Carbon Cycle Perturbance During the Carnian Pluvial Episode (Larne Basin, Northern Ireland)

Abstract. The Late Triassic Carnian Pluvial Episode (CPE, ~232 Ma) marks a major global climatic transition characterized by intensification of humid conditions following a prolonged period of aridity through much of the Triassic. This episode triggered profound environmental and biotic change that ushered in modern environments and ecosystems. Here, we present a new high-resolution integrated geochemical and sedimentological record from the Knocksoghey Formation, Mercia Mudstone Group, in the Larne Basin, Northern Ireland. The high-resolution organic carbon isotopes document a ~4 ‰ negative excursion, whose onset coincides with a small, reproducible rise in Hg concentrations from background levels, thought to be associated with the emplacement of the Wrangellia Large Igneous Province (LIP). The geochemical anomalies stratigraphically closely precede a pulse of coarse siliciclastics, indicative of intensified weathering driven by enhanced rainfall, and are followed by a return to arid, restricted conditions, marked by deposition of stacked anhydrite nodules and beds. The CPE was previously suggested to be characterized by a succession of negative carbon isotope excursions (NCIEs) in sedimentary archives. However, our new data demonstrates a more protracted stepped carbon cycle perturbance, as reflected by a single, stratigraphically prolonged carbon isotope excursion, comparable in nature to NCIEs observed during other LIP-driven climatic perturbations, such as the Toarcian Oceanic Anoxic Event.