Geologically Recent Formation of Some Tesserae on Venus by Plains Deformation

Abstract

Tessera is a pervasively deformed terrain type on Venus generally interpreted as the oldest preserved material on the surface. Large expanses of this terrain type are typically elevated and have been hypothesized to be felsic, perhaps analogous to Earth's continents and even to date from an era with a more Earth-like climate earlier in Venus' history. However, the compositions, modes of emplacement, and timing of deformation of this terrain type remain poorly understood. Here we propose, on the basis of detailed structural mapping, that volcanic plains along portions of the boundaries of the two largest highlands on Venus have been tectonically deformed so as to acquire the morphological characteristics of adjacent tessera units, thus increasing the areal extent of tessera globally. Some of the incorporated plains units are among the stratigraphically youngest on the planet. Our interpretation suggests that the formation of tessera terrain has continued into the geologically recent past on Venus, and that at least some portion of the crust underlying tessera has not required the production of large volumes of felsic rocks.