- N-S trending San Bernardo Fold Belt, located lecting draining without preservation and 170-190 km eastward of the source of pyro- the increasing impermeable and paved areas clastic detritus, the Andean Volcanic Chain. with high rates of runoff over infiltration, The unit represents the reworking of pyroclas- have contributed that some zones were more tic ash-fall beds in fluvial, playa-lake and affected by periodic floodings. lacustrine environments, and can be divided The applied methodology was based on in sixteen lithofacies, grouped in three litho- aerial photointerpretation, satellite images facies associations: 1) fluvial channel, with analysis and topographic maps. The yielded five sub-types, 2) proximal floodplain and 3) Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 53 distal floodplain. Four major Regions with 3 Durham University, UK. distinctive features of the fluvial deposits 4 CECOAL, CONICET, Arg. were recognized, named Regions 1 to 4. At 5 University of Guelph. basin margin locations (e.g. Region 1) the unit is a 30m thick succession of deeply bio- Bifurcations around mid-channel bars turbated ash-fall strata, which records by- are key elements within braided river passing and condensation of the sedimentary sytems, having a major impact upon the record in a subaerial floodplain. In areas routing of flow and sediment, upon channel proximal to the northern basin margin (e.g. change and bar sedimentology. Although Region 2) the unit is less than 300m thick, it much progress has been made in under- consists of small-scale, massive sandbodies standing a range of fluvial processes, in- and sheetflow (or flash-flood) deposits en- creasing attention is being paid to bifurca- cased in a subaerial or subaqueous flood- tions and the important role of bifurcation plain. The fluvial system evidences a poorly asymmetry and flow and sediment routing at integrated network of channels and large these sites. Most studies have been conduct- variation in discharge. In southern areas ed in laboratory flumes or within small riv- (e.g. Region 3) the unit is 300-500m thick ers with low width:depth (aspect) ratios. and consists of thicker fluvial channels and This paper presents results of a field-based floodplain deposits. Fluvial channels show study that details the bed morphology and alternation of massive, plane-parallel and 3D flow structure around two large bifurca- straight to low-sinuosity sandbodies, reflect- tions in the Río Paraná, Argentina, with a ing a highly variable fluvial dynamic. In ar- width:depth ratio of approaching 200. Flow eas of high-subsidence, at southern San Ber- within both bifurcations is dominated large- nardo Fold Belt (e.g. Region 4), the unit is ~ ly by the bed roughness, in the form of sand 1000m thick. Fluvial channels are straight dunes; coherent, channel-scale, secondary to low-sinuosity, mostly single or multi-sto- flow cells, that have been identified as im- rey, being part of a well-integrated drainage portant aspects of the flow field within network in which large variations in dis- smaller channels, and assumed to be present charge are evidenced by plane-laminated within large rivers, are found to be generally sandbodies with W/Th>100. Spatial chang- absent in these reaches. This paper discusses es in thickness, scale and proportion of dif- these findings and outlines how this has pro- ferent fluvial channels of the Castillo Fm. found implications for flow mixing rates, suggest that in spite of the widely recognized sediment transport rates and pathways, and control of volcanism on the characteristics of thus the interpretation of large river mor- volcaniclastic deposits, the reworking of ash- phology and sedimentology. fall deposits in large basins located in a dis- tal position to the source of volcaniclastics are mainly controlled by intrabasinal pro- COHERENT FLOW STRUCTURES OVER cesses. ALLUVIAL SAND DUNES REVEALED BY MULTIBEAM ECHO SOUNDING Daniel R. Parsons,1 J. L Best,2 S. M Simmons,1 G. MORPHOLOGY, FORM ROUGHNESS AND M Keevil,1 K. Oberg,3 J. Czuba3 THE ABSENCE OF CHANNEL SCALE 1 University of Leeds, UK; d.parsons@see.leeds. SECONDARY FLOWS AT BIFURCATIONS IN ac.uk A LARGE RIVER 2 University of Illinois, USA. Daniel R. Parsons,1 J. L. Best,2 S. N. Lane,3 R. J. 3 USGS, Illinois, USA. Hardy,3 O. Orfeo,4 R. Kostaschuk5 1 University of Leeds, UK; d.parsons@see.leeds. The topology, magnitude and sediment ac.uk transport capabilities of large-scale turbu- 2 University of Illinois, USA, lence generated over alluvial sand dunes is 54 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 influential in creating and maintaining dune morphology, and in dominating the transport FLOOD DOMINATED FAN DELTA – CASE of suspended sediment above dune beds. STUDY FROM EASTERN SLOVAKIA Much past laboratory and numerical re- (MARKUÒOVCE) search has illustrated the origin and struc- Marta Prekopová, Juraj Janoèko ture of such dune-related macro turbulence, Institute of Geosciences, Technical University of and this turbulence has also been measured KoÓice, Letná 9, 04001 Slovakia. using both at-a-point and multipoint (aDcp) marta.prekopova@tuke.sk, juraj.janocko@tuke.sk measurements within natural channels. However, all of these past field techniques Inner Carpathian Paleogene Basin, situat- have been unable to examine the holistic ed in the western part of the Carpathian structure of such turbulence and examine Mts., has almost 2 km thick sedimentary fill how this may related to smaller-scale labo- consisting of terrestrial, shallow-marine and ratory studies and numerical simulations. deep-marine deposits. Several ancient in- This paper examines the novel application of cised valleys with well-exposed fluvial depos- multibeam echo sounding (MBES) to exam- its occur along the southern margin of the ine flow and sediment flux above a series of basin. sand dunes in the Mississippi and Missouri Unique exposures along the southern rivers, USA. A RESON 7125 MBES system margin of the basin in the Eastern Slovakia was deployed from a small survey boat and (Markušovce area) show transition between used to map the detailed three-dimensional fluvial deposits and wave-reworked fan-del- topography of sand dunes. Once this bathy- taic deposits. The common feature of both metric surveying had been completed, the systems is a prevalence of coarse-grained boat was then moored at-a-point and the conglomerates alternating with sandstone MBES head aligned so that is captured a facies suggesting dominancy of flooding dur- flow parallel swath. The backscatter signal ing the deposition. from the multibeam swath was then utilized Terrestrial fluvial deposits are represent- to visualize the structure of turbulence as ed by channel fill complex consisting of con- picked out by the clouds of suspended sedi- glomerates filling shallow and broad chan- ment. Image sequences were taken in the nels alternating with flood plain fine-grained trough and near the crests of a large sand and silty deposits. A striking feature of the dune and reveal the presence and advection channel complex is several metres thick in- of large coherent flow structures, with su- terval of clast-supported cobbles and boul- perimposed smaller vortices, that translate ders arranged in several dm shallow and few through the measurement volume. These metres wide channels interpreted as debris images are the first such whole flow field flow deposits. These are thought to be depos- visualizations of dune-related macroturbu- ited by catastrophic floods transporting the lence ever collected from a natural alluvial sediments from distant source areas as sug- channel and reveal a complex flow structure, gested by their petrographical composition. which bears many similarities to that mod- Debris flow facies are at several places inter- elled in past laboratory and numerical exper- bedded by laterally pinching carbonate con- iments. This paper will present images and glomerates representing the entry of alluvial animations of the flow structure and com- fans into the river paleovalley. pare this to past modeling of coherent vor- Fan-deltaic and shallow-water sediments ticity within both smooth and dune-covered are characteristic by conglomerates alternat- beds. ing with fine-grained sandstones with varied internal structures (horizontal lamination, through-cross stratification). Hummocky cross stratification is also observed occasion- ally and is probably a result of the increas- Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 55 ing oscillatory component when unidirec- monly believed. Most unit bars are internally tional current enter the shallow water composed of down-climbing stratasets (shelf). Remarkable is thin layer of coarse- formed by dunes migrating down low-angle, grained subrounded and rounded paleozoic unit-bar lee slopes. Hence, channel deposits cobbles and boulders transported from a dis- are dominated by angle-of-repose cross strata tant source area and probably representing formed by dunes. lateral subaquous analog of thick interval described from the fluvial part of the system. Fan deltaic deposits were wave-reworked DOES LARGE-SCALE ALLUVIAL as suggested by through cross stratification, MORPHOLOGY CONTROL DUNE-SET ripple cross stratifications, thin conglomer- PRESERVATION? ate beds alternating with sandstones and by Reesink, A.J.H.,1, 2 Ashworth, P.J.,1 Amsler, M.L.,3 bioturbated sandstones. The entire vertical Best, J.L.,4 Hardy, R.J.,5 Lane, S.N.,5 Nicholas, succession is capped by notable large-scale A.P.,6 Orfeo, O.,7 Parsons, D.R.,8 Sambrook Smith, through-cross stratified and horizontally lam- G.H.,2 Sandbach, S.D.,5, 6 and Szupiany, R.N.3 inated sandstone with sharp base (know as 1 SET, University of Brighton, UK, emai l : „Markušovce mushroom”), representing the a.j.h.reesink@brighton.ac.uk. fan deltaic deposit reworked by waves in 2 GEES, University of Birmingham, Birmingham, UK. shallow water environment. 3 Universidad Nacional del Litoral, Santa Fe, Argen- tina. 4 University of Illinois, Urbana-Champaign, IL, USA. DISTINGUISHING CROSS STRATA FORMED 5 University of Durham, UK. BY DUNES AND UNIT BARS 6 University of Exeter, UK. Arnold J.H. Reesink,1, 2 John, S. Bridge3 7 Centro de Ecologia Aplicada del Litoral, Corrientes, 1 SET, University of Brighton, Brighton, UK. Argentina. 2 GEES, University of Birmingham, Birmingham, UK; 8 School of Earth and Environment, University of email a.j.h.reesink@brighton.ac.uk; Department of Leeds, UK. Geology, Binghamton University, NY, USA. The thickness distributions of cross-strata The stratification formed by fluvial unit sets underlie paleo-hydraulic interpretations bars can be readily distinguished from that and predictions of permeability heterogene- formed by dunes when observed in extensive ity. Previous work on the proportion of a bed- 2-D exposures. However, angle-of-repose form that is preserved as a set stresses the cross strata can occur in both unit bars and importance of the variation in bedform dunes, and it is difficult to distinguish them height and the deposition rate relative to the in small outcrops and cores. Angle-of-repose migration rate. Although no real consensus cross strata formed by unit bars can be dis- exists on the relative importance of the fac- tinguished in cores by the presence of rela- tors controlling set preservation, it is gener- tively thick and fine-grained bottomsets, ally accepted that sets scale to their forma- and, to a certain extent, by the relatively tive bedforms, and that both follow log-nor- large set thickness. Additional information mal distributions. This paper compares the can be obtained from the cross strata them- thicknesses distributions of cross-strata sets selves. These criteria are required for correct with ground-penetrating radar (GPR) sur- interpretation of channel deposits and for veys. Cross stratatified sets are classified into parameterization of hydrological or reser- three groups based on radar facies, and voir models. Cores through two modern these three groups are interpreted as: near- channel belts indicate that only 1-3% of the horizontal dune sets, inclined dune sets, and channel deposits are composed of angle-of- angle-of-repose unit-bar sets. repose cross strata formed by angle-of-re- The distributions of medium- and large- pose unit bars, which is much less than com- scale set thicknesses were measured from 28, 56 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 ~4 m long suction-cores taken in mid-chan- mán. Consejo Nacional de Investigaciones Científi- nel bars in the Paraná River, Argentina, and cas y Técnicas, CONICET. 36 ~ 3m long cores taken in the South 3 YPF SA, Unidad Económica Mendoza, Saskatchewan River, Canada. Results show jgsanaguam@ypf.com that the total distribution of thicknesses of sets formed by dunes and bars does not fol- The sedimentary record along the mar- low a log-normal distribution. Instead, the gins of Senguerr River shows fluvial and vol- total distribution is better described by three caniclastic deposits belong to Castillo and separate log-normal distributions: [1] dune Bajo Barreal Formations (Chubut Group, Les- sets associated with near-horizontal (<4 º ) ta, 1968; in Uliana and Legarreta, 1999). GPR reflections, formed by dunes on near- These outcrops form an asymmetrical anti- horizontal surfaces, and; [2] dune sets asso- cline in the southern end of the San Bernardo ciated with inclined (>4º) GPR reflections, Range. The plunge of this fold continues to formed by dunes on slopes; [3] unit-bar sets, the south in the subsurface. identified by their large lateral extent, large The field work consisted in the descrip- thickness compared to bankfull levels, and tion of three stratigraphic profiles (818m of association with fine-grained bottomsets. No thickness) and twenty short lateral profiles, clear relationship was found between set and the drawing of each sandstone bodies thickness and vertical position in the deposit. from a color photomosaic (Wizevich, 1991), Dune sets associated with inclined GPR re- which covered all the outcrop, 4km of flections [2] are 2-2.5 times thicker on aver- length and 60 to 100m of height. age than dune sets associated with near-hor- The major stratigraphic profiles were izontal surfaces [1]. This increase in set used in the facies analysis, stratigraphic cor- thickness can be explained by increased pres- relation and to record the vertical distribu- ervation of sets on slopes, which is attributed tion of sandstone, mudstone and volcaniclas- to the decrease in migration rate, height and tic deposits. The photomosaic allowed to length of dunes migrating down large-scale identify thirty eight channel belts; the de- lee slopes, and the locally increased deposi- scriptions of additional short lateral profiles tion rates caused by flow expansion over the permitted the quantitative reconstructions of lee slope. Inclined dune sets made up 10- five channel belts. 20% of the investigated river channel depos- The width of all sandstone bodies varies its which equals roughly 40% of all dune from 12m to 523m but the average width for sets. It is therefore suggested here that large- Castillo Formation is 127m and only 73m for scale alluvial morphology forms a dominant the Bajo Barreal Formation because the mar- control on the preservation of dune sets. gins of these sandstone bodies are eroded or covered. The thickness of sandstone bodies is high- STRATIGRAPHY AND FLUVIAL er for Castillo Formation than Bajo Barreal ARCHITECTURE OF THE CASTILLO AND Formation: 3m and 2.15, respectively. BAJO BARREAL FORMATIONS The paleocurrent directions were mea- (CRETACEOUS) IN THE SOUTHERN END OF sured in the trough cross strata and in the SAN BERNARDO RANGE AND BARRANCA imbricated pebbles. The average paleocur- YANKOWSKI, GOLFO SAN JORGE BASIN, rent direction for Castillo Formation is to- CHUBUT AND SANTA CRUZ PROVINCES, ward N148º but ranging from N60º to 210º ARGENTINA and the sinuosity is 1.35. Bajo Barreal For- Guillermo A. Richter,1 Sergio M. Georgieff,2 Javier mation shows a mean paleocurrent direction G. Sanagua3 toward N107º, varying from N0º to N180º 1 Minera Aguilar SA, Jujuy, Argentina. and the sinuosity is 1.57. 2 IESGLO, Fac. Ciencias Naturales e IML, UNT. Mi- The sinuosity and average thickness of guel Lillo 205, T4000JFE - San Miguel de Tucu- sandstone bodies in Castillo Formation indi- Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 57 cate low lateral migration and deep chan- high-resolution images of seed particles nels; while Bajo Barreal Formation shows within the flow. This experimental configu- higher sinuosity and shallower channel belts. ration will be described to demonstrate the A stratigraphic correlation between the great potential of the technique for studying outcrops and the near Barranca Yankowski flow within porous beds. oil field was performed by using seismic The experimental investigation presented lines. Due to the paleocurrent directions is herein details experiments in a laboratory possible to correlate channel belts between flume in which spheres were used, in a sim- outcrops and wells. The correlation indicates ple geometrical packing, to simulate a po- a control in the direction of the channel rous natural gravel river bed. The boundary belts, which is assumed as a syntectonic con- conditions of flow depth and mean flow ve- trol. locity were varied to examine the changing flow fields within the first four pore spaces. Additionally, the impact of the bed topogra- QUANTIFYING THE DYNAMICS OF FLOW phy, in the form of a simple particle cluster, WITHIN A PERMEABLE GRAVEL BED was also examined to detail its effect on the USING HIGH-RESOLUTION ENDOSCOPIC local subsurface flow. This paper will PARTICLE IMAGING VELOCIMETRY (PIV) present details of the instantaneous and G.H. Sambrook Smith, G. Blois, J. L. Best, R. J. time-averaged flow fields within a represen- Hardy, J. R. Lead tative pore volume that quantify the complex University of Birmingham, UK. nature of the interstitial flow structure. Flow within permeable river beds plays a significant role in both the channel morpho- LINKING SURFACE MORPHODYNAMICS dynamics and in important environmental AND SUBSURFACE ARCHITECTURE IN processes such as dissolved oxygen ex- BRAIDED RIVERS: NEW INSIGHTS FROM change, nutrient availability and contami- THE SOUTH SASKATCHEWAN RIVER nant transport. However, current knowledge PROJECT 1999-2009 of this critical ‘hyporheic’ zone remains G. H. Sambrook Smith, N.O. Parker, S.N. Lane, P.J. largely unquantified, principally due to the Ashworth, J.L. Best, I.A. Lunt, J.S. Bridge, C.J. technical difficulties involved in collecting Simpson, R.E. Thomas, P. Widdison velocity data within the pore spaces. Al- University of Birmingham, UK. though numerical models are being devel- oped to predict flow pathways within perme- This paper presents results from research able river beds, their validation also de- that has been quantifying the morphological mands accurate experimental data at the and sedimentological evolution of the sandy grain/pore scale. braided South Saskatchewan River, Canada, Direct investigations using quantitative over the last decade. The project has used a visualization techniques are inherently chal- novel approach that links Digital Elevation lenging due to practical difficulties in imag- Models, derived from specially-commis- ing through the opaque solid matrix of a sioned annual aerial photographs, with re- permeable bed. In the present study, a fully peat surveys of the subsurface using Ground endoscopic PIV system is described that has Penetrating Radar. By integrating the two been developed and employed to collect ve- datasets, not only can the morphological locity data on the scale of the individual evolution of the river be quantified, but the pore space. A pulsed Nd:YAG laser has been expression of this evolution in the subsurface used to fully illuminate the interstitial mea- can also be identified unambiguously. Thus, surement plane, whilst a 4Mpxl, image-in- the sedimentary architecture can be matched tensified camera, coupled with a high-sensi- explicitly with the formative bedforms. Fur- tivity rod-based borescope, allows capture of thermore, these datasets can be compared on 58 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 an annual basis to establish how the deposits complex sheets, large-scale complex ribbons have been reworked and preserved over time (about 100 m long and up to 5 m thick) and as the braidplain has evolved through bar small scale ribbons (a few tens of meters migration, avulsion and channel fill. Finally, long and up to 3 m thick). The second group the relative impact of different flood magni- includes sheets, lobes and fine grained back- tudes on sediment preservation can be as- ground sedimentation. sessed, as the study reach has experienced a Although some authors have described wide range of flows over the past decade, these deposits as hyperpicnites, the presence including a 1-in-40 year event. Highlights of of dissecation cracks is an unequivocal evi- this unique data demonstrate: 1) the impor- dence of sub-aereal exposure during the ac- tance of unit bars in both the morphological cumulation of this unit. Thus, the idea of and sedimentological evolution of the braid- subacueous deposition in a water body plain; 2) the similarity between the alluvial should be revised. In that manner, the current architecture of compound bars and channel analysis interpret the unit as a fluvial system fills, 3) that larger floods may increase the dominated by sandy bed load (channel rate of morphological evolution, but not the units), with episodic flooding events on the scale of the subsurface structures, such that alluvial plain area (non-channelized units). the deposits of large floods can be difficult to discriminate from those of smaller floods, and, 4) the deposits of older bars that have CHARACTERIZATION OF FLUVIAL been reworked provide a better geometrical GEOFORMS FROM 3D SEISMIC: analogue to the rock record than those of EXAMPLES FOR CERRO GUADAL NORTE recently formed bars that have undergone OIL FIELD, CHUBUT GROUP only limited modification. (CRETACEOUS), GOLFO SAN JORGE BASIN, ARGENTINA Agustina Santangelo,1 Leonor Ferreira,1 Sergio M. FACIES AND ARCHITECTURAL ANALYSIS Georgieff2 OF LOWER CRETACEOUS FLUVIAL 1 YPF SA, Av. Libertador 520, Km3, 9000 - Como- DEPOSITS IN WEST-CENTRAL ARGENTINA doro Rivadavia, Argentina. mlferreirap@ypf.com Pablo Nicolás Sandoval 2 IESGLO – UNT, Conicet, Miguel L i l lo 205, Centro de Investigaciones Geológicas (Universidad T4000JFE – San Miguel de Tucumán, Argentina. Nacional de La Plata – CONICET). Calle 1 Nº 644 CONICET. (B1900TAC) La Plata, Argentina – Tel./Fax: + 54 221 421 5677. sandoval@cig.museo.unlp.edu.ar The strata of the Chubut Group (Creta- ceous, Golfo San Jorge Basin, Argentina) In Agrio del Medio locality (Neuquén are mainly fluvial and lacustrine deposits. Basin) crops out the Pichi Neuquén Member The fluvial architecture and poro-permeabil- of the Rayoso Formation. This unit is 200 ity characteristics of the hydrocarbon-bear- meters thick and is conformed by continen- ing reservoirs were controlled by tectonic, tal clastic deposits of Aptian and Albian age. volcanic and volcaniclastic processes con- Sedimentological detailed logs (1:100 temporaneous to the epiclastic sedimenta- scale) were made on the oriental flank of the tion. Additionally, the connectivity of sand- Agrio Anticlinal on the right margin of the stone bodies was modified according to their Agrio river. With this data along with photo- location in relation to the faults. Hence, lat- mosaics of the area, facies were defined, bi- eral and vertical changes in the fluvial archi- dimentional panels were made, and litho- tecture are observed in different areas of the somes were identified. same oil field. Lithosome characteristics allowed distin- 230 Km2 of 3D seismic registration were guishing between channel units and non- performed in the Cerro Guadal Norte oil channelized units. The first group includes field (YPF SA) at the end of 2008. Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 59 The use of amplitude anomalies allowed from the levee and alluvial plain to evaluate us to identify several distinctive geoforms, differences in the dynamic of the sediments, such as channel belts, crevasse channels, the dominant grain size and the influence of splays or lobes. Horizon sections made pos- the pluviometric variation on the suspended sible to determine the shape of channel and solids. channel belts (wide, orientation, sinuosity In order to determinate the grain size, the and connectivity) and in vertical sections sieving and pipette techniques were used. these are interpreted by means of slight am- The graphic method was employed in the plitude anomalies as well as changes on the calculation of some textural parameters. The shape of the wavelet. Visher method was used to evaluate different The analysis of the 3D seismic informa- mechanisms of bed sediment transport (Vish- tion is a fundamental tool for the study of oil er, 1969). Sediment concentrations were cal- fields, throughout the integration of strati- culated by filtering using membrane disks graphic, sedimentologic and tectonic data, size of pores 0.45 µm. allowing the optimization on the oil wells The Salado River is characterized by high location, aiming to generate an efficient and concentration of suspended solids, linked reliable development of the field. with the low rain offer and the high develop- ment of vegetation. The grain size of bed sediments was rela- SEDIMENTOLOGICAL CHARACTERISTICS OF tively homogeneous along all the hydrologi- SUBTROPICAL PLAIN RIVERS IN RELATION cal cycle, where coarse and medium silt WITH THE HYDROLOGICAL CYCLE (CHACO, were the dominant fractions. ARGENTINA) The Tragadero River bed sediment was Carolina Sartirana, Paola A. Suárez more heterogeneous in grain size. The mean CECOAL (CONICET) – Fa.C.E. Na. (UNNE). Casilla de size is primarily within the very find sand in Correo 291 – 3400 Corrientes. the central area of river channel. The sus- carolinasartirana@gmail.com pended sediment concentration was lower than the Salado River. The concentration of The Chaco-Pampa plain is a large mor- suspended solid in both streams was in- phological unit located in the northeastern creased during the high water periods. Distri- region of Argentina. A series of local fluvial bution curves of accumulative frequencies networks were developed in the Eastern re- demonstrated that the suspension is the gion that presents two important fluvial sub- dominant mechanism of transport. systems named “Amores” and “Oro” differen- All sediment analysis reflected the partic- tiated by its genesis and morphologic evolu- ularities of the area of contribution and the tion. The studied region, including these intrinsic characteristics of the transport small rivers, presents particular characteris- agent. The results improved the available tics related to the small slope and subtropi- information about fluvial environments lo- cal climate. This contribution presents a hy- cated subtropical plains. drosedimentologic characterization of each subsystem in order to generate information about general features of the region and its SOLID LOAD DYNAMICS IN THE DON AND relation to the annual variations of the rain- KUBAN RIVERS, SOUTH RUSSIA: fall. INFLUENCE OF ANTHROPOGENIC AND One river from each subsystem was se- CLIMATE FACTORS lected: Salado River (from Amores sub- Vera Sorokina,1 Sergey Venevsky2 system) and Tragadero River (from Oro sub- 1 Southern Scientific Centre of Russian Academy of system). Bed material load and suspended Science. Russia. sorokina@mmbi.krinc.ru sediment samples were taken from both riv- 2 School of Geography, University of Leeds, UK. er channels, as well as sediment samples s.venevsky@leeds.ac.uk 60 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 Don and Kuban are the largest rivers of South Russia, both terminating in the Azov THE ASYMMETRICAL CHANNEL Sea. The watersheds of the rivers comprise DEVELOPMENT IN MODERN ALLUVIAL almost 500 000 km2, therefore analysis of DEPOSITS: NEOTECTONIC EVIDENCES. dynamics discharge and solid load here is CUMBRES CALCHAQUÍES RANGES, important task. We analysed dynamics of ARGENTINA discharge and solid load in the Don and José A. Sosa Gómez Kuban Rivers for the period 1940-2000 Facultad de Ciencias Naturales – Universidad Nacio- years, using systematic annual observations. nal de Tucumán, Miguel Lillo 205, T4000JFE – San We found for both rivers that there is a Miguel de Tucumán, Argentina. strong variation of the discharge driven jsosago@gmail.com mainly by climate. On the contrary, solid load strongly depends on the river’s regula- At the foot of the Cumbres Calchaquíes tion. The load decreased with implementa- Ranges (CCR, Tucumán Province), more pre- tion of large hydrological projects in 1952 cisely the area where this range structurally for the Don River and in 1972 for the Kuban approaches the Aconquija System (AS) in the River. Positive correlation between river run- Tucumán Province, several alluvial fans off and solid load is seen for both cases, have originated, mainly coming from the however, solid load of Don is decrease slight- CCR slopes. However, these sedimentary de- ly in the last decade of XX century, despite of posits look very heterogeneous in their mor- approximately constant river run-off. We phology. analyse decrease in the seasonal peak of sol- One of these alluvial fans is located in an id load and river run-off for both rivers after area between El Castillo de las Brujas and construction of reservoirs in 1952 and 1972. Los Cardones an unusual channel pattern is Anthropogenic changes of river run-off in observed in the satellite images. The alluvial the Kuban River (minimum 5.7 km3 in fan radius is 6 km; the length from the apex 1986) were highest 1970 -1986 period, and is 6.8 km and the alluvial fan channels flow for the Don River (minimum 9.5 êì3 in towards Amaicha River. The amount of 1972) similar changes took part in 1972- channels is highly variable, from the apex to 1975. Increase in the Kuban River run-off is the central fan 4 alluvial channels can be observed from 1987 mainly due change in the observe; while, from the central towards the precipitation in the region. Amaicha River the number increase to 13 Solid load in the Don River has dropped and the change in degree of incisions, sinu- from 4.0 to 2.8 million tons per year in the osity etc is noticeably abrupt. period 1953-1972 after the construction of This difference between apical and distal Zimla Reservoir. For the Kuban River the de- areas is also emphasized by the channel inci- crease in solid load was more radical from sions observed sharply in the central zone. 8.2 to 0.86 million tons per year in the peri- The deepest channels are observed from the od 1973-2004 after the construction of Kras- central to the distal alluvial fan area, where- nodar Reservoir. This can be explained by as in the apex area the channels are shal- mountainous type of the Kuban watershed. lower. A topographic step in the central area of the alluvial fan has been recorded in both field studies and satellite images analysis. Further, this step or escarpment form a belt, around 150 m width, normal to the drainage direction and coincides with the zone where the amount of channels changes. The belt has been interpreted as a neotectonic reacti- vation of the Amaicha Fault, which also marks the main border between CCR and Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 61 AS. No deflation on the channels has been forms a splay deposit of 1.5 km2. At the observed, which would indicates only a ver- present day, this area is mainly covered by tical compressive reactivation of the underly- plantations, but there are also areas without ing structural block to the river basin. cultivations, possibly due to the seasonal stream regime and low quality of soil. Multiple mechanisms are considered to EVOLUTION OF THE SAN IGNACIO RIVER: be responsible for the modifications of the AN EXAMPLE OF THE TECTONIC, CLIMATIC SIR and other streams at the south of Tu- AND BASE LEVEL CONTROLS IN THE cumán Province: tectonic (the slope changes RIVER DYNAMIC, TUCUMÁN, ARGENTINA caused by tilting of the blocks in the subsur- José Sosa Gómez,1 Sergio M. Georgieff1, 2 face), climate (transition area of rainfall, 1 Facultad de Ciencias Naturales – Universidad Na- from 800 mm to 600 mm per year), base lev- cional de Tucumán, Miguel Lillo 205, T4000JFE – el (the migration of Marapa River to the San Miguel de Tucumán, Argentina. south produced an early upstream join with jsosago@gmail.com SIR), and finally, and less apparent, an- 2 Consejo Nacional de Investigaciones Científicas y thropic activity. Técnicas, CONICET. The orogenic belt of the northern Sierras COMPARISON OF DEPOSITIONAL Pampeanas in the provinces of Tucumán and DYNAMICS AMONG THE BRAIDED, Catamarca, Argentina, has developed an im- MEANDERING AND STRAIGHT CHANNEL portant drainage network towards the east, REACHES IN THE LOWER YELLOW RIVER which flows to the Mar Chiquita’s endorheic Suiji Wang system. The San Ignacio River (SIR, Tucumán Key Laboratory of Water Cycle and Related Land Province) is a tributary to that system with a Surface Processes, Institute of Geographical Scien- reduced to moderate discharge (0.09 – 18.4 ces and Natural Resources Research, Chinese Aca- cumecs). The SIR flows towards northwest demy of Sciences, Beijing 100101, China. across Potrerillo, Balcosna, Los Pinos and Los wangsj@igsnrr.ac.cn Llanos Ranges. The river is controlled by a NNW-SSE fault system and forms a deeply in- There are braided, meandering and cised valley in the basement rocks. Besides, straight channel reaches along the lower Yel- the igneous-metamorphic massif defines an low River. The difference in channel planform uncommon pattern of high sinuosity. Howev- certainly is influenced by different deposition- er, when the river reaches the plain, the mod- al dynamics. In this work, according to a se- ifications in the channel pattern allow also ries of data collected from the yearbook of identifying unusual changes in the river sinu- the water and sediment of the Yellow River, osity across to the plain. the different indexes representative channel The most noticeable modification in the depositional dynamics has analyzed. The re- sinuosity of SIR is observed in the confluence sults show that, there are evident differences with Marapa River, which is manifested as in depositional dynamics among the braided, systematic channel belt migration towards meandering and straight channel reaches in the north and a continuous increment in the the lower Yellow River. The channel gradient sinuosity. In the past century, the SIR formed is the maximum for the braided reach, which splays deposits onto the plains, generating ranges 0.2‰ ~ 0.14‰, is moderate for the widely-distributed lobes of important dimen- meandering reach, which ranges sions as an arheic system. The La Posta and 0.14‰~0.10‰, and the minimum for the El Sueño Streams located to the south show straight reach, which less than 0.10%. The an analog behavior to the SIR. The El Sueño flow velocity of the bankfull discharge is also Stream shows a straight pattern at the foot- larger for the braided, moderate for the me- hills and 10 km in downstream direction andering and least for the straight reaches. Its 62 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 variational extent decreases downwards along with local measures leading to the collapse of the three channel patterns. The gross power living riverine systems. In Europe and other of stream flow is decreases from the braiding developed countries, integration of geologi- via meandering to straight reaches and its cal, hydrological and geomorphological data ratio is 2.31:1.35:1. The specific power of with biological monitoring tools is consid- stream flow is minimum for the braided, ered fundamental in water legislation and maximum for the meandering and moderate management activities. In the last decades a for the straight reaches and its ratio is 0.52: new paradigm in the evaluation of surface 1.18:1. The channel bed sediment is relative waters quality was identified and concepts fine and generally lacks the roll component. like biotic integrity or ecological status were The median grain size is 3.0Ö, 3.2Ö and defined to adequately manage water resourc- 3.67Ö for the braided, meandering and es. In Argentina these concepts only concerns straight reaches, respectively, further more, research and there are no standardized meth- the sediment sorting is also enhanced along odologies to be applied in water manage- the different channel reaches downwords. The ment. sedimentation rate on the channel beds is dif- The Río Quequén Grande watershed has a ferent among the three channel pattern reach- surface of about 9,940 km2 and is located in es under the influence of the different deposi- the southeast of Buenos Aires province, Argen- tional dynamics. It is the minimum for the tina. It outflows into the Atlantic Ocean. The braided, maximum for the meandering and aims of this ongoing research are: to inte- moderate for the straight reaches when dis- grate abiotic and biotic information, to rec- charge is moderate to large, and it is approx- ognize natural and anthropogenic spatial het- imative among the three channel pattern erogeneity and to test methodologies for the reaches, but a decrease tendency downwards, assessment of ecological status of the Río when discharge is small. In addition, the sed- Quequén Grande watershed. A multidisci- imentation rate on braided channel bed evi- plinary approach is being developed. dently depends on the variation of discharge, The watershed was characterized, using and decreases with increasing discharge. an integrated informative system of the geo- Key Words: Depositional dynamics; Sedi- logical, geomorphological, sedimentologi- mentation rate; Braided chnnel; Meandering cal, hydrological, geochemical, land uses channel; Straight channel; Lower Yellow and biological information. Textural and River. geochemical bed sediments analysis and chemical water characterization of the main tributaries and the main course are also MULTIDISCIPLINARY STUDY OF RÍO available. Bankfull channel and caliche out- QUEQUÉN GRANDE BASIN, ARGENTINA crops that crossed the Río Quequén Grande Liliana B. Teruggi,1 Silvia Sala,2 Elena Marrochino,3 channel were mapped. These data together María J. Kristensen,2 Enrica Caporali,1 Carmela with fluvial cross sections were used for the Vaccaro,3 María A. Casco,2 Adrian Cefarelli2 hydraulic analysis. 1 Dipartimento di Ingegneria Civile e Ambientale, As a first approach, a biological moni- Università degli Studi di Firenze, Via S. Marta, 3 toring campaign was defined for integrating – 50139 Florence, Italy. lteruggi@dicea.unifi.it ecological information with preexistent 2 FCNyM, Universidad Nacional de La Plata, Argen- data. Samples for principal nutrients analy- tina. ses were collected. General habitat quality 3 Dip.di Scienze della Terra, UNIFE, Italy. was also evaluated and benthic algal com- munities, aquatic and riparian vegetation In Argentina, rivers are managed from a were sampled. In general the preliminary political and an engineering point of view biological results indicate that the moni- and the associated specific environmental tored rivers have an insufficient water qual- problems (e.g. floods, pollution) are solved ity possibly related to the diffused pollution Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 63 due to intensive agricultural activities. Fur- minates in a ‘floodout’, characterised here by ther research is necessary. In particular bio- an unchannelled reedswamp. In the past monitoring will need to be continued, and ~60 years, at least four avulsions have oc- the number of monitoring sites will need to curred in the channel reach immediately up- be increased. stream of the floodout, forming abandoned channel-levee complexes and altering the distribution of water and sediment supply. MORPHOLOGICAL AND SEDIMENTARY Small tributaries surrounding the wetland DYNAMICS OF A SOUTH AFRICAN also supply water and sediment to this flood- FLOODPLAIN WETLAND: FROM out and another floodout located farther CHANNELLED TO UNCHANNELLED AND downvalley. Augering reveals that organo- BACK TO CHANNELLED? clastic sediments >3 m thick have accumu- S. Tooth,1 T.S. McCarthy,2 H. Rodnight,3 A. Keen- lated in the floodouts as broad lobes that in Zebert,1 M.D. Rowberry,2 D. Brandt2 places have buried the former meander belt 1 Institute of Geography and Earth Sciences, Aberyst- sediments. On the steepened, downvalley wyth University, UK (* set@aber.ac.uk). sides of these lobes, small headcutting chan- 2 School of Geosciences, University of the Witwater- nels receive water that filters through the srand, South Africa; floodouts. If headcutting through the lobes 3 Institut für Geologie und Paläontologie, Universität continues, a through-going channel will re- Innsbruck, Austria. establish upstream, and will eventually link with the sinuous but now essentially mori- Understanding the allogenic and autoge- bund channel still present in the lowermost nic controls on wetland dynamics is essential wetlands. Along the Blood River, the relative for improving interpretations of wetland sed- roles of allogenic and autogenic factors in imentary successions and for informing wet- initiating this sequence of channel-flood- land conservation and remediation schemes. plain changes remain unclear, but the result- We focus on the ~15 km2 upper Blood River ing adjustments are partially analogous to floodplain wetlands, KwaZulu-Natal, South the system-scale, morphological and sedi- Africa, where aerial photographs, field inves- mentary dynamics of those dryland fluvial tigations, and Optically Stimulated Lumines- systems that are also characterised by a cence (OSL) ages provide evidence for combination of channelled and unchannelled marked channel-floodplain changes during landforms (e.g. discontinuous ephemeral the very late Holocene. Between ~600 and streams, erosion cells). From a management 150 years ago, the wetlands were character- perspective, knowledge of these dynamics ised by a through-going, meandering chan- can help to anticipate and mitigate undesir- nel set within a 2.5-km-wide floodplain. able future wetland changes. Wetland sedimentation resulted primarily from lateral point-bar accretion of thin (<4 m), fining-upwards successions of gravelly FLUVIAL REWORKING OF PYROCLASTIC sand to mud, and from oxbow infilling by DEPOSITS: THE CRETACEOUS LOWER organic-rich mud. A sinuous channel MEMBER OF THE BAJO BARREAL flanked by oxbows remains in the lower- FORMATION, SAN JORGE BASIN, most wetlands but during the last 100-150 PATAGONIA, ARGENTINA years, major morphological and sedimentary Aldo Martín Umazano,1 Eduardo Sergio Bellosi,2 changes have occurred upstream, leading to Graciela Visconti,3 Ricardo Néstor Melchor1 dramatic changes in the spatial distribution 1 INCITAP (CONICET-UNLPam), Av. Uruguay 151, and style of wetland sedimentation. The 6300 Santa Rosa, Argentina. former through-going, meandering channel amumazano@exactas.unlpam.edu.ar; has been replaced by a straighter channel 2 CONICET-MACN, Ángel Gallardo 470, 1405 Buenos that decreases in size downstream and ter- Aires, Argentina. 64 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 3 UNLPam, Av. Uruguay 151, 6300 Santa Rosa, massive, matrix-supported and intraclastic Argentina. conglomerates. Intercalations of tuff levels with through cross-bedding or paleosols are The lower member of the Bajo Barreal For- scarce. Fa7 (ponds) includes sheet-like to mation (Cretaceous of Patagonia) records flu- channel-like tuffaceous mudstone bodies with vial sedimentation affected by explosive vol- plane parallel lamination, asymmetrical rip- canism produced in the Patagonian Andes. ples or massive structure arranged in coars- Five sections were studied along a N-S ening-upward cycles. Facies relationship sug- transect in the San Bernardo Range. This gests fluvial systems constituted by different member is composed of sandstone-conglom- types of fluvial channel belts (Fa3) and flood- erate lenses interbedded with thicker and fin- plains where accumulation of primary pyro- er-grained tuffaceous sheets. Facies associa- clastic detritus occurred (Fa1 and Fa2), al- tions (Fa) defined include sub-aerial primary though the remobilization of these by differ- pyroclastic deposits (Fa1 and Fa2) and epi- ent fluvial processes was common (Fa4 to clastic deposits partially originated by re- Fa7). working of the formers (Fa3 to Fa7). Fa1 (py- roclastic ash-falls) is composed of massive or laminated, fine-grained vitric tuffs showing MULTIPLE-POINT SIMULATION OF mantle bedding and pedogenized tops. Fa2 CHANNELIZED AND UNCONFINED (pyroclastic flows) consists of stratified lapilli FLUVIAL DEPOSITS: AN EXPLORATORY tuffs with reverse grading of pumice that pass MODEL FOR CRETACEOUS OIL-BEARING upward to cross-bedded tuffs, which are SANDSTONES OF CENTRAL PATAGONIA capped by massive tuffs. Fa3 (fluvial channel Aldo M. Umazano,1 Claudio Larriestra,2 Eduardo S. belts) includes fining-upward bodies with Bellosi3 channel or ribbon geometry, increasing their 1 INCITAP (CONICET-UNLPam), Uruguay 151, Santa thickness and width from N to S. Fa3 deposits Rosa, Argentina. begin with through cross-bedded conglomer- amumazano@exactas.unlpam.edu.ar ates or horizontal stratified breccias with ver- 2 Larriestra Geotecnologías, Cosentini 1190, Buenos tical transition to through cross-bedded or Aires, Argentina, clarriestra@larriestra.com massive sandstones. Rarely, pause-planes 3 Museo Argentino Cs. Naturales, A. Gallardo 470, were detected in the lower part of channel Buenos Aires, Argentina. ebellosi@sei.com.ar deposits suggesting intermittent sedimenta- tion. Paleocurrents indicate paleoflow to- The results of a multiple-point simulation wards E-SE in all localities. Architectural of the lower member of the Bajo Barreal analysis mostly suggests multi-channelled and Formation (San Jorge Basin) are shown us- subordinately single-channelled rivers with ing outcrop data from the San Bernardo point bars. Fa4 (crevasse-splays) is character- Range. Five localities were studied defining ized by massive and cross-bedded lobe- a 68 km length N-S transect. This member is shaped sandstone bodies with subtle fining- equivalent to the main hydrocarbon produc- upward trend, participation of mudstone ing unit of the basin. Multiple-point stochas- drapes is rare. Fa5 (sheet-floods) comprises tic sequence simulation is a statistical proce- sheet-like strata of fine-grained tuffs with dure that allows to simulate categorical vari- scoured bases; commonly they are massive in ables, particularly curvilinear facies struc- the basal part and laminated in the upper sec- tures, from relative frequencies observed in tor. Rarely, there are intercalations of tuffs training images (numerical representation of and sandstones with different cross-beddings a sedimentary model that includes facies or pedogenic features. Paleodrainage was patterns). According to facies interpretation, near orthogonal to those recorded in Fa3 de- the training volume corresponds to a fluvial posits. Fa6 (debris-flows) is characterized by model with channel-belts showing moderate sheets to plano-convex bodies dominated by sinuosity (adapted from Pyrcz et al., 2008); Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 65 with the following size x=256 y= 256 and ence. Peat compaction likely plays an impor- z=128 nodes. Five main facies associations tant role in the evolution of alluvial plains, are distinguished from outcrop data: fluvial for example by providing extra accommoda- ribbon-shaped channel-belt sandbodies, tuf- tion space, which affects temporal and spa- faceous sheet-floods with scoured bases, ash- tial fluvial sedimentation patterns. It has fall deposits, lacustrine mudstones and pyro- also been suggested that differential peat clastic flows (ignimbrites). Maximum thick- compaction affects floodplain gradients, and ness is 350 m in the Southern region, and hence may affect the occurrence of avulsion. the area is 46000 km2. Alluvial architecture In such ways, peat compaction influences the of the succession is characterized by the ab- alluvial architecture of both modern and sence of discontinuity surfaces or trunca- ancient alluvial sequences, which is impor- tions, so the model possesses a constant num- tant knowledge for e.g. the exploration of ber of layers. The used algorithm is SNESIM natural resources such as oil and gas. (Single Normal Equation) defined by Stre- Still, there is a lack of field data to test belle (2002), and conditioning data come such hypothesis. Therefore, field research, from five outcrop profiles. Observed orienta- using new methods to quantify peat compac- tion of sandbodies was used in training im- tion, was carried out in the Cumberland ages to guide simulation. The cell size is Marshes (Canada) and the Rhine-Meuse del- x=300 m, y=300 m, z=1.75 m. General fa- ta (The Netherlands), where processes oc- cies proportion (72% sheet-floods, 22% curring on respectively decades and millen- channels, 6% the remaining facies) from nia timescales were studied. Most important original logs is respected in the resulting sim- factors controlling the amount of subsidence ulated model, where proportion of channels due to peat compaction are 1) the organic varies between 9-45%, 5-29% and 17-28% matter content of peat, 2) stress imposed on respectively in the lower, middle and upper a peat layer by loading, 3) thickness of the sections. The model predicts that channel compressible substrate, 4) relative vertical sandbodies would be more frequent in the position in a peat layer, and 5) peat compo- Central area; and upward in the upper sec- sition. Much compaction (=thickness reduc- tion, which also displays the lower varia- tion / original thickness) occurs shortly after tion. Lacustrine facies would only occur in loading; within decades up to 43% compac- middle and upper sections, while ignim- tion might occur. In the Rhine-Meuse delta, brites and ashfalls in the upper section. This where peat layers are up to ~8 m thick, model can be improved with more informa- peat compaction has led to subsidence of up tion from outcrops and wells. to 3 m. On short timescales (101-102 years), high amounts of peat compaction locally occur THE EFFECT OF PEAT COMPACTION ON THE due to loading by crevasse splay or natural EVOLUTION OF ALLUVIAL PLAIN levee deposits. As the created additional ac- S. van Asselen commodation space is rapidly filled by in- Department of Physical Geography, Utrecht University, creased fluvial sedimentation or by peat ac- P.O. Box 80.115, 3508 TC Utrecht, The Nether- cumulation, no gradient advantages are cre- lands, s.vanasselen@geo.uu.nl ated which could drive avulsion. Peat com- paction below channel deposits rather leads Alluvial plains like deltas often contain thick to vertical aggradation and fixation of river peat layers. Peat has several distinctive prop- channels. In addition, lateral migration is erties compared to inorganic sediments, inhibited by river banks consisting of mainly which affect processes and the geometry of peat, which is highly resistant to fluvial ero- alluvial rivers. One of these properties is the sion. On longer timescales, when the maxi- high compressibility of peat, which poten- mum compaction potential of peat layers in tially leads to high amounts of land subsid- an area has largely been reached, delta 66 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 lobes become prone to switch to another part sequence consisting of estuarine mudstones, of the alluvial plain. flaser and wavy heterolithic and herringbone sandstones, and bayhead delta sandstones. The medium section is mainly fluvial and ACCOMMODATION / SEDIMENT SUPPLY shows, from west to east, a definite transi- FLUVIAL DEPOSITION CONTROLLED BY tion from conglomerate braided systems to BASE LEVEL CHANGES AND RELATIVE SEA sandy meandering and anastomosing systems LEVEL FLUCTUATIONS IN THE MATA at the farther end. The upper section shows AMARILLA FORMATION (EARLY UPPER fine grained distal fluvial deposits in the CRETACEOUS), SOUTHERN PATAGONIA, west and littoral setting in the east. In this ARGENTINA manner, the lower and upper section should Augusto Nicolás Varela represent higher accommodation / sediment Centro de Investigaciones Geológicas, Universidad supply conditions, whereas the medium sec- Nacional de La Plata – CONICET, calle 1 Nº 644 tion should correspond to a lower accommo- (1900) La Plata, Argentina. dation / sediment supply stage. augustovarela@cig.museo.unlp.edu.ar The three sections show evidence of con- sistent paleoclimatic conditions, so the vari- The aim of this contribution is to study ations in accommodation / sediment supply the tectonic, eustatic and climatic controls registered for the Mata Amarilla Formation over the Mata Amarilla Formation sedimen- are inferred to be promoted by base level tation. The area selected for the current changes related to relative sea level oscilla- study is situated along the southern margin tions. The strong west to east evolution of of the Viedma Lake, where the unit has its the fluvial systems is in correspondence to maximum outcropping thickness, reaching the direction of propagation of the Austral about 350 metres. Basin fold and thrust belt. In this way, the The Mata Amarilla Formation (Feruglio relative sea level changes of the Mata Ama- in Fossa Mancini, 1938) is composed of an rilla Formation respond to a tectonic control alternation of grey, green greyish and dark over a pure eustatic fluctuation. mudstones with whitish sandstones deposited under continental to litoral environmental References conditions. This unit date back to the Early Upper Cretaceous and is a key element for Fossa Mancini, E., Feruglio E. and Yussen de understanding the passage from the exten- Campana J. C. (1938) Una Reunión de sional Rocas Verdes basin to the foreland Geólogos de Y.P.F. y el problema de la Ter- minología Estratigráfica. Boletín de Informa- Austral Basin. The Mata Amarilla Formation ciones Petroleras, 171, 31- 95. is deposited over the deltaic Piedra Clavada Formation and is overlained by the shoreface facies of the Anita Formation. 3D COMPUTER-MODELLING OF FLUVIAL Detailed sedimentological logs, facies DEPOSITS: OUTCROPS STUDIES OF THE analysis and architectural parametres were LOWER TRONCOSO MEMBER (NEUQUÉN useful to define three sedimentary units. BASIN, ARGENTINA) AND IMPLICATIONS These sections are different in their accom- FOR THE CHARACTERISATION OF modation/sediment supply rates. Paleosol SUBSURFACE RESERVOIRS horizons appear interbedding within the Gonzalo D. Veiga,1 John A. Howell2 channel belt along the geological column. 1 Centro de Investigaciones Geológicas (CIG-Universi- The lower section of Mata Amarilla For- dad Nacional de La Plata/CONICET). Calle 1 #644, mation cropping out to the west shows dis- B1900TAC La Plata, Argentina. tal fluvial mudstones with subordinated fine veiga@cig.museo.unlp.edu.ar and medium sandstones. While at the eastern 2 Centre for Integrated Petroleum Research (CIPR- side, the deposits form a coarsening upward University of Bergen). Bergen, Norway. Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 67 Computer-based modelling of fluvial de- width proved more significant than changes posits has become a crucial tool for under- in the channel-belt sinuosity (this one calcu- standing and predicting the variability of hy- lated empirically through palaeocurrent dis- drocarbon reservoirs in the subsurface. The tribution within a channel body). Finally, precise definition of their key parameters re- slight changes in the petrophysical charac- quires quantitative geometric data that can be teristics of floodplain deposits changed the only obtained through the direct observation results of the flow simulations significantly, of the rocks. Therefore, outcrop analysis of suggesting that a detailed study of fine- potential targets or the study of suitable ana- grained facies is also of great importance in logues is important as a means of construct- the characterisation of distal fluvial succes- ing quantitative models that can be directly sions. applied to subsurface exploration. In order to evaluate the relative impor- tance of some of these variables, a detailed EPHEMERAL ALLUVIAL SYSTEMS OF THE study of the distal fluvial deposits of the TERUEL BASIN (MIOCENE, SPAIN): Lower Troncoso Member of the Huitrín For- BASINAL AND CLIMATIC CONTROLS mation in the central Neuquén Basin (west- Dario Ventra central Argentina) was performed. The aim Faculty of Geosciences, Utrecht, the Netherlands, of the study was, while building robust mod- d.ventra@geo.uu.nl els that could be applied to the subsurface in neighbouring areas, evaluate how key ele- The classic stratigraphic record of fluvial ments that can be only assessed through the systems, with protracted discharge through 3D observation of the sedimentary bodies time, is characterized by highly structured influence the outcome of dynamic flow sim- and organized deposits both at facies and ulations. architectural element scales. Relatively less Models were built considering the distri- attention has been paid to deposits of short- bution of potential reservoir units (three range, ephemeral alluvial systems in high- types of channels and sandstone lobes) and gradient, tectonically active areas, which its contrast with low permeability units may often be confused with alluvial fans. (floodplains) at a complete unit scale (~80 The Tertiary Teruel Basin (Spain) is an m thick) in a 56 km2 area. Reservoir units association of half-grabens developed under were modelled stochastically and populated semi-arid climate. Proximal coarse-clastic with petrophysical properties from analogue systems developed at basin margins, interfin- units in the North Sea. Alternative models gering with deposits of low-energy (mudflat were built changing some of the modelling to lacustrine) distal settings. On a large- parameters (channel-belt width, sinuosity, scale distinction between overbank and detailed channel-belt vertical distribution) in channel-fill elements allows to characterize order to compare the results of flow simula- such alluvial successions as products of tions and evaluate their influence in the final channelized drainage pathways. On the oth- results. er hand, facies analysis reveals high vol- Of all the parameters analysed the main umes of poorly organized deposits resulting differences raised in the analysis of the verti- from non-newtonian hyperconcentrated flows cal distribution of sandstone bodies. The and possible in-channel debris flows. stochastic distribution of channel bodies con- Active tectonics at basin margins and a sidering only ten vertical logs gave a more semi-arid climate conducive to flash-floods uniform channel distribution and more opti- probably favored high-gradients, proximity mistic results, in contrast with the observed to sediment sources and ephemeral- dis- architecture where channels are more con- charge events, which in most cases resulted strained to a restricted vertical zone. Results in poor ability to effectively reorganize the derived from changes in the channel-belt abundant sediment supply during transport. 68 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 An additional role could have been played by indicates a growing influence of the southern high volumes of Triassic claystones in the half of Quilmes Ranges that started to basement. In particular, elevated concentra- emerge above the basin surface at 5 My, tions of suspended fines in channel flows along with the tectonic inversion stage. would have significantly contributed to Playa del Zorro Alloformation is the bet- dampen turbulence and raise flow viscosity, ter exposed and present the maximum thick- inhibiting sorting and full development of ness (1,280 m in the type stratigraphic pro- bedforms or tractive fabrics. file of Puesto Molle Grande). The unit lays This latter hypothesis can be tested by disconformably over the Peñas Azules and is comparing deposits of two such ephemeral covered in turn by the Totoral Alloformation alluvial systems dating respectively from the through a low angle irregular unconformity. Late Miocene of the central basin sector and The sandy succession of Playa del Zorro the Quaternary of the northern sector. Strik- Alloformation changes in the middle part to ing facies differences for the two successions lacustrine deposits formed by green to yel- reveal a prevalence of hyperconcentrated low-green shales rich in freshwater ostra- flows in channel-fills of the older one, ex- cods, pelecipods, gastropods and fish scales. posed to much higher sediment supply from The 40 m thick of the lacustrine deposit de- Triassic sources. creases gradually toward the North. In the At basin scale, despite the distinctiveness equivalent strata of the Ovejeria Chica strati- of fine, basinal and overbank deposits and graphic profile the lacustrine facies are ab- high-energy, coarse-clastic alluvial facies, sent. In this particular profile, the uppermost the overwhelming volume of clay present in succession of Playa del Zorro Alloformation most preserved alluvial units might signifi- shows a succession of very well developed cantly lower their potential as pathways for incised channels, with a complex architec- subsurface fluid flow. ture of multiple incisions (deep crevassing). According to the paleocurrents measured in Playa del Zorro Alloformation, the pre- THE ORIGIN OF THE INCISED CHANNELS dominant drainage was to the southeast, IN THE UPPER SECTION OF THE PLAYA coming from a north-south oriented source DEL ZORRO ALLOFORMATION (NEOGENE), area that formed the western basin border. EL CAJÓN VALLEY, CATAMARCA – The lacustrine facies are extended in the ARGENTINA north-south direction from a place near the María Eugenia Vides,1 Gerardo E. Bossi2 Ovejeria Chica to the north, down to the 1 Fundación Miguel L i l lo, Miguel L i l lo 251, Agua de la Paloma River in the south, by a T4000JFE, San Miguel de Tucumán, Tucumán, continuous extension of 70 km or more (in Argentina. subsurface). The existence of such a lacus- 2 IESGLO – UNT, Miguel Lillo 205, T4000JFE – San trine persistent environment is related to the Miguel de Tucumán, Argentina. extensional tectonic stage of the basin evolu- tion. At the top of the lacustrine horizon The Neogene succession of the Santa there is a tuff level dated in 5,7 My by Ar-Ar, María Basin at El Cajón Valley (NW-Pam- very close to the initiation time of the tecton- pean Ranges, NW Argentina) is divided in ic inversion in the Santa María Basin (circa three alloformations, from base to top: Peñas 5 My). The upper section of Playa del Zorro Azules, Playa del Zorro and Totoral. Litholo- Alloformation over the lacustrine facies, is a gy of the fillings indicates sandy fluvial sys- coarsening-up succession with an increase tems changing up into alluvial fans. Pale- participation of conglomerates, that indi- ocurrent directions indicate a changing pale- cates an increment of tectonic activity and odrainage headed to the East in the lower progressive grow of the relief, due to the alloformation and to SE in the two upper uplift of the surrounding mountain blocks. units. The change of drainage orientation As a consequence of the mountain uplift, a Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 69 climatic barrier grew up in the eastern bor- Señor de la Peña playa lake (“barreal”) a der of the basin, creating arid conditions in nearby endorheic pampean valley (“bolsón”). the Basin climate. The fluvial channel facies are normally The incised channels occurrence is relat- composed of lenticular sandy small channels ed in part to the aridification of the climate with smooth erosive bases crowded of irreg- (multiple crevassing) but also to the influ- ular paraclasts of cohesive siltstone. Inter- ence of tectonic changes. Several causes stratified with the water laid sandstones, could be associated to the lacustrine filling there are sandy beds with erosive tops end and the starting of the incised channels formed by well sorted fine grained sands developing. Considering the size and loca- with a very well preserved thin lamination. tion of the lacustrine facies, the changes in This association of fluvial poor sorted medi- the tectonic environment conducted first to um to coarse sands with silty paraclast, as- the disappearance of the paleolake and there sociated with fine well sorted sandstones is after to a general change of the local base typical of many dry rivers of the area. The level of the associated fluvial system. fine sands are reworked aeoilan material taken mainly from the river floor. A second well preserved feature of the ARID CLIMATE FLUVIAL SYSTEMS IN THE channel facies is the presence of high (2 to 5 SALICAS FORMATION (PLIOCENE), BOLSÓN m) river banks(“barrancas”) with chaotic DE PIPANACO, LA RIOJA, ARGENTINA concentration of angular blocks and rounded María Eugenia Vides1, 2 Gerardo E. Bossi2 Sergio pebbles. The Salicas Formation facies pre- M. Georgieff2, 3 sents remarkably similarities with the 1 Fundación Miguel L i l lo, Miguel L i l lo 205, present day fluvial environment developed T4000JFE, San Miguel de Tucumán, Tucumán, under an arid climate with moderate wind Argentina. mariuvides@yahoo.com.ar activity at the end of the winter, and rains 2 IESGLO – UNT, Miguel Lillo 205, T4000JFE – San concentrated in the summer (200-400 mm a Miguel de Tucumán, Argentina. year). Arid climate, in this case, could be 3 CONICET. considered a latitudinal effect of the southern convergence of the Hadley and Ferrell cells The Pliocene sedimentary succession of in a moment of much lower altitude of the the Salicas Formation outcropping around Andean Cordillera. the Bolsón de Pipanaco is laying over the Pampean Peneplain, a paleogeomorphic sur- face build during a Mesozoic and Early Cen- CLAY MINERALS RELATED TO FLUVIAL ozoic extensive erosive period. The Salicas DYNAMIC. BAJO BARREAL FORMATION. Formation consists in sandstones channel SAN JORGE BASIN, SANTA CRUZ, bodies interstratified with subordinate tabu- ARGENTINA lar fine sandstones and shales, of the María Eugenia Vides,1 Lucía Marina Ibañez,1, 2 floodplain.The unit yields fossil mammals Leonor Ferreira3 related with small herbivorous forms of 1 Fundación Miguel L i l lo, Miguel L i l lo 251, Huayquerian-Montehermosean ages (Plio- T4000JFE, San Miguel de Tucumán. cene). Shales form massive isolated tabular 2 Facultad de Ciencias Naturales e IML – Universi- bodies and show rhyzoconcretions and cal- dad Nacional de Tucumán. Miguel Li l lo 205, cretes horizons, which are interbedded with T4000JFE, San Miguel de Tucumán, Argentina. floodplain sandstones. At the west of Mazán 3 YPF S.A. Av. Pte. Roque Saenz Peña 777, Village, a thick siltstone bed, around 1.10 m, C1035AAC-Ciudad Autónoma de Buenos Aires. is interbedded with flood plain deposit Argentina. formed by decimeter tabular ill-laminated beds, which could be compared with similar Bajo Barreal Formation, Upper Creta- silty bed accumulated in the present day ceous of San Jorge Basin, Argentina, is an 70 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 important hydrocarbon reservoir. It is com- which could had induced the montmorillo- posed of fluvial channel sandstones and nite formation on the lee and the beidellita flood plain deposits. It involves south of formation on the humid exposed slope Chubut and north of Santa Cruz provinces. (Paquet and Clauer, 1997) in the flood plains The seals are both stratigraphic and structur- of fluvial systems. al. The former are represented by mudrocks laminated beds.This job aims to point out the relationships between the clay mineralo- RECONSTRUCTION OF FLOOD EVENTS gy and the fluvial dynamic. Moreover, it OVER THE LAST 150 YEARS IN THE tries to set up the possible use of the LOWER CHANGJIANG VALLEY mudrocks levels as correlation markers. Shouye Yang, Wang Zhan, Xiaoli Liu, Jianwei Li Twenty mudstone samples were taken State Key Laboratory of Marine Geology, Tongji Uni- from two logs described in the outcrops versity, Shanghai 200092, China. around La Sin Nombre small Lake, in Cerro syyang@tongji.edu.cn Guadal play. X ray analyses were performed in order to determine the clay mineralogy. The reconstruction of paleo-floods in the Montmorillonite, as the main clay mineral, Holocene has attracted many research atten- kaolinite and illite are present in the log de- tions for the present global change study. The scribed at the east side of the small lake. core sediments from one newly-emerged bar Smectite-illite mixed layered is present in in the lower Changjiang (Yangtze River) one of the samples and two others levels bear mainstream were collected for grain size no differenced smectites. Feldespars and zeo- and organic elemental measurements, with lites are the accessory minerals. The log lo- the aim to reconstruct the flood events over cated to the north of the small lake has beid- the past 150 years. Major grain size parame- ellita as the main clay mineral. Some beds ters such as mean grain size, probability cu- contain montmorillonite but never both of mulative curve and C-M diagram of the core them. Zeolites are present in the base and in sediments clearly indicate the flood event the top of the stratigraphic log. Feldespars deposition. Furthermore, the TOC/TN ratios and smectite-illite and smectite-chlorite in the sediments can indicate flood events mixed layered are present in three samples considering that during the flash floods, located towards the top. Quartz, kaolinite strong surface erosion in the upper and low- and illite can be found all along two logs in er valley of the Changjiang could transport a the clay size class. large amount of undecomposed plant debris The great abundance of smectites allows and organic components with relatively low us to classify these mudrocks as belonging C/N ratios into the lower mainstream. Based to Clayzone A (Gainza et all, 1984), al- on 210Pb dating and sedimentary geochemi- though these authors call all the smectites as cal results, the research profile recorded sev- montmorillonites. eral large floods happened from 1850 to The reasons of the predominance of smec- 1954, which completely agrees with the his- tites over other clay minerals could be in: 1) torical documents and hydrological observa- alteration of pyroclastic materials (Moore tions. It is interesting to note that the flood and Reynolds, 1989); 2) weathering in ill events since 1960s cannot be distinctly recog- dreinaged environments, swamps or flood nized on the basis of sediment grain size and plains in fluvial systems (Berner, 1971); 3) organic elemental compositions of the pro- warm climates with a very dry season (Sing- file, which mainly reflects the intense human er, 1984 and Galán, 1986). activities over the last fifty years, especially In this case, the abundance of smectites condense dam construction, which have sig- could be caused by the weathering of pyro- nificantly changed the characters of suspend- clastic underlying beds as well as the loca- ed sediment into the lower mainstream. tion of the outcrops respect to the wet winds Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 71 Contents ABSTRACTS OF KEYNOTES SPEAKERS ON THE INTERACTIONS BETWEEN TURBULENT FLOWS, SEDIMENT TRANSPORT AND BEDFORM DEVELOPMENT IN ALLUVIAL CHANNELS: 28 YEARS ON ........................ 7 Jim Best ROLE OF CONTINENTAL MARGIN INCISED-VALLEY SYSTEMS IN THE EMERGING SOURCE-TO-SINK PARADIGM ........................................................................ 7 Mike Blum UNIT-BAR DEPOSITS IN ANCIENT RIVER-CHANNEL ALLUVIUM .............................. 8 John Bridge SEDIMENTOLOGICAL AND STRATIGRAPHIC MODELS: INTEGRATION AMONG SCIENCE, TECHNOLOGY AND OIL INDUSTRY. EXAMPLES IN OIL FIELD OF GOLFO SAN JORGE BASIN, CHUBUT AND SANTA CRUZ PROVINCES, ARGENTINA .............................. 9 Luciano Di Benedettto AN OVERVIEW OF EROSION AND SEDIMENTATION PROBLEMS IN FLUVIAL SYSTEMS OF NORTHERN ARGENTINA ......................................................................... 9 Hector Daniel Farias FATHER OF THE WATERS: UNLOCKING THE SECRETS ........................................ 10 Oscar Orfeo, Daniel Parsons HISTORICAL PLANIMETRIC CHANNEL CHANGES IN AN ITALIAN RIVER: THE CECINA RIVER .................................................................................. 10 Liliana B. Teruggi, Massimo Rinaldi ABSTRACTS LOWER PALEOZOIC FLUVIAL DEPOSITS OF ARABIA: FACIES, ENVIRONMENTS AND DEPOSITIONAL STYLES, SAUDI ARABIA ........................................................ 12 Osman Abdullatif FLUVIAL DYNAMICS, ALLUVIAL ARCHITECTURE AND PALAEOHYDROLOGY OF AXIAL AND TRANSVERSE DRAINAGE SYSTEMS IN AN EXTENSIONAL SETTING: LOS ADOBES FORMATION (APTIAN), CAÑADÓN ASFALTO BASIN, ARGENTINA .......................... 12 José Oscar Allard, José Matildo Paredes, Raúl Eduardo Giacosa VOLCANIC BEDROCK MORPHOLOGY AS A CONTROL ON FLUVIAL PATTERN IN A SEMI-ARID SETTING ............................................................................. 13 José Oscar Allard, Alejandro Montes, José M. Paredes, Gustavo Gabriel Bujalesky 72 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 ALTERNATING FLUVIAL STYLES WITHIN THE MARITIMES BASIN COMPLEX OF ATLANTIC CANADA: A RECORD OF EQUATORIAL CLIMATE CHANGE DURING THE LATE PALEOZOIC ICE AGE .................................................................... 14 Jonathan P. Allen, Christopher R. Fielding, Martin R. Gibling, Michael C. Rygel MULTIPLE VALLEY FILLS FROM THE LATE QUATERNARY RECORD OF THE TUSCAN COASTAL PLAIN (ITALY) ............................................................................. 14 Alessandro Amorosi, Veronica Rossi, Giovanni Sarti, Roberto Mattei, Serena Giacomelli DEVELOPMENT AND EVOLUTION OF A LATE QUATERNARY FLUVIAL CHANNEL BELT: IMPLICATIONS FOR THE INTERPRETATION OF ANCIENT ANALOGUES ..................... 15 Alessandro Amorosi, Giovanni Sarti FLUVIAL EVOLUTION AND SEQUENCE MAPS OF INTRAMOUNTAIN BRAIDED RIVERS, CATAMARCA PROVINCE, ARGENTINA ............................................................... 16 Karina B. Anis, Gustavo E. Rizo, Lucía M. Ibañez, Sergio M. Georgieff UPPER CRETACEOUS - SEDIMENTARY PALEOENVIRONMENTS IN THE NORTHEASTERN MARGIN OF THE NEUQUINA BASIN – THE ANACLETO FORMATION AND THE LOWER MEMBER OF THE ALLEN FORMATION. ARGENTINA .......................................... 17 Paula Armas, María Lidia Sánchez, Estefanía Asurmendi TECTONIC GEOMORPHOLOGY OF RAMHORMOZ WATERSHED AREA IN THE ZAGROS FOLD BELT OF SOUTHWESTERN IRAN ........................................................... 17 Arash Barjasteh HIGH FREQUENCE CICLICITY IN CONTINENTAL SYSTEMS: EXAMPLE OF FM. TORDILLO, UPPER JURASSIC NEUQUÉN BASIN ARGENTINA ............................... 18 Arregui Carlos Daniel THE PROCESSES AND DEPOSITIONAL ARCHITECTURE OF BIG RIVERS: THE RIO PARANÁ, ARGENTINA ................................................................... 18 Ashworth, P. J., Amsler, M. L., Best, J. L., Hardy, R. J., Lane, S. N., Nicholas, A. P., Orfeo, O., Parsons, D. R., Reesink, A. J. H., Sambrook Smith, G. H., Sandbach, S. D., Szupiany, R. N. FACIES CHARACTERISTICS AND ORIGIN OF THE QUATERNARY SEDIMENTS IN THE NILE VALLEY, EGYPT .......................................................................... 19 Awad, M.H. HIGH-FREQUENCY VARIATIONS IN ACCOMMODATION SPACE IN PUNTA SAN ANDRÉS ALLOFORMATION (PLIO-PLEISTOCENE), BUENOS AIRES PROVINCE, ARGENTINA ....... 20 Elisa Beilinson ON THE INFLUENCE OF DENSITY DIFFERENCES BETWEEN MIXING FLOWS AT RIVER CONFLUENCES ....................................................................................... 21 Best, J. L., Parsons, D. R., Amsler, M. L., Kostaschuk, R. A., Lane, S.N., Orfeo, O., Szupiany, R.N., Hardy, R.J. Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 73 VISUALIZATION OF DUNE AND BAR-GENERATED TURBULENCE AND SEDIMENT SUSPENSION: IMAGES FROM THE SOUTH SASKATCHEWAN RIVER, CANADA, AND IMPLICATIONS FOR SUSPENDED SEDIMENT RATING CURVES ............................... 21 Jim L. Best, R.E. Thomas, P.J. Ashworth, S.N. Lane, I.A. Lunt, G.H. Sambrook Smith, C.J. Simpson CONTINENTAL SHELVES AS THE LOWSTAND FLUVIAL LONGITUDINAL PROFILE ......... 22 Mike Blum ROLE OF INCISED-VALLEY SYSTEMS IN SOURCE-TO-SINK SEDIMENT ROUTING AND STORAGE: EXAMPLES FROM THE LATE QUATERNARY NORTHERN GULF OF MEXICO MARGIN ............................................................................................... 22 Mike Blum, Matt Garvin LAS CUMBRES FORMATION (EARLY PLEISTOCENE), AN EXAMPLE OF THE OROGENY CLIMAX TECTOFACIES IN THE PAMPEAN RANGES ............................................ 23 Gerardo E. Bossi, Sergio M. Georgieff, Lucía M. Ibañez THE RED BEDS OF HUALFÍN FORMATION IN THE SYNRIFT STAGE OF PAMPEAN RANGES, NORTHWEST OF ARGENTINA: PALEOGEOGRAPHIC AND ENVIRONMENTAL IMPLICATIONS ........................................................................................ 24 Gerardo E. Bossi, Sebastián Moyano NATURAL AND ANTHROPICAL FACTORS AFFECTING MODERN RIVERS AND RESERVOIRS IN A SEMIARID BASIN. TAPIA - TRANCAS BASIN, TUCUMÁN, ARGENTINA .......................................................................................... 25 Bustos, María Soledad PALEOFLUVIAL SYSTEMS IN THE WESTERN CHACO PLAIN, TUCUMÁN PROVINCE, ARGENTINA .......................................................................................... 25 Collantes, M.M., Sayago, J.M., Busnelli, J. THE RIERA DE SOBIRANS (NE, SPAIN) MODEL OF OVERELEVATED TORRENTIAL CHANNELS: SEDIMENTARY CHARACTERISTICS ................................................ 26 Ferran Colombo, Oriol Riba, Lluis Rivero ESTIMATION OF SUSPENSION SEDIMENT VOLUME IN TO THE FUTURE DAM OF POTRERO DE LAS TABLAS ON RIO LULES. TUCUMAN PROVINCE. REPUBLICA ARGENTINA .......................................................................................... 26 Anibal Comba, Julian Soto AN ESTUARINE FOSSIL ASSEMBLAGE FROM THE YACORAITE FORMATION (MAASTRICHTIAN-DANIAN) AND ITS PALEOENVIRONMENTAL SIGNIFICANCE. JUJUY - NORTHWESTERN ARGENTINE .......................................................... 27 Cónsole Gonella, C. A., L.R. Horta, P.E. Herrera Oviedo, M. Griffin, S.M. Georgieff, F.G. Aceñolaza GRADUAL LATERAL RIVER MIGRATION INDUCED BY LATERAL FLOODPLAIN TILTING; A 3D NUMERICAL SIMULATION .................................................................. 27 Arjan de Leeuw, Quintijn Clevis, Greg Tucker, Poppe L. de Boer 74 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 NEOPROTEROZOIC FLUVIAL-DELTAIC DEPOSITS OF THE AMAZON CRATON: THE PROSPERANÇA FORMATION, STATE OF AMAZONAS, BRAZIL .............................. 28 Roberto César de Mendonça Barbosa, Afonso César Rodrigues Nogueira, Werner Truckenbrodt FLUVIAL RESPONSE TECTONIC FOLDING AND TILTING IN THE EOCENE FORELAND BASIN, NW ARGENTINA .......................................................................... 29 Cecilia del Papa, Fernando Hongn INTEGRATED MODELING OF FLUVIAL FAN FRINGE SHEET SANDSTONE: TEN BOER CLAYSTONE MEMBER, SOUTHERN PERMIAN BASIN, NW EUROPE ........................ 29 M.E. Donselaar, I. Overeem, J.H.C. Reichwein, C.A. Visser GEOMORPHOLOGICAL DEVELOPMENT OF THE ATACAMA PLANATION SURFACE ........ 30 L.A. Evenstar, A.J. Hartley A SEDIMENTARY QUANTITATIVE MODEL FOR THE BAJO BARREAL FORMATION (CRETACEOUS): INTEGRATION BETWEEN OUTCROPS AND SUBSURFACE DATA. SAN JORGE BASIN, SANTA CRUZ, ARGENTINA .............................................. 30 Leonor Ferreira, Sergio M. Georgieff, Agustina Santangelo, Yanko Kamerbeek A FACIES MODEL FOR FLUVIAL SYSTEMS IN THE SEASONAL TROPICS AND SUBTROPICS .......................................................................................... 31 Christopher R. Fielding, Jonathan P. Allen, Jan Alexander, Martin R. Gibling SHEET-LIKE FLUVIAL ARCHITECTURE ON REGIONAL SCALES: EXAMPLES FROM THE CRETACEOUS WESTERN INTERIOR SEAWAY OF NORTH AMERICA ......................... 32 Christopher R. Fielding, Matthew J. Corbett, Lauren P. Birgenheier SEDIMENTOLOGY AND STRATIGRAPHIC ARCHITECTURE OF THE UPPER PALEOCENE RÍO CHICO FORMATION, GOLFO SAN JORGE BASIN, PATAGONIA ARGENTINA .......... 33 Nicolás Foix, José M. Paredes POST-LGM INCISED VALLEYS IN THE VENETIAN-FRIULIAN PLAIN (NE ITALY) ............ 34 Alessandro Fontana POROSITY PREDICTION FOR FLUVIAL SAND-GRAVEL MIXTURES ........................... 34 Frings, R.M. CHARACTERIZATION OF FLUVIAL SANDSTONES IN CERRO GUADAL NORTE OIL FIELD, GOLFO SAN JORGE BASIN, SANTA CRUZ, ARGENTINA ............................. 35 Sergio M. Georgieff, José A. Sosa Gómez, Leonor Ferreira, María Eugenia Vides, Lucía M. Ibañez, Ramona Ovejero, Gerardo E. Bossi, Agustina Santangelo, Guillermo A.V. Richter, Karina B. Anis, Esteban M. Pieroni, Sebastián Moyano, Yanko Kamerbeek AN ESTIMATE OF THE PATTERN OF FLUVIAL EROSION FOR THE HIMALAYAS ........... 36 Parthasarathi Ghosh Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 75 TRANSITION OF THE MIDDLE AMAZON RIVER IN THE CONTEXT OF CLIMATIC CHANGE ............................................................................................... 36 Jose Max Gonzalez Rozo, Afonso César Rodrigues Nogueira, Werner Truckenbrodt INTERPRETATION AND FLUVIAL PARAMETERS OF SUBSURFACE SANDSTONE BODIES, CASTILLO AND BAJO BARREAL FORMATIONS (CRETACEOUS) IN THE CAÑADÓN VASCO OIL FIELD, GOLFO SAN JORGE BASIN, SANTA CRUZ, ARGENTINA .............. 37 Sebastián Grignola, Sergio M. Georgieff, Leonor Ferreira TECTOSEDIMENTATION AND COMBINED TRAPS IN THE SANDSTONE HYDROCARBON- BEARING OF THE BAJO BARREAL FORMATION (CRETACEOUS) AT LA SIN NOMBRE LAKE, GOLFO SAN JORGE BASIN, SANTA CRUZ, ARGENTINA ............................. 38 Raul Gutierrez, Agustina Santangello SEDIMENTOLOGICAL AND PALAEOHYDROLOGICAL CONSTRAINTS ON THE DEVELOPMENT OF A LATE SILURIAN TO EARLY DEVONIAN ‘SYN-RIFT’ FLUVIAL SUCCESSION IN THE MIDLAND VALLEY BASIN, SCOTLAND ................................ 39 Adrian Hartley, Stuart Archer, Stephanie Davidson, Tim Davis, Laura Evenstar, Sophie Leleu DISTRIBUTIVE FLUVIAL SYSTEMS (DFS): A RE-EVALUATION OF FLUVIAL FACIES MODELS ............................................................................................... 39 A.J. Hartley, G.S. Weissmann, G.J. Nichols FROM RIVER VALLEY TO ESTUARY: EUSTATIC AND GLACIO-TECTONIC CONTROLS ON THE EARLY-MIDDLE HOLOCENE RHINE-MEUSE SYSTEM, THE NETHERLANDS ....... 40 Marc P. Hijma SHEET LIKE CHANNEL BODIES, WEATHERING AND CALCRETES. A COMPARISON BETWEEN TWO EXAMPLES OF THE DUERO AND ALMAZÁN BASIN (SPAIN) ............. 41 Pedro Huerta, Ildefonso Armenteros, Pablo Gabriel Silva CHANNEL ABANDONMENT PROCESSES IN THE MAHAKAM DELTA, EAST BORNEO, INDONESIA ........................................................................................... 42 Salahuddin Husein, Joseph J. Lambiase PETROGRAPHY AND POROSITY IN FLUVIAL HYDROCARBON–BEARING SANDSTONES. BAJO BARREAL FORMATION (CRETACEOUS), SAN JORGE BASIN, ARGENTINA ........ 42 Lucía M. Ibañez, Ramona Ovejero, Sergio Georgieff, Leonor Ferreira, Gerardo E. Bossi LATE WEICHSELIAN DEGLACIATION, BASE LEVEL CHANGES AND FLUVIAL RESPONSE, AIN RIVER, JURA, FRANCE ....................................................................... 43 C. Kasse WHY LARGE RIVERS HAVE LOW-ANGLE DUNES ............................................... 43 Ray Kostaschuk WASH LOAD IN THE PARANÁ RIVER, ARGENTINA ........................................... 44 Ray Kostaschuk, Oscar Orfeo 76 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 SEDIMENTATION SETTING AND QUATERNARY DEPOSITION ................................ 44 Hasan Kuliçi, Jakup Hoxhaj DETERMINATION OF RELATIONS BETWEEN THE TRANSPORT OF BOTTOM MATERIAL AND SUSPENDED MATERIAL IN A LARGE RIVER, BASING ON GRAIN SIZE ANALYSIS OF DEPOSITS IN ARTIFICIAL WATER RESERVOIRS (THE VISTULA CATCHMENT BASIN, POLAND) .............................................................................................. 45 Adam Lajczak CHANNEL BED ADJUSTMENTS FOLLOWING A MAJOR DEBRIS FLOW IN A MOUNTAIN STREAM ................................................................................ 46 Hélène Lamarre, Geneviève Marquis, André G. Roy, Thomas Buffin-Bélanger, Jay Lacey, Bruce MacVicar FLOW VELOCITY FIELDS OVER A 15-KM LONG DUNEBED IN THE LOWER MISSISSIPPI RIVER DURING SPRING HIGH DISCHARGES ................................................... 46 Suzanne F. Leclair NORTH ATLANTIC TRIASSIC RIFT BASIN FILLS: CONTROLS ON THE EVOLUTION FROM FLUVIAL TO PLAYA STAGE .................................................................. 47 Sophie Leleu, Adrian J. Hartley CHANNEL CROSS-PROFILE CHANGE AT TOUDAOGUAI STATION AND ITS RESPONSE TO THE OPERATION OF UPSTREAM RESERVOIRS IN THE UPPER YELLOW RIVER ....... 48 Lishan Ran, Suiji Wang, Xiaoli Fan LATE QUATERNARY ALLUVIAL SEQUENCES IN THE ARID PIEDMONT OF CORDILLERA FRONTAL (33º-34º S) MENDOZA, ARGENTINA ................................................ 48 Mehl Adriana, Zárate Marcelo RESERVOIR ARCHITECTURE MODELING OF FLUVIAL POINT BARS: LORANCA BASIN, SPAIN ................................................................................................. 49 L.A. Meijer, K.A. van Toorenenburg, M.E. Donselaar VARIABILITY OF CHANNEL MORPHOLOGY OF LARGE FLUVIAL FAN SYSTEMS IN ACTIVE FORELAND TECTONIC SETTINGS: VARIABILITY OF CHANNEL MORPHOLOGY OF LARGE FLUVIAL FAN SYSTEMS IN ACTIVE FORELAND TECTONIC SETTINGS: IMPACT ON RESERVOIR ARCHITECTURE AND CONNECTIVITY ............................... 50 Andrea Moscariello, Chris Bugg, Niels Hovius THE FLOODPLAIN SEDIMENTOLOGY OF COOPER CREEK. WHY BILLABONGS (WATERHOLES) IN THE CHANNEL COUNTRY START AND STOP ............................. 50 Gerald C. Nanson, Josh R. Larsen, Dioni I. Cendon, Simon D. Fagan, Brian G Jones HYDRAULIC GEOMETRY OF NARROW DEEP CHANNELS IN PEATLAND FLOODPLAINS; EVIDENCE FOR OPTIMISATION ..................................................................... 51 Gerald Nanson, Rachel A. Nanson, He Qing Huang Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 77 FLOOD RISK ON FLUVIAL MARGINS AND URBAN AREAS. TUCUMÁN. ARGENTINA ........................................................................................... 52 Neder, Liliana del Valle, Busnelli, José MAIN CONTROLS ON THE EVOLUTION OF DISTAL VOLCANICLASTIC SUCCESSIONS IN CONTINENTAL ENVIRONMENTS: CASTILLO FORMATION (ALBIAN) OF THE GOLFO SAN JORGE BASIN, ARGENTINA ................................................................ 52 José Matildo Paredes, Nicolás Foix, José Oscar Allard, Ferrán Colombo MORPHOLOGY, FORM ROUGHNESS AND THE ABSENCE OF CHANNEL SCALE SECONDARY FLOWS AT BIFURCATIONS IN A LARGE RIVER ................................ 53 Daniel R. Parsons, J. L. Best, S. N. Lane, R. J. Hardy, O. Orfeo, R. Kostaschuk COHERENT FLOW STRUCTURES OVER ALLUVIAL SAND DUNES REVEALED BY MULTIBEAM ECHO SOUNDING .................................................................... 53 Daniel R. Parsons, J. L Best, S. M Simmons, G. M Keevil, K. Oberg, J. Czuba FLOOD DOMINATED FAN DELTA – CASE STUDY FROM EASTERN SLOVAKIA (MARKUÒOVCE) ...................................................................................... 54 Marta Prekopová, Juraj Janoèko DISTINGUISHING CROSS STRATA FORMED BY DUNES AND UNIT BARS ................ 55 Arnold J.H. Reesink, John, S. Bridge DOES LARGE-SCALE ALLUVIAL MORPHOLOGY CONTROL DUNE-SET PRESERVATION? .... 55 Reesink, A.J.H., Ashworth, P.J., Amsler, M.L., Best, J.L., Hardy, R.J., Lane, S.N., Nicholas, A.P., Orfeo, O., Parsons, D.R., Sambrook Smith, G.H., Sandbach, S.D., and Szupiany, R.N. STRATIGRAPHY AND FLUVIAL ARCHITECTURE OF THE CASTILLO AND BAJO BARREAL FORMATIONS (CRETACEOUS) IN THE SOUTHERN END OF SAN BERNARDO RANGE AND BARRANCA YANKOWSKI, GOLFO SAN JORGE BASIN, CHUBUT AND SANTA CRUZ PROVINCES, ARGENTINA ........................................................ 56 Guillermo A. Richter, Sergio M. Georgieff, Javier G. Sanagua QUANTIFYING THE DYNAMICS OF FLOW WITHIN A PERMEABLE GRAVEL BED USING HIGH-RESOLUTION ENDOSCOPIC PARTICLE IMAGING VELOCIMETRY (PIV) ................ 57 G.H. Sambrook Smith, G. Blois, J. L. Best, R. J. Hardy, J. R. Lead LINKING SURFACE MORPHODYNAMICS AND SUBSURFACE ARCHITECTURE IN BRAIDED RIVERS: NEW INSIGHTS FROM THE SOUTH SASKATCHEWAN RIVER PROJECT 1999-2009 .............................................................................. 57 G. H. Sambrook Smith, N.O. Parker, S.N. Lane, P.J. Ashworth, J.L. Best, I.A. Lunt, J.S. Bridge, C.J. Simpson, R.E. Thomas, P. Widdison FACIES AND ARCHITECTURAL ANALYSIS OF LOWER CRETACEOUS FLUVIAL DEPOSITS IN WEST-CENTRAL ARGENTINA ..................................................... 58 Pablo Nicolás Sandoval 78 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 CHARACTERIZATION OF FLUVIAL GEOFORMS FROM 3D SEISMIC: EXAMPLES FOR CERRO GUADAL NORTE OIL FIELD, CHUBUT GROUP (CRETACEOUS), GOLFO SAN JORGE BASIN, ARGENTINA ................................................................ 58 Agustina Santangelo, Leonor Ferreira, Sergio M. Georgieff SEDIMENTOLOGICAL CHARACTERISTICS OF SUBTROPICAL PLAIN RIVERS IN RELATION WITH THE HYDROLOGICAL CYCLE (CHACO, ARGENTINA) ....................... 59 Carolina Sartirana, Paola A. Suárez SOLID LOAD DYNAMICS IN THE DON AND KUBAN RIVERS, SOUTH RUSSIA: INFLUENCE OF ANTHROPOGENIC AND CLIMATE FACTORS .................................. 59 Vera Sorokina, Sergey Venevsky THE ASYMMETRICAL CHANNEL DEVELOPMENT IN MODERN ALLUVIAL DEPOSITS: NEOTECTONIC EVIDENCES. CUMBRES CALCHAQUÍES RANGES, ARGENTINA ............ 60 José A. Sosa Gómez EVOLUTION OF THE SAN IGNACIO RIVER: AN EXAMPLE OF THE TECTONIC, CLIMATIC AND BASE LEVEL CONTROLS IN THE RIVER DYNAMIC, TUCUMÁN, ARGENTINA ...... 61 José Sosa Gómez, Sergio M. Georgieff COMPARISON OF DEPOSITIONAL DYNAMICS AMONG THE BRAIDED, MEANDERING AND STRAIGHT CHANNEL REACHES IN THE LOWER YELLOW RIVER ...................... 61 Suiji Wang MULTIDISCIPLINARY STUDY OF RÍO QUEQUÉN GRANDE BASIN, ARGENTINA .......... 62 Liliana B. Teruggi, Silvia Sala, Elena Marrochino, María J. Kristensen, Enrica Caporali, Carmela Vaccaro, María A. Casco, Adrian Cefarelli MORPHOLOGICAL AND SEDIMENTARY DYNAMICS OF A SOUTH AFRICAN FLOODPLAIN WETLAND: FROM CHANNELLED TO UNCHANNELLED AND BACK TO CHANNELLED? ....................................................................................... 63 S. Tooth, T.S. McCarthy, H. Rodnight, A. Keen-Zebert, M.D. Rowberry, D. Brandt FLUVIAL REWORKING OF PYROCLASTIC DEPOSITS: THE CRETACEOUS LOWER MEMBER OF THE BAJO BARREAL FORMATION, SAN JORGE BASIN, PATAGONIA, ARGENTINA ........................................................................................... 63 Aldo Martín Umazano, Eduardo Sergio Bellosi, Graciela Visconti, Ricardo Néstor Melchor MULTIPLE-POINT SIMULATION OF CHANNELIZED AND UNCONFINED FLUVIAL DEPOSITS: AN EXPLORATORY MODEL FOR CRETACEOUS OIL-BEARING SANDSTONES OF CENTRAL PATAGONIA ........................................................................... 64 Aldo M. Umazano, Claudio Larriestra, Eduardo S. Bellosi THE EFFECT OF PEAT COMPACTION ON THE EVOLUTION OF ALLUVIAL PLAIN ............ 65 S. van Asselen Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 79 ACCOMMODATION / SEDIMENT SUPPLY FLUVIAL DEPOSITION CONTROLLED BY BASE LEVEL CHANGES AND RELATIVE SEA LEVEL FLUCTUATIONS IN THE MATA AMARILLA FORMATION (EARLY UPPER CRETACEOUS), SOUTHERN PATAGONIA, ARGENTINA ...... 66 Augusto Nicolás Varela 3D COMPUTER-MODELLING OF FLUVIAL DEPOSITS: OUTCROPS STUDIES OF THE LOWER TRONCOSO MEMBER (NEUQUÉN BASIN, ARGENTINA) AND IMPLICATIONS FOR THE CHARACTERISATION OF SUBSURFACE RESERVOIRS .............................. 66 Gonzalo D. Veiga, John A. Howell EPHEMERAL ALLUVIAL SYSTEMS OF THE TERUEL BASIN (MIOCENE, SPAIN): BASINAL AND CLIMATIC CONTROLS ............................................................. 67 Dario Ventra THE ORIGIN OF THE INCISED CHANNELS IN THE UPPER SECTION OF THE PLAYA DEL ZORRO ALLOFORMATION (NEOGENE), EL CAJÓN VALLEY, CATAMARCA – ARGENTINA ....................................................................... 68 María Eugenia Vides, Gerardo E. Bossi ARID CLIMATE FLUVIAL SYSTEMS IN THE SALICAS FORMATION (PLIOCENE), BOLSÓN DE PIPANACO, LA RIOJA, ARGENTINA .............................................. 69 María Eugenia Vides, Gerardo E. Bossi, Sergio M. Georgieff CLAY MINERALS RELATED TO FLUVIAL DYNAMIC. BAJO BARREAL FORMATION. SAN JORGE BASIN, SANTA CRUZ, ARGENTINA ............................................... 69 María Eugenia Vides, Lucía Marina Ibañez, Leonor Ferreira RECONSTRUCTION OF FLOOD EVENTS OVER THE LAST 150 YEARS IN THE LOWER CHANGJIANG VALLEY .............................................................................. 70 Shouye Yang, Wang Zhan, Xiaoli Liu, Jianwei Li 80 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 Instructions for authors SCOPE AND EDITORIAL POLICY words each, containing the title and keywords The Acta geológica li l loana publishes only (maximum of 6 words). original contributions related to geological top- The main text of the manuscript will start ics. 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Invertebrados fósiles. mation of the empirical correlation of Al in EUDEBA, Buenos Aires, 707 pp. hornblende with pressure of solidification of Grosse, P. 2007. Los granitos porfíricos y orbic- calcalkaline plutons. American Mineralogist ulares del sector Centro Oriental de la Sier- 72: 231-239. ra de Velasco: génesis y significación region- Alonso, R. 1992. Estratigrafía del Cenozoico de al. Tesis Doctoral Facultad de Ciencias Exac- la cuenca de Pastos Grandes (Puna salteña) tas y Naturales, Universidad Nacional de con énfasis en la Formación Sijes y sus bo- Córdoba (inédito) 285 p. Córdoba. ratos. Revista de la Asociación Geológica Argentina 47(2): 189-199. Reprints.— before the final publication of the Valencio, D. A. 1973. El significado estratigrá- article, the author will receive a galley proof fico y paleogeográfico de los estudios pale- which should be carefully reviewed and sent omagnéticos de formaciones del Paleozoico back to the Editor ia l Committee with in 2 superior y del Mesozoico inferior de Améri- weeks of reception. Once published in the jour- ca del Sur. V Congreso Geológico Argentino. nal, 30 reprints of the article will be provided Actas 5: 71-79, Buenos Aires. free of charge. Authors may purchase additional Benton. M. J. y Hitchin, R. (en prensa). Testing reprints. the quality of the fossil record by groups For more editorial information: and by major habitats. Historical Biology. www.lillo.org.ar 82 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009 83 84 Acta geo lóg i ca l i l l oana 21 – ISSN 0567-7513 – Sup lemento , 9 th ICFS , 2009