Sedimentary Architecture of the Stimson Formation at the Naukluft Plateau, Gale Crater, Mars

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