PRELIMINARY MAPPING OF LATERALLY EXTENSIVE PHYLLOSILICATES IN THE WEST MARGARITIFER PLATEAU REGION OF MARS

Occurrences of clay minerals found in stratigraphic sequences have been used to support the idea of widespread precipitation and pedogenic weathering during a warmer, wetter climate era on early Mars. These sequences have been identified in several geographic provinces: along the walls of and plains surrounding Valles Marineris, Mawrth Vallis, Terra Sirenum, northern Hellas, and Nili Fossae. The intent of this study is to map and characterize an additional regionally extensive layer of near-surface phyllosilicate-bearing material exposed on the plateaus in West Margaritifer Terra, possibly connecting the sequences exposed in eastern Valles Marineris and NW Noachis Terra with those in Mawrth Vallis/Arabia Terra. West Margaritifer has experienced a complex geologic history, including formation of chaos terrains and dissection by the Morava and Ares Valles outflow channels. These large scale aqueous events allow for the possibility of alternate phyllosilicate emplacement mechanisms besides pedogenesis, including floodplain deposition and subsurface (groundwater) alteration. We will report on progress using Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) multispectral visible/near infrared mapping data together with Thermal Emission Imaging System (THEMIS) thermal inertia data to identify and delineate outcrops of the clay-bearing unit. Analyses of CRISM hyperspectral targeted data provide information on specific phyllosilicate and associated mineral phases. Finally, topographic and morphologic relationships will be assessed in order to understand the geologic context and emplacement of this terrain, and how it might relate to other layered phyllosilicate deposits. The West Margaritifer and other similar layered phyllosilicates were formed under particular paleoclimatic and geologic conditions that may have once been prevalent regionally, if not globally; understanding these conditions is key for deciphering the planet’s overall history of water and habitability potential.