Collaborative Research: Post-Impact Studies of the Chesapeake Bay Impact Structure: Quantifying Continental Margin Evolution

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0606693MillerThis project will extend earlier work funded by CD involving the analysis of stratigraphy on the US Mid-Atlantic Margin. The PIs have been involved in a long term project of coring, logging, and seismic profiling of this passive margin in order to extract global sea-level change from the stratigraphic record and evaluate the role of eustasy, tectonic subsidence, and sediment input on passive continental margin sedimentation. This effort has culminated in the development of a eustatic estimate for the past 100 million years derived largely from backstripping studies of New Jersey onshore boreholes. The Chesapeake Bay Impact Structure (CBIS) has recently been drilled by the USGS (5 coreholes drilled within the crater). The PIs were involved (with CD funding) in logging the holes and have access to the cores for analysis. The PIs will evaluate the geodynamic effects of a large impact on crustal subsidence and the relative roles of global sea-level and regional tectonic changes on molding the stratigraphic record of the margin. Comparison of backstripping (accounting for the effects of sediment loading, compaction, paleowater depth, and basin subsidence) results from the 5 coreholes in the crater with previously analyzed coreholes outside the crater will allow them to quantify the effects of tectonics and global sea level. These comparisons will provide a natural experiment quantifying the relative effects of impact-generated accommodation versus "normal" thermo-flexural subsidence, sea-level, and sediment supply on the evolution of a passive continental margin. The project specifically focuses on short and long term tectonic consequences of impact, refinement of Cenozoic stratigraphy for the east coast, and improvement of the regional and global sea level curve for post-Eocene time. The project will also examine the oxygen and carbon isotopic composition of sediments deposited immediately after the impact in order to look for isotopic excursions associated with climatic effects caused by the impact.