地质力学学报

MACROSCOPIC AND MICROSCOPIC FEATURES OF THE QUATERNARY GLACIAL VESTIGES IN THE TANZHESI AREA OF THE WESTERN HILLS OF BEIJING

Wu Xihao, Jiang Fuchu, Xu Heling, Xiao Huaguo

1997, 3(4): 3-12.

Abstract (95) PDF (471KB)(5)

Abstract:
After a study of macroscopic features for the Quaternary glacial vestiges in the Tanzhesi area of the Western Hills of Beijing,the analysis of the appearances and assemblage features of quartz grain surface textures has been carried out for the palaeoglacial deposits of the Guantuoling and Zhaojiatai glaciations.The surface textures of quartz grains indicate a dominance of the appearance assemblage of glacial origin in the Guantuoling till and Dafuzhuang till of the Guantuoling glacial stage as well as in the Tainpingzhuang till of the Zhaojiatai glaciation,and glaciofluvial origin for the Lujiatan deposit of Zhaojiatai glaciation.Therefore,based on the macroscopic and micrioscopic features of the palaeoglacial vestiges in this area,it is certain that two palaeoglaciations had developed in the Early and Middle Pleistocene respectively.

TECTONIC ACTIVITY IN SEMI-ARID AREA OF NORTH CHINA DURING LATE QUATERNARY

Zhu Zhaoyu

1997, 3(4): 13-19.

Abstract (222) PDF (276KB)(9)

Abstract:
The last 0.2 Ma has witnessed very obvious tectonic activity in the semi-arid area of North China.There are many active structures dated as of late Quaternary age in the area,such as normal fault,reverse fault,strike-slip fault,fold,sag,uplift,tectonic landform,tectonic terrace,fossil earthquakes and volcanic structures.The maximum amplitude of the vertical movement is about 88-132m with an average rate of 0.44-0.66 mm/a in the centre of tectonic blocks,and in the active tectonic zone around these blocks the maximum amplitude is about 210-343m with an average rate of 1.05-1.72mm/a,the intensity and rate of the movement contimually increasing.The principal compressive stress trends NE SW and E W.The tectonic activity in the last 0.2 Ma may be divided into 6 stages with ages of about 200,100-70,50-30,10-7,0.7 and 0.3 kaBP,respectively.The most intensive tectonic movement in the late Quaternary fell in the periods of 100-70 and 50-30kaBP.The tectonic reactivation in the semi-arid area of North China is correlative with the uplift of the Tibetan Plateau,serving as one of the controlling factors in the formation and evolution of the arid and semi-arid areas of North China.

ON THE TECTONIC LANDFORM OF THE YUMU MOUNTAIN, HEXI CORRIDOR,GANSU PROVINCE

Li Youli, Yang Jingchun, Li Baojun, Tan Lihua

1997, 3(4): 20-26.

Abstract (182) PDF (264KB)(7)

Abstract:
The Hexi Corridor,located in the northeastern margin of the Qinghai-Tibetan plateau,is a foreland basin system formed by the northeastward push of the plateau.The Yumu mountain is a transverse highland between the Zhangye basin and Jiudong basin in the system.Based on the field study of fault outcrops and landform deformations,combining with TL and ¹⁴C ages,it is concluded that the north marginal fault of the Yumu mountain is a thrust with left-lateral slipping and the east marginal fault is a thrust with right-lateral slipping,and the Yumu Mountain developed from the resulting uplifting of the Yumu Mountain block along these faults.

AGE OF THE VERMICULATED RED SOIL IN JIUJIANG AREA,CENTRAL CHINA

Jiang Fuchu, Wu Xihao, Xiao Huaguo, Zhao Zhizhong, Wang Sumin, Xue Bin

1997, 3(4): 27-32.

Abstract (185) PDF (263KB)(13)

Abstract:
There is a wide distribution of the vermiculated red soil in the middle and lower reaches of the Changjiang River.A preliminary study of the Changhongdadao profile in Jiujiang City was carried out in this paper.In the profile,the strata can be divided from the bottom upwards into fluvial sandy gravel,horizontally vermiculated ferruginous red soil,vertically vermiculated red soil,red clay and eolian Xiashu loess,3.3m,4.5m,5.9m,3.6m and 4.1m thick respectively.The boundary between the Brunhes normal zone and the Matsuyama reversed zone is know from magnetostratigraphic study to occur in the middle part of the vermiculated red soil bed at a depth of 12.9m and the Jaramillo normal subzone in the ferruginous vermiculated red soil bed at a depth of 15.1m to 16.1m.The average sedimentation rate is calculated by Cande and Kent's palaeomagnetic age model and by thermoluminescent dating and hence the age of bed boundaries.The results show that the ferruginous vermiculated red soil was deposited during 1.232-0.869MaBP,the vermiculated red soil during 0.869-0.392 MaBP and the red soil during 0.392-0.101MaBP.
The sedimentary sequence in the Changhongdadao profile indicates a periodic climate change of about 0.4Ma.It is consistent with the tectonoclimatic cycles as revealed by the tectonic layers in the Loess Plateau and the Qinghai-Tibetan Plateau and the change of the earth's orbital eccentricity.

PRELIMINARY STUDY ON THE DESERT -LOESS DEPOSIT GROUP IN THE NORTH SHELF AREA AT THE CLOSE OF LATE PLEISTOCENE

Yu Hongjun, Han Deliang, Chu Fengyou

1997, 3(4): 33-38.

Abstract (201) PDF (244KB)(9)

Abstract:
At the close of Late Pleistocene,as a result of strong monsoon action,the desert loess deposit group was formed in western China(loess plateau and the desert region to its west).With its arrival in the shelf areas,two new desert-loess deposit groups were formed.One is the Bohai Sea desert-loess deposit group,including the floor of Bohai Sea and the desert zone along the coast and the loess deposits containing foraminifera distributed in the western coast of Liaodong Peninsula,the Miaodao Islands,and to the west of Penglai City,Shandong Province,the other is the Yellow Sea desert loess group,including the desert area in the North Jiangsu shoal and Yangtze River delta region prior to Holocene transgression and the Xiashu loess in the vicinity of Nanjing City.

RECORD OF ENVIRONMENTAL CHANGE IN RESHUI PROFILE AT KUNLUNSHAN PASS SINCE 18 kaBP

Liu Gengnian, Cui Zhijiu, Wu Yongqiu, Xu Qinghai

1997, 3(4): 39-45.

Abstract (223) PDF (287KB)(6)

Abstract:
A study of the sedimentary structures,chemical compossition,grain size and sporopollen assemblages of the 270 cm thick sediments of the Reshui Profile has yielded information of environmental change since 18 kaBP at Kunlunshan Mountains Pass,Qinghai Tibetan Plateau.The evidence indicates a severe cold-dry climate in 18-11 kaBP,a period which corresponds to the time span from the climax to the end of Late Glaciation.There were two warmer periods in 10-7.8 kaBP and 4.5-3 kaBP.Two colder periods occurred in 6.7-5.6 kaBP and in a time after 2.3 kaBP.

ENVIRONMENT CHANGES DURING THE CLOSE OF PLEISTOCENE IN THE TAIBAI BASIN IN THE QINLING MOUNTAIN

Fan Shuxian, Zhao Jingbo, Wu Xihao, Tong Guobang, Zhang Junpai

1997, 3(4): 46-51.

Abstract (275) PDF (313KB)(11)

Abstract:
The environment during the close of Pleistocene is reconstructed from the sporopollen spectrum of the Guali Village section.It was a butula-rich forest-steppe or bushveld steppe.The prominent fluctuation of sporopollen content indicates the intense change of climate.The section contained four poor sporopollen events(at depth 15.6-15.8m,10.7-10.9m,5.6-5.8m and 3.4-3.5m).It is characterized by a sharp decrease of woody plant with little or no tree pollen and a increase of herb pollen content.These... More

RECORD OF PALEOENVIRONMENTAL EVOLUTION OF TAIHU LAKE IN THE PAST 14000 YEARS

Qu Wenchuan, Xue Bin, Wu Yanhong, Wang Sumin, Wu Ruijing, Zhang Pingzhong, Chen Jianfa

1997, 3(4): 52-61.

Abstract (204) PDF (381KB)(9)

Abstract:
From the analysis of the magnetic susceptibility,TOC,TN,pigment,organic carbon isotope,HI,saturated hydrocarbon and ¹⁴C dating etc.of the sediment samples from cores of two boreholes in the Taihu lake,a knowledge of the evolution of paleoenvironment of the lake during the last 14ka is achieved.The results show that the lake has undergone the following stages:The Lake was at a low level,or even became exposed during 14.3-13.3kaBP,reflecting an arid climate.There existed a transitional stage during 13.3-12.4kaBP,the climate being slightly warm and wet.There are indications of a cold and dry climate around 11.5kaBP,probably corresponding to the Younger Drays event,comparable with other areas in east China.10.9-10kaBP is obviously a warm period with a reducing environment and relatively deep water.There was a alternation of cool and warm climate during 10-7.2kaBP.It was warm and wet during 7.2-5.737kaBP.Many climate indicators changed suddenly in 5.05kaBP,probably a reflection of change in material source and a sedimentation break.The uppermost surficial sediment shows features of a modern environment.The West Taihu Lake is of algae-type with high production and high eutrophication and is characterized by oxidation environment and flourishing algae.The East Taihu Lake is of macrophyte-type with low production and low eutrophication where the organic material mainly came from the exuberant aquatic vascular plants.

COLLAPSIBILITY OF LOESS AND ITS ORIGIN

Zhao Jingbo, Yuo Yingli, Chen Yun

1997, 3(4): 62-68.

Abstract (175) PDF (268KB)(9)

Abstract:
It was found from the determination of the collapsibility of loess that there is a downward attenuation of collapsibility due to overweight or vertical fluctuation of collapsibi lity due to the degree of pedogenesis.The microstructure of loess is divided into 18 types on the basis of the microscopic study and the correlation between collapsibility and pedogenesis.It is thus known that collapsibility only occurs in some specific soils during pedogenesis,e.g.the brown soil,Chestnut soil,Sieronems,Chernozems,Loessial Soil and Drab Soil of CaCO₃ that have experienced poor pedogenesis.No collapsibility occurs in wet soils that have undergone strong pedogenesis.

ENVIRONMENTAL CHANGE IN THE POYANG LAKE AREA DURING LATE-PLEISTOCENE

Wu Yanhong, Yang Xiangdong, Wang Sumin

1997, 3(4): 69-76.

Abstract (204) PDF (369KB)(11)

Abstract:
During Late-Pleistocene, a stratigraphic sequence of alternating wind-drift sand, loess and limnetic facies developed in the northern Poyang Lake area. In this paper, environmental change and course of monsoon chage during Late-Pleistocene have been studied based on the analysis of the environmental proxies collected from five exposure pro files in Jiujiang, Hukou and Pengze. As a result, we have found that there was a cold and dry climate controlled by stronger winter monsoon during 147-129.06 kaBP. Therer was an obvious periodicity of climate during 129.6-76 kaBP:it was warm and wet in the early and middle stage and became attenuated in the late stage with some intervening cold events. Moreover this period began with a n increasingly strong summer monsoon until 120 kaBP. when it beg an to decline, and became strong again after a weak period of 103-92ka BP. In the stage of 76-55ka BP, it was cold and dry, as a result of severe winter monsoon. The summer monsoon became strong again during 55-25 ka BP, leading to a warm and wet climate with cold fluctuations. The climate tended to become dry after 13ka BP.

CHARACTERISTIC FEATURES OF THE SEDIMENTARY SAMPLES FROM THE BOREHOLE M₁ IN JIANGHAN PLAIN AND RECONSTRUCTION OF PALAEOENVIRONMENT

Zhu Yuxin, Xue Bin, Yang Xiangdong, Xia Weilan, Wang Sumin

1997, 3(4): 77-84.

Abstract (174) PDF (297KB)(26)

Abstract:
By an analysis of the lithology,grain size,spore and pollen of the lake sediments from borehole M₁ in Jianghan Plain as well as ¹⁴C dating the palaeoclimate and palaeoenvironment since Late Glacial have been reconstructed as follows.There was a lake expansion at the close of the Late Great Ice Age when the climate was temperate and wet and the lacustrine sediments were deposited.The climate was temperate and turned dry at the end of Late Ice Age,when the boring site was controlled by fluvial environment.In early Holocene(10-8.9kaBP),the climate turned temperate and wet.It was warm and wet generally in Holocene Megathermal(8.9-3.5kaBP),in which the period of 6.8-4.9kaBP was the optimum,and there were 2 cool events occurring at 4.9-4.8kaBP and 4.4-4.2kaBP.Lakes began to form at 4.8kaBP,and the fossil Yunmengze lake was at its climax of development at 3.9-3.5kaBP.The temperature decreased in late Holocene(3.5-1.7kaBP) compared with that in Megathermal,in which it was temperate-cool and wet in 3.5-2.5kaBP,temperate and wet in 2.5kaBP with a stable lake environment.The Yunmengze lake shrank since 1.7kaBP,leading to exposition of the boring site.

“LOESS” IN XUANCHENG PREFECTURE OF ANHUI PROVINCE AND PALAEOLITHIC CULTURE

Yang Dayuan, Li Xusheng, Lu Huayu, Han Huiyou, Ren Lixiu, Fang Yingsan

1997, 3(4): 85-89.

Abstract (227) PDF (225KB)(7)

Abstract:
In the Xuancheng prefecture of Anhui province,there are quite a few profiles composed of aeolian-dust accumulation,in which were buried palaeolithic stonewares.The profile located at Chenshan hill(30°52'32″N,118°51'58″E),Xuancheng prefecture,was accumulated since 81.7×10⁴aBP,and 8 cycles of wind dust accumulation-palaeosol development are found by an analysis of the susceptibility and grain size of samples continuously collected in the profile.The depositional environment of the aeolian-dust accumulation is similar to that of the loess accumulation in northern China.The palaeolithic stoneware from Chenshan profile as was shaped by simple chopper belongs to the southern culture system in the palaeolithic age,which was diferent from that north of the Qinling Mountain-system-Huaihe River in the stoneware assemblage.

A GEOCHRONOLOGICAL STUDY OF THE SALAWUSU STRATA IN NORTH CHINA

Su Zhizhu, Dong Guangrong, Jin Heiling

1997, 3(4): 90-96.

Abstract (223) PDF (297KB)(15)

Abstract:
Salawusu Formation in Salawusu river area is one of the standard sections of Late Pleistocene strata in North China.However,there are a lot of different views about the strata since the establishment of Salawusu Formation,especially in the aspects of sedimental facies,stratigraphic age and its climate significance.Here,by the stratigraphic subdivision and dating,the following recognitions can be gained:
1.Salawusu Formation is mainly composed of fluvial lacustrine sediments,which corresponds to the stage 5 of deep sea ¹⁸O and formed between about 140-70kaBP.Chengchuan Formation mainly consists of fossil aeolian sands with some lacustrine silty-clay in the middle part,which corresponds to the stages 2-4 of deep sea ¹⁸O and formed between 70-10 kaBP.Dagouwan Formation is composed of lacustrine sediments and black-paleosol,which formed in early middle period of Holocene with the warm-humid climate,Dishaogouwan Formation consists of sub-loess and aeolian sands,which represented the sedimentation in the cold-dry climate during the late Holocene.
2.As a fluvial-lacustrine sedimentary strata,Salawusu Formation is quite different form its overlying Chengchuan Formation whether in geochronolgy,lithology and sedimentary facies or in palaeontology.Chengchuan Formation and Malan Loess belong to heteropic deposits (sandy and loessic facies) formed contemporaneously under the same wind action.
3.As a fluvial-lacustrine-aeolian-sand sequence found at the Dishaogouwan profile in the Salawusu river area,its climatic records corresponding to that of loess and deep sea deposits,may be divided into 5 climatic periods.It suggests that the climatic change of this region during the last interglacial period is synchronous with that of the whole earth.

1997 Vol. 3, No. 4

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