Deep-water osmium-isotope record of the Permian–Triassic interval from Niushan, China reveals potential delayed volcanic signal post the mass extinction

Abstract

The end Permian mass extinction event is one of the most severe biotic crisis of the Phanerozoic. The trigger of this event has been widely linked to massive volcanic activity associated with the Siberian Traps Large Igneous Province through the application of multiple geochronological (e.g., Usingle bondPb and Arsingle bondAr dating) and geochemical proxies (e.g., C, Hg, Zn, Os, etc.). Of these proxies, a few osmium (187Os/188Os) records are available for near-shore/shallow water depositional settings (e.g., Meishan, China; Opal Creek, Canada), which suggest multiple episodes of volcanism before, during and after the mass extinction event. Here, we present a new initial 187Os/188Os (Osi) stratigraphy across the deep-water Niushan Permian–Triassic boundary interval section of South China that reveals a single unradiogenic Os-isotope shift (from ~0.6 to 0.3) after the end Permian mass extinction event interval, which is interpreted to be related to volcanic activity. Above the unradiogenic excursion, a radiogenic shift to ~1.1 is detected across the Permian–Triassic boundary at Niushan that is correlative to the radiogenic Osi shift observed in the Meishan section. This increase in Os-isotope values is taken to reflect enhanced continental weathering. Both the unradiogenic and radiogenic excursions in the deep-water Niushan section are smaller in magnitude compared with the Os isotope profiles from more shallow-water sections of Meishan and Opal Creek. Our data suggest investigations of multiple sections across a variety of depositional environments may yield a more comprehensive understanding of the scale of the global perturbations related to volcanism and continental weathering intensity of the Permian–Triassic boundary interval.