The end-Triassic mass extinction: A new correlation between extinction events and δ13C fluctuations from a Triassic-Jurassic peritidal succession in western Sicily

A new δ13Ccarb curve was obtained from an expanded peritidal succession in western Sicily and was used to
investigate the relationships between isotopic signatures and biological events on carbonate platforms across
the Triassic-Jurassic boundary (TJB). The resulting curve shows two main negative carbon isotopic excursions
(CIEs) that fit well with the “Initial” and “Main” CIEs that are recognized worldwide and linked to the End-
Triassic Extinction (ETE). In the studied section, the first negative CIE marks the disappearance of the large
megalodontids, which were replaced by small and thin-shelled specimens, while the “Main” CIE corresponds
to the last occurrence (LO) of the megalodontids and, approximately 50m upsection, to the total demise of the
Rhaetian benthic foraminifer community. Upward, the carbon curve shows a positive trend (ca. +1‰) and a
gradual recovery of the benthic communities after an approximately 10 m-thick barren interval populated
only by the problematic alga Thaumatoporella parvovesiculifera.
A comparison between the Mt. Sparagio δ13Ccarb curve and other coeval Ccarb and Corg curves from carbonate
platform, ramp and deep basin successions indicates similar isotopic trends; however, the diverse magnitudes
and responses of benthic communities confirmthat the carbon cycle perturbations have been globally significant,
and were influenced by external forces such as CAMP volcanism. The multiphase nature of the extinction pulses
could have been caused by local environmental changes related to transgression/regression phenomena. Overall,
this study adds new data and a new timing to the effect of the acidification process on carbon productivity and
benthic communities in different environments across the TJB.