成都理工大学马义权团队近日取得一项新成果。他们报道了中始新世气候最佳期火山和轨道所致的碳释放。这一研究成果发表在2024年7月30日出版的国际学术期刊《地质学》上。

据介绍，始新世中期气候最佳期(MECO)的驱动因素仍然是一个谜。研究人员报道了中国东部渤海湾盆地的高分辨率陆地MECO记录。记录显示，MECO期间显示出汞的阶段性富集和独特的火山成因Δ¹⁹⁹Hg特征，而在MECO暖峰期间，显示出突发性化学风化增强和δ¹³C_org负偏移(CIE)为特征。

一个高分辨率的年龄模型将MECO的年龄限制在ca. 40.59-40.18 Ma，开始于第一个约320k.y.峰值温暖期，CIE开始于40.27 Ma，对应于405k.y.和100k.y.的偏心率最大值，并持续了约90k.y.，提示始新世早期的热液活动。

研究结果表明，幕式火山活动导致大气中二氧化碳分压的逐渐上升和MECO发作的持续时间较长。40.27Ma的轨道作用力，加上二氧化碳作用力，导致了峰值温度和正的碳循环反馈。区域风化的增加与全球大陆风化减弱的证据不一致，表明MECO变暖的风化响应具有强烈的空间异质性。

附：英文原文

Title: Volcanic and orbitally forced carbon release during the Middle Eocene Climatic Optimum

Author: Yiquan Ma, Majie Fan, Chen Zhang, Stephen E. Grasby, Runsheng Yin, Yangbo Lu, Bolin Zhang, Xin Jin, Chao Ma, Yongchao Lu, Appy Sluijs

Issue&Volume: 2024-07-30

Abstract: The drivers of the Middle Eocene Climatic Optimum (MECO) remain enigmatic. Here we report a high-resolution terrestrial MECO record from the Bohai Bay Basin, eastern China. The record shows episodic Hg enrichments and a volcanogenic Δ¹⁹⁹Hg signature during the MECO, and an abrupt chemical weathering enhancement and negative δ¹³C_org excursion (CIE) during the MECO peak warmth. A high-resolution age model constrains the MECO to ca. 40.59-40.18 Ma with the onset in the first ～320 k.y. Peak warmth and the CIE initiated at 40.27 Ma, corresponding to 405 k.y. and 100 k.y. eccentricity maxima, and lasted for ～90 k.y., reminiscent of the early Eocene hyperthermals. Our findings suggest that episodic volcanism contributed to gradual atmospheric pCO₂ rise, leading to the long duration of the MECO onset. Orbital forcing at 40.27 Ma, on top of CO₂ forcing, caused the peak warmth and a positive carbon cycle feedback. The regional increase in weathering is inconsistent with evidence for weakened global continental weathering, suggesting strong spatial heterogeneity in the weathering response to MECO warming.

DOI: 10.1130/G52435.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G52435.1/645998/Volcanic-and-orbitally-forced-carbon-releaseredirectedFrom=fulltext