Multiple S-isotope constraints on environmental changes during the Serpukhovian mass extinction

Abstract

The Serpukhovian (mid-Carboniferous) mass extinction has been ranked fifth among the major Phanerozoic biodiversity crises, based on its ecological impact. Global cooling and environmental deterioration driven by the late Paleozoic ice age (LPIA) have been invoked as potential drivers of the Serpukhovian extinction; however, the underlying killing mechanisms remain poorly understood. Here we present multiple S-isotopic records (δ34S and Δ33S) of pyrites from the Naqing section in South China, a potential Global Stratotype Section and Point (GSSP) for the base of the Serpukhovian Stage. Our results reveal the distinctive S-isotopic characteristics of negative Δ33S and δ34S values, implying changes in redox conditions in the mid-Carboniferous oceans. The mixing signal of S-isotopic compositions suggests the encroachment of deep anoxic water onto the shallow shelves. The recurrence of the S-isotope mixing signal during the Serpukhovian extinction suggests the instability of oceanic redox conditions and that the episodic incursion of toxic anoxic water may have contributed to the Serpukhovian extinction.