Research conducted on the drill core collected during IODP-ICDP Expedition 364 to the Chicxulub crater has profoundly affected on our understanding of impact and cratering processes, deposition of impact-related breccias and post-impact sediments, the return of life to the crater, processes associated with ejecta distribution and deposition, the release of climate-perturbing gases, and the development of a long-lived hydrothermal system in the crater. Newly recovered cores from Expedition 364 include the uplifted target rocks: melt-rich impactites, hydrothermal deposits, a tsunami bed coupled with a transitional layer, and the resumption of carbonate sedimentation. These lithologies record processes spanning from minutes to millions of years post-impact.

            One of the key findings of the project concerns the development of large, complex craters and their peak rings (a ring of discontinuous mountains around a crater?s center). The discovery that the peak ring is composed of granitic rocks previously buried to 10 km depth confirms the hypothesis that peak rings form from the simultaneous collapse of a central uplift and radial faulting that progressively down dropped the crater?s terrace zone toward the crater center (Fig. 1).

            Another major hypothesis concerning impact cratering is that the target rocks weaken dramatically and behave similar to a fluid and our group?s research documented this fluidization and subsequent strengthening of the rocks resulting in more brittle deformation. Our group documented in great detail the return of water to the crater that reworked and redeposited impact breccias. We documented deposition and reworking of impact breccias by tsunami and seiches as well as deposition of a transitional unit between the breccias and normal marine early Cenozoic sediments (Fig. 2). The transitional unit records the return of life to the crater with both microfossils and the burrows of soft bodied organisms preserved in sediments likely deposited within years of the impact (Fig. 2). We documented the microbial communities that proliferated in the nascent crater as well as the current day microbial community in the deep biosphere. We were also the first to document the remains of the impactor itself in the crater, providing a direct link with the environmental consequences of globe-circling impact ejecta. Our research helped to quantify the release of climate-active gasses by the impact that influenced the amount of sunlight reaching the Earth, surface temperatures, and provides one of the major kill mechanisms for the extinction event. Numerical modeling of the impact provided insight into the angle of impact, interpreted to be steeply inclined, which resulted in the release of more climate-perturbing gases than either a vertical or a shallowly inclined impact. Our team also documented the magnitude and history of the hydrothermal system that developed post-impact and persisted for at least 2 million years.

            Analysis of post impact sediments deposited during the early Cenozoic provides a view of the paleoceanography of the crater and the return of a highly productive ecosystem within 30,000 years of the impact. Another of our groups? studies provides insight into the climatic and floristic changes that occurred during the Paleocene-Eocene thermal maximum, 10 million years after the impact. At Chicxulub, this event is characterized by an increase in terrigenous input and surface productivity, salinity stratification, bottom waters with low oxygen content, and evidence of low oxygen and the build-up of hydrogen sulfide in shallow waters of the photic zone. Additional research on the Paleocene and Eocene portions of the core provide further insight into the early Cenozoic paleoceanography and sea level history at Chicxulub.

            Chicxulub drilling unleashed an unprecedented level of interest from the media, including numerous press releases, newspaper stories and scientific journal news updates, radio interviews and two television documentaries (BBC and Nova). Interest in the science surrounding the drilling has grown as significant results from the work funded by our proposal and allied international efforts has come to light. Our research was listed by the journal Science as the runner-up science story of 2019 behind the breakthrough story of the year concerning an international team of astronomers that first imaged a black hole.

Last Modified: 11/24/2021
Modified by: Michael T Whalen