Formation and evolution of the westernmost corona of Aphrodite Terra, Venus

Previous knowledge of Venus equatorial highlands has been greatly extended by Magellan SAR imagery. Spanning over more than 15,000 km, with a mean elevation of 3 km, Aphrodite Terra is a key region for the comprehension of Venusian geology and tectonics. Surface geology is investigated with the high-resolution Magellan radar imagery. This study focuses on the westernmost part of Aphrodite Terra, an area 2000 km in diameter centred on Verdandi Corona. Structural interpretation is based on conventional manual cartography and image processing. The conjunction of these two methods enables a model of formation to be proposed in four stages: (1) intense fracturation of the substratum under extensive stress, creating a pattern of small horsts and grabens, (2) filling of grabens by a volcanic material, (3) formation of Verdandi Corona, a circular feature 180 km wide, with concentric and radial fractures corresponding to the remains of a subsiding volcano, (4) N105° faults overcutting the caldera and radial normal faults developing at its periphery. Along with the topographic information available, these stages suggest that this corona results from the rising, cooling and flattening of a diapir intruded in the Venusian pre-existing fractured crust.