Multiple Uplift and Exhumation of the Southeastern Tibetan Plateau:Evidence from Low-Temperature Thermochronology

Since the Cenozoic,the Tibetan Plateau has experienced large-scale uplift and outgrowth due to the India-Asia collision.However,the mechanism and timing of these tectonic processes still remain debated.Here,using apatite fission track dating and inverse thermal modeling,we explore the mechanism of different phases of rapid cooling for different batholiths and intrusions in the southeastern Tibetan Plateau.In contrast to previous views,we find that the coeval granitic batholith exposed in the same tectonic zone experienced differential fast uplift in different sites,indicating that the present Tibetan Plateau was the result of differential uplift rather than the entire lithosphere uplift related to lithospheric collapse during Cenozoic times.In addition,we also suggest that the 5-2 Ma mantle-related magmatism should be regarded as the critical trigger for the widely coeval cooling event in the southeastern Tibetan Plateau,because it led to the increase in atmospheric CO_(2)level and a hotter upper crust than before,which are efficient for suddenly fast rock weathering and erosion.Finally,we propose that the current landform of the southeastern Tibetan Plateau was the combined influences of tectonic and climate.

Atmospheric Sulfur and Nitrogen Deposition in Five Nature Reserves of Sichuan Basin to Qinghai-Tibetan Plateau Transect Region,Southwest-ern China

Enhanced sulfur and nitrogen deposition has been observed in many transect regions worldwide,from urban/agricultural areas to mountains.The Sichuan Basin(SCB),with 18 prefectural cities,is the most economically-developed region in western China,while the rural Qinghai-Tibetan Plateau(QTP)lies west of the SCB.Previous regional and national atmospheric modeling studies have sug-gested that large areas in the SCB-to-QTP transect region experience excessive deposition of sulfur and nitrogen.In this study,we ap-plied a passive monitoring method at 1l sites(one in urban Chengdu and 10 from fivenature reserves)in this transect region from September 2021 to October 2022 to confirm the high sulfur and nitrogen deposition fluxes and to understand the gaps between the mod-eling and observation results for this transect region.These observations suggest that the five reserves are under eutrophication risk,and only two reserves are partially under acidification risk.Owing to the complex topography and landscapes,both sulfur and nitrogen de-position and critical loads exhibit large spatial variations within a reserve,such as Mount Emei.Regional atmospheric modeling may not accurately capture the spatial variations in deposition fluxes within a reserve;however,it can capture general spatial patterns over the entire transect.This study demonstrates that a combination of state-of-the-art atmospheric chemical models and low-cost monitoring methods is helpful for ecological risk assessments at a regional scale.

Ground-Based Atmospheric CO_(2),CH_(4),and CO Column Measurements at Golmud in the Qinghai-Tibetan Plateau and Comparisons with TROPOMI/S5P Satellite Observations

Measurements of carbon dioxide(CO_(2)),methane(CH_(4)),and carbon monoxide(CO)are of great importance in the Qinghai-Tibetan region,as it is the highest and largest plateau in the world affecting global weather and climate systems.In this study,for the first time,we present CO_(2),CH_(4),and CO column measurements carried out by a Bruker EM27/SUN Fourier-transform infrared spectrometer(FTIR)at Golmud(36.42°E,94.91°N,2808 m)in August 2021.The mean and standard deviation of the column-average dry-air mixing ratio of CO_(2),CH_(4),and CO(XCO_(2),XCH_(4),and XCO)are 409.3±0.4 ppm,1905.5±19.4 ppb,and 103.1±7.7 ppb,respectively.The differences between the FTIR co-located TROPOMI/S5P satellite measurements at Golmud are 0.68±0.64%(13.1±12.2 ppb)for XCH_(4) and 9.81±3.48%(–10.7±3.8 ppb)for XCO,which are within their retrieval uncertainties.High correlations for both XCH_(4) and XCO are observed between the FTIR and S5P satellite measurements.Using the FLEXPART model and satellite measurements,we find that enhanced CH_(4) and CO columns in Golmud are affected by anthropogenic emissions transported from North India.This study provides an insight into the variations of the CO_(2),CH_(4),and CO columns in the Qinghai-Tibetan Plateau.

Spatiotemporal variation of ecological environment quality and extreme climate drivers on the Qinghai-Tibetan Plateau

Protecting the ecological security of the Qinghai-Tibet Plateau(QTP)is of great importance for global ecology and climate.Over the past few decades,climate extremes have posed a significant challenge to the ecological environment of the QTP.However,there are few studies that explored the effects of climate extremes on ecological environment quality of the QTP,and few researchers have made quantitative analysis.Hereby,this paper proposed the Ecological Environmental Quality Index(EEQI)for analyzing the spatial and temporal variation of ecological environment quality on the QTP from 2000 to 2020,and explored the effects of climate extremes on EEQI based on Geographically and Temporally Weighted Regression(GTWR)model.The results showed that the ecological environment quality in QTP was poor in the west,but good in the east.Between 2000 and 2020,the area of EEQI variation was large(34.61%of the total area),but the intensity of EEQI variation was relatively low and occurred mainly by a slightly increasing level(EEQI change range of 0.05-0.1).The overall ecological environment quality of the QTP exhibited spatial and temporal fluctuations,which may be attributed to climate extremes.Significant spatial heterogeneity was observed in the effects of the climate extremes on ecological environment quality.Specifically,the effects of daily temperature range(DTR),number of frost days(FD0),maximum 5-day precipitation(RX5day),and moderate precipitation days(R10)on ecological environment quality were positive in most regions.Furthermore,there were significant temporal differences in the effects of consecutive dry days(CDD),consecutive wet days(CWD),R10,and FD0 on ecological environment quality.These differences may be attributed to variances in ecological environment quality,climate extremes,and vegetation types across different regions.In conclusion,the impact of climate extremes on ecological environment quality exhibits complex patterns.These findings will assist managers in identifying changes in the ecological environment quality of the QTP and addressing the effects of climate extremes.

The particular species determining spatial heterogeneity in shady and terrace on the Qinghai-Tibetan Plateau,China

Spatial patterns of plant species and patchy community are important properties in grasslands.However,research regarding spatial patterns of formed patches with various species has not fully advanced until now.Our purpose is to clarify differences in spatial pattern formed by species and community constructed under shady and terrace habitats.The three common Kobresia-Carex patches(Size 1,0.6–0.9 m^(2);Size 2,3.0–3.8 m^(2) and Size 3,6.5–8.8 m^(2))were selected in shady and terrace on the Qinghai-Tibetan Plateau,and corresponding quadrats of 1m1m,2m2m and 3m3m were placed for S1,S2 and S3 patches,respectively.The surveyed quadrats were divided into 20cm20cm large cells(L-cells),and further divided into four 10cm10cm small cells(S-cells).We used the binary occurrence system(presence/absence data)to record occurrences of all species in S-cells.The analysis shows that the power law model was well able to determine the spatial distribution pattern of species or patchy community in shady and terrace.All species and patches show aggregated distribution in shady and terrace habitats.In the shady habitat,the relative spatial heterogeneity(ε)of individual plant species was lowest at presence frequency(P)of 0.1–0.3,whereas in the terrace habitatεwas lowest at P<0.1,andεincreased monotonically with increasing P.For most dominant species,P andεvalues were higher in terrace than those in shady.We concluded that the dominant species largely determine spatial heterogeneity of the Kobresia-Carex patches,while companion and rare species have weak influence on the community-level heterogeneity in shady and terrace habitats.

An Orthogonal Collision Dynamic Mechanism of Wave-Like Uplift Plateaus in Southern Asia

In southern Asia, there are three large-scale wave-like mountains ranging from the Tibetan Plateau westward to the Iranian Plateau and the Armenian Plateau. On the southern side between plateaus, there are the Indian Peninsula and the Arabian Peninsula. What dynamic mechanisms form the directional alignment of the three plateaus with the two peninsulas remains a mystery. In the early stages of the Earth’s geological evolution, the internal structure of the Earth was that the center was a solid core, and the outmost layer was a thin equatorial crust zone separated by two thick pristine continents in polar areas, while the middle part was a deep magma fluid layer. Within the magma fluid layer, thermal and dynamic differences triggered planetary-scale vertical magma cells and led to the core-magma angular momentum exchange. When the core loses angular momentum and the magma layer gains angular momentum, the movement of upper magma fluids to the east and the tropical convergence zone (TCZ) drives the split and drift of two thick pristine continents, eventually forming the current combination of these plateaus and peninsulas and their wave-like arrangement along the east-west direction. Among them, the horizontal orthogonal convergence (collision) of upper magma fluids from the two hemispheres excited the vertical shear stress along the magma TCZ, which is the dynamic mechanism of mountain uplifts on the north side and plate subductions on the south side. To confirm this mechanism, two examples of low-level winds are used to calculate the correspondence between cyclone/anticyclonic systems generated by the orthogonal collision of airflows along the atmospheric TCZ and satellite-observed cloud systems. Such comparison can help us revisit the geological history of continental drift and orogeny.

Geochemical characteristics of Sr isotopes in the LS33 drill core from the Qiongdongnan Basin, South China Sea, and their response to the uplift of the Tibetan Plateau

Making full use of modern analytical and testing techniques to explore and establish new indexes or methods for extracting paleoseawater geochemical information from sediments will help to reconstruct the sedimentary paleoenvironment in different research areas.The connection between the subsidence of the South China Sea basin and the uplift of the Tibetan Plateau has been a scientific concern in recent decades.To explore the information on the sedimentary paleoenvironment,provenance changes and uplift of Tibetan Plateau contained in core sediments(debris),we selected core samples from Well LS33 in the Qiongdongnan Basin,South China Sea,and analyzed the contents of typical elements(Al,Th,and rare earth elements)that can indicate changes in provenance and the Sr isotopic compositions,which can reveal the geochemical characteristics of the paleoseawater depending on the type of material(authigenic carbonate and terrigenous detritus).The results show the following:(1)during the late Miocene,the Red River transported a large amount of detrital sediments from the ancient continental block(South China)to the Qiongdongnan Basin.(2)The authigenic carbonates accurately record changes in the 87Sr/86Sr ratios in the South China Sea since the Oligocene.These ratios reflect the semi-closed marginal sea environment of the South China Sea(relative to the ocean)and the sedimentary paleoenvironment evolution process of the deep-water area of the Qiongdongnan Basin from continental to transitional and then to bathyal.(3)Since the Neogene,the variations in the 87Sr/86Sr ratio in the authigenic carbonates have been consistent with the variations in the uplift rate of the Tibetan Plateau and the sediment accumulation rate in the Qiongdongnan Basin.These consistent changes indicate the complex geological process of the change in the rock weathering intensity and terrigenous Sr flux caused by changes in the uplift rate of the Tibetan Plateau,which influence the Sr isotope composition of seawater.

The Relationship of Black-necked Crane Migration to the Uplift of the Qinghai-tibetan Plateau

Bird migration is a seasonal movement between breeding and wintering grounds.Opinions are widely divided on the reasons for this movement.According to biological data including:geographic distribution,reproductive physiology,comparison of breeding and wintering habitats,geological data including Qinghai Tibetan Plateau uplift and Quatemary Period glaciation,it is inferred that bird migration is a survival mechanism,and that migration originated on the breeding grounds.

Sensitivity of East Asian Climate to the Progressive Uplift and Expansion of the Tibetan Plateau Under the Mid-Pliocene Boundary Conditions

A global atmospheric general circulation model has been used to perform eleven idealized numerical experiments, i.e., TP10, TP10, .., TP100, corresponding to different percentages of the Tibetan Plateau altitude. The aim is to explore the sensitivity of East Asian climate to the uplift and expansion of the Tibetan Plateau under the reconstructed boundary conditions for the mid-Pliocene about 3 Ma ago. When the plateau is progressively uplifted, global annual surface temperature is gradually declined and statistically significant cooling signals emerge only in the Northern Hemisphere, especially over and around the Tibetan Plateau, with larger magnitudes over land than over the oceans. On the contrary, annual surface temperature rises notably over Central Asia and most parts of Africa, as well as over northeasternmost Eurasia in the experiments TP60 to TP100. Meanwhile, the plateau uplift also leads to annual precipitation augmentation over the Tibetan Plateau but a reduction in northern Asia, the Indian Peninsula, much of Central Asia, parts of western Asia and the southern portions of northeastern Europe. Additionally, it is found that an East Asian summer monsoon system similar to that of the present initially exists in the TP60 and is gradually intensified with the continued plateau uplift. At 850 hPa the plateau uplift induces an anomalous cyclonic circulation around the Tibetan Plateau in summertime and two anomalous westerly currents respectively located to the south and north of the Tibetan Plateau in wintertime. In the mid-troposphere, similarto-modern spatial pattern of summertime western North Pacific subtropical high is only exhibited in the experiments TP60 to TP100, and the East Asian trough is steadily deepened in response to the progressive uplift and expansion of the Tibetan Plateau.

Cenozoic uplift of the Tibetan Plateau:Evidence from the tectonic-sedimentary evolution of the western Qaidam Basin

Geologists agree that the collision of the Indian and Asian plates caused uplift of the Tibet Plateau. However, controversy still exists regarding the modes and mechanisms of the Tibetan Plateau uplift. Geology has recorded this uplift well in the Qaidam Basin. This paper analyzes the tectonic and sedimentary evolution of the western Qaidam Basin using sub-surface seismic and drill data. The Cenozoic intensity and history of deformation in the Qaidam Basin have been reconstructed based on the tectonic developments, faults growth index, sedimentary facies variations, and the migration of the depositional depressions. The changes in the sedimentary facies show that lakes in the western Qaidam Basin had gone from inflow to still water deposition to withdrawal. Tectonic movements controlled deposition in various depressions, and the depressions gradually shifted southeastward. In addition, the morphology of the surface structures in the western Qaidam Basin shows that the Cenozoic tectonic movements controlled the evolution of the Basin and divided it into （a） the southern fault terrace zone, （b） a central Yingxiongling orogenic belt, and （c） the northern fold-thrust belt; divided by the XI fault （Youshi fault） and Youbei fault, respectively. The field data indicate that the western Qaidam Basin formed in a Cenozoic compressive tectonic environment caused by the India--Asia plate collision. Further, the Basin experienced two phases of intensive tectonic deformation. The first phase occurred during the Middle Eocene--Early Miocene （Xia Ganchaigou Fm. and Shang Ganchaigou Fro., 43.8- 22 Ma）, and peaked in the Early Oligocene （Upper Xia Ganchaigou Fro., 31.5 Ma）. The second phase occurred between the Middle Miocene and the Present （Shang Youshashan Fro. and Qigequan Fro., 14.9-0 Ma）, and was stronger than the first phase. The tectonic--sedimentary evolution and the orienta- tion of surface structures in the western Qaidam Basin resulted from the Tibetan Plateau uplift, and recorded the periodic northward growth of the Plateau. Recognizing this early tectonic--sedimentary evolution supports the previous conclusion that northern Tibet responded to the collision between India and Asia shortly after its initiation. However, the current results reveal that northern Tibet also experi- enced another phase of uplift during the late Neogene. The effects of these two stages of tectonic activity combined to produce the current Tibetan Plateau.

Cenozoic Evolution of Sediments and Climate Change and Response to Tectonic Uplift of the Northeastern Tibetan Plateau

Through a comprehensive study of magnetostratigraphy and sedimentology of several basins in the northeastern Tibetan Plateau,we reveal that the study area mainly experienced six tectonic uplift stages at approximately 52 Ma,34-30 Ma,24-20 Ma,16-12 Ma,8-6 Ma,and 3.6-2.6 Ma.Comprehensive analyses of pollen assemblages from the Qaidam,Linxia,Xining,and West Jiuquan Basins show that the northeastern Tibetan Plateau has undergone six major changes in vegetation types and climate：50-40 Ma for the warm-humid forest vegetation,40-23 Ma for the warm-arid and temperate-arid forest steppe vegetation,23-18.6 Ma for the warm-humid and temperate-humid forest vegetation,18.6-8.5 Ma for the warm-humid and cool-humid forest steppe vegetation,8.6-5 Ma for the temperate sub-humid savanna steppe vegetation,and 5-1.8 Ma for the cold-arid steppe vegetation.Comprehensive comparisons of tectonic uplift events inferred from sedimentary records,climatic changes inferred from pollen,and global climate changes show that in the northeastern Tibetan Plateau the climate in the Paleogene at low altitude was mainly controlled by the global climate change,while that in the Neogene interval with high altitude landscapes of mountains and basins is more controlled by altitude and morphology.

Sedimentary Evolution of the Qinghai-Tibet Plateau in Cenozoic and its Response to the Uplift of the Plateau

We have studied the evolution of the tectonic lithofacies paleogeography of Paleocene- Eocene, Oligocene, Miocene, and Pliocene of the Qinghai-Tibet Plateau by compiling data regarding the type, tectonic setting, and iithostratigraphic sequence of 98 remnant basins in the plateau area. Our results can be summarized as follows. （1） The Paleocene to Eocene is characterized by uplift and erosion in the Songpan-Garze and Gangdise belts, depression （lakes and pluvial plains） in eastern Tarim, Qaidam, Qiangtang, and Hoh Xil, and the Neo-Tethys Sea in the western and southern Qinghai-Tibet Plateau. （2） The Oligocene is characterized by uplift in the Gangdise--Himalaya and Karakorum regions （marked by the absence of sedimentation）, fluvial transport （originating eastward and flowing westward） in the Brahmaputra region （marked by the deposition of Dazhuka conglomerate）, uplift and erosion in western Kunlun and Songpan-Garze, and depression （lakes） in the Tarim, Qaidam, Qiangtang, and Hoh Xil. The Oligocene is further characterized by depressional littoral and neritic basins in southwestern Tarim, with marine facies deposition ceasing at the end of the Oligocene. （3） For the Miocene, a widespread regional unconformity （ca. 23 Ma） in and adjacent to the plateau indicates comprehensive uplift of the plateau. This period is characterized by depressions （lakes） in the Tarim, Qaidam, Xining-Nanzhou, Qiangtang, and Hoh Xil. Lacustrine facies deposition expanded to peak in and adjacent to the plateau ca. 18-13 Ma, and north-south fault basins formed in southern Tibet ca. 13-10 Ma. All of these features indicate that the plateau uplifted to its peak and began to collapse. （4） Uplift and erosion occurred during the Pliocene in most parts of the plateau, except in the Hoh Xil-Qiangtang, Tarim, and Qaidam. The continuous uplift and intensive taphrogeny in the plateau divided the original large basin into small basins, deposition of lacustrine facies decreased considerably, and boulderstone accumulated, indicating a response to the overall uplift of the plateau. Here, we discuss the evolution of tectonic lithofacies paleogeography in Cenozoic and its response to the tectonic uplift of the Qinghai-Tibet Plateau in relation to the above characteristics. We have recognized five major uplift events, which occurred during 58-53 Ma, 45-30 Ma, 25-20 Ma, 13-7 Ma, and since 5 Ma. The results presented here indicate that the paleogeomorphic configurations of the Qinghai-Tibet Plateau turned over during the late Miocene, with high elevations in the east during the pre-Miocene switching to high contours in the west at the end of Miocene.

Chronological Link Between the Abrupt Change of the Loess Grain Size Sequence and the Formation of River Terraces on the Eastern Margin of the Qinghai-Tibetan Plateau Since the Late Early-Pleistocene

Based on the study of magnetostratigraphy,magnetic susceptibility and grain size of Garze A section on the southeastern margin of the Qinghai-Tibetan Plateau since the late early-Pleistocene,the basal age of Garze loess is located at～1.16 MaBP and a series of abrupt paleoclimatic changes is detected.The times of abrupt changes are of distinct series features,and the interval between each two adjacent abrupt changes is～50 kyr or～100 kyr.The most significant abrupt changes occur at around 1.06,0.85,0.6,0.46,0.39 and 0.14 MaBP.There is a chronological link between the abrupt changes of paleoclimate and the formation of river terraces and it is almost simultaneous with a strengthening trend of neotectonic activities.Therefore,maybe the climatic transition controll the timing of terrace formation,and the tectonic uplift originate potential energy and has a direct effect on channel incision, both the climatic transition and the tectonic uplift are important.Terraces are the products of the interaction of instable climatic variations and tectonic uplift.Like the loess-paleosol sequences,river terrace sequences are also controlled by the climate-tectonic coupling system and are ruled by climate-tectonic gyration with a～100 kyr paracycle,which may be the short eccentricity period of the earth.

Analysis of Dynamics and Driving Factors of Wetland Landscape in Zoige,Eastern Qinghai-Tibetan Plateau

Zoige Wetland is one of the largest plateau wetlands in the world. This paper provides a dynamic analysis of spatial and temporal patterns of the wetland in Zoige, Eastern Qinghai-Tibetan Plateau, supported by ERDAS8.7 and ArcGIS9.0. It is the first comparative analysis of a system of rapidly changing wetland with landscape patterns in Zoige, using 3 classified landsat Thematic Mapper images of 1977, 1994 and 2001. The classified images were used to generate wetland distributing maps, and shape index （S）, diversity index （H）, dominance index （D）, evenness index （E）, fragmentation index （F） and fractal dimension （Fd） were calculated and analyzed spatiotemporally across pure grazing area in Zoige for each landscape type and in different periods （before 1977, during 1977-1994 and 1994-2001）, as well as the driving forces of natural and anthropogenic. The study shows that for a comprehensive understanding of the shapes and trajectories of the shrinking and desertificated land expansion of the wetland, a spatiotemporal landscape metrics analysis in different periods is an improvement than only with landscape changing rates. This type of analysis can also be used to infer underlying social, economic, and political processes that drive the observed wetland forms. The results indicate that wetland patterns can be changed over relatively short periods of time. The total area of lake reduced by 164.86 km^2, grassland extended by 141.74 km^2, semi-marsh extended by 105.94 km^2, marsh reduced by 86.00 km^2 the number of landscape patches reduced by 56, and their average area decreased by 2.68 km^2, the successions within lake, marsh, semi-marsh and grassland were found obviously. S decreased stepwise： D and F increased but H decreased： The changing rate after 1994 was 2.3 to 2.9 times greater than that before. The change of the wetland landscape patterns resulted in the interaction between socio-ceenomic and natural forces of positive and negative aspects; and natural factors affected as assistant aspect. Some important human activities in this period led to the change of the landscape patterns in this region directly. Some measurements made by government and NGO delayed the converting process partly.

Evapotranspiration and Its Energy Exchange in Alpine Meadow Ecosystem on the Qinghai-Tibetan Plateau

To understand the water and energy exchange on the Qinghai-Tibetan Plateau, we explored the characteristics of evapotranspiration （ET） and energy fluxes from 2002 to 2005 over a Kobresia meadow ecosystem using the eddy covariance method. The ratio of annual ET to precipitation （P） of meadow ecosystem was about 60%, but varied greatly with the change of season from summer to winter. The annual ET/P in meadow was lower than that in shrub, steppe and wetland ecosystems of this plateau. The incident solar radiation （Rs） received by the meadow was obviously higher than that of lowland in the same latitude; however the ratio of net radiation （Rn） to Rs with average annual value of 0.44 was significantly lower than that in the same latitude. The average annual ET was about 390 mm for 2002-2005, of which more than 80% occurred in growing season from May to September. The energy consumed on the ET was about 44% of net radiation in growing season, which was lower than that of shrub, steppe and wetland on this plateau. This study demonstrates that the Kobresia meadow may prevent the excessive water loss through evapotranspiration from the ecosystem into the atmosphere in comparison to the shrub, steppe and wetland ecosystems of the Qinghai-Tibetan Plateau.

PRESENT LANDFORMS, ACTIVE TECTONIC ZONES, DEEP STRUCTURES AND UPLIFT MECHANISMS OF THE LONGSHOUSHAN BLOCK ON THE NORTHERN MARGIN OF THE QINGHAI—TIBET PLATEAU

Located in the northern margin of the Qinghai—Tibet Plateau, the Longshoushan Mt. is a small block between Qinghai—Tibet Landmass and Alashan Landmass.Traditional tectonic viewpoint does not consider that the Longshoushan Mt. is a single tectonic block. It is quite evident that there is only a hazy idea about the Longshoushan block. Though there is a very complex tectonic region between Qinghai—Tibet Landmass and Alashan Landmass, the Longshoushan block in the region shows unique tectonic landforms, deep structures and uplift mechanisms. Researching into the relationship between the Longshoushan block and the Qinghai—Tibet and Alashan Landmasses will contribute to the realization of boundary and orogenic belt on the northern margin of the Qinghai—Tibet block. It is a very important scientific subject.The Longshoushan Mt., longer than 150km in NWW direction and wider than 10km, is located on the northern side of Hexi corridor(100 5°～102 5°E,38 5°～39 3°N). It extends from the northwest of Zhangye to Hexibu, and from the south of Chaoshui basin to the north of Minle basin. From west to east, there are the highest peak, Dongdashan Mt.(3616m), the second peak, Dufengding(2937m) and Qianshan peak(2827m), height of the mountains is getting lower and lower, mean height above sea level is over 2000m, and relative height difference is about 1000m. The Longshoushan Mt. provides a natural defence for stopping the southward migration of sandstorm in the Hexi corridor, and forms a topographic step zone from the Alashan Plateau to the Qinghai—Tibet Plateau. In the Longshoushan area, developed landforms, such as planation surface, table\|land, terrace land, are general characters of all geomorphic units. It is shown that the Longshoushan Mt. is a intermittently uplifted block. An astonishingly similar of geometric patterns of Taohualashan Mt. and Hongshihu basin is very interesting natural landscape in the area. It is suggested that Taohualashan Mt. broke away from Hongshihu Basin in secular tectonic movement. The viewpoint is supported by major formation, lithofacies, limitation and style of active faulting. The Longshoushan block consists of two major active fault zones (the northern Longshoushan fault zone and the southern Longshoushan fault zone), the active Pingshanhu—Hongshihu fault basin belt and Taohualashan—Xieposhan tectonic uplift belt. In addition, there are the NNW\|trending West Polamading fault, NWW\|trending Maohudong fault trough, NNE\|trending Daxiahe rift valley and others on the block. the activity and formation style of these structures indicate that the block is acted not only by compressive stress, but also by tensile stress. The northern Longshoushan and southern Longshoushan fault zones are closely related to formation and evolution of the Longshoushan block, the two zones are active fault zones since late Pleistocene and boundary fault zones of the block. The genesis and activity style of the Pingshanhu\|Hongshihu basin are similar to the continental rift, which may be due to the mantle uplift.

Late Cenozoic Stratigraphy and Paleomagnetic Chronology of the Zanda Basin,Tibet, and Records of the Uplift of the Qinghai-Tibet Plateau

The characteristics of Late Cenozoic tectonic uplift of the southern margin of the Qinghai- Tibet Plateau may be inferred from fluvio-lacustrine strata in the Zanda basin, Ngari, Tibet. Magnetostratigraphic study shows that the very thick fluvio-lacustrine strata in the basin are 5.89- 0.78 Ma old and that their deposition persisted for 5.11 Ma, i.e. starting at the end of the Miocene and ending at the end of the early Pleistocene, with the Quaternary glacial stage starting in the area no later than 1.58 Ma. Analysis of the sedimentary environment indicates that the Zanda basin on the southern Qinghai-Tibet Plateau began uplift at -5.89 Ma, later than the northern Qinghai-Tibet Plateau. Presence of gravel beds in the Guge and Qangze Formations reflects that strong uplift took place at -5.15 and -2.71 Ma, with the uplift peaking at -2.71 Ma.

Effects of warming and clipping on plant and soil properties of an alpine meadow in the Qinghai-Tibetan Plateau, China

Climate warming and livestock grazing are known to have great influences on alpine ecosystems like those of the Qinghai-Tibetan Plateau （QTP） in China. However, it is lacking of studies on the effects of warming and grazing on plant and soil properties in these alpine ecosystems. In this study, we reported the related research from manipulative experiment in 2010-2012 in the QTP. The aim of this study was to investigate the individual and combined effects of warming and clipping on plant and soil properties in the alpine meadow ecosystem. Infrared radiators were used to simulate climate warming starting in July 2010, while clipping was performed once in Octo- ber 2011 to simulate the local livestock grazing. The experiment was designed as a randomized block consisting of five replications and four treatments： control （CK）, warming （W）, clipping （C） and warming＋clipping combination （WC）. The plant and soil properties were investigated in the growing season of the alpine meadow in 2012. The results showed that W and WC treatments significantly decreased relative humidity at 20-cm height above ground as well as significantly increases air temperature at the same height, surface temperature, and soil temperature at the depth of 0-30 cm. However, the C treatment did not significantly decrease soil moisture and soil temperature at the depth of 0-60 cm. Relative to CK, vegetation height and species number increased significantly in W and WC treatment, respectively, while vegetation aboveground biomass decreased significantly in C treatment in the early growing season. However, vegetation cover, species diversity, belowground biomass and soil properties at the depth of 0-30 cm did not differ significantly in W, C and WC treatments. Soil moisture increased at the depth of 40-100 cm in W and WC treatments, while belowground biomass, soil activated carbon, organic carbon and total nitrogen increased in the 30-50 cm soil layer in W, C and WC treatments. Although the initial responses of plant and soil properties to experimental warming and clipping were slow and weak, the drought induced by the down- ward shift of soil moisture in the upper soil layers may induce plant belowground biomass to transfer to the deeper soil layers. This movement would modify the distributions of soil activated carbon, organic carbon and total nitrogen However, long-term data collection is needed to further explain this interesting phenomenon.

On the Geodynamic Mechanism of Episodic Uplift of the Tibetan Plateau during the Cenozoic Era

Multi-stage uplift of the Tibetan Plateau during the Cenozoic implies a complex geodynamic process.In this paper,we review main geodynamic models for the uplift of the plateau,and,in particular,analyze the spatio-temporal framework of the Cenozoic deformation structures,which are closely related to the deep geodynamic mechanism for the plateau uplift.From this perspective,significant change of the deformation regime over the Tibetan Plateau occurred by the middle-late Miocene,while thrust and thrust-folding system under NS compression was succeded by extension or stress-relaxation.Meanwhile,a series of large-scale strike-slip faults commenced or was kinemtically reversed.Based on a systematic synthesis of the structure deformation,magmatism,geomorphological process and geophysical exploration,we propose a periodical model of alternating crustal compression and extension for episodic uplift of the Tibetan Plateau.

Impact of climate change on allowable bearing capacity on theQinghai-Tibetan Plateau

Climate change has a substantial impact on infrastructures in the permafrost on the Qinghai-Tibetan Plateau (QTP). In this study, the mean annual ground temperature (MAGT) and permafrost evolution were investigated in both the historical (1950-2005) and projected (2006-2099) periods. Then, an allowable bearing capacity model was used to discuss the allowable bearing capacity change on the QTP. Results show that the MAGT increased by 0.36 ℃ during 1950-2005. The MAGT will increase by 0.40 (RCP2.6), 0.79 (RCP4.5), 1.07 (RCP6.0), and 1.75 (RCP8.5)℃C during 2006-2099. In addition, the permafrost area has decreased by 0.195 × 10^6 km2 in 1950-2005. The permafrost area will decrease by 0.232 × 10^6 (RCP2.6), 0.468 × 10^6 (RCP4.5), 0.564 × 10^6 (RCP6.0), and 0.803 × 10^6 (RCP8.5) km2 during 2006-2099. With the degradation of permafrost, the allowable bearing capacity in permafrost zones would decrease accordingly. The decreasing trend is 6 kPa per 10 years in 1950-2005, and will be 0.6 (RCP2.6), 5 (RCP4.5), 7 (RCP6.0), and 11 (RCP8.5) kPa per 10 years during 2006-2099. The most remarkable trend would be observed under RCP8.5. Meanwhile, some scientific advices for the design, construction, operation and maintenance of permafrost engineering in the context of climate change were provided.