Nutrients and Marine Redox Changes During the CPE-Event1 (late Triassic) in the Dolomites (southern Alps, Italy)

The climate of the Late Triassic was perturbed by a 1.2–2.5 Ma interval of repeated carbon-cycle perturbations, during which discrete environmental and biological events have been identified, collectively representing the Carnian Pluvial Episode (CPE). In sedimentary records, these CPE’s events are marked by multiple negative C-cycle excursions (NCIEs), indicating injections of 13C-depleted CO2 into the exogenic reservoirs of the C-cycle. Enrichments in sedimentary Hg during the NCIEs and 187Os/188O isotope data suggest a volcanic origin for this isotopically light CO2, likely related to the emplacement of the coeval Wrangellia Large Igneous Province. Increased volcanic CO2 emissions led to a rise of global temperatures, which intensified the hydrological cycle and promoted a transition toward a more humid climate. In Western Tethys, it has been shown that the shift to more persistent humid conditions during the CPE Event associated with NCIE1 (i.e. CPE-Event1) was stepwise, occurring through a series of rapid (< 50 Kyr) arid-humid climate swings driven by discrete pulses of CO2. While in the terrestrial environment clay mineral assemblages and detrital proxies indicate that these climatic swings influenced the rates of chemical weathering and the mechanism of sediment transport to the marine basin, as well as triggering a profound crisis in terrestrial flora, the impact of this rapid climate change on the marine environment remains poorly understood. We performed high-resolution C-isotope analyses, major (XRF) and trace (ICP-MS) element analyses, and pyrite framboid size measurements (SEM) across the stratigraphic interval recording the CPE-Event1 in two marine successions from the Dolomites (Southern Alps, Western Tethys; Italy). Our results reveal the links between climate change and marine environmental perturbations in the Dolomites, providing new insights into nutrient dynamics and the development of oxygen-depleted conditions during the CPE-Event1.