Geology of the Alpha Regio (V-32) Quadrangle, Venus

We present a 1:2,500,000 geological map of the Alpha Regio (V-32) quadrangle, Venus. The V-32 quadrangle extends from 0° to 25 S, 0°to 30° E with an area of approximately 7,600,000 km2. Geological mapping was conducted using full resolution (maximum 75 m/pixel) SAR, altimetry and stereo-derived topography data from NASA's Magellan mission in ArcGIS 10.5. Nearly 40,000 lineaments were mapped. The oldest unit, tessera terrain, is present in two major regions: Alpha Regio and Minu-Anni Tessera. Two major fracture belts, both oriented approximately NNW-SSE, and four minor fracture belts have been identified and characterized. Two previously unrecognized wrinkle ridge trends of radiating and circumferential orientation have also been identified in the northeastern corner of the quadrangle. A total of 77 geological units were mapped. Plains material, previously mapped as global regional plains units, was divided into 27 units. Earlier estimates of the diameters of several coronae have been extended by hundreds of kilometres

Analysis of Venusian wrinkle ridge morphometry using stereo-derived topography: A case study from Southern Eistla regio

We present an analysis of 503 topographic profiles taken across 40 ENE-WSW trending wrinkle ridges from Southern Eistla Regio, Venus, using stereo-derived topography. We find that their average widths and heights are on the order of 10 km and 100 m, respectively. While the majority of the wrinkle ridges are asymmetric and display vergence to the southeast, some are quasi-symmetric, possibly representing pop-up structures, and possess multiple peaks along the backslope, potentially indicating the presence of secondary backthrust faults. Fault geometry modeling in which the average observed wrinkle ridge topographic profile is matched to the calculated surface deformation while varying various faulting parameters indicates that the wrinkle ridges studied have dips of 30°, penetrate to depths of 5 km or less, are blind and reach to within 2 km of the surface, have accommodated approximately 200 m of slip, and possess a planar geometry. These results imply that the wrinkle ridges formed through a thin-skinned deformation style. The spacing and distribution of the wrinkle ridges at a regional scale displays a clear relationship between wrinkle ridge deformation and lithospheric properties. We therefore conclude that the distribution of wrinkle ridges in the study area is a direct reflection of the regional strain which, in turn, is a result of mantle dynamics coupled with lithospheric thickness. The accumulation of contractional deformation expressed as wrinkle ridges appears to be the result of mantle downwelling along the peripheries of Eistla Regio