Narrowing the gap between early Deccan Traps CO (sub 2) outgassing and pre-KPB global climate

摘要: A 2-4 degrees C warming episode that preceded the Cretaceous Paleogene boundary (KPB) mass extinction has been linked with the opening phases of Deccan Traps volcanism. Here, we use measurements of trace elements and CO (sub 2) in melt inclusions to test the hypothesis that early Deccan magmatism triggered the Late Cretaceous warming interval. Using glassy, bubble-bearing melt inclusions hosted in magnesian olivines from early picritic basalts, we report CO (sub 2) concentrations from NanoSIMS analysis of glass and Raman spectroscopy on vapor bubbles. Trace element proxies for CO (sub 2), such as Ba and Nb, yield estimates of initial CO (sub 2) prior to degassing. In conjunction with our melt inclusion data, trace element ratios support a range of CO (sub 2) concentrations to higher values than prior estimates, with strong degassing beginning at the Moho or in the lower crust. However, our revised estimates of magmatic carbon inventories narrow but do not eliminate the gap between volcanic carbon outgassing and the carbon emissions. Based on scalings from carbon cycle modeling and estimates of preserved lava volumes from the Kalsubai and Lonavala subgroups of approximately 120,000 km (super 3), we find that volcanic CO (sub 2) outgassing alone remains insufficient to account for the magnitude of observed Late Cretaceous warming. Possible explanations for this' missing'carbon include:(1) cryptic degassing,(2) degassing of sedimentary rocks, or (3) magma volumes not included in estimates based on preserved, onshore lavas. Unlike other Large Igneous Provinces, Deccan country rocks are not known to host …