INVESTIGATION OF AQUEOUS PROCESSES IN THE VALLE GRANDE PALEO-LAKE, VALLES CALDERA AS A MARTIAN ANALOG

 The Valle Grande Paleo-lake in the southeastern portion of Valles Caldera, NM, U.S.A. provides a useful location to study short distance source-to-sink variation in geochemistry and mineralogy. In this study, lithium is the primary focus in order to test its effectiveness at recording past environmental change. This is possible due to the ~75 m of lake sediment that has been drilled and cored in this region and the extensive paleo-climate work that has been completed with this material; this has provided a strong understanding of past environmental change throughout the lifespan of the lake. Chemical and mineralogical analyses were conducted in the lake sediment and from source rock material surrounding Valle Grande to understand such changes during the weathering, erosion, and deposition of this material. Finally, as this is a depositional basin dominated by a single type of igneous rock in an arid region, it provides a useful analog to Martian lacustrine settings, such as Gale Crater which also is characterized by a closed depositional basin dominated by an igneous rock type, basalt rather than rhyolite. In the drill core lithium was minimally enriched in the interglacial sediment compared to the glacial; in addition, the trend for lithium with depth was somewhat similar to established climate proxies. However, these changes were not as distinct as the trends seen with the other proxies and the mean values for the two periods investigated were within one standard deviation of each other.