Terrestrial mercury anomalies across the Permian-Triassic transition in North China linked to volcanism

The Permian-Triassic mass extinction (PTME) is the most severe biological crisis in Earth history and is closely linked to massive contemporaneous volcanism. However, there is currently limited evidence of Mercury (Hg) enrichment directly from volcanic sources in terrestrial strata, necessitating evidence from different regions and latitudes to confirm the relationship between volcanism and changes in terrestrial environments and biotas. To explore this connection, we conducted a comprehensive analysis integrating astronomical cycles to provide a temporal framework, Hg concentrations, and Hg isotopes from terrestrial strata in the Yiyang Coalfield, located in the southern North China Plate (NCP). Our high-resolution astronomical timescale reveals that in the low latitude NCP the PTME commenced on land with the end-Permian Terrestrial Collapse (EPTC) which preceded the marine mass extinction by approximately 270 kyr and was latitudinally diachronous. The EPTC commenced in high-to-mid latitudes (75–30°S), then approximately 100–430 kyr later spread through different mid-to-low latitude regions (60–20°N) into equatorial paleolatitudes (10°N–0°). Hg isotopic results show that the initial Hg enrichment peak during the EPTC originated from terrestrial weathering and wildfire combustion rather than directly from volcanism, whereas the three subsequent Hg enrichment peaks over a 500 kyr interval following the EPTC originated directly from volcanism. This temporal coupling suggests that terrestrial ecosystems exhibited greater sensitivity and a more rapid response to global warming than marine ecosystems. Stratigraphic correlations show the early eruptive phase of the Siberian Traps Large Igneous Province (STLIP) led to gradual collapse of terrestrial ecosystems from high to low latitudes as they responded to increasingly warmer and more stressed conditions. The main eruptive phase of the STLIP, potentially augmented by contemporaneous widespread volcanism, may have ultimately led to the final collapse of terrestrial ecosystems and marine extinctions.