THRUST FAULTING ON VENUS: TECTONIC MODELING OF THE VEDMA DORSA RIDGE BELT (Invited Presentation)

Compressional ridge belts in the low-lying plains of Venus serve as windows into the tectonic setting, lithospheric properties, and thermal conditions of Venus during the time of ridge belt formation. Previous studies have analyzed ridge belts in Atalanta, Vinmara, Lavinia and Rusalka Planitae using radar images from the Magellan mission. We conduct a case study of the only ridge belt imaged with Magellan radar at two different viewing angles and is thus visible in the stereo topography digital elevation model (DEM) (Herrick et al., 2012): Vedma Dorsa, an ~1800 km long ridge belt with 0.5-1 km of relief in the Llorona/Vellamo Planitae. The asymmetry of topographic cross sections at several locations along Vedma indicates that the ridge belt was primarily formed by deep thrust faulting and shallow lithospheric folding. Detailed elastic dislocation and Monte Carlo tectonic modeling of thrust faulting at these locations is consistent with this interpretation, resulting in the preferred fault displacement (D) of ~ 1–2 km, depth of faulting (z) of ~10–25 km, and fault dip (θ) of ~ 25–30°. Our preferred models and the additional fault complexities supported at each site suggest that Vedma is an intermediate structure between lobate scarps and fold and thrust belts, incorporating morphometric aspects from both classifications. Considering terrestrial fault depths and the preferred depth of faulting from our models, we derive a heat flux of 16–39 mW/m² at the time of faulting. The low value for the heat flux is consistent with compressional deformation over cold, downwelling mantle and is within the range of estimated global average heat flux on Venus. Our results demonstrate that better topography data is needed for in-depth analysis of ridge belts and tectonic structures that provide key insight into the surface and thermal evolution of Venus’s lithosphere, which will be made possible with NASA’s future VERITAS mission, and ESA’s future EnVision mission.