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Physical Sedimentology in Gale Crater, Mars


Gale crater was selected as the Mars Science Laboratory landing site largely because remote images suggested the crater contains a thick sequence of sedimentary rocks interpreted to be eolian, fluvial, and lacustrine deposits (previous work summarized by Anderson and Bell, 2010). In the year since landing, the rover, Curiosity, identified and examined deposits of all three of these depositional environments. Eolian deposits examined by Curiosity include the Rocknest sand shadow (unconsolidated sand in the lee of rocks on the surface described by Blake et al. in press) and thin sandstones beds with pinstripe laminae deposited by migrating wind ripples. On its route to Mt. Sharp, it is likely that the rover will pass near active eolian dunes and “washboard” deposits that have previously been interpreted as preserved eolian dunes. Fluvial deposits examined by Curiosity include both conglomerates and sandstones. The conglomerates have textures of fluvial conglomerates and contain rounded pebbles indicating substantial abrasion (Williams et al. 2013). The fluvial sandstones are cross-bedded (including compound cross-bedding), with dip directions indicating transport generally toward the southeast (toward Mt. Sharp rather than away from it). Fractures interpreted to be desiccation cracks and interbedded eolian (pinstriped) sandstones suggest that fluvial activity alternated with dry, windy, periods. Curiosity also examined deposits interpreted as distal fluvial or lacustrine mudstones (Sheepbed mudstone) at a location that is topographically lower than the fluvial sandstones and conglomerates. That unit is discussed in other abstracts in this session. References Anderson, R.B. and Bell, J.F. III, 2010, Geologic mapping and characterization of Gale Crater and implications for its potential as a Mars Science Laboratory landing site: Mars 5, 76-128. Blake, D.F. in press, Curiosity at Gale crater, Mars: characterization and analysis of the Rocknest sand shadow: Science. Williams, R.M.E. et al. 2013, Martian fluvial conglomerates at Gale Crater: Science, 340, 1068-1072.