Carbon-isotope stratigraphy of upper Barremian−lower Albianshallow-water carbonates of the southern Apennines (Italy): high resolution correlation with deep-water reference sections

The middle Cretaceous was a period of repeated perturbations of the global carbon cycle. High atmospheric pCO2 has been invoked as the main cause of middle Cretaceous super greenhouse, Oceanic Anoxic Events (OAEs) and biocalcification crises recorded by calcareous nannoplankton (WEISSERT & ERBA, 2004). Most of what we know on these events was derived from the study of geochemical proxies and biotic change in deep-water sequences. Comparatively much less is known from shallowwater carbonate systems. The full exploitation of the information contained in these archives is often hampered by the diagenetic processes, the low biostratigraphic resolution and the lack of well-defined correlations with biochronological standard schemes based on ammonites and calcareous plankton and nannoplankton. Secular changes in the δ13C composition of sea-water have been well documented in Lower Cretaceous pelagic and hemipelagic sequences from different localities (HERRLE et alii, 2004, and references therein) and during the last 20 years C-isotope stratigraphy has been increasingly used to correlate shallow-water carbonate with deep-water sequences. This tool has been recently applied also to the southern Apennines carbonate platform (D’ARGENIO et alii, 2004; PARENTE et alii, 2007). The successful application of the δ13C record as a stratigraphic tool in shallow-water carbonate sections requires that the degree of preservation/alteration of the original isotopic signal is correctly evaluated and that independent tie points are established to facilitate correlation with the reference curve. In this study we present high-resolution δ13C curves of two Barremian-Albian shallow-water carbonate sections of the central-southern Apennines (Italy) (fig. 1): Monte Croce (north of Itri, Lazio) and Monte Motola (south of Salerno, Campania).