Resolving the pre-erosive extent and volume of the Deccan Large Igneous Province with low-temperature thermochronology: Implications for Earth’s long-term carbon cycle

• Applicant: Dr. Cody Colleps
• Subject Area: Geology ; Mineralogy, Petrology and Geochemistry
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 538063624

The voluminous modern preservation of the Deccan large igneous province (LIP) of west-central India archives one of the most extraordinary volcanic events in Earth’s history, and its pre-erosive extent was even more expansive. Constraining the pre-erosive extent and volume of the Deccan LIP is imperative to understand the impact that Deccan volcanism had on driving global-scale climatic shifts since the end of the Late Cretaceous. First, it has been proposed that initial Deccan eruptions drove an abrupt increase in atmospheric CO2 responsible for the Late Maastrichtian warming event. Following their emplacement, the weathering of the Deccan basalts has been proposed as an efficient mechanism to drawdown atmospheric CO¬2 via silicate weathering reactions, which may have facilitated long-term cooling during the Cenozoic. Whereas these Deccan-related mechanisms are known to directly influence the long-term carbon cycle, the magnitude of this influence remains poorly understood and intensely debated. One major source of this uncertainty is the lack of direct constraints on the pre-erosive extent and volume of the Deccan LIP—significant volumes of Deccan basalts have eroded away since their emplacement, and present-day preservations only permit minimal direct estimates for eruptive volumes. This proposed research intends to utilize a novel, state-of-the-art low-temperature thermochronometric methodology to (1) map out the pre-erosive areal extent of the Deccan LIP, and (2) quantify the volume of Deccan basalts eroded away since their emplacement. A recent proof-of-concept study by Colleps et al. (2021) reveals that apatite (U-Th)/He (AHe) thermochronometric data can directly constrain where Deccan basalts were once emplaced, but have since eroded away. To expand on this previous study, a proposed comprehensive low-temperature thermochronometric dataset—including AHe dates, high-resolution 4He/3He profiles, and apatite Fission Track dates—will be collected from rocks surrounding the margins of modern Deccan LIP exposures. Not only will these data establish new minimal areal constraints for the original Deccan LIP extent, they will be utilized to extract exceptionally high-resolution thermal history models from which (1) erosive volumes may be better estimated, and (2) spatial-temporal patterns in Deccan basalt erosion may be established. Newly established estimates for the pre-erosive Deccan extent and volume will be incorporated into sophisticated long-term carbon cycling models, permitting adequate assessment of the impact the Deccan LIP had on Earth’s climate in the detail required to resolve existing ambiguities.

• DFG Programme: Research Grants