Intensification of the hydrological and carbon cycles linked to volcanism during theCarnian Pluvial Episode

Abstract

Extreme hydroclimatic changes in the geological record are commonly associated with voluminous greenhouse gas emissions from large igneous provinces. A possible example of this is the Carnian Pluvial Episode (CPE) of the Late Triassic (~233 Ma). The precise temporal relationship between increased hydrological cycling and volcanism at the CPE is unclear, however, as most studies have focused on marine records that provide only indirect and likely delayed evidence of hydrological changes on land. Here we present a multiproxy analysis (including organic carbon isotopes, mercury (Hg) concentrations and isotopes, trace elements, and zircon U-Pb dating) of a terrestrial sedimentary record of the Carnian deposited in the northeastern Paleo-Tethys. We can identify the onset of volcanic activity in this record based on Hg enrichment and near-zero mass independent fractionation of Hg isotopes, which serve as a proxy for volcanism, and find that this onset is broadly coeval with the onset of the CPE and enhanced terrestrial runoff and rapid lake expansion. Enhanced hydrological cycling persisted throughout the CPE. Our results provide a direct link between volcanism and its impact on the hydrological and carbon cycles.