Global perturbation of the marine calcium cycle during the Permian-Triassic transition

Abstract

A negative shift in the calcium isotopic composition of marine carbonate rocks spanning the end-Permian extinction horizon in South China has been used to argue for an ocean acidification event coincident with mass extinction. This interpretation has proven controversial, both because the excursion has not been demonstrated across multiple, widely separated localities, and because modeling results of coupled carbon and calcium isotope records illustrate that calcium cycle imbalances alone cannot account for the full magnitude of the isotope excursion. Here, we further test potential controls on the Permian-Triassic calcium isotope record by measuring calcium isotope ratios from shallow-marine carbonate successions spanning the Permian-Triassic boundary in Turkey, Italy, and Oman. All measured sections display negative shifts in δ 44/40 Ca of up to 0.6‰. Consistency in the direction, magnitude, and timing of the calcium isotope excursion across these widely separated localities implies a primary and global δ 44/40 Ca signature. Based on the results of a coupled box model of the geological carbon and calcium cycles, we interpret the excursion to reflect a series of consequences arising from volcanic CO 2 release, including a temporary decrease in seawater δ 44/40 Ca due to short-lived ocean acidification and a more protracted increase in calcium isotope fractionation associated with a shift toward more primary aragonite in the sediment and, potentially, subsequently elevated carbonate saturation states caused by the persistence of elevated CO 2 delivery from volcanism. Locally, changing balances between aragonite and calcite production are sufficient to account for the calcium isotope excursions, but this effect alone does not explain the globally observed negative excursion in the δ 13 C values of carbonate sediments and organic matter as well. Only a carbon release event and related geochemical consequences are consistent both with calcium and carbon isotope data. The carbon release scenario can also account for oxygen isotope evidence for dramatic and protracted global warming as well as paleontological evidence for the preferential extinction of marine animals most susceptible to acidification, warming, and anoxia.

Permian Large Igneous Provinces and Their Paleoenvironmental Effects

“…A similar trend is observed in the calcium isotopic compositions of conodont apatite from the Meishan GSSP (Hinojosa et al, 2012). This pattern was also found in Turkey, Italy, and Oman in terms of the direction, magnitude, and timing of the calcium isotope excursion (Lau et al, 2017;Silva-Tamayo et al, 2018). Based on updated modeling experiments, Silva-Tamayo et al (2018) concluded that the observed parallel negative excursions in carbonate δ 44/40 Ca and δ 13 C are best explained by a series of consequences arising from Siberian Traps volcanic CO 2 release.…”

“…This pattern was also found in Turkey, Italy, and Oman in terms of the direction, magnitude, and timing of the calcium isotope excursion (Lau et al, 2017;Silva-Tamayo et al, 2018). Based on updated modeling experiments, Silva-Tamayo et al (2018) concluded that the observed parallel negative excursions in carbonate δ 44/40 Ca and δ 13 C are best explained by a series of consequences arising from Siberian Traps volcanic CO 2 release. These included a temporary decrease in seawater δ 44/40 Ca due to short-lived ocean acidification and a more protracted increase in calcium isotope fractionation associated with a shift toward more primary aragonite in the sediment and, potentially, subsequently elevated carbon saturation states caused by the persistence of elevated CO 2 delivery from volcanism.…”

“…According to Clarkson et al (2015), the δ 11 B values (i.e., ocean pH) remained stable across the period of NCIE, and began to decrease rapidly, with its minimum coincident with the second pulse of mass extinction (EP2). The asynchronous behavior of δ 13 C and δ 11 B in the UAE remains enigmatic (Silva-Tamayo et al, 2018), because if the globally recognized NCIE at EP1 were interpreted as a response to the CO 2 transferred from a high pCO 2 atmosphere into the surface ocean waters, coherent patterns in δ 13 C and δ 11 B would be expected.…”

Early Triassic benthic invertebrates from the Great Bank of Guizhou, South China: systematic palaeontology and palaeobiology

“…; Silva‐Tamayo et al . ). Another notable feature is the dominance of aragonite taxa in the benthic communities, with the exception of the Huangzhishan Formation fauna, suggesting a high pH of benthic ecosystems in the extinction aftermath globally.…”

Changhsingian brachiopod communities along a marine depth gradient in South China and their ecological significance in the end-Permian mass extinction

“…The end‐Permian mass extinction (EPME), one of the most remarkable biological events in the Phanerozoic Eon, considerably altered evolutionary processes in marine ecosystems and marked the transition from Palaeozoic‐type marine ecosystems to the ‘modern’ Mesozoic and Cenozoic‐type marine ecosystems (Sepkoski 1981; Chen & Benton 2012; Payne et al 2014; Stanley 2016; Brayard et al 2017). It is argued that ecosystem collapse (or extinction) was triggered by synergistic stresses, such as anoxia (Wignall & Twitchett 1996; Isozaki 1997; Winguth & Winguth 2012; Huang et al 2017b), global warming (Joachimski et al 2012; Sun et al 2012; Garbelli et al 2016; Brand et al 2016) and possible ocean acidification (Payne et al 2007, 2010; Hinojosa et al 2012; Kershaw et al 2012; Clarkson et al 2015; Silva‐Tamayo et al 2018). Marine ecosystems involve biotic and abiotic components, which need to be considered together when discussing extinction patterns and processes.…”