Geophysical insights into the crater subsurface at the Chicxulub and Ries impact craters




McCall, Naoma

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Large impact events have shaped the evolution of life on Earth both during early Earth history and the K-Pg extinction event. They transport huge volumes of rock distances of kilometers in timescales ranging from seconds to minutes. Impacts are found on every rocky and icy planetary body and are the dominant form of crustal resurfacing on planets without plate tectonics. As impact cratering is an important geologic process, but one that is rarely observed in real time, our understanding relies on modeling and existing craters. On Earth, impact craters are often eroded, tectonically deformed, or buried in sediment. This dissertation uses drill core and seismic data at two craters largely obscured but preserved by sedimentation: the Chicxulub impact crater, Mexico and the Nördlingen Ries impact crater, Germany. My research ground-truthed impact cratering models and strengthened theories of faulting and acoustic fluidization at Chicxulub. At Ries, the data acquired, processed, and interpreted during this PhD shows that Ries is a transitional crater that exhibits neither a central peak nor peak ring and that the suevite deposition at the crater was emplaced via ground-hugging flows. I measured the permeability of peak ring rocks from the International Ocean Discovery Program (IODP) Expedition 364 core, an important parameter for determining the duration of the post impact hydrothermal system at Chicxulub, I found that the permeabilities were likely responsible for an isolated and heterogeneous post-impact hydrothermal system at Chicxulub.


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