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黄土高原风尘堆积是开展古环境变化研究的重要沉积物,其源区的具体位置和变化程度对于揭示东亚大气环流演化具有关键意义,而且一直被学术界广泛关注,存在较大争议.前人通过地球化学(Sr-Nd-Pb同位素、元素地球化学、碎屑锆石UPb年龄)、矿物学(白云石、重矿物)、物理学(释光灵敏度、电子自旋共振信号和环境磁学)、气象观测与模拟、地貌学等方法对黄土高原风尘堆积及其潜在源区(北方荒漠和戈壁以及青藏高原东北部)开展了大量示踪研究.研究表明青藏高原东北部、阿拉善高原、塔里木盆地和蒙古戈壁可能是非常重要的源区.目前存在的问题:(1)源区的具体区位;(2)源区物质供给系统是否存在时空变化;(3)第四纪以来的黄土研究居多,而更老时间尺度上风尘堆积的物源研究较少.因此,今后开展更多粉尘物源示踪方法学的研究,并加强第四纪以前黄土高原风尘堆积的物源研究,是风尘堆积物源研究的重要内容. 相似文献
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黄土高原风尘堆积是开展古环境变化研究的重要沉积物,其源区的具体位置和变化程度对于揭示东亚大气环流演化具有关键意义,而且一直被学术界广泛关注,存在较大争议.前人通过地球化学(Sr-Nd-Pb同位素、元素地球化学、碎屑锆石U-Pb年龄)、矿物学(白云石、重矿物)、物理学(释光灵敏度、电子自旋共振信号和环境磁学)、气象观测与模拟、地貌学等方法对黄土高原风尘堆积及其潜在源区(北方荒漠和戈壁以及青藏高原东北部)开展了大量示踪研究.研究表明青藏高原东北部、阿拉善高原、塔里木盆地和蒙古戈壁可能是非常重要的源区.目前存在的问题:(1)源区的具体区位;(2)源区物质供给系统是否存在时空变化;(3)第四纪以来的黄土研究居多,而更老时间尺度上风尘堆积的物源研究较少.因此,今后开展更多粉尘物源示踪方法学的研究,并加强第四纪以前黄土高原风尘堆积的物源研究,是风尘堆积物源研究的重要内容. 相似文献
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西宁黄土碎屑锆石年龄特征及其对黄土高原黄土物源的指示意义 总被引：2，自引：0，他引：2
物源研究是理解黄土高原风成沉积物中古环境记录的关键一环.众多证据表明,黄土高原西北部的阿拉善高原及其周边广袤干旱地区是黄土高原黄土的主要风尘源区.但是,基于锆石U-Pb同位素地质年代学的证据对此提出了质疑.黄土高原黄土与青藏高原北部物质中的锆石具有相似的年龄分布,预示黄土高原风尘主要以西风搬运的方式来自青藏高原北部,特别是柴达木盆地.本研究通过分析西宁黄土的锆石年龄特征验证此假说.西宁处于在从青藏高原北部到黄土高原的假想搬运路线上.西宁黄土主要来自青藏高原北部的干旱区.西宁黄土中锆石的主要年龄分布与黄土高原黄土相似,反映青藏高原北部确实为黄土高原黄土的主要物质来源.但是,与黄土高原黄土相比,西宁黄土缺少年龄在360Ma左右和年龄小于100Ma的锆石.这两组年龄的锆石可能来自其他地区,例如处于中亚造山带.由于阿拉善于旱区也通过河流搬运接收来自青藏高原北部的物质,锆石U-Pb年龄证据并不能排除阿拉善干旱区作为主要风尘物源的可能.相反,阿拉善干旱区还接受来自其北部中亚造山带和其本身华北克拉通的物质,来自阿拉善干旱区的风尘可能更好地解释黄土高原黄土中的锆石年龄特征. 相似文献
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晚新生代黄土高原风尘序列的粒度和沉积速率与中国北方大气环流演变 总被引：33，自引：21，他引：12
文章以风尘沉积的粗粒和细粒组分与季风和西风环流的联系为基础,利用黄土高原中部的洛川剖面、西峰剖面和灵台剖面的粒度和沉积速率记录,讨论了晚新生代中国北方季风环流和西风环流的演变历史,总结了这一时期大气环流演变的基本规律和大气环流演变的动力机制.研究表明,自8～7Ma风尘沉积发育至5Ma左右,西风环流和季风环流都有减弱的趋势;自5Ma以来,西风环流和季风环流的强度都在逐步加强;与此同步,季风环流对风尘沉积的贡献增加,而西风环流对风尘的贡献逐渐减小,这一逐渐发展的大气环流趋势与北半球高纬冰盖的逐步发展有关;大气环流的这种趋势变化在8～7Ma,3.4Ma和1.2～0.9Ma这几个时期存在着突变,可能反映了青藏高原的阶段性隆升对中国北方季风环流演化的决定性作用以及对西风环流结构和强度的重要影响.中国北方大气环流在轨道尺度变化的基本特征是,低空季风环流在冰期加强,在间冰期减弱.西风环流和季风环流在冰期和间冰期的强度和格局可能主要与全球冰量的基本状况和青藏高原原面的性质有关.黄土高原的风尘记录在万年尺度和千年尺度的气候事件上都表现出相当明显的区域差异,可能主要与局部地形的大气环流效应有关. 相似文献
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黄土高原中部连续的风尘堆积黄土-红粘土序列,蕴含着东亚季风演化与高原隆升等重要的古气候与构造信息.结合已有的古地磁年代,根据磁化率的变化特征对黄土高原中部朝那黄土-红粘土剖面记录的古环境变化进行了划分,共划分I(8.1～5.6 MaBP)东亚季风的初显期、Ⅱ(5.6～4.8 MaBP)东亚夏季风开始增强期、Ⅲ(4.8～2.8 MaBP)青藏高原隆升和东亚季风波动增强期、Ⅳ(2.8～2.6 MaBP)气候转型期、V(2.6～1.2 MaBP)弱季风期、Ⅵ(1.2～0.62 MaBP)季风增强期和Ⅶ(＜0.62 MaBP)季风鼎盛期等7个阶段.并将其与全球冰量、太阳辐射进行对比,初步讨论各阶段演化的可能机制. 相似文献
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新近纪以来中国黄土高原的风尘记录 总被引：7，自引：0，他引：7
通过对黄土高原中部两个典型的风尘堆积序列的岩性和磁性地层研究 ,认为中国黄土高原风尘堆积的开始发育年龄至少约为 7.2 Ma B.P.。以红粘土和黄土—古土壤交互出现的风尘沉积 ,不仅真实地记录了东亚季风气候的形成演化 ,而且可能包含了青藏高原的阶段性隆升、北半球冰盖形成演化及大冰期发生等构造气候事件的印记。反映粉尘源区的干燥度及携带粉尘的大气环流强度的风尘沉积速率自 7.2 Ma B.P.开始、尤其是 4.5 Ma B.P.以来逐渐增大 ,似乎暗示了自新近纪以来亚洲内陆粉尘源区干旱化的逐级发展和东亚冬季风环流强度的逐渐增加 相似文献
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历史时期的雨土及近代尘暴的研究证实,风尘堆积与冬半年强冷气流活动有关。中国东部第四纪风尘堆积(黄土和下蜀土)分布的时、空变化及其粒度的不断增粗表明,第四纪以来冬季风强度是不断增加的。季风强度的变化主要与青藏高原越来越快的整体隆升有关。青藏高原上升产生了高原季风,并对西风气流和蒙古冷高压发生影响,即从三方面对季风起到增强作用。另一方面是中新生代以来地球气候变冷,使中、高纬地带的海陆分布和地形对大气环流有更大的影响。 相似文献
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Previous studies show that the thick aeolian dust deposits in the Chinese Loess Plateau (CLP) have accumulated since the early Miocene or even late Oligocene. They are considered to provide the best terrestrial record for the onset of Asian interior aridification and the evolutionary history of the Asian Monsoon. However, large variability in the basal ages of aeolian deposits makes the aeolian dust depositional history and the controlling dynamics controversial. Here, we present a preliminary hypothesis for the tectonic controls of aeolian dust deposition in the CLP by connecting the two main uplift events of the Tibetan Plateau and the regional tectonic events with the aeolian dust accumulation history. Regional tectonic events in the Ordos Block (the basement of the CLP) during the late Cenozoic are less recognized as controlling aeolian dust accumulation by sculpting the surface landscape. The stable tectonic environment of the Ordos Block since the late Miocene might have been the main controlling factor that enabled the widespread deposition of the aeolian red clay after ~8 Ma. Here, we hypothesize that because the large-scale monsoon system and central Asian aridity had existed since at least the early Miocene, the accumulation and preservation of aeolian deposits within the CLP are actually largely controlled by the regional tectonic environment and less by climatic factors. 相似文献
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《International Geology Review》2012,54(14):1861-1876
Currently mechanisms for the onset of the widespread aeolian dust accumulation in the Chinese Loess Plateau since 8–7 Ma remain elusive. In this study, we compile 11 records of climate (14–7 Ma) and tectonic activity of the Tibetan Plateau and its adjacent areas (15–6 Ma). The results suggest that strong tectonic activity in the northeastern Tibetan Plateau has produced massive debris and dust, which was deposited in the piedmont basins and reworked by weathering and fluviolacustrine erosion. At the same time, global cooling and uplift of the Tibetan Plateau over the period of 14–7 Ma intensified the East Asian winter monsoon and westerly winds (westerlies) while weakening the Asian summer monsoon, which led to the spread of dry land vegetation and aridification in interior China. Sediments in the piedmont basins were then exposed in the aridity and transported by the westerlies to the Chinese Loess Plateau and the North Pacific. We suggest that tectonic activity in the northeastern Tibetan Plateau and shifting global climate together triggered the widespread aeolian dust accumulation in the Chinese Loess Plateau and the North Pacific since 8–7 Ma. 相似文献
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在干旱气候背景下常常有风尘物质的释放和传输,风尘沉积被认为是干旱环境变化良好的地质记录。在亚洲中部和中国北方,大面积的干旱区被沙漠戈壁覆盖,这些地区是粉尘物质的重要源地,释放的风尘物质影响局地和区域环境,并通过参与生物地球化学循环等影响更大空间尺度的气候变化。因此,亚洲中部干旱气候的形成和演化以及发展趋势一直受到重视。长期以来,关于晚新生代亚洲中部干旱气候发展的驱动机制至少有两种解释:一是青藏高原的隆升控制着亚洲中部的干旱化过程,随着高原的阶段性隆升亚洲干旱气候逐步增强;二是晚新生代全球变冷直接驱动着亚洲变干,全球变冷是主导因素。中国黄土高原及其周边地区堆积的黄土-红粘土序列是指示亚洲干旱化过程良好的地质记录,通过对新获得的风尘堆积记录的分析,发现在晚新生代中国风尘堆积的时空演化与全球变冷有较好的对应,全球变冷可以促使亚洲中部干旱气候发展并加强粉尘活动,而青藏高原隆升的幅度和时间还不清楚,进而认为是全球变冷而不是青藏高原隆升直接驱动亚洲内陆的阶段性变干。基于这些结果,我们认为以前关于青藏高原隆升影响全球气候的结论可能高估了青藏高原在地球环境演化中的作用,关于高原隆升直接驱动亚洲干旱化的结论还需要检验。 相似文献
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六盘山西侧山麓剥蚀面的发育与新构造隆升 总被引：12，自引：0，他引：12
晚新生代青藏高原的隆升对其周围地貌格局和沉积产生了重大影响。地处高原东北构造边界的六盘山受其影响产生明显的地貌分异，造成黄土高原东西两部分巨大的风成沉积差异。最近对位于六盘山西侧陇中盆地东北边缘黄河最高阶地之上的山麓剥蚀面上的黄土磁性地层学研究表明该剥蚀面形成于约1.8 MaBP，与陇中盆地西南隅的兰州、临夏两地山麓剥蚀面的年龄一致〔1〕，表明在约1.8 MaBP 以前六盘山以西普遍遭受剥蚀，可能形成一级统一 的山麓剥蚀面，即所谓的甘肃期准平原，并指示在约1.8 MaBP 时，六盘山和青藏高原曾产生进一步强烈抬升，该剥蚀面发育结束，黄河出现，黄土开始堆积〔1，2〕。 相似文献
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Predominantly laminated lake sediments from a saline closed‐basin lake on the northeastern Tibetan Plateau were investigated using a multi‐proxy approach (14C‐accelerator mass spectrometry dating, smear‐slide analysis, loss on ignition, grain size, X‐ray diffraction, elemental concentration, ostracod assemblages, stable isotopes of ostracod shells) to trace the regional environmental and climatic history in the Lateglacial and Holocene. Before about 15 cal. ka BP, small saline water bodies probably filled the basin under unstable cold and harsh environmental conditions. Soon after about 14.9 cal. ka BP, a relatively deep saline lake was established, probably as a result of runoff from melting snow, ice and frozen ground in the lake's catchment. Large changes in flux of aeolian material to the lake were recorded during this initial period of formation of Lake Kuhai. Highest lake levels, a low sediment accumulation rate and less saline conditions were maintained between about 12.8 and 7.1 cal. ka BP when the aeolian influx diminished significantly. After about 7.1 cal. ka BP, the aeolian influx remained at a moderate level apart from a strongly increased dust delivery to the lake between about 6.1 and 5.4 cal. ka BP and a minor short‐lived period of slightly enhanced aeolian influx at about 2.7 cal. ka BP. The strongly enhanced dust input to the lake between 6.1 and 5.4 cal. ka BP represented the largest influx of aeolian material to Lake Kuhai during the entire Holocene. However, evidence for climatic deterioration during this period is not seen at most other palaeoclimate sites on the Tibetan Plateau, but instead a significant increase in aridity has been recorded at numerous sites in the northern foreland of the Tibetan Plateau and on the Chinese Loess Plateau. The large dust input to Lake Kuhai between 6.1 and 5.4 cal. ka BP probably did not result from a severe climate deterioration on the Tibetan Plateau itself, but from the pronounced aridity in its northern and eastern foreland. In contrast, the increase in dust influx about 2.7 cal. ka BP seems to correspond to a brief warming spell recorded at other sites on the Tibetan Plateau too. A slight increase in lake level and decrease in salinity after about 0.6 cal. ka BP suggests a slightly higher effective moisture during the final lake stage, accompanied by a somewhat larger dust influx. This apparent contradiction possibly results from enhanced human activities on the northeastern Tibetan Plateau during the last 600 years. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Junhuai Yang Dunsheng Xia Fuyuan Gao Shuyuan Wang Zixuan Chen Jia Jia Shengli Yang Zhiyong Ling 《地球科学进展》1986,35(8):863-877
The Yarlung Zangbo River is located in the southern Tibetan Plateau. Loess since the geological history and modern aeolian sand dunes are widely developed in the basin, bearing rich information on the aeolian processes and environmental evolution. In this work, we reviewed the main research progress of aeolian deposits in the Yarlung Zangbo River basin in recent years, and discussed the distribution characteristics, accumulation age, sediment characteristics and provenance and the possible formation mechanism of aeolian deposits and the history of aeolian activity. The results show that loess is mainly developed on the river’s terraces and some of the hilltops, and mostly formed since the last glacial maximum and mainly developed since Marine Isotope Stage 1 (about 14 ka BP), while aeolian sand deposit is mainly developed in the river’s wide valley, with relatively short accumulation time. The sediment particles mainly underwent mechanical transport and physical weathering, but chemical weathering was weak. Although the physical and chemical properties of sediments show some spatial changes, there still exist obvious local characteristics, which are closely related to the nearby surface sediments. Under the background of aeolian source, the local-source genesis of loess is generally recognized. The surface loose material at the bottom of valley is main material source of aeolian deposits. The evolution of aeolian activity is relatively complex. In addition to the regional climate change, the local environment is also an important factor affecting the aeolian activity and its regional difference. Based on the previous studies, we suggest that the systematic study on the physical and chemical properties of aeolian sediments, climate change since the Holocene and the impact of dust emission on human living environment should be strengthened in the future research. 相似文献
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Late Cenozoic orogenic history of Western Qinling inferred from sedimentation of Tianshui basin, northeastern margin of Tibetan Plateau 总被引：1，自引：0，他引：1
Xiuxi Wang Jijun Li Chunhui Song Massimiliano Zattin Zhijun Zhao Jun Zhang Yong Zhang Kuang He 《International Journal of Earth Sciences》2012,101(5):1345-1356
The Western Qinling orogenic belt marks the northeastern margin of the Tibetan Plateau. Its late Cenozoic orogenic history is recorded in an excellent sedimentary sequence exposed in the Tianshui sub-basin of the Longzhong basin. According to the magnetostratigraphic analysis from the Yaodian and Lamashan sections, we speculate that the late Cenozoic Tianshui basin accumulated lacustrine/floodplain deposits from ~14.8 to ~2.6?Ma. In addition, detrital apatite fission-track thermochronologic and paleocurrent data reveal that the detritus of the Tianshui basin mostly derived from the Western Qinling and that the youngest population age represents a ~14?Ma volcanic intrusion, which can be related to the lithospheric deformation and uplift of the Tibetan Plateau. Furthermore, two stages of variations in depositional facies and average accumulation rates were attributed to the pulse uplift and deformation of the Western Qinling at 9.2–7.4 and ~3.6?Ma. 相似文献
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ABSTRACTThe formation of the Qilian mountains and the evolution of adjacent basins were controlled by the uplift and northeastward growth of the Tibetan Plateau. In a field survey conducted on the main Cenozoic basin sediments in the Qilian Mountains and adjacent areas, fission track age data of apatite obtained previously were analyzed. Cenozoic tectonics and landform evolution in the area where the Qilian Mountains now stand and its response to the uplift of the Tibetan Plateau were studied. In the Oligocene Epoch, the Tibetan Plateau was initially uplifted and extended northeastward, forming the Guide-Xining-Lanzhou-Linxia foreland basin on the northern margin of the western Qinling Mountains, and the foreland basin in the area where the Qilian Mountains now stand received widespread sediments. In the Miocene, influenced by the enhanced uplift and northeastward thrust of the Tibetan Plateau, a stage of intracontinental squeezing orogeny and foreland basin splitting began in the area where the Qilian Mountains now stand. In the Pliocene Epoch, the Qilian Mountains were continuously uplifted, the basins shrank, large lake basins disappeared gradually, and large-area red-clay-type aeolian sediments appeared. During the Quaternary Period, the uplift of the Tibetan Plateau accelerated, causing a rapid rise in the altitude of the Qilian Mountains. Global climate change occurred and mountain glaciers began to develop. Quaternary moraine deposits appeared for the first time in the area, and very thick loess sediments appeared in the Longzhong area, east of the area where the Qilian Mountains now stand, forming the famous Loess Plateau. 相似文献
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由于对地球表层环境和大气环流形式产生了明显变化,青藏高原在新生代持续快速的隆升过程,就成为重要而壮观的全球变化事件之一。对该事件的关注与研究,产生了许多重要的科学概念和成果,同时也产生了许多争论。发育在青藏高原东北缘即甘肃省酒泉地区的新生界风成砂岩及其相关沉积,代表了青藏高原新生代隆升过程中造成的环境变化的特殊沉积。它们包括：〗（1）古近系白杨河组底部的风成砂岩,代表了受到印度夏季季风控制的炎热干旱环境的产物;（2）新近系疏勒河组下部的风成砂岩,表明了继续受到印度夏季季风控制的潮湿气候背景的沉积;（3）第四系玉门组冰水沉积中的风成砂岩透镜体,表现为冬季季风（或盛行西风）形成的寒冷气候下的风成砂岩。因此,研究区域的新生界风成砂岩,成为窥视青藏高原新生代隆升的沉积学响应,为研究青藏高原的新生代隆升过程提供了重要思考线索。 相似文献