Strong climate seasonality at the onset of the Carnian Pluvial Episode in Northwestern Tethys (Late Triassic)

The Late Triassic “megamonsoon” circulation was profoundly perturbed by large igneous province (LIP) volcanism during the so-called Carnian Pluvial Episode (CPE). C-isotope excursions in sedimentary records indicate large CO₂ emissions into the exogenic reservoirs of the C-cycle during the CPE. The consequent global warming would have strongly intensified the “megamonsoon”, enhancing the hydrological cycle and perturbing global environment for a relatively long time (1.2–2.5 Myr). However, the pattern of the climate change during the rapid (maximum 110 Kyr) initial Negative C-isotope excursion (NCIE1) of the CPE remains poorly understood. Here, we performed high-resolution C-isotope analyses, major (XRF) and trace (ICP-MS) element analyses, clay mineralogy (XRD) and palynology across CIE-1 in a marine succession from the Dolomites (Italy). We show that in the northwestern Tethys the transition to more persistent wet conditions was interrupted by episodic intervals with “megadroughts” linked to discrete rapid emissions of CO₂ in the atmosphere–ocean system. These rapid (<50 Kyr) climate swings severely stressed the floral communities and triggered major changes in silicate chemical weathering, resulted in changes in nutrient delivery and redox conditions in the basin.