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1.
晚中新世以来亚洲季风阶段性演化的海陆记录 总被引：4，自引：0，他引：4
本文在综合对比晚新生代以来中国黄土高原黄土一红粘土沉积、西北太平洋粉尘沉积、南海有孔虫、阿拉伯海有孔虫记录的基础上,探讨了大约8Ma以来亚洲季风的阶段性演化历史。结果发现,黄土高原粉尘沉积在8Ma前后大规模出现,在3．5Ma前后大幅增加;印度季风在8Ma前后形成(或显著加强);南海ODP1146站位浮游有孔虫Neoglcboquadrina丰度也有两次明显增加,表明海水表面温度不断降低和海洋生产力的增加,指示东亚冬季风作用增强。北太平洋()DP885／886钻孔风成粉尘通量也有增加,指示亚洲内陆进一步的干旱化和冬季风作用的增强。印度洋沉积通量在11Ma前后开始增加。在9～8Ma时出现峰值,表明喜马拉雅山和青藏高原南部逐渐隆起。当隆起达到足够高度时,导致亚洲内陆干旱气候带扩大,同时提供大量粉尘并向东传输到中国北方和北太平洋地区。青藏高原北缘山前盆地的沉积记录显示,在3．6Ma时,高原北部的进一步快速隆升过程可能影响到整个高原,从而导致亚洲内陆更加干旱化,东亚季风增强,粉尘沉积加快,南海及印度洋陆源沉积作用加剧。 相似文献
2.
中更新世全球最大冰期与中国沙漠扩张 总被引：10，自引：1，他引：10
位于青藏高原和西北干旱区交界带的沙沟黄土剖面, 详细记录了0.8 Ma BP以来东亚季风系统和沙漠演化的历史. L6黄土层中, 中值粒径和砂粒含量表明当时冬季风极端强盛, 沙漠大规模扩张, 其范围仅次于末次冰期最盛期. 在0.6～0.7 Ma BP以前(即深海氧同位素MIS16阶段), 北半球高纬度大陆冰盖大规模扩展, 全球冰量达到最大, 并且西伯利亚冰盖的扩展, 还使得西伯利亚高压增强; 同时, 青藏高原上也发育了最大规模的冰川, 从而强化了西风和东亚冬季风. 其结果造成了中国季风边缘区的沙漠扩张. 虽然全球冰量和青藏高原是影响沙漠演化的重要因素, 但在不同的时段其机制可能有所不同, 也不能忽略其它因素的影响. 相似文献
3.
甘肃临夏盆地新近纪红粘土粒度组成的古环境意义① 总被引：3，自引：2，他引：3
临夏盆地十里墩剖面新近纪红粘土粒度组成特征、磁化率值分析表明:8.2Ma以来,临夏盆地经历了干旱化的逐级发展和东亚冬季风的逐渐加强过程。8.2～7.4Ma,东亚冬季风形成,干旱化已经发生,风成红粘土开始在盆地沉积;7.4～6.8Ma,亚洲冬季风逐渐加强,开始影响黄土高原地区,形成大面积的红粘土堆积,盆地为半干旱～半湿润的气候环境;6.8～6.0Ma气候与构造稳定,基本维持了前期的气候特点;5.9～5.3Ma,盆地冬季风强度略有增加,为干湿与干凉交替的气候环境;5.3～4.8Ma盆地冬季风盛行、干旱化程度强烈,气候特征为干凉;4.8～4.0Ma,夏季风开始盛行,气候变的湿润。4.0Ma后,青藏高原开始发生又一次强烈隆升。 相似文献
4.
通过对柴达木盆地大红沟剖面新生代沉积物岩石磁学的研究,探讨青藏高原东北部的构造活动与气候变化。典型样品的热退磁曲线表明,磁铁矿含量随地层年代的变新而增大。沉积物的磁化率由老至新划分为5个阶段,随时代变新而不断增大,与磁铁矿含量的增大相吻合。柴达木盆地沉积物磁化率值的变化与气候变化关系密切:①约43Ma,磁化率增大是全球气候变冷变干导致沉积物中磁铁矿含量增加所致;②约33Ma,磁化率增大是全球气候加速变冷的结果;③22Ma左右,青藏高原整体隆升,控制中国大陆环境的气候系统由行星风系转变为季风风系,亚洲内陆开始干旱化,致使更多的磁铁矿得以保存,磁化率值再度增大;④14Ma青藏高原东北缘发生区域构造抬升,西北干旱区进一步扩大,东亚季风明显加强,同时全球冰量扩张,导致柴达木盆地沉积物的磁化率整体增大,而且波动幅度和频率增大。 相似文献
5.
红粘土被认为类似于黄土,也是风成沉积。六盘山东侧红粘土底部沉积年龄主要集中于8Ma左右,而西侧底部最老沉积年龄主要在25~22Ma。通过综合分析红粘土的物源,青藏高原的隆升以及亚洲内陆干旱原因等方面认为:1亚洲内陆晚渐新世—早中新世的干旱主要是青藏高原的隆升阻挡了西南气流的深入和副特提斯海向西退出造成下风向区水汽来源减少而形成。2六盘山以西红粘土的沉积主要是在西风绕流和狭管效应作用下形成。以东没有沉积底界年龄为25~22Ma的红粘土可能是那个时间段冬季风势力较弱,且受沿途山脉以及山地地区西风的阻挡,所以无法携带风尘沉积物在六盘山以东沉积。8Ma左右红粘土在六盘山以东的沉积说明冬季风势力增强,穿过了西风在山地地区的阻挡形成之。38Ma左右冬季风穿过西风在山地的阻挡携带红粘土到六盘山以东,说明蒙古西伯利亚高压已经大大增强,当时的沉积范围已与现在相当,显示环流系统接近现在的特征。同时根据青藏高原与蒙古西伯利亚高压的关系,结合青藏高原构造运动证据,8Ma左右青藏高原的强烈隆升可能对亚洲季风的演化具有重要的意义。 相似文献
6.
黄土高原红粘土的风成成因已得到一致的认可，目前发现最早的红粘土出现在渐新世末中新世初，表明古近纪末中国西北内陆地区干旱化环境就已形成。黄土高原红粘土的粒度特征显示自北而南平均粒径逐渐减小，表明了初始的季风系统已经建立，冬季风对风尘物质的传输具有重要作用。红粘土的粒度分布曲线显示其有两个组分组成，其中粗粒（>20μm）代表了近地面风（冬季风）传输部分，而细粒（<5μm）代表了高空西风传输部分，粒度组成特征很好地记录了大气环流的发展变化。自渐新世末，六盘山以西的红粘土显示在21.3～20.2 Ma、16.0～13.3 Ma和8.7～6.9 Ma三个时期平均粒径增大，沉积速率升高，其可能与全球变冷和青藏高原阶段性隆升有关，其中8.7～6.9 Ma主要受全球变冷控制。而六盘山以东的红粘土剖面，粒度变化特征显示在7.6～6.2 Ma，或至5.4 Ma粒径都较粗，表明冬季风较强；之后至3.6 Ma平均粒径较细，沉积速率较低，指示了冬季风发育较弱，为气候环境较好的阶段；从3.6～2.6 Ma，大多数剖面都显示平均粒径增大，沉积速率增加，冬夏季风同时增强，进入向第四纪冰期过渡的阶段。北极冰... 相似文献
7.
南海北部中新世以来粘土矿物特征及东亚古季风记录 总被引：4，自引：0，他引：4
应用X射线衍射(XRD)、扫描电子显微镜(SEM) 和X射线能谱(EDS) 分析技术对南海北部ODP1146站中新世以来(~20 Ma) 粘土矿物的组成、结晶学特征、微形貌和化学成分进行了研究, 分析了粘土矿物的物质来源及其记录的东亚季风演化历史.1146站粘土矿物组合的总体特点是以伊利石和蒙脱石为主, 高岭石和绿泥石含量较低.物源分析表明, 1146站蒙脱石主要来自于吕宋岛, 伊利石和绿泥石来自于珠江和台湾(长江), 而高岭石则主要来自于珠江.1146站的粘土矿物不仅被南海周围物源的同时代气候所控制, 而且为相互消长的不同传输作用(表层洋流) 的强度所影响.1146站(伊利石+绿泥石) /蒙脱石比值可以用来作为东亚季风演化的矿物学标志.指标变化显示出东亚冬季风强度和冬季风相对夏季风的强度在15 Ma、8 Ma和3 Ma左右发生了3次显著加强, 结果可以与黄土、北太平洋风尘沉积、南海微体古生物记录等很好对比.青藏高原的阶段性隆升可能促进了东亚季风的这3次加强. 相似文献
8.
季风亚洲末次冰期可统一称为大理冰期,古冰川首次出现于东亚海岸山地,内陆高山高原则冰川规模缩小。早期大理冰期冰川规模大于晚期,是季风亚洲的特色。古雪线在亚洲东海岸形成向南弯曲的大槽,是大理冰期夏季风衰弱、海陆的干湿对比加剧以及东亚大槽南移的结果。53000—27000aB.P.之间为萨拉乌苏-卡尔金斯克大间冰段,气候冷暖多变,西伯利亚冻土融化,华北平原为喜冷云杉林占据,内陆湖水面普遍升高。构造运动对古冰川发育有明显影响。青藏高原大冰盖是不存在的。 相似文献
9.
本文详细研究了陕西洛川黄土剖面中Rb,Sr的含量变化及其在不同粒级与不同相态中的分布特征。结果表明Rb在粘粒中含量高，基本只存在于残留态中，而Sr则主要分布于砂和粉砂粒级中，并以残留态与碳酸盐结合态为主要赋存相态，因此黄土和古土壤中Rb、Sr含量的差异应与冬季风驱动的粒度分选作用引起的物质组成变化及风驱动的风化成壤强度密切相关。Rb／Sr值变化实际上反映了东一业季风系统的两个相互消长因子－－冬季风与夏季风在轨道时间尺度上的循环交互特征。洛川剖面2.6Ma以来Sr含量总体演化趋势与北半球冰量变化模式的相似性验证了高纬度冰盖生长与东亚季风强度之间存在着耦合关系，而Rb含量与磁化率之间极佳的正相关关第为今后用Rb画评估成壤作用对磁化率的贡献成为可能。 相似文献
10.
本文简要综述和讨论了与亚洲古季风气候形成有关的中国及邻区新生代,特别是晚新生代构造演化的一些问题。新生代初印度一欧亚板块汇聚以来,特提斯海的消退过程,以及太平洋板块在亚洲大陆东缘和东南缘消减引致的弧后海盆(如日本海、东海、南海)的扩张和陆缘海盆(如黄海、渤海等)的出现,对于亚洲古季风形成的意义要比青藏高原隆升所起的作用更重要。青藏高原地表快速隆升在时间上滞后于高原地壳S—N方向的强烈缩短,其原因可能与青藏高原下地壳和上地幔熔融或局部熔融有关。此外,东亚古东南季风区域特征的形成还与我国华北及东南沿海构造运动导致的晚新生代地形地貌演化有着重要关联。 相似文献
11.
REORGANIZATION OF THE ASIAN MONSOON SYSTEM AT ABOUT 2.6 Ma AGO AND ITS IMPLICATIONS FOR THE RISING OF THE TIBETAN PLATEAUheChineseResearchFoundation(KZ 951 A1 2 0 4 ) 相似文献
12.
自新生代以来 ,在亚洲东部大陆边缘的裂谷系和青藏高原内部及周边地区 ,火山活动频繁发生 ,形成大量火山和火山岩 ,在一些火山区还发育有大小不等、形态不一的玛珥湖 ,其中有的积水 ,有的干枯 ,它们集中分布于雷琼、东北、青藏高原等地区 ,跨越了热带、亚热带、温带和高寒地带。从中新世的山东山旺盆地 ,早更新世东北龙岗地区的龙湾 ,到雷琼地区中晚更新世的田洋、湖光岩等 ,几乎各个时代、各种类型的玛珥和玛珥湖都有 ,玛珥湖中的沉积物从几十米到一二百米厚度不等 ,记录了不同地区、不同时段气候环境演变的历史 ,对全球变化研究有着重要意义。 相似文献
13.
气候模拟显示,中国在古近纪曾被带状干旱带控制并被大面积沙漠沉积覆盖,然而在中国境内,尤其是在青藏高原周边气候变化与青藏高原隆升耦合敏感地区却鲜有发现,一定程度制约了东亚季风起源时间和气候变化研究。本文通过岩性、沉积结构、沉积构造、石英砂颗粒表面特征、铁质黏土套的化学成分特征和风成沙丘分布面积综合分析,证实了剑川盆地古近系始新统宝相寺组中段典型沙漠沉积的存在。古风向重建显示,沙漠早期为西风控制,晚期为西北风控制并伴随有初始季风雨。综合分析区域地质证据可见,青藏高原东缘始新世中晚期经历了一个由干旱到潮湿的气候剧变事件,而沙漠的消失即为该事件的标志。研究区古近纪风向偏转、初始季风雨的出现以及沙漠的消失表明,东亚季风可能始于晚始新世。本文进一步确证了青藏高原东缘古近纪沙漠的存在,对深化研究东亚季风起源的时间及其与青藏高原隆升的耦合关系具重要意义。 相似文献
14.
《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
15.
三大自然区过渡地带近50年来气候类型变化及其对气候变化的响应 总被引：2，自引：0，他引：2
The transition area of three natural zones (Eastern Monsoon Region, Arid Region of Northwest China, Qinghai Tibet Plateau Region) is influenced by the Asian monsoon and middle latitude westerly circulation because of its special geographical position. And it is more sensitive to global climate change. The Koppen climate classification, which is widely used in the world, and the accumulated temperature-dryness classification, which is usually used in China, were used to study the climate zones and changes in the region of longitude 97.5°~108°E, latitude 33°~41.5°N, from 1961 to 2010. The changing areas of each climate zone were compared to the East Asian Summer Monsoon index, the South Asian Summer Monsoon index, the Summer Westerly index, the East Asian Winter Monsoon index, the Plateau Summer Monsoon index, the North Atlantic Oscillation index, the Southern Oscillation index, NINO3.4 index, to explore the response of the transition area of three natural zones to each climate system. According to the results, this region will become wetter when the Summer Westerly or the East Asian Winter Monsoon is relatively strong. When the East Asian Summer Monsoon or the South Asian Summer Monsoon becomes strong, the climate in low altitude region of the study area will easily become drier, and the climate in high altitude region of the study area is easily to become wetter. When the Plateau Summer Monsoon is relatively strong, the climate in the study area will easily become drier. When the North Atlantic Oscillation is relatively strong, the study area will easily become wetter. And when the El Niño is relatively strong, or the Southern Oscillation is relatively weak, the study area will easily become drier. In general, the moisture status of this region is mainly controlled by the middle latitude westerly circulation. The enhancement of the Asian summer monsoon could increase the precipitation in the southeast part of this regional, but, according to the degrees of dryness and the types of climate change in this paper, warming effects could offset precipitation increasing and make the area drier. The transition area of three natural zones is influenced by multiple interactions of climate systems from East Asia. A single climatic index, such as air temperature or precipitation, can not completely represent the regional features of climate change. As a result, areas of climate zones can be used as an important index in the regional climate change assessment. 相似文献
16.
青藏高原主夷平面形成的上限年龄为3.6MaB.P.,临夏盆地新生代湖相沉积同时结束,青藏运动开始,分为A(3.6MaB.P.),B(2.6MaB.P.)和C(1.7MaB.P.)3幕,A幕现代亚洲季风形成,B幕黄土开始堆积,C幕黄河出现;昆黄运动(1.2～0.6MaB.P.)使黄河干流切入青藏高原,大面积山地进入冰冻圈,可能导致中更新世之气候转型;共和运动造成黄河切穿龙羊峡,青海湖孤立,高原达到现代高度.中国三大自然区是高原隆升驱动大气环流改变而导致的中国最高层次的景观分异.本文讨论了8MaB.P.的有限高度隆升及亚洲干旱化的问题,亚洲夏季风22MaB.P.已经开始,是高原隆升及其它因素共同作用的结果,为亚洲古季风阶段.3.6MaB.P.才是现代亚洲季风真正开始的时期,可能北半球进入冰期也与此有密切关系. 相似文献
17.
对南海北部大洋钻探ODP1 1 48站进行稳定同位素和有孔虫分析 ,采用多种替代性指标 ,追溯上新世晚期以来东亚冬季风的演变。发现约 3 1～ 2 2MaB .P .之间 ,浮游有孔虫Globigerinoidesruber的δ13C值显著降低 ,而Neogloboquadrinadutertrei的相对丰度明显增大 ,指示冬季风急剧增强 ,并伴随表层海水温度的降低和古生产力的增高。此后 ,冬季风还有几次明显的增强 ,特别是在约 1 7MaB .P .,1 .3MaB .P .,0 .9MaB .P .,0 .6MaB .P .和0 2MaB .P .。 相似文献
18.
Characteristics of Clay Minerals in the Northern South China Sea and Its Implications for Evolution of East Asian Monsoon since Miocene 总被引：3，自引：0，他引：3
Clay mineral assemblages, crystallinity, chemistry, and micromorphology of clay particles in sediments from ODP Site 1146 in the northern South China Sea (SCS) were analyzed, and used to trace sediment sources and obtain proxy records of the past changes in the East Asian monsoon climate since the Miocene, based on a multi-approach, including X-ray diffraction (XRD) and scanning electron microscopy combined with energy dispersive X-ray spectrometry (SEM-EDS). Clay minerals consist mainly of illite and smectite, with associated chlorite and kaolinite. The illite at ODP Site 1146 has very well-to-well crystallinity, and smectite has moderate-to-poor crystallinity. In SEM the smectite particles at ODP Site 1146 often appear cauliflower-like, a typical micromorphology of volcanic smecites. The smectite at ODP Site 1146 is relatively rich in Si element, but poor in Fe, very similar to the smectite from the West Philippine Sea. In contrast, the chemical composition of illite at ODP Site 1146 has no obvious differences from those of the Loess plateau, Yellow River, Yangtze River, and Pearl River. A further study on sediment source indicates that smectite originates mainly from Luzon, kaolinite from the Pearl River, and illite and chlorite from the Pearl River, Taiwan and/or the Yangtze River. The clay mineral assemblages at ODP Site 1146 were not only controlled by continental eathering regimes surrounding the SCS, but also by the changing strength of the transport processes. The ratios of (illite+chlorite)/smectite at ODP Site 1146 were adopted as proxies for the East Asian monsoon evolution. Relatively higher ratios reflect strongly intensified winter monsoon relative to summer monsoon, in contrast, lower ratios indicate a strengthened summer monsoon relative to winter monsoon. The consistent variation of this clay proxy from those of Loess plateau, eolian deposition in the North Pacific, planktonic, benthic foraminifera, and black carbon in the SCS since 20 Ma shows that three profound shifts of the East Asian winter monsoon intensity, and aridity in the Asian inland and the intensity of winter monsoon relative to summer monsoon, occurred at about 15 Ma, 8 Ma, and the younger at about 3 Ma. The phased uplift of the Himalaya-Tibetan plateau may have played a significant role in strengthening the Asian monsoon at 15 Ma, 8 Ma, and 3 Ma. 相似文献
19.
Zr/Rb ratio in the Chinese loess sequences and its implication for changes in the East Asian winter monsoon strength 总被引：2，自引：0，他引：2
The long-term dust accumulation sequences on the Chinese Loess Plateau (CLP) provide a valuable opportunity to study the evolution of East Asian winter monsoon strength. Grain size of bulk samples of loess deposits, though widely used, is a modified measure of the strength of winter monsoon wind due to modification by post-depositional weathering and pedogenesis. This study proposes a new and reliable geochemical climate proxy that records the variability of the East Asian winter monsoon on the CLP. Six loess-paleosol sections on the Plateau were selected for measuring concentrations of the trace elements Zr and Rb as well as grain size. Variations of the Zr/Rb ratio in all the sections encompassing the last 130 ka display a generally similar pattern to that of mean grain size of bulk samples (MGSB). Though a positive correlation exists between the Zr/Rb ratio and MGSB, the correlation coefficient decreases in southern and eastern sections where intense pedogenesis occurred in the relatively warm and humid climates. Long-term Zr/Rb variation in the Lingtai section exhibits amplitudes and frequencies similar to those in MGSB and the mean grain size of quartz particles (MGSQ, accepted as a more reliable proxy than MGSB) in the upper loess-paleosol sequence over the past 2.6 Ma. However, for the underlying Red Clay formation, in the interval from about 7-2.6 Ma B.P., the MGSB record is relatively stable, whereas both the Zr/Rb ratio and MGSQ show distinct variability and display amplitudes similar to those observed in the overlying loess-paleosol sequence. These results demonstrate that the Zr/Rb ratio reflects original eolian grain size and may serve as a reliable index of the strength of East Asian winter monsoon winds. 相似文献