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M. Di Lucia, M. Mutti, and M. Parente

 

Bio-chemostratigraphy of the Barremian–Aptian shallow-water carbonates of the southern Apennines (Italy): pinpointing the OAE1a in a Tethyan carbonate platform  

 

Solid Earth, 3, 1–28, 2012
www.solid-earth.net/3/1/2012/

 

doi: 10.5194/se-3-1-2012

 

 

 

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 areused 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 d13C 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 ∂13C 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 d13C 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 recognizedbeyond the Apenninic platform, the calibration presentedin this paper can be used to pinpoint the interval correspondingto the Early Aptian oceanic anoxic event in othercarbonate platforms of central and southern Tethys. This calibrationwill be particularly useful to interpret the record ofthe Selli event in carbonate platform sections for which a reliablecarbon isotope stratigraphy is not available.

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