Sedimentary architecture of the Stimson Formation at the Naukluft plateau, Gale crater, Mars

Abstract: Sedimentary architecture and texture can be used to reconstruct the palaeoenvironment under which the sediment accumulated. On Mars palaeoenvironmental reconstructions can be used to understand the ancient Martian atmospheric circulation, surface sedimentary processes, and presence of water to provide insight into ancient habitability and climate evolution. Exploration of the Naukluft plateau, Gale crater, by the MSL rover Curiosity yielded evidence of aeolian dunes within the strata, and that the Stimson formation unconformably overlies the older lacustrine Murray formation. Analysis of the strata unveiled a hierarchy of bounding surfaces forming compound cross-bedding, indicating two scales of bedform: primary dunes (draa) and superimposed dunes. Cross-set dip-azimuth indicate a broad the sediment transport direction toward the north, aligning with a north or north-east transport direction of previous work . Paired with textural analysis, the outcrops of Naukluft plateau are interpreted to have formed within the central section of a large, dry aeolian dune field. Concretions, veins and alteration halos, all formed by diagenesis or fracturing associated with sub-surface fluids, that coincide with the lithification of the Stimson formation. This hints toward extended presence of water within Gale crater, but at a much lower abundance than earlier in the crater fill sequence. The unconformity demarks a large climatic transition from the lacustrine Murray formation to dry aeolian Stimson formation, that reflects long-term drying of the environmnent. Such observations enhance the understanding of the ancient Martian environment, allowing reconstructions of atmospheric conditions, climate and habitability on a regional scale.