Cenozoic Environmental Changes in the Northern Qaidam Basin Inferred from n-alkane Records  

作　　者：LIU Zhonghui ZHANG Kexin SUN Yuanyuan LIU Weiguo LIU Yusheng(Christopher) QUAN Cheng 

机构地区：[1]Department of Earth Sciences, The University of Hong Kong [2]State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences [3]Institute of Earth Environment, Chinese Academy of Sciences [4]Department of Biological Sciences, East Tennessee State University,Johnson City, Tennessee 37614-1710,USA [5]Research Center of Paleontology and Stratigraphy, Jilin University

出　　处：《Acta Geologica Sinica(English Edition)》2014年第5期1547-1555,共9页地质学报（英文版）

基　　金：partially supported by the National Basic Research Program of China (2010CB833406);National Natural Science Foundation of China (NSFC 41172008 and 41372002);Distinguished Young Scientist of Ministry of Land and Resources, China, and Hong Kong RGC (HKU 703809P);HKU research facility was supported by the Special Equipment Grant from the University Grants Committee of the Hong Kong Special Administrative Region, China (SEG_HKU01)

摘　　要：Cenozoic climatic and environmental changes in the arid Asian interior, and their possible relations with global climatic changes and the Tibetan Plateau uplift, have been intensively investigated and debated over past decades. Here we present 40-Myr （million years）-long n-alkane records from a continuous Cenozoic sediment sequence in the Dahonggou Section, Qaidam Basin, northern Tibetan Plateau, to infer environmental changes in the northern basin. A set of n-alkane indexes, including ACL, CPI and Paq, vary substantially and consistently throughout the records, which are interpreted to reflect relative contributions from terrestrial vascular plants vs. aquatic macrophytes, and thus indicate depositional environments. ACL values vary between 21 and 30; CP1 values range from 1.0 to 8.0; and Paq values change from 〈0.1 to 0.8 over the past 40-Myr. We have roughly identified two periods, at 25.8-21.0 Ma （million years ago） and 13.0-17.5 Ma, with higher ACL and CPI and lower Paq values indicating predominant lacustrine environments. Lower ACL and CPI values, together with higher Paq values, occurred at 〉25.8 Ma, 17.5-21.0 Ma, and 〈13.0 Ma, corresponding to alluvial fan/river deltaic deposits and shallow lacustrine settings, consistent with the observed features in sedimentological facies. The inferred Cenozoic environmental changes in the northern Qaidam Basin appear to correspond to global climatic changes.Cenozoic climatic and environmental changes in the arid Asian interior, and their possible relations with global climatic changes and the Tibetan Plateau uplift, have been intensively investigated and debated over past decades. Here we present 40-Myr （million years）-long n-alkane records from a continuous Cenozoic sediment sequence in the Dahonggou Section, Qaidam Basin, northern Tibetan Plateau, to infer environmental changes in the northern basin. A set of n-alkane indexes, including ACL, CPI and Paq, vary substantially and consistently throughout the records, which are interpreted to reflect relative contributions from terrestrial vascular plants vs. aquatic macrophytes, and thus indicate depositional environments. ACL values vary between 21 and 30; CP1 values range from 1.0 to 8.0; and Paq values change from 〈0.1 to 0.8 over the past 40-Myr. We have roughly identified two periods, at 25.8-21.0 Ma （million years ago） and 13.0-17.5 Ma, with higher ACL and CPI and lower Paq values indicating predominant lacustrine environments. Lower ACL and CPI values, together with higher Paq values, occurred at 〉25.8 Ma, 17.5-21.0 Ma, and 〈13.0 Ma, corresponding to alluvial fan/river deltaic deposits and shallow lacustrine settings, consistent with the observed features in sedimentological facies. The inferred Cenozoic environmental changes in the northern Qaidam Basin appear to correspond to global climatic changes.

关 键 词：northern Tibetan Plateau Qaidam Basin CENOZOIC N-ALKANES PALEOENVIRONMENT 

分 类 号：P534.6[天文地球—古生物学与地层学]