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

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 10 5 km 2 in extent or greater and is spatially consistent with hypotheses for a northern ocean.

The imprint of atmospheric evolution in the D/H of Hesperian clay minerals on Mars

“…The method involves determining volume mixing ratios for each spectral line and comparing with those calculated using the HITRAN 2012 database (49) for the same conditions of pressure, temperature, path length, spectral laser width, etc. The comparison is made between the integrated areas of the lines to generate mixing ratios of each isotopic component that are then compared to produce isotope ratios.…”

A Field Guide to Finding Fossils on Mars

“…Orbital data reveal fluvial valley networks draining thousands of square kilometers, exhumed meandering and branched distributary channels, paleolake deposits in topographic depressions, and alluvial fans/deltas entering these lakes, all of which reflect sustained precipitation and subaqueous sediment transport during the Noachian and Hesperian periods (Cabrol & Grin, ; Fassett & Head, ; Goudge et al, ; Grant et al, ; Grotzinger, Gupta, et al, ; Malin & Edgett, ; Metz et al, ; Moore & Howard, ). Some fan‐shaped deposits, possibly deltaic, have been interpreted as aligned along the shoreline of a large ocean (Di Achille & Hynek, ; DiBiase et al, ) that would have covered the northern lowlands, although this is controversial. At Gale Crater, however, the Mars Science Laboratory mission (Curiosity rover) has explored the sedimentary record of a Late Noachian/Early Hesperian paleolake that persisted for thousands to millions of years, with evidence for mild salinity, moderate pH, and local redox gradients (Grotzinger et al, ; Grotzinger, Gupta, et al, ; Hurowitz et al, ).…”

Avulsion cycles and their stratigraphic signature on an experimental backwater‐controlled delta

“…Moreover, river avulsions present a serious hazard to communities living on deltas worldwide, and understanding their mechanics is vital for sustainable management of deltas, and forecasting deltaic evolution in the face of sea level rise, river engineering, and land use changes upstream of river deltas. From a stratigraphic viewpoint, river avulsions control the distribution of sediment and the stacking patterns of channel bodies in the subsurface [e.g., Allen , ; Bridge and Mackey , ; Mackey and Bridge , ; Mohrig et al , ; Hajek et al , ], and thus are of significant importance for unraveling the mechanics of ancient deltaic systems [e.g., Paola , ; Kleinhans , ; Bianchi and Allison , ; DiBiase et al , ], and for characterization of aquifers and hydrocarbon reservoirs [ Bohacs and Suter , ; Ainsworth et al , ].…”