Amazonian Tectonic Evolution of Ceraunius and Tractus Fossae, Mars, and Implications for Local Magmatic Sources

The heavily faulted Martian terrains of Ceraunius Fossae and Tractus Fossae, south of the Alba Mons volcano, have previously only been considered as parts of larger tectonic studies of Alba Mons, and consequently the complexity of the faulting remains unclear. As these terrains are in the midst of the large Tharsis volcanoes, the study of their surface deformation has the potential to help unravel the volcano-tectonic deformation associated with the growth of Tharsis as well as to decipher details of the magma-tectonic processes responsible for graben formation. Here, we distinguish between faults and collapse structures based on image and topographic evidence. We mapped ∼12,000 faults, which we grouped into three distinct fault groups based on orientation, morphology, and relative ages. These show a temporal evolution in the mapped fault orientations from NE to N-S to NW with associated changes in stress orientations. We also mapped collapse features and categorized them into four different groups: pit-crater chains, catenae, u-shaped troughs and chasmata. Examining the four collapse structure groups reveals that they are likely four progressive stages in the erosional evolution of pit-crater chains. Together, this revealed a structural history heavily influenced by lateral diking from both local (radial to Alba Mons, Pavonis Mons and Ascraeus Mons) and regional (radial to Tharsis) sources, and vertical diking from a proposed Ceraunius Fossae centered magma source. This, along with an updated crater size-frequency distribution analysis of the unit ages, reveals a highly active tectonic and magmatic environment south of Alba Mons in the Middle Amazonian.