Mariano Parente, Gianluca Frijia, and Matteo Di Lucia
Carbon-isotope stratigraphy of Cenomanian-Turonian platform carbonates from the Southern Apennines (Italy); a chemostratigraphic approach to the problem of correlation between shallow-water and deep-water successions
Journal of the Geological Society of London (May 2007), 164(3):609-620

Abstract:
The carbon-isotope record of three sections of shallow-water carbonates from the Upper Cretaceous sequences of the southern Apennines (Italy) shows a pronounced positive excursion of about 4-5 per mil. Using the upper Cenomanian Cisalveolina fraasi level as a biostratigraphic tie-point we correlate this excursion to the OAE-2 isotopic event. Comparison with the standard reference delta ¹³ C curve of Eastbourne (England) shows that the overall character of the excursion is clearly reproduced in the shallow-water curves. Chemostratigraphic correlation allows definition of the age of some important shallow-water biostratigraphic events to the precision of an ammonite zone, using the well-established bio-chronostratigraphic framework defined in the Eastbourne section. The onset of the Cenomanian-Turonian isotopic excursion coincides with a transgressive trend, recorded by the occurrence of more open-marine facies and culminating with an incipient drowning in one of the sections studied. Our data suggest that the open-ocean isotopic signal is most faithfully recorded and preserved in shallow-water platform carbonates during transgressive periods, when the effects of meteoric diagenesis and seawater ageing are less severe.