The Guadalupian-Lopingian boundary stratotype at Penglaitan, and the nearby Tieqiao section, near Laibin, South China, record a series of major environmental changes within the Jiangnan Basin during a Mid Permian biotic crisis. The sequence stratigraphic, petrographic and palaeontological record of these sections has been studied and the associated strontium isotopic fluctuations assayed. Mass extinction of fusulinid foraminifera is most clearly associated in time with onset of volcanism and a relative sea-level fall that saw the establishment of mid-ramp conditions (Laibin Limestone) in settings that were previously dominated by radiolarian mudstones. The regression also coincides with a low point of 87Sr/86Sr ratios. The lowstand deposits contain mafic scoriaceous grains that record pyroclastic volcanism probably centred in the Emeishan flood basalt province 800 km to the west of Laibin. Thus, unusually violent eruptions associated with flood basalts in this province may have contributed to the environmental stresses responsible for the extinction event. Subsequent environmental changes included transgression, spread of dysoxic waters, indicated by populations of small pyrite framboids, and a major negative C isotope excursion. All these phenomena have been previously related to the end-Guadalupian extinction but they in fact post-date the crisis because a post-extinction fauna of foraminifers are encountered at this time.
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