黑龙江科技大学Li Yuanji和张强报道了东北抚顺盆地始新世古环境的定量地球化学重建。相关论文于2024年2月1日发表在《地球化学学报》杂志上。

研究人员以位于北半球中纬度地区的抚顺盆地、古近系(LFD-1井)古城子组、吉军屯组和西楼田组为研究对象，研究进行了精细的无机地球化学分析。结果表明，抚顺盆地始新统古城子组(54.51-47.8Ma)和吉军屯组(47.8-41.2 Ma)是在湿润气候下沉积的。西楼田组下部(41.2-40.1 Ma)和上部(40.1-37.8 Ma)分别表现为半干旱和半湿润—半干旱气候，这与有机碳同位素反映的古气候信息非常相似。始新世极热时期2 (ETM2，约53.7 Ma)、始新世早期气候最佳期(EECO，约 53.1-46.5 Ma)、始新世极热时期3 (ETM3，约52.8 Ma)和始新世中期气候最佳期(MECO，约40.7-40.1 Ma)显著增强了这些时期的化学风化作用。

pCO₂浓度的快速增加导致温度、降水和地表径流的增加，表现出强烈的化学风化作用。研究使用无钾腐蚀指数(CIA-K)、CaO/Al₂O₃和(Na₂O + K₂O)/Al₂O₃等参数估算年平均温度(MATa)和年平均降水量(MAPa、MAPb和MAPc)等参数。将MAPa、MAPb和MAPc与MAP估算的花粉数据进行比较，发现MAPa和MAPb在高降水期(降水>1000 mm，古城子组)对气候更为敏感，恢复的平均降水量与MAP相似。相比之下，MAPc在低降水期(降水<1000mm，吉军屯组和西楼田组)对气候更为敏感，精度更高。

为充分考虑可溶性无机盐Ca²⁺和Na⁺的影响，研究人员构建了CIA-K和CaO/Al₂O₃与CIA、CIA-K和CaO/Al₂O₃与MAP的多元线性方程，即MAPd和MAPe。结果表明，MAPe具有最高的性能，可以有效地用于估算东北亚洲古降水量的变化。

据悉，古温度和古降水关键参数的定量估算是古气候重建的关键。现代沉积物地球化学资料与气候数据资料具有高度的一致性，它们之间的关系可为古气候的定量重建提供重要参考。

附：英文原文

Title: Quantitative geochemical reconstruction of Eocene paleoenvironment in Fushun Basin, northeast China

Author: Li, Yuanji, Sun, Pingchang, Zhang, Qiang, Wang, Junxian

Issue&Volume: 2024-02-01

Abstract: The quantitative estimation of key parameters of paleotemperature and paleoprecipitation is crucial for paleoclimate reconstruction. Geochemical data from modern sediments are highly consistent with climate data, and their relationship can provide an important reference for the quantitative reconstruction of the paleoclimate. In this study, detailed inorganic geochemical analysis was carried out using high-precision sampling of the Paleogene (LFD-1 well) Guchengzi, Jijuntun and Xiloutian Formations in the Fushun Basin located in the mid-latitudes of the Northern Hemisphere. The Eocene Guchengzi Formation (54.51–47.8 Ma) and Jijuntun Formation (47.8–41.2 Ma) in the Fushun Basin were found to have been deposited under a humid climate. The lower (41.2–40.1 Ma) and upper (40.1–37.8 Ma) parts of the Xiloutian Formation were characterized by semiarid and semihumid–semiarid climates, respectively, which is very similar to the paleoclimatic information reflected by organic carbon isotopes. The Eocene Thermal Maximum 2 (ETM2,~53.7 Ma), Early Eocene Climatic Optimum (EECO,~53.1–46.5 Ma, Eocene Thermal Maximum 3 (ETM 3,~52.8 Ma), and Middle Eocene Climatic Optimum (MECO,~40.7–40.1 Ma) events significantly enhanced chemical weathering during these periods. The rapid increase in pCO₂ concentration leads to an increase in temperature, precipitation, and surface runoff, exhibiting strong chemical weathering. The mean annual temperature (MATa) and mean annual precipitation (MAPa, MAPb, and MAPc) were estimated using parameters, such as the corrosion index without potassium (CIA-K), CaO/Al₂O₃, and (Na₂O+K₂O)/Al₂O₃. Comparing MAPa, MAPb, and MAPc with the MAP estimated using pollen data, MAPa and MAPb were found to be more sensitive to the climate during high precipitation periods (precipitation>1000 mm, Guchengzi Formation), and the recovered average precipitation was similar to MAP. In contrast, MAPc was more sensitive to the climate during low precipitation periods (precipitation<1000 mm, Jijuntun, and Xiloutian Formations), with higher accuracy. To fully consider the influence of soluble inorganic salts Ca²⁺ and Na⁺, multivariate linear equations of CIA-K and CaO/Al₂O₃ with CIA, and CIA-K and CaO/Al₂O₃ with MAP were constructed, namely MAPd and MAPe. The results show that MAPe has the highest performance and can be effectively used to estimate the change of paleoprecipitation in Northeast Asia.

DOI: 10.1007/s11631-024-00674-6

Source: https://link.springer.com/article/10.1007/s11631-024-00674-6