Chemo- and biostratigraphic correlation of the CPE (Carnian Pluvial Episode, Late Triassic) in the Western Tethys: Implications for environmental perturbation prior to the CPE

The Carnian Pluvial Episode (CPE), characterized by global warming, enhanced hydrological cycle, and major biotic turnovers, represents a key Late Triassic interval of global carbon-cycle perturbation and climate change. Chemostratigraphy provides the principal framework for the global correlation of CPE successions, but inaccurate biostratigraphic calibration of carbon-isotope records can lead to miscorrelation of negative carbon isotope excursions (NCIEs). New bulk organic carbon isotope, microfacies, conodont, and foraminifer data from six successions in the Transdanubian Range (TR, Western Hungary), combined with revised biostratigraphic constraints, required the recalibration of previously published carbon-isotope curves. The revised framework shows that the lower Veszprém Formation, recording increased clastic input and the previously recognized CPE NCIE-1, belongs to the Julian 1 ( Aon–Aonoides Subzone). Microfacies and foraminiferal assemblages further indicate that the microbial-skeletal carbonate factory of the Wetterstein reef system remained active during the deposition of the lower Veszprém Formation. Consequently, this excursion is reinterpreted as a Pre-CPE NCIE, an interval of elevated terrestrial input but only moderate ecosystem disturbance. The onset of the CPE is placed at a pronounced NCIE in a higher stratigraphic position, formerly known as the CPE NCIE-2, coinciding with the final demise of the carbonate platform and major ecological reorganization. Peak environmental stress characterized by abundant hygrophytic palynomorphs, temporary collapse of marine microbiota or low-diversity stressed communities, was confined to the late Julian 2. Recovery began in the early Tuvalian with renewed shallow-water carbonate production despite continued minor carbon-cycle perturbations and fluctuating terrestrial input, indicating prolonged environmental instability, with the most severe biotic disruptions concentrated at the onset of the CPE and the end of Julian 2.