MINERALOGICAL MAGAZINE, VOLUME 62A The Cenomanian/Turonian oceanic anoxic event: Response of the atmospheric

The Cenomanian/Turonian (C/T) transition is char-acterized by a world-wide deposition of laminated organic matter-rich marine facies. The absence of benthonic faunas and the low abundance and diversity of planktonic microfossil groups indicates that these sediments were deposited under oxygen deficient conditions (Jarvis et aL, 1988). At the C/T boundary a sharp increase in 13C/12C ratios for marine carbonates and organic matter (OM) is observed (Arthur et al., 1988). This positive isotope excursion of c. 2.5%o is thought to reflect 13C enrichment in oceanic and atmospheric CO2, resulting from an increase in the rate of burial of isotopically light organic arbon (Corg) as a response to the so-called C/T Oceanic Anoxic Event (C/T