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2007, Volume 14 Issue 6
20 June 2007 Previous Issue    Next Issue
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A developing plate boundary: Tianshan-Baykal active tectonic belt 2007, 14(6): 1-17.  Abstract ( 6566 )   PDF   It is obvious that a great amount of strong earthquakes in central Asia occurred densely along Tianshan-Baykal belt; however, none huge continuous fault has been revealed on the surface along the belt. It caused academic argument related to their relationship. The authors analyzed its seismic activity in terms of seismicity in time-space domain, zoning feature, stress field, and recurrence period of earthquakes. In addition, we studied the Bouguer gravity and isostatic anomaly, and calculated the distributi... Related Articles | Metrics

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Continental breakup and evolution of rifted volcanic margins 2007, 14(6): 18-25.  Abstract ( 2431 )   PDF   Volcanic rifted margins are a kind of continental margin formed during continental breakup. Their geodynamic evolution is as complex as that of active margins. Through the study of continental breakup and evolution of passive margins in recent years, the recognition of these margins has greatly improved knowledge of their sedimentary process, magmatism and metamorphism. Several models have been proposed for continental breakups. The asymmetry simple shear model may explain the genesis of volcanic rifted mar... Related Articles | Metrics

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Evidence for coalescing of extensional detachment and magma diapirism during uplift of the Yunmengshan metamorphic core complex 2007, 14(6): 26-39.  Abstract ( 1831 )   PDF   The uplift of the Yunmengshan metamorphic core complex in the Beijing region in the Cretaceous period was associated with a detachment southwards along the Sihetang shear zone and the emplacement of a large granodiorite batholith in an early stage. Subsequent deformation mainly occurred along the margins of the granodiorite batholith and its host rocks to form the Yunmengshan ductile shear zone, where abundant syntectonic granite and pegmatite veins injected into a mylonite zone. All of the veins in the she... Related Articles | Metrics

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Rotation of crustal blocks as an explanation of Oligo-Miocene extension in Southeastern Tibet—evidenced by the Diancangshan and nearby metamorphic core complexes 2007, 14(6): 40-48.  Abstract ( 2564 )   PDF   The Diancangshan (DCS) metamorphic core complex (mcc) along the Red River Fault Zone (RRFZ) is an incomplete mcc composed of two units with distinct characteristics, i.e. a lower plate of amphibolite grade tectonites intruded by synkinematic monzogranite, and a greenschist grade detachment fault zone. Lower plate rocks possess high temperature (high-T) structures and L or LS mylonites with left-lateral strike-slip shear sense. The detachment fault zone is a low temperature (low-T) shear zone with top to th... Related Articles | Metrics

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The Maximum Effective Moment Criterion (MEMC) and related geological structures 2007, 14(6): 49-60.  Abstract ( 2233 )   PDF   The Mohr-Coulomb criterion has been widely used to explain the formation of fractures. However, it fails to explain large strain deformation that widely occurs in nature. There is presently a new theory, the MEMC, which is mathematically expressed as Meff=0.5 (σ1-σ3) L·sin 2α·sin α, where σ1-σ3 represents the yield strength of the related rock, L is a unit length and α is the angle between σ1 and deformation bands. This criterion demonstrates that the maximum value appears at angles of ±54.7° to σ1 and ther... Related Articles | Metrics

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Significance of a basic rheological model in geology and its application 2007, 14(6): 61-65.  Abstract ( 2293 )   PDF   Rock deformation in earth is a typical rheological process, during which large strain could occur within rock when it suffers small stress for a long-term. Generally, outcrop of many rocks in the field could be the best examples of rheological deformation occurred during geological time. Rheology has been rapidly developed in the area of mechanics since it was established in the late 19th century. Unfortunately, only a few publications applying rheological theory to geology could be found in the literature.... Related Articles | Metrics

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The Third Editorial Committee of Earth Science Frontiers A BRIEF INTRODUCTION TO OVERSEA MEMBERS OF THE EDITORIAL BOARD 2007, 14(6): 65-65.  Abstract ( 1747 )   PDF   (1)Dr .El-Sayed Mohamed Abdelrahman Professor of Geophysics ,Cairo University ,Egypt . His pri mary researchinterests are poten-tial field methods . His research has focused on gravity , magnetic ,self-potential methods including depth and shape determination . He hasbeen awarded 5 prizes between 1992 and 2003 ,including the state prize in Earth sciences ,the state prize in advanced technological sciencesand the others . (2)Dr . Norman Bleistein Emeritus Professor of Geophysics ,Colorado School of Mines , U... Related Articles | Metrics

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Theory and application of tri-shear fault propagation folding 2007, 14(6): 66-73.  Abstract ( 2742 )   PDF   The fold geometry formed by propagation of basement fault into sedimentary cover is quite difficult to explain based on parallel folding theory owing to the marked rheological difference between the basement and the sedimentary cover. Erslev put forward a theory called the tri-shear fault propagation folding, which holds that the strong brittle deformation of underlying fault is accommodated by a triangular-like widening-upward distributional shear zone, and the triangle apex is pinned to the fault tip. Har... Related Articles | Metrics

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The role of olistostrome in thrusting—a case study from the Miboshan Formation of Middle Ordovician in the Niushou Mountain, Ningxia 2007, 14(6): 85-95.  Abstract ( 1823 )   PDF   Olistostromes are common in the Middle Ordovicianstrata in the central-southern Ningxia Province. These olistostrome may have become decollements during later thrusting. Based on the sedimentary and later deformation characteristics of these olistostromes in the Miboshan Formation, we suggest that these olistostrome played an important role in the thrusting process. The development of a decollement during thrusting is commonly related to the rheology of the rocks. Because olistostromes possess, not only a m... Related Articles | Metrics

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The characteristics of intra-continental deformation and hydrocarbon distribution controlled by the Himalayan tectonic movements in China 2007, 14(6): 96-104.  Abstract ( 1684 )   PDF   Based on previous studies and the latest insights from recent petroleum exploration programs, we propose that the characteristics of intra-continental deformation and its distribution, caused by the Himalayan tectonic movements, are controlled by basement framework formed by a collage of microcratons and lithotectonic terranes and dynamic factors such as the Indian/Eurasia collision and subduction of the Pacific plate. The evolution of Himalayan tectonic movements can be resolved by three principal dynamic ... Related Articles | Metrics

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The shortening process and closure of a continental basin: a case study of the Tarim basin, Northwest China 2007, 14(6): 105-113.  Abstract ( 2427 )   PDF   The Tarim basin is the largest Cenozoic sedimentary depression north of the Tibet plateau. The Tarim basin is surrounded by Cenozoic intraplate orogenic belts. Contrasting with the spectacular uplift and spreading of the Tibet plateau, the relatively strong Tarim block generally has undergone little internal deformation during Cenozoic orogenic movements. The tectonic boundaries of Tarim basin show clear cutting or transfer relationships. Major fractures and marginal thrust and strike-slip fault systems cha... Related Articles | Metrics

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Comparative study of the foreland thrust belts of South and North Tianshan and implications for hydrocarbon accumulation 2007, 14(6): 123-131.  Abstract ( 2182 )   PDF   The Kuqa foreland developed in southern margin and rümqi foreland on the northern margin of the Tianshan orogen. There are four zones of fold-and-thrust belts on the southern margin and three on the northern margin. Comparative studies about the timing between the southern and northern foreland thrust belts indicate that the first structural belt in the southern margin of Tianshan began about 23.3 Ma ago and that the deformation propagated from north to south; whereas the first structural belt in the north... Related Articles | Metrics

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New viewpoints of the primary migration of oil and gas 2007, 14(6): 132-142.  Abstract ( 1733 )   PDF   The present paper deals with the driving mechanism of primary migration of oil and gas based on the fundamentals of flow mechanics in porous media. The main conclusions are as follows. Oil and gas flow out of source rocks as a continuous phase of oil and gas, but not as a water solution of oil and gas or as diffusion. Buoyancy is the main driving force for the primary migration, and the direction of flow is upward. The time necessary for primary migration to occur is related to the permeability of source ro... Related Articles | Metrics

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Discussion on basic styles and mechanism of petroleum fluid migration in the Junggar Basin 2007, 14(6): 143-150.  Abstract ( 2304 )   PDF   In the Junggar Basin, petroleum generally migrates along reservoir rocks (including unconformity) and faults. In this paper, the basic styles and mechanism of petroleum migration were analyzed, based on organic-inorganic interaction during hydrocarbon formation and evolution. It is shown that in reservoir rocks, based on the characteristics of petro-fluid, oil-gas migration styles vary in mechanical-solution and mechanical characteristics, respectively. The factors controlling this fluid heterogeneity inclu... Related Articles | Metrics

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Pre-Mesozoic basement provenance tracing of the Songliao Basin by means of detrital zircon SHRIMP chronology 2007, 14(6): 151-158.  Abstract ( 2240 )   PDF   In the southeast uplift of the Songliao Basin, the basement develop para-rock widely. In this paper, we obtain extensive age range from 406 Ma to 2 208 Ma from 3 para-rock samples by means of detrital zircon SHRIMP chronology, which suggests that the basement of the Songliao Basin has complex provenance. Combined with previous studies, we suggest that the 1 100-2 200 Ma zircons perhaps originate from the China North Craton, while the zircons of 520 Ma may stem from Jiamusi massif. Besides, the samples petr... Related Articles | Metrics

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Method of early prediction on source rocks in basins with low exploration activity 2007, 14(6): 159-167.  Abstract ( 2055 )   PDF   Low exploration activity fields (deep formation, deep water and new exploration areas) are important for petroleum exploration. Source rock evaluation, the result of which will determine the exploration potential of a basin, is one of the most important aspects. Because all the evaluation parameters are almost unknown in an area of low exploration activity with sparse wells, the early evaluation of source rock is somewhat contradictory. Based on the framework of sequence stratigraphy, this paper presents a ... Related Articles | Metrics

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The mechanism of the southern Junggar Cenozoic thrusts 2007, 14(6): 168-174.  Abstract ( 2052 )   PDF   There are three east-west trending thrust-fold belts along the southern flank of the Junggar basin, western segments of each thrust fold belt, which are connected with the north Tianshan Piedmont fault, began forming in the middle Miocene; with the main thrust fold belts beginning forming in the late Miocene, about 10 Ma B.P. The east terminations of the thrust fold belts were formed in the Quaternary. This timing indicates the northward transportation of compressional tectonic dynamics. The initial formati... Related Articles | Metrics

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Apatite fission track thermochronology of Cenozoic exhumation in Larsemann Hills, East Antarctica 2007, 14(6): 175-188.  Abstract ( 2544 )   PDF   The Cenozoic rifting and exhumation is very common in West Antarctica and Transantarctic Mountains, though it is rarely documented from East Antarctica. However, based on apatite fission track ages and thermal histories modeled for samples from Larsemann Hills, Prydz Bay, East Antarctica, we conclude that the Cenozoic uplifting and extension may have occurred in the coastal edge of East Antarctica, at 49.8±12 Ma, which is later than the onset of the rifting system (~60-50 Ma), developed in West Antarctica. ... Related Articles | Metrics

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What happened on the upstream of Minjiang River in Sichuan Province 20 000 years ago 2007, 14(6): 189-196.  Abstract ( 2186 )   PDF   A huge natural paleo-dammed lake deposit named “Diexi paleo-dammed lake” in Diexi ancient county was discovered in 1999. It is situated above the basin of the upper Minjiang River in Sichuan Province, China. The thickness of this lacustrine deposit is variable, reaching up to 200 m at some locations. Carbon-14 chronology has shown that this lacustrine deposit was formed about 20 000 years ago. Subsequently, other smaller paleo-dammed lake deposits have been discovered downstream of the Diexi area above the ... Related Articles | Metrics

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Major elements composition and provenance analysis in the sediments of the South Yellow Sea 2007, 14(6): 197-203.  Abstract ( 1941 )   PDF   Based on the major elements abundances of sediment samples from 295 stations in the South Yellow Sea, we have conducted the R-mode cluster analysis and R-mode factor analysis of major elements in the sediments and their relationship with the sources. Al2O3,MgO,K2O and Fe2O3 have similar distributions, whereas SiO2 is negatively correlated with these oxides. The distributions of CaO and CaCO3 in the central and western areas of the South Yellow Sea indicate a clear link with source materials related to the Y... Related Articles | Metrics

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Marine foraminiferal δ~(11)B and reconstruction of atmospheric pCO_2 2007, 14(6): 204-214.  Abstract ( 1965 )   PDF   Atmospheric pCO2 regulates the global climates on both short-and long-term timescales. Knowledge of evolution of atmospheric pCO2 in the past would provide a potential possibility to predict changes in the future. An increasing number of studies have shown that marine foraminiferal δ11B has great potential to be a reliable palaeo-pH proxy, hence, allows reconstructions of the atmospheric pCO2. In this paper, we firstly reviewed on the boron isotopes in marine foraminifers, as well as the basis of the boron ... Related Articles | Metrics

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Genesis of underwater shrinkage cracks and geological models of their filling 2007, 14(6): 215-221.  Abstract ( 1753 )   PDF   Based on field measurements and experimental analyses of underwater shrinkage cracks, we discuss formation processes of the cracks, sedimentary models of their filling, factors that influence them. and propose theoretical models. There are four steps that lead to the formation of cracks: (1) the primary muddy state of underwater sediments in low-lying areas; (2) sedimentary compacting processes; (3) the forming of shrinkage cracks after falling water levels and increasing salinity; (4) the filling of cracks... Related Articles | Metrics

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Response of karstification to land-use types in mountain area—a case study of the karst areas in Bitan and Shuifang springs in Jinfo Mountain, Chongqing, China 2007, 14(6): 222-230.  Abstract ( 1871 )   PDF   Previous studies on karst processes were always focused on karstification intensity and its variation under different geological settings, climatic and hydrologic conditions in the view of macro scale, and considering changes of CO2 density driving karst processes in a certain area, or the contribution of carbonate rock weathering to the atmospheric CO2. Less attention was paid to the impact of land-use types on karst processes in mountain area. It has been recognized that intensity of karst processes could... Related Articles | Metrics