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Isotopic fingerprints of mountain uplift and global cooling in paleoclimatic and paleoecological records from the northern Tibetan Plateau
Palaeogeography, Palaeoclimatology, Palaeoecology ( IF 3 ) Pub Date : 2021-07-20 , DOI: 10.1016/j.palaeo.2021.110578
Mingqiu Hou 1 , Guangsheng Zhuang 1 , Minghao Wu 1
Affiliation  

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-chain n-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 δ13Cwax values 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 δ13Cwax values to be associated with the decline in C4 plants 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.



中文翻译:

青藏高原北部古气候和古生态记录中山地隆升和全球变冷的同位素指纹

青藏高原北部后中新世气候和生态的变化归因于构造抬升和全球气候变化。然而,构造运动和全球气候变化的相对作用一直是一个长期存在的争论。为解开全球气候变化与构造作用对青藏高原北部区域气候生态的复杂影响,我们研究了叶蜡长链构烷烃和碳(δ 13 C)的碳同位素(δ 13 C)和氧同位素 (δ 18O) 河西走廊(前陆盆地)三个地层序列(约 16 Ma 至 2 Ma)的碳酸盐岩,并将它们与柴达木盆地(山间盆地)的古气候记录进行比较。我们的同位素结果可以分为两个阶段。在第一阶段(16-12 Ma),河西走廊和柴达木盆地δ 13 C值的下降与中中新世气候最优(MMCO)之后的全球降温同步。我们将 δ 13 C值下降 2‰ 解释为与全球变冷导致的C 4植物减少有关。在第 2 阶段(自 12 Ma 以来),植物碳同位素鉴别 (Ɛ CO2-wax ) 和 δ 18河西走廊的 O 值反映了相对稳定的水气候条件,这与同期柴达木盆地干旱的增加有关。我们将古水文条件的差异归因于抬升引起的盆地隔离和柴达木盆地缺水的加剧。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相关的变化。

更新日期:2021-07-24
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