Abstract
Drive east along the Northshore Road of Lake Mead, then turnoff on the Bitter Spring Road and into Echo Wash. Head northwest and, once you break through the gap in the Bitter Ridge, you've entered the White Basin. Strip this basin of its vegetation and you have entered a landscape that feels like Gale Crater on Mars. The late Miocene Lovell Wash Member of the Horse Spring Formation-with coarse clastics, marls, evaporites, and limestones-dominates the geology of the basin. These continental sediments formed in a mixed fluvio-lacustrine setting under extremely harsh environmental conditions: very little in the way of macrofossils exist in these sediments, suggesting an inhospitable setting for most life. This is particularly true for the limestones, deposited in highly alkaline, shallow lakes and influenced by hydrothermal activity. A rich diversity of microbial macro-, meso-, and microstructures characterize one thin (1-5 m) limestone interval with large lateral extent ( approximately 12 km). We have investigated the microbial morphologies, textures, and geochemistry of this interval within its detailed stratigraphic context, thereby providing a truly unique insight into microbial carbonate deposition in an arid lake setting. We argue that this could be one of the best Earth analogs for a Martian lake system like that found at Gale Crater and, hopefully, in the areas currently being explored by Perseverance. In this poster we will present new stable isotopic and geochemical data, tied to morphological and textural properties of the numerous stromatolites and thrombolites of this interval. These data raise important questions about the relative roles of lake chemistry, paleoclimate, and microbial metabolisms on the preserved microbial signal in lacustrine carbonates globally and, especially, on other planets.