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Published June 12, 2013 | Published
Journal Article Open

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

Abstract

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.

Additional Information

© 2013 American Geophysical Union. Received 12 December 2012; revised 10 May 2013; accepted 17 May 2013; published 12 June 2013. Parts of the research presented here were completed as part of a reading seminar at Caltech. We thank group participants for valuable discussions, especially Edwin Kite, Melissa Rice, Kirsten Siebach, Katie Stack, and Mathieu Lapotre. We thank John Grotzinger, Joel Hurowitz, and Ralph Milliken for their insight and helpful comments. Thoughtful reviews by Devon Burr, Nicolas Mangold, and an anonymous reviewer helped improve an earlier version of the manuscript. Funding for this work was provided by NSF (grant OCE-1233685 to MPL), NASA (grant 12PGG120107 to MPL) and the California Institute of Technology (WWF, MPL, and RAD).

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