Groundwater Connectivity and Buffering in Western Australian Hypersaline Lakes: Implications for Late‐Stage Martian Lacustrine Systems

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Abstract
Thousands of saline to hypersaline lakes exist across the Yilgarn Craton in Western Australia, representing potential Mars analogs with diverse and varying salinity, pH, and oxygen conditions that remain poorly constrained. Here, we report geochemical trends in lake waters that vary across wet‐dry cycles as well as with regional location and geomorphic setting within the craton's paleovalley system. We identify two different geochemical regimes: (a) lakes where groundwater is more acidic than lake water, and shifts in composition reflect changing precipitation, and (b) lakes that are more acidic than local groundwater due to subsurface and surface geochemical interactions. Elevated salinity in all lakes relative to groundwater occurs due to cyclic evaporation driven by strong seasonal forcing. Most lakes occupy shallow, surficial basins that lack exposed outcrops. Lakes that are deeply incised expose truncated lateritic profiles dominated by clay minerals, quartz veins, and Fe‐oxides. These contrasting settings represent geologic and geochemical endmembers across the region, for which interactions between evaporative concentration and acidic groundwater shape the geochemical evolution of lake systems differently. These factors, in turn, influence microbial habitability, the deposition of salts and other surficial indicators of environmental change. Our observations reveal visible signatures of prolonged acidic‐groundwater interactions, including features consistent with Fe redox cycling, and recurring wet‐dry cycles. These findings suggest that paleodrainage systems within and near craters in Mars' Terra Sirenum, which host similar layered and bleached Al‐rich clay outcrops with smaller exposures of acidic weathered minerals, may record evaporitic concentration and potentially long‐duration groundwater interactions.
Funding Information
  • National Aeronautics and Space Administration (80NSSC22K1409)
  • National Aeronautics and Space Administration (80NM0018D0004)

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