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 refl ect 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 pCO2, 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.
A volcanic CO2 pulse triggered the Cretaceous Oceanic Anoxic Event 1a and a biocalcification crisis / S. Mehay, C.E. Keller, S.M. Bernasconi, H. Weissert, E. Erba, C. Bottini, P.A. Hochuli. - In: GEOLOGY. - ISSN 0091-7613. - 37:9(2009), pp. 819-822.
|Titolo:||A volcanic CO2 pulse triggered the Cretaceous Oceanic Anoxic Event 1a and a biocalcification crisis|
BOTTINI, CINZIA (Penultimo)
|Settore Scientifico Disciplinare:||Settore GEO/02 - Geologia Stratigrafica e Sedimentologica|
Settore GEO/01 - Paleontologia e Paleoecologia
|Data di pubblicazione:||2009|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1130/G30100A.1|
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