A study reconstructs the events of the first day of the Cenozoic Era. The Chicxulub asteroid impact approximately 66 million years ago marked the boundary between the Mesozoic and Cenozoic Eras and likely caused the associated mass extinction event. To better understand the immediate aftermath of the impact, Sean Gulick and colleagues analyzed a core from the peak ring of the Chicxulub impact crater, a circle of elevated topography surrounding the center of the crater, containing approximately 130 m of impact melt rock and melt-bearing breccia deposited on the first day following the impact. Based on the analysis, the authors inferred that the bottom 40-50-m impact melt and breccia were rapidly deposited within minutes of the impact. Another 90 m of material was deposited by ocean water flowing back into the crater and the subsequent settling of debris over a period of hours. The top layer of the deposit contained soil biomarkers, suggesting that the tsunami caused by the impact was reflected back to the impact site during the first day, bringing terrestrial material with it. The presence of charcoal in the uppermost layers suggests the existence of impact-induced wildfires, whereas the absence of sulfur-rich evaporites from the deposit suggest that the impact released a large amount of sulfate aerosols that could have caused global cooling and darkening, according to the authors.
Article #19-09479: "The first day of the Cenozoic," by Sean P. S. Gulick et al.
MEDIA CONTACT: Sean P. S. Gulick, University of Texas at Austin, TX; tel: 512-471-0483; e-mail: email@example.com
Proceedings of the National Academy of Sciences