2003 Vol. 9, No. 4

Display Method:
QUATERNARY GLACIAL VESTIGES IN THE WESTERN HJILLS,BEIJING
WU Xi-hao, JIANG Fu-chu, XU He-ling, XIAO Hua-guo
2003, 9(4): 289-302.
Abstract (149) PDF (1548KB)(6)
Abstract:
Quaternary glacial vestiges in the Western Hills,Beijing Municipality,have been investigated and studied from the 1950s on.However,since the 1980s,divergent views on the related palaeoglacial phenomena have been put forward by some geographers and geologists,whose main viewpoint is that the occurrence of the phenomena concerned can be explained by the nivation and solifluction in the periglacial climate.In this trip,the macroscopic and microcosmic features of the Quaternary glacial vestiges that are the key to judging and to understanding wheter the palaeoglaciers were developed in the following five visited localities:glacial pavement at Moshikou,Quintuoling till of the Guantuoing glaciation on the Guantuo Ridge,till of the Zhaojiatai glaciation in the west of Taipingzhuang,the glaciofluvial deposits of the Zhaojiatai glaciation in the north of Lujiatan Township and till of the Guantuoling glaciation in the east of Dafuzhuang.
BASIC FEATURES OF SPATIAL DISTRIBUTION OF THE LIMITS OF PERMAFROST IN CHINA
JIANG Fu-chu, WU Xi-hao, WANG Shu-bing, ZHAO Zhi-zhong, FU Jian-li
2003, 9(4): 303-312.
Abstract (122) PDF (357KB)(12)
Abstract:
In this paper,according to the correlation between the permafrost and climatic elements,combined with distribution of the modern permafrost in China,the annual mean temperature,annual temperature range and heights of the limit of permafrost have been calculated and studied on the basis of the meteorological data obtained from 104 weather stations in China.The altitudes of spatial distribution of the limits of permafrost are obviously controlled by changes in altitude and latitude,and inoreose from north to south.The limit of permafrost in eastern China rises from <1200 m in Northeast China to (5700 m) in the Haikou area,Hainan;that in northwestern China rises from 2600 m in the Altay Mountains to 4500 m in the Kunlun Mountains,being 1400-800 m higher than that at the same latitudes in eastern China.The heights of the limit of permafrost are essentially maintained at 4500-5000 m on the Qinghai-Tibet Plateau.Lastly,the relations between the climatic limit of permafrost and modern climatic snowline are discussed.
NEOTECTONICS IN THE SOUTHERN PART OF THE TAIHANG UPLIFT,NORTH CHINA
ZHANG Yue-qiao, YANG Nong, MA Yin-sheng
2003, 9(4): 313-329.
Abstract (169) PDF (1340KB)(17)
Abstract:
Based on TM remote-sensing image interpretation and field observation of slip vectors of faults,coupled with the thermal isotope and radioactive isotope chronological studies of younger geologic bodies,this paper mainly describes the morpho-structural features in the southern segment of the Taihang uplift,defines the phases of neotectonic deformation and determines the neotectonic stress field and its transition history.Studies indicate that in the Neogene the southern segment of the Taihang Mountains experienced two major phases of extension.In the mid-late Miocene the area was subjected to nearly NE-SW extension,concomitantly with extensional eruption of basic volcanic rocks in North China.The extension was concentrated in fault zones on the eastern and southern margins of the area.During the Pliocene to early Pleistocene strong NW-SE crustal extension resulted in disintegration of the planation geomorphology and formation of a graben basin in the area.Since the mid-late Pleistocene the southern Taihang Mountain marginal fault zone has become a main boundary zone of neotectonic deformation.Analyses of fault plane slip vectors and displacement features of younger piedmont alluvial fans and small gullies along the fault suggest that the fault zone is an oblique-extensional,sinistral strike-slip boundary fault znoe,with the extension oriented in a NW-SE to NNW-SSE direction.In the tectonic context,the NE-SW extension in eastern China in the Miocene is related to the dynamic process of back-arc spreading resulting from westward subduction of the Pacific plate to the east,while the neotectonic deformation since the Pliocene is related to the rapid uplift of the Qinghai-Tibet Plateau and eastward tectonic extrusion due to the late-stage India-Eurasia collision.
INFORMATION OF HOLOCENE ENVIRONMENTAL CHANGE FROM LACUSTRIAN DEPOSITS OF THE FOYECHI LAKE SECTION,TAIBAI MOUNTAIN
CUI Zhi-jiu, TANG Yuan-xin, LI Jian-jiang, LIU Hong-yan, LIU Geng-nian
2003, 9(4): 330-336.
Abstract (198) PDF (219KB)(9)
Abstract:
Foyechi Lake,located at an elevation of 3300 m above sea level,near the summit of Taibai Mountain(3767 m), is an alpine ice-scour lake developed in a bergschrund.A section of 210 cm thick lacustrian deposits in the lake was measured. Analyses of the grain size,sporo-pollen and samples for dating show the climate has undergone marked cold-warm and dry-wel changes since 8200 a BP in the Holocene.The 8200-6800 a BP interval was a warm and humid phase,with temperature increasing significantly at 7200 a BP.The climate fluctuated at 6800-5900 a BP,with a short cooling phase at 6300 a BP,and a significant warming phase at about 6000 a BP.Temperature and precipitation decreased at 5900 a BP,which ended at 5200 a BP with the lowest values.Then the temperatures rose slowly and became warm and humid at 4800-2600 a BP.It is believed that the climate was warmest around 3000 a BP.The climate became cold and wet again at 2600-900 a BP,with the temperatures and precipitation reaching their the lowest values at 1500 a BP.The climate becomes better since 900 a BP.
TIME SCALE OF LOESS IN THE SANMENXIA AREA
ZHAO Zhi-zhong, WANG Shu-bing, JIANG Fu-chu, WU Xi-hao, XIAO Hua-guo, TIAN Guo-qiang, LIU Ke, XUE Bing, WANG Su-min
2003, 9(4): 337-342.
Abstract (184) PDF (199KB)(9)
Abstract:
The 153 m thick Caocun loess profile at Zhangbian Township located at the southeast margin of the Loess Plateau is typical of the Sanmenxia area.In the profile there occurs a complete,145 m thick loess-paleosol sequence consisting of continuous dust deposits from L1 to L33 145 m thick.The establishment of an accurate time scale of the Caocun loess sequence is important not only for the study of (millenial-scale) paleomonsoonal change on the Loess plateau but also for the correlation of global paleoclimate changes between land and sea.In this paper four available time scale models are introduced and the time scale of loess in Sanmenxia is studied using the susceptibility model and grain-size model and checked.It is feasible to establish the time scale of the Caocun loess using several models.
N-S-TRENDING ACTIVE STRUCTURES ALONG THE QINGHAI TIBET RAILWAY AND THEIR INFLUENCES ON RAILWAY BED ENGINEERING
YI Ming-chu, WU Zhen-han, HU Dao-gong, PENG Hua, LIU Qi-sheng, WU Zhong-hai
2003, 9(4): 343-354.
Abstract (151) PDF (1110KB)(14)
Abstract:
A nearly N-S-trending active tectonic belt is attested to exist along the Qinghai-Tibet Railway under construction according to surface geological route survey,active tectonic mapping at different scales and geophysical exploration of different depths.The N-S-trending tectonic belt along the railway exhibits evidently active faulting,crustal deformation,Quaternary down-faulted basins,earthquake activity,linear distribution of hot springs and distinct geophysical anomalies and different formations distributed on both sides of it.The N-S-trending tectonic belt also shows relatively strong tectonic activity at present and a trend of enhancing of the tectonic activity in the future and can induce many kinds of geological hazards and jeopardize the railway bed,highway bed and permant engineering works to different degrees.
RECORDS OF DEPOSITIONAL BREAKS AND ENVIRONMENTAL CHANGE AT THE ZANONGTANG SECTION OF NAM CO, TIBET SINCE 10 ka BP
ZHU Da-gang, ZHAO Xi-tao, MENG Xian-gang, WU Zhong-hai, SHAO Zhao-gang, FENG Xiang-yang, YANG Chao-bin, WANG Jian-ping
2003, 9(4): 355-362.
Abstract (150) PDF (282KB)(7)
Abstract:
Studies of sedimentary structures,more soluble and 14C dating salts,magnetic susceptibility,grain size,carbonates,and sporopollen of the Holocene Zanongtang Formation have yielded information of depositional breaks and environmental change since 10 ka BP in the Nam Co area,Tibet.The data indicate the following:since 9010-8560 a BP the climate changed from slightly cold-dry through slightly moist to relatively moist;during 4870-2350 a BP the climate changed from warm-moist to warmer-moister and then changed from the Holocene climatic optimum to relatively moist.This suggests that in the Holocene the area experienced two major climatic cycles and multiple pronounced cold-warm and dry-moist oscillations on the basis of the general trend of gradual drying.
STUDY OF THE MINJIANG RIVER TERRACES IN THE WESTERN SICHUAN PLATEAU
YANG Nong, ZHANG Yue-qiao, MENG Hui, ZHANG Hui-ping
2003, 9(4): 363-370.
Abstract (185) PDF (465KB)(9)
Abstract:
Based on field observations and ESR dating of terrace deposits along the upper Minjiang River valley,combined with previously dating ages of the terraces,this paper describes the formation of late Quaternary terraces of the trunk river in the upper reaches of the Minjiang River and its incision history and discusses the response of terrace evolution to the uplift of the Minshan-Longmenshan tectonic belt.
NEW PROGRESS IN QUATERNARY DATING RESEARCH
SUN Hong-yan, LI Zhi-xiang, TIAN Ming-zhong
2003, 9(4): 371-378.
Abstract (177) PDF (333KB)(9)
Abstract:
The Quaternary plays an important role in the geological history because it is closely related to the human beings.Therefore highly reliable and precise Quaternary dating is needed.Now geologists have improved and developed many Quaternary dating methods.This paper discusses some recent advances in the Quaternary dating in respect to rock stratigraphy,biology,magnetic stratigraphy,archaeology and isotope dating.The main progress of these methods is as follows:the dating precision and efficiency have bean raised markedly while the required dosage of a dated sample is reduced significantly because of the development of technologies,such as the Ar-Ar laser microprobe dating;and these dating methods can be used in wider research fields. For example,the ESR method has used in dating of tills and the sequences established according to the dating results may correlate with the deep sea oxygen isotope stages. However,it is necessary to have plenty of geological experience,choose appropriate dating methods according to the features of the samples and use as many appropriate methods as possible for comparative dating to improve the reliability of dating.
DEVELOPMENT AND SCIENTIFIC SIGNIFICANCE OF ADJUSTABLE MAGNETIC FIELD COILS AND THE STANDARD LOCATION CHECKOUT SYSTEM
ZHANG Rui-feng, ZHANG Jing-xin
2003, 9(4): 379-382.
Abstract (81) PDF (187KB)(5)
Abstract:
Before the successful development of this system, the coil spacing in the magnetic field coil system was fixed and there are large magnetic gradients in almost all the environment; therefore, the uniformity and orthogonality designed theoretically were not adjustable or able to be supervised or corrected when the environment changed. The development of this system makes the coil spacing relatively equally adjustable or asymmetrically adjustable and so can compensate the magnetic gradient in the objectivc environment,thus raising the precision of supervision, solving the problem of the magnetic gradient correction effectively and filling in the gap in this application in China.