Massive changes in marine sedimentation rates during the Carnian Pluvial Episode (Late Triassic)

Abstract

The Carnian is marked by major environmental changes, including multiple carbon-cycle perturbations, global warming and enhanced hydrological cycling that have been linked to the effects of the emplacement of Wrangellia large igneous province. The environmental perturbations occurred in an interval of about 1–2 Myr between the Julian 2 and the base of the Tuvalian 2. This interval is named Carnian Pluvial Episode (CPE). The widespread and pronounced sedimentological changes observed in marine sedimentary records, which abruptly shift towards mainly siliciclastic deposition, point to general higher continental runoff during the CPE. However, quantification of actual changes in sediment flux to marine basins is still lacking. We calculated changes in linear and relative sedimentation rates in Carnian well age-constrained marine successions. During the Julian 2, the lithological changes are coupled to increases of up to ca. 3000% in relative sedimentation rates in the marine sequences of Western Tethys and Panthalassa, and to slight decreases (< -100%) in sedimentation rates in successions of Eastern Tethys. Sedimentation rates then decrease in the Tuvalian 1 in all the successions. The higher siliciclastic delivery to the basins is likely the result of the interplay of higher precipitation and continental runoff under conditions of higher atmospheric pCO2, eustatic sea-level changes and local depositional contraints, which could all be relatable to the effects of volcanic gases emissions from Wrangellia large igneous province.