Direct coupling between carbon release and weathering during the Toarcian oceanic anoxic event

Kemp, David B.; Selby, David; Izumi, Kentaro

Abstract

Silicate weathering represents a major feedback mechanism in the Earth’s climate system, helping to stabilize atmospheric CO2 levels and temperature on million-year time scales. On shorter time scales of greater relevance to understanding the fate of anthropogenic CO2, the efficacy and responsiveness of weathering is less clear. Here, we present high-resolution osmium-isotope data that reflect global chemical weathering from a stratigraphically thick record of the early Toarcian oceanic anoxic event (T-OAE; ca. 182 Ma). A pronounced decrease in the carbon-isotope composition of exogenic carbon reservoirs during this event has been linked to the large-scale release of 12C-enriched carbon. Our data indicate that the flux of radiogenic osmium to the oceans increased in lockstep with the decrease in carbon-isotope values, demonstrating a geologically synchronous coupling between massive carbon release and enhanced global continental crust weathering. We show that abrupt shifts in carbon isotopes, previously interpreted as millennial-scale methane hydrate melting or terrestrial carbon-release events, are coeval with rapid increases in weathering. Global weathering may have increased by >40% across each of these intervals of rapid carbon injection. Our results help to reconcile previous estimates of weathering change during the T-OAE, and support the view that, overall, global weathering rates may have increased six-fold through the entire event.

Citation

Kemp, D. B., Selby, D., & Izumi, K. (2020). Direct coupling between carbon release and weathering during the Toarcian oceanic anoxic event. Geology, 48(10), 976-980. https://doi.org/10.1130/g47509.1

• Journal Article Type: Article
• Acceptance Date: May 8, 2020
• Online Publication Date: Jun 25, 2020
• Publication Date: 2020
• Deposit Date: Jun 4, 2020
• Publicly Available Date: Jun 26, 2020
• Journal: Geology
• Print ISSN: 0091-7613
• Electronic ISSN: 1943-2682
• Publisher: Geological Society of America
• Peer Reviewed: Peer Reviewed
• Volume: 48
• Issue: 10
• Pages: 976-980
• DOI: https://doi.org/10.1130/g47509.1
• Public URL: https://durham-repository.worktribe.com/output/1300772