Ben Creisler
A new paper:
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Carbon outgassing from Large Igneous Provinces has been invoked as a mechanism to drive major climate shifts throughout Earthâs history. However, the lack of direct constraints on evolving carbon release from magmas in these provinces represents a major challenge for understanding the relationship between magmatism and environmental change. This paper presents constraints on CO2 contents of early Deccan Traps lavas based on studies of olivine-hosted melt inclusions. We use these data to evaluate links between early Deccan carbon outgassing and an episode of pronounced warming just prior to the end-Cretaceous mass extinction. By accounting for evolving CO2 budgets and degassing from intrusive magmas, this work quantitatively relates magma emplacement, outgassing, and observed changes in paleoclimate.
Abstract
A 2 to 4 ÂC warming episode, known as the Latest Maastrichtian warming event (LMWE), preceded the CretaceousâPaleogene boundary (KPB) mass extinction at 66.05 Â 0.08 Ma and has been linked with the onset of voluminous Deccan Traps volcanism. Here, we use direct measurements of melt-inclusion CO2 concentrations and trace-element proxies for CO2 to test the hypothesis that early Deccan magmatism triggered this warming interval. We report CO2 concentrations from NanoSIMS and Raman spectroscopic analyses of melt-inclusion glass and vapor bubbles hosted in magnesian olivines from pre-KPB Deccan primitive basalts. Reconstructed melt-inclusion CO2 concentrations range up to 0.23 to 1.2 wt% CO2 for lavas from the Saurashtra Peninsula and the Thakurvadi Formation in the Western Ghats region. Trace-element proxies for CO2 concentration (Ba and Nb) yield estimates of initial melt concentrations of 0.4 to 1.3 wt% CO2 prior to degassing. Our data imply carbon saturation and degassing of Deccan magmas initiated at high pressures near the Moho or in the lower crust. Furthermore, we find that the earliest Deccan magmas were more CO2 rich, which we hypothesize facilitated more efficient flushing and outgassing from intrusive magmas. Based on carbon cycle modeling and estimates of preserved lava volumes for pre-KPB lavas, we find that volcanic CO2 outgassing alone remains insufficient to account for the magnitude of the observed latest Maastrichtian warming. However, accounting for intrusive outgassing can reconcile early carbon-rich Deccan Traps outgassing with observed changes in climate and atmospheric pCO2.
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News:
Scientists zero in on the role of volcanoes in the demise of dinosaurs
https://phys.org/news/2021-03-scientists-role-volcanoes-demise-dinosaurs.html"Their data show that CO2 outgassing from Deccan Traps magmas can explain a warming of Earth's global temperatures by roughly 3 degrees Celsius during the early phases of Deccan volcanism, but that there was not nearly that much warming by the time we reached the mass extinction event, supporting the idea that later Deccan magmas were not releasing as much CO2. These new insights disfavor the theory that volcanic CO2 was a major driver of the most recent mass extinction."