Continuous precipitation was sampled at several stations in the southern Tibetan plateau to study the variation of stable isotope in precipitation. Our work shows that there is a strong signal of monsoon precipitation...Continuous precipitation was sampled at several stations in the southern Tibetan plateau to study the variation of stable isotope in precipitation. Our work shows that there is a strong signal of monsoon precipitation in the stable isotope of precipitation, which is quite different from that in other regions in the Tibetan plateau. The spatial variation, the seasonal variation of δ 18 O and the relationship between δ 18 O in precipitation and local meteorological parameters are all affected by monsoon precipitation in the south of Tibetan plateau.From the spatial variation, precipitation samples were collected from a dozen stations from south to north of the Tibetan plateau. A strong spatial variation of stable isotope in precipitation has been found. Extremely low value of δ 18 O in precipitation in the south of Tibetan plateau can be seen which can be contributed to the monsoon precipitation in the south of Tibetan plateau. The strong precipitation in the south slope of Himalayas Mts. depleted heavily the heavy stable isotope which resulting in very low δ 18 O in precipitation in the south of Tibetan plateau. This work also shows that the monsoon precipitation can affect effectively as far as to the Tanggula Mts. in the middle of the Tibetan plateau.展开更多
In south\|eastern margin of Tibetan plateau, the Western Yunnan area of China, the NNW\|striking faults are dominant active structures. Their dextral strike\|slips cause conjugate slips along NE\|striking faults, and ...In south\|eastern margin of Tibetan plateau, the Western Yunnan area of China, the NNW\|striking faults are dominant active structures. Their dextral strike\|slips cause conjugate slips along NE\|striking faults, and these left shears induce blocks’ clockwise rotations along vertical axes. For example, Simao Block in the south part of Western Yunnan is bounded by Red River Fault (east), Lancang—Gengma Fault (west), Nandinghe Fault (north), and Dian Bien Phu Fault (south); and the right shears of Red River Fault and Lancang—Gengma Fault induced conjugate left shear along Nandinghe Fault and Dian Bien Phu Fault, and laters’ sinistral slips caused clockwise rotation of the Block. This rotation has been proved by geodetic measurements (Jiang, et al., 1993) and palaeomagnetic measurement (Wu, et al., 1987). In Pu’er area, which is located in the central part of Simao Block, several small\|scale blocks are clockwise rotated by sinistral shears of NE\|striking faults (Wang Yang, 1996). Block rotation along vertical axis is main active deformation style in Western Yunnan.展开更多
Since 1996, a regional GPS network has been established along the northern Tibetan Plateau and its neighboring foreland, and has been measured for the period 1996\|1998.* Viewed relative to Chengdu (CHDU fiduciary sta...Since 1996, a regional GPS network has been established along the northern Tibetan Plateau and its neighboring foreland, and has been measured for the period 1996\|1998.* Viewed relative to Chengdu (CHDU fiduciary station representing the stable South China), stations of the northern plateau bounded by the Qilian Shan and the Altyn Tagh fault, move NE to NNW with 20 5～11 7mm/a, and NE to NNE with 10 5～1 5mm/a in its foreland. Addition, the Lhasa (LHAS tracking station in the southern Tibetan Plateau) moves NNE at 23 1mm/a related to CHDU. Especially interestingly, the velocities and the directions of motion vectors of stations in the northern Tibetan Plateau decrease progressively and deflect systematically westward from south to north, respectively. More, the tangents of motion vectors of stations converge around a point near the central of Qaidam Basin except the GLM station at Golmud. We, therefore, find that the general vortex feature of the crust motion appears on the velocity field in the northern Tibetan Plateau. And the anti\|clockwise vortex motion is restricted by block boundaries within the plateau, and also involved the related forelands for example HCY station (Jianyuguan) at the Hexi Corridor.展开更多
Qaidam basin is located at northeast Qinghai—Xizang (Tibet) plateau, and surrounded by east Kunlun, south Qilian and Altun mountain systems. The purpose of this paper is to study the Cenozoic basin evolutionary stage...Qaidam basin is located at northeast Qinghai—Xizang (Tibet) plateau, and surrounded by east Kunlun, south Qilian and Altun mountain systems. The purpose of this paper is to study the Cenozoic basin evolutionary stages, structural styles of the Qaidam, and the denudation in adjacent mountain systems through seismic profile interpretation and complemented by field observation. The Qaidam basin has experienced two tectonic stages of Paleogene—early Miocene (65～12Ma) and late Miocene—present (12～0Ma). The former is characterized by differential uplift of the mountains and subsidence of the basin, and the latter by intense compression, wrench, thrusting and folding. The compressional structural styles are mainly distributed in the Circle Hero—Range Depression of southwest Qaidam, such as Nanyishan, Youquanzi, Younan, Youshashan anticline belts and thrust faults. The wrench structural styles of the northern Qaidam include en echelon uplifts (fault—block outcrops) such as Seshitengshan, Luliangshan, Xitieshan and Eimnikshan, which are mainly composed of pre\|Sinian and Paleozoic rocks; en echelon anticlines such as Lenghu—Nanbaxian belts; and en echelon depressions such as Kunteyi, Senan and Yibei depressions, which are mainly composed of Mesozoic and Cenozoic rocks.展开更多
The Tibetan Plateau is located in the east part of the Tethys realm which is the largest oil and gas accumulation region of the world.The Gangba Basin, located on the south of Tibetan Plateau,is a Mesozoic marine petr...The Tibetan Plateau is located in the east part of the Tethys realm which is the largest oil and gas accumulation region of the world.The Gangba Basin, located on the south of Tibetan Plateau,is a Mesozoic marine petroliferous basin covering an area of 7000 km2.The basin has been received little hydrocarbon interest for its severe climate and life conditions.The Upper Jurassic siliciclastics in Gangba Basin展开更多
The topographic margin of the Tibetan Plateau adjacent to the Sichuan Basin is one of the World’s most impressive continental escarpments, rising from ～600 meters in the basin to peak elevations exceeding 6km across...The topographic margin of the Tibetan Plateau adjacent to the Sichuan Basin is one of the World’s most impressive continental escarpments, rising from ～600 meters in the basin to peak elevations exceeding 6km across a horizontal distance of only 50～60km. Despite this relief, recent geodetic results (King et al., 1997; Chen et al., 1999) indicate that active shortening across this margin of the plateau is <3mm/a, and is within uncertainty of zero. Recent geodynamic models for active deformation in eastern Tibet (Royden et al., 1997) explain this discrepancy as a consequence of flow of lower crust from beneath the central plateau. These models predict relatively high rates of rock uplift in the near absence of horizontal shortening. Rivers along this margin of the plateau are actively incising into bedrock and afford the opportunity to better resolve the distribution of rock uplift along the margin.展开更多
From the planktonic foraminiferal and nannofossil events across the Oligocene/Miocene boundary (OMB) to the major transient glaciation at this epoch boundary,Mi-l,the paleoclimate,stratigraphic and paleontologic event...From the planktonic foraminiferal and nannofossil events across the Oligocene/Miocene boundary (OMB) to the major transient glaciation at this epoch boundary,Mi-l,the paleoclimate,stratigraphic and paleontologic events showed a prominent change across the OMB.However,the previous work was mainly about the marine deposits,especially the ocean drilling data.Whatever,the continental strata,such as the alluvial and lacustrine sedimentation in展开更多
The formation of the Tibetan Plateau is closely related to the evolution of Tethys. There have been many researchers and articles concerning the Tethys since E.Suess proposed the concept in 1893. It means a large ocea...The formation of the Tibetan Plateau is closely related to the evolution of Tethys. There have been many researchers and articles concerning the Tethys since E.Suess proposed the concept in 1893. It means a large ocean which lies between Eurasia and Gondwanaland. With the development of Tethyan research, some new terms, appeared such as Neo\|Tethys, Paleo\|Tethys, and Proto\|Tethys, representing the Tethys in Mesozoic—Cenozoic, late Paleozoic and early Paleozoic respectively. The trace of an ocean from Sinian to Ordovician was discovered during the scientific expedition and Proto\|Tethys was proposed to name the ocean. Therefore, the Tibetan Plateau is the main scope of the Eastern Tethys. It can be divided c losely related into three zones which represent the main oceanic locations in th ree different stages.The Northern Tethyan Region lies in the Kunlun and Qilian Mountains, its remnant is the Fifth Suture Zone. It is also the northern boundary of the Tibetan Plateau The rift initiated after the continental basement had been formed in Sinian and gradually developed into an ocean, which was named Proto\|Tethys, the earliest Tethyan ocean known up to now. The petrochemical compositions of pillow lava in this zone show the characteristics of mid\|ocean ridge tholeiite basalt and the pelagic ophiolitic flysch were well developed, indicating a matured ocean. It was closed in Ordovician and Silurian.展开更多
More and more concentrations have been focused on the uplift of the Tibetan Plateau and its effects on regional and global environment. The development of Asian monsoon has a close relationship with the uplift of the ...More and more concentrations have been focused on the uplift of the Tibetan Plateau and its effects on regional and global environment. The development of Asian monsoon has a close relationship with the uplift of the Tibetan Plateau. The understanding for the development of Asian monsoon is the key to the understanding of the process and the mechanism of the environmental evolution of the Asian region and to the understanding of the history of the uplift of the Tibetan Plateau. It is found that a big change of the Asian monsoon system occurred at about 2 6Ma ago. The winter monsoon strengthened (Ding et al.,1992 ), the change of winter monsoon began to in the opposite phase to the summer monsoon in East Asia (An et al., 1998 ), the tropical Southwest monsoon was hard to influence the North China (Li, 1999). However, whether there were changes in direction of winter monsoon and strength of summer monsoon occurred and how to change are still not clear. In this paper, the changes of the Asian monsoon system at about 2 6Ma ago are discussed, based on the reanalysis and combination of the results of atmospheric simulations and the geological records existed. It is suggested that, at about 2 6Ma ago, both winter monsoon and summer monsoon strengthened obviously, because that the amplitude of the climatic change increased a lot—warmer during the warm periods and colder during the cold periods. The direction of winter monsoon in Northern China changed from North—West—West to Northwest or North—West—North, because that the expansion direction of eolian\|deposit\|distribution area in China changed from mainly eastward to mainly southward. The area influenced by subtropical monsoon increased, but the area influenced by tropical monsoon decreased in China, because of the rising of the Tibetan Plateau and the southwest\|ward migration of the center of the Asian Low. At some time of the Pliocene, the tropical monsoon had penetrated onto the Qinghai\|Xizang region and influenced on the North China and Northwest China. However, after 2.6Ma B.P., the effects of the tropical monsoon on Northwest China and the northern part of the Tibetan Plateau decreased. All these suggest that the Tibetan Plateau perhaps reached about 2000m elevation at about 2 6Ma B.P..展开更多
As one of the most distinct tectonic blocks on the Earth’s surface, Tibetan Plateau draw great attention of the geoscientists from the world. Many authors have proposed various kinds of the mechanism to try to clarif...As one of the most distinct tectonic blocks on the Earth’s surface, Tibetan Plateau draw great attention of the geoscientists from the world. Many authors have proposed various kinds of the mechanism to try to clarify the evolution of the plateau. While many studies are often restricted to crustal units, the important role of the mantle part of the lithosphere (mantle lithosphere) during and after the collision process has not been appreciated widely. The purpose of the paper is to investigate the dynamic process of the thinning (delamination and convective removal) of the thickened lithosphere and its influence upon the uplift of the plateau.1\ Thickened lithosphere root\;Parsons and McKenzie (1978) proposed that the continental lithosphere could be thought of as consisting of two distinct parts: the mechanical and thermal boundary layers. The lower, and hotter, part is the thermal boundary layer. Its viscosity is sufficiently low that the force of gravity acting on density contrasts between the thermal boundary layer and the underlying mantle lead to the episodic sinking of the thermal boundary layer and its replacement by hot asthenosphere. When continental crust shortens and thickens, the mantle directly beneath it must also be displaced downward. In other words, mountain building process shortens horizontally and thickens vertically the mechanical boundary layer, and presumably the thermal boundary layer. And the process stretches the isotherms vertically, thus reducing the geothermal gradient. Houseman’s numerical experiments (1981) show that thickening of the thermal boundary layer enhances the density contrasts between it and the underlying asthenosphere, and so leads to its removal and replacement with hot asthenosphere. This phenomenon is called the instability of the thickened lithosphere.展开更多
The transform fault is essentially a displacement fault whose terminal part is adjusted by other tectonic types, its displacement component is absorbed by other structures intersected with it by high angles or meet at...The transform fault is essentially a displacement fault whose terminal part is adjusted by other tectonic types, its displacement component is absorbed by other structures intersected with it by high angles or meet at right angles. The main elements of transform fault are the sleep\|dipping displacement faults and the adjusted structures intersected with it at high angles. According to the combination of tectonic features formed by its two ends of displacement fault and the structures intersected with it, the transform fault can be divided into three types, including the adjusted transform fault of extensional normal fault, the adjusted transform fault of compressive fold and thrust fault, and the compound transform fault. The transform fault is different from the displacement fault, its horizontal displacement may be increased or decreased or not be changed at all as the time of fault movement extended, but for parallel displacement the dislocation will be increased. Therefore, the study of transform fault is very important for the recognition of long time disputed displacement components of huge displacement fault. The traditional Altyn fault is the adjusting fault of the compression deformation of the Western Kunlun and Northern Qilian mountains of the northern margin of the Tibetan Plateau since Cenozoic.展开更多
The emergence of the Qing—Zang plateau is among the most important geological events on the globe since the Cenozoic Era. Many geological issues can find answer from here. The major issues concerning plateau probably...The emergence of the Qing—Zang plateau is among the most important geological events on the globe since the Cenozoic Era. Many geological issues can find answer from here. The major issues concerning plateau probably have three: (1) geodynamics, timing and speed of the plateau uplift;(2) The plateau uplift impact on surrounding environment;(3) mineral resources in the plateau. The authors want to focuses on first issue based on volcanisms occurred in interior and surrounding of the plateau, The new opinions are following:(1) Each volcanic eruptive episode corresponded to strong uplift stage;(2) The dynamic mechanism of the plateau uplift can not ignore another force from west beyond collision between Indian and Eurasia plates from South;(3) The surrounding volcanic chain is not only related to the collision from South, but also from west.展开更多
The elevation of Qinghai\|Tibetan plateau is a epoch\|making event in the global evolutionary history, which not only constructed the modern magnificent geomorphic feature, but also influenced far\|reachingly the glob...The elevation of Qinghai\|Tibetan plateau is a epoch\|making event in the global evolutionary history, which not only constructed the modern magnificent geomorphic feature, but also influenced far\|reachingly the global climate. The evolutionary models of its uplifting time and scope has been primarily set up, and is waiting to be competed with new discovery and supplement. A comprehensive field geologic excursion on the Cenozoic strata of the Kumukuli basin, Xinjiang, northwest Qinghai\|Tibetan plateau by authors has collected a lot of first\|hand data, and the discovery and dating of the late Pleistocene mammal fossils made an important supplement to the scarcity of late Quaternary fossil recorders in many basins, as well as contributed a great deal to the quantitative study of the researches alike, in the main time, provided new evidences to the uplift of Qinghai\|Tibetan plateau since late pleistocene.Lies in the northwest part of the Qinghai\|Tibetan plateau, and between the Kunlun and Altum Mountain ranges, Kumukuli basin is a intracontinental plateau basin, with a mean elevation about 4000m. Cenozoic strata have a time span from Oligocene to Pleistocene.The stratigraphic and lithologic association displays that the development of Kumukuli basin started at the Oligocene, at the primary uplift stage of the Qinghai\|Tibetan plateau. The Oligocene and Miocene, with a giant thickness and multiple layers of thick conglomerate, is of the products of stronger erosional stage, and a reflection of higher differential in inner geomorphology of the plateau. The aggradation led to the smoothness of the geomorphic feature and fineness of sedimentary particle since Pliocene. Since then, Large scale conglomerate outcroped in the peripheral of the plateau, and differential of geomorphology in the plateau and its peripheral areas became distinct. Kumukuli basin is one of the synchronously developed basin with the plateau, having the most completed Cenozoic sequence with a thickness over 7000m. Its Tertiary sedimentary sequence is basically similar to that of the Ningxia basin, northeastern margin of the Qinghai\|Tibetan plateau, and can be well correlated each other, mutually, they recorded the uplift process of the Qinghai\|Tibetan plateau, and their difference may represent the contrast evolution of the plateau and inhomogeneous differential in geomorphic feature of the plateau and its perimeter respectively. Being two sedimentary basins in separately tectonic units, the former has much thicker strata and coarser particles, for instance, the Oligocene is over 3000m in thickness in Kumukuli basin, however, only about 100m in Ningxia basin. Several uncomformities occurring in Kumukuli basin, namely, between the Quarternary and the Pliocene, the Pliocene and the Middle\|Upper Miocene, as well as the Middle\|Upper Miocene and the Lower Miocene, are the direct effects of horizontal movement accompanied with the process of the uplift of the Qinghai\|Tibetan plateau. Maybe those data imply that the western part of the plateau much stronger in uplift and distinct in horizontal movement than that of the east.展开更多
The southeastern edge of the Tibetan plateau is marked by several thrust sheets trending roughly in E\|W direction. The Yanyuan thrust sheet is bounded by three arcuate thrust belts, marked by high mountain ranges wit...The southeastern edge of the Tibetan plateau is marked by several thrust sheets trending roughly in E\|W direction. The Yanyuan thrust sheet is bounded by three arcuate thrust belts, marked by high mountain ranges with the Jinhe belt on the north, the Qianhe belt on the south and the Ninglang belt on the west. Within the Yanyuan thrust belt are sedimentary cover rocks of the Yangtze platform, with ages ranging from Sinian to Triassic. In the north, the thrust sheet is overlain by the Muli thrust sheet along the Jinhe belt, while in the south, it is underlain by the Kangdian paleoland along the Qianhe belt. The youngest rocks on the foot wall are late Eocene to Oligocene in age, indicating that the thrusting occurred in the late Tertiary. The top of the Yanyuan thrust belt is truncated by a flat erosion surface similar to that on the plateau to the north. Along a north\|dipping normal fault bordering the Yanyuan basin on the south, the erosion surface is tilted to the south against Triassic rocks. The basin is filled with coal\|bearing clastic sediments of Pliocene and early Pleistocene age, which gives the timing of the normal faulting. Based on the faulting pattern, we propose that the southeastern edge of the Tibetan plateau underwent a large amount of N\|S shortening and uplift along the Yanyuan thrust sheet in the late Tertiary, while the subsequent normal faulting that had occurred along the Yanyuan basin during the Pliocene and Pliocene can be interpreted to have accommodated gravitational collapse of the crust.展开更多
We estimated crustal v p/ v s ratio of Tibetan Plateau by combined inversion of Love and Rayleigh wave dispersion data. It is developed by us that the joint inversion methods using both Love and Rayleigh wave dispersi...We estimated crustal v p/ v s ratio of Tibetan Plateau by combined inversion of Love and Rayleigh wave dispersion data. It is developed by us that the joint inversion methods using both Love and Rayleigh wave dispersion data. Thickness and S\|wave velocity of each sub layer are taken from Love wave dispersion data, then P\|wave velocity structure was deduced using Rayleigh wave dispersion data. Densities of sub layers were estimated by the empirical relationships between seismic velocity and rock density. Having S\| and P\|wave velocities, v p/ v s ratio is calculated for each sub layer. Six sub layers in crust of Tibetan Plateau has been identified, which are 0～8km, 8～30km, 30～40km, 40～62km, 62～68km and 68～75km respectively. The S\|wave velocity structure of the Plateau is 3 13, 3 32, 3 15, 3 92, 3 45 and 3 87 km/s for each sub layer; and P\|wave velocities are 6 00, 6 10, 5 72, 6 35, 6 78 and 6 64km/s respectively v p/ v s ratios in sub layers are 1 92, 1 84, 1 82, 1 62, 1 96 and 1 72; and corresponding Poisson ratios are 0 31, 0 29, 0 28, 0 19, 0 32 and 0 24. Our result on Poisson ratios of Tibetan crust was supported by seismic waveform modelling by Rodgers and Schwartz (1998).展开更多
Mt. Yulong, located in the eastern part of Tibetan Plateau, is the southmost present glaciation area both in China and Europe\|Asia continent,where distributes 19 typical sub\|tropics temperate glaciers. In the summer...Mt. Yulong, located in the eastern part of Tibetan Plateau, is the southmost present glaciation area both in China and Europe\|Asia continent,where distributes 19 typical sub\|tropics temperate glaciers. In the summer of 1999, a firn core, 10 10m long to the glacier ice, was successfully recovered in the accumulation area at the largest glacier (No.1 Baishui) on Mt. Yulong. Annual and seasonal variations of different climatic signals above the depth of 7 8m are apparent and five\|year snow accumulation can be clearly identified by the seasonal changes of isotopic and ionic composition, some higher values of electrical conductivity and pH values. These annual boundaries can be also verified by the positions of dirty refrozen ice layers at summer surface of each year. The mean annual net accumulation between the balance years of 94/95 and 97/98 are calculated to about 900mm water equivalent. The amplitude of isotopic changes becomes smaller with the increasing depth of the core and isotopic homogenization occurred below the depth of 7 8m. Concentrations of Ca 2+ and Mg 2+ are much higher than those of Na + and K +, reflecting that the air masses for precipitation came far from their marine sources and passed over a longer continental route. Cl - and Na + show well corresponding variation patterns in the firn profile,indicating their same genesis. Concentrations of SO 2- 4 and NO - 3 are low, reflecting very slight pollution caused by human activities in this area. According to the sum of net income recovered from the firn core and the estimated ablation amount, the average annual precipitation above the equilibrium line is estimated in the scope of 2250mm and 3200mm but it needed to be verified by long\|term observation of mass balance. As indicated by the trend of local climatic changes in last 50years, climatic signals in the firn core and recent observation at the terminal of glacier No.1 Baishui, the glaciers in Mt. Yulong start to advance in 1998 after continuous retreat from early 1980’s to late 1990’s.展开更多
The A’nyemaqen ophiolite belt lies along the northeastern margin of the Tibetan Plateau and is believed to mark the boundary between the East Kunlun terrain and the ayanhar\|Songpan\|Garze terrain (Fig.1). The ophiol...The A’nyemaqen ophiolite belt lies along the northeastern margin of the Tibetan Plateau and is believed to mark the boundary between the East Kunlun terrain and the ayanhar\|Songpan\|Garze terrain (Fig.1). The ophiolite in this belt is considered to be Early Permian to Middle Triassic in age (Yang et al., 1996). Our recent study indicates that there is an old ophiolite suite (>421 5Ma), located to the northern margin of this belt (Fig.1). Since the new found ophiolite is near to the Dur’ngoi deposit, so we called it North Dur’ngoi ophiolite. The geological and geochemical characteristics of the two ophiolite suites are different obviously as follows.展开更多
The development of a plateau is an integral part of the evolution of recent large orogens. This is suggested by the presence of wide regions of high topographic relief in many Phanerozoic collisional belts, with the T...The development of a plateau is an integral part of the evolution of recent large orogens. This is suggested by the presence of wide regions of high topographic relief in many Phanerozoic collisional belts, with the Tibetan, Anatolian, Altiplano and Colorado plateaus forming the most often cited examples. To date, plateaus have not been documented in Proterozoic orogens. However, if large Proterozoic convergent belts developed plateaus, evidence should be preserved in the geologic record.Proterozoic belts expose deeper crustal levels that are not directly accessible in modern analogues. Therefore, if they represent the final product of a plateau style evolution, their study may give direct insight on the nature of the middle to lower crust beneath modern orogenic plateaus. The Grenville Province of the Canadian Shield is a Mesoproterozoic continental collision belt of Himalayan scale that contains various lines of evidence suggesting an early plateau\|type evolution. Here we discuss this evidence and draw comparisons with the prime example of a present day plateau in a continental collision setting, the Tibetan plateau.展开更多
As one of the major projects of GAME (GEWEX Asian Monsoon Experiment), the GAME\|Tibet aimed to mainly examine the energy and water cycle in Tibetan Plateau and its effects on Asian monsoon. In this paper, based on th...As one of the major projects of GAME (GEWEX Asian Monsoon Experiment), the GAME\|Tibet aimed to mainly examine the energy and water cycle in Tibetan Plateau and its effects on Asian monsoon. In this paper, based on the in\|situ high\|resolution observation data of GAME\|Tibet, the soil energy\|moisture distribution and the melting\|freezing progresses and their effects on seasonal shift were preliminarily discussed.The soil energy\|water distribution and freezing\|melting processes varied at different sites in northern part of Tibetan Plateau. The temporal and spatial variation of the soil moisture content is more complex than that of temperature. The soil moisture content increased with depth in certain layers but decreased in other layers. The freezing and melting processes and the temperature distribution were largely influenced by the existence of higher soil moisture content layer. During summer monsoon, the soil moisture at 10cm at all sites is relatively high, but the spatial difference existed. Generally speaking, the shallow layers start to freeze in October and to melt from April at all sites, with about 6 months frozen period. However, the beginning time of freezing\|melting and frozen period varied at different sites.展开更多
文摘Continuous precipitation was sampled at several stations in the southern Tibetan plateau to study the variation of stable isotope in precipitation. Our work shows that there is a strong signal of monsoon precipitation in the stable isotope of precipitation, which is quite different from that in other regions in the Tibetan plateau. The spatial variation, the seasonal variation of δ 18 O and the relationship between δ 18 O in precipitation and local meteorological parameters are all affected by monsoon precipitation in the south of Tibetan plateau.From the spatial variation, precipitation samples were collected from a dozen stations from south to north of the Tibetan plateau. A strong spatial variation of stable isotope in precipitation has been found. Extremely low value of δ 18 O in precipitation in the south of Tibetan plateau can be seen which can be contributed to the monsoon precipitation in the south of Tibetan plateau. The strong precipitation in the south slope of Himalayas Mts. depleted heavily the heavy stable isotope which resulting in very low δ 18 O in precipitation in the south of Tibetan plateau. This work also shows that the monsoon precipitation can affect effectively as far as to the Tanggula Mts. in the middle of the Tibetan plateau.
文摘In south\|eastern margin of Tibetan plateau, the Western Yunnan area of China, the NNW\|striking faults are dominant active structures. Their dextral strike\|slips cause conjugate slips along NE\|striking faults, and these left shears induce blocks’ clockwise rotations along vertical axes. For example, Simao Block in the south part of Western Yunnan is bounded by Red River Fault (east), Lancang—Gengma Fault (west), Nandinghe Fault (north), and Dian Bien Phu Fault (south); and the right shears of Red River Fault and Lancang—Gengma Fault induced conjugate left shear along Nandinghe Fault and Dian Bien Phu Fault, and laters’ sinistral slips caused clockwise rotation of the Block. This rotation has been proved by geodetic measurements (Jiang, et al., 1993) and palaeomagnetic measurement (Wu, et al., 1987). In Pu’er area, which is located in the central part of Simao Block, several small\|scale blocks are clockwise rotated by sinistral shears of NE\|striking faults (Wang Yang, 1996). Block rotation along vertical axis is main active deformation style in Western Yunnan.
文摘Since 1996, a regional GPS network has been established along the northern Tibetan Plateau and its neighboring foreland, and has been measured for the period 1996\|1998.* Viewed relative to Chengdu (CHDU fiduciary station representing the stable South China), stations of the northern plateau bounded by the Qilian Shan and the Altyn Tagh fault, move NE to NNW with 20 5～11 7mm/a, and NE to NNE with 10 5～1 5mm/a in its foreland. Addition, the Lhasa (LHAS tracking station in the southern Tibetan Plateau) moves NNE at 23 1mm/a related to CHDU. Especially interestingly, the velocities and the directions of motion vectors of stations in the northern Tibetan Plateau decrease progressively and deflect systematically westward from south to north, respectively. More, the tangents of motion vectors of stations converge around a point near the central of Qaidam Basin except the GLM station at Golmud. We, therefore, find that the general vortex feature of the crust motion appears on the velocity field in the northern Tibetan Plateau. And the anti\|clockwise vortex motion is restricted by block boundaries within the plateau, and also involved the related forelands for example HCY station (Jianyuguan) at the Hexi Corridor.
文摘Qaidam basin is located at northeast Qinghai—Xizang (Tibet) plateau, and surrounded by east Kunlun, south Qilian and Altun mountain systems. The purpose of this paper is to study the Cenozoic basin evolutionary stages, structural styles of the Qaidam, and the denudation in adjacent mountain systems through seismic profile interpretation and complemented by field observation. The Qaidam basin has experienced two tectonic stages of Paleogene—early Miocene (65～12Ma) and late Miocene—present (12～0Ma). The former is characterized by differential uplift of the mountains and subsidence of the basin, and the latter by intense compression, wrench, thrusting and folding. The compressional structural styles are mainly distributed in the Circle Hero—Range Depression of southwest Qaidam, such as Nanyishan, Youquanzi, Younan, Youshashan anticline belts and thrust faults. The wrench structural styles of the northern Qaidam include en echelon uplifts (fault—block outcrops) such as Seshitengshan, Luliangshan, Xitieshan and Eimnikshan, which are mainly composed of pre\|Sinian and Paleozoic rocks; en echelon anticlines such as Lenghu—Nanbaxian belts; and en echelon depressions such as Kunteyi, Senan and Yibei depressions, which are mainly composed of Mesozoic and Cenozoic rocks.
基金The study was jointly funded by the NSFC(Grant No.90502009,40372085)the CAREERI of CAS(Grant No.2004106)Also this study is supported by the Alexander von Humboldt Foundation.
文摘The Tibetan Plateau is located in the east part of the Tethys realm which is the largest oil and gas accumulation region of the world.The Gangba Basin, located on the south of Tibetan Plateau,is a Mesozoic marine petroliferous basin covering an area of 7000 km2.The basin has been received little hydrocarbon interest for its severe climate and life conditions.The Upper Jurassic siliciclastics in Gangba Basin
文摘The topographic margin of the Tibetan Plateau adjacent to the Sichuan Basin is one of the World’s most impressive continental escarpments, rising from ～600 meters in the basin to peak elevations exceeding 6km across a horizontal distance of only 50～60km. Despite this relief, recent geodetic results (King et al., 1997; Chen et al., 1999) indicate that active shortening across this margin of the plateau is <3mm/a, and is within uncertainty of zero. Recent geodynamic models for active deformation in eastern Tibet (Royden et al., 1997) explain this discrepancy as a consequence of flow of lower crust from beneath the central plateau. These models predict relatively high rates of rock uplift in the near absence of horizontal shortening. Rivers along this margin of the plateau are actively incising into bedrock and afford the opportunity to better resolve the distribution of rock uplift along the margin.
文摘From the planktonic foraminiferal and nannofossil events across the Oligocene/Miocene boundary (OMB) to the major transient glaciation at this epoch boundary,Mi-l,the paleoclimate,stratigraphic and paleontologic events showed a prominent change across the OMB.However,the previous work was mainly about the marine deposits,especially the ocean drilling data.Whatever,the continental strata,such as the alluvial and lacustrine sedimentation in
文摘The formation of the Tibetan Plateau is closely related to the evolution of Tethys. There have been many researchers and articles concerning the Tethys since E.Suess proposed the concept in 1893. It means a large ocean which lies between Eurasia and Gondwanaland. With the development of Tethyan research, some new terms, appeared such as Neo\|Tethys, Paleo\|Tethys, and Proto\|Tethys, representing the Tethys in Mesozoic—Cenozoic, late Paleozoic and early Paleozoic respectively. The trace of an ocean from Sinian to Ordovician was discovered during the scientific expedition and Proto\|Tethys was proposed to name the ocean. Therefore, the Tibetan Plateau is the main scope of the Eastern Tethys. It can be divided c losely related into three zones which represent the main oceanic locations in th ree different stages.The Northern Tethyan Region lies in the Kunlun and Qilian Mountains, its remnant is the Fifth Suture Zone. It is also the northern boundary of the Tibetan Plateau The rift initiated after the continental basement had been formed in Sinian and gradually developed into an ocean, which was named Proto\|Tethys, the earliest Tethyan ocean known up to now. The petrochemical compositions of pillow lava in this zone show the characteristics of mid\|ocean ridge tholeiite basalt and the pelagic ophiolitic flysch were well developed, indicating a matured ocean. It was closed in Ordovician and Silurian.
文摘More and more concentrations have been focused on the uplift of the Tibetan Plateau and its effects on regional and global environment. The development of Asian monsoon has a close relationship with the uplift of the Tibetan Plateau. The understanding for the development of Asian monsoon is the key to the understanding of the process and the mechanism of the environmental evolution of the Asian region and to the understanding of the history of the uplift of the Tibetan Plateau. It is found that a big change of the Asian monsoon system occurred at about 2 6Ma ago. The winter monsoon strengthened (Ding et al.,1992 ), the change of winter monsoon began to in the opposite phase to the summer monsoon in East Asia (An et al., 1998 ), the tropical Southwest monsoon was hard to influence the North China (Li, 1999). However, whether there were changes in direction of winter monsoon and strength of summer monsoon occurred and how to change are still not clear. In this paper, the changes of the Asian monsoon system at about 2 6Ma ago are discussed, based on the reanalysis and combination of the results of atmospheric simulations and the geological records existed. It is suggested that, at about 2 6Ma ago, both winter monsoon and summer monsoon strengthened obviously, because that the amplitude of the climatic change increased a lot—warmer during the warm periods and colder during the cold periods. The direction of winter monsoon in Northern China changed from North—West—West to Northwest or North—West—North, because that the expansion direction of eolian\|deposit\|distribution area in China changed from mainly eastward to mainly southward. The area influenced by subtropical monsoon increased, but the area influenced by tropical monsoon decreased in China, because of the rising of the Tibetan Plateau and the southwest\|ward migration of the center of the Asian Low. At some time of the Pliocene, the tropical monsoon had penetrated onto the Qinghai\|Xizang region and influenced on the North China and Northwest China. However, after 2.6Ma B.P., the effects of the tropical monsoon on Northwest China and the northern part of the Tibetan Plateau decreased. All these suggest that the Tibetan Plateau perhaps reached about 2000m elevation at about 2 6Ma B.P..
文摘As one of the most distinct tectonic blocks on the Earth’s surface, Tibetan Plateau draw great attention of the geoscientists from the world. Many authors have proposed various kinds of the mechanism to try to clarify the evolution of the plateau. While many studies are often restricted to crustal units, the important role of the mantle part of the lithosphere (mantle lithosphere) during and after the collision process has not been appreciated widely. The purpose of the paper is to investigate the dynamic process of the thinning (delamination and convective removal) of the thickened lithosphere and its influence upon the uplift of the plateau.1\ Thickened lithosphere root\;Parsons and McKenzie (1978) proposed that the continental lithosphere could be thought of as consisting of two distinct parts: the mechanical and thermal boundary layers. The lower, and hotter, part is the thermal boundary layer. Its viscosity is sufficiently low that the force of gravity acting on density contrasts between the thermal boundary layer and the underlying mantle lead to the episodic sinking of the thermal boundary layer and its replacement by hot asthenosphere. When continental crust shortens and thickens, the mantle directly beneath it must also be displaced downward. In other words, mountain building process shortens horizontally and thickens vertically the mechanical boundary layer, and presumably the thermal boundary layer. And the process stretches the isotherms vertically, thus reducing the geothermal gradient. Houseman’s numerical experiments (1981) show that thickening of the thermal boundary layer enhances the density contrasts between it and the underlying asthenosphere, and so leads to its removal and replacement with hot asthenosphere. This phenomenon is called the instability of the thickened lithosphere.
基金theNationalNaturalScienceFoundationofChina (No .4 980 2 0 19)
文摘The transform fault is essentially a displacement fault whose terminal part is adjusted by other tectonic types, its displacement component is absorbed by other structures intersected with it by high angles or meet at right angles. The main elements of transform fault are the sleep\|dipping displacement faults and the adjusted structures intersected with it at high angles. According to the combination of tectonic features formed by its two ends of displacement fault and the structures intersected with it, the transform fault can be divided into three types, including the adjusted transform fault of extensional normal fault, the adjusted transform fault of compressive fold and thrust fault, and the compound transform fault. The transform fault is different from the displacement fault, its horizontal displacement may be increased or decreased or not be changed at all as the time of fault movement extended, but for parallel displacement the dislocation will be increased. Therefore, the study of transform fault is very important for the recognition of long time disputed displacement components of huge displacement fault. The traditional Altyn fault is the adjusting fault of the compression deformation of the Western Kunlun and Northern Qilian mountains of the northern margin of the Tibetan Plateau since Cenozoic.
文摘The emergence of the Qing—Zang plateau is among the most important geological events on the globe since the Cenozoic Era. Many geological issues can find answer from here. The major issues concerning plateau probably have three: (1) geodynamics, timing and speed of the plateau uplift;(2) The plateau uplift impact on surrounding environment;(3) mineral resources in the plateau. The authors want to focuses on first issue based on volcanisms occurred in interior and surrounding of the plateau, The new opinions are following:(1) Each volcanic eruptive episode corresponded to strong uplift stage;(2) The dynamic mechanism of the plateau uplift can not ignore another force from west beyond collision between Indian and Eurasia plates from South;(3) The surrounding volcanic chain is not only related to the collision from South, but also from west.
文摘The elevation of Qinghai\|Tibetan plateau is a epoch\|making event in the global evolutionary history, which not only constructed the modern magnificent geomorphic feature, but also influenced far\|reachingly the global climate. The evolutionary models of its uplifting time and scope has been primarily set up, and is waiting to be competed with new discovery and supplement. A comprehensive field geologic excursion on the Cenozoic strata of the Kumukuli basin, Xinjiang, northwest Qinghai\|Tibetan plateau by authors has collected a lot of first\|hand data, and the discovery and dating of the late Pleistocene mammal fossils made an important supplement to the scarcity of late Quaternary fossil recorders in many basins, as well as contributed a great deal to the quantitative study of the researches alike, in the main time, provided new evidences to the uplift of Qinghai\|Tibetan plateau since late pleistocene.Lies in the northwest part of the Qinghai\|Tibetan plateau, and between the Kunlun and Altum Mountain ranges, Kumukuli basin is a intracontinental plateau basin, with a mean elevation about 4000m. Cenozoic strata have a time span from Oligocene to Pleistocene.The stratigraphic and lithologic association displays that the development of Kumukuli basin started at the Oligocene, at the primary uplift stage of the Qinghai\|Tibetan plateau. The Oligocene and Miocene, with a giant thickness and multiple layers of thick conglomerate, is of the products of stronger erosional stage, and a reflection of higher differential in inner geomorphology of the plateau. The aggradation led to the smoothness of the geomorphic feature and fineness of sedimentary particle since Pliocene. Since then, Large scale conglomerate outcroped in the peripheral of the plateau, and differential of geomorphology in the plateau and its peripheral areas became distinct. Kumukuli basin is one of the synchronously developed basin with the plateau, having the most completed Cenozoic sequence with a thickness over 7000m. Its Tertiary sedimentary sequence is basically similar to that of the Ningxia basin, northeastern margin of the Qinghai\|Tibetan plateau, and can be well correlated each other, mutually, they recorded the uplift process of the Qinghai\|Tibetan plateau, and their difference may represent the contrast evolution of the plateau and inhomogeneous differential in geomorphic feature of the plateau and its perimeter respectively. Being two sedimentary basins in separately tectonic units, the former has much thicker strata and coarser particles, for instance, the Oligocene is over 3000m in thickness in Kumukuli basin, however, only about 100m in Ningxia basin. Several uncomformities occurring in Kumukuli basin, namely, between the Quarternary and the Pliocene, the Pliocene and the Middle\|Upper Miocene, as well as the Middle\|Upper Miocene and the Lower Miocene, are the direct effects of horizontal movement accompanied with the process of the uplift of the Qinghai\|Tibetan plateau. Maybe those data imply that the western part of the plateau much stronger in uplift and distinct in horizontal movement than that of the east.
文摘The southeastern edge of the Tibetan plateau is marked by several thrust sheets trending roughly in E\|W direction. The Yanyuan thrust sheet is bounded by three arcuate thrust belts, marked by high mountain ranges with the Jinhe belt on the north, the Qianhe belt on the south and the Ninglang belt on the west. Within the Yanyuan thrust belt are sedimentary cover rocks of the Yangtze platform, with ages ranging from Sinian to Triassic. In the north, the thrust sheet is overlain by the Muli thrust sheet along the Jinhe belt, while in the south, it is underlain by the Kangdian paleoland along the Qianhe belt. The youngest rocks on the foot wall are late Eocene to Oligocene in age, indicating that the thrusting occurred in the late Tertiary. The top of the Yanyuan thrust belt is truncated by a flat erosion surface similar to that on the plateau to the north. Along a north\|dipping normal fault bordering the Yanyuan basin on the south, the erosion surface is tilted to the south against Triassic rocks. The basin is filled with coal\|bearing clastic sediments of Pliocene and early Pleistocene age, which gives the timing of the normal faulting. Based on the faulting pattern, we propose that the southeastern edge of the Tibetan plateau underwent a large amount of N\|S shortening and uplift along the Yanyuan thrust sheet in the late Tertiary, while the subsequent normal faulting that had occurred along the Yanyuan basin during the Pliocene and Pliocene can be interpreted to have accommodated gravitational collapse of the crust.
文摘We estimated crustal v p/ v s ratio of Tibetan Plateau by combined inversion of Love and Rayleigh wave dispersion data. It is developed by us that the joint inversion methods using both Love and Rayleigh wave dispersion data. Thickness and S\|wave velocity of each sub layer are taken from Love wave dispersion data, then P\|wave velocity structure was deduced using Rayleigh wave dispersion data. Densities of sub layers were estimated by the empirical relationships between seismic velocity and rock density. Having S\| and P\|wave velocities, v p/ v s ratio is calculated for each sub layer. Six sub layers in crust of Tibetan Plateau has been identified, which are 0～8km, 8～30km, 30～40km, 40～62km, 62～68km and 68～75km respectively. The S\|wave velocity structure of the Plateau is 3 13, 3 32, 3 15, 3 92, 3 45 and 3 87 km/s for each sub layer; and P\|wave velocities are 6 00, 6 10, 5 72, 6 35, 6 78 and 6 64km/s respectively v p/ v s ratios in sub layers are 1 92, 1 84, 1 82, 1 62, 1 96 and 1 72; and corresponding Poisson ratios are 0 31, 0 29, 0 28, 0 19, 0 32 and 0 24. Our result on Poisson ratios of Tibetan crust was supported by seismic waveform modelling by Rodgers and Schwartz (1998).
文摘Mt. Yulong, located in the eastern part of Tibetan Plateau, is the southmost present glaciation area both in China and Europe\|Asia continent,where distributes 19 typical sub\|tropics temperate glaciers. In the summer of 1999, a firn core, 10 10m long to the glacier ice, was successfully recovered in the accumulation area at the largest glacier (No.1 Baishui) on Mt. Yulong. Annual and seasonal variations of different climatic signals above the depth of 7 8m are apparent and five\|year snow accumulation can be clearly identified by the seasonal changes of isotopic and ionic composition, some higher values of electrical conductivity and pH values. These annual boundaries can be also verified by the positions of dirty refrozen ice layers at summer surface of each year. The mean annual net accumulation between the balance years of 94/95 and 97/98 are calculated to about 900mm water equivalent. The amplitude of isotopic changes becomes smaller with the increasing depth of the core and isotopic homogenization occurred below the depth of 7 8m. Concentrations of Ca 2+ and Mg 2+ are much higher than those of Na + and K +, reflecting that the air masses for precipitation came far from their marine sources and passed over a longer continental route. Cl - and Na + show well corresponding variation patterns in the firn profile,indicating their same genesis. Concentrations of SO 2- 4 and NO - 3 are low, reflecting very slight pollution caused by human activities in this area. According to the sum of net income recovered from the firn core and the estimated ablation amount, the average annual precipitation above the equilibrium line is estimated in the scope of 2250mm and 3200mm but it needed to be verified by long\|term observation of mass balance. As indicated by the trend of local climatic changes in last 50years, climatic signals in the firn core and recent observation at the terminal of glacier No.1 Baishui, the glaciers in Mt. Yulong start to advance in 1998 after continuous retreat from early 1980’s to late 1990’s.
文摘The A’nyemaqen ophiolite belt lies along the northeastern margin of the Tibetan Plateau and is believed to mark the boundary between the East Kunlun terrain and the ayanhar\|Songpan\|Garze terrain (Fig.1). The ophiolite in this belt is considered to be Early Permian to Middle Triassic in age (Yang et al., 1996). Our recent study indicates that there is an old ophiolite suite (>421 5Ma), located to the northern margin of this belt (Fig.1). Since the new found ophiolite is near to the Dur’ngoi deposit, so we called it North Dur’ngoi ophiolite. The geological and geochemical characteristics of the two ophiolite suites are different obviously as follows.
文摘The development of a plateau is an integral part of the evolution of recent large orogens. This is suggested by the presence of wide regions of high topographic relief in many Phanerozoic collisional belts, with the Tibetan, Anatolian, Altiplano and Colorado plateaus forming the most often cited examples. To date, plateaus have not been documented in Proterozoic orogens. However, if large Proterozoic convergent belts developed plateaus, evidence should be preserved in the geologic record.Proterozoic belts expose deeper crustal levels that are not directly accessible in modern analogues. Therefore, if they represent the final product of a plateau style evolution, their study may give direct insight on the nature of the middle to lower crust beneath modern orogenic plateaus. The Grenville Province of the Canadian Shield is a Mesoproterozoic continental collision belt of Himalayan scale that contains various lines of evidence suggesting an early plateau\|type evolution. Here we discuss this evidence and draw comparisons with the prime example of a present day plateau in a continental collision setting, the Tibetan plateau.
文摘As one of the major projects of GAME (GEWEX Asian Monsoon Experiment), the GAME\|Tibet aimed to mainly examine the energy and water cycle in Tibetan Plateau and its effects on Asian monsoon. In this paper, based on the in\|situ high\|resolution observation data of GAME\|Tibet, the soil energy\|moisture distribution and the melting\|freezing progresses and their effects on seasonal shift were preliminarily discussed.The soil energy\|water distribution and freezing\|melting processes varied at different sites in northern part of Tibetan Plateau. The temporal and spatial variation of the soil moisture content is more complex than that of temperature. The soil moisture content increased with depth in certain layers but decreased in other layers. The freezing and melting processes and the temperature distribution were largely influenced by the existence of higher soil moisture content layer. During summer monsoon, the soil moisture at 10cm at all sites is relatively high, but the spatial difference existed. Generally speaking, the shallow layers start to freeze in October and to melt from April at all sites, with about 6 months frozen period. However, the beginning time of freezing\|melting and frozen period varied at different sites.
