Collaborative Research: The Evolution of Extremely Acid Lakes and Groundwaters in Western Australia

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Acid and neutral saline lake and groundwater systems on the Yilgarn Craton in southern Western Australia represent a rare modern extreme environment type. These natural systems are characterized by waters with a pH range from 1.5 to 10.5 and diverse chemical composition, as well as by an unusual assemblage of depositional and diagenetic minerals, and novel extremophilic microorganisms. PIs will conduct a drilling project that will provide the first intact and complete samples of Quaternary and late Tertiary sediments from these extreme environments. Past surface and subsurface histories will be interpreted from sedimentological, mineralogical, and palynological studies of these cores. Temperatures, pHs, and chemical compositions of past surface water and groundwater will be determined by fluid inclusions in bedded and displacive halite and gypsum and stable isotopes in gypsum, alunite, and jarosite. Identification of palynomorphs and dating of organic-rich siliciclastics and diagenetic minerals will constrain ages. Any suspect microbial remains will be described and will undergo preliminary study. Data from ten cores from throughout the Yilgarn Craton will yield: (1) past depositional environments; (2) past lake water and groundwater chemistry and pH; and (3) past surface water temperatures, which serve as surface air temperature proxies, through the Quaternary for southern Western Australia. This research will document the evolution of these acid saline waters and their response to and from local, regional, and global geological processes. The recognition of past extreme environments in the rock record of Earth and Mars will be evaluated with this work. Finally, PIs will use these results to make predictions about the future evolution of acid saline waters in Western Australia, where it threatens farming, ranching, and even human habitation.