Conodont biostratigraphically constrained eruptive duration of Emeishan Large Igneous Province and implication for the end-Capitanian warming

The emplacement and subsequent weathering of Emeishan large igneous province (LIP) have been linked to the climate change at the Guadalupian-Lopingian transition. Though lots of magneto-stratigraphic analysis and radio-isotopic dating works were conducted on the Emeishan LIP, the temporal correlation between Emeishan LIP and climate change is still in debate for the climatic records generally being archived in biostratigraphically dated marine successions. We here logged a Guadalupian-Lopingian limestone dominated succession in the Youjiang Basin located to the southeast of Emeishan LIP. A high-resolution conodont biostratigraphy was obtained for succession and constrained the studied succession in the conodont biozones of J. xuanhanensis, J. granti, and C. dukouensis. There developed multiple tuff and tuffaceous layers in this succession with stratigraphically lower ones geochemically akin to the high-Ti basalt and higher ones akin to the rhyolites of the Emeishan LIP. Analyzed zircons give average U-Pb ages at around 260 Ma and have chemical compositions like those recovered from Emeishan LIP. In coming the paleogeographic location, our petrological, geochemical, Nd-Sr isotopic and zircon U-Pb age and trace element data indicate the identified tuff materials were derived from the volcanic eruption of the Emeishan LIP. According to the established conodont biostratigraphy, the high-Ti basalt volcanism can be constrained in the conodont biozones of J. granti. Based on this biostratigraphically constrained eruption duration of Emeishan LIP, high-Ti basalt eruption can be confidently corrected with the conodont oxygen isotope indicated end-Guadalupian climate warming. Comparing with the rhyolitic tuff rocks, basaltic tuff layers contain a large population of older zircons which might indicate the addition of crustal materials into the basaltic magma enroute to the surface. There might be voluminous CO₂ degassing from the crustal rocks including the carbonates and organic rich mudstones. This degassing in combination with the magmatic CO₂ release and oxidation of buried organic materials in the coastal regions during the regression at that time could increase the atmospheric pCO₂ and resulted in the climate warming.