| 摘要: |
| 始新世—渐新世是新生代气候从“温室”向“冰室”转变的重要节点，也是青藏高原及邻区气候格局发生重大变革的关键时期。为了重建高原中部腹地始新世—渐新世的古气候演变特征，探讨古气候变化的控制因素，利用X射线衍射分析对高原中部伦坡拉盆地382道班剖面的黏土矿物特征进行了综合研究，结果显示，伦坡拉盆地在始新世—渐新世牛堡组二段沉积的黏土矿物主要以伊利石为主，伊/蒙混层次之，高岭石与绿泥石含量极少，蒙脱石仅出现在极少样品中。黏土矿物类型及组合特征指示伦坡拉盆地在该时期整体处于寒冷干旱的气候条件，但在长周期趋势下伊利石相对含量逐渐减少，伊/蒙混层逐渐增多，显示出青藏高原中部地区的气候系统在晚始新世—早渐新世时期存在向更加湿润的气候条件转变，这种气候系统的改变可能与南亚季风在晚始新世的演化所带来的更多水汽条件和青藏高原中部中央分水岭的形成有关，但在始新世与渐新世之交，伊利石含量陡然增多，而伊/蒙混层含量则减少，且两者频繁波动，这反映了该盆地在EOT时期受到全球降温的影响。 |
| 关键词: 黏土矿物 古气候 晚始新世—早渐新世 青藏高原腹地 南亚季风 |
| DOI：10.19826/j.cnki.1009-3850.2023.02021 |
| 附件 |
| 投稿时间：2022-10-21修订日期：2022-12-06 |
| 基金项目: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）资助 |
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| Late Eocene-Early Oligocene clay mineral characteristics and paleoclimate significance in Lunpola Basin, Tibet |
| LU Chang, XIA Guoqing, CHEN Yun, WU Jinxuan, BAO Wancheng, FAN Qiushuang, SHI Zhu, HAO Xiawei |
(1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China;
2. Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China;
3. No.2 Oil Extraction Plant, Sinopec Northwest China Petroleum Bureau, Bayingol 841604, China;
4. Research Institute No.280, CNNC, Deyang 618300, China) |
| Abstract: |
| The Eocene-Oligocene Transition (EOT) is an important node of the Cenozoic climate transition from "greenhouse" to "icehouse" worldwide, especially on the Qinghai-Tibet Plateau and adjacent regions. In order to reconstruct the paleoclimatic evolution and controlling factors during the Eocene-Oligocene in the central hinterland of the Tibetan Plateau, clay mineral characteristics of 382 Daoban section in Lunpola Basin were analyzed by X-ray diffraction. Results show that the clay minerals deposited during the Eocene-Oligocene within the Second member of the Niubao Formation comprised of illite, illite/smectite mixed layers (I/S), kaolinite, chlorite and montmorillonite. Generally, the illite is the most abundant clay mineral, followed by I/S, while the kaolinite and chlorite contents are very low, and montmorillonite only appears in a few samples. Characteristics of clay minerals indicate that the Lumpola Basin was in a prolonged cold-dry climate conditions during this period, but a long-term decline in illite and rise in I/S contents indicating that the climate system in the central Tibetan Plateau changed to a more humid climate during this period. Such change could be related to the paleogeographic backgrounds of central Tibet and the evolution of South Asia monsoon since the late Eocene. However, at the EOT, illite content steeply increased, while the I/S content decreased and both fluctuated frequently, which reflects the influence of global cooling in the central Tibetan Plateau. |
| Key words: Clay minerals paleoclimate Late Eocene-Early Oligocene the central hinterland of the Tibetan Plateau South Asia Monsoon |
