Constant elevation of southern Tibet over the past 15 million years

The uplift of the Tibetan plateau, an area that is 2,000 km wide, to an altitude of about 5,000 m has been shown to modify global climate and to influence monsoon intensity. Mechanical and thermal models for homogeneous thickening of the lithosphere make specific predictions about uplift rates of the Tibetan plateau, but the precise history of the uplift of the plateau has yet to be confirmed by observations. Here we present well-preserved fossil leaf assemblages from the Namling basin, southern Tibet, dated to approximately 15 Myr ago, which allow us to reconstruct the temperatures within the basin at that time. Using a numerical general circulation model to estimate moist static energy at the location of the fossil leaves, we reconstruct the elevation of the Namling basin 15 Myr ago to be 4,689 +/- 895 m or 4,638 +/- 847 m, depending on the reference data used. This is comparable to the present-day altitude of 4,600 m. We conclude that the elevation of the southern Tibetan plateau probably has remained unchanged for the past 15 Myr.     

青藏高原隆升阶段性

 青藏高原的隆升不仅是印度板块与亚洲板块碰撞导致的地球内部岩石圈地球动力学作用过程的结果,并且对全球和亚洲气候变化、亚洲地貌和地表环境过程及大量地内和地表矿产资源的形成分布产生了深刻影响。因而研究高原隆升的历史不仅对解决上述重大科学问题提供重要途径,而且可为高原区域资源环境的开发和可持续发展提供理论依据。简要回顾和梳理了国内外近年来,围绕青藏高原隆升所取得的主要进展。研究表明新生代青藏高原经历了多阶段、多幕次、准同步异幅且高原南北后期加速隆升的演化过程。具体可划分为55~30、25~10及8~0 Ma 3个主要生长隆升期次。其中55~30 Ma的高原早期隆升,主要集中在高原中南部的拉萨地块和羌塘地块,并且可能隆升到接近3 km高度,或甚至更高,有人称之为“原西藏高原”,但其周缘存在准同步异幅的变形隆升响应;25~10 Ma的中期隆升,“原西藏高原”南北缘的喜马拉雅山和可可西里-昆仑山开始强烈隆升,“原西藏高原”率先隆升到目前高度并开始向东西两侧挤出物质、拉张形成南北向裂谷,高原北缘普遍产生广泛变形隆升但幅度有限;从约8 Ma开始的晚期隆升,高原南、北部边缘的喜马拉雅山和昆仑山-西秦岭以北的高原东北部隆升显著加速,经历一系列短暂快速的多幕次构造变形和生长隆升,最终形成现今高原面貌。     

Evolution of Asian monsoons and phased uplift of the Himalaya-Tibetan plateau since Late Miocene times

The climates of Asia are affected significantly by the extent and height of the Himalayan mountains and the Tibetan plateau. Uplift of this region began about 50 Myr ago, and further significant increases in altitude of the Tibetan plateau are thought to have occurred about 10-8 Myr ago, or more recently. However, the climatic consequences of this uplift remain unclear. Here we use records of aeolian sediments from China and marine sediments from the Indian and North Pacific oceans to identify three stages of evolution of Asian climates: first, enhanced aridity in the Asian interior and onset of the Indian and east Asian monsoons, about 9-8 Myr ago; next, continued intensification of the east Asian summer and winter monsoons, together with increased dust transport to the North Pacific Ocean, about 3.6-2.6 Myr ago; and last, increased variability and possible weakening of the Indian and east Asian summer monsoons and continued strengthening of the east Asian winter monsoon since about 2.6 Myr ago. The results of a numerical climate-model experiment, using idealized stepwise increases of mountain-plateau elevation, support the argument that the stages in evolution of Asian monsoons are linked to phases of Himalaya-Tibetan plateau uplift and to Northern Hemisphere glaciation.     

青藏高原地面抬升证据讨论

当前学术界在青藏高原地面何时达到现代高度问题上存在着许多不同观点,概括起来主要有３种：１４Ｍａ前已达到高于现代的最大高度,８Ｍａ前已达到或超过现代高度,距今３．４Ｍａ来分阶中强烈上升并逐步达到现代高度,之所以出现如此大的意见分歧,除高原面积广阔,研究程度不深和覆盖面不够的原因外,不同研究者所使用研究方法和证据的差异也是重要因素,在分析了各种证据对高原地面上升的记录机理后,我们认为夷平面、河流附地,     

FY2C水汽通道资料反映的西藏高原水汽特征

本文利用2007-2009年逐时FY2C静止气象卫星水汽通道观测资料、T213垂直速度分析场分析了西藏高原水汽的空间分布,指出西藏高原有3条水汽通道,水汽来源来自孟加拉湾、南海和阿拉伯海;高原水汽日变化特点是昼弱夜强,与西藏地区降水昼晴夜雨的特征一致;地形影响水汽分布形式,进而影响降水分布特征,分析西藏高原降水分布时应该综合考虑这三者之间的联系。     

白龙江流域藏族传统岁时节日文化研究

白龙江流域藏族包括甘肃省甘南藏族自治州的迭部、舟曲两县及甘肃陇南地区的文县及宕昌等地的藏族.由于所处的自然环境、经济生活类型不同,地处青藏高原东部边缘地带的白龙江流域藏族,有自己独特的节日民俗文化.文章以岁时节日为研究主题,从节日的形成渊源、性质和类型以及对社会的影响及功能等方面进行分析,认为藏族节日文化凸显了其心理特点,构成民族精神的表象世界.这种民族精神是藏民族受到高原自然生态和文化心态的熏陶、感染,经过长期的文化积累,形成的一种强大的民族精神,它支撑着藏文化的发展与创新,具有巨大的内聚亲和精神.     

Evidence of crustal ＇channel flow＇ in the eastern margin of Tibetan Plateau from MT measurements

Magnetotelluric （MT） survey has been carried out in the eastern margin of the Tibetan Plateau and its neighboring Shimian-Leshan area, Sichuan Province. Analysis of this MT data reveals that the electric structure of the Tibetan Plateau differ much from that of the Sichuan block. In general, the electric resistivity of crust beneath the Sichuan block in the east is larger than that of the eastern margin of the Tibetan Plateau in the west. The crust of the plateau is divided into upper, middle, and lower layers. The middle crust is a low resistivity layer with minimum down to 3-10Ωm about 10-15 km thick. It presumably contains partial melt and/or salt-bearing fluids with low viscosity, prone to deform and flow, producing a ＂channel flow＂ under the southeastward squeeze of the eastern Tibetan Plateau. This low-resistivity layer makes the upper crust decoupled mechanically from the lower crust. In the brittle upper crust, faults are dominated by left-lateral strike-slip and thrust motions, leading to surface rising and shallow earthquakes. The low-resistivity layer also cut the Xianshuihe-Anninghe fault zone into two sections vertically. In this region, the thicknesses of upper, middle, and lower crust vary laterally, producing a transitional zone in the eastern margin of the Tibetan Plateau characterized by thicker crust and higher elevation in the west and thinner crust and lower elevation in the east.     

初进高原的汉族与世居藏族血液学指标的比较研究

目的：通过比较初进高原（1周之内）的汉族与高原世居藏族的血常规18项指标及血压、心率、血氧饱和度,研究低氧对机体代谢功能的影响,尤其是低氧对机体血液学指标的影响。方法：采用指尖采血的方法,利用Sysmax的Poch100i型血液自动分析仪（日本产）进行血常规18项指标的检测;使用水银血压测量仪进行静息状态下右上肢肱动脉血压的测定;测定静息状态下的心率;使用NP-40型血氧饱和度测定仪（日本）检测血氧饱和度。采集的数据利用SPSS统计软件进行分析。结果：①进藏1周之内的汉族,其血红蛋白、红细胞压积、平均血红蛋白量、平均血红蛋白浓度、血小板、白细胞计数均小于世居高原的藏族（P〈0.05）,而红细胞计数、平均红细胞体积与世居高原的藏族无差别（P〉0.05）;②进藏1周之内的汉族的收缩压、舒张压、心率均高于世居高原的藏族（P〈0.05）,而血氧饱和度却低于世居高原的藏族（P〈0.05）;结论：进藏1周之内的汉族在红细胞系统指标（HGB、HCT、MCH、MCHC）及血压、心率、血氧饱和度等指标与世居高原的藏族青年存在明显差异。应进一步扩大样本量,以阐明汉族在高原习服过程中上述指标的变化程度和变化规律,为更好地了解高原习服的机制提供理论依据。     

New geological evidence of crustal thickening in the Gangdese block prior to the Indo-Asian collision

Recent mapping in the Gangdese block has revealed many leucogranites that are similar to those in the High Himalaya. These leucogranites formed at ～140 Ma as indicated by monazite Th-Pb ion-microprobe dating and cooled at ～130 Ma as indicated by muscovite ^40Ar/^39Ar dating. In conjunction with previous structural and paleogeographic studies, the new data indicate that the Gangdese block underwent crustal thickening and associated exhumation during ～140—130 Ma. In this regard, the southern margin of Eurasia continent was comparable to the modern South American Altiplano-Puna plateau, the prime example of active ocean-continent subduction and associated thickened crust. Specifically, the early stages of crustal thickening and uplifting of the Gangdese block may result from subduction of the Neo-Tethyan Ocean. If the Tibetan Plateau would form by accretion of a series of blocks with thickened crust, an elevated topographic plateau similar to the Altiplano-Puna plateau had formed before collision between the Indian and Eurasian plates. Then the Tibetan Plateau would have quickly thickened, uplifted, and begun to extend soon after onset of the collision. Thus, the deformational mechanism of the Tibetan Plateau is not distributed shortening, but rather concentrating deformation within regions of thin crust between the accreted blocks.     

青藏高原地区生态保护立法模式的确立——以藏族生态文化为视角

在青藏高原生态保护立法中如何有效利用藏族生态文化,关系到该地区生态保护的成败。因此．在青藏高原地区生态环境保护立法中既要强调国家的作用,也要对该地区民族生态文化传统给予足够的重视。为此,在该地区生态环保立法中首先应当确立服务型立法与促进型立法相结合的模式,对藏族生态文化进行有效引领;其次,从另外一个层面来看,还应当确立地方立法与中央立法相结合的立法模式,对藏族生态文化从立法上予以充分吸收,并为其对青藏高原地区生态保护发挥积极作用从制度上提供物质保障。     

Tibetan plateau river incision inhibited by glacial stabilization of the Tsangpo gorge

A considerable amount of research has focused on how and when the Tibetan plateau formed in the wake of tectonic convergence between India and Asia. Although far less enquiry has addressed the controls on river incision into the plateau itself, widely accepted theory predicts that steep fluvial knick points (river reaches with very steep gradients) in the eastern Himalayan syntaxis at the southeastern plateau margin should erode rapidly, driving a wave of incision back into the plateau. Preservation of the plateau edge thus presents something of a conundrum that may be resolved by invoking either differential rock uplift matching erosional decay, or other mechanisms for retarding bedrock river incision in this region where high stream power excludes the potential for aridity as a simple limit to dissection of the plateau. Here we report morphologic evidence showing that Quaternary depression of the regional equilibrium line altitude, where long-term glacier mass gain equals mass loss, was sufficient to repeatedly form moraine dams on major rivers: such damming substantially impeded river incision into the southeastern edge of the Tibetan plateau through the coupled effects of upstream impoundment and interglacial aggradation. Such glacial stabilization of the resulting highly focused river incision centred on the Tsangpo gorge could further contribute to initiating and accentuating a locus of rapid exhumation, known as tectonic anaeurysm.     

Geodetic evidence for a low slip rate in the Altyn Tagh fault system

The collision between India and Asia has been simulated with a variety of computational models that describe or predict the motions of the main faults of east Asia. Geological slip-rate estimates of 20-30 mm yr(-1) suggest that the largest of these faults, the 2,000-km-long Altyn Tagh fault system on the northern edge of the Tibetan plateau, absorbs as much of the Indo-Asian convergence signal as do the Himalayas--partly by oblique slip and partly by contraction and mountain growth. However, the predictions of dynamic models for Asian deformation and the lower bounds of some geological slip-rates estimates (3-9 mm yr(-1); refs 7, 8) suggest that the Altyn Tagh system is less active. Here, we report geodetic data from 89-91 degrees E that indicate left-lateral shear of 9 +/- 5 mm yr(-1) and contraction of 3 +/- 1 mm yr(-1) across the Altyn Tagh system. This result--combined with our finding that, at 90 degrees E, Tibet contracts north-south at 9 +/- 1 mm yr(-1)--supports the predictions of dynamic models of Asian deformation.     

藏雪鸡（Tetraogallus tibetanus）冬季活动规律及觅食地的选择

2009年12月～2010年3月间在西藏日喀则南木林县南木林镇岗噶村周围对藏雪鸡的冬季活动规律与觅食地选择进行了初步研究。结果显示,藏雪鸡在该地区冬季主要活动在平均海拔4484.16±242.99m（n=73）,上线海拔达到5233m,下线海拔4213m。日活动强度显示有3个峰点,分别是9：00、12：00、19：00。主要以6～10只为集群的形式觅食。通过对73个样方14个参数进行主成分分析后发现,海拔高度是冬季藏雪鸡活动规律及觅食地选择的最主要因子,植被是次主要因子,坡向是次要因子。     

Earth science: palaeo-altimetry of Tibet

The determination of palaeo-elevation has emerged in the past 15 years as an important tool for constraining physical processes that govern the formation of mountain belts. Rowley and Currie report palaeo-elevations for the Lunpola basin within the Tibetan plateau and claim that these elevations are incompatible with 'mantle-thickening models' for mountain formation. We show here that their data do not support this conclusion and, indeed, are consistent with its opposite. The Tibetan plateau could have risen by a kilometre or more as its dense lower lithosphere sank into the underlying mantle.     

Normal faulting in central Tibet since at least 13.5 Myr ago

Tectonic models for the evolution of the Tibetan plateau interpret observed east-west thinning of the upper crust to be the result of either increased potential energy of elevated crust or geodynamic processes that may be unrelated to plateau formation. A key piece of information needed to evaluate these models is the timing of deformation within the plateau. The onset of normal faulting has been estimated to have commenced in southern Tibet between about 14 Myr ago and about 8 Myr ago and, in central Tibet, about 4 Myr ago. Here, however, we report a minimum age of approximately 13.5 Myr for the onset of graben formation in central Tibet, based on mineralization ages determined with Rb-Sr and 40Ar-39Ar data that post-date a major graben-bounding normal fault. These data, along with evidence for prolonged activity of normal faulting in this and other Tibetan grabens, support models that relate normal faulting to processes occurring beneath the plateau. Thinning of the upper crust is most plausibly the result of potential-energy increases resulting from spatially and temporally heterogeneous changes in thermal structure and density distribution within the crust and upper mantle beneath Tibet. This is supported by recent geophysical and geological data, which indicate that spatial heterogeneity exists in both the Tibetan crust and lithospheric mantle.     

Discovery of the granulite xenoliths in Cenozoic volcanic rocks from Hoh Xil,Tibetan plateau

Two-pyroxene granulite and clinopyroxene granulite xenoliths have been recently discovered in the Late Paleogene toNeogene volcanic rocks (with ages in the range of 4.27～44.60 Ma) that outcropped in Hoh Xil, central Tibetan plateau. Based on theelectron microprobe analysis data, the xenoliths provide constraints for the formation equilibrium temperatures of the two-pyroxene gran-ulite being about 783 to 818℃ as determined by two-pyroxene thermometry and the forming pressure of the clinopyroxene granulite beingabout 0.845 to 0.858 GPa that is equivalent to 27.9～28.3 km depth respectively. It indicates that these granulite xenoliths represent thesamples from the middle part of the thickened Tibetan crust. This discovery is important and significant to making further discussion onthe component and thermal regime of the deep crust of the Tibetan plateau.     

青藏高原城镇化时空格局变化及自然驱动因素分析

青藏高原特殊的自然条件导致了其较低的城镇化发展水平,分析青藏高原城镇化发展的时空格局与成因对推动当地未来的新型城镇化具有重要的指导意义。本文利用1990-2020年历次人口普查数据,对青藏高原范围内县域单元的城镇化水平时空变化进行分析,并利用地理探测器分析导致城镇化格局形成的自然地理因素。结果表明：青藏高原地区整体城镇化水平较低,城镇化率波动较大,区域差异明显,且差异有减小的趋势;城镇化水平较高的地区集中在行政中心与高原东部边缘地区,高原中部部分地区存在城镇化率下降的情况;地形因素是影响青藏高原地区城镇化发展的主要自然因素。     

Comprehensive geophysical profile and lithosphere structures and geodynamics in western Qinghai-Xizang (Tibetan) Plateau

A comprehensive study in this paper for the lithosphere velocity structure, conductivity structure, density and magnetism structure at the Qinghai-Xizang(Tibetan) Plateau has been completed based on the data of gravity, geomagnetism, and magneto-telluric sounding (MTS), explosion seismology acquired on the comprehensive geophysical profile along Gyirong-Sangehu. It presents the deep and shallow structural features of blocks, suture zones, and faults. Meanwhile, the lithosphere structure at the east and west parts of the plateau has been crossstudied and the deep structure of the plateau and the geodynamic models have been discussed according to the geophysical data available for the Qinghai-Xizang (Tibetan) Plateau.     

Numerical simulation of GPS observed clockwise rotation around the eastern Himalayan syntax in the Tibetan Plateau

From Global Position System (GPS) measurements, there is a clockwise rotation around the eastern Himalayan syntax in the Tibetan Plateau. This phenomenon is difficult to be interpreted by simple two-dimensional modeling from a geodynamic point of view. Because of the extremely thick crust and the lower crust with relatively high temperature in the Tibetan Plateau, the lithospheric rheology in Tibet and surrounding areas present a complex structure. In general, the tectonic structure of the Tibetan Plateau consists of brittle upper crust, ductile lower crust, high viscosity lithospheric upper mantle, and low viscosity asthenosphere, the same as the case in many other continental regions. However, the lower crust in the Tibetan Plateau is much more ductile with a lower viscosity than those of its surroundings at the same depth, and the effective viscosity is low along the collision fault zone. In this study, we construct a three-dimensional Maxwell visco-elastic model in spherical coordinate system, and simulate the deformation process of the Tibetan Plateau driven by a continuous push from the Indian plate. The results show that the existence of the soft lower crust under the plateau makes the entire plateau uplift as a whole, and the Himalayas and the eastern Himalayan syntax uplift faster. Since the lower crust of surrounding blocks is harder except in the southeastern corner where the high-temperature material is much softer and forms an exit channel for material transfer, after the whole plateau reaches a certain height, the lower crustal and upper mantle material begins to move eastward or southeastward and drag the upper crust to behave same way. Thus, from the macroscopic point of view, a relative rigid motion of the plateau with a clockwise rotation around the eastern Himalayan syntax is developed. Supported by Knowledge Innovation Project of the Chinese Academy of Sciences (Grant No. KZCX2-YW-123) and National Natural Science Foundation of China (Grant Nos. 40774048 and 90814014)     

低氧对不同海拔雄性高原鼠兔生殖机能若干指标的影响

为了探讨低氧对不同海拔雄性高原鼠兔(Ochotona curzoniae)生殖机能的影响,测定了不同海拔雄性高原鼠兔繁殖期睾丸指数,附睾指数,附睾尾精子数量,精子活率和睾丸组织LDH-C4和LDH比活力及其比值;同时还统计了不同海拔雌性高原鼠兔胎仔数。结果显示:不同海拔高原鼠兔睾丸指数、睾丸组织LDH-C4比活力和LDH比活力均无显著差异(P﹥0.05);而高海拔高原鼠兔附睾指数和附睾尾精子数量均极显著高于低海拔高原鼠兔(P﹤0.01);高海拔高原鼠兔精子活率和LDH-C4比活力/LDH比活力均显著高于低海拔高原鼠兔(P﹤0.05);而高海拔雌性高原鼠兔胎仔数却显著低于低海拔高原鼠兔(P﹤0.05)。以上结果表明,随着海拔的升高,低氧对高原鼠兔精子生成和精子活率不仅没有抑制,反而明显提高,但低氧对雌性高原鼠兔胎仔有显著影响,随着低氧程度提高,胎仔数下降。