Organic carbon isotope (δ13Corg) curve and extinction trends across the Triassic/Jurassic boundary at Mt. Sparagio (Italy): A tool for global correlations between peritidal and pelagic successions

The Triassic/Jurassic boundary (TJB, 201.3 Ma) is characterized by profound turnovers in both marine and terrestrial biota, known as end-Triassic mass Extinction event (ETE). During this severe event, distinct negative carbon isotope excursions (CIEs) have been globally observed, and they were linked to volcanogenic emissions or methane release by dissociation of clathrates. The triggering factor of the negative CIEs was attributed to the emplacement of the Central Atlantic Magmatic Province (CAMP) and the break-up of the Pangea. Specifically, three significant carbon-cycle disruptions named Precursor, Initial and Main CIE have been recorded in several stratigraphic successions deposited in terrestrial and pelagic environments. We investigated the organic carbon isotope curve from the subtidal facies of the Mount Sparagio section (Sicily, Italy), which is a continuous peritidal succession representing an Upper Triassic to Lower Jurassic carbonate platform edging the south-western side of the Tethys Ocean. For the first time, we achieved a complete profile of organic carbon stable isotopic composition (δ13Corg) during the end-Triassic mass Extinction event (ETE) in a carbonate shallow water environment. The δ13Corg profile highlights the 3 negative excursions that characterized the Triassic/Jurassic boundary time interval in pelagic and deep-water successions. The documented CIEs correspond to significant biotic turnovers recognized along the Mt. Sparagio section, suggesting that also the Upper Triassic-Lower Jurassic carbonate platforms were affected by the onset of the Central Atlantic Magmatic Province. Furthermore, although the Mt. Sparagio section has been studied in detail for microfacies associations and it is well biostratigraphically constrained with shallow marine macro- and microfossils, only the documented δ13Corg negative shifts allowed to correlate peritidal environments to pelagic successions, making the organic carbon curve (δ13Corg) a powerful tool for global correlations.