Synchronous end-Permian mass extinction zenith in marine and low-middle latitude terrestrial North China

The end-Permian mass extinction was the most severe biotic crisis of the Phanerozoic, yet temporal synchrony between marine and terrestrial extinctions remains debated due to correlation uncertainties. Here, we present an integrated magnetostratigraphic, cyclostratigraphic, and carbon-isotope and mercury (Hg) chemostratigraphic record from the fluvial Upper Shihhotse, Sunjiagou, and Liujiagou formations at the Sigou section, North China. We identify 14 magnetozones spanning the late Changhsingian to late Olenekian, constrained by a floating timescale based on gamma-ray cyclostratigraphy and subsequently anchored through magnetostratigraphic correlation. Our chronostratigraphy reveals a Hg peak at 252.4 Ma, aligning with the main eruptive phase of the Siberian Traps Large Igneous Province, while the carbon isotope excursion onset (252.1 Ma) and minimum (252.0 Ma) are synchronous with the Meishan Global Stratotype Section and Point. Furthermore, the Induan-Olenekian boundary is positioned below magnetozone SG4n, constraining the Induan Stage duration to 1.6 to 1.8 My. These findings establish a high-resolution chronostratigraphic framework for the Permian-Triassic boundary in North China, supporting a synchronous extinction zenith across marine and low-middle latitude terrestrial ecosystems, with latitudinal diachroneity relative to high-latitude and tropical landmasses.