81 / 2025-03-31 13:32:24

High resolution palaeoenvironmental reconstruction at the onset of the Carnian Pluvial Episode in Western Tethys

Triassic,Carnian Pluvial Episode,paleoclimate,redox changes,floral crisis

Theme 3: Earth-Life Co-evolution Through Time > Session 3h: Transient Ocean Deoxygenation in Earth History: Biotic and Abiotic Controls

Multiple negative C-isotope excursions (NCIEs) in sedimentary rocks indicate large emissions of CO₂ into the exogenic reservoirs of the C-cycle during the Carnian Pluvial Episode (CPE) in the early Late Triassic, likely from Wrangellia large igneous province (LIP). Consequently, a relatively long term (1.2-2.5 Myr) global warming could intensify the Late Triassic “mega-monsoon”, enhancing hydrological cycle and perturbing global environments. The CPE is generally considered to be a long interval of generally more humid conditions, but the pattern of the climate change in response to the rapid (< 100 Kyr) initial CO₂ pulse (NCIE1) at the beginning of the CPE, and its impact on the ecosystems remains poorly understood. We performed high-resolution C-isotope analyses, major (XRF) and trace (ICP-MS) element analyses, pyrite framboid diameter measurements at SEM, clay mineralogy (XRD) and palynology across the onset of the CPE in a marine succession from the Dolomites (Italy). We show that in Western Tethys the initial CO₂ emissions in the atmosphere-ocean system did not cause a sudden shift to more humid conditions, but rather strengthened the mega-monsoon seasonality with prolonged and extreme dry seasons. This episodic aridification severely stressed the floral communities and triggered major changes in silicate chemical weathering, resulting in changes in nutrient supply and redox conditions in the basin.