A tectonic model for the formation of the gridded plains on Guinevere Planitia, Venus: Implications for the thickness of the elastic lithosphere

The "gridded plains" of Guinevere Planitia are comprised of a north-east trending set of extremely linear and regularly spaced lineations, and a north-west trending set of more irregularly spaced curvilinear radar-bright structures. The fainter NE set has been interpreted as cooling cracks in a thin surface layer (Banerdt and Sammis, 1992). The brighter NW trending set are interpreted as shear fractures in the lithosphere which have propagated up through the surface basalt flow after the more regular set of cooling cracks had formed. The length distribution of this set of fractures has a sharp bend at a length of about 80 km, which we interpret as reflecting a transition from the 3-D growth of a penny-shaped crack in the lithosphere to the 2-D elongation of a crack which has penetrated the elastic lithosphere. This interpretation implies that the elastic lithosphere is roughly 40 km thick.