PRELIMINARY ANALYSES OF NEW ACID SALINE LAKE CORES IN WESTERN AUSTRALIA: SEDIMENTOLOGICAL, PALYNOLOGICAL, MINERALOGICAL, AND GEOCHEMICAL ANALYSIS OF SPATIAL AND TEMPORAL ENVIRONMENTAL CHANGES IN EXTREME ENVIRONMENTS

Acid saline lakes in southern Western Australia exhibit an extreme range in pH (1.5-10.5), salinity, and associated sedimentary mineralogy and geochemistry. Ten new cores were drilled into saline lake basins in January and February of 2009, targeting a variety of lake types based on previous studies of lake and groundwater chemistry, sedimentary mineralogy and geochemistry, and host rocks lithology. The cores exhibit a range of different lithofacies and diagenetic characteristics with depth reflecting changes in both the depositional conditions and subsequent groundwater chemistry over time and space. Sediment thickness and depth to the underlying bedrock in the modern lake basins ranges from less than two meters to over 60 m, and contacts between sediment and bedrock show differences in weathering and regolith composition in different areas. In some of the cores, it is difficult to distinguish between grains that have been weathered in situ versus grains that have been transported and exposed to depositional processes. Preliminary sedimentological analyses reveal a mixture of lithofacies including peat and soft coal, clay, clayey siltstone, gypsum sand, quartz sand and gravel, bottom-growth gypsum, and halite. These sediments exhibit laminated bedding, lenticular bedding, various types of cracks, root features, disseminated pyrite nodules, multicolored mottling and banding, iron oxide-cemented lithic gravels, and abundant iron oxide concretions in the subsurface. Preliminary palynological analyses suggest that the base of the deepest core contains sediments that are Late Eocene in age, and future work will constrain whether deposition has been continuous or has experienced hiatuses over time. Examination of the depositional and diagenetic features, detrital and authigenic mineralogy, geochemistry, and palynomorph and palynofacies analyses will be used to explore how these environments have changed through time and space and will provide insights into the processes leading to the formation of extremely acid hypersaline lake systems.