Ridge Belts: Evidence for Regional- and Local-scale Deformation on the Surface of Venus

We evaluate models for the formation of the ridge belt fan assemblage on Venus through consideration of the orientation, spatial distribution, topographic expression and wavelengths of observed tectonic surface features. We favor a compressional mechanism for long wavelength deformation corresponding to the spacing of ridge belts (300_<),<400 kin). However, short wavelength ridges and grooves (10_<),<20 km) that are contained within belts and trend parallel to them are likely to be compressional and extensional, and to reflect both regional and local stress fields. We hypothesize that large-scale (> > ridge spacing) early-stage mantle downwelling is the source of regional compression responsible for the establishment of the long wavelength of deformation.