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

Kemp, David B. and Selby, David and Izumi, Kentaro (2020) 'Direct coupling between carbon release and weathering during the Toarcian oceanic anoxic event.', Geology., 48 (10). pp. 976-980.

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.

Item Type:Article
Full text:Publisher-imposed embargo
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Available under License - Creative Commons Attribution.
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1130/G47509.1
Publisher statement:© 2020 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license.
Date accepted:08 May 2020
Date deposited:04 June 2020
Date of first online publication:25 June 2020
Date first made open access:26 June 2020

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