Landforms Associated With the Aspect-Controlled Exhumation of Crater-Filling Alluvial Strata on Mars

Abstract

Fluvial channel belts, the deposits accumulated in rivers surrounded by floodplain deposits, are sensitive environmental recorders. Across Mars, wind has exposed ancient channel belts via the preferential erosion of floodplain strata, creating landforms called fluvial ridges. However, river deposits observed by the Mars rover Curiosity are instead exposed along a series of steep slopes and shallow benches, and short, truncated ridges we call noses. Here, we tested the hypothesis that these exposures record channel-belt exhumation with a preferential direction of scarp retreat (a slope-aspect control), in contrast with models of fluvial-ridge formation. Using a landscape evolution model sensitive to lithology and an Earth-analog 3D-seismic-reflectance volume imaging fluvial stratigraphy, we generated synthetic erosional landscapes where channel-belt exhumation created benches and noses rather than fluvial ridges, depending on the orientation of belts relative to the preferential direction of scarp retreat, which we suggest is set by winds steered along crater topography.