Journal
EARTH-SCIENCE REVIEWS
Volume 203, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.earscirev.2020.103123
Keywords
Carbon cycle; Cretaceous; Oceanic Anoxic Event 2; Mid-Cenomanian Event; Box model; Large Igneous Province
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Funding
- Schlanger Fellowship from the Consortium for Ocean Leadership
- Institute for Sustainability and Energy at Northwestern (ISEN)
- National Research Foundation of Korea - Ministry of Science and ICT [NRF-2019R1C1C1005550]
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The middle Cretaceous was a period characterized by elevated sea-floor spreading rates, enhanced volcanism, high atmospheric CO2 levels, warming temperatures, and the peak eustatic highstand of the Mesozoic. Two well-known perturbations in the global carbon cycle mark this interval - the Cenomanian-Turonian Oceanic Anoxic Event 2 (OAE2) and the Mid-Cenomanian Event (MCE). Although studies during the past two decades have arrived at a consensus that the Caribbean Large Igneous Province (LIP) likely played a key role in triggering OAE2, arguably the most significant perturbation of the Late Cretaceous, the detailed environmental developments during the Mid-Late Cenomanian leading up to it have only recently been the focus of investigations. This study, based on previous studies of the Middle Cenomanian - Early Turonian climate, tectonics, sea level, and carbon isotope chemostratigraphy, tests plausible environmental scenarios to explain the behavior of the Middle Cenomanian to Early Turonian carbon cycle, via isotope-mass balance calculation in a simple carbon cycle box model. The model experiments successfully reproduce two distinctive features observed in the Mid-Late Cenomanian delta C-13 curves - 1) decoupling of delta C-13(carb) and delta C-13(org) reflecting increasing isotope fractionation in response to steadily rising pCO(2), driven by enhanced volcanic degassing of mantle-derived CO2, which likely preceded the presumed peak volcanism of the Caribbean LIP; and 2) a long-lived, secondary positive excursion that documents enhanced organic carbon burial in shallow shelf seas that expanded during global sea-level rise and highstand. We demonstrate a plausible combination of environmental forcings that pre-conditioned the mid-Cretaceous ocean-atmosphere system for a massive perturbation, OAE2.
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