Reconstruction of the early Eocene paleoclimate and paleoenvironment of the southeastern Neo-Tethys Ocean
Reconstruction of the early Eocene paleoclimate and paleoenvironment of the southeastern Neo-Tethys Ocean
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新特提斯洋东南部始新世早期古气候与古环境重建
DOI：
10.1016/j.gloplacha.2022.103875
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发表时间：
2022
影响因子：
3.9
通讯作者：
Cui, Ying
中科院分区：
文献类型：
--
作者：
Dong, Yixin;Convers, Liliana Calderón;Jiang, Shijun;Li, Xiaona;Zhu, Peng;Chen, Hongde;Cui, Ying
始新世早期被认为是新生代最温暖的时期，全球气温比今天高约 10°C。尽管始新世东南部新特提斯洋具有重要的构造意义，但很少有研究关注其古气候历史。在这里，我们报告了新的地球化学数据，揭示了中国青藏高原南部定日地区曲米巴剖面早始新世（约53.7至52.6 Ma）的古气候条件，这可能代表了新特提斯洋东南部最年轻的海洋地层。研究的库米巴地段由恩巴组和扎果组组成，其特征是粉砂质泥灰岩、泥岩和薄层岩屑砂岩。库米巴剖面的古气候和古环境历史是利用海洋碳酸盐的稳定碳和氧同位素（δ13C碳和δ18Ocarb）、主量、痕量和稀土元素重建的。库米巴断面至少记录了一次始新世早期高温事件（I1 或 I2；~53.6 Ma），这得到了 δ13Ccarbin 2 单元突然负偏移的支持。化学风化增强（例如，化学蚀变指数）进一步支持了这一点，这可归因于温度和降水的增加。 3号机组持续的负δ13C碳偏移可能是由火山活动释放13C贫碳造成的。火山输入可能增加了养分的可用性并促进了海洋初级生产力（例如，更高的磷、钡、镍和铜的富集因子）。此外，在此期间，如氧化还原敏感指标（例如 U 和 V 以及 Ce/Ce* 的较高富集因子）所示，流域可能经历了底层水缺氧（第 3 单元）。我们的研究结果支持始新世早期变暖引起的新特提斯洋东南部古环境条件的变化。
The early Eocene is thought to be the warmest period of the Cenozoic Era, with global temperatures ~10 °C higher than today. Few studies have focused on the paleoclimatic history of the early Eocene southeastern Neo-Tethys Ocean despite its tectonic significance. Here, we report new geochemical data that reveal the paleoclimate conditions of the early Eocene (~ 53.7 to 52.6 Ma) from the Qumiba section in the Tingri region of the southern Tibetan Plateau, China, which likely represents the youngest marine strata in the southeastern Neo-Tethys Ocean. The studied Qumiba section consists of the Enba and Zhaguo Formations characterized by silty marls, mudstones and thin layers of lithic sandstones. The paleoclimate and paleoenvironment history of the Qumiba section is reconstructed using stable carbon and oxygen isotopes of marine carbonates (δ13Ccarband δ18Ocarb), major, trace and rare earth elements. At least one early Eocene hyperthermal event (I1 or I2; ~53.6 Ma) has been recorded in the Qumiba section supported by abrupt negative excursions in δ13Ccarbin Unit 2. This is further supported by enhanced chemical weathering (e.g., chemical index of alteration), which can be attributed to increased temperature and precipitation. The continued negative δ13Ccarbexcursions in Unit 3 may have been caused by the release of13C-depleted carbon from volcanic activities. The volcanic inputs may have increased nutrient availability and promoted marine primary productivity (e.g., higher enrichment factors of P, Ba, Ni and Cu). Furthermore, the basin may have experienced bottom water anoxia as suggested by the redox-sensitive proxies (e.g., higher enrichment factors of U and V and Ce/Ce*) during this period (Unit 3). Our findings support warming-induced changes in paleoenvironmental conditions in the southeastern Neo-Tethys Ocean during the early Eocene.