水銀の上昇:古代火山の環境影響に新たな光(Mercury rising: Study sheds new light on ancient volcanoes’ environmental impact)

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2024-02-29 ペンシルベニア州立大学(PennState)

地球の歴史での大規模な火山活動は、大気中に大量の二酸化炭素を放出し、環境の大きな変化や大量絶滅と関連しています。ペンシルベニア州立大学とオックスフォード大学をリードする国際チームは、古代の火山活動による岩石中の残留水銀量を推定する新しい手法を開発しました。この手法により、大規模な火山地帯からの二酸化炭素排出量を推定することができ、地球システムのフィードバックプロセスについての理解を向上させる可能性があります。

<関連情報>

ジュラ紀初期の大規模火成岩地域の炭素排出が堆積水銀によって制約される Early Jurassic large igneous province carbon emissions constrained by sedimentary mercury

Isabel M. Fendley,Joost Frieling,Tamsin A. Mather,Micha Ruhl,Stephen P. Hesselbo & Hugh C. Jenkyns
Nature Geoscience  Published:26 February 2024
DOI:https://doi.org/10.1038/s41561-024-01378-5

figure 1

Abstract

Large igneous province eruptions and their 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, to derive quantitative large igneous province degassing estimates over a 20-million-year-long Early Jurassic interval (195–175 million years ago). 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 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 require faster and larger carbon inputs than our proposed emissions. Resolving this discrepancy may require climate–carbon-cycle feedbacks or co-emitted gases to substantially 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.

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1702地球物理及び地球化学
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