Episodic magmatism at the Permian/Triassic crisis boundary and its linkage to underlying source rocks: constraints from conodont-based high-resolution geochemical proxies in marine carbonate successions, South China

Abstract

Frequent magmatism was a major event causing the mass extinction across the Permian/Triassic Boundary. In the current study, we determined magmatism characteristics from the Pingdingshan section at the Permian/Triassic Boundary using conodont-based geochemical proxies at a high-resolution scale (~ 50 kyr). Integrated trace elements (Mn, Sr, Rb, and Th) and stable/radioactive isotopes (δ¹⁸O, δ¹³C, and ⁸⁷Sr/⁸⁶Sr) revealed that conodonts provided an ideal proxy for chemostratigraphic signatures of ancient seawater. The conodont-based, high-resolution ⁸⁷Sr/⁸⁶Sr isotopes from the studied interval (250.50–252.00 Ma) displayed three decreasing cycles upwardly against a long-term increasing background, reflecting three episodes of magmatism. As a contrast, the conodont-based, high-resolution δ¹⁸O isotopes from this interval exhibited no episodic pattern, indicating that the δ¹⁸O isotopes of conodonts were limitedly influenced by marine magmatism. The high-resolution δ¹³C values of micrites displayed a pattern consistent with the trend of long-term background, revealing that the δ¹³C signatures of episodic magmatism were not inherited by micrites. The magmatism associated with the EPME event exerted great influences upon the Chihsian source rocks by introducing massive heat through hydrothermal fluids and causing pervasive oceanic anoxia.

Graphical abstract