A Diverse Array of Fluvial Depositional Systems in Arabia Terra: Evidence for mid-Noachian to Early Hesperian Rivers on Mars.

Branching to sinuous ridges systems, hundreds of kilometers in length and comprising layered strata, are present across much of Arabia Terra, Mars. These ridges are interpreted as depositional fluvial channels, now preserved as inverted topography. Here we use high-resolution image and topographic data sets to investigate the morphology of these depositional systems and show key examples of their relationships to associated fluvial landforms. The inverted channel systems likely comprise indurated conglomerate, sandstone, and mudstone bodies, which form a multistory channel stratigraphy. The channel systems intersect local basins and indurated sedimentary mounds, which we interpret as paleolake deposits. Some inverted channels are located within erosional valley networks, which have regional and local catchments. Inverted channels are typically found in downslope sections of valley networks, sometimes at the margins of basins, and numerous different transition morphologies are observed. These relationships indicate a complex history of erosion and deposition, possibly controlled by changes in water or sediment flux, or base-level variation. Other inverted channel systems have no clear preserved catchment, likely lost due to regional resurfacing of upland areas. Sediment may have been transported through Arabia Terra toward the dichotomy and stored in local and regional-scale basins. Regional stratigraphic relations suggest these systems were active between the mid-Noachian and early Hesperian. The morphology of these systems is supportive of an early Mars climate, which was characterized by prolonged precipitation and runoff.

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©2019. The Authors.