2007 Vol. 13, No. 1

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SAND GRAINS CANNOT "FLY FAR AND HIGH"———A BASIC PRINCIPLE ABOUT "DUST STORMS"
ZHANG Hong-ren
2007, 13(1): 1-6.
Abstract (264) HTML (202) PDF (186KB)(7)
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Sand and dust are both products of physical weathering.However, their behaviors are entirely different in the eolian transport process.A rigorous physical test performed by Bagnold proved that dust can fly up to 3000 m high over great distances with wind, while sand grains can move at most by means of saltation near the land surface.All the so-called "sand-dust storms" that attack the North China plain from the north are essentially dust storms.Analysis of sediments deposited in various major weather events also confirms the conclusion.Therefore the sources of dust storm materials are not areas with sand but areas with dust.This study may help people take correct methods for remediation of effects of dust storms.
AN APPROACH TO THE STUDY OF COAL AND GAS OUTBURSTS
SUN Ye, TAN Cheng-xuan, SUN Wei-feng, WANG Rui-jiang, WU Shu-ren, CHEN Qun-ce
2007, 13(1): 7-14.
Abstract (3933) HTML (98) PDF (278KB)(20)
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The overlapping of tectonic stress, rock mass energy concentration and mining-induced stress is the basic cause for coal andgas outbursts.Coal and gasoutbursts, which are one of the manifestations of present tectonic activities and induced by crustal instability, belong to the research content of geomechanics.It is a good way to explore the basic idea of prevention and reductionof hazards caused by coal and gas outbursts by using the experience in seismogeological work initiated by Prof.J.S.Lee for reference, beginning with the study of present active tectonic systems and using the methodology and technology of rock mechanics and tectonic stress field, combined with the practice and experience of crustal stability assessments.
RISK ANALYSIS AND PREDICTION OF EARTHQUAKES IN THE CONSTRUCTION AREA OF THE WEST LINE OF THE SOUTH-TO-NORTH WATER DIVERSION PROJECT
PENG Hua, MA Xiu-min
2007, 13(1): 15-24.
Abstract (258) HTML (85) PDF (516KB)(8)
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The paper discusses the distinguishing features of earthquake activities in the construction area of the west line of the project of water diversion from the upper Yangtze River in the south to the upper Yellow River in the north.According to these features, by using the regional earthquake data and statistical method, the characteristics of temporal-spatial distribution of earthquakes occurring in the area are discussed, and in addition, the possibility of occurrence of earthquakes in the area in the future is predicted.
LATITUDINAL CONVERGENCE OF THE ASIAN CONTINENT, RISE OF THE QINGHAI-TIBET PLATEAU AND EXPANSION OF THE EAST ASIAN CONTINENT
LI Shu-jing
2007, 13(1): 25-30, 50.
Abstract (140) HTML (43) PDF (299KB)(14)
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The tectonic problem of East Asia is one of the focuses of the world's concern. In East Asia stand two magnificent plateaus —the Mongolia Plateau and Qinghai-Tibet Plateau —and between the two plateaus lie E-W-trending modern mountain systems such as the Tianshan-Yinshan and Kunlun-Qinling mountain systems, which consist of a series of shear-overthrusting tectonic systems, powerfully suggesting the occurrence of strong latitudinal convergence in the East Asian continent. East of the aforesaid region the general tectonic features show trends of expansion and divergence toward the SE. Southward they reach the Indonesia Islands south of the equator and eastward they might involve the Mariana island arc. A series of arcuate structures are tectonic belts formed by frontal compression, overthrusting, uplift and thickening of the overthrusting-extensional slabs and behind these arcuate structures there usually occur extensional and detachment-subsidence and thinning basins, which show the directions of movements of the continental crustal surface. The present tectonic features of the East Asian continent are the product of the Himalayan movement since the Cenozoic and this process is now still going on. It not only has exerted important influence on the geological structure and tectonics, distribution characteristics of earthquakes and resources and environmental problems, but also are closely related to the formation of the atmospheric circulation and climatic and environmental changes.
3D MODEL OF REVERSED S-SHAPED OROGENIC BELTS ON THE CONTINENTAL MARGIN : WITH A DISCUSSION OF THE INTERNAL STRUCTURE AND UPLIFT OF THE QINGHAI-TIBET PLATEAU
LI Dong-xu
2007, 13(1): 31-41.
Abstract (220) HTML (74) PDF (417KB)(8)
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According to the tectono-geomorphological features and characteristics of neotectonic movement on the southwestern margin of the North American continent, the author has established a 3D tectonomechanic model of the reversed S-shaped continental-margin orogenic belt of the northern hemisphere. This zigzag orogenic belt extends from Alaska through the Cordillera to the Caribbean and may be divided into three sections :(1)the Alaska region, which, as a head arc, is an arcuate dextral shear uplifted orogenic belt; (2)the Cordillera orogenic belt, which as a middle section, is a straight dextral strike-slip orogenic belt; and(3)the region from south of the Madre Mountains to the Caribbean Sea, which, as a tail arc, is a sinistral transrotational " trench-arc-basin system". The author used this model to check the orogenic belts on the southern margin of the Eurasian continent and ascertained that the zigzag mountain chain from the Alps through Zagros and Himalaya to Indonesia is composed of four connected reversed S-shaped orogenic belts. The cause for their decomposition into four separate tectonic systems is related to the breakup of the supercontinent Gondwana in the southern hemisphere. According to the above-mentioned regional tectonic characteristics, the author thinks that the original internal structure of the Qinghai-Tibet Plateau was a transrotational trench-arc-basin system, belonging to the tail arc of the Pamir-Karakorum-Himalaya reversed S-shaped orogenic belt.Later it underwent the superimposition of two dynamic systems, the subduction of the Indian plate and the dextral shear and uplift of the head arc of the Qinghai-Tibet-Sanjiang-Indonesia reversed S-shaped orogenic belt.
CRETACEOUS DENUDATION OF THE ILI BASIN AS REVEALED BY FISSION-TRACK THERMOCHRONOLOGY
GONG Hong-liang, CHEN Zheng-le, HU Yuan-qing, LI Li, Li Sheng-xiang, ZHENG En-jiu, HAN Xiao-zhong
2007, 13(1): 42-50.
Abstract (142) HTML (61) PDF (397KB)(7)
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The fission-track dating method has been widely used to constrain the exhumation of mountains and tectono-thermal evolution of basins.This paper mainly presents the results of apatite fission-track dating and discusses the Mesozoic uplift-denudation event in the Ili basin.Fission-track dating revealed that the fission-track ages of three sandstones from drilling wells at the south margin of the basin are 112.6±9, 79.3±11.4 and 94.0±7.4 Ma respectively, and that the corresponding fission track lengths are 13.45±0.17, 13.15±0.16 and 13.17±0.17μ m respectively with a single peak distribution pattern.Further temperature-time modeling of apatite was conducted using the apatite fission track solution program after the model of Ketcham, based on measurements of the fission-track lengths and pooled ages.The results show that one important uplift-denudation and cooling event took place in the Ili basin at 115-95 Ma.This cooling event is fairly consistent with the absence of Upper Jurassic Lower Cretaceous strata in the basin, suggesting the uplift and subsequent denudation of the Ili basin during this period of time.The coexistence of the single apatite fission-track ages older and younger than the sedimentation age indicates that the apatite fission track was partially annealed after sedimentation as response to the temperature increase resulting from the burial.Supposing that the geothermal gradient is 30 ℃/km and that the temperatures of the partial annealing zone of apatite fission track vary from 80 ℃ to 120 ℃, it can be estimated that the samples were buried at~2.6-4 km depth and that at least at least 1.8- km-thick material has been denuded with a denudation ratio of 0.09mm/a during the Mid-Late Cretaceous (115~95Ma).Correlation and analysis of regional data suggest that the Mid-Late Cretaceous uplift and denudation event was widespread in the whole Tianshan Range and even the whole orogenic belt in northern Xinjiang.
SEQUENCE STRATIGRAPHY AND PETROLEUM ACCUMULATION IN FORELAND BASINS
LIU Gang, DONG Shu-wen
2007, 13(1): 51-59.
Abstract (150) HTML (90) PDF (321KB)(8)
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From a tectonic point of view, foreland basins related to plate collision are areas favorable for petroleum accumulation.Collision of two plates form a series of orogenic belts, while foreland basins tend to form in the fronts of relatively stable plates.The characteristics of foreland basins make them favorable for petroleum generation, migration, accumulation and preservation.Foreland basins are one of the basins endowed with the most abundant petroleum in the world.Sequence stratigraphy of foreland basins is a special branch of applying the theory of sequence stratigraphy to fold belts and foreland basins, assuming that the material supply is stable and that the change in accommodation space of a foreland basin is controlled by structural effects and global sea-level change.Through summarizing stratigraphic sequences and cycles of different orders and their origin, the authors have revealed the inherent relationship of tectonic movement of orogenic belts, basin sedimentation and sea-level change and further studied the sedimentary-tectonic evolution of foreland basins.In addition, they propose that:the petroleum potential of foreland basins mainly depends on the devolopment degree of the early-formed passive margins and preservation conditions of petroleum; thin-skinned overthrust belts have fairly good petroleum potential; foreland basins have many types of traps; and the late-stage front sediments of basins is advantageous to burial, maturation and preservation of early-stage sediments.The four conclusions about the relationships between foreland basins and petroleum provide a theoretical basis for petroleum exploration.
SEQUENCE STRATIGRAPHY OF THE BAYAN QAGAN SUBBASIN IN THE EREN BASIN AND APPLICATIONS FOR PETROLEUM EXPLORATION
LI Jin-liang, FAN Tai-liang, ZHANG Yue-qiao
2007, 13(1): 60-69.
Abstract (179) HTML (106) PDF (563KB)(8)
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Based on an analysis of well-log data and seismic profiles, the authors have identified the main sequence boundaries in the Bayan Qagan subbasin of the Eren basin, established the sequence stratigraphic framework of the subbasin and described the types of sedimentary facies and their plan distribution and constructed a sedimentary facies model of this half graben.According to the features of the source-reservoir-cap rock assemblage, the authors predict that:the Tengger Formation (sequence Ⅲ) and the first member of the Duhongmu Formation (sequence Ⅳ)are the favorable target zones for petroleum exploration, the fluvial sand bodies along the southern gentle slope and alluvial fan deposits along the northern steep slope are the favorable reservoir zones for hydrocarbon accumulation and the Da'erqi fault-block and Sanghe district are favorable blocks for hydrocarbon accumulation.
ANALYSIS OF HIGH-RESOLUTION SEQUENCE STRATIGRAPHY AND STUDY OF DEPOSITIONAL SYSTEMS IN THE MALING OIL FIELD, ORDOS BASIN
WANG Chun-yu, ZHANG Zhi-guo, LI Zhao-ming, ZHANG Lin-yan, ZHANG Hong-bin, YANG Zhi-guo
2007, 13(1): 70-77, 96.
Abstract (212) HTML (106) PDF (440KB)(6)
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Based on the theory of base-level cycles, two long-term, six medium-term and twenty-seven short-term cyclic sequences can be distinguished in the Jurassic Yan'an Formation and Fuxian Formation in the Maling oil field, Ordos basin.This paper introduces in more detail the controls of the base level on sedimentary facies.The change in base level of the long-term cycles may affect and control the types, development scales and facies association patters of streams, and the ascending half and descending half of the medium-term cycle may give rise to the same type of fluvial facies.On the basis of an analysis of cores, well records, well logs and single-well facies, three types of sediments, namely, the sediments of braided streams, meandering streams and anastomosed streams, are distinguished in this area.
LATE QUATERARY NEOTECTONIC MOVEMENT OF THE JIAYUGUAN FAULT
CHEN Bai-lin, LIU Jian-sheng, ZHANG Yong-shuang, LIU Jian-min
2007, 13(1): 78-85.
Abstract (128) HTML (117) PDF (401KB)(19)
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The Jiayuguan active fault is situated near Jiayuguan City.It is closely related to the Jiayuguan-Wenshushan uplift (which is one of the three uplifts in the Hexi Corridor:the JiayuguanWenshushan uplift in the western part of the Hexi Corridor, Yumushan uplift in the central part of the Hexi Corridor and Dahuangshan uplift in the eastern part of the Hexi Corridor)and is also a component part of the northern Qilian marginal-Hexi Corridor active fault system.The fault strikes N320°W and extends linearly for 20 km.It cuts the pre-Cretaceous, Cretaceous, Neogene and upper Pleistocene.In section, the southwestern block of the fault moves up, while the northeastern block moves down; in plan, it is marked by apparent right-lateral strike-slip motion.Five phases of neotectonic movement took place along the Jiayuguan fault during the latest Pleistocene to Holocene, i.e.at 4.3-4.5, 12.9-14.0, 20.0-23.2, 35.5-45 and 58.1 ka BP.The faulting was dominated by stick-slip movement and shows the distinctive characteristics of paleoearthquakes.
CHARACTERISTICS OF CENOZOIC FAULT ACTIVITIES IN THE HUIMIN SUBBASIN
WANG Shu-bao, ZHONG Jian-hua, CHEN Zhi-peng
2007, 13(1): 86-96.
Abstract (126) HTML (61) PDF (519KB)(8)
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The parameters of Quaternary fault activities such as the growth index, fault throw and fault activity rate are calculated to analyze the characteristics of fault activities in the Huimin subbasin and four orders of subbasin-controlling faults are distinguished.The analysis indicates the following:the fault activity rate is the most representative parameter; the fault activities in the Huimin subbasin have the long-continued, differential and episodic characteristics; and the activities of faults of lower orders have the short-term and uncertain characteristics.The subbasin-controlling faults of four orders played different roles in the formation of the subbasin and local structures within the subbasin.