Leaf wax stable isotopes from Northern Tibetan Plateau: Implications for uplift and climate since 15 Ma
Leaf wax stable isotopes from Northern Tibetan Plateau: Implications for uplift and climate since 15 Ma
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DOI：
10.1016/j.epsl.2014.01.003
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发表时间：
2014-03
影响因子：
5.3
通讯作者：
G. Zhuang;M. Brandon;M. Pagani;S. Krishnan
中科院分区：
文献类型：
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作者：
G. Zhuang;M. Brandon;M. Pagani;S. Krishnan
摘要青藏高原的发育被认为在亚洲气候演变过程中发挥了关键作用。然而，由于缺乏能够提供海拔和气候演变平行信息的年代确定的沉积序列，我们对高原生长和亚洲气候变化之间关系的理解是有限的。本文报道了青藏高原北方柴达木盆地新近纪连续地层（15-1.8 Ma）中叶蜡正构烷烃（δ D n-alk）稳定氢同位素组成的高分辨率时间序列记录。这些数据被用来重建大气沃茨的同位素组成（δ Dm），并随后用于解释柴达木盆地的古地形和气候历史。结果表明，柴达木盆地水文演化经历了四个阶段。第一阶段（15 ~ 10.4Ma），δ Dm从-24.9 ‰逐渐降低到-75.5 ‰，与构造活动期同步。估计的2.1± 0.3km的地形增长与柴达木盆地相对于河西走廊前陆的高度相当。我们注意到，C3植物在该地区占主导地位，因为中新世，我们把这作为独立的证据，该地区是山区之前，晚中新世和上新世的C4扩张。δ Dm在随后阶段的变化似乎与干湿条件的变化有关，而与地形变化无关，这一结论得到了青藏高原其他独立气候记录的支持。第二阶段（10.4 ~ 6.9Ma）δ Dm值偏高，与严重干旱有关;第三阶段（6.9 ~ 4.1Ma）δ Dm值偏低，与东亚夏季风加强有关。第IV阶段（4.1 Ma ~ 1.8 Ma）δ Dm值较高，反映了当时的气候比现在干燥。
Abstract The growth of Tibetan Plateau is considered to have played a key role during the evolution of Asian climate. Our understanding of the relationship between the plateau growth and Asian climate changes is limited, however, due to the scarcity of well-dated sedimentary sequences that could provide parallel information of the evolution of elevation and climate. Here, we report a high-resolution time series record of the stable hydrogen isotopic composition of leaf-wax n-alkanes (δ D n-alk) from a continuous Neogene stratigraphic sequence (15–1.8 Ma) from the Qaidam basin on the northern Tibetan Plateau. These data are used to reconstruct the isotopic composition of meteoric waters (δ D m) and subsequently applied to interpret the history of paleotopography and climate in Qaidam. Our results indicate four stages in the evolution of hydrology in the Qaidam basin. In Stage I (15 Ma to 10.4 Ma), δ D m gradually decreases from− 24.9‰ to− 75.5‰, synchronous with a period of active tectonism. The estimated topographic growth of 2.1±0.3 km is comparable to the height of Qaidam basin relative to the foreland Hexi Corridor. We note that C 3 plants were dominant in this region since the Miocene; we take this as independent evidence that this area was mountainous before the C 4 expansion in late Miocene and Pliocene. δ D m variability in subsequent stages appears to be related to shifts in dry and moist conditions and independent of topographical changes—a conclusion supported by other independent climatic records on the Tibetan Plateau. High δ D m values in Stage II (10.4 Ma to 6.9 Ma) are related to severe aridity, and Stage III (6.9 Ma to 4.1 Ma) is marked by low δ D m values, suggestive of moist conditions related to the strengthening East Asia Summer Monsoon. High δ D m values in Stage IV (4.1 Ma to 1.8 Ma) reflect a climate, drier than the present.