Layered MegaBlocks in the central uplifts of impact craters

Abstract

A database of bedrock exposed in crater central uplifts has been compiled from multiple orbital datasets. In this study we focus on uplifts which show decameter-scale layers within the exposed megablocks derived from the bedrock of the preexisting target. This distinctive morphology, found in 41 craters globally, occurs mostly in regions mapped as Hesperian plains material, generally interpreted as regions of extensive flood lavas. The association with volcanic units coupled with morphology and mineralogy that is consistent with flood lava emplacement suggests that the layers are stacks of dense lava interbedded with weaker materials. Estimates for the uplift of stratigraphic sections coupled with morphologic and morphometric analyses lead to estimated thicknesses of the layered unit. These estimates indicate Hesperian flood lavas are ∼23% thicker than a previous minimum estimate, with a volume of 5.5×107km3. This increases the known extrusive volcanic production for the history of Mars and volatile release to past martian atmospheres.