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Black shale deposition, atmospheric CO2 drawdown, and cooling during the Cenomanian-Turonian Oceanic Anoxic Event

Wiley Blackwell (John Wiley & Sons)
Publication Date
DOI: 10.1029/2010pa002081
  • Archaeology
  • Earth Science


Oceanic Anoxic Event 2 (OAE2), spanning the Cenomanian-Turonian boundary (CTB), represents one of the largest perturbations in the global carbon cycle in the last 100 Myr. The δ C , δ C , and δ O chemostratigraphy of a black shale-bearing CTB succession in the Vocontian Basin of France is described and correlated at high resolution to the European CTB reference section at Eastbourne, England, and to successions in Germany, the equatorial and midlatitude proto-North Atlantic, and the U.S. Western Interior Seaway (WIS). C (offset between δ C and δ C ) is shown to be a good pCO proxy that is consistent with pCO records obtained using biomarker δ C data from Atlantic black shales and leaf stomata data from WIS sections. Boreal chalk δ O records show sea surface temperature (SST) changes that closely follow the C pCO proxy and confirm TEX results from deep ocean sites. Rising pCO and SST during the Late Cenomanian is attributed to volcanic degassing; pCO and SST maxima occurred at the onset of black shale deposition, followed by falling pCO and cooling due to carbon sequestration by marine organic productivity and preservation, and increased silicate weathering. A marked pCO minimum (∼25% fall) occurred with a SST minimum (Plenus Cold Event) showing >4C of cooling in ∼40 kyr. Renewed increases in pCO , SST, and δ C during latest Cenomanian black shale deposition suggest that a continuing volcanogenic CO flux overrode further drawdown effects. Maximum pCO and SST followed the end of OAE2, associated with a falling nutrient supply during the Early Turonian eustatic highstand. Copyright 2011 by the American Geophysical Union.

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