Browsing by Author "Mariethoz, G"
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- ItemCave monitoring to constrain the paleoclimate interpretation of δ18O proxy in speleothems from semi-arid areas(University of New South Wales and Australian Nuclear Science and Technology Organisation, 2015-07-09) Markowska, M; Baker, AA; Andersen, MS; Jex, CN; Cuthbert, MO; Rau, GC; Graham, PW; Rutlidge, H; Mariethoz, G; Marjo, CE; Treble, PC; Edwards, NNot supplied to the ANSTO Library.
- ItemCave stalagmites as records of past recharge frequency in semi-arid Australia(National Centre for Groundwater Research And Training, 2015-11-03) Markowska, M; Baker, AA; Andersen, MS; Rutlidge, H; Jex, CN; Cuthbert, MO; Rau, GC; Adler, L; Graham, PW; Mariethoz, G; Marjo, CE; Treble, PCUnderstanding past variability in groundwater recharge over recent time scales (0 – 10 ka) in Australia is essential for future sustainable groundwater management in a changing climate. Currently, there are limited data about past infiltration rates and their relationship to environmental controls that dominate recharge variability. Speleothem (cave precipitates) records may provide a new approach to understanding past infiltration (i.e. recharge rates), in addition to traditional interpretations of connectivity between climate and the hydrological cycle, in drier parts of Australia. In this study we used Cathedral Cave, (SE Australia) located in a temperate semi-arid climate, as a natural laboratory to investigate cave infiltration rates and the climate-karst-cave interactions driving the isotopic (δ18O) and chemical variability in modern drip water. These findings were then used to interpret the δ18O stalagmite record from two modern speleothems growing during the last ~50 years. Modern drip water results showed that the δ18O composition was enriched by up to 2.77 ‰ relative to annually weighted mean rainfall. Isotopically lighter δ18O occurred during infiltration events, followed by subsequent isotopic enrichment as evaporation in the unsaturated zone fractionated δ18O of stored water. Drip rate monitoring revealed that larger events leading to infiltration were infrequent (0 – 3 a-1) and the ‘effectiveness’ of these infiltration events was controlled by antecedent moisture conditions in the soil zone. In drier climatic zones, evaporation drives the enrichment of δ18O in the unsaturated zone, allowing periods of infiltration to be identified from the stable isotopic composition of drip waters. Our findings are important for interpreting speleothem records from regions with infrequent recharge and high evaporation rates. Such records are likely to contain evidence of past infiltration events moderated by an evaporation signal, allowing records of paleo-recharge to be reconstructed for drier climate regions of Australia.
- ItemDripwater organic matter and trace element geochemistry in a semi-arid karst environment: Implications for speleothem paleoclimatology(Elsevier, 2014-06-15) Rutlidge, H; Baker, AA; Marjo, CE; Andersen, MS; Graham, PW; Cuthbert, MO; Jex, CN; Rau, GC; Roshan, H; Markowska, M; Mariethoz, GA series of four short-term infiltration experiments which revealed hydrochemical responses relevant to semi-arid karst environments were carried out above Cathedral Cave, Wellington, New South Wales (NSW), Australia. Dripwater samples were collected at two sites for trace element and organic matter analysis. Organic matter was characterised using fluorescence and interpreted using a PARAFAC model. Three components were isolated that represented unprocessed, soil-derived humic-like and fulvic-like material, processed humic/fulvic-like material and tryptophan-like fluorescence. Principal Component Analysis (PCA) performed on the entire dataset comprising trace element concentrations and PARAFAC scores revealed two dominant components that were identified as soil and limestone bedrock. The soil component was assigned based on significant contributions from the PARAFAC scores and additionally included Ba, Cu, Ni and Mg. The bedrock component included the expected elements of Ca, Mg and Sr as well as Si. The same elemental behaviour was observed in recent stalagmite growth collected from the site. Our experiments demonstrate that existing paleoclimate interpretations of speleothem Mg and Sr, developed in regions of positive water balance, are not readily applicable to water limited environments. We provide a new interpretation of trace element signatures unique to speleothems from water limited karst environments. © 2014, Elsevier Ltd.
- ItemEvaporative cooling of speleothem drip water(Nature Publishing Group, 2014-06-04) Cuthbert, MO; Rau, GC; Andersen, MS; Roshan, H; Rutlidge, H; Marjo, CE; Markowska, M; Jex, CN; Graham, PW; Mariethoz, G; Acworth, RI; Baker, AAThis study describes the first use of concurrent high-precision temperature and drip rate monitoring to explore what controls the temperature of speleothem forming drip water. Two contrasting sites, one with fast transient and one with slow constant dripping, in a temperate semi-arid location (Wellington, NSW, Australia), exhibit drip water temperatures which deviate significantly from the cave air temperature. We confirm the hypothesis that evaporative cooling is the dominant, but so far unattributed, control causing significant disequilibrium between drip water and host rock/air temperatures. The amount of cooling is dependent on the drip rate, relative humidity and ventilation. Our results have implications for the interpretation of temperature-sensitive, speleothem climate proxies such as delta O-18, cave microecology and the use of heat as a tracer in karst. Understanding the processes controlling the temperature of speleothem-forming cave drip waters is vital for assessing the reliability of such deposits as archives of climate change. © 2014, Nature Publishing Group.
- ItemA groundwater recharge experiment in krast - Wellington Caves, NSW(International Association of Hydrogeologists, 2013-09-16) Andersen, MS; Baker, AA; Graham, PW; Rutlidge, H; Mariethoz, G; Roshan, H; Rau, GC; Markowska, M; Cuthbert, MOGroundwater recharge is a process which is inherently difficult to measure directly due to soil and sediment heterogeneity and the tendency for this to cause preferential flow. This often leads to groundwater recharge being estimated by indirect methods, such as remotely or by differences in the water balance, which frequently causes huge uncertainties in the estimates. Karst terrains with cave features, although notoriously heterogeneous, offer a rare opportunity to physically enter the subsurface and make direct observations. Cathedral Cave at Wellington Caves in NSW, Australia was used for a multiple tracer experiment to look a recharge processes as well as physical and chemical processes affecting speleothems formation. On four consecutive days, four water releases were applied to a 3 x 7 m soil patch 2-3 m above the cave ceiling. The applications varying from 800 to 1500 L corresponds to natural precipitation events of 40 to 70 mm, events which have been known to cause recharge into the caves in the past. The four different events were variably modified by adding deuterium (2H), a fluorescing tracer and ice to reduce the temperature. Inside the caves onset of recharge was measured by automatic drip rate monitoring and temperature loggers. In addition, discrete water samples were collected and analysed for stable water isotope composition, fluorescence and dissolved trace elements. A preliminary assessment of the cave observations suggest that. although ow was preferentially along fractures, considerable interaction with pore water in the rock matrix must have taken place to significantly dilute the tracer content of water sampled in the cave. To our knowledge this is the first time that is has been directly shown that water sampled during a recharge event is only fractionally water from that particular event. For the location of this study the result is surprising considering the short distance of 2-3 m between the soil surface and the cave ceiling. The results have significant implications for our understanding of karst hydrology as well as reconstruction of past recharge and climate conditions from cave speleothems.
- ItemHydrological characterization of cave drip waters in a porous limestone: Golgotha Cave, Western Australia(Copernicus Publications, 2018-02-06) Mohmud, K; Mariethoz, G; Baker, AA; Treble, PCCave drip water response to surface meteorological conditions is complex due to the heterogeneity of water movement in the karst unsaturated zone. Previous studies have focused on the monitoring of fractured rock limestones that have little or no primary porosity. In this study, we aim to further understand infiltration water hydrology in the Tamala Limestone of SW Australia, which is Quaternary aeolianite with primary porosity. We build on our previous studies of the Golgotha Cave system and utilize the existing spatial survey of 29 automated cave drip loggers and a lidar-based flow classification scheme, conducted in the two main chambers of this cave. We find that a daily sampling frequency at our cave site optimizes the capture of drip variability with the least possible sampling artifacts. With the optimum sampling frequency, most of the drip sites show persistent autocorrelation for at least a month, typically much longer, indicating ample storage of water feeding all stalactites investigated. Drip discharge histograms are highly variable, showing sometimes multimodal distributions. Histogram skewness is shown to relate to the wetter-than-average 2013 hydrological year and modality is affected by seasonality. The hydrological classification scheme with respect to mean discharge and the flow variation can distinguish between groundwater flow types in limestones with primary porosity, and the technique could be used to characterize different karst flow paths when high-frequency automated drip logger data are available. We observe little difference in the coefficient of variation (COV) between flow classification types, probably reflecting the ample storage due to the dominance of primary porosity at this cave site. Moreover, we do not find any relationship between drip variability and discharge within similar flow type. Finally, a combination of multidimensional scaling (MDS) and clustering by k means is used to classify similar drip types based on time series analysis. This clustering reveals four unique drip regimes which agree with previous flow type classification for this site. It highlights a spatial homogeneity in drip types in one cave chamber, and spatial heterogeneity in the other, which is in agreement with our understanding of cave chamber morphology and lithology. © Author(s) 2018
- ItemLidar investigation of infiltration water heterogeneity in the Tamala Limestone(American Geophysical Union, 2014-12-15) Mahmud, K; Mariethoz, G; Teble, PC; Baker, AATo better manage groundwater resources in carbonate areas and improve our understanding of speleothem archives, it is important to understand and predict unsaturated zone hydrology in karst. The high level of complexity and spatial heterogeneity of such systems is challenging and requires knowledge of the typical geometry of karstic features. We present an exhaustive characterization of Golgotha Cave, SW Western Australia, based on an extensive LIDAR measurement campaign. The cave is developed in Quaternary age aeolianite (dune limestone) and contains speleothem records. We collect 30 representative 3D scan images from this site using FARO Focus3D, a high-speed 3D laser scanner, to visualize, study and extract 2D and 3D information from various points of view and at different scales. In addition to LIDAR data, 32 automatic drip loggers are installed at this site to measure the distribution and volume of water flow. We perform mathematical morphological analyses on the cave ceiling, to determine statistical information regarding the stalactites widths, lengths and spatial distribution. We determine a relationship between stalactites diameter and length. We perform tests for randomness to investigate the relationship between stalactite distribution and ceiling features such as fractures and apply this to identify different types of possible flow patterns such as fracture flow, solution pipe flow, primary matrix flow etc. We also relate stalactites density variation with topography of the cave ceiling which shows hydraulic gradient deviations. Finally we use Image Quilting, one of the recently developed multiple-point geostatistics methods, with the training images derived from LIDAR data to create a larger cave system to represent not only the caves that are visible, but the entire system which is inaccessible. As a result, an integral geological model is generated which may allow other scientists, geologist, to work on two different levels, integrating different speleothem datasets: (1) a basic level based on the accurate and metric support provided by the laser scanner; and (2) an advanced level using the image-based modelling.
- ItemRoles of transpiration, forest bioproductivity and fire on a long-term dripwater hydrochemistry dataset from Golgotha Cave, SW Australia(American Geophysical Union (AGU), 2015-12-15) Treble, PC; Baker, AA; Fairchild, IJ; Bradley, C; Mahmud, K; Andersen, MS; Meredith, KT; Mariethoz, GGolgotha Cave is located in a forested catchment in SW Australia where evapotranspiration losses from the vadose-zone are high and forest biomass has been disturbed by fire. The cave has been continuously monitored since 2005 and this extensive dataset has been used to quantify key processes determining dripwater hydrology and chemistry (Mahmud et al., 2015; Treble et al., 2013; 2015). In this paper we present a synthesis of these findings and derive a conceptual model to illustrate the main hydrochemical processes that will impact cave dripwater in similar environments. We applied mass-balance techniques to quantify sources (water/rock interactions and aerosol) and sinks (prior calcite precipitation and biomass uptake). Mass-balance results suggest that transpiration and elemental sequestration into biomass modifies dripwater ion concentrations. The vegetation uptake impacts dripwater Mg, K and SO4, with the largest impact on SO4, estimated to be up to 60% at some drip sites. Overall, our findings suggest that varying amounts of transpiration by deeply-rooted trees contribute significantly to spatial and temporal variability in dripwater solute concentrations. This is in addition to the partitioning of infiltrating water between characteristic flow pathways. Applying principal components analysis, we identify a common long-term rising trend in dripwater Cl, Mg, K, Ca, Sr and Si. We assess whether the long-term trends in dripwater solutes are driven by post-fire biomass recovery and/or the impacts of a drying climate in SW Australia. References Mahmud et al. (2015), Terrestrial Lidar Survey and Morphological Analysis to Identify Infiltration Properties in the Tamala Limestone, Western Australia, doi:10.1109/JSTARS.2015.2451088. Treble et al. (2013), An isotopic and modelling study of flow paths and storage in Quaternary calcarenite, doi:10.1016/J.Quascirev.2012.12.015. Treble et al. (2015), Impacts of cave air ventilation and in-cave prior calcite precipitation on Golgotha Cave dripwater chemistry, doi:10.1016/J.Quascirev.2015.06.001.
- ItemSemi-arid zone caves: evaporation and hydrological controls on δ18O drip water composition and implications for speleothem paleoclimate reconstructions(Elsevier B.V., 2016-01-01) Markowska, M; Baker, AA; Andersen, MS; Jex, CN; Cuthbert, MO; Rau, GC; Graham, PW; Rutlidge, H; Mariethoz, G; Marjo, CE; Treble, PC; Edwards, NOxygen isotope ratios in speleothems may be affected by external processes that are independent of climate, such as karst hydrology and kinetic fractionation. Consequently, there has been a shift towards characterising and understanding these processes through cave monitoring studies, particularly focussing on temperate zones where precipitation exceeds evapotranspiration. Here, we investigate oxygen isotope systematics at Wellington Caves in semi-arid, SE Australia, where evapotranspiration exceeds precipitation. We use a novel D2O isotopic tracer in a series of artificial irrigations, supplemented by pre-irrigation data comprised four years of drip monitoring and three years of stable isotope analysis of both drip waters and rainfall. This study reveals that: (1) evaporative processes in the unsaturated zone dominate the isotopic composition of drip waters; (2) significant soil zone ‘wetting up’ is required to overcome soil moisture deficits in order to achieve infiltration, which is highly dependent on antecedent hydro-climatic conditions; (3) lateral flow, preferential flow and sorption in the soil zone are important in redistributing subsurface zone water; (4) isotopic breakthrough curves suggest clear evidence of piston-flow at some drip sites where an older front of water discharged prior to artificial irrigation water; and (5) water residence times in a shallow vadose zone (<2 m) are highly variable and can exceed six months. Oxygen isotope speleothem records from semi-arid regions are therefore more likely to contain archives of alternating paleo-aridity and paleo-recharge, rather than paleo-rainfall e.g. the amount effect or mean annual. Speleothem-forming drip waters will be dominated by evaporative enrichment, up to ∼3‰ in the context of this study, relative to precipitation-weighted mean annual rainfall. The oxygen isotope variability of such coeval records may further be influenced by flow path and storage in the unsaturated zone that is not only drip specific but also influenced by internal cave climatic conditions, which may vary spatially in the cave.© 2015, Elsevier Ltd.
- ItemTerrestrial LiDAR survey and morphological analysis to identify infiltration properties in the Tamala Limestone, Western Australia(IEEE, 2015-07-16) Mahmud, K; Mariethoz, G; Treble, PC; Baker, AACaves are an ideal observatory of infiltration water in karstified limestone, and the application of remote sensing techniques can bring new insights toward flow patterns and processes. We present an exhaustive characterization of Golgotha Cave in SW Western Australia, based on a light detection and ranging (LiDAR) measurement campaign. The cave is developed in Quaternary age aeolianite (dune limestone) and its infiltration waters form speleothems. We collect ground-based LiDAR scans of the cave ceiling at three sites within the cave system. The resulting point-clouds are analyzed using mathematical morphology to determine statistical information on stalactite widths, lengths, and spatial distributions. We establish a relationship between stalactite diameter and length that is in agreement with the platonic ideal of stalactite shape. We relate stalactite density variation with topography of the cave ceiling and variations in hydraulic gradient. From this analysis, it appears that longer stalactites tend to occur in comparatively lower ceiling elevation, which, we hypothesize, represents greater mass of water in the limestone above the roof of the cave. We also investigate the relationship between stalactite distribution and ceiling features such as fractures. We apply this to identify different types of possible flow patterns such as matrix flow and fracture flow. This analysis demonstrates a spatial variability, with one site having linear groups of stalactites and another site mostly dominated by stalactite clusters. © 2015, IEEE.
- ItemWlCount: geological lamination detection and counting using an image analysis approach(Elsevier, 2022-03) Oriani, F; Treble, PC; Baker, AA; Mariethoz, GThe manual identification and count of laminae in layered textures is a common practice in the study of geological records, which can be time consuming and carry large uncertainty for dense or disturbed lamina textures. We present here a novel image analysis approach to detect and count laminae in geoscientific imagery, called WlCount. Based on Dynamic Time Warping and Wavelet analysis, WlCount firstly aligns persistent vertical elements to increase the continuity of the lamina structure. Then, using a graphical interface, the user extracts the most significant signal frequencies and allows the automatic count of the laminae. The software, tested on a series of stalagmite cut images showing different types of laminations and a tree-ring image, provides an estimation of the laminae detection and count comparable to the manual one. WlCount presents as a useful open-source tool to help geoscientists, sensibly speeding up the lamination count process. © 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license.