2002 Vol. 8, No. 4

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CHARACTERISTICS OF SPACE DISTRIBUTION OF THE CLIMATIC SNOWLINE IN CHINA
JIANG Fu-chu, WU Xi-hao, WANG Shu-bin, FU Jian-li
2002, 8(4): 289-296.
Abstract (153) PDF (263KB)(10)
Abstract:
The regulars of space distribution of the climatic snowline are both controlled by the changes of altitude and latitude,and by the changes of regional climate.In substance,the changes of setup of climatic snowline in space are a reflection of variations of the hydrothermal condition.According to the climatic data obtained from the 106 weather stations in China,the heights of the climatic snowline have been computed and studied on the basis of the correlatable functions between of the annual mean temperature,the annual precipitation and the rate of solid-state precipitation,and the characteristics of the climatic snowline in the space have been discussed.
UNROOFING HISTORY OF THE WEST KUNLUN VIEWED FROM THE PETROGRAPHY OF SANDSTONE AND CONGLOMERATE FROM YECHENG SECTION,XINJIANG
ZHENG Hong-bo
2002, 8(4): 297-305.
Abstract (218) PDF (344KB)(8)
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Late Cenozoic foreland basin deposits in Yecheng are composed of Moocene mudstone and sandstone(Wuqia Group),Early Pliocene sandstone with minor gritstone(Artux Formation) and Late Pliocene-Early Pleistocene conglomerate(Xiyu Formation). The Miocene strata are dominated by fine-grained clastic material,indicating a distal source and low gradient slope. Palaeocurrent measurements suggest a northward direction,indicating that the Kunlun area was at low elevation. Deposition of Artux Formation marked the first appearance of gravel and lithic detritus,indicating the uplift of Kunlun. Xiyu Formation is characterized by coarse debris flow deposits,marking the strong uplift of the northern part of Tibetan Plateau and unroofing of the West Kunlun.
2002, 8(4): 306-306.
Abstract (123) PDF (32KB)(12)
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DISCOVERY OF PERIGLACIAL PHENOMENA FORMED AT THE LAST STAGE OF LATE PLEISTOCENE ON CONTINENTAL SHELF,NORTH CHINA
YU Hong-jun, HAN De-liang, XU Xing-yong
2002, 8(4): 307-314.
Abstract (109) PDF (327KB)(7)
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At the last Ice Age,the sea level lowered and accordingly water retreated from continental shelf. Affected by cold snap from the North,the temperatures of plain area of East Asia are lower than other areas in same geographic latitude,and the continental shelf plain became one of periglacial geomorphies in east China. These shelf periglacial geomorphy includes widely distributed sandlots,groups of sand dunes,bits and pieces of washin sediment,sedimentary texture of the ice-contact origin,sedimentary texture similar to ice wedge in the northern East China Sea ect.
A SUMMARY REVIEW OF RESEARCH PROGRESS ON GLOBAL CHANGE IN THE SOUTH CHINA SEA
ZHU Zhao-yu, QIU Yan, ZHOU Hou-yun, CHEN Jun-ren, OUYANG Ting-ping, ZHONG He-xian, XIE Jiu-bing
2002, 8(4): 315-322,314.
Abstract (91) PDF (323KB)(8)
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On the basis of data from the litertures and author's study some important progresses of the research into global change in the South China Sea have been reviewed in this paper. The chronostratigraphic sequence covered about 33 Ma has been established; Long-term sequence records and high-resolution records of paleo-environment have been investigated; A series of paroxysmal events(such as the Middle Pleistocene Evolution,the Heinrich event,the D-O events,the fire events,the Toba volcanic event and the tektite event,etc.) have been discovered in the cores from the South China Sea.The results indicate that it is necessary to deepen the research into the South China Sea for understanding the coupled system of atmosphere-marine-continent and the dynamics of global change.
FABRIC ANALYSIS OF GRAVEL IN QUATERNARY GRAVEL BEDS ON BACKBONE AREA OF NIQINGTANGGULASHAN MOUNTAINS
ZHU Da-gang, ZHAO Xi-tao, MENG Xian-gang, WU Zhong-ha, SHAO Zhao-gang, FENG Xiang-yang, WANG Jin, YANG Chao-bin
2002, 8(4): 323-332.
Abstract (295) PDF (346KB)(8)
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The authors expound the source, the origin and the transport of different original Quaternary gravel beds in south and north of Nianqingtanggoulashan Mountains, from the bedrock strata, the compositional, the granulometric and the psephitic analysis, based on fabric analysis of Quaternary gravel beds on backbone area of Niqingtanggulashan Mountains. It is obvious difference in the rock composition, the grain sizes, the sphericity, the intensity of weathering on the 3 Gravel Beds of glacial epoch phases in the middle section of Nianqingtanggoulashan Mountains. This difference reflecs the denudation of the different rocks of Nianqingtanggoulashan Mountains in the doming of Qinghai-Xizang (Tibet) plateau.
ENVIRONMENTAL CHANGES AND ITS RESPONDING TO TECTONIC UPLIFT OF TIBETAN PLATEAU DURING THE LAST 2.8 Ma RECORDED BY LAKE SEDIMENTS
CHEN Shi-yue, WANG Su-min
2002, 8(4): 333-340.
Abstract (109) PDF (291KB)(9)
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According to the studies of lake sediments' lithological property, grain size, pollen and magnetic susceptibility of the Cuoe lake in the central Tibetan Plateau, and combining the achievement of RH-core of Zoige basin in eastern Tibetan Plateau, we discuss the process of environmental changes and its responding to the tectonic uplift of Tibetan Plateau during the last 2.8Ma. The sedimentary records from the outcrop indicate that the Cuoe Basin was first formed by fault activity at about 2.8MaBP and a strong uplift movement occurred at about 2.6MaBP and a relatively leveling epoch under the background of the uplift from 2.6 to 0.8MaBP. Three tectonic uplift movements have been revealed by the sedimentary records in core of Zoige basin since 0.9MaBP,showing three stages of environmental evolution of the plateau. There was no strong dry climate event near 2.6MaBP, corresponding to the bottom age of Loess in the Loess Plateau. The sedimentary records of lake sediments in the plateau show a wet climate during the prosperous periods of loess accumulation such as L15、L9、L6.
THE DISCOVERY OF THE QUATERNARY FOSSIL ICE-WEDGES IN CHENGDU PLAIN
LI Yong, LI Yong-zhao, ZHOU Rong-jun, WANG Guo-zhi, SI Guang-yin, WANG Feng-lin, LIANG Xiang-zhong
2002, 8(4): 341-346.
Abstract (134) PDF (207KB)(6)
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Recently,four fossil ice-wedges have been found at the outcrop excavated,at the north end of the Plio-Pleistocene Dayi Conglomerate Profile on the west bank of the Xiejiang River near Dayi Nitrogenous Fertilizer Factory,west of the Chengdu Plain.Its co-ordinates are 30°35'N,103°31'E,and 530m above sea level.
These ice-wedges have been developed on the top of the outcrop of Dayi Conglomerate.The largest wedge is 3m wide at the top,and extends 2.5m vertically.The wedges extend vertically downwards,and obliquely intersect the bedding planes of the Dayi Conglomerate.They thus postdate deposition of the Dayi Conglomerate and appear to be epigenetic.The sediments in the ice-wedges are different from the Dayi Conglomerate.The former are brownish yellow,well-sorted,with 5cm~15cm clasts in a fine-grained matrix.The latter is grey-white or yellow-grey,poorly-sorted,with 20cm~30cm clasts.The ice-wedge sediments have a higher percentage of gravel(95%) compared to the Dayi Conglomerate(85%).In addition,the distribution of ab planes for pebbles in the ice-wedge sediments is random,whereas ab planes in the Dayi Conglomerate are dominantly orientated 170°~210°∠30°~40°.According to these differences,the ice-wedges can be distinguished from outcrops of the Dayi Conglomerate.The age of sediments in the ice-wedges is 0.171 Ma from ESR data.This suggests that these ice wedges might correspond to stage 6(0.195Ma~0.128Ma) of the oxygen isotope temperature curve from deep sea-core V28-238.This is similar to the climatic fluctuations recorded by L2~5 (0.195Ma~0.180Ma) and L2~4(0.180Ma~0.167Ma) of Chinese loess,and the penultimate glacial stage in Qinghai-Xizang Plateau.It is generally considered that ice-wedges are indicative of permafrost,therefore the samples we obtained suggest that permafrost developed in the Chengdu Plain during the Pleistocene.
It has been reported that permafrost can only develop below -6℃ in high-latitude areas,and the southernmost extent of permafrost occurrence is equivalent to the -2℃ to -4℃ isotherm.However,the annual air temperature in Dayi is about 16℃ now,which means the temperature during ice wedges formation may have been at least 18℃ less than present.
A REVIEW OF THE QUATERNARY GEOLOGY AND ENVIRONMENTAL CHANGE IN ZHOUKOUDIAN, BEIJING
CHENG Jie, WANG Hai-zhi, ZHANG Xi-jun, YU Jiang-kuan, DU Hong-gan
2002, 8(4): 347-353.
Abstract (180) PDF (229KB)(11)
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This paper is a review of the Quaternary geology,environmental change,palaeoanthropology and archeology made during the last 80 years in Zhoukoudian area,Beijing,and gives superficial suggestions deeply to research on the Quaternary geology,environment and palaeoanthropology in this area.For the last 80 years,in Zhoukoudian area many fossils of Homo erectus pekinensis, early Homo sapiens and late Homo sapiens were found;a lot of old stone artifacts were collected;the Quaternary stratigraphical sequence was set up;the ice wedges of the Early pleistocene were discovered and the Taipingshan Cold Age was named;the three circles of the warm-cold fluctuations in the Middle Pleistocene were recognized.The last researches show that it is very important to search for the new Early Pleistocene fossil localities,to study on the evolution and social behavior of "Peking man",to research on the environmental change for the Quaternary period,and to yield a stratigraphic sequence of the biotic-climatic events in Zhoukoudian area in the future.
PALEOCLIMATIC CHANGES AROUND MEDIEVAL WARM PERIOD IN LEIZHOU PENINSULA,CHINA
CHU Guo-qiang, SUN Qing
2002, 8(4): 354-360.
Abstract (150) PDF (233KB)(7)
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Huguangyan Maar Lake is located in Leizhou Peninsula,Guangdong Province.The Chronology of its lake sediments is determined by the methods of 137Cs,AMS and 14C,and Organic carbon(TOC),nitrogen(TN) and inorganic carbon(TIC) are analyzed.In this hydrologically closed lake,TIC variations may reflect changes in the precipitation/evaporation ratio.TOC and TN in the sediments are proxy indicators of lake productivity and nutrient input.In this tropical area,where surface water temperatures are high year-round,temperature is probably a less important factor controlling algai productivity.Therefore,increased rainfall may be responsible for the observed increase in TOC,TN and TOC/TN.
High TIC content correlates with low concentrations of TOC and TN,and indicates two drought episodes dated to AD 670~760 and AD 880~1260 in the sediments of lake Huguangyan.The drought Medieval Warm Period indicted by geochemical proxy in Huguangyan Maar Lake is temporally correlated with the drought period from diatom and pollen data in Longgan Lake,Anhui Province.They may imply that thereis a drought in Medieval Warm Period in south China.
THE ELEMENTARY ACKNOWLEDGE ON THE IMPORTANCE OF ENVIRONMENTAL EVOLUTION OF YUNNAN PLATEAU
MING Qing-zhong, PAN Yu-jun
2002, 8(4): 361-368.
Abstract (172) PDF (246KB)(10)
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Yunnan plateau is one of the four plateaus in China.Comparatively,there are only a few researches on the environmental evolution and its resource environmental effects,and these researches are not deep enough.The research on plateau environmental evolution in the Yunnan will be beneficial to solving the problems of the uniqueness of Yunnan plateau and to the development of earth science,and will be beneficial to the implement of Great Development in Western Provinces of China and the sustainable development.After Yunan underwent the peneplanation in Tertiary its environmental evolution began from the Yunan movement occurring in late Pliocene which made the leveling surface displacement and disaggregated,then the modern landform and water system were formed gradually,and the environment controlled by the ancient monsoon changed alternating influence of south-east and south-west monsoons,then the biology diversity,environmental diversity and resource diversity came into being,and influenced the diversity of ethnicity,the diversity of culture.
MAGNETOSTRATIGRAPHY AND PALEOCLIMATIC SIGNIFICANCE OF AN EOLLIAN SEQUENCE FROM THE XUANCHENG AREA,ANHUI PROVINCE
QIAO Yan-song, GUO Zheng-tang, HAO Qing-zhen, WU Wen-xiang, ZHANG Zhong-shi, ZHAO Hua, ZHU Ri-xiang
2002, 8(4): 369-375.
Abstract (260) PDF (218KB)(9)
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A loess-soil sequence near Xuancheng from the Yangtze valley is investigated using magnetostratigraphy and luminescence dating to determine the location of B/M boundary.This boundary is found to be located within the middle-lower part of the so-called plinthitic laterite.,a widely distributed mid-Pleistocene tropical soils in southern China.The magnetostratigraphy data,combining with the OSL age suggests a basal age of the typical eolian depositional loess-soil sequence is about 0.85Ma.This age boundary corresponds to a significant global climate change,also is recorded in the marine sediments and in the loess-paleosol sequence in northern China.It also coincides with two geological events,intensive uplift of the Tibetan Plateau and the extension of the global ice volume.We interpret the onset of eolian loess deposition in the middle-lower reaches of Yangtze River as a result of hydrological and circulation changes associated with above two events occurring at the mid-Pleistocene.
STUDY ON THE DAM ABUTMENT'S SIDE SLOPE STABILITY OF LONGPAN DAM REGION OF TIGER LEAPING GORGE HYDROELECTRIC STATION IN JINGSHA RIVER
WANG Bo, LI Yu-sheng, WANG Yun-sheng, XIE Hong-yu
2002, 8(4): 376-382.
Abstract (181) PDF (306KB)(9)
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The paper makes a analysis for natures of the basic geological environment and for the geomorphology features in Longpan dam region;as a result,the objective calculative model is obtained.On this condition,the stability of dam abutment is computed with FEM simulation in present tectonic stress field,and landslide of right bank is computed with unequal thrust method,then makes analysis of the results and concludes that the dam abutment's side slope of left bank is on the state of sress release and landslide of right bank is on the stress relaxation condition under the present tectonic stress field,and the dam abutment's side slope is stable under the natural condtion,the landslide of right bank is also stable under the various condtions.