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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.

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.

The end-Cretaceous mass extinction resulted in the demise of the dinosaurs and many other plant and animal species, irrevocably changing Earth’s ecosystems. The environmental changes which influenced the mass extinction and recovery were most likely caused by a combination of the Chicxulub impact and Deccan Traps Large Igneous Province volcanism. The climate and ecological effects of the Deccan Traps remain ambiguous, due in part to a paucity of constraints on eruption rates and frequency. I have addressed this by using mercury concentration as an indicator of eruptions and combining these chemostratigraphic records with mercury box models to estimate eruptive rate and emissions rate of climate-altering gases. Additionally, the timing of the largest known Deccan eruptions, the Rajahmundry Traps, was unclear with respect to the extinction event. As the largest eruptions have been hypothesized to have the most significant climate impact, knowing the timing of these eruptions allows for direct comparison with climate records. Using a combination of geochronological techniques, I found that all three subaerially exposed Rajahmundry Traps lava flows erupted after the Cretaceous-Paleogene boundary. I then used scalings from the LOSCAR carbon cycle model along with paleoclimate records and found that these eruptions most likely did not cause multi-degree warming. However, they could have contributed to ongoing carbon cycle perturbations during the recovery interval. I then investigated the nature of these carbon cycle perturbations by creating a new high-resolution carbon isotope record from terrestrial organic material. I specifically addressed the discrepancy between terrestrial carbon isotope records, which have been interpreted as containing short (<10 ka) excursions, and marine records, which contain a much longer (∼ 1.5 Ma) excursion linked to decreased export productivity in the surface ocean. My new record shows that, contrary to previously thought, terrestrial

The end-Cretaceous mass extinction resulted in the demise of the dinosaurs and many other plant and animal species, irrevocably changing Earth’s ecosystems. The environmental changes which influenced the mass extinction and recovery were most likely caused by a combination of the Chicxulub impact and Deccan Traps Large Igneous Province volcanism. The climate and ecological effects of the Deccan Traps remain ambiguous, due in part to a paucity of constraints on eruption rates and frequency. I have addressed this by using mercury concentration as an indicator of eruptions and combining these chemostratigraphic records with mercury box models to estimate eruptive rate and emissions rate of climate-altering gases. Additionally, the timing of the largest known Deccan eruptions, the Rajahmundry Traps, was unclear with respect to the extinction event. As the largest eruptions have been hypothesized to have the most significant climate impact, knowing the timing of these eruptions allows for direct comparison with climate records. Using a combination of geochronological techniques, I found that all three subaerially exposed Rajahmundry Traps lava flows erupted after the Cretaceous-Paleogene boundary. I then used scalings from the LOSCAR carbon cycle model along with paleoclimate records and found that these eruptions most likely did not cause multi-degree warming. However, they could have contributed to ongoing carbon cycle perturbations during the recovery interval. I then investigated the nature of these carbon cycle perturbations by creating a new high-resolution carbon isotope record from terrestrial organic material. I specifically addressed the discrepancy between terrestrial carbon isotope records, which have been interpreted as containing short (<10 ka) excursions, and marine records, which contain a much longer (∼ 1.5 Ma) excursion linked to decreased export productivity in the surface ocean. My new record shows that, contrary to previously thought, terrestrial

Weathering profiles developed on basalt substrate contain information relevant to climate, atmospheric composition and evolution, nutrient release into the hydrosphere, and understanding Martian regolith. In this study, the chemical compositions of two profiles developed on Deccan Trap basalt are examined. One is sub-Recent and has only progressed to a moderate degree of alteration (Chhindwara profile), whereas the other is ancient (Paleocene) and the degree of alteration is extreme (Bidar laterite). In an attempt to better quantify the chemical changes during incipient to intermediate weathering of mafic substrates, a new index is proposed: the mafic index of alteration (MIA). Similar to the chemical index of alteration (CIA), the MIA quantifies the net loss of the mobile major elements (Ca, Mg, Na, K +/- Fe) relative to the immobile major elements (Al +/- Fe). The redox-dependent weathering behaviour of Fe is factored into two separate arrangements of the MIA that apply to oxidative [MIA((O))] or reduced [MIA((R))] weathering. The MIA can be visualised in a variety of ternary diagrams in the Al-Fe-Mg-Ca-Na-K system. To chemically quantify the stages of advanced to extreme weathering, at which the MIA and CIA are ineffective, the SiO2 to (Al2O3 + Fe2O3) mass ratio, based on the established Si-Al-Fe (SAF) 'laterite' ternary diagram, is used; we propose that this ratio be referred to as the 'index of lateritisation' (IOL). Major element chemical variations, as expressed by weathering indices, are used to relate the extent of weathering with the behaviour of trace elements (alkali, alkaline earth, rare earth, and Nb) in the profiles. During the early stages of basalt weathering, the mobile trace elements (Sr, Be, Li) are anti-correlated with the chemical weathering indices and thus released during these stages. By contrast, the monovalent elements (K, Rb, Cs, Tl), excluding Na and Li, appear to be associated with the pedogenetic clay minerals. Of these elements, those

The Deccan Trap basalts are the remnants of a massive series of lava flows that erupted at the K/T boundary and covered 1-2 million km2 of west-central India. This eruptive event is of global interest because of its possible link to the major mass extinction event, and there is much debate about the duration of this massive volcanic event. In contrast to isotopic or paleomagnetic dating methods, I explore an alternative approach to determine the lifecycle of the magma chambers that supplied the lavas, and extend the concept to obtain a tighter constraint on Deccan’s duration. My method relies on extracting time information from elemental and isotopic diffusion across zone boundary in an individual crystal. I determined elemental and Sr-isotopic variations across abnormally large (2-5 cm) plagioclase crystals from the Thalghat and Kashele “Giant Plagioclase Basalts” from the lowermost Jawhar and Igatpuri Formations respectively in the thickest Western Ghats section near Mumbai. I also obtained bulk rock major, trace and rare earth element chemistry of each lava flow from the two formations. Thalghat flows contain only 12% zoned crystals, with 87Sr/86Sr ratios of 0.7096 in the core and 0.7106 in the rim, separated by a sharp boundary. In contrast, all Kashele crystals have a wider range of 87Sr/86Sr values, with multiple zones. Geochemical modeling of the data suggests that the two types of crystals grew in distinct magmatic environments. Modeling intracrystalline diffusive equilibration between the core and rim of Thalghat crystals led me to obtain a crystal growth rate of 2.03x10-10 cm/s and a residence time of 780 years for the crystals in the magma chamber(s). Employing some assumptions based on field and geochronologic evidence, I extrapolated this residence time to the entire Western Ghats and obtained an estimate of 25,000 – 35,000 years for the duration of Western Ghats volcanism. This gave an eruptive rate of 30 – 40 km3/yr, which is much higher than any pres

A thick pile of felsic volcanics overlies eleven basic flows in Pavagadh. Mugearite seen as intrusive can be considered to be the last phase of the basic magmatic activity in Pavagadh....

A thick pile of felsic volcanics overlies eleven basic flows in Pavagadh. Mugearite seen as intrusive can be considered to be the last phase of the basic magmatic activity in Pavagadh....