Calcium isotope constraints on the end-Permian mass extinction

Abstract

The end-Permian mass extinction horizon is marked by an abrupt shift in style of carbonate sedimentation and a negative excursion in the carbon isotope (δ 13 C) composition of carbonate minerals. Several extinction scenarios consistent with these observations have been put forward. Secular variation in the calcium isotope (δ 44∕40 Ca) composition of marine sediments provides a tool for distinguishing among these possibilities and thereby constraining the causes of mass extinction. Here we report δ 44∕40 Ca across the Permian-Triassic boundary from marine limestone in south China. The δ 44∕40 Ca exhibits a transient negative excursion of ∼0.3‰ over a few hundred thousand years or less, which we interpret to reflect a change in the global δ 44∕40 Ca composition of seawater. CO 2 -driven ocean acidification best explains the coincidence of the δ 44∕40 Ca excursion with negative excursions in the δ 13 C of carbonates and organic matter and the preferential extinction of heavily calcified marine animals. Calcium isotope constraints on carbon cycle calculations suggest that the average δ 13 C of CO 2 released was heavier than −28‰ and more likely near −15‰; these values indicate a source containing substantial amounts of mantle-or carbonatederived carbon. Collectively, the results point toward Siberian Trap volcanism as the trigger of mass extinction.

The Phanerozoic δ88/86Sr record of seawater: New constraints on past changes in oceanic carbonate fluxes

“…This short term acidification event is not visible in our long-term δ 88/86 Sr sw record, but we anticipate that a negative excursion in δ 88/86 Sr sw , similar to that observed for Ca isotopes (Hinojosa et al, 2012;Payne et al, 2010), might be observed in future high resolution studies across the P/T boundary. Therefore, the predicted long term seawater anoxia is not necessarily in contradiction to the occurrence of a short term ocean acidification event on the order of a few hundred thousand years (Payne and Clapham, 2012;Sobolev et al, 2011).…”

“…Carbonate burial and dissolution are believed to have been closely linked to changes in seawater chemistry induced by ocean anoxia and acidification (Knoll et al, 1996;Payne et al, 2010;Riebesell et al, 1993;Woods et al, 1999). Massive weathering and recrystallization of continental carbonate shelves during sea level low stands could also contribute an additional flux of Sr to the ocean (Krabbenhöft et al, 2010;Stoll and Schrag, 1998).…”

Latest Permian carbonate carbon isotope variability traces heterogeneous organic carbon accumulation and authigenic carbonate formation

“…An elevated oceanic carbonate inventory is a predicted aspect of an ocean without pelagic calcifiers, which only started proliferating during the Mesozoic and would effectively buffer short-term perturbations to P-Tr marine carbon isotopes (Kump and Arthur, 1999;Zeebe and Westbroek, 2003;Rampino and Caldeira, 2005;Ridgwell, 2005;Payne et al, 2010). This does not, however, exclude local departures from this dynamic equilibrium or depth-related isotope differences, such as those forced by the biological pump (Kump and Arthur, 1999;Rampino and Caldeira, 2005).…”

Adaptive strategies and environmental significance of lingulid brachiopods across the late Permian extinction

“…The recognition and effects of acidification on the upper Permian marine biota have been suggested using the pattern of taxonomical selectivity, geochemistry of Calcium isotopes, dissolution and mineralogical composition of carbonates (e.g., Payne et al, 2007;Payne et al, 2010;Clapham and Payne, 2011;Hinojosa et al, 2012), but direct evidences on the fossil record are lacking.…”