The Curiosity rover is exploring Hesperian-aged stratigraphy in Gale crater, Mars, where a transition from clay-bearing units to a layered sulfate-bearing unit has been interpreted to represent a major environmental transition of unknown character. We present the first description of key facies in the sulfate-bearing unit, recently observed in the distance by the rover, and propose a model for changes in depositional environments. Our results indicate a transition from lacustrine mudstones into thick aeolian deposits, topped by a major deflation surface, above which strata show architectures likely diagnostic of a subaqueous environment. This model offers a reference example of a depositional sequence for layered sulfate-bearing strata, which have been identified from orbit in other locations globally. It differs from the idea of a monotonic Hesperian climate change into long-term aridity on Mars and instead implies a period characterized by multiple transitions between sustained drier and wetter climates.
Alternating wet and dry depositional environments recorded in the stratigraphy of Mount Sharp at Gale crater, Mars
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W. Rapin, G. Dromart, D. Rubin, L. Le Deit, N. Mangold, L.A. Edgar, O. Gasnault, K. Herkenhoff, S. Le Mouélic, R.B. Anderson, S. Maurice, V. Fox, B.L. Ehlmann, J.L. Dickson, R.C. Wiens; Alternating wet and dry depositional environments recorded in the stratigraphy of Mount Sharp at Gale crater, Mars. Geology 2021; doi: https://doi.org/10.1130/G48519.1
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