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<p>The aridification of inland Asia in the late Cenozoic was an important climate event, and China’s terrestrial environment also underwent a great shift during this period. We use geometric mean (GM) to integrate paleoenvironmental proxies of ostracod shells for trace element. On the basis of the original paleosalinity proxies (Sr/Ca, Ba/Ca) and paleoredox proxies (Th/U, δU, Fe/Ca×10), GM<sub>(Sr/Ca, Ba/Ca)</sub> and GM<sub>(Th/U, δU, Fe/Ca×10)</sub> are added to enhance the reliability of paleoenvironmental and paleoclimatic reconstructions. These paleosalinity and paleoredox proxies, combined with the converted paleosalinity (S) and relative water level (RWL) characteristics, can identify four paleoenvironmental evolution stages of the paleolake in the Western Qaidam Basin from the late Oligocene to early Miocene. These four stages include a deep-water environment with low salinity and strongly reducing conditions (29.32–26 Ma), a shallow-water environment with high salinity and strong oxidation (26–23 Ma), a relatively deep-water environment with low salinity and moderate oxidation (23–21.2 Ma), and a declining-water-level phase characterized by increased salinity and intensified oxidation (21.2–20.01 Ma). Accordingly, the climate in this region can also be divided into four evolutionary stages: humid, arid, relatively humid, and arid again. Ostracod fossils indicate that the Western Qaidam Basin remained generally arid between 26 – 20.01 Ma. This aridity, which was initiated around 26 Ma, was a response to the inland aridification of Asia during the late Oligocene. Our study shows that the dry and wet climate changes in the northeastern margin of the Qinghai Tibet Plateau during the late Oligocene to early Miocene (29.32–20.01 Ma) were not entirely consistent with global temperature fluctuations. Based on the evolution of the global climate, we infer that the significant uplift of the Tibetan Plateau and the westward retreat of the Paratethys Sea were the primary reasons for the overall aridification in the northeast margin of the Tibetan Plateau from the late Oligocene (26 Ma).</p>

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Paleoclimatic evolution of the northeastern Tibetan Plateau margin during the Late Oligocene-Early Miocene: Evidence from Ostracod shell trace elements

  • 期刊论文

  • 发表日期：

    2026年7月29日

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  • Wei Chen,
  • Jinlong Ma,
  • Xiaofeng Wang,
  • Xuan Li,
  • Liang Zeng,
  • Xiaoqing Jiang,
  • Ping Yang,
  • Houyong Luo,
  • Ke Yin

摘要

The aridification of inland Asia in the late Cenozoic was an important climate event, and China’s terrestrial environment also underwent a great shift during this period. We use geometric mean (GM) to integrate paleoenvironmental proxies of ostracod shells for trace element. On the basis of the original paleosalinity proxies (Sr/Ca, Ba/Ca) and paleoredox proxies (Th/U, δU, Fe/Ca×10), GM(Sr/Ca, Ba/Ca) and GM(Th/U, δU, Fe/Ca×10) are added to enhance the reliability of paleoenvironmental and paleoclimatic reconstructions. These paleosalinity and paleoredox proxies, combined with the converted paleosalinity (S) and relative water level (RWL) characteristics, can identify four paleoenvironmental evolution stages of the paleolake in the Western Qaidam Basin from the late Oligocene to early Miocene. These four stages include a deep-water environment with low salinity and strongly reducing conditions (29.32–26 Ma), a shallow-water environment with high salinity and strong oxidation (26–23 Ma), a relatively deep-water environment with low salinity and moderate oxidation (23–21.2 Ma), and a declining-water-level phase characterized by increased salinity and intensified oxidation (21.2–20.01 Ma). Accordingly, the climate in this region can also be divided into four evolutionary stages: humid, arid, relatively humid, and arid again. Ostracod fossils indicate that the Western Qaidam Basin remained generally arid between 26 – 20.01 Ma. This aridity, which was initiated around 26 Ma, was a response to the inland aridification of Asia during the late Oligocene. Our study shows that the dry and wet climate changes in the northeastern margin of the Qinghai Tibet Plateau during the late Oligocene to early Miocene (29.32–20.01 Ma) were not entirely consistent with global temperature fluctuations. Based on the evolution of the global climate, we infer that the significant uplift of the Tibetan Plateau and the westward retreat of the Paratethys Sea were the primary reasons for the overall aridification in the northeast margin of the Tibetan Plateau from the late Oligocene (26 Ma).