The Carnian Pluvial Episode in the Yanyuan Basin (Southwestern China)

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As one of the hyperthermal events in the Mesozoic, the Carnian Pluvial Episode (CPE) was a global perturbation of the C-cycle and a strong enhancement of the hydrological cycle associated with global warming resulting in significant changes in sedimentary environments from Pangaea to deep water Panthalassa. In this paper, we make research on biostratigraphy, petrology, cyclostratigraphy and geochemistry of the Shemulong Formation in the Yanyuan Basin, at the southwestern of the Yangtze Platform. This strata record the complete deposition of the Carnian stage and preserve the signal of the astronomical orbital period. It also provides good paleontological information which was identified clear biostratigraphic framework. New redox proxies and stable isotopes are analyzed and compare the δ13C data with existing data from other sections of the CPE. In this section, there are at least four terrigenous input pulses which are consisted of sandstone and mudstone, causing the abrupt shutdown of carbonate production during the CPE period. Meanwhile, biodiversity data like bivalves, conodonts and ammonoids in the study area show a major change in abundance and variability during the CPE period. These are also coincident with negative carbon isotope excursions (NCIE), proving the close correspondence between the perturbation of the carbon cycle (and related hyperthermal events occur) and the turnover of depositional systems and ecosystems. Furthermore, we found differences in the recovery of carbonate production after each terrigenous input. The degree of recovery decreases and then increases upwards (bioclastic limestones - oolitic limestones - bioclastic limestones - biostrome - reef mound). It may link to the intensity of the terrigenous input pulse. In summary, this research provides more comparative schemes in the eastern Tethys for the collaborative study of environment biological co-evolution relationship within the CPE interval and is of positive significance for the in-depth understanding of climate and biodiversity changes through hyperthermal intervals in Earth history.AcknowledgementsThis work was supported by the National Natural Science Foundation of China (No. 41972120; 42172129), by the State Key Laboratory of Palaeo-biology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS) (No.173131).