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| 1 | Sr-Nd-Pb Isotopic Compositions of the Neogene Eolian Deposits in the Xining Basin and Implications for Their Dust Sources显示文摘The Neogene eolian deposits in the Xining Basin are valuable archive for studying the evolution of the Asian monsoon system and geomorphic processes of Northwest China. The Neogene eolian deposits that paleomagnetically dated at about 14 Ma probably were sourced from the middle and west Qinghai-Tibetan Plateau(QTP) as indicated by elemental compositions and magnetic properties. This study provides the Sr-Nd-Pb isotopic ratios of different sediments(gravels from the river terraces, Neogene eolian deposits and Quaternary loess) in the Xining Basin. The results show that:(1) Sr-Nd isotopic compositions of terrace gravels are different from those of the Neogene and Quaternary eolian deposits, although the Nd isotope ratios of gravel on the 10 th terrace(T10) and eolian deposits are similar.(2) Pb isotopic compositions of river gravels are obviously different from the eolian deposits in the Xining Basin. However, Pb isotopic compositions of eolian deposits in the basin are similar to those of eolian deposits in the central Chinese Loess Plateau.(3) Sr-Nd-Pb isotope results indicate that the Neogene eolian deposits in the Xining Basin were probably sourced from remote areas outside of the basin by long-distance transportation. The Qaidam Basin is probably an important source area for the eolian deposits in the Xining Basin. | Fangming Zeng Meiyan Liang Shuzhen Peng Dongmei Yu Shuyuan Xiang | 2015 | Journal of Earth Science2015，26，5： | 4 |
| 2 | Cenozoic tectonic and geomorphic evolution of the Longxi region in northeastern Tibetan Plateau interpreted from detrital zircon显示文摘The Longxi region contains different kinds of Cenozoic sediments,including eolian deposits,reworked loess,fluvial and lacustrine deposits.The provenance evolution of these sediments is of great significance in exploring the uplift,tectonic deformation and associated with geomorphic evolution of the Northeastern Tibetan Plateau.In this paper,we used the single-grain zircon provenance analysis to constrain the provenances for the Paleogene alluvial conglomerates and for the Neogene fluvial-lacustrine sediments,and compared them with results from the loess deposits since the Miocene.The results show that:(1)the Paleogene alluvial conglomerates contain a large number of detrital zircons ranging from 560 to 1100 Ma that were derived from the Yangzi Block.However,the sediments of early Miocene have much fewer zircons of this age span,which are characterized by an abundance of zircon ages in the ranges of 200-360 Ma.This indicates that the Paleogene alluvial conglomerates mainly come from the middle and/or southern West Qinling,and the early Miocene sediments are primarily from the northern West Qinling;(2)Late Neogene fluvial sediments(11.5 Ma onward)in Tianshui-Qinan region are dominated by zircon ages of 3 80-450 Ma.This zircon population is similar to that of the exposed intrusive rocks of southern part of the Liupan Mountains,implying that the southern part of Liupan Mountains probably had already uplifted by 11.5 Ma;(3)Late Miocene lacustrine sediments in Tianshui region have a zircon age spectra that is remarkably different from coeval fluvial deposits,but is similar to the zircon age distributions of the Miocene loess in Qinan region,late Miocene-Pliocene Hipparion red clay and Quaternary loess.This indicates that fine particles within these Miocene lacustrine sediments in Tianshui region may be dominated by aeolian materials.This study reveals that provenance changes of Cenozoic sediments in Tianshui-Qinan region and its geomorphic evolution are closely related to the multi-stage uplift of the Northeastern Tibetan Plateau.In particular,the major uplift of the Northern Tibetan Plateau during late Oligocene-early Miocene may have not only provided the source areas and wind dynamic conditions for the deposits of the Miocene loess,but also provided the geomorphic conditions for its accumulation. | WANG ZhiXiang LIANG MeiYan SUN YuQi DAI GaoWen | 2017 | Science China Earth Sciences2017，60，2： | 4 |
| 3 | Detrital-Zircon Evidence for the Origin of the Late Quaternary Loess in Qingzhou,Shandong Province and Its Implications for the Evolution of the Yellow River显示文摘The loess depositions in Shandong Province are important parts of loess records in eastern China,but their origin and genetic linkage between the Yellow River and the Chinese Loess Plateau are still unclear.This paper presents the detrital-zircon evidence for the origin and provenance evolution of the Qingzhou loess in Shandong Province.The results show that:(1) the Qingzhou loess was sourced from the sandy lands within the North China Plain that were fed by the silty materials from the Chinese Loess Plateau,the mountainous region in central Shandong Province,and the Yanshan and Taihang Mountains;(2) the Qingzhou loess was mainly sourced from the loess materials transported by the Yellow River,and the basal age of the Qingzhou loess indicates the timing of intensified aridification of the North China Plain and integration of the Yellow River was not later than 0.5 Ma;and(3) the provenance and grain-size of the Qingzhou loess underwent a significant transition at ~0.22 Ma,which was related to the expansion of the sandy land within the North China Plain.Our results indicate that the origin of the loess on the North China Plain are obviously different from the loess on the Chinese Loess Plateau,and the increase of grain-size and accumulation rate in the loess records on the North China Plain at ~0.22 Ma was due to the environmental deterioration of the eastern China. | Yanfei Shen Meiyan Liang Jianxun Wu Shuzhen Peng Guoqiao Xiao | 2022 | Journal of Earth Science2022，33，1： | 1 |
| 4 | Distribution of n-alkanes in Miocene loess in Qinan, western Chinese Loess Plateau, and its palaeoenvironmental implications显示文摘Neogene eolian successions are one of the most important terrestrial palaeoenvironmental archives in East Asia.However, they have received far less attention than Quaternary loess deposits, especially in the case of lipid biomarker analysis.In order to obtain a better insight into the early-middle Miocene palaeoenvironment, we conducted a study of n-alkane biomarkers from sediments of the QA-I section(Qinan) in the western Chinese Loess Plateau, and compared the results with those of previous n-alkane analyses of eolian and aquatic sediments of varying age. Our principal results are as follows:(1) All QA-I samples contain n-alkanes ranging from C_(14) to C_(35), among which the relative content of short-chain n-alkanes(C_(14)–C_(20)) from microorganisms is significantly greater than that of long-chain n-alkanes(C_(26)–C_(35)) from the waxes of terrestrial higher plants;the main peak is at C_(16)–C_(18). All samples have a relatively lower abundance of medium-chain n-alkanes(C_(21)–C_(25)) than that of long-and short-chain n-alkanes, similar to strongly weathered palaeosols in Quaternary loess and Late Miocene-Pliocene Hipparion Red-Earth; however, this distribution is significantly different from that in weakly-weathered loess of Quaternary loess and Late Miocene-Pliocene Hipparion Red-Earth, as well as from aquatic sediments.(2) Despite some odd-over-even carbon predominance of long-chain n-alkanes in the QA-I samples, the carbon preference index(CPI) values are significantly lower than those of most of the weakly-weathered sediments. Our results show that strong weathering and microbial processes have significantly altered the n-alkanes in the Miocene eolian deposits in Qinan, and led to a significant oxidation and degradation of long-chain n-alkanes and the predominance of short-chain n-alkanes from bacteria. Therefore, the contribution of microorganism to total organic carbon(TOC) and its resulting in carbon isotopic composition should be carefully assessed in future studies. | SHEN JiaHeng XIAO GuoQiao WANG ZhiXiang SUN Qing WU HaiBin ZHANG ChunXia GUO ZhengTang | 2017 | Science China Earth Sciences2017，60，5： | 1 |
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