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| 1 | Sedimentary and geochemical evidence of Eocene climate change in the Xining Basin, northeastern Tibetan Plateau显示文摘The northeastern Tibetan Plateau began to grow during the Eocene and it is important to understand the climatic history of Asia during this period of so-called ‘doubthouse' conditions. However, despite major advances in the last few decades,the evolutionary history and possible mechanisms of Eocene climate change in the northeastern Tibetan Plateau remain unclear.The Xining Basin in the northeastern Tibetan Plateau contains a continuous sequence of Early to Late Eocene non-marine sediments which provides the opportunity to resolve long-term climate changes during this period. In this study, we report the results of analyses of lithofacies, sediment color and geochemistry of bulk samples collected from the Xijigou section of the Xining Basin. An abrupt lithofacies change between the Early(~52–40 Ma) and Late Eocene(~40–34 Ma) indicates a change in the depositional environment from a shallow lake to a playa lake in response to a significant climatic shift. During ~52–40 Ma,higher values of sediment redness(a*), redness/lightness(a*/L*) and higher modified Chemical Index of Weathering(CIW′)indicate a relatively warm and humid climate, while from ~40–34 Ma the lower values of a*, a*/L*and lower CIW′ imply subhumid to semi-arid climatic conditions. The paleoclimatic records indicate a long-term(~52–34 Ma) trend of decreasing chemical weathering, consistent with global climate change. An abrupt sharp excursion of the proxy records during ~42–40 Ma suggests a relatively brief warm interval, corresponding to the Middle Eocene Climatic Optimum(MECO). We suggest that global cooling substantially reduced humidity in inner Asia, resulting in sub-humid to semi-arid climatic conditions after 40 Ma in the Xining Basin, which may have been responsible for the long-term trend of decreasing chemical weathering during the Eocene. | Abu Sadat Md SAYEM Zhengtang GUO Haibin WU Chunxia ZHANG Fan YANG Guoqiao XIAO Zhilin HE | 2018 | Science China Earth Sciences2018，61，9： | 6 |
| 2 | Sedimentary Evolution of the Qinghai-Tibet Plateau in Cenozoic and its Response to the Uplift of the Plateau显示文摘We have studied the evolution of the tectonic lithofacies paleogeography of Paleocene-Eocene, Oligocene, Miocene, and Pliocene of the Qinghai-Tibet Plateau by compiling data regarding the type, tectonic setting, and lithostratigraphic sequence of 98 remnant basins in the plateau area. Our results can be summarized as follows. (1) The Paleocene to Eocene is characterized by uplift and erosion in the Songpan-Garzê and Gangdisê belts, depression (lakes and pluvial plains) in eastern Tarim, Qaidam, Qiangtang, and Hoh Xil, and the Neo-Tethys Sea in the western and southern Qinghai-Tibet Plateau. (2) The Oligocene is characterized by uplift in the Gangdisê-Himalaya and Karakorum regions (marked by the absence of sedimentation), fluvial transport (originating eastward and flowing westward) in the Brahmaputra region (marked by the deposition of Dazhuka conglomerate), uplift and erosion in western Kunlun and Songpan-Garzê, and depression (lakes) in the Tarim, Qaidam, Qiangtang, and Hoh Xil. The Oligocene is further characterized by depressional littoral and neritic basins in southwestern Tarim, with marine facies deposition ceasing at the end of the Oligocene. (3) For the Miocene, a widespread regional unconformity (ca. 23 Ma) in and adjacent to the plateau indicates comprehensive uplift of the plateau. This period is characterized by depressions (lakes) in the Tarim, Qaidam, Xining-Nanzhou, Qiangtang, and Hoh Xil. Lacustrine facies deposition expanded to peak in and adjacent to the plateau ca. 18-13 Ma, and north-south fault basins formed in southern Tibet ca. 13-10 Ma. All of these features indicate that the plateau uplifted to its peak and began to collapse. (4) Uplift and erosion occurred during the Pliocene in most parts of the plateau, except in the Hoh Xil-Qiangtang, Tarim, and Qaidam. The continuous uplift and intensive taphrogeny in the plateau divided the original large basin into small basins, deposition of lacustrine facies decreased considerably, and boulderstone accumulated, indicating a response to the overall uplift of the plateau. Here, we discuss the evolution of tectonic lithofacies paleogeography in Cenozoic and its response to the tectonic uplift of the Qinghai-Tibet Plateau in relation to the above characteristics. We have recognized five major uplift events, which occurred during 58-53 Ma, 45-30 Ma, 25-20 Ma, 13-7 Ma, and since 5 Ma. The results presented here indicate that the paleogeomorphic configurations of the Qinghai-Tibet Plateau turned over during the late Miocene, with high elevations in the east during the pre-Miocene switching to high contours in the west at the end of Miocene. | ZHANG Kexin WANG Guocan XU Yadong LUO Mansheng JI Junliang XIAO Guoqiao WANG An SONG Bowen LIANG Yinpin JIANG Shangsong CAO Kai CHEN Fenning CHEN Ruiming YANG Yongfeng | 2013 | Acta Geologica Sinica(English Edition)2013，87，2： | 6 |
| 3 | Magnetostratigraphy and provenance of the Qingzhou loess in Shandong province显示文摘Loess deposits with varying thickness are widely distributed on the intermontane valleys and piedmont zones on the northern side of the central Shandong mountainous regions. However, the basal ages and material resources of the loess deposits are not clear. The paper studied the Qingzhou loess profile in Shandong with magnetostratigraphic and optical stimulated luminescence (OSL) methods and further investigated its main provenances with the mineralogical methods. The magnetostratigraphic results showed that the Brunhes/Matuyama (B/M) reversal boundary was not recognized, suggesting a basal age younger than 0.78 Ma. Extrapolations by sedimentation rates, based on the upper part depositional rate from the OSL age, the basal age of the Qingzhou loess is about 0.5 Ma. Until now, older loess deposits have not been reported on the northern side of the central Shandong mountainous regions. The results of the paper indicate that the loess deposits in this area might have strated from the Middle Pleistocene. The basal age of Qingzhou loess is approximately synchronous with the Xiashu loess in the middle-lower reaches of Yangtze River. Major components of clay minerals in the Qingzhou profile are dominated by illite. Other clay mineral compositions are mainly smectite, chlorite and kaolinite, which are similar with the Xifeng loess in the Loess Plateau. However, the contents of smectite and the ratios of illite and kaolinte in the Qingzhou loess samples are higher than those in the Xifeng loess samples of the Loess Plateau, indicating that the loess in the northern side of the central Shandong mountainous regions has different sources from that of the loess deposits in the Loess Plateau. The clay mineral analysis further reinforces the earlier conclu- sion that the marine strata exposed in the Laizhou Bay and the fluvial plain of the lower reaches of Yellow River during the glacier periods are the main material sources for the Qingzhou loess deposits, which is an indicator to the local aridification of the lower reaches of the Yellow River. Loess deposition in the central Shandong mountainous regions started at around 0.5 Ma. The age of Qingzhou loess is approximately synchronous with the ongoing high-latitude cold since the Middle Pleistocene, which indicates that strengthened East Asian winter monsoon was sufficiently energetic to bring substantial quantities of material from the marine strata exposed in the Laizhou Bay and the fluvial plain of the lower reaches of the Yellow River to the central Shandong mountainous regions. The results therefore suggest that both regional geological process and global changes were responsible for the formation of Qingzhou loess since Middle Pleistocene. | ShuZhen PENG LiJun ZHU GuoQiao XIAO YanSong QIAO ZhiDong GAO DongDong CHEN | 2011 | Journal of Arid Land2011，3，3： | 3 |
| 4 | 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 |
| 5 | 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 |
| 6 | Siloles and Acetenyl Aromatics Copolymers: Synthesis, Characterization and Photophysical Properties显示文摘Two copolymers,poly(1,1-dimethyl-3,4-diphenylsilole-alt-N-hexyl-3,6-diethynylcarbazole)(PS-DyCz)and poly-(1,1-dimethyl-3,4-diphenylsilole-alt-2,7-diethynyl-9,9'-dihexylfluorene)(PS-DyF),were synthesized by Sonogashira coupling reaction of 2,5-dibromo-1,1-dimethyl-3,4-diphenylsilole and N-hexyl-3,6-diethynylcarbazole or 2,7-diethynyl-9,9'-dihexylfluorene,respectively.The chemical structures of the copolymers were characterized by NMR,FT-IR techniques.Their thermal and photophysical properties were evaluated by TGA,DSC,UV-Vis and fluorescence spectroscopy,respectively.The weight-averaged molecular weights(Mw)of PS-DyCz and PS-DyF are 1.20×10^(4) and 3.83×10^(4) Da,respectively.The degree of polymerization is 8 and 22 units.Theseπ-conjugated polymers exhibited lower band-gap of 2.25 and 2.70 eV due to the presence of silole rings and C≡C triple bonds in their backbone,the results were consistent with the density functional(DFT)calculations at the B3LYP/6-31G^(*)level. | Zhenhua He Guoqiao Lai Zhifang Li Xiao Yuan Yongjia Shen Chengyun Wang | 2015 | Chinese Journal of Chemistry2015，33，5： | 0 |
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