江汉盆地SKD1深钻记录的古新世——始新世极热事件时期的古气候

Paleoclimate during the Paleocene–Eocene Extreme Thermal Event Recorded by the Deep Drill Core SKD1 in the Jianghan Basin

古新世—始新世极热事件(PETM,~56 Ma)是发生古新世与始新世界线附近的一次快速增温事件,研究PETM事件的气候变化及驱动机制对应对全球变暖对气候和生态系统带来的影响至关重要。然而目前PETM记录较少且其气候效应仍存在很大争议。本文基于江汉盆地SKD1钻孔材料,利用湖泊自生碳酸盐矿物及其氧同位素组成,并结合岩芯岩性特征,分析了钻孔碳酸盐氧同位素(δ^(18)O_(碳酸盐))的指示意义,探讨了PETM期间江汉盆地的古气候,结果清晰地记录了PETM事件期间江汉盆地降水量显著增加、气候变湿的特征。PETM事件之前(pre-PETM)δ^(18)O_(碳酸盐)值较高,碳酸盐矿物以白云石为主,指示了江汉盆地年均降水量较少,气候非常干旱;PETM期间δ^(8)O_(碳酸盐)值显著负偏,主要沉积方解石,指示了降水量显著增加,气候相对湿润。PETM事件之后(post-PETM)δ^(18)O_(碳酸盐)值升高,白云石含量增加,且开始沉积厚层蒸发盐,说明气候再次变干。未来全球快速变暖背景下,副热带至中纬度地区可能普遍存在降水量显著增多的现象。

The Paleocene-Eocene thermal extreme event (PETM, ~56 Ma) was a transient episode of global warming near the Paleocene-Eocene boundary. The study of the climate change and driving mechanism of the Paleocene-Eocene thermal extreme event (PETM) is very important for dealing with the impact of global warming on climate and ecosystem. However, the current PETM records are few and its climate effects are still very controversial. Here, based on the materials of the SKD1 core in the Jianghan Basin, we analyzed the indication significance of the carbonate oxygen isotope (δ^(18)O_(carbonate)) in the core and further discussed the paleoclimate in the Jianghan Basin during the PETM, using lake authigenic carbonates and their isotopic compositions, combined with lithology characteristics. The results clearly show a significant increase in precipitation (P) in the Jianghan Basin during the PETM event. Before the PETM event (pre-PETM), the δ^(18)O_(carbonate) values were relatively high, and the carbonate minerals are mainly dolomite, with anhydrite being widely distributed, indicating a low mean annual precipitation in the Jianghan Basin. During the PETM event, δ^(18)O_(carbonate) values show a large negative excursion and calcite is the main deposit, which indicates a significant increase in precipitation and a relatively humid climate. After the PETM event (post-PETM), the increase in both the δ^(18)O_(carbonate) values and the dolomite content, along with the deposition of thick layers of anhydrite, glauberite, and halite indicate that the climate became extremely arid again. As a result of rapid global warming in the future, there may be a significant increase in precipitation in subtropical to mid-latitude regions.