Impact Stratigraphy of the U.S. Gulf Coast States

Impact stratigraphy is the study of materials ejected from extraterrestrial impact craters and impact structures that become part of the stratigraphic record. Impact stratigraphy also commonly includes the distal effects of impact (e.g., seismic effects, extirpation, and mass extinction) within the stratigraphic record. The U.S. Gulf Coastal states have a remarkable variety of impact-related stratigraphy given the area involved. Distal ejecta from impacts occur at the Cretaceous-Paleogene boundary and within upper Eocene layers in the Gulf Coastal plains of Texas, Mississippi, and Alabama. In addition, at the Cretaceous-Paleogene boundary in those states, there are remarkable impact-related high-energy sedimentary deposits (tsunami- and/or tempestite-produced units). Further, there is evidence of impact-related, earthquake-produced faults at this stratigraphic level in western Alabama. In the upper Eocene of Georgia and Alabama, there are distal ejecta (including tektites), which are related to the Chesapeake Bay impact structure, Virginia. There are other enigmatic upper Eocene breccias and distal ejecta as well. This paper reviews impact ejecta layers and related deposits and structures of the U.S. Gulf Coast and presents some new findings about some of these features, which were produced by rare, high-energy cosmic events.