Tectonic Evaluation of Alpha Regio Highland and Environs, Venus

Systematic geologic mapping of an area on Venus provides geologic unit and morphologic information about the area that was evaluated to provide a simple geologic history. In the study area, a large complexly deformed highland--Alpha Regio--was found to be among the oldest material units, but its relation to other nearby complexly deformed units was indeterminable. To better delineate the complex geologic and tectonic history of the area the authors expanded on the initial geologic map assessment by including tectonic unit mapping of the Alpha Regio highland and geophysical modeling of the highland to assess the possible effect of its formation on surrounding geologic units. Tectonic unit mapping identified five discrete periods of tectonic activity involved in the formation of the highland. Additionally, the tectonic assessment showed that late stage extensional features within the highland were related to a regional tectonic event that occurred after the formation of the highland. Geophysical models of highland formation by both upwelling and downwelling were assessed, and a downwelling model was applied to the Alpha Regio highland to calculate stresses related to its formation. Results of the modeling suggest that tectonic features mapped outside of the highland were not caused by stresses induced by the formation of Alpha Regio. [C] 2000 Academic Press