Vertical and lateral collapse of Tharsis Tholus, Mars

Abstract

Tharsis Tholus, a more than 3.9Ga old composite shield volcano to the east of the major Tharsis Montes, has experienced a complex history of growth and destruction. On the basis of new high resolution images we analysed the morphology as well as the tectonic structures of the Tharsis Tholus volcano in detail. From morphological data, cross-cutting relations of the surface structures, and crater modelling ages we propose a chronostratigraphy for the volcano-tectonic history of Tharsis Tholus.The strongly faulted volcano reveals two large-scale landslide events followed by two subsequent shield re-growth phases between 3.8 and 1.7Ga and two caldera collapses. Tharsis Tholus was also affected by regional extensional tectonics between 1.7Ga and 0.4Ga recorded by sub-parallel sets of NE trending graben structures. The steep and up to 5.4km high landslide scarps on Tharsis Tholus suggest deep faulting of the edifice. In order to confirm this hypothesis we used analogue sand box models in which we demonstrated that gravitational flank movement on top of weak basal substrata may have produced the deformation structures as observed on Tharsis Tholus.