Microbial life in the nascent Chicxulub crater

Abstract

The Chicxulub crater was formed by an asteroid impact at ca. 66 Ma. The impact is considered to have contributed to the end-Cretaceous mass extinction and reduced productivity in the world’s oceans due to a transient cessation of photosynthesis. Here, biomarker profiles extracted from crater core material reveal exceptional insights into the post-impact upheaval and rapid recovery of microbial life. In the immediate hours to days after the impact, ocean resurge flooded the crater and a subsequent tsunami delivered debris from the surrounding carbonate ramp. Deposited material, including biomarkers diagnostic for land plants, cyanobacteria, and photosynthetic sulfur bacteria, appears to have been mobilized by wave energy from coastal microbial mats. As that energy subsided, days to months later, blooms of unicellular cyanobacteria were fueled by terrigenous nutrients. Approximately 200 k.y. later, the nutrient supply waned and the basin returned to oligotrophic conditions, as evident from N2-fixing cyanobacteria biomarkers. At 1 m.y. after impact, the abundance of photosynthetic sulfur bacteria supported the development of water-column photic zone euxinia within the crater.

The Habitat of the Nascent Chicxulub Crater

“…There are no organic-walled dinoflagellates in the green marlstone but calcite and apatite interpreted as fossils of cyanobacteria are common (supporting information Figure S8; Pl. 1-8), an interpretation supported by organic biomarkers (Schaefer et al, 2020).…”

Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction

“…Even within the site of the asteroid impact, rich communities were reestablished within 30 ky of the K/Pg boundary ( 45 ). This implies a very rapid recovery of marine productivity ( 45 , 46 ), which argues against the suggested delay in ecosystem reset caused by continued Deccan volcanism after the K/Pg boundary ( 9 , 45 , 46 ). In contrast to the end-Permian mass extinction, the K/Pg event was geologically instantaneous ( 2 – 4 , 10 , 23 , 35 ), and there is no clear evidence for a prolonged decline ( 3 , 4 , 35 , 47 ) that would be required for Deccan volcanism to trigger a mass extinction-level event due to the short residence time of stratospheric aerosols.…”

“…S7 B ). After the extinction, the marine environment recovered relatively fast, between a few thousand years to ∼1 My ( 9 , 45 , 46 , 49 ).…”

Response to Kate Littler

“…As described, the carotenoid biomarkers are present, albeit in trace concentrations, above and below the black shale interval. In the crater basin, evidence of periods of photic zone euxinia was reported for the limestone interval prior to the PETM, as shown by Schaefer et al (2020). Here, different sources (microbial mats versus open water column PZE) for the elevated carotenoids have been proposed.…”