Reconciling early Deccan Traps CO ₂ outgassing and pre-KPB global climate

Abstract

A 2 to 4 °C warming episode, known as the Latest Maastrichtian warming event (LMWE), preceded the Cretaceous–Paleogene boundary (KPB) mass extinction at 66.05 ± 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.

Crustal SiO2 Content of the Emeishan Large Igneous Province and its Implications for Magma Volume and Plumbing System

“…The mass balance calculation for the major elements gave a cumulate (intrusive/extrusive) ratio of ∼0.65 for the Emeishan LIP (Cox, 1993;. In this sense, ∼1.45 × 10 6 km 3 volume of the erupted magmas, a little larger than the extrusive volume of the Deccan Traps (0.6-1.3 × 10 6 km 3 ) (Nava et al, 2021), and ∼2.39 × 10 6 km 3 volume of the total emplaced magmas can be estimated for the extremely mafic area (Figure 6), which is comparable to the volume of typical LIPs generated by mantle plumes (Coffin & Eldholm, 1994). So far, we have effectively estimated the intrusive and extrusive volumes of the plume-generated magmas in the Emeishan LIP.…”

“…The red dashed line depicts an area of ∼3 × 10 4 km 2 featured by the extremely mafic composition (∼55.7 wt% SiO 2 ). concentrations can be reconstructed (e.g., Nava et al, 2021), it can be expect to understand the outgassing of plume-related volcanism more quantitatively which has been invoked as the critical mechanism of these environmental changes (Shen et al, 2011;Wignall et al, 2009).…”

Clumped-isotope-derived climate trends leading up to the end-Cretaceous mass extinction in northwest Europe

“…This warming event (termed the Late Maastrichtian Warm Event or LMWE; Woelders et al, 2018) has been observed in multiple locations and has been dated to approximately coincide with the onset of major Deccan volcanism (66.413 ± 0.067 Ma; Sprain et al, 2019). Anomalous mercury concentrations in sediments (e.g., Font et al, 2016;Sial et al, 2016;Percival et al, 2018;Zhao et al, 2021) and fossil shells (Meyer et al, 2019) link the warming to a volcanic source, and modeling of the climate impacts of hypothesized volcanic CO2 and Hg emissions result in warming consistent with observations (Tobin et al, 2017;Fendley et al, 2019;Nava et al, 2021). Prior to the LMWE, global climate was in a "cool greenhouse" state (Scotese, 2021), with a small ice cap possible in Antarctica as indicated by models (Miller et al, 2005;Ladant and Donnadieu, 2016), sea-ice-indicating dinoflagellate cysts (Bowman et al, 2013), and coastal Antarctic temperatures near the freezing point (Petersen et al, 2016a).…”

“…Multiple paleoclimate records document a late Maastrichtian warming event (LMWE) (e.g., Stott and Kennett, 1990;Li and Keller, 1998;Petersen et al, 2016a;Woelders et al, 2017;Woelders et al, 2018;Barnet et al, 2019;Gao et al, 2021;Nava et al, 2021), beginning gradually at 66.4 Ma with more rapid warming at 66.3 Ma (Hull et al, 2020). This timing of the LMWE aligns it with the onset of LIP volcanism in the Indian subcontinent, based on 40 Ar-39 Ar ages for the oldest basalts of the Deccan Traps (66.413 ± 0.067 Ma; Sprain et al, 2019) and shifts in marine osmium isotope ratios towards mantle values beginning ~400 kyr prior to the KPB (Ravizza and Peucker-Ehrenbrink, 2003;Hull et al, 2020).…”

Supplemental Material: Contribution of orbital forcing and Deccan volcanism to global climatic and biotic changes across the Cretaceous-Paleogene boundary at Zumaia, Spain

“…3B). Recent carbon and CO 2 estimations from Deccan outgassing suggest that this phase could have outgassed more CO 2 than the main eruptive phases of the Wai subgroup, but this would still have been insufficient to explain the amplitude of LMWE warming (Hernandez Nava et al, 2021). However, both warming (Hull et al, 2020; Fig.…”