Plains Tectonism on Venus: Inferences from Canali Longitudinal Profiles

Canali-type channels on Venus show inverted profile segments; that is, large portions of the channels trend uphill. Th original gradients for these channels were not horizontal, but must have progressively trended downhill. Therefore, undulation patterns imposed on the profiles have to be the result of tectonism occurring since channel formation. This implies that some of the uppermost geological units of the plains, which are coincident with canali, experienced significant postemplacement tectonic deformation. The pattern of deformation is hierarchical. Within observational limits, at least two scales of deformation are indicated. The longer scale deformation (thousands of kilometers) corresponds to largescale basins; the shorter scale deformation (hundreds of kilometers) corresponds to ridge belts or to small-scale domes/basins. The latter features, at scales up to a few hundred kilometers, extensively deform some plains areas. Although not appearing in the topographic profiles because of resolution limitations, deformation scales of tens of kilometers or less, which mostly reflect wrinkle ridges, also overlap the longer deformation scales. The channels probably formed relatively quickly in comparison to the time scale of deformation. Canali formation is closely related to the genesis of plains, and canali profile deformation reflects tectonic processes operating at multiple scales. The lower limit rates of large-scale tectonic warping are comparable to epeirogenetic deformation rates for Earth's intraplate continental interiors.