Qaidam Basin paleosols reflect climate and weathering intensity on the northeastern Tibetan Plateau during the Early Eocene Climatic Optimum
Qaidam Basin paleosols reflect climate and weathering intensity on the northeastern Tibetan Plateau during the Early Eocene Climatic Optimum
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柴达木盆地古土壤反映了青藏高原东北部早始新世气候最适宜期的气候和风化强度
DOI：
10.1016/j.palaeo.2018.03.027
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Wang Chaowen
中科院分区：
文献类型：
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作者：
Song Bowen;Zhang Kexin;Zhang Li;Ji Junliang;Hong Hanlie;Wei Yi;Xu Yadong;Algeo Thomas J.;Wang Chaowen
古土壤作为一种重要的地质档案，被广泛用于古环境和古气候条件的重建。本文对柴达木盆地始新统（~52 ~ 44 Ma）陆乐河组河流段13个古土壤层位的成土碳酸盐的黏土矿物学特征和碳氧同位素组成进行了详细分析。成土蒙脱石和伊利/蒙脱石（I/S）混合层矿物是古土壤中主要的粘土矿物，表明柴达木盆地早始新世的古气候具有强烈的季节性，夏季暖湿气候。土壤碳酸盐结核δ13C（平均值- 7.1 ± 0.8‰）重建的高成土蒙脱石产量和高大气co2值与早始新世气候适宜期（EECO）的高温一致。同期古土壤碳酸盐结核估算的古地表水组成（δ18Opsw）值为−7.9‰~−6.0‰（VSMOW），显著高于柴达木盆地现代夏季降水的δ18O值。估计的温差（~5.0 °C冷却）意味着研究区抬升了近1000 m，达到目前平均海拔~3000 m。该古海拔估算值与全球降水同位素网络（GNIP）在同一海拔范围内的亚洲站点的现代大气水同位素一致。
As an important geological archive, paleosols have been widely used in reconstruction of paleoenvironmental and paleoclimatic conditions. In this study, we undertook detailed analyses of the clay mineralogy and carbon and oxygen isotopic compositions of pedogenic carbonates in a series of 13 paleosol horizons within a fluvial section of the Eocene (~52–44 Ma) Lulehe Formation in the Qaidam Basin. Pedogenic smectite and illite/smectite (I/S) mixed-layer minerals are the predominant clay minerals in the paleosols, suggesting that the early Eocene paleoclimate of the Qaidam Basin was strongly seasonal with warm-wet summers. The high levels of pedogenic smectite production and high atmosphericpCO2reconstructed from soil carbonate nodule δ13C (mean −7.1 ± 0.8‰) are consistent with elevated temperatures during the Early Eocene Climatic Optimum (EECO). Coeval paleosol carbonate nodules yield estimated paleo-surface water compositions (δ18Opsw) of −7.9‰ to −6.0‰ (VSMOW), which are significantly higher than the δ18O value of modern summer precipitation in the Qaidam Basin. The estimated temperature difference (~5.0 °C cooling) implies uplift of the study area by nearly 1000 m to its current average elevation of ~3000 m above sea level. This paleoelevation estimate agrees with modern meteoric water isotopes of Global Network of Isotopes in Precipitation (GNIP) sites in Asia in the same elevation range.