Latest Permian and earliest Triassic geomagnetic polarity timescale: A polarity reversal marks the greatest mass extinction

The establishment of the latest Permian geomagnetic polarity time scale has been inhibited by the inconsistent polarity patterns published by different teams for the section at Meishan, which hosts the Global Boundary Stratotype Section and Points (GSSPs) for the Permian-Triassic boundary (PTB) and base of the underlying Changhsingian Stage. We have analyzed the magnetostratigraphy of the Shangsi section, the former candidate for the PTB GSSP, and the alternate Chaotian section in South China to compile a reliable geomagnetic polarity timescale spanning the late Wuchiapingian and Changhsingian (Late Permian) to early Induan (Early Triassic). The late Wuchiapingian to early Changhsingian is dominated by normal polarity (chron “LP2n” of Hounslow and Balabanov, 2018) with three reversed-polarity subchrons (LP2n.0r to LP2n.2r) within the Clarkina wangi conodont Zone. The mid to late Changhsingian is dominated by reversed polarity, with the onset of this chron “LP2r” in the C. changxingensis Zone. The biostratigraphic placement of the brief normal-polarity chron “LP3n” of the late Changhsingian is within the C. yini Zone. The reversed-polarity chron “LP3r” of the latest Changhsingian (late C. yini to C. meishanensis Zones) is succeeded by the normal-polarity chron “LT1n” that spans from the very latest Changhsingian into the early Griesbachian substage of the basal Triassic. The onset of this chron LT1n coincided with the lowest occurrence of Hindeodus changxingensis, which is just after the onset of the latest Permian mass extinction in South China and slightly prior to the PTB. The integration of conodont biozones, carbon isotope excursions and the revised magnetostratigraphy composite from the Shangsi and Chaotian sections produces a high-resolution consistent sequence of the latest Permian mass extinction (LPME), the onset of chron LT1n and then the PTB; thereby enabling high-resolution global correlation of these latest Permian to basal Triassic events.