SHORT TERM IMPACT EFFECTS: MODELING THE CHESAPEAKE BAY IMPACT STRUCTURE

The Chesapeake Bay Impact Structure (CBIS) is a ~35.4 million year old crater located on the eastern seaboard of North America. This impact occurred in an area that allowed for a return to “normal” deposition shortly after impact, resulting in a unique record of both impact related and subsequent passive margin sedimentation. We use backstripping to show that the impact strongly affected sedimentation for 7 m.y. through impact derived crustal scale tectonics dominated by the effects of sediment compaction and the introduction and subsequent removal of a negative thermal anomaly. This negative thermal anomaly appears as an interplay of increased subsidence immediately post-impact due to the cooling of the upper crust by the sediment load, and is later replaced by a period of uplift as the sediment pile insulates and traps heat during the return to thermal equilibrium. After this, the area was dominated by passive margin thermal subsidence overprinted by periods of regional scale uplift and excess subsidence. These periods record uplift and excess subsidence on the order of 10's to 100 m's of change, and are consistent with sediment loading from the development of prograding sediment bodies.