| 青海共和盆地早全新世古风向重建及其对黄土物源的指示 |
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| 引用本文： | 田少华,肖国桥,戴高文,赖忠平.青海共和盆地早全新世古风向重建及其对黄土物源的指示[J].第四纪研究,2020(1):95-104. |
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| 作者姓名： | 田少华 肖国桥 戴高文 赖忠平 |
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| 作者单位： | 中国地质大学（武汉）地理与信息工程学院;中国地质大学（武汉）;中国地质大学（武汉）环境学院;汕头大学海洋科学研究院 |
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| 基金项目： | 国家自然科学基金项目(批准号:41672338)资助。 |
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| 摘 要： | 青藏高原东北部地处黄土与沙漠的过渡地区,在冰期-间冰期旋回中受中纬西风与东亚季风环流的交替控制,曾发生大范围的沙漠进退,是黄土高原重要的潜在物源区。恢复该区地质历史时期的大气环流格局可为重建东亚地区的环境面貌、探讨黄土高原的物源区、检验东亚地区古气候模拟结果的有效性等方面提供重要依据。但目前对高原东北部的古大气环流特征却鲜有研究。青藏高原东北部保存有一系列的古沙丘,可为古大气环流的重建提供直接依据。本文选取青海共和盆地一处代表性新月形古沙丘开展光释光测年研究,并通过其平面形态和前积层产状恢复了当时的古风向。结果表明:共和盆地的风沙活动自早全新世以来开始显著减弱,此时近地面盛行与现今风向一致的西北风。前人的研究揭示出青藏高原东北部在冰期时很可能盛行西风,并存在广泛的荒漠化,因而很可能是黄土高原冰期时重要的物源区之一。而本研究指示,该区的盛行风向在早全新世以来转变为西北风,且荒漠范围显著退缩,导致其全新世不再是黄土高原的物源区。青藏高原东北部的盛行风向和荒漠范围在冰期-间冰期旋回中的这种变化,为理解黄土高原的粉尘物源在空间和冰期-间冰期旋回上的变化提供了依据。
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| 关 键 词： | 青藏高原东北部 共和盆地 古沙丘 古大气环流 黄土物源 |
RECOVERY OF EARLY HOLOCENE PALEOWIND DIRECTION FROM THE GONGHE BASIN IN NORTHEASTERN TIBETAN PLATEAU AND ITS IMPLICATIONS FOR PROVENANCE OF CHINESE LOESS |
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| Tian Shaohua,Xiao Guoqiao,Dai Gaowen,Lai Zhongping.RECOVERY OF EARLY HOLOCENE PALEOWIND DIRECTION FROM THE GONGHE BASIN IN NORTHEASTERN TIBETAN PLATEAU AND ITS IMPLICATIONS FOR PROVENANCE OF CHINESE LOESS[J].Quaternary Sciences,2020(1):95-104. |
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| Authors: | Tian Shaohua Xiao Guoqiao Dai Gaowen Lai Zhongping |
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| Institution: | (School of Geography and Information Engineering,China University of Geosciences(Wuhan),Wuhan 430074,Hubei;Hubei Key Laboratory of Critical Zone Evolution,China University of Geosciences(Wuhan),Wuhan 430074,Hubei;School of Environmental Studies,China University of Geosciences(Wuhan),Wuhan 430074,Hubei;Institute of Marine Science,Shantou University,Shantou 515063,Guangdong) |
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| Abstract: | The Northeastern Tibetan Plateau(NETP)is located in the transitional zone between the Chinese Loess Plateau(CLP)and interior Asian deserts.Its climate is influenced by the interplay of the mid-latitude Westerlies and East Asian monsoon circulations.Previous studies suggested significant desert advance and retreat in the NETP on glacial-interglacial cycles,indicating that this area may serve as an important potential source area for the Chinese Loess Plateau in glacial times.Reconstruction of paleo-atmospheric circulation pattern of the NETP would provide essential evidence for reconstructing the paleo-environment of this area,exploring the provenance of the CLP,and assessing the validity of climate models for East Asia.However,there is still lack of the paleo-atmospheric circulation reconstruction for the NETP.Our recent field investigation revealed that the Gonghe Basin(35°30'~37°00'N,98°30'~101°30'E)in the NETP preserves large amounts of ancient dunes,which could provide direct evidence of paleo-wind directions.Based on the optically stimulated luminescence(OSL)dating and the foreset bedding dip directions,we reconstructed the paleo-wind directions from a representative inactive barchan dune that laying on the Santala platform(the oldest Yellow River terrace)in the Gonghe Basin.The studied dune(35.917°N,100.226°E;3187 m a.s.l.)is over 5.5 m in thick,and covered by 1.6 m-thick loess.The results indicate that the dune was fixed in the Earliest Holocene(ca.11.3 ka),and it was formed by a northwest paleo-wind,consistent with the direction of current winter monsoon.Our results suggest that the climate of NETP have been dominated by East Asian monsoon circulations since the Earliest Holocene.Specifically,the onset of the East Asian winter monsoon probably has led to a northwest wind,and the increase of summer monsoon rainfall probably has significantly weakened the aeolian activities in the Gonghe Basin.These results are in line with previous studies on the reconstruction of Holocene Asian monsoon history and the modelling results of Holocene wind directions.Previous studies have demonstrated that,during the last glacial period,there were widely distributed deserts in the NETP,and the area was probably dominated by westerly winds.These scenarios were significantly different from the Holocene that the area was covered by loess and dominated by the northwest winds.As such,the NETP was likely to be one of important source areas of the CLP in the last glaciation,because these deserts were located in the upwind of the CLP.However,the NETP were no longer as the source area of the CLP since the Earliest Holocene,as these deserts have significantly retreated and the wind direction has changed.The periodically variations of deserts and wind directions over the NETP during the Late Quaternary glacial-interglacial cycles were thus probably the main reasons for the spatial and glacial-interglacial variations in loess provenance of the CLP. |
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| Keywords: | Northeastern Tibetan Plateau Gonghe Basin sand dune paleo-atmospheric circulation the provenance of loess |
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