Southern Qinghai-Tibet Plateau Research Articles

Untangling the effects of management measures, climate and land use cover change on grassland dynamics in the Qinghai–Tibet Plateau, China

AbstractMultiple large‐scale ecological conservation programmes have been launched by the Chinese Government to combat grassland degradation across the Qinghai–Tibet Plateau (QTP) since 1999. However, the mechanisms by which these ecological initiatives might affect grassland changes remains unknown. Here, we examined the land use cover change (LUCC) and net primary productivity (NPP) of the grassland in the QTP in 2001–2016. The effects of LUCC, management measures, and climate variation on grassland NPP were quantitatively evaluated. The grassland area had a net increase of 96,397 km2, which could be attributed to the conversion of desert and forests. The total NPP of grassland increased by 154,073.7 GgC·yr−1 in 2001–2016, of which the contribution of climate and human factors occupied 35.58% and 64.42%, respectively. Specifically, climate variation caused an overall increase of 54,823.24 GgC·yr−1in grassland total NPP. The climate‐dominated NPP decrease was widely found in the eastern and southern QTP. The contribution of LUCC and management measures to the increase of grassland NPP was 62.78% and 37.22%, respectively. This increase was mostly found in the mid‐east region of the QTP, which could sufficiently counteract the negative effect of climate variation on NPP. Overall, these findings seem to demonstrate that these ecological restoration programs have substantially promote the increase of grassland NPP and contribute to understanding the degree to which the grassland ecosystem may respond to the LUCC and management measures under the ecological restoration projects, which are essential to developing more effective ecological measures for future grassland restoration in the QTP.

Diversity patterns of cushion plants on the Qinghai-Tibet Plateau: A basic study for future conservation efforts on alpine ecosystems

The Qinghai-Tibet Plateau (QTP) is an important cushion plant hotspot. However, the distribution of cushion plants on the QTP is unknown, as are the factors that drive cushion plant distribution, limiting our understanding of the evolution of cushion species in the region. In this study, we assessed spatial patterns of total cushion plant diversity (including taxonomic and phylogenetic) over the entire QTP and compared patterns of diversity of cushion plants with different typologies (i.e., compact vs. loose). We also examined how these patterns were related to climatic features. Our results indicate that the southern QTP hosts the highest total cushion plant richness, especially in the south-central Hengduan Mountains subregion. The total number of cushion species declines from south to north and from southeast to northwest. Compact cushion plants exhibit similar patterns as the total cushion plant richness, whereas loose cushion plants show random distribution. Cushion plant phylogenetic diversity showed a similar pattern as that of the total cushion plant richness. In addition, cushion plant phylogenetic community structure was clustered in the eastern and southwestern QTP, whereas random or overdispersed in other areas. Climatic features represented by annual energy and water trends, seasonality and extreme environmental factors, had significant effects on cushion plant diversity patterns but limited effects on the phylogenetic community structure, suggesting that climatic features indeed promote the formation of cushion plants. Because cushion plants play vital roles in alpine ecosystems, our findings not only promote our understanding of the evolution and formation of alpine cushion plant diversity but also provide an indispensable foundation for future studies on cushion plant functions and thus alpine ecosystem sustainability in the entire QTP region.

Improving estimation of soil organic matter content by combining Landsat 8 OLI images and environmental data: A case study in the river valley of the southern Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau (QTP) is a typical ecologically fragile area. Once the surface vegetation degenerates, it may not be restored. This requires the development of soil organic matter (SOM) monitoring method without destroying the surface, so as to ensure the sustainable development of plateau agriculture. This work investigated the environmental factors that are significantly related to SOM content in the river valley of the southern QTP. These environmental factors include soil hydrothermal factors (soil moisture content and soil temperature), topographic factors (elevation and slope) and vegetation factor (NDVI). The original band reflectivity (OR) of Landsat 8 OLI images and the band reflectivity after the first-order derivative (FDR) and the second-order derivative (SDR) processing were combined with the above environmental factors to estimate SOM content. The results showed that the accuracy of the model was improved obviously by adding environmental factors. The estimation effect of back propagation neural network (BPNN) model was better than that of geographically weighted regression (GWR) model, partial least squares regression (PLSR) model and multivariable linear regression (MLR) model. GWR model can also meet the estimation requirements, while PLSR and MLR models cannot achieve effectively the estimation of SOM content. FDR-BPNN model considering environmental factors was the best model for estimating SOM content, with R2 being 0.947, RMSEC being 4.701 g·kg−1 and MAEV being 5.485 g·kg−1. Moreover, the model had the lowest uncertainty and the highest stability. This study will provide a good insight for the monitoring of SOM content in the future, and provide basic data support for the implementation of precision agriculture in the QTP.

Increasing sensitivity of alpine grasslands to climate variability along an elevational gradient on the Qinghai-Tibet Plateau

Monitoring and mapping the sensitivity of grassland ecosystems to climate change is crucial for developing sustainable local grassland management strategies. The sensitivity of alpine grasslands to climate change is considered to be high on the Qinghai–Tibet Plateau (QTP), yet little is known about its spatial pattern, and particularly the variations between different elevations. Here, based on the Normalized Difference Vegetation Index (NDVI) and three climate variables (air temperature, precipitation, and solar radiation), we modified a vegetation sensitivity index-approach to capture the relative sensitivity of alpine grassland productivity to climate variability on the QTP during 2000–2016. The results show that alpine grasslands on the southern QTP are more sensitive to climate variability overall, and that the climate factors driving alpine grassland dynamics are spatially heterogeneous. Alpine grasslands on the southern QTP are more sensitive to temperature variability, those on the northeastern QTP display strong responses to precipitation variability, and those on the central QTP are primarily influenced by a combination of radiation and temperature variability. The sensitivity of alpine grasslands to climate variability increases significantly along an elevational gradient, especially to temperature variability. This study underscores that alpine grasslands at higher elevations on the QTP are more sensitive to climate variability than those at lower elevations at the regional scale.

Phylogeography of the threatened tetraploid fish, Schizothorax waltoni, in the Yarlung Tsangpo River on the southern Qinghai-Tibet Plateau: implications for conservation

The phylogeography of Schizothorax waltoni, an endemic and endangered tetraploid schizothoracine fish in the Yarlung Tsangpo River (YLTR) on southern margin of Qinghai-Tibet Plateau (QTP), was investigated using two mitochondrial DNA regions and eleven microsatellite loci. Analyses of concatenated sequences of cytochrome b (1141 bp) and the control region (712 bp) revealed high haplotype diversity and moderate nucleotide diversity. High genetic diversity was observed based on microsatellite variation. Both mtDNA and microsatellite analyses revealed significant genetic differentiation between the eastern population (Mainling) and the other four populations to the west, and non-significant genetic differentiation amongst the three central populations in the west. Significant genetic differentiation was observed between the western population (Shigatse) and the three central populations based on microsatellite analyses alone. Bayesian skyline plot analyses showed that S. waltoni experienced a pronounced population expansion 0.05 to 0.10 Ma. Hierarchical structure analyses of microsatellite data indicated that S. waltoni could be split into three groups (western, central and eastern YLTR). The results indicate that three management units should be considered for S. waltoni. Our findings highlight the need for the conservation and effective management of S. waltoni, which is a key member of the endemic and highly threatened fishes of the QTP.

Electrical conductivities of two granite samples in southern Tibet and their geophysical implications

There are clear differences in the electrical conductivities of the crustal granites of the Qinghai-Tibet Plateau. Because these granites are among the major rock types on the Qinghai-Tibet Plateau, it is very important to detect the electrical conductivity of granites under high temperatures and pressures to study the electrical conductivity structure of this area. Using impedance spectroscopy at a frequency range of 10−1–106 Hz, the electrical conductivity of the muscovite-granite collected from Yadong was investigated at a confining pressure of 1.0 GPa and temperatures ranging from 577 to 996 K, while the electrical conductivity of the biotite-granite collected from Lhasa was investigated at a pressure of 1.0 GPa and temperatures ranging from 587 to 1382 K. The calculated activation enthalpies of the Yadong muscovite-granite sample is 0.92 eV in the low-temperature range (577–919 K) and 2.16 eV in the high-temperature range (919–996 K). The activation enthalpies of the Lhasa biotite-granite sample is 0.48 eV in the low-temperature range (587–990 K) and 2.06 eV in the high-temperature range (990–1382 K). The change in the activation enthalpies of the granites at different temperature ranges may be associated with the dehydration of the two samples. The electrical conductivities of the granite samples obtained in the laboratory using impedance spectroscopy correspond well with field observations conducted near the sampling points, both in terms of the actual conductivity values and the observed variations between the low-temperature and high-temperature regimes. This correlation of laboratory and field conductivities indicates that the conductivities of the crustal rocks in the two regions closely correspond to granite conductivities. We calculated the electrical conductivities of muscovite-granite and biotite-granite samples using the effective medium and HS boundary models. When applied to the crustal rocks of southern Tibet, the results of the geophysical conductivity profiles lie within the range of laboratory data. Thus, the electrical characteristics of the crustal rocks underlying the southern Qinghai-Tibet Plateau can largely be attributed to granites, with the large changes to high conductivities at increasing depths resulting from the dehydration of crustal rocks with granitic compositions.

Monitoring surface deformation over permafrost with an improved SBAS-InSAR algorithm: With emphasis on climatic factors modeling

Abstract Changes of permafrost not only affect regional and global water circulation, carbon deposit and climate warming, but also influence ground ecological, geophysical, and biogeochemical processes in cold region. Monitoring surface deformation over permafrost will help to understand the dynamics of these processes, assess climate changes, and prevent potential damages to engineering structures underlain by permafrost. This article employs an improved small baseline subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) technique to monitor the surface deformation over the Danxiong-Yangbajing area in the southern Qinghai-Tibet Plateau (QTP), with emphasis on climatic factors modeling. A new deformation model considering both the external (mainly climatic) and internal factors (such as tectonic activities and thermal character of frozen soil) is constructed and introduced into the SBAS-InSAR to estimate the surface deformation over permafrost. The results show that the peak-to-peak annual deformation over natural surface is 3.6–5.0 cm, while that along the Qinghai-Tibet Highway (QTH) and the Qinghai-Tibet Railway (QTR) is 2.8–3.7 cm. We also find that the surface deformation over frozen soil is negatively correlated to air temperature and precipitation, with the correlation being − 0.80 to − 0.45 and − 0.95 to − 0.75, respectively. The root mean squares (RMSs) of the residual (un-modeled) deformation got by the proposed method are much smaller than that by the existing methods. We also successfully examine a time lag of about 60 days between the retrieved maximal subsidence and the highest air temperature in warm seasons (from May to September). After compensating for this time lag, the RMSs of the residual deformation reduce significantly and the correlation between the deformation and the temperature rises considerably, varying from − 0.95 to − 0.65. The method presented in this paper is more suitable to model and analyze the surface deformation in permafrost areas.

Taxonomic status of a population of Gymoncypris waddelli Regan, 1905(Cypriniformes: Schizothoracinae) distributed in Pengqu River, Tibet, China.

Gymnocypris waddelli, a highland cold-water fish, is distributed among rivers and lakes of the southern Qinghai-Tibet Plateau. Although previously described as G. waddelli, specimens from the Pengqu River are morphologically distinguishable from those from Lake Yamzhog Yumco, which is the type locality of G. waddelli. We investigated morphological variations of G. waddelli specimens from Pengqu River and Lake Yamzhog Yumco using not only traditional morphological methods but also newly-developed geometric morphometric analysis; furthermore, mitochondrial Cytochrome b (Cyt b) gene analysis was employed to explore the phylogenetic position of the Pengqu River population. Our morphological analyses suggested that G. waddelli from the Pengqu River had an obtuse snout, nearly straight oral fissure, shorter lower jaw than upper jaw, broad mouth and sparse inside gill rakers of the first arch relative to the Lake Yamzhog Yumco population. The strongly supported monophyly of Pengqu population according to mitochondrial datasets was obtained, indicating genetic differences between Pengqu River and Lake Yamzhog Yumco populations. Given their substantial genetic and morphological divergence, specimens from Pengqu River warrant recognition as a distinct species, here described and named Gymnocypris pengquensis.

InSAR analysis of surface deformation over permafrost to estimate active layer thickness based on one-dimensional heat transfer model of soils.

This paper presents a novel method to estimate active layer thickness (ALT) over permafrost based on InSAR (Interferometric Synthetic Aperture Radar) observation and the heat transfer model of soils. The time lags between the periodic feature of InSAR-observed surface deformation over permafrost and the meteorologically recorded temperatures are assumed to be the time intervals that the temperature maximum to diffuse from the ground surface downward to the bottom of the active layer. By exploiting the time lags and the one-dimensional heat transfer model of soils, we estimate the ALTs. Using the frozen soil region in southern Qinghai-Tibet Plateau (QTP) as examples, we provided a conceptual demonstration of the estimation of the InSAR pixel-wise ALTs. In the case study, the ALTs are ranging from 1.02 to 3.14 m and with an average of 1.95 m. The results are compatible with those sparse ALT observations/estimations by traditional methods, while with extraordinary high spatial resolution at pixel level (~40 meter). The presented method is simple, and can potentially be used for deriving high-resolution ALTs in other remote areas similar to QTP, where only sparse observations are available now.

Research on the changes of the tidal force and the air temperature in the atmosphere of Lushan (China) Ms7.0 earthquake

The cycle process of the tidal force of celestial body for Lushan M7.0 earthquake, occurred in Lushan county of Sichuan, China on April 20, 2013 was calculated. The earthquake occurred at the lowest point phase. It indicated that the type of seismogenic fault that the tide force acted on belonged to the thrust fault. According to the tidal cycle, the abnormal air temperature change was analyzed based on NCEP satellite data around the whole China before and after the earthquake. The result showed that the air temperature changed evidently with the tide force changing. In temporal, the change went through: initial air temperature rise → strength→ reaching abnormal peak→ gradually decline; in spatial, the abnormal area winded its way along the margin of the southern Qinghai-Tibet Plateau and went through: scattered→ conversion→ scattered procession. The procession was similar to the change procession of a rock breaking under the stress loading. This shows that the stress change of rock may cause the air temperature change in the atmosphere before and after earthquake. It indicated that the tidal force of celestial body could trigger the earthquake, when the tectonic stress reaches its critical broken point and the air temperature anomaly was proportional to the seismic tectonic stress change. It was useful to combine air temperature and tidal force in earthquake precursory.

Cryptic and repeated “allopolyploid” speciation within Allium przewalskianum Regel. (Alliaceae) from the Qinghai-Tibet Plateau

Polyploidization has contributed greatly to current plant diversity. Allopolyploid speciation, which can rapidly overcome meiosis abnormalities, is a common and repeated process in numerous genera. However, most polyploids within a single morphological/taxonomic species have been considered autopolyploids, which were assumed to arise through spontaneous genome doubling and/or following the fusion of unreduced diploid gametes. It remains untested whether these intraspecific polyploids may also be the result of ‘allopolyploid’ hybridizations between differentiated diploid populations and whether such speciation has also occurred repeatedly. In this study, we examined the diploid–tetraploid species Allium przewalskianum on the Qinghai-Tibet Plateau (QTP) to test this cryptic speciation hypothesis under morphological stasis, based on three sets of nuclear genetic data (AFLP, ITS, and CHS) and niche modeling. Our analyses of the three datasets together revealed that the diploid populations across the northeastern to southeastern QTP exhibit strong geographical differentiation. Based on the shared nuclear lineages fixed in the different diploids, three tetraploid groups in the northern, southern, and eastern QTP were identified as having originated independently, through “allopolyploid” hybridization between the differentiated diploids. Ecological niche modeling based on ecological variables suggested distinct niche differentiation between two tetraploid groups in the northern and southern QTP and also between these and the diploid populations. Furthermore, they also differed in their responses to past climate changes. These findings together suggested that at least two tetraploid groups had originated independently through hybridizations between the differentiated diploid populations. Our results highlight the cryptic allopolyploid speciation underlying a single morphological species, which mirrors well the repeated allopolyploid speciations within the genus. This allopolyploid speciation may prevail within the diploid–polyploid species complex that is classified as a single morphological species; indeed, the underlying cryptic speciation and evolutionary dynamics are certainly more complex than previously assumed.

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

Abstract: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 lithostratigraphic 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–Garzê and Gangdisê 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 Gangdisê–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‐Garzê, 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.

Response of the East Asian climate system to water and heat changes of global frozen soil using NCAR CAM model

Under the condition of land-atmosphere heat and water conservation, a set of sensitive numerical experiments are set up to investigate the response of the East Asian climate system to global frozen soil change. This is done by introducing the supercooled soil water process into the Community Land Model (CLM3.0), which has been coupled to the National Center of Atmospheric Research Community Atmosphere Model (CAM3.1). Results show that: (1) The ratio between soil ice and soil water in CLM3.0 is clearly changed by the supercooled soil water process. Ground surface temperature and soil temperature are also affected. (2) The Eurasian (including East Asian) climate system is sensitive to changes of heat and water in frozen soil regions. In January, the Aleutian low sea level pressure circulation is strengthened, Ural blocking high at 500 hPa weakened, and East Asian trough weakened. In July, sea level pressure over the Aleutian Islands region is significantly reduced; there are negative anomalies of 500 hPa geopotential height over the East Asian mainland, and positive anomalies over the East Asian ocean. (3) In January, the southerly component of the 850 hPa wind field over East Asia increases, indicating a weakened winter monsoon. In July, cyclonic anomalies appear on the East Asian mainland while there are anticyclonic anomalies over the ocean, reflective of a strengthened east coast summer monsoon. (4) Summer rainfall in East Asia changed significantly, including substantial precipitation increase on the southern Qinghai-Tibet Plateau, central Yangtze River Basin, and northeast China. Summer rainfall significantly decreased in south China and Hainan Island, but slightly decreased in central and north China. Further analysis showed considerable upper air motion along ∼30°N latitude, with substantial descent of air at its north and south sides. Warm and humid air from the Northeast Pacific converged with cold air from northern land areas, representing the main cause of the precipitation anomalies.

Variation of GPS Precipitable Water over the Qinghai-Tibet Plateau: Possible Teleconnection Triggering Rainfall over the Yangtze River Valley

GPS technologies show many capabilities for monitoring atmospheric water vapor. This study uses GPS data from the Japan International Co-operation Agency (JICA) and Hubei GPS network to monitor precipitable water (PW) over the Qinghai-Tibet Plateau (QTP) and over the middle Yangtze River Valley (YRV). The results show that the southern QTP is wetter than the central area due to the barring effect of the Plateau on the monsoon. PW is higher in summer than other months over either the QTP or the middle YRV. The diurnal variation of PW over the QTP is more complex than that of the middle YRV with fluctuations occurring during the whole day due to the unique topography. The minimum PW over both the QTP and the middle YRV appears in the morning; however, the peak over the QTP occurs at night while the peak over the middle YRV occurs in the early afternoon. Furthermore, PW over the QTP, especially its southern and eastern edges, are positively correlated with PW over the middle YRV. This may imply that the southern and eastern Plateaus are key regions transporting atmospheric vapor to the middle YRV. Our results indicate the possibility of finding early warning signals resulting from the intensification of the QTP atmospheric vapor leading to heavy rainfall events over the middle YRV.

Sr fluxes and isotopic compositions of the eleven rivers originating from the Qinghai-Tibet Plateau and their contributions to 87Sr/86Sr evolution of seawater

To evaluate influence of chemical weathering of the Qinghai-Tibet Plateau (QTP) on seawater 87Sr/86Sr variation, river water and sediment samples were collected, and their Sr concentrations and isotopic compositions analyzed, from the seven large rivers that originated from the QTP. By combining these with the data of the Ganges, Brahmaputra, Indus and Irrawaddy originated in the southern QTP, the total Sr flux of the eleven rivers reaches 3.47×109 mol·a−1, which accounts for 10.2% of the total Sr flux transported by the global rivers. The weighted mean 87Sr/86Sr is 0.71694, higher than the average value of the global rivers. The 87Srex (87Sr flux in excess of the seawater 87Sr/86Sr ratio) of the Chinese seven rivers is 1.55×106 mol·a−1, only accounting for about 6% of the value of the eleven rivers originated from QTP, and the Ganges-Brahmaputra system accounts for 86%. We assume that the QTP rivers have no strontium contributions to the oceans before ∼40 Ma and the Sr fluxes of the global rivers, except the QTP eleven rivers, are constant, then a maximum linear increase in Sr fluxes of the QTP rivers from zero to the modern value in response to tectonic uplift can explain ∼69% increase of seawater 87Sr/86Sr over the past ∼40 Ma and the remainder of 31% is perhaps provided from other factors.

Coupling and Formation Mechanism of Continental Intraplate Basin and Orogen—Examples from the Qinghai–Tibet Plateau and Adjacent Basins

There are very close relationships between orogenic belts and their peripheral sedimentary basins: they are spatially interdependent in structure, mutually compensatory in material, interactive in tectonics, simultaneous in tectonic evolution. The relationships indicate a unified formation mechanism for the continental orogenic belts and the sedimentary basins, which can be presented as follows: lower crustal ductile lateral flow from the basin to the orogen, driven by thermal energy related to upwelling mantle plume in the intracontinental crust and by vertical diaper movement of dehydration and magma of the subduction plate on the active continental margin, results in the circulative movement of crust materials between basins and orogens. The coupling between the Qinghai–Tibet Plateau and its peripheral basins is a typical basin-orogen coupling occurring in the intraplate tectonic setting. The formation of the Qinghai–Tibet Plateau is not a result of collision between the India plate and the Eurasia plate, but rather the result of intraplate basin-orogen formation process driven by lower crustal flow. The tectonic evolution of intraplate basin-orogen system in the Qinghai–Tibet Plateau can be divided into two stages: (1) intraplate orogen-basin formation stage. During this stage, the spatial and temporal evolution of the intraplate orogens and basins in the Qinghai–Tibet Plateau is indicated by the successive geographic movement of the locations of the new basin-orogen systems from the northern and eastern, to the central, and finally to the southern Qinghai–Tibet Plateau, corresponding geochronologically to periods from 180–120 Ma, to 65–30 Ma, and finally to 23–7 Ma. This stage was manifested by extensive intraplate faulting, folding, block movement, magmatism and metallogeny. (2) isostatic mountain building and basin margin subsidence stage. In this stage, there were rapid uplift and strong erosion of the entire Qinghai–Tibet Plateau and rapid subsidence and molasse formation in the depressions on the margins of the peripheral basins resulted from gravity isostasy since 3.6 Ma. The stage is characterized by pulsative uplift and subsidence, crust-scale vertical movement, integral rapid uplifting of the Plateau, local subsiding of basin margin, and tremendous change in topography and environment, with pulses at 3.6 Ma B.P., 2.5 Ma B.P., 1.8–1.2 Ma B.P., 0.8 Ma B.P., 0.15 Ma B.P., etc. The intracontinental basin-orogen systems also underwent tectonic transformation from extension to compression, and the active movement respectively changed from the basin to the orogen. Non-Anderson low-angle detachment, wavy thrust faults, and abnormal conjugate strike-slip faults are formed due to lower crustal flow and intraplate basin-orogeny coupling.

Lg Coda Q Variation across the Myanmar Arc and its Neighboring Regions

Regional seismograms were collected to image the lateral variations of Lg coda Q at 1 Hz (Q0) and its frequency dependence η across Burma and its neighboring regions. The data include 660 vertical-component traces recorded at 39 stations. The resulting image indicates that Lg coda Q, at a frequency of 1 Hz, varies between 100 and 500. Lowest Q values ( 250) are found in the eastern Indian block. From the Lg coda Q tomography, we found that (1) The Sagain fault acts as a rough boundary between the eastern Indian plate and the Three rivers area of the Eurasia plate; (2) near the eastern Himalayan syntaxis, higher Q value appears in the background of relatively low Q (which may be the consequence of the northward intrusion of the Assam block of the Indian plate into the southern Qinghai-Tibet plateau.

Introduction to recent advances in regional geological mapping (1:250, 000) and new results from southern Qinghai-Tibet Plateau

A large volume of new geological data has been obtained in the process of new round of geological surveys (at a scale of 1:250, 000) and other geoscientific studies in southern QinghaiTibet Plateau ( Wang et al. 2004). The new results and achievements provide stable bases that are beneficial for understanding the principles governing the geological processes and verifying them in the Qinghai-Tibet Plateau. Significant data on the spatio-temporal distribution of the regional primary junction belts (suture zones) and faults also serve as the base for basic geological information required to establish a workable geotectonic framework for Qinghai-Tibet Plateau. The discovery of high-pressure granulites and lots of data on isotope chronology of Precambrian metamorphic rocks offer new insights to discuss the formation mechanism and exhumation process of the metamorphic basement in the southern Tibet. Findings of new strata and confirmation of already known strata containing abundant fossils provide new evidences to establish a regional stratigraphic system that will be used for geological classification and comparison. Likewise, discovery of some magmatic rock types and isotope-based age data on them enable to reconstruct the process of evolution and also propose a spatiotemporal framework for the magmatic rocks. Newly discovered unconformities and sedimentary facies or the verification of existing ones together with the associated geological information are fundamental for the analysis of sedimentary basin and for the paleogeographic reconstruction of tectonic lithofacies. The results and progresses in Quaternary geological mapping at regional scale and also in studying the neotectonic movements will be useful for deciphering the history of uplift of Plateau, the changes in the paleoenvironments and also the development of lakes in the geological past. Additional progress in finding the relics of ancient human activity, deciphering zoological environments and also studying the geology of regions of touristic importance has been made. These will be definitely valuable for research on zoological environment and ancient human civilization of Qinghai-Tibet Plateau and also for regional economic development. Besides these discoveries, new information on mineralization gained through the regional geological surveys will serve as guidelines for undertaking necessary action to explore and develop the mineral resources and also for appraisal of important metallogenic regions and belts in Qinghai-Tibet Plateau.