2000 Vol. 6, No. 4

Display Method:
ANCIENT DRAINAGE SYSTEM OF THE YELLOW RIVER ON NORTH CHINA PLAIN
WU Chen, XU Qing-hai, YANG Xiao-lan
2000, 6(4): 1-9.
Abstract (244) PDF (339KB)(6)
Abstract:
A study of several NE_SW-trending sand belts buried 20~35m underground in North China Plain from geophysical and drilling and experimental data has been carried out for a rational exploitation and utilization of ground water. These sand belts are of alluvial facies,representing ancient stream channels of the Yellow River. From their distributions,heavy mineral associations,and scale,and fossil contents and 14C dating they are known to have formed during the period spanning Late lce Age to Early Holocene. They cut into the interglacial brown clay and indicates that the Yellow River might have passed through the Sanmen Gorge in the Late lce Age and left some traces of Bohai Sea on the continental shelf.
S TSCHUDI, S IVY-OCHS, PW KUBIK, J SCHFER, C SCHLCHTER, Z ZHAO, X WU
2000, 6(4): 10-10.
Abstract (124) PDF (17KB)(5)
Abstract:
PALYNOEVENTS SINCE LATE CENOZOIC IN WEIHE VALLEY AND CLIMATE CHANGES
TONG Guo-bang, WU Xi-hao, CHEN Yun, ZHANG Jun-pai, WANG Shu-bing, LI Yue-cong, CAO Jia-dong
2000, 6(4): 11-18.
Abstract (162) PDF (338KB)(23)
Abstract:
Weihe valley is one of the areas where the study on late Cenozoic palynology began very early,involving more than twenty sections. By comparing the temporal and spatial distribution of the sporollon assemblages coupled with paleo-geomagnetism dating,we have ten areal zones. Since 3.5MaBP,the palynoflora were found to have evolved go through five stages,i.e.broad-leaf trees stage,conifer trees stage,woody grassland and grassland stage,woody grassland and desert grassland stage,grassland stage,and lastly woody grassland and grassland. These stages mark the megaevolution of the surface's environments beginning respectively from 2.5MaBP,2.0MaBP,1.4/1.6MaBP,and 0.8MaBP.
THE LOESS STRATIGRAPHY IN SANMENXIA AREA
ZHAO Zhi-zhong, WU Xi-hao, JIANG Fu-chu, XIAO Hua-guo, WANG Shu-bing, TIAN Guo-qiang, LIU Ke, YIN Wei-de, XUE Bing, WANG Su-min
2000, 6(4): 19-26,66.
Abstract (339) PDF (352KB)(13)
Abstract:
The Caocun loess profile in Zhangbian township located at the southeast margin of the Loess Plateau is typical of the Sanmenxia area. In the profile there occurs a loess-paleosol sequence from L1 to L33 145m thick,underlain by a red clay bed. The B/M boundary was recorded at the bottom of L7,the J magnetic event at S11 to S12,the O magnetic event at L23 to L26,and the M/G boundary at the bottom of L33 near the red clay. The magnetic susceptibility of the loess deposits,as well as the carbonates and macrograined components contained all indicate that there have been many periodic monsoon changes totalling 13 cold events,with each lasting more than 40000 years. A high-resolution chronostratigraphy of the profile has been established by an age model according to grains. There exists a clear correlation between the records of paleomonsoon in the Caocun loess succession and SPECMAP from 3×105-year BP to the present.
TWO LOESS PROFILES IN PINGLU,SHANXI AND CORRESPONDING PALEOCLIMATIC RECONSTRUCTION
WANG Shu-bing, WU Xi-hao, JIANG Fu-chu, TIAN Guo-qiang, LIU Ke
2000, 6(4): 27-36.
Abstract (184) PDF (341KB)(7)
Abstract:
In this paper,two loess profiles located in Pinglu,Shanxi north of Sanmenxia gorge of the Yellow River,have been studied. The magnetic susceptibility curves of Miaoxia and Yangwa profiles show that the susceptibility values of S6 and S1 are higher than that deposited in the corresponding period in the Loess Plateau,while the values of S5~S2 and L7~L2 are somewhat lower,being close to the susceptibility value of L9 in the interior of the Loess Plateau. The thickness of strata of S5~L5 is greater than that of the Loess Plateau. A comparison with the curves of the magnetic susceptibility,δ18O in DSDP607 and V30-97,and mid-month insolation 65°N for July of Caocun profile,shows that the climatic changes indicated by both Miaoxia and Yangwa profiles are close to the interior of the Loess Plateau at the scale of 105 a. This fact may reflect its consistency with the global glacial cycle resulting from the variation in solar radiation controlled by variation in some elements of earth's orbit. But there is no simple correspondence between them as shown by the greater thicknesses of deposits and relatively lower susceptibility values. It may be caused by (1) different rate of dust accumulation,(2) water erosion,(3) different source materials and (4) variation in local soil forming conditions.
DEBRIS FLOW RISK ZONATION IN ZHAOTONG COUNTY OF YUNNAN PROVINCE,CHINA
LIU Xi-lin
2000, 6(4): 37-42.
Abstract (189) PDF (231KB)(13)
Abstract:
This paper discusses the principales of debris flow risk zonation,i.e. similarity,integrity,factor synthesis and factor dominancy.Regional grade of debris flow risk is chosen as the synthetic index for the risk zonation and the method for risk grading is also given here. Based on the grades,five zones,negligible risk zone,low risk zone,medium risk zone,high risk zone and very high risk zone are differentiated. Taking Zhaotong county of Yunnan province as an example,the paper describes the methods of debris flow risk zonation and achieves the debris flow risk map for Zhaotong county.
THE GEOCHEMICAL ELEMENT CHARACTERISTICS AND PALEOSEDIMENTARY ENVIRONMENT OF THE QUATERNARY DEPOSITS IN YINCHUAN BASIN
LIU Ping-gui, FAN Shu-xian, LI Xue-ju
2000, 6(4): 43-50,94.
Abstract (155) PDF (362KB)(8)
Abstract:
From an analysis of the contents of geochemical elements and their vertical distribution of the core samples from Yinchuan Basin and the stratigraphic lithologies a zonation of the geochemical elements has been determined. Combining this with spare-pollen data,a discussion of the paleoclimate and paleoenvironment and their evoluation in the basin. Since the middle and late Quaternary has been maded.
FLEXURE OR UNDERPLATING DISCUSSION ON THE FORMATION OF WANGANUI BASIN,NEW ZEALAND
LIU Xi-lin, John Townend
2000, 6(4): 51-57.
Abstract (221) PDF (253KB)(5)
Abstract:
Wanganui Basin,located between North and South Island of New Zealand,is characterized by thick crust and low heat flow. Previous study attributed its formation to bending of thin plate under vertical component of drag force acted by the subducting slab on the overriding crust. The present study shows that the flexure hypothesis of thin plate is not self consistent. We propose that the process of underplating is responsible for both the sinking of Wanganui Basin and the rising of Axial Range east of the basin. This model can explain the synchronism of sinking of basin and rising of mountain,the southwest migration of sedimentation center of the basin and uplift of the once subsided northeastern basin,and the low heat flow observed in the basin.
NATURE OF THE QIANGTANG BASIN AND ITS TECTONIC EVOLUTION
HUANG Ji-jun
2000, 6(4): 58-66.
Abstract (160) PDF (326KB)(8)
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The Qiangtang Basin is a huge sedimentary basin which is situated between the Banggonghu Lake-Nujiang River suture zone and the Xijinwulan-Jinshajiang River suture zone.Its formation and evolution was controlled by the dynamics of the Tethys tectonic belt.An analysis of the sedimentary sequence and of the essential mineral components,chemical components and trace elements of the clastic rocks as well as the chemical components of igneous rocks in the Qiangtang Basin show that the basin resulted from a superimposition of different types of tectonic basins in different periods i.e.a craton riftbasin in the Late Paleozoic,a foreland basin in the Mesozoic and an intermountain graben basin in the Cenozoic.
DEFORMATION OF ARCHAEAN WULASHAN GROUP IN GUYANG REGION OF INNER MONGOLIA
LI Long, GAO De-zhen, ZHANG Wei-jie, GENG Ming-shan, WANG Tao
2000, 6(4): 67-72.
Abstract (164) PDF (207KB)(5)
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There have existed different views on the metamophism-deformation of the Wulashan Group. It is pointed in this paper that the late Archaean Wulashan Group has experienced two major deformation events on the basis of recent results obtained from 3 sheets of 1:50000 geological mapping and other regional studies since 90's. The first deformation event is characterized by solid flow fold and high temperature ductile shear zone resulting from nearly horizontal shearing by extension. The metamorphism is of high amphibolite granulite facies. The deformation took place at the end of Archaean. The second deformation even is characterized by shallow tight homoclinal similar fold-main fold and low temperature ductile shear zone arising from post-crustal uplifting compression. The event occurred in the early Proterozoic.
RELATIONSHIP BETWEEN NEN-TRENDING ACTIVE STRIKE-SLIP FAULTS AND EARTHQUAKE HOT SPRING DISTRIBUTION IN EASTERN HUNAN AND WESTERN JIANGXI,CHINA
LI Xian-fu, YAN Tong-zhen, FU Zhao-ren
2000, 6(4): 73-78.
Abstract (199) PDF (224KB)(11)
Abstract:
The relationship between the active NEN-trending strike-slip faults and the distribution of earthquakes hot springs in the area of eastern Hunan and western Jiangxi of China has been studied. The results show that:(1) the earthquakes and hot springs are mostly located in the three main NEN-trending strike-slip fault zones and associated P,R' faults;(2) The basic structural patterns in the region of high temperature hot springs or strong earthquake epicentres comprise left-lateral en echelon faults and pull-apart basins;(3) the structural layering of the continental crust is thought to be one of the important factors that influence the seismicity in this area.
A STUDY OF ORE-CONTROLLING STRUCTURES ON GOLD AND ANTIMONG IN THE MID-XUEFENG MOUNTAIN, HUNAN PROVINCE
ZHU Da-gang, MENG Xian-gang, LUO Xue-quan, WEI Dao-fang, FENG Xiang-yang, SHAO Zhao-gang, ZHAO Jian-guang, LIU Xing-qin, WANG Jian-ping, WANG Zhi-shun
2000, 6(4): 79-87.
Abstract (170) PDF (313KB)(12)
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A study of the fabrics of ductile-brittle rock deformation during the mineralization epoch by X-ray diffraction method is made. The aim is to find out the structural control of the gold and antimony in the Mid-Xuefeng Mountain so as to predict its distribution and enrichment. The results show that the NE-trending compresso-shear structural belt may serve as the passage way for the SE-NW ore fluid flow under a stress regime with the greatest principal stress trending NW-SE, and the NW-SE trending tenso-shear structural belt associated with and derived from the NE-SW-striking structures as the host structure and described.
QUANTITATIVE EVALUATION ON GEOLOGICAL STRUCTURE COMPLEXITY OF CUIJIAZHAI MINE,HEBEI PROVINCE
CAO Dai-yong, MU Xuan-she
2000, 6(4): 88-94.
Abstract (186) PDF (230KB)(5)
Abstract:
The quantitative evaluation on geological structure complexity is one of the hotspots in the research of mining geology,the key techniques of which include selecting proper assessment indexes and assessment models.On the basis of analysis of geological setting and procession of exploration data,5 continuous deformation parameters and 5 discontinuous deformation parameters are taken as indexes for the evaluation on geological structure complexity.The comprehensive statistical assessment model and comprehensive fuzzy assessment model are both adapted for the quantitative evaluation on geological structure complexity of Cuijiazhai mine,Hebei Province.A comparative study shows that both can be used for quantitative evaluation on geological structure complexity,with the fuzzy model being more plausible.