Deltaic deposits at Aeolis Dorsa: Sedimentary evidence for a standing body of water on the northern plains of Mars

Authors

  • Roman A. DiBiase,

    Corresponding author
    1. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
    • Corresponding author: R. A. DiBiase, Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA. (rdibiase@caltech.edu)

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  • Ajay B. Limaye,

    1. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
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  • Joel S. Scheingross,

    1. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
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  • Woodward W. Fischer,

    1. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
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  • Michael P. Lamb

    1. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
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Abstract

[1] A fundamental long-standing question regarding Mars history is whether the flat and low-lying northern plains ever hosted an ocean. The best opportunity to solve this problem is provided by stratigraphic observations of sedimentary deposits onlapping the crustal dichotomy. Here, we use high-resolution imagery and topography to analyze a branching network of inverted channel and channel lobe deposits in the Aeolis Dorsa region, just north of the dichotomy boundary. Observations of stacked, cross-cutting channel bodies and stratal geometries indicate that these landforms represent exhumed distributary channel deposits. Observations of depositional trunk feeder channel bodies, a lack of evidence for past topographic confinement, channel avulsions at similar elevations, and the presence of a strong break in dip slope between topset and foreset beds suggest that this distributary system was most likely a delta, rather than an alluvial fan or submarine fan. Sediment transport calculations using both measured and derived channel geometries indicate a minimum delta deposition time on the order of 400 years. The location of this delta within a thick and widespread clastic wedge abutting the crustal dichotomy boundary, unconfined by any observable craters, suggests a standing body of water potentially 105 km2 in extent or greater and is spatially consistent with hypotheses for a northern ocean.

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