Episodic aridification at the onset of the Carnian Pluvial Episode in Western Tethys

During the Carnian Pluvial Episode (CPE; Late Triassic), repeated emissions of CO2 into the exogenic reservoirs of the C-cycle, likely from large igneous province (LIP) volcanism, caused relatively long-term warming and perturbed mega-monsoon circulation. A general long-term (>1 Myr) shift to more humid conditions is observed in many geological records during the CPE, but the pattern of climate change in response to the initial rapid CO2 pulse (<100 Kyr) and its immediate effects on ecosystems remain, however, poorly understood. Here, we performed high-resolution multi-proxy analyses across the onset of the CPE in a marine succession of Western Tethys, including palynology, mineralogy and geochemistry. We show that in these tropical regions the initial CO2 emissions into the atmosphere–land–ocean system at the onset of the CPE did not cause a sudden increase in humidity but rather resulted in a succession of relatively rapid (likely <50 Kyr) climate swings. Short intervals dominated by episodic aridification alternated with periods of higher moisture, modulating the intensity of silicate chemical weathering on land and the modes of sediment transport to the marine basin. The abrupt climate swings caused changes in the composition of terrestrial floral and a substantial reduction in plants generic richness in the basin’s catchment area. Notably, plants exhibiting modern-type characters rose during this phase. After the CPE’s initial C-cycle perturbation, the environment in Western Tethys remained more persistently humid, but plants generic richness did not recover, pointing to a longer term vegetation crisis.

During the Carnian Pluvial Episode (CPE; Late Triassic), repeated emissions of CO2 into the exogenic reservoirs of the C-cycle, likely from large igneous province (LIP) volcanism, caused relatively long-term warming and perturbed mega-monsoon circulation. A general long-term (>1 Myr) shift to more humid conditions is observed in many geological records during the CPE, but the pattern of climate change in response to the initial rapid CO2 pulse (<100 Kyr) and its immediate effects on ecosystems remain, however, poorly understood. Here, we performed high-resolution multi-proxy analyses across the onset of the CPE in a marine succession of Western Tethys, including palynology, mineralogy and geochemistry. We show that in these tropical regions the initial CO2 emissions into the atmosphere–land–ocean system at the onset of the CPE did not cause a sudden increase in humidity but rather resulted in a succession of relatively rapid (likely <50 Kyr) climate swings. Short intervals dominated by episodic aridification alternated with periods of higher moisture, modulating the intensity of silicate chemical weathering on land and the modes of sediment transport to the marine basin. The abrupt climate swings caused changes in the composition of terrestrial floral and a substantial reduction in plants generic richness in the basin's catchment area. Notably, plants exhibiting modern-type characters rose during this phase. After the CPE's initial C-cycle perturbation, the environment in Western Tethys remained more persistently humid, but plants generic richness did not recover, pointing to a longer-term vegetation crisis.