P43B-2116
Sedimentary Facies as Indicators of Changing Lake Levels in Gale Crater, Mars

Thursday, 17 December 2015
Poster Hall (Moscone South)
David M Rubin, University of California-Santa Cruz, Santa Cruz, CA, United States, John P Grotzinger, California Institute of Technology, Pasadena, CA, United States, Sanjeev Gupta, Imperial College London, London, United Kingdom, Dawn Y Sumner, University of California, Davis, Earth and Planetary Sciences, Davis, CA, United States, Rebecca M. E. Williams, Planetary Science Institute Tucson, Tucson, AZ, United States, William E Dietrich, University of California Berkeley, Berkeley, CA, United States, Lauren A Edgar, USGS Astrogeology Science Center, Flagstaff, AZ, United States, Kevin W Lewis, Johns Hopkins University, Baltimore, MD, United States, Dorothy Z Oehler, Johnson Space Center, Houston, TX, United States, Melissa S Rice, Western Washington University, Bellingham, WA, United States, Juergen Schieber, Indiana University Bloomington, Bloomington, IN, United States, Kathryn Stack, NASA Jet Propulsion Laboratory, Pasadena, CA, United States and MSL Science Team
Abstract:
The rover, Curiosity, has observed a variety of sediment deposits that record changing lake levels in Gale crater: (1) conglomerates and sandstones deposited by rivers flowing south from the crater rim toward Mt. Sharp; (2) sandstone and conglomerate beds inclined southward toward Mt. Sharp, interpreted as clinoforms deposited at shallow depths by small deltas advancing into a lake; the small scale of the clinoforms suggest that the lake was shallow and/or lake level fluctuated too quickly for clinoforms to advance into deep water; (3) relatively thin sandstone beds that contain sets of cross-beds that reverse in dip between north and south and that truncate and are draped over eroded clinoform foreset beds; these beds are interpreted to have been deposited by small eolian dunes when lake levels were low; (4) centimeter-scale flat-lying cyclic strata that are interpreted as annual depositional cycles (varves) in relatively still water; (5) and a variety of facies that formed along a widespread erosional surface.

Even without considering all the stratigraphic complexities, distribution of these various deposits indicates changes in lake level. Eolian deposits truncating clinoforms record falling lake levels, and lake deposits that occur at higher elevation than fluvial or eolian deposits record rising lake levels.

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