Global carbon cycle perturbations triggered by volatile volcanism and ecosystem responses during the Carnian Pluvial Episode (late Triassic)

The Carnian Pluvial Episode (CPE) was a dramatic climatic event during the early Late Triassic. The CPE has been recognized worldwide and is marked by the termination of carbonate platform successions and by pronounced negative δ¹³C excursions (denoted as the CPE excursion). The onset of the CPE has been proposed to be linked with the volatile eruption of the Wrangellia Large Igneous Province (W-LIP). However, this extreme climatic event remains disputed in terms of its precise global correlation, timing of onset, duration, and global magnitude. We compiled a database of 13 conodont biozone-controlled stable-isotope reference sections throughout the Tethyan region. After a reexamination of previously published conodont taxonomy from each section, the statistics on the conodont assemblages/zones yield a global set of 17 high-resolution conodont Unitary Association Zones (UAZs) spanning the entire Carnian successions. A set of age-tie points placed an age model on this global UAZ scale. We added paired δ¹³C_carb and δ¹³C_org data from two sections in South China to other records in this global database, and then normalized all carbon-isotope datasets. A pronounced negative δ¹³C_carb excursion with a magnitude of -2± 0.5‰ (from an average of ~3‰ to ~1‰) is evident in these normalized trends and is recognized around the entire Tethys realm. The CPE excursion coincides with conodont UAZ-4 (~234 Ma) through UAZ-8 (within the Mazzaella carnica and Paragondolella praelindae zones, Julian2) and has a duration of ca. 1.5 Myr. We note that an apparent delayed onset of the CPE excursion in South China relative to elsewhere in the Tethys as suggested by previous studies may have been an artifact caused by incomplete conodont-stratigraphic records and/or irregularities in taxonomic identification. A carbon and phosphorus cycle model highlight the strong relationship between the eruption of the W-LIP and CPE excursion; however, the estimated amount of CO₂volatiles released by the W-LIP would directly account for only ~25% of the total amount of light-carbon required to explain the combined magnitude and duration of the global CPE excursion.