ABSTRACT

The latest of Earth?s five largest mass extinction events occurred coeval with the impact of a ~14 km asteroid into the Yucatan Peninsula (Mexico), ending the Mesozoic Era. In April-May 2016, the International Ocean Discovery Program (IODP), with co-funding from the International Continental Scientific Drilling Program (ICDP), successfully cored with nearly 100% recovery from 505-1337 m below seafloor into the resulting 200 km-wide Chicxulub impact crater. These cores record an extraordinary sequence of impact and post-impact events. This project will investigate these unique cores further to understand the local and global effects of the only impact conclusively linked to a mass extinction event. This research is part of a larger international effort, including ~40 scientists from 14 countries, and also supports education and mentoring at the graduate and post-graduate level. Project researchers will continue to engage in outreach and education through media interviews, museum displays, and other activities to highlight the research to the general public.

The recent IODP-ICDP drilling expedition at Chicxulub recovered the first-ever samples of an unequivocal peak ring. A peak ring is a discontinuous ring of mountains observed within the central basin of all large impact craters on rocky planets. The discovery that Chicxulub?s peak ring consists of largely granitic crust uplifted by ~10 km calibrates impact models, allows for observation of impact processes, and for a first-order assessment of the environmental consequences of the impact (?kill mechanisms?). Newly recovered cores include the uplifted target rocks: melt-rich impact generated rock types, hydrothermal deposits, a tsunami bed coupled with a settling layer, and the resumption of carbonate sedimentation. These lithologies record processes spanning from minutes to millions of years post-impact. The proposed work will:

1. Reconstruct thermal history of the peak ring and the duration of the impact-induced hydrothermal system to determine how these processes affected the return of life to the crater.
2. Compare rock fragments in the impact rocks to pre-impact stratigraphy to quantify the volatiles released and constrain models of impact-induced climate change and extinction.
3. Find the first conclusive evidence of the asteroid within the crater to tie to global K-Pg boundary records and identify the possible influence of metal toxicity.
4. Investigate the fossil record of the boundary sequence, in concert with the sedimentology, stratigraphy, and environmental chemistry, to illuminate possible killing mechanisms and determine the pace and timing of the recovery within the crater from the weeks after the impact through the early Paleocene.

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