Formation and Diagenesis of Sedimentary Rocks in Gale Crater, Mars

Abstract

The history of surface processes on Mars is recorded in the sedimentary rock record. Sedimentary rock layers exposed in Gale Crater on the modern crater floor (Aeolus Palus) and on Mount Sharp (Aeolus Mons), which hosts one of the more complete records of transitions between major mineralogical eras on Mars, have been investigated by the Mars Science Laboratory Curiosity rover since landing in August 2012. This dissertation focuses on the formation and diagenesis of the sedimentary rocks in Gale crater in order to assess the compositional diversity of the volcanic sources around Gale crater, the effects of transport processes on the sediment grains, and the volumes and geochemistry of water that transported and cemented the sediments. The first study uses orbital mapping of a distinctive cemented boxwork layer on Mount Sharp to constrain a minimum volume of groundwater available to form this layer, 1 km above the modern floor of Gale, with implications for the formation of Mount Sharp. The other three studies use Curiosity rover imagery and geochemical data to investigate sedimentary rocks in Aeolus Palus and at the base of Mount Sharp. The second study identifies and describes diagenetic synaeresis cracks in the Sheepbed mudstone, at the lowest elevation in Aeolus Palus, with implications for the duration of water saturation of these lake sediments. The third and fourth studies identify and explain geochemical trends in the fluvio-deltaic Bradbury group, the Murray mudstone formation, and the eolian Stimson sandstone, focusing on geochemical diversity in the source regions for each of these units and how different depositional processes are reflected in the geochemical data. The sedimentary system in Gale crater has changed our understanding of Mars by expanding the known variety of igneous rocks, increasing estimates of the longevity of surface water lakes, and showing that there were once habitable environments on our neighboring planet.