| 摘要: |
| 伦坡拉盆地位于青藏高原腹地，是感应高原隆升过程和环境变化效应的核心地带，不仅能够记录大陆碰撞过程、岩石圈和地壳变形历史，也是获取高原腹地地形地貌演化环境和气候变迁信息最理想的场所。为揭示伦坡拉盆地晚始新世－早渐新世古气候信息，选取盆地西南缘382道班剖面牛堡组二段细粒沉积物样品，通过主、微量元素分析，采用元素组合（C值）、Rb/Sr、Sr/Cu和Sr/Ba等比值以及化学蚀变指数（CIA）、元素风化指数（α）、Ln(Al2O3/Na2O)等多种化学风化指数研究了源区风化作用强度，讨论了古气候演化特征。结果表明：伦坡拉盆地牛堡组二段沉积期古气候整体较为干旱，但在始新世－渐新世之交存在一个明显的降温事件，该降温事件并不局限于伦坡拉盆地，在青藏高原及周缘其它地区也被广泛记录，是新生代始新世－渐新世全球降温事件的陆内响应。 |
| 关键词: 伦坡拉盆地 元素地球化学 风化指数 始新世－渐新世 古气候 |
| DOI：10.19826/j.cnki.1009-3850.2023.02023 |
| 附件 |
| 投稿时间：2022-07-24修订日期：2022-11-25 |
| 基金项目:国家自然科学基金“青藏高原新生代湖相碳酸盐碳氧同位素特征与古环境意义”（41972115） |
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| Late Eocene to early Oligocene geochemical characteristics and paleoclimatic significance of the second member of Niubao Formation in the Lunpola Basin，Tibet |
| BAO Wancheng, XIA Guoqing, LU Chang, FAN Qiushuang, WU Jinxuan, SHI Zhu |
(1. State Key Laboratory of oil and gas reservoir geology and development engineering, Chengdu University of technology, Chengdu 610059, China;
2. Institute of sedimentary geology, Chengdu University of technology, Chengdu 610059, China;
3. NO.280 Research Institute of Nuclear Industry, Deyang 618300, China;
4. NO.2 Oil Production Plant, Northwest Oilfield Company, SINOPEC, Bayingol 841600, China) |
| Abstract: |
| The Lunpola Basin, which is located in the hinterlands of the Tibetan Plateau, is the most sensitive territory for uplifting processes and related responses of environmental changes.It not only records the continental collision process and the deformation history of the lithosphere and crust, but it is also considered the most preferred study site to investigate the paleotopography, paleogeomorphology, and paleoclimatic evolution. In order to reveal the late Eocene to early Oligocene paleoclimate in the Lunpola Basin, a total of 67 rock samples from the second member of the Niubao Formation at 382 Daoban section in the southwest margin of the Lunpola Basin were selected. Based on major and trace elements, a variety of chemical weathering ratios and indices, including the combination of elements (C value), Rb/Sr, Sr/Cu, Sr/Ba, chemical index of alteration (CIA), elemental weathering index (α), and Ln(Al2O3/Na2O) were used to assess the intensity of weathering regimes and paleoclimatic evolution in the source area. The results showed that arid paleoclimate was prevalent during deposition of the second member in the Niubao Formation. However, there was an apparent cooling event at the boundary transition of the Eocene-Oligocene (EOT), which was not only confined to the Lunpola basin but also widely documented in the Tibetan Plateau and other regions along the circumferential margin. This Eocene-Oligocene cooling event is considered a well-developed continental response to the first global Cenozoic cooling event in the Lunpola lake basin. |
| Key words: Lunpola Basin Elemental geochemical Weathering index Eocene–Oligocene Paleoclimate |
