Deltaic deposits indicative of a paleo-coastline at Aeolis Dorsa, Mars
2019
Abstract Recent work at Aeolis Dorsa, Mars has identified exposure of
fluvialsedimentary
outcropdeposited early in martian history, likely during the late
Hesperianor earlier. Here, we examine a ∼1200 km 2 exposure of sedimentary
outcropin southeast Aeolis Dorsa. Total thickness of the
stratigraphic sectionexceeds 100 m. We identify eight discrete complexes, each of which is primarily composed of branching channel-filling
fluvialdeposits associated with a primary feeder, or trunk, channel deposit. Relative ages for the branching complexes are derived from observed stacking relationships, and there is a pattern of eastward younging. Using
digital elevation modelsderived from Context Camera (CTX) stereo pair images, we measure the
strikeand
dipof stratal
surfaces mappedthroughout the study area. There is a trend of increasing dip magnitude from north to south. The branching complexes are interpreted as exhumed remnants of the lobes of an
aggrading
river deltathat shifted its depo-center from west to east over time. The increasing dip magnitude of stratal surfaces towards the south records topset-foreset transitions, an architectural feature associated with
river deltas, and indicates paleo-transport was locally southward. The interpreted deltaic lobes indicate that Aeolis Dorsa was a coastal region not presently bound by a modern crater basin, and the studied
outcropis part of a larger set of coastal sedimentary deposits identified in the region.
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