The Tectonic History of Western Arabia Terra, Mars

This thesis explores the tectonic history of Mars. It focusses on the regions of Arabia Terra, Chryse Planitia and Acidalia Planitia that surround Oxia Planum, the selected landing site of the ExoMars <i>Rosalind Franklin</i> Rover. The region contains widespread kilometre-scale tectonic landforms, shortening structures, that are surface expressions of thrust-faults with various degrees of folding. This thesis aims to study these to ascertain the spatial distribution of tectonic structures in the region, determine when the region was tectonically active and investigate the temporal history of the tectonic structures, and quantitively study the tectonic structures. <br><br> Using remote sensing datasets (CTX, THEMIS, HRSC, MOLA), I produce a 1:4,000,000 scale map of tectonic shortening structures in a 3 million km² study area. I use four methods to ascertain the timing of tectonic activity, including relative dating (stratigraphic relationship with map units, crosscutting relationship with crater populations, crosscutting relationships using crater size-frequency distribution analysis of ejecta blankets) and absolute dating (buffered crater count analysis of individual structures). I analyse tectonically-triggered landslides using high-resolution datasets (CTX, HiRISE, CaSSIS), to explore fault re-activation via a case study at Marsabit crater and thereby achieve a more comprehensive insight into the formation history of shortening structures. Finally, I constrain the timing of tectonic activity based on crosscutting relationships, relative to other features in the study area such as the extensive fluvial features. <br><br> The mapping reveals 845 tectonic shortening structures that have heights of 8 m to 700 m, a combined length of ∼28,000 km, and a dominant N-S orientation. Analysis of the age of these structures demonstrates that tectonic activity on Mars was not constrained to ancient times. The shortening structures formed and were active throughout Mars’ history. Many formed circumferentially to Tharsis during the Noachian and Hesperian, but remained active well into the Amazonian. The series of tectonically-triggered landslides and the presence of crestal grabens provide strong evidence that tectonic processes on Mars continued into the Middle-Late Amazonian and were not just confined to volcanic provinces. Future in-situ investigations by the ExoMars <i>Rosalind Franklin</i> Rover may provide the opportunity to compare small local faults/fractures/veins to this regional structural survey.