IODP-ICDP Expedition 364; drilling the Chicxulub impact crater to understand planetary evolution and mass extinction

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Author(s): Gulick, Sears P. S.; Morgan, Joanna V.
Author Affiliation(s): Primary:
University of Texas at Austin, Institute for Geophysics, Austin, TX, United States
Imperial College London, United Kingdom
Volume Title: AGU 2017 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2017; American Geophysical Union 2017 fall meeting, New Orleans, LA, Dec. 11-15, 2017. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The most recent of Earth's five largest mass extinction events occurred 66 Ma, coeval with the impact of a ≈12 km asteroid, striking at ≈60 degrees into what is today the Yucatán Peninsula, México, producing the ≈200 km-wide Chicxulub crater. This impact, by some estimations, drove the extinction of 75% of life on Earth at the genus level. The mass extinction event marks the boundary between the Cretaceous and Paleogene. Proposed kill mechanisms include thermal effects caused by the reentry of fast ejecta into Earth's atmosphere, dust and sulfate aerosols reducing Earth's solar insolation, ocean acidification, and metal toxicity due to the chemical make-up of the impactor. The magnitude and duration of these processes is still debated, and further evaluation of the proposed kill mechanisms requires an understanding of the mechanics of the Chicxulub impact as well as the resulting global environmental perturbations. In April and May 2016, the International Ocean Discovery Program, with co-funding from the International Continental Scientific Drilling Program, successfully cored into the Chicxulub impact crater with nearly 100% recovery. These cores include the first-ever samples of the transition from an intact peak ring through post-impact sediments. A peak ring is a discontinuous ring of mountains observed within the central basin of all large impact craters on rocky planets. Newly drilled cores include the uplifted target rocks, melt-rich impactites, hydrothermal deposits, a possible settling layer, and the resumption of carbonate sedimentation. The discovery that Chicxulub's peak ring consists of largely granitic crust uplifted by ≈10 km calibrates impact models and allows for observation of impact processes. At the top of the peak ring, the K-Pg boundary deposit includes a impactite sequence ≈130 m thick deposited by processes that range from minutes to likely years post-impact. This sequence is then overprinted by hydrothermal processes that lasted at least 100s Kyr post-impact and may have fed a subsurface ecosystem within the crater. The full recovery of life within the crater spans from immediately after impact through millions years allowing for a first-order assessment of the environmental consequences of the impact ("kill mechanisms").
Year of Publication: 2017
Research Program: IODP2 International Ocean Discovery Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Cenozoic; Chicxulub Crater; Cretaceous; Expedition 364; Gulf of Mexico; Impacts; International Ocean Discovery Program; K-Pg boundary; Lower Paleocene; Mass extinctions; Mesozoic; North Atlantic; Paleocene; Paleoecology; Paleogene; Stratigraphic boundary; Tertiary; Upper Cretaceous
Coordinates: N212701 N212701 W0895658 W0895658
Record ID: 2018093724
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