The recovery of the deep biosphere at the Chicxulub impact crater

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Author(s): Coolen, Marco; Cockell, Charles S.; Schaefer, Bettina; Grice, Kliti; Schneiders, Luzie; Morgan, Joanna V.; Gulick, Sean P. S.; Wittmann, Axel; Lofi, Johanna; Christeson, Gail Lynn; Kring, David A.; Whalen, Michael T.
Author Affiliation(s): Primary:
Curtin University, West Australia Organic and Isotope Geochemistry Centre, School of Earth and Planetary Sciences, Perth, WA, Australia
University of Edinburgh, United Kingdom
University of Bremen, Germany
Imperial College London, United Kingdom
University of Texas at Austin, United States
Arizona State University, United States
Université de Montpellier, France
Universities Space Research Association, United States
University of Alaska Fairbanks, United States
Volume Title: AGU 2018 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2018; American Geophysical Union 2018 fall meeting, Washington, DC, Dec. 10-14, 2018. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The Chicxulub crater, Mexico, is the site of the asteroid impact that led to the end-Cretaceous mass extinction. While impact events are known to be able to cause severe disruption to surface-dwelling organisms, the effects of such catastrophic perturbations on the deep biosphere are not known. Deep ocean drilling into the peak ring of the Chicxulub impact crater (IODP expedition 364) in 2016 allowed us to study the modern deep biosphere within the (a) high-porosity melt-bearing impact breccia/suevite (617-740 mbsf) emplaced within a day or so of the Cenozoic, (b) the overlying low porosity post-impact marine Cenozoic carbonates (504-617 mbsf), and the impacted and fractured granitic basement (740-1334 mbsf). The microbial biomass (∼106 cells/g wet weight) was highest in the upper suevite, in underlying non-granitic subvolcanic pre-impact basanite, and at the intercalation of suevite and impact melt rock. Pre-impact sterile conditions of the uplifted granitic basement rocks and mineralogical evidence of impact-induced sterilization suggest that the basement rocks have only been amenable to microbial colonization for less than 66 Myr. Enrichments at in situ 50-60°C show the presence of heterotrophic lifestyles in the suevite and bacterial sulfate reduction extending into the top of the granitic basement. Cultivation-independent 16S diversity profiling revealed the presence of heterotrophic (fermentative) as well as autotrophic C-fixing thermophilic bacteria in the organic-rich (up to 4 wt % total organic carbon; TOC) Cenozoic sediments. The organic-lean suevite (< 0.1% TOC) showed the unique presence of sequences related to thermophilic Synechococcus (cyanobacteria) and S-oxidizing green sulfur bacteria (chlorobi), and Chloroflexi often associated with organic-poor deep-sea sediments. Alphaproteobacteria, predominated in the upper part of the granitic basement (<1000 mbsf), while putative manganese-oxidising Bacilli (Firmicutes) predominated in the melt-rich granitic basement (>1200 mbsf). Our data suggest that the catastrophe that led to the end-Cretaceous mass extinction caused geological disruption and recolonization of microbial life in the deep subsurface biosphere at the Chicxulub impact site.
Year of Publication: 2018
Research Program: IODP2 International Ocean Discovery Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Biosphere; Breccia; Chicxulub Crater; Cretaceous; Ecology; Expedition 364; Geomorphology; Gulf of Mexico; Impact breccia; Impact craters; Impact features; Impactites; International Ocean Discovery Program; Mesozoic; Metamorphic rocks; North Atlantic; Suevite; Upper Cretaceous
Coordinates: N212701 N212701 W0895658 W0895658
Record ID: 2019061731
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