Abstract
Abstract. Low biostratigraphic resolution and lack of chronostratigraphic calibration hinder precise correlations between platform carbonates and coeval deep-water successions. These are the main obstacle when studying the record of Mesozoic oceanic anoxic events in carbonate platforms. In this paper carbon and strontium isotope stratigraphy are used to produce the first chronostratigraphic calibration of the Barremian-Aptian biostratigraphy of the Apenninic carbonate platform of southern Italy. According to this calibration, the segment of decreasing δ13C values, leading to the negative peak that is generally taken as the onset of the Selli event, starts a few metres above the last occurrence of Palorbitolina lenticularis and Voloshinoides murgensis. The following rise of δ13C values, corresponding to the interval of enhanced accumulation of organic matter in deep-water sections, ends just below the first acme of Salpingoporella dinarica, which roughly corresponds to the segment of peak δ13C values. The whole carbon isotope excursion associated with the oceanic anoxic event 1a is bracketed in the Apenninic carbonate platform between the last occurrence of Voloshinoides murgensis and the "Orbitolina level", characterized by the association of Mesorbitolina parva and Mesorbitolina texana. Since these bioevents have been widely recognized beyond the Apenninic platform, the calibration presented in this paper can be used to pinpoint the interval corresponding to the Early Aptian oceanic anoxic event in other carbonate platforms of central and southern Tethys. This calibration will be particularly useful to interpret the record of the Selli event in carbonate platform sections for which a reliable carbon isotope stratigraphy is not available.
Highlights
The Early Aptian oceanic anoxic event 1a (OAE1a), known as the Selli event, was a time of severe perturbation of the global carbon cycle
The nomenclature of the Lithofacies Associations (LA) conforms to that adopted by previous Authors for the Lower Cretaceous carbonates of the Apenninic carbonate platform and of other carbonate platforms of the central-southern Tethyan domain (Raspini, 2001; Pittet et al, 2002; Hillgartner et al, 2003; D’Argenio et al, 2004; Bachmann and Hirsch, 2006)
In this paper this task is fulfilled by integrating carbon isotope stratigraphy and biostratigraphy, with additional support by strontium isotope stratigraphy on a limited set of samples
Summary
The Early Aptian oceanic anoxic event 1a (OAE1a), known as the Selli event, was a time of severe perturbation of the global carbon cycle. While the long-lived Urgonian platform was drowned shortly before the onset of the OAE1a (Wissler et al, 2003; Follmi et al, 2006; Huck et al, 2011), some carbonate platforms in the central and southern Tethys were able to continue growing in shallow water. These resilient platforms preserve the record of palaeoecologic disturbance of tropical
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