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1.
运城盐湖是在盆地内部断块自北向南阶梯性沉降背景下形成的． ７．１～３．６ Ｍａ红 土堆积期湖泊范围较今为大,古季风已形成; ３．６ Ｍａ因青藏高原隆升的辐射效应,盆地 北部基底突然抬升,湖泊向南退缩; ２．６ Ｍａ构造变动河流进入盆地北部, ２．０～１．９ Ｍａ间 风成作用增强,开始黄土堆积．由于湖区断块自 １．８～１．０ Ｍａ始加速沉降,在天然水力 梯度下有充足的地下水补给,黄土在湖泊中的堆积速率小于湖泊构造沉降速率,故形 成了黄土高原上惟一的现代湖泊． ５．８～１．９ Ｍａ间湖泊地层中有 ４次大的季风强度变化记 录． 相似文献
2.
本文报道由蓝田、陕县、洛川、西峰、平凉、兰州及靖远等剖面获得的古地磁研究结果．主要结论为：１．中国黄土剖面记录了Ｂｒｕｎｈｅｓ正极性带与Ｍａｔｕｙａｍａ负极性带，Ｂｒｕｎｈｅｓ／Ｍａｔｕｙａｍａ极性转换过程位于第８层黄土（Ｌ８）．在段家坡黄土剖面该转换过程对应的地层厚度为０．３７５ｍ，持续时间约６０００ａ．转换过程由３次极性变化构成，每次经历的时间约为４００ａ．２．Ｊａｒａｍｉｌｌｏ正极性亚带（Ｊ）位于标志层Ｌ９至Ｌ１５之间，大约Ｓ１０－Ｓ１３位置．３．Ｏｌｄｕｖａｉ正极性亚带（Ｏ）对应的地层为Ｓ２７－Ｓ３３４．Ｒｅｕｎｉｏｎ正极性亚带（Ｒ）由两部分组成，在蓝田段家坡黄土剖面分别位于Ｌ３６和Ｓ３８５．Ｍａｔｕｙａｍａ负极性带与Ｇａｕｓｓ正极性带界限（Ｍ／Ｇａ）位于黄土和红色粘土交界处，中国黄土的底界年龄为２．４８Ｍａ左右．黄土与红色粘土为整合接触关系．６．黄土下伏的红色粘土记录了Ｇａｕｓｓ正极性带，Ｇｉｌｂｅｒｔ负极性带和古地磁年表编号５（Ｅｐｏｃｈ５）． 相似文献
3.
乌鲁木齐重力潮汐研究与震兆异常 总被引：1，自引：0，他引：1
利用Ｖｅｎｅｄｉｋｏｖ调和分析法分析了乌鲁木齐ＧＳ－１５－２１６重力仪１９９０～１９９３年的潮汐记录，得到了该地区的重力潮汐参量：δｏ１＝１．１５８２６±０．０００４９，Δｏ１＝０．１５±０．０２，δＭ２＝１．１６１０８±０．０００２２，ΔＭ２＝－０．３２±０．０１。主波Ｍ２和Ｏ１的结果与１９８０年中比协作时ＧＥＯ－０８４的观测结果一致，与Ｍｏｌｏｄｅｎｓｋｙ模型１值符合很好。不同时段得到的δ值和Δ值内符合精度高，表明乌鲁木齐地区重力场稳定，重力仪性能稳定，观测资料可用于检验地球模型、研究地球深部构造以及震源物理场。分析了和静东北两次５．２级地震前δＭ２值的短期前兆异常，确认从目前的重力潮汐观测中可以分辨出变化量大于１％的δ因子震兆异常． 相似文献
4.
更新过程在许多领域已有应用。本文检验确认四川省、云南省Ｍ＿ｓ≥５．５，６．０，６．５；川滇Ｍ＿ｓ≥６．０、６．５，７．０；西藏Ｍ＿ｓ≥６．０，６．５，６级地震（主震）间隔时间分别都可认为服从指数分布；同时其中大多又可认为服从对数正态分布，分别对未来１年、３年、５年给出地震发生的概率，并对以上时段内可能发震的次数作出估计，对西南地区未来几年内的地震活动强度给出简明的统计描述，应注意：年内四川省应有Ｍ＿ｓ≥５．５级地震发生，且震级可能大于或等于６．０级。 相似文献
5.
赣东北蛇绿混杂岩带中硅质岩的地球化学特征及构造意义 总被引：18，自引：0，他引：18
赣东北蛇绿混杂岩带中含晚古生代放射虫硅质岩的ＳｉＯ_２含量变化范围为 ７８．４０％～ ８９．２８％,Ｓｉ／Ａｌ＝ ６．３～２３,Ｓｉ／Ａｌ比和Ａｌ_２Ｏ_３呈很好的负相关关系,表明它们含有 较高比例的陆源泥质沉积物．硅质岩样品的Ａｌ_２Ｏ_３／（Ａｌ_２Ｏ_３＋Ｆｅ_２Ｏ_３）＝０．５１～０．９０,Ｃｅ／Ｃｅ~·＝ ０,９１～１．２２, Ｌａ_ｎ／Ｃｅ_ｎ＝ ０．７６～１．１１, Ｖ＜Ｍ２０μｇ／ｇ,Ｖ／Ｙ＜２．６,Ｔｉ／Ｖ＞４０,一致表明这些硅质 岩形成于与大陆地壳物质输入密切相关的大陆边缘环境,而与大洋盆地、洋中脊环境无 关．因此,这些晚古生代硅质岩既不属于～ １．０Ｇａ蛇绿岩套“三位一体”中的一部分,也 不支持晚古生代扬子和华夏两个块体之间存在深海大洋盆。 相似文献
6.
算法复杂性川滇地区11个地震带（区）地震预报的研究 总被引：1，自引：0，他引：1
以川滇地区１１个地震带（区）为对象，研究了将算法复杂性Ｃ（ｎ）用地地震预报的可能性。文中以１ａ为时间窗，０．５ａ为滑动步长，按２．５＜Ｍ＜３．５＜，３．５＜Ｍ＜４．５和Ｍ＞４．５分成３档，将各地震带（区）地震序列转换成由３种符号组成的字符串，从而计算各地震带（区）算法复杂性Ｃ（ｎ）随时间变化曲线，规定了预报和预报规则，总体上取得了略高于随机瞎报的预报效果，显示了效算法复性用于地震预报研究有一定的前 相似文献
7.
黄土高原中部的陕西泾阳、旬邑黄土剖面具有高分辨率气候记录,记录了130ka 以来的气候波动,一些细微的气候波动也被记录下来。位于大陆的黄土磁化率气候记录可以与南极冰芯气候记录对比。结果表明:Lorius 与 Jouzel 等将冰芯同位素曲线划分为 A、B、C、D、E、F、G、H 冷暖阶段,可与黄土磁化率气候曲线划分的1、2、3、4、（5、6、7）、8,9、10冷暖阶段对比。其中冰芯记录所反映的 A、C、E、G（或黄土记录反映的1、3、5、6、7、9）为暖阶段:B、D、F、H（2、4、8、10）为冷阶段。总之,黄土磁化率记录曲线与冰芯气候记录曲线的形态极为相似,指示了黄土高原地区的大陆气候变化与极地气候变化同受全球变化的影响。这证明了极地冰量变化与东亚大陆冬、夏季风强弱变化,是全球气候变化在极地与大陆的两种表现形式。黄土记录的气候变化时间滞后于冰芯记录,可能暗示着大陆气候变化滞后于极地气候变化。 相似文献
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9.
本文使用１９８６年至１９９１年期间沈阳遥测地震台网记录到的１４５３次地震的持续时间资料（２．０≤Ｍ＿Ｌ≤６．１级、５ｋｍ＜△＜１０００ｋｍ），求得了辽宁省及其邻近地区多台多幅度持时震级的经验公式，结果表明，这种震级误差小，应用范围为Ｍ＿Ｌ≤６．０级，解决了限幅地震无法计算震级的难题． 相似文献
10.
黔南洞穴石笋古气候变化记录及终止点Ⅱ的确定 总被引：17，自引：0，他引：17
通过对黔南地区三个大型石笋进行TIMS-U系测年和碳、氧稳定同位素分析, 获得了163~113.8 ka高分辨率的古气候记录. 石笋氧同位素的记录曲线揭示, 在万、千年尺度上, 研究区冰期的降温和间冰期回暖的波动特征, 可与冰芯、湖泊、黄土、深海岩芯记录相比较, 其记录的气候波动与全球具有一致性, 显示与北极地区存在着古气候的遥相关. 研究表明, 石笋记录所反映出的古季风环流变化的直接动力可能来自全球冰量变化, 即主要受北半球日照辐射强度、北大西洋冰漂碎屑带的扩张以及低纬度太平洋海表面温度变化等因素的影响. 根据d18O值进行了温度计算, 获得了研究区冰期(相当于深海同位素6阶段的中后期, 平均为8.1℃, 最低为－1.43~0.65℃)与间冰期(相当于深海同位素5E段, 平均为18.24℃)之间的年均温差达10℃左右(与冰芯记录的温度变化幅度大约为10℃, 大体相一致), 显示东亚夏季风与冬季风环流强度具有显著的差异. 通过对3个石笋的精确测年, 确定倒数第2次冰期的终止点Ⅱ的年龄为129.28±1.1 ka, 这一界线的年龄代表了末次间冰期开始的年代, 即是中更新世与晚更新世的分界年龄, 与冰芯和深海SPECMAP氧同位素曲线上末次间冰期的起始年龄相一致. 相似文献
11.
The evolution and driving mechanism of the Asian winter monsoon system are of great importance to understanding the present-day climate. Through high-resolution particle size analysis of the oldest loess-red clay sequence known so far (with a basal age of about 8 Ma) and comparison of the results with oxygen isotope curves from North Atlantic marine sediments, 4 stages of the evolution of the Asian winter monsoon were clearly demonstrated. During the first stage, between about 8.1 and 4.3 Ma, there was no relation between Asian winter monsoon and Northern Hemisphere ice volume and high latitude climate inferred from marine sediments. A weak relation developed during the second stage, about 4.3 to 3.5 Ma. During the third stage (3.5 to 2.6 Ma) an Asian winter monsoon system similar to the present formed, initiating a stronger relation between the winter monsoon and Northern Hemisphere ice volume and high latitude climate. In the final stage (2.6 to 0 Ma) the present Asian winter monsoon system was fortified and stabilized and changes in the winter monsoon system were almost in phase with Northern Hemisphere ice volume and climate. The staggered uplift of Tibetan Plateau at ≈8, 3.6, 2.6 Ma and later might be the driving force for the evolution of the Asian winter monsoon.
相似文献12.
The results of a high-resolution mineral magnetic study combined with major element geochemistry analysis, oxygen isotopes and 14C AMS stratigraphy are reported for deep-sea gravity cores MD77-169 and MD77-180 located in the Andaman Sea and the Bay of Bengal, respectively. Core MD77-169 covers the last 280 kyr and core MD77-180 covers the last 160 kyr. In both cores, rock magnetic parameters indicate that the magnetic assemblage is dominated by pseudo-single domain titanomagnetite grains, with grain-size variations following a strong 23 kyr periodicity. Smaller magnetic grain sizes are observed during periods characterized by a strong summer monsoon. In addition, in core MD77-180, we observe a correlation between magnetic grain size and a chemical index of alteration. This suggests that these magnetic grain-size changes are related to chemical weathering driven by summer monsoon rainfall. A comparison of the GISP2 ice core isotopic record and the magnetic grain-size record of the Bay of Bengal shows that rapid temperature variations documented in the ice core (Dansgaard–Oeschger cycles and Heinrich events), during the last glacial period are also present in the magnetic grain-size record. Heinrich events and cold stadial events are characterized by relatively large magnetic grain sizes. Furthermore, Heinrich events are characterized by lower values of the chemical index of alteration implying a lower degree of chemical weathering related to significantly drier conditions on the continent. We suggest that rapid cold events of the North Atlantic (Heinrich events) during the last glacial stages are characterized by a weaker summer monsoon rainfall over the Himalaya via an atmospheric teleconnection. 相似文献
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14.
TIAN Jun WANG Pinxian CHENG Xinrong WANG Rujian & SUN Xiangjun . State Key Laboratory of Marine Geology Tongji University Shanghai China . Institute of Geology Geophysics Chinese Academy of Sciences Beijing China . Institute of Botany Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2005,48(10)
The variations of the Earth’s geometry (ETP) pre-dominate climate changes such as monsoon on the Earth[1], serving as its external forcing. The loess/ paleosol sequence in Central China provides a good record of terrestrial deposition to study the evolution of the east Asian monsoon[2―4]. However, the deep sea deposition, due to its high resolution dating and abun-dant climate proxies, should be able to provide more climatic information in the geological time, such as the forcing mechanis… 相似文献
15.
TIAN Jun 《中国科学:地球科学(英文版)》2013,56(12):2160-2172
The Milankovi theory stresses that the summer insolation in the high northern latitudes that is dominated by the precession cycle controls the glacial/interglacial cycles in global climate change.If the climate system responds linearly to the external insolation forcing,the precession cycle of 23 or 19 ka should dominate the variations in the climatic proxy records.I performed spectral and evolutive cross spectral analyses on the high resolution benthic 18O and 13C records from the South China Sea and the North Atlantic,the proxies of global ice volume and ocean carbon reservoir respectively.I found that the obliquity instead of the eccentricity or the precession is the most marked cycle in the global ice volume and ocean carbon reservoir variations over the past 5 Ma.The analysis further reveals that only at the obliquity band instead of the eccentricity or the precession band does the global ice volume and ocean carbon reservoir display consistently high coherency and stable phase relationship over the past 5 Ma.The consistently positive or near-zero phases of the benthic 18O relative to the benthic13C at the obliquity band suggest that the global carbon cycle is involved in the polar ice sheet growth as an important internal feedback,not a determinative driving factor.The obliquity instead of the precession or the eccentricity takes the dominant role of driving the global climate change during the Pliocene and Pleistocene. 相似文献
16.
Jan-Berend W. STUUT 《中国科学D辑(英文版)》2007,50(10):1536-1547
273 samples from Ocean Drilling Program (ODP) Site 1146 in the northern South China Sea (SCS) were analyzed for grain-size distributions using grain-size class vs. standard deviation method and end-member modeling algorithm (EMMA) in order to investigate the evolution of the East Asian monsoon since about 20 Ma. 10–19 μm/1.3–2.4 μm, the ratio of two grain-size populations with the highest variability through time was used to indicate East Asian winter monsoon intensity relative to summer monsoon. The mass accumulation rate of the coarsest end member EM1 (eolian), resulting from EMMA, can be used as a proxy of winter monsoon strength and Asian inland aridity, and the ratio of EM1/(EM2 EM3) as a proxy of winter monsoon intensity relative to summer monsoon. The combined proxies show that a profound enhancement of East Asian winter monsoon strength and winter monsoon intensity relative to summer monsoon occurred at about 8 Ma, and it is possible that the summer monsoon simultaneously intensified with winter monsoon at 3 Ma. Our results are well consistent with the previous studies in loess, eolian deposion in the Pacifc, radiolarians and planktonic foraminifera in the SCS. The phased uplift of the Himalaya-Tibetan Plateau may have played a significant role in strengthening the Asian monsoon at 8 Ma and 3 Ma. 相似文献
17.
Magnetostratigraphy and palaeoclimate of Red Clay sequences from Chinese Loess Plateau 总被引：5，自引：0，他引：5
Two Red Clay profiles near Xi’an and Xifeng were investigated in an attempt to determine magnetostratigraphic and palaeoclimatic
records. The results show that aeolian dust accumulation and the related East Asia palaeomonsoon system had begun by 6.5 Ma,
and it is deduced that the Tibetan Plateau had reached a significant elevation at that time. The late Tertiary palaeoclimatic
history of the Red Clay as reflected by magnetic susceptibility is reconstructed during the period of 6.5–2.5 Ma. Stepwise
increase in susceptibility of aeolian dust accumulation appears to have a close correlation to the uplift processes of the
Tibetan Plateau. The remarkable increase of aeolian dust accumulation at 3.2 Ma appears to be due to the influence of global
ice volume on the East Asia monsoon. Palaeomonsoon variation during the late Tertiary as recorded in the Red Clay sequences
from the Chinese Loess Plateau can be regarded as the product of a number of interacting factors, such as uplift of the Tibetan
Plateau, solar radiation, global ice volume, etc.
Project supported by the National Natural Science Foundation of China and the Foundation of Xi’an Laboratory of Loess and
Quaternary Geology, Chinese Academy of Sciences. 相似文献
18.
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
19.
Zhisheng An Sumin Wang Xihao Wu Mingyang Chen Donghuai Sun Xiuming Liu Fubao Wang Li Li Youbin Sun Weijian Zhou Jie Zhou Xiaodong Liu Huayu Lu Yunxiang Zhang Guangrong Dong Xiaoke Qiang 《中国科学D辑(英文版)》1999,42(3):258-271
On the basis of a newly-constructed record of magnetic susceptibility (SUS) and the depositional rate change of eolian loess-red
clay sequences in the last 7.2 Ma BP from the hea Plateau, together with a cornperison of a record of °18O values from the equatorial East Pacific Ocean and eolian Quartz flux variations fmm the North Pacific Ocean, the evolutiomuy
process of the Late Cenozoic Great Glaciation in the Northern Hemisphere can be divided into three stages: the arrival stage
around 7.2–3.4 Ma BP, the initial stage at about 3.4—2.6 Ma BP, and the Great Ice Age since 2.6 Ma BP. The evolution of the
East Asian monsoon is characterized by paid winter and summer monsoons, and it is basically composed of the initial stage
of weak winter and summer monsoons, the transitional stage of simultaneous increase in intensity of winter and summer monsoons,
and the prevailing stage of strong winter and week summer monsoons, or weak winter and strong summer monsoons. The Late Cenowic
global tectonic uplift, paaicdarly the Qinghai-Xizang Plateau uplift and the associated CO2 concentration variation, controls the dng processes of the onset of Great Glaciation and the long-term changes of East Asian
monsoom climate in the Northern Hemisphere to a large extent. The accelerating uplift of the Qinghai-Xizang Plateau between
3.4 and 2.6 Ma BP provided an important driving force to global climiatic change.
Project supported by the foundation of Chinese Academy of Sciences (Grant No. KZ951-A1-402), the State Science and Technology
Committee (Grant No. 95-pre-40)and the Chinese Nature Science Foundation (Grant No. 49672140) 相似文献
20.
WEN Lingjuan LU Huayu & QIANG Xiaoke State Key Laboratory of Loess Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi’an China 《中国科学D辑(英文版)》2005,48(9):1452-1462
In recent years, the Red Clay deposits underlying Quaternary loess on the Chinese Loess Plateau (north China) have attracted more attention because they show a direct and continuous record of past atmos- pheric circulation and palaeoclimatic change. Investiga- tions on Red Clay deposits through multidisciplinary methods have demonstrated an aeolian origin for the Red Clay, like the overlying Quaternary loess. The Red Clay formed during the Miocene and Pliocene[1―13]. However, the type o… 相似文献