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中更新世以来若尔盖盆地环境演化与黄土高原比较研究 总被引：23，自引：2，他引：23
综合若尔盖盆地RH孔的研究成果与RM孔的初步分析,重建了青藏高原东部中更新世以来构造-气候演化过程,并具体地将RH孔的21个阶段和洛川黄土记录进行对比,分析其异同点,探讨了高原不同隆升阶段高原自身环境特点及其对邻近的西北干早区的影响。 相似文献
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基于古地磁和AMS14C定年结果,对长江三角洲太湖平原的WJ孔进行岩性特征、矿物磁学、粒度分析及有孔虫化石研究,拟重建WJ孔记录的晚第四纪以来沉积环境演变过程与海侵事件,并探讨环境磁学参数对河口三角洲地区沉积环境演化的指示意义.研究结果表明,WJ孔可以划分为中更新世阶段I、中更新世阶段II、晚更新世、全新世四个阶段,沉积地貌环境分别为:河湖、滨海-阶地、河口坝-河口湾-潮滩与阶地、湖沼平原.WJ孔揭示了三次海侵事件,分别为中更新世晚期海侵,晚更新世MIS5海侵和晚更新世MIS3海侵.其中记录的MIS5e海侵最为强盛,MIS3后期也存在一次海侵加强事件.另外,滨海潮滩-河口坝环境的沉积物磁性特征明显,χlf、SIRM、HIRM等为显著高值. 相似文献
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《地球物理学进展》2016,(5)
致密砂岩孔喉细小,孔隙结构和孔隙表面性质复杂.深入理解电学参数变化规律对认识储层孔隙结构和含油气饱和度具有重要意义.本文选取鄂尔多斯盆地上古生界二叠系某致密砂岩气藏18块岩样,采用自吸増水法建立含水饱和度,测定岩样原地有效应力25 MPa下的电学参数,并采用压汞实验分析了岩样孔隙结构.原地有效应力下,致密砂岩的岩性系数a大于1、b小于1,胶结指数m、饱和度指数n均小于2,反映出致密砂岩的次生孔隙类型和片状孔喉特征;渗透率增加,岩性系数b缓慢增加,饱和度指数n主要介于1.0~1.5之间;在对数坐标系中,低含水饱和度阶段,部分岩石电阻率增大系数与含水饱和度的关系线发生弯曲,出现非阿尔奇现象;高含水饱和度阶段,随含水饱和度增加,部分岩石电阻率增大系数与含水饱和度RI-Sw关系线出现饱和度指数降低的非阿尔奇现象.低含水饱和度阶段,岩石孔隙表面的水润湿性是RI-Sw曲线向下弯曲的主要原因;孔喉连通性差、非均质性强的部分水湿岩石的RI-Sw曲线可能向上弯曲;致密砂岩的进汞中值压力高,孔喉非均匀性强,水在岩石中不均匀地分布,含水饱和度大于(70%~90%)后,RI-Sw曲线出现平缓折线,该阶段的n值远小于2. 相似文献
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雷州半岛全新世高温期珊瑚生长所揭示的环境突变事件 总被引：23，自引：0，他引：23
通过对南海北部雷州半岛徐闻县灯楼角角孔珊瑚礁剖面(20°14.005′N, 109°55.200′E)的研究, 发现在全新世高温期存在至少9次高频率、大幅度的气候突然变冷事件, 将这一现象命名为“雷州事件”. 这一时期是雷州半岛珊瑚礁发育的适宜期, 至少可分为9个阶段, 每一阶段(即一次气候适宜期)的持续时间约20~50 a, 之后即在冬季突然出现一次低温和(或)相对低海平面事件, 导致角孔珊瑚大量死亡, 并出露遭受磨蚀, 形成间断面; 如此循环往复, 形成厚逾4 m的角孔珊瑚礁坪. 此段时间地壳分阶段性地下沉, 海平面上升. 该珊瑚礁剖面是研究中国南部热带地区全新世高温期年代际气候变化的宝贵的材料, 为全新世高温期的高频气候不稳定性演化模式提供了新的证据, 对传统的全新世大暖期的气候特征提供了新的认识. 相似文献
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在巢湖杭埠河流域中的古湖盆中心——三河圩区获取28.6 m长的湖相岩芯（SZK1507孔）,利用AMS14C测年技术建立可靠的地层年代序列,通过对SZK1507孔738 cm以上段湖相沉积物平均粒径、磁化率、总氮（TN）、总有机碳（TOC）及C/N的综合分析,高分辨率重建了巢湖杭埠河流域全新世以来的古环境演变过程.结果表明,本区域的环境变化过程可以分为4个阶段,阶段Ⅰ（约10050—9700 cal.a B.P.）与阶段Ⅲ（约9250—5300 cal.a B.P.）气候较为湿润,巢湖水位较高,平均粒径、磁化率值较低,TN、TOC、C/N也偏低;阶段Ⅱ（约9700—9250 cal.a B.P.）与阶段Ⅳ（约5300 cal.a B.P.以来）气候干燥,巢湖水量减少,水位降低,平均粒径、磁化率值、TN、TOC、C/N均较高.一些全球范围内显著发生的气候突变事件在SZK1507孔沉积记录中也有体现,如9.3、8.2和4.2 ka B.P.事件等.将巢湖杭埠河流域10000 cal.a B.P.以来的平均粒径、磁化率、TN、TOC、C/N沉积记录与全新世以来的北纬30°夏季太阳辐射量、太阳黑子数、火山喷发对大气中硫酸盐含量贡献率等进行对比,发现巢湖杭埠河流域全新世气候突变事件主要受控于北半球夏季太阳辐射量变化、太阳活动以及火山活动等因素,并与它们之间复杂的响应机制有关. 相似文献
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青藏高原中部0.2 ka来的环境变化 总被引：6，自引：0，他引：6
根据青藏高原那曲地区错鄂CE-1孔137Cs和210Pb测试结果, 建立了该孔年代序列. 根据沉积物岩性、碳酸盐含量、介形虫壳体Sr/Ca和Mg/Ca比值、碳酸盐同位素分析, 推测青藏高原中部近0.2 ka来环境变化经历了两大阶段, 即: 前0.1 ka, 气候干 旱, 沉积环境为沼泽环境; 后0.1 ka, 气温上升, 湿度增大, 为湖泊环境. 0.1 ka来的湿度变化存在0.02 ka的周期, 其中, 1920～1940和1960～1980年前后, 为两个较为湿润的时期, 1980年以来该地区变干. 相似文献
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The Zoige Basin is located in the eastern margin of the Qinghai-Xizang Plateau, in which two cores, RH and RM, have been drilled,
with the depths of 120 m and 310 m respectively. The former with the bottom age of 826 kaB. P. has been divided into 21 stages
according to the multi-proxy analysis, which could be basically compared with the oxygen isotope record of deep-sea core.
The palaeoclimatic and palaeoenvironmental process of the Zoigê Basin over the past 900 kaB. P. is reconstructed, and the
comparison of core RH with the Luochuan Loess record is made. 相似文献
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Youbin Sun Xulong Wang Qingsong Liu Steven C. Clemens 《Earth and Planetary Science Letters》2010,289(1-2):171-179
Rapid East Asian Monsoon oscillations recorded by Chinese loess are thought to be dynamically linked to north Atlantic climate. However, few efforts have been made to assess the effects of post-depositional processes (e.g., surface mixing and pedogenesis) on loess paleoclimatic records. Here a detailed optically stimulated luminescence dating of a thick loess sequence from the western Loess Plateau is presented, offering a reliable chronology for last glacial deposits. Magnetic susceptibility and mean grain size records from three loess–paleosol sequences along a northwest–southeast transect are investigated to evaluate impacts of post-depositional processes on these loess-based proxy records. Our results indicate that: (1) loess sequences developed within the flat tableland of the central and western Loess Plateau are nearly continuous during the last glaciation; and (2) post-depositional processes have distinct impacts on rapid monsoon signals recorded in loess sequences from different regions. In the central Loess Plateau, rapid monsoon signals have been attenuated to various degrees depending on the sedimentation rate and pedogenic intensity. In the northwestern Loess Plateau, however, due to high sedimentation rate and relatively weak pedogenesis, high-resolution grain size oscillations reliably record rapid monsoon changes and can be well correlated to rapid climate changes recorded in the Greenland ice core and Hulu cave stalagmite. 相似文献
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FU KaiDao FANG XiaoMin GAO JunPing HAN WenXia & LI LiLi MOE National Laboratory of Western China''''s Environmental Systems & College of Resource Environment Lanzhou University Lanzhou China Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2007,50(1):81-91
The widely distributed thick gravel deposits along the rim of the Tibetan Plateau have been long thought to be the product of rapid tectonic uplift of the plateau. However, this has been challenged by recent works that suggest these thick gravels may be the result of climate change. In this paper we carried out a detailed field measurement of gravel grain sizes from the Jiuquan and Gobi Gravel Beds in the top of the Laojunmiao section in the Jiuxi Basin in the northern margin of Qilian Mts. (northern Tibetan Plateau). The results suggest that the grain sizes of the Jiuquan and Gobi Gravel Beds over the last 0.8 Ma are characterized by nine coarse-fine cycles having strong 100-ka and 41-ka periodicities that correlate well with the loess-paleosol monsoon record and isotopic global climatic record from deep sea sediments as well as by a long trend of coarsening in gravel grain size. The coarse gravel layers were formed during the warm-humid interglaciations while the fine layers correspond to the cold-dry glaciations. Because the paleoclimate in NW China began to get dramatically drier after the mid-Pleistocene, we think the persistent coarsening of gravel grain size was most probably caused by the rapid uplift of the northern Tibetan Plateau, and that the orbital scale cyclic variations in gravel grain size were driven by orbital forcing factors that were superimposed on the tectonically-forced long-term coarsening trend in gravel size. These findings also shed new light on the interaction results of climate and tectonics in relation to the uplift of the Tibetan Plateau. 相似文献
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Xiuming Liu Zhisheng An Tim Rolph Xiaoke Qiang Paul Hesse Huayu Lu Jie Zhou Yanjun Cai 《中国科学D辑(英文版)》2001,44(7):635-651
The study on magnetic properties of the red clay indicates that the red clay and loesspaleosol sequence have a common magnetic
mineralogy, with magnetite, maghemite, hematite (and possibly goethite) contributing to the magnetic behavior. The red clay
magnetic susceptibility is also found to have a positive relation with extrafine superparamagnetic grains. This suggests that,
like the Quaternary loess-paleosols, an ultrafine ferrimagnetic component produced during pedogenesis in the red clay under
humid conditions also plays an important role in susceptibility enhancement in the soil units. This is supported by the correlation
between Rb/Sr ratio and magnetic susceptibility. This signifies that, like the above loess-paleosol sequence, the magnetic
susceptibility of the red clay can be used as a general proxy paleoclimatic indicator, although whether its susceptibility
in the red clay is comparable to pedogenesis intensity and requires further investigation. Magnetic susceptibility variation
in the red clay thus also provides an eolian/pedogenic record of paleoclimatic evolution. Study of the background susceptibility
indicates that, on average, the absolute scale of the paleoclimatic shift from red clay development to Quaternary loess deposition
is similar to the climatic shift from stage 5 (S1) to stage 2–4 (L1). This may suggest that during the Quaternary there is
an evident strengthening of the absolute wind intensity to bring more (about double) coarser and less weathered (non-SP fraction)
eolian magnetic input from the source regions to the Loess Plateau than during the Pliocene. The presence of eolian red clay
since 7.5 Ma BP in central-northern China implies an important environmental change from the underlying Cretaceous red sandstone.
The red clay development was closely related to global drying and climate cooling since the Cretaceous and closely associated
with the abrupt uplift of the Qinghai-Xizang Plateau at about that time. This uplift of the plateau intensified the East Asia
monsoon system and started red clay deposition. 相似文献
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Liu Xiuming AN Zhisheng Tim Rolph QIANG Xiaoke Paul Hesse Lu Huayu ZHOU Jie CAI Yanjun 《中国科学D辑(英文版)》2001,44(7)
The study on magnetic properties of the red clay indicates that the red clay and loess- paleosol sequence have a common magnetic mineralogy, with magnetite, maghemite, hematite (and possibly goethite) contributing to the magnetic behavior. The red clay magnetic susceptibility is also found to have a positive relation with extrafine superparamagnetic grains. This suggests that, like the Quaternary loess-paleosols, an ultrafine ferrimagnetic component produced during pe-dogenesis in the red clay under humid conditions also plays an important role in susceptibility enhancement in the soil units. This is supported by the correlation between Rb/Sr ratio and magnetic susceptibility. This signifies that, like the above loess-paleosol sequence, the magnetic susceptibility of the red clay can be used as a general proxy paleoclimatic indicator, although whether its susceptibility in the red clay is comparable to pedogenesis intensity and requires further investigation. Magnetic susceptibility variation in the red clay thus also provides an eo-lian/pedogenic record of paleoclimatic evolution. Study of the background susceptibility indicates that, on average, the absolute scale of the paleoclimatic shift from red clay development to Quaternary loess deposition is similar to the climatic shift from stage 5 (S1) to stage 2-4 (L1). This may suggest that during the Quaternary there is an evident strengthening of the absolute wind intensity to bring more (about double) coarser and less weathered (non-SP fraction) eolian magnetic input from the source regions to the Loess Plateau than during the Pliocene. The presence of eolian red clay since 7.5 Ma BP in central-northern China implies an important envi-ronmental change from the underlying Cretaceous red sandstone. The red clay development was closely related to global drying and climate cooling since the Cretaceous and closely associated with the abrupt uplift of the Qinghai-Xizang Plateau at about that time. This uplift of the plateau intensified the East Asia monsoon system and started red clay deposition. 相似文献
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China's Loess Plateau was formed under special conditions. The tectonic movement, topographical characteristics, and monsoon patterns combined to create a favourable environment for the accumulation of thick loessic deposits. The Loess Plateau itself is part of the ‘Monsoon Triangle’ of China, a region very susceptible to climatic changes. Throughout the Upper Pleistocene the palaeoenvironment on the Loess Plateau alternated from steppe, to deciduous forest and coniferous forest, in response to shifts in the atmospheric circulation. Three monsoon patterns appear to be indicated: (1) a full glacial monsoon pattern (18000–15000 yr BP) which induced a cold and dry climate favouring loess accumulation in steppe conditions; (2) an interglacial monsoon pattern (last interglacial and Holocene) in which a warm humid climate prevailed with deciduous forests, leaving palaeosols interbedded within the loess sequence; and (3) a transitional or interstadial monsoon pattern (50 000–23 000 yr BP) in which the climate was cold and humid in the Loess Plateau, encouraging the development of coniferous forest. 相似文献
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Mangshan loess on China’ s Central Plain and its response to tectonic movement and climate* 总被引：1，自引：0，他引：1
The Mangshan loess on China’s Central Plain, located on the transitional zone between the uplifting Loess Plateau and the
subsiding North China Plain, is a proximal sandy loess transported from the fanhead of alluvial fan in the lower reaches of
the Yellow River and has recorded the coupling effect of the tectonics and climate over the last 200 ka. An abrupt environmental
change indicated by the abrupt rise of deposit rate in the late penultimate glaciation, about 150 ka BP, took place; that
is, the Yellow River downcut and moved eastwards through the Sanmenxia Gorge and transported abundant materials from the Loess
Plateau to form paleosol S1 with a thickness of 15.7 m and loess L1 with a thickness of 77.3 m. The loess-paleosol sequence
at Mangshan has not only recorded detailed climate responses of this area to the East Asian monsoon, but also reflects the
tectonogenetic environmental effect caused by the trunk stream of the Yellow River cutting through Sanmenxia Gorge into sea.
Project supported by the National Natural Science Foundation of China (Grant No..49572132). 相似文献
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Correlation between high-resolution climate records from a Nanjing stalagmite and GRIP ice core during the last glaciation 总被引：1，自引：0，他引：1
A 400-mm-long stalagmite from Tangshan Cave, Nanjing has been analyzed by a high-precision TIMS-U series dating method and
also determined for oxygen and carbon stable isotopic compositions. The results provided a high-resolution paleoclimate record
for eastern China during a time interval (from 54 000 to 19 000 aBP) of the last glaciation. The continuous record of oxygen-18
variations in the stalagmite, indicating a precipitation history of the East Asian monsoon, shows not only signals of the
Heinrich events, but also the Dansgaard-Oeschger cycles which are first found in the last glacial climate record of the East
Asian monsoon area. Although the stalagmite-based climatic signals match well with the GRIP ice core record, some differences
between the two records can be recognized: (1) The last glacial climate changes in eastern China exhibited a long-term remarkably
cooling trend, superimposed on which were four successive Bond’s cycles illustrated by the δ18O curve. This strong cooling tendency may be an effect of the strong summer monsoon event during the MIS 3 over the Tibetan
Plateau. (2) There exist some phase differences of 1000–2000 years between the cooling events in the stalagmite-based climate
signal and the GRIP ice core record. Such differences should be further verified by calibrations of multiple dating methods 相似文献
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Evolution of the monsoon and dry climate in East Asia during late Cenozoic: A review 总被引：2，自引：0，他引：2
Climate in Eastern Asia is composed of monsoon climate in the east,arid and semi-arid climate in the north and west,and the cold and dry climate of Qinghai-Tibetan Plateau in the southwest.The underlying causes for the evolution of East Asian climate during late Cenozoic have long been investigated and debated,particularly with regards to the role played by the Qinghai-Tibetan Plateau uplift and the global cooling.In this paper,we reviewed major research developments in this area,and summarized the important results.Based on a synthesis of data,we propose that the Qinghai-Tibetan Plateau uplift alone cannot fully explain the formation of monsoon and arid climates in Eastern Asia during the past 22–25 Ma.Other factors such as the global ice volume and high-latitude temperature changes have also played a vital role.Moreover,atmospheric CO2changes may have modulated the monsoon and dry climate changes by affecting the location of the inter-tropical convergence zone(ITCZ),which controls the monsoon precipitation zone and the track of the East Asian winter monsoon during late Cenozoic.The integration of high-resolution geological record and numerical paleoclimate modeling could make new contributions to understanding the climate evolution and variation in eastern Asia in future studies.It could facilitate the investigation of the regional differences in East Asian environmental changes and the asynchronous nature between the uplift of Qinghai-Tibetan Plateau and their climatic effects.These would be the keys to understanding underlying driving forces for the evolution of the East Asian climate. 相似文献