Layered mantling deposits in northeast Arabia Terra, Mars: Noachian-Hesperian sedimentation, erosion, and terrain inversion

[1] Thick, layered mantling deposits of different ages occur in several nonpolar regions of Mars and are thought to represent volcanic ash and/or climate-related ice-dust deposition. One such deposit is a layered mantling unit that unconformably blanketed highlands terrain in northeast Arabia Terra during the Late Noachian and/or earliest Hesperian. Shortly thereafter, by the mid-Hesperian, this deposit was substantially eroded; on the basis of its superposed crater population, it appears to have subsequently retained its approximate morphology and distribution in the 3.5 Gyr since. When the erosion occurred, in the Early Hesperian, the mantling unit was more resistant in some areas than its surroundings, resulting in inversion of relief: craters were transformed into highstanding buttes, and valleys were transformed into isolated ridges. On the basis of the scale of the observed inversion of relief, the magnitude of erosion in northeast Arabia Terra was substantial, up to hundreds of meters. We have used newly available data to assess the nature of the mantling material and probable mechanisms for its deposition and removal. We find that (1) the mantle unit is layered at scales of meters to tens of meters; (2) the deposit has a median thickness of 60 m, and the thickness of the deposi