Browsing by Author "García, A"

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    Lake Carpentaria
    (Geological Survey of Queensland, 2013-01-01) Chivas, AR; García, A; Cendón, DI
    The modern drainage catchment of the Gulf of Carpentaria (Figure 9.2) comprises more than 25 monsoon-fed rivers that collectively provide 25% of the total fluvial run-off of the Australian continent (Figure 9.12). The Gulf is bounded to the east by Torress Strait(maximum water depth 12m) and by the Arafura Sill (water depth 53 m) to the west. The deepest, eastern central portion of the Gulf today is 71 m (Figure 9.13). Accordingly, during episodes of low Quaternary sea levels, the Gulf was separated from the open waters of the Indian and Pacific Oceans and formed the large freshwater-brackish Lake Carpentaria (Torgersen et al. 1983, 1985, 1988; Jones & Torgersen 1988). When most recently filled, the lake had a maximum depth of 15-18m and the lateral dimensions of about 600 x 300K, with overflow westwards into the Arafura Sea (Chivas et al. 2001). Among modern lakes, only the Caspian Sea has a larger surface area. Throughout the past glacial cycle of -125 000 years, there was at least one land bridge between Australia and New Guinea for more than 90% of this time. © 2013, Queensland Government.
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    Non-marine evaporites with both inherited marine and continental signatures: the Gulf of Carpentaria, Australia, at similar ~ 70 ka
    (Elsevier, 2007-10-15) Playà, E; Cendón, DI; Trave, A; Chivas, AR; García, A
    Changes in sea-level and associated climatic fluctuations resulted in extreme and cyclic changes in depositional environments in the Gulf of Carpentaria region (N. Australia). Disconnection from the sea led to the establishment of a "Lake Carpentaria", perched above sea-level. In this environment, evaporitic conditions at about 70 ka produced a repetitive alternation of Pm to mm-thick evaporitic and micritic laminae with a varve-like appearance. These precipitates are interpreted as primary features, deposited in a shallow lake that retained limited water in its centre (core MD-32). Elemental and isotope geochemistry of gypsum and micrite laminae show a complex evaporitic environment where initially marine waters evaporated with the input of continental waters compensating for evaporative losses. Reduced continental input could not support a lake of the initial dimensions and the lake contracted to the deepest part of the basin along the north-eastern side of the basin. In a lake with smaller water volume, continental solutes became apparent. While Sr contents and sulfur isotopes indicate marine contributions, strontium isotopes and oxygen isotopes in sulfates reveal continental inputs and other processes such as recycling of previously precipitated evaporites, sulfate reduction and potential reservoir effects. Carbonate- delta C-13 and delta O-18 values in micritic levels also reveal a continental influence and perhaps variations in organic matter signatures associated with climatic variations and vegetation changes. The REE-normalized patterns in gypsum samples are like those found in northern Cape York rivers, restricting the potential continental inputs into the evaporatic basin to a limited geographical area. The small depletion in LREE-normalized patterns between gypsum and river samples is interpreted as a marine influence while depletions in HREE are considered to be the result of fractionation of HREE during gypsum crystallization. © 2007, Elsevier Ltd.
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    The sedimentary record of palaeoenvironments and sea-level change in the Gulf of Carpentaria, Australia, through the last glacial cycle
    (Elsevier, 2008-05-15) Reeves, JM; Chivas, AR; García, A; Holt, S; Couapel, MJJ; Jones, BG; Cendón, DI; Fink, D
    Environmental evolution of the Gulf of Carpentaria region, the world's largest tropical epicontinental seaway, through the last glacial cycle has been determined from a series of six sediment cores. These cores form the focus of a multi-disciplinary study to elucidate sea level, climate and environmental change in the region. The sedimentary record reveals a series of facies including open shallow marine, marginal marine, estuarine, lacustrine and subaerial exposure, throughout the extent of the basin during this period. The partial or complete closure of the central basin from marine waters results from sea level falling below the height of one or both of the sills that border the Gulf—the Arafura Sill to the west (53 m below present sea level (bpsl)) and Torres Strait to the east (12 m bpsl). The extent and timing of these closures, and restriction of the shallow waterbody within, are intrinsic to local ocean circulation, available latent heat transport and the movement of people and animals between Australia and New Guinea. Whilst the occurrence of the palaeo-Lake Carpentaria has previously been identified, this study expands on the hydrological conditions of the lacustrine phases and extends the record through the Last Interglacial, detailing the previous sea-level highstand (MIS 5.5) and subsequent retreat. When sea levels were low during the MIS 6 glacial period, the Gulf was largely subaerially exposed and traversed by meandering rivers. The MIS 5 transgression (∼130 ka BP) led to marine then alternating marine/estuarine conditions through to MIS 4 (∼70 ka BP) when a protracted lacustrine phase, of varying salinity and depth/area, and including periods of near desiccation, persisted until about 12.2 cal ka BP. The lake expanded to near maximum size (∼190 000 km2) following the intensification/restoration of the Australian monsoon at 14 ka BP. This lake-full phase was short-lived, as by 12.2 cal ka BP, marine waters were entering the basin, coincident with the progressive sea-level rise. Fully marine conditions were restored by about 10.5 cal ka BP by westward connection to the Arafura Sea (Indian Ocean), whereas connections to the Pacific Ocean (Coral Sea) did not occur until about 8 cal ka BP. © 2007 Elsevier Ltd and INQUA.
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    Using multiple geochemical proxies to trace origin of gypsum (Gulf of Carpentaria, Australia, -70ka)
    (Sociedad Geologica de Espana, 2007-05) Playà, E; Cendón, DI; Trave, A; Chivas, AR; García, A
    This paper discusses the geochemical signature of the Carpentaria evaporitic levels using minor-trace and rare-earth elements (REE) and Sr, O, C and S isotopes. The chemistry of these evaporites reveals important criteria for distinguishing between ancient marine and non-marine evaporites. © 2007 Sociedad Geologica de Espana