Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Planetary Science

Supervisor

Dr. Gordon Osinski

2nd Supervisor

Dr. Livio Tornabene

Joint Supervisor

Abstract

Central uplifts within complex impact craters on Mars and Earth have been studied for many decades. Nevertheless, their formation is still poorly understood (regarding target rock weakening mechanisms), as well as the impactites found within, them including their extent and distribution. We have cartographically approached these questions by mapping morphologies and structures within three impact craters on Mars, utilizing high-resolution images taken by the Mars Reconnaissance Orbiter combined with other data sets, while making comparisons to terrestrial field-based observations and measurements. Betio (281.38° E, -23.15° N), Byala (293.54° E, -25.75° N), and Halba (303.91° E, -26.03° N) impact craters are all ~30 km in diameter, located within the Hesperian-aged Ridged Plains unit in Thaumasia Planum, Mars, and contain central floor pits that expose megablocks of layered bedrock. A comparison of three craters of similar diameters, target lithologies, and geographical regions allows us to investigate the morphologic and structural similarities and differences found between the three craters. Our mapping reveals a variety of faults, folds (likely radial transpression ridges), multiple interpreted breccia dykes, in addition to different types of interpreted impactites (e.g., breccias and melts –clast –free and –rich, pitted materials and uplifted bedrock (i.e., parautochthonous bedrock). Through structural mapping we have found that smaller (60–300 m in diameter) blocks with high dips of ~ 45° to 85° are present proximal to the relatively flat floor pit and larger (>800 m in diameter) blocks with shallow dip angles of ~ 5 ° to 15° occur in the outer sections of the floor pit, similar to terrestrial observations. Deformation mechanisms that aided in the uplift and collapse include brittle deformation, seen increasing towards the centre of the crater, a decrease in block size closer to the centre, and the presence of fault-bounded blocks.

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