期刊
GEOLOGY
卷 37, 期 9, 页码 819-822出版社
GEOLOGICAL SOC AMER, INC
DOI: 10.1130/G30100A.1
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资金
- ETH Zurich
- TUMSS
- ETH School Domain of Earth, Environment and Natural Resources (SENETH)
- Swiss National Fund [200021-113687]
- MIUR (Italian Ministry of University and Research)-Research Programs of National Interest [2007-2007W9B2WE 001]
The Aptian Oceanic Anoxic Event 1a (OAE1a, ca.120 Ma ago) is one of the most prominent of a series of geologically brief intervals in the Cretaceous characterized by the deposition of organic carbon-rich sediments. OAEs reflect major perturbations in the global carbon cycle evidenced by sedimentary carbon isotope records. However, the triggering mechanisms for OAEs remain controversial. Here we present a bulk-rock and molecular (marine and terrestrial biomarkers) C isotope record at unprecedented time resolution, from the Cismon section of northern Italy, that shows that OAE1a conditions were reached over a period of several thousands of years through a stepwise perturbation of the carbon cycle. The documented sequence of events is most compatible with a trigger associated with increased CO2 emissions, possibly leading to a doubling of pCO(2), which in turn caused larger C isotope fractionation in marine and terrestrial organisms and a major biotic crisis in the calcareous nannoplankton. Our data also show that a release of isotopically light carbon from partial methane hydrate dissociation probably played a minor role in the OAE1a carbon cycle perturbation.
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