Carbon Cycle Perturbations during the Carnian Pluvial Episode: Insights from Organic Carbon Isotopes, Charcoal and Mercury in the Paleo-Antarctic Circle

Organic geochemical and isotopic proxies preserved in continental archives provide critical insights into past climate perturbations and carbon-cycle dynamics, yet their application to high-latitude terrestrial records remains limited. Here, we present a new, high-resolution dataset of organic carbon isotopes (δ¹³Corg), charcoal, and mercury from the BIC-5 core from Tasmania, providing a southern high-latitude perspective on the Carnian Pluvial Episode (CPE). Bulk organic carbon isotopes (δ¹³Corg) reveal four pronounced negative carbon-isotope excursions (NCIE 1–4), with values reaching –27 to –29‰, recording repeated carbon-cycle perturbations characteristic of the CPE. Three of these isotopic shifts (NCIE 1, 3, and 4) are systematically accompanied by elevated Hg/TOC ratios, suggesting Hg input occurred synchronous with the carbon-cycle disruption. Sediments in the BIC-5 core are dominated by terrestrial organic matter, and peaks in Hg/TOC occur alongside elevated charcoal abundances, suggesting enhanced wildfire activity and rapid sequestration of organic carbon. The close stratigraphic coupling of δ¹³Corg excursions and Hg anomalies supports either a direct volcanic driver for the environmental perturbations recorded in the BIC-5 core or anomalous wildfire activity that, in turn, may indirectly link to volcanic activity. Comparison with coeval δ¹³Corg and Hg records from low- and mid-latitude sections in Europe, Asia, and other Gondwanan sites reveals strong synchronicity in excursion timing and magnitude, demonstrating that the BIC-5 record captures a globally coherent signal, most plausibly associated with pulsed magmatic activity of the Wrangellia Large Igneous Province and coeval volcanic centres in the Panthalassan–Tethyan realm. This study highlights the combined application of organic carbon isotopes, charcoal and Hg as complementary proxies for reconstructing extreme paleoclimate events, emphasising their robustness across depositional environments and paleolatitudes, and providing a high-latitude perspective on the mechanisms driving the Carnian Pluvial Episode.