Deciphering the structural history of Ulysses Fossae, Mars, using fault pattern analysis

Ulysses Fossae is a faulted region surrounded by lava flows that sits between the major volcanoes of the Tharsis Rise volcanic province on Mars. This area is unique, as it is the only exposure of extensional faulting which can be related to the Olympus Mons volcano and one of the only a few faulted areas relating to the Tharsis Montes. In order to determine the area's structural evolution through time, we mapped all identifiable faults, divided them into 10 fault groups determined by their orientation and morphology, and performed detailed crater size-frequency analysis of the geological units. We divide the fault groups into two overall types based on their genesis: local diking and regional extension. The complex structural evolution recorded in the extensional faults in Ulysses Fossae is dominated by local dike-related activity (8/10 fault groups), along with deformation from large, regional scale extensional processes related to the development of the Tharsis province as a whole (2/10 fault groups). Strain values measured across the 1 fault groups vary between 0.4%–2.2%, with the grabens related to regional extension accommodating larger extensional strains than the local dike-related grabens. The crater size-frequency distribution analysis of three distinct areas in Ulysses Fossae (UF Dome, UF North, and UF South) revealed that the majority of the faulting in Ulysses Fossae was active during the Early Amazonian.