A high-resolution (cm-scale) carbon-isotope stratigraphic study has been carried out at San Lorenzello (Matese Mountains, southern Apennines, Italy), on a shallow marine carbonate section, previously correlated with coeval sections by using a combination of biostratigraphic, cyclostratigraphic and sequence-stratigraphic criteria. This succession, deposited along the southern margin of the Alpine Tethys, is Late Valanginian - Early Hauterivian in age; it consists of a hierarchy of shallowing-upward cycles (elementary cycles, bundles and superbundles), linked to Earth’s orbital oscillations. We estimate that the influence of the depositional environment and diagenesis on the δ13C signal is negligible and that the carbon-isotope composition of bulk carbonate, as well as individual grains, indicate a similar response to an original climate-ocean forcing. No clear relationship emerges between the δ13C variations and the sea-level changes. The long-term δ13C oscillations have been correlated with the coeval curves from the emipelagic La Charce (Vocontian Basin, France) and from the pelagic Capriolo (southern Alps, northern Italy) sections. This comparison suggests that the C-isotope signature is well preserved at San Lorenzello, where only the upper part of the Valanginian carbon isotope global excursion is recorded in the outcrop. The available data allowed us: (a) to relate the shallow-marine stratigraphic record with the ammonite and nannofossil biozonation and the magnetostratigraphy; (b) to identify the Valanginian-Hauterivian boundary in the studied shallow-marine deposits on the basis of high-resolution carbon-isotope correlation with the La Charce and Capriolo sections; (c) to suggest that the time duration of about 2.9 my, estimated by orbital chronostratigraphy in the San Lorenzello section, is comparable with the ± 3 my reported for the same stratigraphic interval in Channell et al. (1995) and Gradstein et al. (2004).
File in questo prodotto:
Non ci sono file associati a questo prodotto.