中国黄土与红色粘土记录的地磁极性界限及地质意义   总被引：13，自引：0，他引：13       下载免费PDF全文

岳乐平 《地球物理学报》1995,38(3):311-320

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   

碳硅泥岩型铀矿床的成矿作用与红层（盆）的关系   总被引：2，自引：0，他引：2  

连立祥 《华东地质学院学报》1994,17(1):68-75

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红粘土的微结构及其概化模型   总被引：9，自引：0，他引：9  

廖义玲  余培厚 《工程地质学报》1994,2(1):27-37

本文论述红粘土的物质组成和微结构特征,在此基础上提出了红粘土微结构的概化模型,并根据这种模型对红粘土的工程特性进行了探讨。  相似文献   

Magnetostratigraphy and palaeoclimate of Red Clay sequences from Chinese Loess Plateau   总被引：5，自引：0，他引：5  

Donghuai Sun  Dongsheng Liu  Mingyang Chen  Zhisheng An  Shaw John 《中国科学D辑(英文版)》1997,40(4):337-343

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   

Seismicity re-evaluation of the northern Red Sea     

A. Gharib  A. Necioglu  A. Al-Amri 《Geophysical Journal International》1997,130(2):335-348

The Aqaba subnetwork of five vertical short-period stations of the seismological observatory of King Saud University was installed in late 1986 along the eastern side of the Gulf of Aqaba, northern Red Sea. During the first six years (1986 August to 1992 July) of the subnetwork operation, 400 microearthquakes were detected. Of these, 93 events were recorded by most of the subnet stations and were located. Their epicentres lie in the northern part of the Red Sea between latitudes 25.5 N and 27.5 N and longitudes 33.5 E and 36 E along the axial depression of the Red Sea where the large intrusions (deeps) are located. Magnitudes of the locatable events ranged from 2.1 to 4.8. Two intensive swarms of about 200 microearthquakes occurred in February and June of 1992. The February swarm is the first intensive sequence observed in the surveying area since the establishment of the KSU network. Frequency-magnitude analysis of the recorded events for the period 1986-1992 yielded 3.543 for a and 0.658 for b . These relatively higher b values (0.658) are a good indication of the crustal heterogeneity under the spreading zone of the northern Red Sea. USGS and KSU data together show 3.41 for a and 0.49 for b . This study, together with historical data, confirms that the area is very seismically active and that the activity is mainly of swarm type, and may be attributed to the subsurface magmatic activity and spreading centres that are usually associated with strike-slip and normal faulting, respectively.  相似文献   

青藏高原东北部古喀斯特过程与环境   总被引：6，自引：0，他引：6  

崔之久  陈怀录 《地理学报》1996,51(5):408-417,T001

本文介绍了青藏高原东北部地区的古喀斯特现象，并对相关沉积进行了化学成、粘土矿物的Ｘ－射线衍射以及石英砂表面结构等气候代用指标的分析。分析结果一致，指示了温暖湿润的亚热带气候条件。重结晶方解石的裂变径迹测年结果表明，该地区古喀斯特发育于中中新世。  相似文献   

THE MEASUREMENT ON VISCOSITY Q VALUE USINGP-WAVE OF LOCAL EARTHQUAKESIN WESTERN YUNNAN PROVINCE 滇西地区近震(?)波的粘性 Q_α值测定     

杜志俊 《地震研究》1989,(1)

本文使用云南滇西地区、红河断裂带北段1984——1985年由PDR-2数字事件记录仪记录到的84张地震记录图,按文献〔4〕中所述的理论和方法,用直达(?)波资料计算了该区的分区粘性多Q_α值,初步结论是:整个场区内介质粘弹性可用非线性体去近似模拟。Q_α值分布情况为:由云龙、洱源、漾濞三点所成的三角区内,其值约为50±30左右较低,而沿弥渡向北,经下关至剑川所示的整个断裂带上所测Q_α值较高,约在160±30左右。反映了明显的构造差异性。  相似文献   

EUTROPHICATION AND RED TIDES AS CONSEQUENCES OF ECONOMIC DEVELOPMENT   总被引：4，自引：0，他引：4  

Zhao-Yin WANG  Yongsheng WU  and Guangqian WANG Prof.  Dept. of Hydraulic Engineering  Tsinghua University & International Research  Training Center on Erosion  Sedimentation  Beijing  China  Email: zywang@tsinghua.edu.cn or zywang@sun 《国际泥沙研究》2001,16(4)

1 mTRoorcnoxThe EnvirDment AgenCy of UK (l997) defins eUtIDPhication as "the enrichInnt of waters byinorgedc plant nUtrientS that result in the simulation of an mp Of syInPtOInati changes. These includethe inCrased PrOduCtiOn Of aigae or othe aquatic PlantS, affeChng the quallty of the water and distUIbingthe balance Of orpedsms Present within it. Such changes Inay be undesirable and intetw with wateuses." Sndth et al. (l999) indicated tha eopation of waters is mainly caused by h…  相似文献   

桂林地区红土砾石层的工程地质特征及其应用   总被引：1，自引：1，他引：1  

牟春梅 《工程地质学报》2003,11(2):186-188

桂林地区的红土砾石层以其独特的工程地质特征引起了许多中外学者的注意, 对它的成因至今还存在争议。本文主要讨论红土砾石层的工程应用, 即不仅可作为一般低层建筑物的天然持力层, 而且可以作为沟、塘等低洼地带的回填土料 ;而且厚度较大的红土砾石层坚硬部分可作为桩端持力层。  相似文献   

Enhanced red fluorescence emission in the oxygen minimum zone of the Arabian Sea     

Wiebke Breves  Rüdiger Heuermann  Rainer Reuter 《Ocean Dynamics》2003,53(2):86-97

 Depth profiles of fluorescence at several excitation and emission wavelengths were measured along with CTD data during the cruise So119 of RV Sonne in the Arabian Sea from 12 May to 10 June 1997. In addition to chlorophyll fluorescence from phytoplankton in the near-surface layer, the profiles in the oxygen minimum region well below the euphotic zone show enhanced red fluorescence. Red fluorescence intensity is inversely related to the oxygen concentration in intermediate and deep waters. A relationship to characteristic water masses of the region cannot be found in the data, and this holds also with chemical data such as DOC. Absorbance spectra of water samples taken in the oxygen minimum zone show an absorption band at 420 nm wavelength with about 50 nm bandwidth, much weaker than gelbstoff absorbance in the same wavelength range. The absorption band remains stable after sample filtration with 0.45 μm glass fibre filters. Hence, the size of the absorbing matter is in the range of dissolved molecules or particles much smaller than 1 μm. Fluorescence spectra of unfiltered samples with 420 nm excitation show a weak emission band at 600 nm and a more pronounced one at 660 nm wavelength. The trailing edge of the 660 nm band falls into the range of chlorophyll emission, thus giving rise to the observed depth profiles of red fluorescence in the oxygen minimum zone. Red fluorescence measured on samples remain stable during a few hours after sampling even in the presence of oxygen. It is not detectable after several weeks of sample storage in the dark and cannot be reproduced even after depletion of dissolved oxygen. Received: 22 May 2002 / Accepted: 18 February 2003 Responsible Editor: Andreas Oschlies Acknowledgements. This work was supported by a grant from the Federal Minister of Education and Technology, Bonn, within the frame work of the JGOFS Arabian Sea program. We are grateful to the captain and the crew of RV Sonne for their support. We are indebted to Mrs. Kirsten Neumann from the Institute of Marine Chemistry and Biogeochemistry of the University of Hamburg for providing the oxygen data, and to Mr. Nikolai Delling from the same institute for making the DOC and chlorophyll data available to us.  相似文献