Zhongya Hu a, Weiqiang Li b , Robert J. Newton c , Sylvain Richoz d , Yasufumi Iryu e , Satoshi Takahashi f , Takumi Maekawa g , Zhiguang Xia b h , Shouye Yang a , Shu-Zhong Shen b , Hua Zhang i
a State Key Laboratory of Marine Geology, Tongji University, Shanghai, China
b State Key Laboratory of Critical Earth Material Cycling and Mineral Deposits, Nanjing University, Nanjing, China
c School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
d Department of Earth and Environmental Sciences, Lund University, Lund, 223-62, Sweden
e Advanced Institute for Marine Ecosystem Change (WPI-AIMEC), Tohoku University, Sendai, 980 8578, Japan
f Department of Earth and Environmental Sciences, Nagoya University, Nagoya, 464-8601, Japan
g Osaka Museum of Natural History, 1-23 Nagai Park, Higashi-sumiyoshi-ku, Osaka, 546-0034, Japan
h Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu, China
i State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China
Abstract: The pronounced spatial heterogeneity in the severity of the end-Permian mass extinction is suggested as the result of changes in oceanic connectivity, which regulate the buffering capacity of marine environments against global perturbations. However, direct geochemical constraints remain limited. Magnesium isotopes (δ26Mg) of seawater serve as a sensitive tracer for oceanic restriction. Here, we present reconstructed seawater δ26Mg records from the Neo-Tethys and Panthalassa oceans and compare them with existing data from the Paleo-Tethys. Our results reveal a fundamental divergence: seawater δ26Mg remained stable (−0.4‰ to −0.3‰) in the Neo-Tethys and Panthalassa across the Permian–Triassic transition, whereas it increased by more than 0.5‰ in the Paleo-Tethys. This contrast suggests that the Neo-Tethys was effectively connected to the vast, well-buffered Panthalassa Ocean, while the Paleo-Tethys was a more restricted basin. Mass balance modeling suggests that the open Panthalassa/Neo-Tethys system maintained a significantly larger Mg reservoir and greater capacity to buffer external changes, thereby supporting relatively stable environmental conditions. However, the restricted Paleo-Tethys is more sensitive to chemical disturbances, potentially leading to more pronounced environmental stress. Our Mg isotope data provide geochemical constraints on ocean connectivity and suggest that differences in buffering capacity may have played an important role in shaping the spatial heterogeneity of biotic catastrophe during the end-Permian mass extinction. The degree of restriction and inter-basin exchange in deep-water areas warrant further investigation.
Full Article: https://doi.org/10.1016/j.epsl.2026.120191
