Isotopic fingerprints of mountain uplift and global cooling in paleoclimatic and paleoecological records from the northern Tibetan Plateau
Isotopic fingerprints of mountain uplift and global cooling in paleoclimatic and paleoecological records from the northern Tibetan Plateau
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DOI：
10.1016/j.palaeo.2021.110578
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发表时间：
2021-09
期刊：
影响因子：
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通讯作者：
M. Hou;G. Zhuang;Minghao Wu
中科院分区：
文献类型：
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作者：
M. Hou;G. Zhuang;Minghao Wu
中中新世后青藏高原北方气候生态变化的主要原因是构造隆升和全球气候变化。然而，构造作用和全球气候变化的相对作用一直是一个长期的争论。为揭示全球气候变化和构造运动对青藏高原北方区域气候和生态的复杂影响，研究了青藏高原北部3个地层序列（约1000 m）的叶蜡长链正构烷烃碳同位素（δ 13 C）和碳酸盐碳同位素（δ 13 C）、氧同位素（δ 18 O）。16 ~ 2 Ma），并与柴达木盆地（山间盆地）的古气候记录进行了对比。我们的同位素结果可以分为两个阶段。第一阶段（16-12 Ma），河西走廊和柴达木盆地δ 13 Cwax值的下降与中中新世气候适宜期（MMCO）后全球变冷同步;δ 13 Cwax值下降2‰，与全球变冷导致C4植物减少有关。第二阶段（12 Ma以来），河西走廊植物碳同位素分辨率（δ CO2-蜡）和δ 18 O值反映了相对稳定的水文气候条件，与同期柴达木盆地干旱化程度的增强相对应。柴达木盆地古水文条件的差异主要是由于隆升导致的盆地隔离和缺水加剧。晚中新世隆升的影响还表现为河西走廊持续的盆地内差异，表明与地形降水和生态有关的变化。
Post-middle Miocene changes in climate and ecology in the northern Tibetan Plateau have been attributed to tectonic uplift and global climate change. However, the relative roles of tectonism and global climate change have been a long-standing debate. To untangle the complex influences of global climate change versus the tectonism on regional climate and ecology in the northern Tibetan Plateau, we studied carbon isotopes (δ13Cwax) of leaf wax long-chainn-alkanes and carbon (δ13C) and oxygen isotopes (δ18O) of carbonates from three stratigraphic successions (ca. 16 Ma to 2 Ma) in the Hexi Corridor (foreland basin) and compare them with paleoclimate records in the Qaidam Basin (intermontane basin). Our isotopic results can be divided into two stages. In Stage 1 (16–12 Ma), a decrease of δ13Cwaxvalues in the Hexi Corridor and Qaidam Basin is synchronous with global cooling after the Mid-Miocene Climate Optimum (MMCO). We interpret the 2‰ decrease in δ13Cwaxvalues to be associated with the decline in C4plants due to the global cooling. In Stage 2 (since 12 Ma), plant carbon isotope discrimination (ƐCO2-wax) and δ18O values in the Hexi Corridor reflect relatively stable hydroclimate condition, which contracts with the enhanced aridity in Qaidam Basin during the same interval. We attribute the difference in paleohydrological conditions to the uplift-induced basin isolation and the enhancement of water deficiency in the Qaidam Basin. The effects of late Miocene uplift also manifest as persistent intra-basinal differences in the Hexi Corridor, indicating changes associated with orographic precipitation and ecology.