The Deformation of Eastern Ovda Regio – Collision and Complexity

Abstract

Western Aphrodite Terra, Venus, consists of two highland tesserae (or crustal plateaux), Ovda and Thetis Regionnes, separated by lower-lying fractured plains. The origin of highland plateaux has been the subject of debate, principally between the downwelling model of [1], which proposes that they form above mantle downwellings that shorten and thicken the ductile lower crust, and the upwelling model of [2], which proposes that they are produced by mantle plumes that thicken the crust by flood volcanism. These models make opposite predictions about the relationship between extensional and compressional features. A particular prediction of [2] is that tensile fractures and graben (both collectively referred to as ribbons) are formed by doming of a thin brittle layer above a large mantle upwelling. Later collapse of this dome produces circumferential folds. Here we examine the regional structure of Eastern Ovda and attempt to produce a deformation model to fit the observations. Specifically, we consider the location and orientation of ribbon and fold structures, and the late-stage deformation recorded in the intra-tessera basins.