Multiproxy Geochemical Records of the Carnian Pluvial Episode in Laurasia

The Late Triassic Carnian Pluvial Episode (CPE, ~232 Ma) is characterized by significant changes in climate globally, with conditions shifting from arid to humid and wet, followed by a return to arid conditions. The climatic shift, recorded in multiple stratigraphic sections worldwide, is thought to have been driven by a perturbation of the global carbon cycle, associated with the emplacement of the Wrangellian Terrain Large Igneous Province (WT-LIP, ~231-225 Ma). The event is often linked to profound environmental and biotic change, including the rise and diversification of dinosaurs and the establishment of modern ecosystems. Here we present new high-resolution geochemical and sedimentological data from two Carnian successions from Laurasia: the Knocksoghey Formation of the Mercia Mudstone Group in the Carnduff-2 core, Northern Ireland, representing playa-lake and aeolian deposits, and the De Geerdalen Formation, Kapp Toscana Group in the DH-4 core, Longyearbyen, representing deltaic to shallow-marine settings. Together, these sites provide complementary mid- and high-latitude records of environmental change across the Carnian Pluvial Episode (CPE). We integrate carbon isotopes, elemental compositions, weathering indices, clay mineralogy, and Hg/TOC variations to assess the temporal link between the emplacement of the WT-LIP and the onset of the CPE. In the Knocksoghey Formation, the abrupt emplacement of coarser siliciclastic deposits, known as ‘Skerries’, disrupts otherwise monotonous fine-grained red paleosols, interpreted as evidence of enhanced weathering due to the CPE. These deposits are preceded by elevated Hg concentrations, a negative carbon isotope excursion of ~6‰, and concurrent increases in geochemical weathering proxies. Comparisons of Hg/TOC and δ¹³C data from our records with other localities show a marked increase in the Hg/TOC concurrently with the onset of a stepped negative carbon isotope excursion, similar to other well-characterized LIP-driven climate perturbations (e.g., Toarcian CIE), further supporting the WT-LIP volcanism as the driving mechanism of the CPE.