T15 Understanding the Links between Life, Biogeochemical Cycles, and Environmental Feedbacks throughout the Mesozoic

Sunday, 22 September 2024
8:00 AM - 12:00 PM
207B

LARGE IGNEOUS PROVINCE CARBON EMISSIONS CONSTRAINED BY SEDIMENTARY MERCURY

Paper number: T15-8
Program: Technical Sessions
Time: 9:45 AM – 10:05 AM

Authors

Abstract

Large Igneous Province eruptions and their significant carbon emissions often coincide with, and are hypothesized to have driven, severe environmental perturbations in the geological past. However, the vast scale of large igneous provinces and uncertainties in magmatic volatile contents and radioisotopic dates limit our ability to resolve gas emissions in detail over time. Here, we employ high-resolution (~5–200 kyr) sedimentary mercury data from the Llanbedr (Mochras Farm) borehole, Wales, along with a Hg box model inversion framework to derive quantitative large igneous province degassing estimates over a 20-million-year-long Early Jurassic interval (195–175 million years ago). We find that intervals of relatively elevated sedimentary mercury coincide with episodes of carbon-cycle change, including the Toarcian Oceanic Anoxic Event (183–182 million years ago).

We then use excess mercury loading to estimate Large Igneous Province-associated carbon emissions, revealing that multi-millennial episodes of activity plausibly drove recognized pCO2 and temperature increases. However, previous carbon-cycle model-based carbon emission scenarios (based only on the inversion of geochemical paleoenvironmental proxies such as carbon isotopes and temperature records) require faster and larger carbon inputs than our proposed emissions. Resolving this discrepancy may require climate–carbon–cycle feedbacks or co-emitted gases to significantly exacerbate the carbon-cycle response, processes potentially underestimated in current models. Our long and near-continuous record of Early Jurassic large igneous province activity demonstrates mercury’s potential as a tool to resolve past carbon fluxes. In this presentation, we will present preliminary work utilizing this same approach applied to mercury records from other large igneous provinces associated with environmental change (e.g., the Deccan and Siberian Traps) and evaluate whether the estimated large igneous province-associated gas fluxes are comparable to those expected based on other techniques such as carbon-cycle proxy inversions.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-404801

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