2005 Vol. 11, No. 4

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THE AGE OF THE YELLOW RIVER PASSING THROUGH THE SANMEN GORGE
JIANG Fu-chu, FU Jian-li, WANG Shu-bing, ZHAO Zhi-zhong
2005, 11(4): 293-301.
Abstract (219) PDF (313KB)(12)
Abstract:
The development of the Yellow River was one of the major events of Late Cenozoic tectonogeomorphologic and environmental evolution in East Asia.Only by passing through the Sanmen Gorge between Shanxi and Henan and flowing into the sea,was the main stream of the Yellow River formed eventually.Therefore,the Sanmen Gorge is one of the crucial sites for the study and discussion of the formation and evolution of the Yellow River.On the basis of the important events of environmental sudden change revealed by the extinction of the Sanmen paleolake and abrupt change in sedimentation rate of the late Pleistocene loess at Mangshan,it is inferred that the Yellow River passed through the Sanmen Gorge and flowed into the sea about 150 kaB.P.,and then the modern Yellow River drainage system formed eventually.
ON AGE OF THE YUANMOU MAN
QIAN Fang
2005, 11(4): 302-310.
Abstract (270) PDF (378KB)(6)
Abstract:
In the past 40 years,the author has further studied the age,living environment and culture of the Yuanmou Man.The study of Yuanmou Man's age has been carried out by:(1) the paleomagnetostratigraphic method,fission-track dating(FTD),electron spin resonance(ESR) and amino acid analysis,(2) the Yuanmou fauna,(3) the geomorphology in the Yuanmou area,(4) neotectonic movement,(5) the Quaternary stratigraphy of the Yuanmou basin,and(6) the teeth and tibia of the Yuanmou Man.The study at last comes to the conclusion that Yuanmou Man's age is early Pleistocene,~170 MaB.P..
QUATERNARY GLACIAL REMNANTS IN THE ZANDA BASIN AND ITS PERIPHERAL HIGH MOUNTAIN AREAS, TIBET, AND DIVISION AND CORRELATION OF GLACIAL STAGES
ZHU Da-gang, MENG Xian-gang, SHAO Zhao-gang, YANG Chao-bin, HAN Jian-en, YU Jia, MENG Qing-wei, Lü Rong-ping
2005, 11(4): 311-319.
Abstract (197) PDF (407KB)(7)
Abstract:
Quaternary glacial remnants in the Zanda basin and its peripheral high mountain areas,Tibet,are widespread and continuously developed and have a complete range of types.The main glacial-eroded remnants include U-shaped valleys,knife-edge crests,horns(pyramidal peaks),firn basins,cirques,ice-scoured hills and bedrock drumlins;the till remnants are moraines,outwash deposits,glacial erratic boulders,terminal moraines,lateral moraines and medial moraines.The characteristic morainic and outwash geomorphologies include outwash plains and platforms,morainic hills.The remnants of compressional structures are folds,faults,epigenetic structures formed by faulting,press pits,pressure fractures and deformed gravels.ESR dating of moraines gives a maximum age of 2.33 Ma.According to the features,distribution and ages of the morainic and outwash deposits,seven glacial stages,six interglacial stages and one neoglacial stage of regional glacial development may be distinguished from older to younger.The Zanda basin and its peripheral high mountain areas,Tibet,are now known as a region where the most Quaternary glacial remnants are found and Quaternary glacial remnants are most completely preserved and most continuously developed on the Qinghai-Tibet Plateau.This study provides important data and grounds for the study of the Quaternary glacier evolution,division and correlation glacial stages and study of the paleoclimate and paleoenvironment in this area and the Qinghai-Tibet Plateau.
PALYNOLOGICAL RECORDS IN THE QANGZÊ SECTION OF THE ZANDA BASIN, NGARI, TIBET
HAN Jian-en, YU Jia, MENG Qing-wei, Lü Rong-ping, ZHU Da-gang, MENG Xian-gang, Shao Zhao-gang
2005, 11(4): 320-327.
Abstract (157) PDF (405KB)(14)
Abstract:
Based on palynological records of the Qangzê section in Zanda basin,Ngari,Tibet,the authors have preliminarily defined the Neogene-Quaternary boundary in the area and revealed the vegetational and environmental history of the area since the late Pleistocene.During~2.68-2.45 Ma,the vegetation was dominated by arbores,mainly Pinus,Chenopodiaceae and Artemisia,indicating a cold warm climate in the mountain region.During~2.45-2.11 Ma,herbs increased rapidly and the climate became dry-cold,indicating the characteristic of the bushveld climate.During 2.11-1.49 Ma,the quantity and species of the herbs reached the culmination and the bush increased accordingly,showing that the climate became more and more arid.During 1.49-1.36 Ma,herbs declined slightly but pteridophytes increased relatively greatly,revealing a dry-cold grassland climate.
CHARACTERISTICS OF THE CLIMATIC VARIATATION IN ZOIGÊ IN THE PAST 45 YEARS AND ITS EFFECTS ON THE ECO-ENVIRONMENT IN THE AREA
WANG Yan, ZHAO Zhi-zhong, QIAO Yan-song, LI Chao-zhu
2005, 11(4): 328-332,340.
Abstract (248) PDF (234KB)(14)
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Grassland degradation and desertification have become one of the prominent environmental problems in the Zoigê area.This paper analyzes the characteristics of the climatic variation from 1957 to 2001 and its influence on the eco-environment in the Zoigê area.The annual average temperatures in the area showed a marked tendency of increase,with an increase rate of about 0.23℃ per 10 years,and the seasonal temperatures also showed a tendency of increase,which is especially the case in autumn(from September to November) and winter(from December to February) when the temperatures rose more significantly.The annual precipitation showed a slight decrease tendency,with a decrease rate of 1.75mm per years.In autumn and spring(from March to May),the precipitation showed a tendency to decrease year by year,and more marked decrease was recorded in autumn.However,in summer(from June to August) and winter the precipitation shows a tendency to increase year by year.Affected by warming and drying,the frozen ground and vegetation in Zoigê changed.The eco-environmental problems such as grassland degradation and desertification have had great effects on the social,economic and eco-environmental development in the area.
DEM ANALYSIS OF THE TECTONOGEOMORPHOLOGY OF THE DABIE OROGENIC BELT
CHENG San-you, LIU Shao-feng, ZHANG Hui-ping, SHEN Xu-hui, SU San, LEI Guo-jing
2005, 11(4): 333-340.
Abstract (176) PDF (776KB)(14)
Abstract:
This paper constructs a digital elevation model(DEM) of the Dabie orogenic belt and performs a modeling analysis of its tectonogeomorphology based on the techno-platform of the geographic information system(GIS) and shuttle radar topography mission(SRTM) topographical data.The relief of the Dabie orogenic belt is high in the central part and low on two sides both along the trend of the belt and in the direction perpendicular to the trend,and downfaulted basins are developed on both sides where the relief is low.On the SRTM-DEM geomorphologic map and slope image,the geomorphologic features of main faults such as the Tanlu fault are conspicuous and the drainage systems,which are strictly controlled by faults,mostly present a trellis pattern.Geomorphologically the streams turn at high angles and the main tributaries intersect near right angles.The differential uplift and subsidence of the crust in the area along the faults resulted in the coexistence of graben valleys,fault block mountains and downfaulted basins.This paper also analyzes the relation between the slopes and elevations and gets the information of planation surfaces in the Dabie orogenic belt.
TECTONIC ACTIVITY OF THE LENGKOU FAULT IN EASTERN HEBEI SINCE THE MESOZOIC AND ITS GEOLOGICAL SIGNIFICANCE
CHEN Yun-feng, WANG Gen-hou, ZHANG Chang-hou, QIN Yuan, MU Sheng-li, LIU Yang
2005, 11(4): 341-349.
Abstract (131) PDF (356KB)(8)
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While regionally the whole tectonic framework of the Yanshan intraplate orogenic belt is oriented in E-W and NNE directions,the tectonic line of the Lengkou fault strikes NW.On the basis of detailed field tracing of the Lengkou fault,combined with previous regional research results,the authors hold that the Lengkou fault resulted from polyphase tectonic activities and controlled Mesoproterozoic deposits.The fault activities since the Mesozoic may be divided into four phases:1.north-vergent thrusting in the early Middle Jurassic;2.normal-sinistral strike-slip movement in the terminal Middle Jurassic to Early Cretaceous;3.south-directed thrusting in the Late Cretaceous;and 4.dextral strike-slip movement in the late phase.
CHARACTERISTICS AND ORIGIN OF GREENSTONE BELT TYPE GOLD DEPOSITS IN WESTERN SHANDONG
WANG Hong, HUO Guang-hui, WANG Bao-jun
2005, 11(4): 350-356.
Abstract (201) PDF (315KB)(20)
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With relatively high total gold background values,the strata of the greenstone belt in western Shandong are source beds of gold deposit.Both the well-preserved greenstone belt and TTG-reworked granite-greenstone belt are favorable for gold deposit formation.The formation and distribution of the known gold deposits are both related to ductile shear belts,which are major ore-controlling structure of greenstone type gold deposits.The TTG series,which have experienced strong ductile deformation and fragmentation and contain rich greenstone belt remnants,have close relation with gold deposit formation.Superimposition of Mesozoic Yanshanian magmatic-hydrothermal activities favorable for further gold concentration and mineralization.
2005, 11(4): 357-360.
Abstract (99) PDF (372KB)(7)
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ENVIRONMENTAL ANOMALIES OF TRACE ELEMENTS IN URBAN DUST OF XI'AN CITY
TIAN Hui, DU Pei-xuan, Mei Ling
2005, 11(4): 361-369.
Abstract (263) PDF (298KB)(6)
Abstract:
Based on a study of the background values and enrichment degrees of some trace elements in urban dust in Xi'an City,environmental anomaly areas in Xi'an were outlined,and the element characteristics of various environmental anomaly areas were analyzed.The paper points out that the main pollution-producing elements in urban dust in the anomaly areas are Hg,Ag,Sb and Zn,while the other elements in different anomaly areas are also enriched to different degrees.On the basis of these results,the distributions of trace elements in different anomaly areas were evaluated.
APPLICATIONS OF DIFFERENTIAL GEOMETRY TO QUANTITATIVE ANALYSIS OF STRUCTURAL GEOLOGY
LI Zhi-yong, ZENG Zuo-xun, LUO Wen-qiang
2005, 11(4): 370-376,349.
Abstract (337) PDF (363KB)(27)
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This paper elucidates the necessity of introducing differential geometry in the quantitative study of structural geology and discusses its applications in the quantitative study of structural geology and relevant numerical calculation method.Differential geometry provides a basis for the quantitative description of the geometry of geological structure and construction of a precise mathematical analytical model and is also an important mathematical tool for the indepth quantitative study of the geometry of geological structure and its variations.In order to combine differential geometry with other advanced techniques and methods more conveniently,on the basis of previous studies,the authors summarize the construction and reconstruction of a mathematical model for geological structure,computer-aided automatic analysis and calculation and 3D visualization and movement simulation.It can be applied to the forecasting of fractures,analysis of structural plane deformation,morphological classification of folds,detection of hidden faults and evaluation and study of mineral deposits and oil/gas accumulations.
FINITE ELEMENT ANALYSIS OF EFFECTS OF STICK-SLIP MOVEMENT OF THE SEISMOGENIC FAULT ON THE DEFORMATION OF THE QINGHAI-TIBET RAILWAY——A CASE STUDY OF THE EAST KUNLUN ACTIVE FAULT
OUYANG Yong-long, HU Dao-gong, WANG Lian-jie, ZHANG You, CHEN Xin-long
2005, 11(4): 377-385.
Abstract (170) PDF (507KB)(12)
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The East Kunlun fault(EKF) is one of the present-day most active,left-lateral strike-slip seismogenic faults in the northern Qinghai-Tibet Plateau.Future seismic activities or abrupt strike-slip movement of the EKF will cause serious engineering-geological problems to the Qinghai-Tibet Railway.On the basis of the geometric and kinematic characteristics of the EKF,the deformation effects of the rails occurring when the epicenter of a future earthquake is located near the railway were simulated,with 8 m horizontal left-lateral displacement added.The results show that the bedrock moves 8 m en masse when the epicenter is located near the railway,while the Quaternary loose sediments and groundsill are deformed.The horizontal diaplacement of the Quaternary close to the fault is obviously smaller from above downward,while the rails and groundsill show successive left-lateral crooked deformation for about 25 m.There occur a NE-trending tensional graben and a NW-trending seismic drumlin on the east and west sides of the railway respectively.The rails are seriously distorted near the fault and the stress of the rails is reduced toward both sidess of the fault and the maximum shear stress plane of the rails is perpendicular to the direction of elongation of the rails;therefore the rails are most likely to be subjected to shear once an earthquake happens.On the basis of the simulation,the paper puts forward such countermeasures as widening of the groundsill and replacement of the soil layer near the fault.
APPLICATION OF HYDRAULIC FRACTURING IN-SITU STRESS MEASUREMENTS IN TUNNELLING IN WESTERN XINJIANG
MA Xiu-min, PENG Hua, LI Jin-suo
2005, 11(4): 386-393.
Abstract (173) PDF (422KB)(12)
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Ground stress measurements and study in western China become more and more important with increasing construction investment in recent years.Hydraulic fracturing in-situ stress measurements were carried out in a working area of a mountain tunnel(with a maximum burial depth of 1100 m) in the North Tianshan Mountains along the proposed Jing-Yi-Huo Railway in western Xinjiang,and the values and directions of the principal stresses in the stress field in the North Tianshan region were obtained.According to the results of the stress measurements,the authors have studied the stress state in the stress field of the working area and analyzed the stability of the surrounding rocks of the tunnel and the possibility of the occurrence of geological hazards.