The Relationship between Carbon Isotopic Changes and the Sediments Supply at the P-T Boundary in Dongling Section, Jiangxi Province

Key words: 
• carbon isotope /
• Permian-Triassic boundary /
• provenance /
• mass extinction /
• Dongling Section

Abstract: The largest mass extinction event in the Phanerozoic took place at the end of Permian. The cause of this biological crisis is still remaining controversial. This work uses the carbon isotope, major and minor elements across the Permian-Triassic boundary at the Dongling section in the Xiushui city of the Jiangxi Province to study the relationship between the global carbon cycle perturbation and consistent provenance changes and the mass extinction. The results show that the carbonate carbon isotope profile displays stepwise negative excursion. The magnitudes of first and secondary stepwise are 2‰ and 2.5‰, respectively, with a total magnitude of 4.5‰. In the process of stepwise negative excursion of carbon isotope,the provenance of silicate composition in the carbonate rock changes from mafic igneous rocks to island arc intermediate-acid igneous rocks. The later probably concern with the volcanic eruption of Southern China Island. According to negative excursion of carbon isotope has the same time with the change of provenance and ash layer, conjecture it may relate to South China island arc volcanism and volcanism eruption of Siberian large igneous provinces. Large-scale volcanism eruption released or triggered carbon dioxides and methane. These greenhouse gases and the global regression probably are the main causes for this stepwise carbon isotopic excursion across the Permian-Triassic boundary. The deteriorated environments resulted from the volcanism, e.g., global warming, marine anoxia, marine acidification, large sediment influx resulted from vegetation deterioration, lead to the increased pressure of organism existence and thus the mass extinction.