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The western area of the Chinese Loess Plateau (CLP) is close to the northeastern margin of the Tibetan Plateau (NTP) and arid regions of northern China. Loess-paleosol sequence is a good archive for studying the variation of the East Asian summer monsoon (EASM) and the evolutionary history of paleoclimate. However, excessive remagnetization makes it challenging to infer the location of the time-scaled strata, and only a few high-resolution long scale paleomagnetic data are available from the western CLP. To solve this problem, this paper presents a study on establishing a Quaternary chronological framework using the traditional paleomagnetic method and quartz electron spin resonance (ESR) dating. The result is validated by comparing sequences in a variation of magnetic susceptibility and grain-size. Detailed thermal demagnetization records show that declination is reversed, but the inclination reversal is not apparent between S7 and S8. ESR estimated that the three samples collected at a depth of ∼112–145 m were 853.51 ± 133.43 ka, 962.12 ± 144.30 ka, and 1004.27 ± 206.86 ka, respectively. Constrained by these ESR dates, the age of the L9-L15 is defined as ∼0.9–1.2 Ma, which is corroborated the observation in the field stratigraphic survey, the characteristics of magnetic susceptibility and grain-size data. Based on these ages, the Matuyama and Brunhes boundary (MBB, ∼0.78 Ma) is deduced in L8 as inferred from the declination sequence. The bottom age of the loess-paleosol sequence extrapolated from the sedimentation rate is 2.13 Ma. The chronological sequence is therefore established. Several environmental indexes were changed coordinately in broad areas based on the chronological framework, indicating that it is logical and reliable. [ABSTRACT FROM AUTHOR]

The lightning clustering algorithm for spaceborne lightning observations clusters events into flash products and plays a crucial role in lightning-related research. This paper modified the lightning clustering algorithm based on the routine algorithm of Lightning Mapping Imager (LMI) and applied it to lightning events recorded by the LMI in 2019 to study the flash duration and flash area and specially to reveal the extreme lightning. To reveal the temporal and spatial features of lightning, the MCA (modified cluster algorithm) flash products defined flash duration and flash area. The results showed that continental regions have higher lightning frequencies but smaller events per flash, flash durations and flash areas than the ocean. The Tibetan Plateau has a low lightning frequency and smaller flash duration and area than eastern China. The flash count, events per flash, flash duration and flash area are higher during nighttime than during daytime. The relationship between flash duration and flash area showed distinct regional differences. In the MCA flash product, about 0.6% (0.1%) flashes have duration (area) that exceeds 1.0 s (5,000 km2). Finally, we analyzed two extreme lightning cases in eastern China, where the longest flash duration was 4.748 s and the largest flash area was 17,100 km2. This research contributes to advancing our understanding in the features of space-based lightning in the Eastern Hemisphere and applications to convection study. • Clustering algorithm was modified to study lightning with extreme duration and area. • Lightning duration and area both implied regional differences. • Quantitative relationship of duration and area was established in different regions. • The longest flash duration/largest flash area was 4.75 s/17100 km2 in eastern China. [ABSTRACT FROM AUTHOR]

The Qiangtang Basin is one of the largest Mesozoic petroliferous basins in China that is still unexploited for the petroleum industry. The basic geological issues and synthesis of the Qiangtang Basin related to the Tethyan evolution are still poorly understood. This volume presents 20 research papers to address the tectonic settings, basin evolution, and sedimentary environments of the Qiangtang Basin, which are key factors for a better understanding of the overall petroleum system. The Qiangtang Basin holds a Precambrian base developed in response to the Paleo-Tethys Hol Xil-Jinshajiang Ocean evolution, with enhanced sedimentary basin infilling during the opening and expansion of the Neo-Tethys Bangong-Nujiang Ocean in the Mesozoic. The Paleozoic basin framework of the Qiangtang demised as the Paleo-Tethys Ocean closed at the latest Permian, while the Early-Middle Triassic foreland basin underwent a negative basin inversion during the Late Triassic. The latter initiated a new sedimentary filling cycle of the Qiangtang Basin, which was triggered by the active extensional rifting and the onset of the bimodal volcanic eruption. Recent scientific exploratory drilling (QK-1 well) found that the Qiangtang Basin is characterized by multiple source rocks, of which the upper Triassic Bagong Formation and the lower Quse Formation exhibit the most hydrocarbon generation potential. The development of high quality and quantity source rocks in the Qiangtang Basin is ensured by regional to global-scale bottom-water anoxia and high primary productivity in the eastern Tethys realm in the Late Triassic and the Early Jurassic. The main reservoirs in the Qiangtang Basin include the Middle Jurassic reef-beach facies, the Upper Triassic carbonates, and the Lower Jurassic terrestrial clastic rocks. Two very-thick caprocks of gypsum in the Lower Jurassic and gypsum mudstones in the Middle Jurassic strata are found during the scientific drilling, which is interpreted as favorable regional-scale seals for petroleum entrapment in the Qiangtang Basin. [ABSTRACT FROM AUTHOR]

Geofluids from natural springs connect with the crust and/or mantle in many cases, and their geochemical anomalies could be significant for the study on faults activity and even earthquakes. Several natural springs are distributed along the Lenglongling fault zone (LLLFZ) in the northeastern margin of the Tibetan Plateau, where the M s 6.9 Menyuan earthquake occurred on January 8th, 2022. Based on chemical and isotopic compositions (δD, δ18O, δ13C, and 3He/4He) of water and gas samples, the origin of geofluids and their potential correlation with fault activity even including earthquakes are preliminarily assessed in this paper. The δ13C CO2 values and 3He/4He ratios showed that the gas originating from the crust was associated with the metamorphism of carbonate rocks, whereas the δ18O and δD values of water samples indicated that the natural springs were predominantly infiltrated with precipitations from local mountains ranging 3.7 - 5.5 km in height. Obvious changes of Ca2+ and HCO 3 − concentrations in SZK spring waters in the surface rupture zones were observed in a short period (about three months) after the main shock, in contrast to those of the GSK springs far from the surface rupture zones. Such variations might be correlated with the stress increase prior to the 2022 Menyuan M s 6.9 earthquake. The mechanical fracturing of surrounding limestone rocks during the slipping movement of LLLF could facilitate the water-rock interactions. Compared to three-month observations after the main shock, relatively higher concentrations of HCO 3 − and heavier δ18O H 2 O values of the LHG springs were also observed in the short-term period. The shallow stored formation water might be squeezed along the cracks and rose to the surface during earthquake tremors, causing a sandblasting water phenomenon. • Ionic concentration of spring water showed anomalies with Menyuan M S 6.9 earthquake. • Two distinct causes of hydro-chemical anomalies revealed. • Bubbling CO 2 originated mainly from metamorphic and weathering carbonate in the crust. [ABSTRACT FROM AUTHOR]

The Qilian-Qaidam Orogenic Belt is a component of the western Central China Orogenic Belt, and records a nearly complete evolutionary history of the South Qilian and North Qaidam oceans (branches of the Proto-Tethyan Ocean). However, the timing and process of amalgamation of the microblocks of the western Central China Orogenic Belt and the closure time of the South Qilian and North Qaidam oceans remain uncertain. The Olongbuluke Terrane (OLT), located in the central of the Qilian-Qaidam Orogenic Belt, contains well-developed Precambrian to Paleozoic sedimentary successions that shed light on the tectonic history of these ocean basins. In this paper, detrital zircon U Pb ages combined with ophiolitic, magmatic and high-pressure to ultrahigh-pressure metamorphic records and field investigations, indicate that the OLT was part of a passive continental margin during the early Paleozoic and there was a microblock, named the North Qaidam Terrane (NQT), lying between the Qaidam Block and the OLT. A marked provenance change occurs in the OLT after ca. 517 Ma, which is inferred to record the collision between the OLT and NQT. Later, the North Qaidam oceanic plate subducted under the NQT, and the North Qaidam Ocean closed at ca. 450 Ma. The similar detrital zircon U Pb age spectra of contemporaneous deposit flysch sequences in the Shihuigou Formation (OLT) and the Balonggonggaer Formation (the South Qilian Accretionary Belt) indicates the onset of collision between the OLT and Central Qilian Terrane occurred at ca. 458 Ma. The detrital zircon U Pb age spectra of microblocks from the early Paleozoic strata of the northern Tibetan Plateau share a North Indian affinity, indicating that the closure of the Proto-Tethyan Ocean may relate to the formation of the Gondwanan landmass. • The North Qaidam Terrane may exist between the Qaidam Block and the Olongbuluke Terrane. • The Olongbuluke Terrane collided to the North Qaidam Terrane at ca. 517 Ma. • The onset of collision between the Olongbuluke Terrane and the Central Qilian Terrane at ca. 458 Ma. • The closure of Proto-Tethys may relate to the formation of the Gondwana landmass. [ABSTRACT FROM AUTHOR]

This paper examines the local and non-local climatic effects of wetter arid areas of Northwestern China (ANWC) in summer using a fully coupled climate model. In response to soil moisture increase, the local air temperature significantly decreases, and precipitation increases in summer. The wetter ANWC results in a warmer and rainless climate over the Central part of North China Plain (CNCP). While the influence of increasing soil moisture on the Tibetan Plateau (TP) precipitation is negligible due to the high altitude. A cooler climate over ANWC leads to an abnormal descending motion occurring. Meanwhile, an anomalous high pressure and an abnormal anticyclonic circulation occurs in 500 hPa over the west of ANWC. Correspondingly, a huge anomalous cyclone circulation occurs over the northeastern part of China and Mongolia, which can hinder the northward movement of the East Asian summer Monsoon (EASM) and reduce the water vapor transport into Central China Plain. As a result, the weakened EASM thus leads to rainless over CNCP. As soil moisture increases over ANWC is stronger, the magnitudes of the influence on the atmospheric field become larger. This study highlights the wetter ANWC effect on local climate and provides more information about the mechanism of wetter ANWC remote effect on non-local climate. • This paper examines the local and non-local climatic effects of wetter arid areas of Northwestern China (ANWC) in summer using a fully coupled climate model. • It finds that the wetter ANWC can result in a warmer and rainless climate over the Central part of North China Plain (CNCP) through a complex atmospheric circulation response. • A cooler climate leads to an abnormal descending motion occurring over ANWC. • A huge anomalous cyclone circulation over the northeastern part of China and Mongolia can block the East Asian summer Monsoon northward and decrease the water vapor transport into Central China Plain. • This study highlights the wetter ANWC effect on local climate and provides more information about the mechanism of wetter ANWC remote effect on non-local climate. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The geometric distribution and activity of the Mengzi fault has been studied. • The horizontal slip rate of the fault has been obtained via the offset gullies and terraces. • Three paleo-events since 30–40 ka BP have been observed, with a 10-ka major earthquake recurrence period. • The Mengzi fault plays an important role in the adjustment of the large slip rate loss for the southern Xiaojiang fault. Abstract Few studies have been conducted on the activity of the Mengzi fault system, which is located to the southeast of the Sichuan-Yunnan block. The Mengzi fault is distributed along the eastern margin of the Mengzi basin. However, little is known about the location, length, and activity of the fault or the occurrence of paleo-earthquakes during the late Quaternary. This paper studies the geometric distribution and activity of the fault via remote sensing imagery interpretation, fault outcrops in the area, faulted landforms and chronological analyses. The results show that the Mengzi fault extends from Nandong (Kaiyuan basin) in the north through the eastern margin of the Mengzi basin to Pingbian in the southeast, eventually intersecting with the Honghe fault. The Mengzi fault is approximately 250 km long and is characterized as a reverse strike-slip fault. We survey and calculate the offset gullies and terraces dislocated by the fault; combined with sample dating, we calculate the horizontal slip rate of the fault since 30 ka BP to be 0.91–1.56 mm/a. Three paleo-events since 30–40 ka BP are observed with a 10-ka major earthquake recurrence period. We analyze the relationships among the Mengzi fault, southern Xiaojiang fault, and Qujiang-Jianshui fault and note a slip rate loss of ≥8 mm/a from the southern Xiaojiang fault that was absorbed by reverse dextral strike-slip faulting and lateral shortening of the Qujiang-Jianshui fault and the Mengzi fault. The Mengzi fault plays an important role in the adjustment of the large slip rate reduction along the southern Xiaojiang fault. Moreover, the Mengzi fault has a similar tectonic position to the seismogenic faults of the 2008 Wenchuan earthquake, 2013 Lushan earthquake and 2014 Ludian earthquake, and the Mengzi fault and southern Xiaojiang fault both accumulate the energy generated by the southeastward movement of the Sichuan-Yunnan block. Studies on the Mengzi fault are helpful for renewing our understanding of the tectonic patterns of the southeastern Sichuan-Yunnan block and delimiting the boundary of the southeastern block margin. Furthermore, because the cities of Mengzi and Kaiyuan are located along the Mengzi fault, this study has practical significance for earthquake disaster mitigation. [ABSTRACT FROM AUTHOR]

Farmer's ability to rapidly grow their populations has been seen as an advantage in allowing them to either engulf or simply do away with foragers. Research on agriculture's spread in East Asia has followed an underlying assumption: that farming produced equally reliable returns across the vast expanse of territories into which it spread. Farmers are thus always seen as being at a demographic advantage. However, in some parts of Asia, ecological barriers to growing crops may have meant that the opposite was true. In order to illuminate how foragers and farmers might have interacted in environments marginal to crop cultivation, I argue that we first need to outline where the barriers to farmer expansion in prehistory lay. Using ecological niche modeling combined with an analysis of recent archaeological data, this paper contrasts forager farmer interaction in two different areas of the Tibetan Plateau. It argues that the higher elevation reaches of the “third pole” constituted a barrier for early millet farmers expanding into the region. In these areas foragers may have maintained a competitive advantage. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the Holocene record of extreme flood events in the upper Minjiang River valley of the eastern Tibetan Plateau, China. Slackwater deposits (SWDs), the fine-grained sediments of palaeofloods, were identified within debris flow deposits at a tributary mouth and in channel expansions along the bedrock gorge. Eight palaeoflood SWDs were dated to between 6.0 ± 0.9 ka and 4.6 ± 0.9 ka using optically-stimulated luminescence analysis in combination with the minimum age model and represent at least two phases of palaeoflood events. The palaeoflood history in the upper Minjiang River Valley is consistent with the record of the mid-Holocene flood events in the mainstream of the Yangtze River. These mid-Holocene extreme flood events were closely related to strong ENSO activity and variability of the monsoon climate in the eastern Tibetan Plateau. In our study area, minimum palaeoflood discharges were estimated as 6500–7800 m3/s by the step-backwater method. These estimated discharges are less than the values inferred for the outburst flood that occurred in the upper Minjiang River Valley in 1933. Flood-inundation maps show that palaeoflood SWDs were deposited in low-velocity backwater zones. Our palaeoflood reconstructions are important for improving regional records of maximum flood and help to develop risk analysis for rare flood events. • Sedimentary characteristics of palaeoflood records in complex environment were identified. • Palaeoflood discharges were estimated to be 6500–7800 m3/s at the three study sites. • Palaeoflood results redefine the envelope curve of the regional maximum floods. • Response of mid-Holocene (6.0–4.6 ka) extreme flood events to climate variability. • Palaeoflood reconstructions help to develop risk analysis for rare flood events. [ABSTRACT FROM AUTHOR]

Abstract: Knowledge of the Little Ice Age (LIA) on the Tibetan Plateau (TP) is of critical importance for understanding the climate changes over the past millennium. However, the data associated with the extents and chronologies of TP LIA moraines are highly dispersed in literature. Lack of systematic integration of these data hampers us to further understand the nature of the LIA, especially from a perspective of whole TP. The paper reviews multiple types of dating on LIA moraines to examine the timing and nature of the LIA on the TP. These include ages of radiocarbon 14C, lichenometry, and cosmogenic radionuclide (CRN), by which we can cross-date the same or morphostratigraphically similar landforms. LIA moraines on the TP are usually present a few hundred to thousand meters beyond the contemporary glaciers. The morphological and stratigraphic evidence indicates multiple periods of glacier advance during the last millennium (LIA). At present, available chronology evidence allows to fully compare the timing of the LIA maximum extents. The glaciers reached and retreated from their LIA maximum extents by an asynchronous pattern between different parts of the TP. The majority of glaciers advanced to their LIA maximum extents at late-14th and early-14th century on the southern and northwestern TP, respectively. The glaciers retreated from their LIA maximum extents during 16th to early-18th, late-14th to early-15th and early-16th century on the southern, northwestern, and northeastern TP, respectively. In addition, the glacier advance period of late-18th to early-19th centuries and retreat period of late-19th century are common on the whole TP. Comparison with ice core records suggests that on the TP, the glacier fluctuations responded more strongly to temperature than to precipitation. By comparison of the LIA chronologies from a global perspective, this paper also concludes that the LIA maximum extents occurred commonly earlier on the TP than in North Atlantic and Southern Hemisphere regions, despite of the variability in the timing of LIA maximum extents on the TP and in the North Atlantic regions. Further, more chronology programs, especially in the central TP, are necessarily needed to improve our understanding of the LIA glacier fluctuations. [Copyright &y& Elsevier]

Abstract: What are the geodynamic processes that caused these deadly earthquakes? Why have these earthquakes caused so much damage? What are the key lessons that we have learned from these devastating earthquakes? Answers to these questions will significantly enhance not only our understanding of earthquake occurrence but also our ability to reduce seismic hazard. Under the framework of bi-lateral cooperation on earthquake sciences between China and USA, the Second Bi-Lateral Workshop on Earthquake Sciences was held in Chengdu, Sichuan Province, China, from April 22 to 25, 2011. Among the goals of this workshop was a review of recent advances in the study of great earthquakes and the exchange of ideas on earthquake disaster reduction. The principle theme of the workshop was “Great Earthquakes in the 21st Century and Geodynamics.” This Special Issue contains a total of 24 papers presented during the workshop. The contributions cover a wide-range of topics associated with the theme. This preface summarizes the main points of the papers presented in this issue. [Copyright &y& Elsevier]

The Nb-Ta-Zr-Hf-REY-Ga mineralization in the Late Permian coals in southwestern China has been well investigated by several studies and has generally been attributed to alkaline pyroclastics coupled with input from hydrothermal fluids. The Late Triassic is one of the important coal-forming periods but the critical element mineralization in coals of this geological age has not been well documented. In this paper, the mechanism of Nb-Ta-Zr-Hf-REE-Ga-Th-U mineralization in the K5 coal seam of the Upper Triassic Xujiahe Formation from the Gaosheng Mine, Sichuan Basin, southwestern China, was investigated. The K5 coal is a high-ash, low-sulfur, and low-volatile bituminous coal. The minerals in this coal include illite, kaolinite, quartz, and, to a lesser extent, anatase, calcite, chamosite, bassanite, and pyrite, along with traces of ankerite, rutile, and zircon. Compared with the averages of common world hard coals, the studied coals are enriched in critical elements including Zr (247 ppm), Hf (5.56 ppm), Nb (23 ppm), Ta (1.55 ppm), rare earth elements and yttrium (REY, 168 ppm), Ga (18.3 ppm), Th (14.1 ppm), and U (6.18 ppm) (all on a whole coal basis). The Al 2 O 3 /TiO 2 ratios, Eu anomalies, and the relationships of Al 2 O 3 /TiO 2 vs. Zr/TiO 2 and Nb/Yb suggest that the sediment-source rocks of the Gaosheng coals were Neoproterozoic and Early-Middle Triassic felsic-intermediate igneous rocks from the southeastern Qinling and Longmenshan Orogens, along with the Hannan and Micangshan-Dabashan Uplifts. Other probable sources are contemporaneous felsic-intermediate pyroclastics from the Late Triassic volcanic areas around the Sichuan Basin (i.e., East Kunlun Orogen, West Qinling Orogen, and East Tibetan Plateau). The relationships of Al 2 O 3 /TiO 2 vs. Zr/Al 2 O 3 , Al 2 O 3 /TiO 2 vs. Nb/Al 2 O 3 , Ga/Al 2 O 3 , and Al 2 O 3 /TiO 2 vs. LREY/Al 2 O 3 further indicate that the elevated concentrations of Nb(Ta)-Zr(Hf)-REY-Ga in the Gaosheng coal are probably sourced from both the erosion of sediment-source regions and contemporaneous pyroclastics. The illite-kaolinite aggregates with a vermicular texture and authigenic illite, quartz, anatase, pyrite, calcite, ankerite, barite, and REE-rich minerals, REY distribution patterns, as well as elemental variation trends of the coal seam, collectively indicate that the studied coals were likely influenced by multiple-stage infiltration of various solutions. These solutions leached the fresh pyroclastics and products of erosion derived from granites in the sediment-source regions, leading to redistribution of the critical elements (e.g., Zr, Nb, and HREY) between the roof, floor, and parting mudstones and the coal benches. The concentrations of (Nb,Ta) 2 O 5 , (Zr,Hf) 2 O 5 , and Ga in the coals are 107, 1093, and 57.6 ppm, respectively, close to or higher than the marginal grade of conventional ore deposits for these elements, and thus the Gaosheng coals have potential as raw materials for the recovery of the critical metals Nb, Ta, Zr, Hf, and Ga. [Display omitted] • The coal contains elevated concentrations of Nb, Ta, Zr, Hf, REE, Ga, Th, and U. • The sediment-source region of the coals was felsic-intermediate igneous rocks. • Elevated concentrations of critical elements in coal due to products of erosion and pyroclastics. • The coals are likely influenced by the multiple-stage infiltration of acid solutions. • The acid solutions leached the fresh pyroclastic and terrigenous materials. [ABSTRACT FROM AUTHOR]

In their thoughtful paper entitled "An equable subtropical climate throughout China in the Miocene based on palaeofloral evidence", Qing Wang, Yan Li, David K. Ferguson, Wen-Bo Mo, and Nan Yang (2021) imply that China exhibited negligible latitudinal mean annual precipitation (MAP) gradients and lacked arid regions during the Miocene. They also speculate that there was no abrupt change in elevation of the Tibetan Plateau, nor that the plateau attained its present altitude or orography during that period. These conclusions were derived mainly by using a co-existence approach (CA) and 'incomplete data'. Here, we use CA with training data and also integrate a coexistence likelihood estimation, a pollen-MAP boundary, a desert-MAP boundary, and other newly published MAP data to show that Northwest China consistently exhibited drier conditions than South China and East China during the entire Miocene, with our new values being 300–500 mm lower than those of Wang et al. (2021). This implies that there were large spatial gradients of MAP in China during the Miocene, which may be directly linked with the growth of the Tibetan Plateau, the global cooling, as well as other factors. We recommend the comprehensive consideration of multiple methods and proxies for reconstructing past climate conditions as opposed to a single proxy. [ABSTRACT FROM AUTHOR]

Abstract: In allusion to the problems of the frozen soil engineering geology, the roadbed stability with climate change in construction of the Qinghai–Tibet Railway (QTR), this paper provides overview of the frozen soil engineering problems before and during the QTR constructions. Based on the experiences and lessons learned from the road construction in permafrost areas, the authors recommended that the principle of “positive cooling” of the railroad roadbed by lowering permafrost temperatures should be used in the design of the QTR, rather than that of “passive protection” of permafrost through increasing thermal resistance of the roadway, such as simply increasing fill thickness and/or using thermal-insulation materials. This is especially important for the road sections in warm, ice-rich permafrost areas. In addition, this paper reviews several methods for “cooled roadbed” by controlling radiation, convection and conduction through modifying roadway structure and using different fill materials. Meanwhile, the authors also provide information on some existing problems and future monitoring programs along the QTR. [Copyright &y& Elsevier]

Abstract: This paper describes a multi-temporal grid method for quantifying changes in glacier coverage. A multi-temporal grid synthesizes spatial, attribute and process components of glacier information by sequentially combining spatial data from satellite images or maps. It enables us to identify glacier retreat and advance areas in individual grid cells for three or more periods of data sets. Discrepancies among the sequential data sets were detected graphically and numerically, including noise from geo-location error, misclassification, or different interpretation results in various pixel resolutions. Noise was detected and corrected to a large extent by visualization of the synthetic grid. The paper compares the results with that from a common method based on individual data sets, focusing on the Mt. Naimona’Nyi and Mt. Qomolangma regions at the northern slopes of the Himalayas. Results show that the identified noise (e.g. by 2.5km2 in the Mt. Naimona’Nyi region) is much larger than measurement uncertainty calculated by sensor resolution and co-registration error (e.g. by 0.015km2 in the Mt. Naimona’Nyi region). After noise removal, we notice that glacier recession clearly accelerates. The multi-temporal grid method results in a better quantification of glacier variation. It shows that glaciers in the Himalayas have both retreated and advanced during the last several decades, with retreat dominating and accelerating. Glaciers on the northern slope of Mt. Qomolangma in the middle Himalayas retreat more extensively and faster than those in the Mt. Naimona’Nyi region in the western Himalayas. [Copyright &y& Elsevier]

Abstract: As far as the railway embankment in permafrost regions is concerned, its mechanical properties are closely related to soil temperature. Especially for the embankment in the warm permafrost regions (mean annual ground temperatures range from 0–−1.5 °C), its stability will change greatly with minor temperature variations. The Qinghai–Tibet Railway (QTR) is approximately 1142 km long, of which 275 km are underlain by warm permafrost. Furthermore, the Qinghai–Tibet Plateau (QTP) is in an active seismic zone. Thus, the seismic stability, liquefaction, and deformation of the embankment of QTR are critical issues on safe operation. However, there are few papers concerning about the seismic response of railway embankment in permafrost regions. This paper will propose a thermal-dynamic coupled model, and the model and its specific analytical procedure can be described as follows. Firstly, based on the governing differential equations of transient temperature field with phase change, the temperature distributions of railway embankment are computed and analyzed by numerical method. Then, since the mechanical properties of frozen soil are effected by temperature, the dynamic consolidation equations of Biot, whose parameters are relative to temperature, are deduced in detail by adopting dynamic consolidation theory. Lastly, by using this numerical model, the seismic response of the QTR embankment is simulated, and the characteristics of seismic response, such as excess pore water pressure, stress and displacement, are analyzed in detail. Meanwhile, the seismic stability of this embankment is evaluated. The results show that this numerical model is able to simulate seismic response of embankment in permafrost regions. [Copyright &y& Elsevier]

Abstract: Rapid economic development has spurred land use change in China since the Chinese government initiated its economic reform in 1978. Although many papers have analyzed the characteristics of land use change, especially cropland conversion to non-agricultural use affected by economic development in the developed regions of China, relatively less attention has been paid to studying the characteristics of land use change affected by both economic development and environmental changes in its undeveloped regions. This paper analyzes the land use change and its driving forces in Dulan County, Qinghai Province on the Tibetan Plateau during 1990–2000. The land use change was studied based on the landscape metrics change and transition matrix of land use types, while its driving forces were analyzed according to climatic changes and socioeconomic development. The study indicates that the increase of land use benefits was given great attention; however, the protection of arid environment did not attracted much attention. The study suggests that the land use should be based on the sustainable protection of arid environment on the Tibetan Plateau. [Copyright &y& Elsevier]

The Wenchuan earthquake Fault Scientific Drilling project-hole 1 (WFSD-1) offers a unique opportunity for studying the faulting behavior and the thermal regime of the Longmen Shan fault zone (LMFZ), east margin of Tibetan Plateau. Thermal conductivity of fault rocks within main fault zone shows strong negative interrelations with the porosity, the gamma ray and the P-wave slowness, as well as a positive interrelation with the density. Here we attribute these correlations to the fractures and the rock-fluid reaction generated from the earthquake, which will increase the porosity, the radioactivity and the P-wave slowness as well as decrease the density and the thermal conductivity, synchronously. 15 continuous temperature profiles were summarized in this paper. Based on integrated studies of temperature variations and thermal gradients, local temperature anomalies were detected at three depth ranges of 480–510 m, 580–610 m and 625–755 m, respectively. These anomalies seem to correspond to different fracture zones and may be attributed to fluid flow in the fractures. In addition, the non-uniform vertical distribution of these temperature anomalies was observed across the co-seismic slip surface at 589.2 m. In the below ∼200 m borehole depth, a prominent thermal anomaly zone was developed, implying more factures were generated in the footwall than the hanging wall during the Wenchuan earthquake. The heat flow ranges from 69 mW/m 2 to 72 mW/m 2 for different logs. The persistence of elevated heat flow in the LMFZ appears to rule out frictional heating on the Yingxiu-Beichuan fault (YBF) as the source of the WFSD-1 value, but is probably related to the regional tectonic evolution. [ABSTRACT FROM AUTHOR]

Abstract: The Longmen-Shan fault zone, at the eastern margin of the Tibetan Plateau, is one of the most extensively studied areas in the world, yet the deformation model and earthquake-generating mechanism remain subjects of vigorous debate. This paper presents a new three-dimensional (3-D) velocity model determined using a large volume of seismic data and two-dimensional (2-D) magnetotelluric (MT) profiles from previous studies, to investigate the mechanisms of crustal deformation and earthquake generation along the reverse-thrust and strike-slip fault zone. It has been observed that low-velocity, and low-resistivity anomalies related to the Sichuan foreland basin, is in sharp contrast to high-velocity and high-resistivity anomalies in the Songpan-Ganze block in the upper crust. The tomographic model presented here reveals two crustal bodies with low-velocity and high-conductivity anomalies underneath the Longmen-Shan fault zone, separated into three contrasting segments by the two crustal bodies. The two low-velocity and low-resistivity bodies have been interpreted as being associated with extrusion of either fluids or products of partial melting from the lower crust and/or the upper mantle. This suggests strong variations in the rheological strength of the rock along the fault zone. This finding implies that coupling between these presumably fluid-bearing bodies and earthquake generation could be extremely complex and that there is dramatic variation from the southwestern area to the northeastern segment along the fault belt. It is suggested here that this complex and variable deformation system along the fault zone played a principal role in controlling seismic generation and rupturing during the 2008 Wenchuan earthquake (Ms 8.0) and that it will do so again during possible future earthquakes in the region. [Copyright &y& Elsevier]

Abstract: Radiocarbon dating of lake sediments is often hampered by the presence of a lake reservoir effect (LRE, also ‘dead carbon’ or ‘old carbon’ effect) especially in dry and cold regions with a sparse plant cover in the catchment. The Tibetan Plateau became a hotspot of the palaeoenvironmental and climate research community in recent years and the assessment of present-day LREs is a crucial prerequisite for the establishment of reliable radiocarbon age–depth relationships for lake sediment cores. This paper examines the spatial variability of LREs within individual lakes, through a discussion of new data for Lake Donggi Cona and a compilation of previously published data for five additional lakes where LRE data are available for different sites. Lake reservoir effects for Lake Donggi Cona on the northeastern Tibetan Plateau were determined for shells of aquatic snails collected alive close to the lake's shore. The largest determined LRE of 20,000 14C years is significantly larger than previously reported LREs from the central part of the lake, and larger than any previously published LRE for the Tibetan Plateau. Relatively low LREs in the central regions of lakes, higher LREs towards the margins, and high LREs in tributaries and spring waters are apparently a common pattern of Tibetan Plateau lakes. The differences in LREs within individual lakes or catchment areas are attributed to the more prolonged exchange of the lake water's dissolved inorganic carbon with the atmospheric CO2 in central lake regions on the one hand and the increasing influence of 14C free or poor stream and groundwater due to the dissolution of carbonaceous basement rocks towards its margins. Generally higher LREs were recorded in the three tectonically active lake regions of the six examined catchments, and it is speculated that rising crustal CO2 further contributes to the LREs in these catchments. In addition to these observations and inferences, elevated 14C levels of the atmosphere as a result of nuclear bomb testing are often ignored if LREs for modern materials are reported by convention relative to the atmospheric 14C activity of the year 1950. LRE data reported in this way represent unrealistic minimum estimates. [Copyright &y& Elsevier]

Summary: Alpine meadow soil is an important ecosystem component of the Qinghai-Tibetan Plateau. However, the alpine meadow soil is undergoing serious degradation mainly due to global climate change, overgrazing, human activities and rodents. In this paper, spatial sequencing was chosen over time succession sequencing to study the changes of soil hydraulic properties under different degrees of alpine meadow degradation. Soil saturated hydraulic conductivity (Ks) and Gardner α both at the surface and at 40–50cm depth were investigated in the field using tension infiltrometers. Soil physical and chemical properties, together with the root index at 0–10cm and 40–50cm soil layer depths were also analyzed. Pearson correlations were adopted to study the relationships among the investigated factors and principal component analysis was performed to identify the dominant factor. Results show that with increasing degree of degradation, soil sand content increased while soil Ks and Gardner α as well as soil clay content, soil porosity decreased in the 0–10cm soil layers, and organic matter and root gravimetric density decreased in both the 0–10cm and 40–50cm soil layers. However, soil moisture showed no significant changes with increasing degradation. With decreasing pressure head, soil unsaturated hydraulic conductivity reduced more slowly under degraded conditions than non-degraded conditions. Soil Ks and Gardner α were significantly correlated (P =0.01) with bulk density, soil porosity, soil organic matter and root gravimetric density. Among these, soil porosity is the dominant factor explaining about 90% of the variability in total infiltration flow. Under non-degraded conditions, the infiltration flow principally depended on the presence of macropores. With increasing degree of degradation, soil macropores quickly changed to mesopores or micropores. The proportion of total infiltration flow through macropores and mesopores significantly decreased with the most substantial decrease observed for the macropores in the 0–10cm soil layer. The substantial decrease of macropores caused a cut in soil moisture and hydraulic conductivity. This study improves the understanding and prediction of alpine meadow soil and ecosystem changes and provides guidelines for improving water flow modeling under the background of global climate change over the Qinghai-Tibetan Plateau and similar regions. [Copyright &y& Elsevier]

Abstract: Trade-off between the depth of an interface and the average velocity above the interface is well known in receiver function inversion. To resolve model ambiguity, surface wave dispersion data, which are sensitive to vertical shear velocity average, are commonly combined with P receiver functions in the inversion. In this paper, we design a joint inversion scheme using the neighborhood searching algorithm to solve shear velocity structure of the crust and uppermost mantle with receiver function and surface wave dispersion data. Two sets of stretched splines are implemented in the inversion to obtain smooth velocity profiles, separated by a specifically defined Moho discontinuity. We apply this method to the dense Hi-CLIMB seismic array in the central Tibetan Plateau (TP). The Indian crust is observed to subduct and underplate the Tibetan crust between the Yarlung-Zangbo suture and the Bangong-Nujiang suture, at the latitude of about 31.5°N. The crust thickens from about 50km below the Indian foreland to over 75km south of Bangong-Nujiang suture and turns shallower at around 65km under the Qiangtang block. We identify two zones with complicated Moho structure beneath the northern Lhasa block and southern Qiangtang block, indicating highly deformed Moho morphology, and beneath the Himalaya block associated with the underthrusting of the Indian Plate, respectively. A low velocity zone is present in the mid-crust in most parts of the profile under the TP with up to more than 10% velocity reduction. The low velocity structure is not continuous, forming discontinuous patches rather than channels, calling for a revision of the channel flow model. [Copyright &y& Elsevier]

Abstract: Based on the tree rings of Qilian juniper (Juniperus przewalskii), this paper presents a Palmer Drought Severity Index (PDSI) reconstruction (r = 0.578, p < 0.01) since AD 1411 for the northeastern Tibetan Plateau (TP). Regional extreme dry years (<2SD) were found in 1451, 1455, 1480, 1488, 1490, 1591, 1649, 1770, 1776, 1824, 1831, 1879, 1922, 1927 and 1992, while extreme wet years (≥2SD) were not observed. Persistent decadal dry intervals were observed in the 1450s, 1480s, 1510s, 1580s–90s, 1680s–1720s, 1820s–40s, 1920s–30s and after 1990s, and decadal wet intervals in the 1410s, 1500s, 1540s–50s, 1610s–70s, 1750s–60s, 1790s–1800s, 1880s–1910s, 1960s–80s. Regional droughts evident in the reconstruction appear to be relatively consistent with the drought history of the entire arid northeastern TP to the north indicated by previous studies. Spectral peaks of 2.1–5.9 years may be indicative of ENSO and IOD activity, as also suggested by negative correlations with SSTs in the eastern equatorial and southeastern Pacific Ocean and the northern Indian Ocean. Significant multi-decadal spectral peaks of 31.1–36.6 years and 41–53.8 years were identified and indicated that the decadal-scale variability may be linked to SST variations in the northern Pacific and Atlantic Oceans. [Copyright &y& Elsevier]

Abstract: The Yellow River (Huang He) downstream of the Jinshaan Canyon displays well-preserved fluvial terrace sequences below an extensive planation surface at the northeastern Ordos Plateau. Despite a series of well developed geomorphic surfaces, the landscape evolution of the plateau is largely unconstrained. The Jinshaan Canyon, formed by the deeply incising Yellow River through the Ordos Plateau, provides keys to understanding the landscape evolution of this Plateau with respect to the nearby northeastern margin of the Tibetan Plateau. This paper presents two sets of magnetostratigraphic results derived from the aeolian deposits (Red Clay and loess) on the planation surface and the uppermost Yellow River terrace in the middle part of the Jinshaan Canyon. Magnetostratigraphic analysis reveals that the planation surface and the uppermost Yellow River terrace formed respectively at circa 3.7Ma and circa 1.2Ma ago. The Ordos Plateau is the product of a period of planation culminating just before circa 3.7Ma and then was interrupted by an episode of uplift, which may be correlated with the accelerated growth of the Tibetan Plateau in the Miocene–Pliocene. The drainage system in the Jinshaan Canyon was re-organized around 3.7Ma. No correlation seems to exist between an older drainage existing prior to circa 3.7Ma and the present Yellow River network in the Jinshaan Canyon, even though sedimentary and tectonic evidence suggests that the drainage in the middle reach of the Yellow River formed in the late Miocene-early Pliocene. The Yellow River has developed its rectangular course around the Ordos Plateau only since circa 3.7Ma. [Copyright &y& Elsevier]

Abstract: The tectonic evolution of the Qiangtang Block in the Qinghai–Tibetan Plateau has been a controversial subject for a long time. In this paper, the discovery of new stratigraphic and fusuline fossil evidence from the Permian sequences (Qudi and Lugu formations) of the Qiangtang Block is reported and the palaeogeographical position and tectonic history of this block during the Late Cisuralian (Late Early Permian) are discussed. The Qudi Formation is typified by thick turbidite deposits and contains Artinskian fusulines such as Pseudofusulina and Chalaroschwagerina. The fusulines were deposited as grains involved in debris flow deposits, suggesting a synchronicity with the depositional time of the turbidites. The subsequent Lugu Formation is dominated by seamount-type carbonates with an irregular basalt base. Fusulines Cancellina, Pseudodoliolina and Parafusulina in the base of the carbonates confirm its age as middle Kungurian. The transition from the turbidite Qudi Formation to the seamount Lugu Formation is here interpreted to be a continuous depositional process recording the Qiangtang Block''s separation from the Indian Plate. This separation signaled the opening of the Neotethys Ocean between the Qiangtang Block and the Indian Plate. Palaeogeographically, the Qiangtang Block''s separation is comparable with the Baoshan Block''s separation in the east and Central Pamir''s separation in the west. By contrast, the ultimate opening of the Neotethys Ocean by the separation of India–Pakistan and northern Oman is apparently much later than this event recorded in the Qiangtang Block. Consequently, it is interpreted that the opening of the Neotethys Ocean in the whole northern Gondwanan margin is a diachronous series of events. [Copyright &y& Elsevier]

Abstract: Spatial non-stationarity and scale-dependence are important characteristics of the relationship between NDVI and climatic factors. To improve the reliability of model prediction, it is necessary to find the scales and spatial heterogeneity in which a stationary relationship is reached. In this paper, a geographically weighted regression (GWR) model was developed to define spatial non-stationarity and scale-dependent relationships between NDVI and climatic factors. The results indicate that the spatial scale of the stationary relationship for NDVI and both temperature and precipitation is 156km over the whole Qinghai-Tibet Plateau. Both modeling performance and the spatial pattern of the GWR model are significantly better than global regression models such as OLS. Significant spatial heterogeneity of regression relationships between NDVI and climatic factors is revealed within the Qinghai-Tibet Plateau. We conclude that the dominant climatic factor influencing NDVI is not the same for all ecoregions within the study area. There are also different key scales of interaction between NDVI and the dominant climatic factor in these various ecoregions. Finally, model performance is different in the each eco-region. Therefore, this finding can provide a scientific basis for choosing a suitable scale and reliable models to solve scale-dependent problems in geography and ecology. [Copyright &y& Elsevier]

Abstract: The Tibetan plateau contains thousands of small and big lakes. Changes in the water level of these lakes can be an important indicator for the water balance of the Tibetan plateau, but were until now extremely difficult to monitor: performing continuous in situ measurements at a large number of lakes is not feasible because of their remoteness, while radar altimetry is only capable of monitoring large lakes. Between 2003 and 2009 the Geoscience Laser Altimeter System (GLAS) on board of the Ice, Cloud and land Elevation Satellite (ICESat) obtained world-wide elevation profiles during 18 one-month campaigns. Using the GLAS data it is possible to obtain lake levels at decimeter accuracy. Available GLAS data over the Tibetan lakes is selected by means of the MODIS lake mask. As a result, lake level variations between 2003 and 2009 of 154 lakes of over a square kilometer size could be observed. For these lakes, an analysis of annual water level trends is made, and then their yearly gained or lost water volumes are estimated. In total, an area averaged increase in lake level of 0.20m/year over the Tibetan plateau is observed between 2003 and 2009. Most of the individual lakes considered in this paper have little or no levels apparently documented, and so the ICESat data provide the first baseline measurements of these lakes in the vertical. [Copyright &y& Elsevier]

Abstract: The Xianshuihe–Xiaojiang fault zone (XFZ) forms a prominent linear NW–SE trending tectonic feature along the southeastern margin of the Tibetan Plateau. The spatial and temporal evolution of the predominantly strike–slip movement along the fault remains unclear, as estimates for the initiation age of its different segments range from 5 to 13Ma. The Jinhe–Qinghe fault (JqF; the south part of the Longmen Shan thrust belt) provides a key for understanding the tectonic role and deformation history of the Xianshuihe–Xiaojiang fault zone in terms of timing, magnitude of displacement, and spatial–temporal evolution. This paper presents research on the structure and chronology of the JqF. The results of a geometric and kinematic study of the Jinhe–Qinghe fault show it to be a thrust fault with a left-lateral strike slip component; The strike slip offset extends at least 13–18km to southwest, based on the shortening of its folds and faulting, and based on stream deflection. Ten apatite fission track apparent ages show a pronounced change in age/elevation gradient at ~17±2Ma, consistent with an abrupt increase of exhumation due to uplift of the hanging wall of the JqF at that time. Combined with the age of deformed Tertiary strata in the footwall of the JqF and the geometric relationships of the JqF with the Chenghai fault and the XFZ, this indicates that the JqF was active between 17 and 5Ma. Based on the fault chronology, geometry, and movement, we suggest that the fault was a transpressional structure at the south end of the XFZ during the period from 17 to 5Ma. [Copyright &y& Elsevier]

Abstract: This paper describes and discusses the hydrochemical and isotopic characteristics of samples collected from some geothermal springs or wells in the Xining basin of the northeastern Tibetan Plateau, China. The results show that the groundwater runoff, circulation depth, recharge period, and residence times vary greatly, while dominating both the geothermal reservoir temperature and heat preservation in different tectonic units of the Xining Basin. Particularly, recharge by young cold surface water quickly and greatly reduces the temperature of geothermal systems. As for heat source, the general low temperature, immature waters as well as, helium isotope (3He/4He and 4He/20 Ne ratio) show that there seems to be no hot, mantle sourced fluids to increase the geothermal temperature. Crustal magmatic fluids, the radiogenic heat of radioactive elements, and the fault friction produced heat can all be possible contributing factors to the Xining basin heat sources. One can conclude that future investigation for geothermal resources should be closer to northern margin of Laji Moutain deep large fault zone where the high heat-flow can provide heat source while the mixing of surface water with groundwater is relatively slow. [Copyright &y& Elsevier]

Abstract: This paper presents detailed SHRIMP zircon U–Pb chronology, mineral chemistry, major and trace element, and Sr–Nd–Hf isotope geochemistry of two Cenozoic plutons (Karibasheng and Kuzigan) in western Tibetan Plateau, China. The Karibasheng pluton is composed of monzogranite, and the Kuzigan pluton consists of syenogranite, diopside-bearing syenite and diopside syenite. SHRIMP zircon U–Pb dating on monzogranite, syenogranite and diopside syenite shows that they were emplaced in Miocene (12–10Ma). These rocks are metaluminous and show the affinities with shoshonitic rocks, i.e., alkali-rich (K2O+Na2O=8.6–13.4wt.%), high K2O contents (4.7–10.6wt.%) with high K2O/Na2O ratios (1.2–4.6), enrichment in large ion lithophile elements (LILE) (e.g., Ba=2200–9100ppm; Sr=840–3100ppm, most >1100ppm) and rare earth elements (REE), especially light REE (LREE) (La/Yb up to 168). The rocks are depleted in high field strength elements (HFSE) but show high Nb/Ta ratios (13.3–30.7). The granites have lower initial 87Sr/86Sr ratios (0.7091–0.7099) and higher εNd (T) values (−7.1 to −9.5) than the syenites that have initial 87Sr/86Sr ratios of 0.7095–0.7117 and εNd (T) values of −8.6 to −12.2. Their zircon εHf (T) values (−7.2 to −9.7) are coupled with their whole-rock εNd (T) values, and plot along the mantle array. The amphibole–plagioclase thermometer and estimation of apatite saturation temperature indicate that the primary magmas had high temperatures (up to 880°C for the granites and up to 1100°C for the syenites). The source depth for the granites and syenites is <70–100km inferred by the metasomatic volatile phase (amphibole–phlogopite) relation, and thus most probably within the upper part of lithospheric mantle. Detailed elemental and isotopic data and major element modeling suggest that the granites and syenites were derived directly by partial melting of the veined lithospheric mantle that had been hybridized by the continental slab-derived melts. Continental slab break-off was most likely the mechanism associated with the generation of these granites and syenites. [Copyright &y& Elsevier]

Abstract: This paper presents three parallel datasets of total organic carbon (TOC) and total inorganic carbon (TIC) as well as carbonate content (CaCO3) of lake sediment from two lakes on the Tibetan Plateau in order to compare different methods and different machines. The results indicate that two carbon analyzers (a Shimadzu TOC-VCPH with solid sample module SSM-5000A and an Elementar Vario EL II) provide very similar TOC and TIC content despite slightly different performance procedures and temperature controls. A TOC record determined by a wet oxidation method and a carbon analyzer shows consistent down core variation although it seems that the wet oxidation method may overestimate TOC content due to the existence of some reduced compounds or minerals in the sediment. TIC content measured by a carbon analyzer and carbonate content determined by a chemical method exhibit similar fluctuation trends in both cores. This suggests that TIC content may be used as an environmental proxy roughly taking the place of carbonate content, especially in sediment with simple carbonate compositions. [Copyright &y& Elsevier]

Abstract: Although many studies of the 2008 Mw 7.9 Wenchuan earthquake have described the ground deformation features, rupture mechanism, and structural features of the seismogenic fault zone associated with this event, debate remains concerning the total length of the co-seismic surface rupture zone and whether the earthquake ruptured the Qingchuan Fault in the northeastern segment of the Longmen Shan Thrust Belt (LSTB), China. In this paper, we present new field evidence that the Qingchuan Fault was ruptured by the 2008 Wenchuan earthquake and that the total length of the co-seismic surface rupture zone is up to 285–300km. Field investigations reveal that the earthquake produced a ≥60-km-long surface rupture zone along the pre-existing Qingchuan Fault, with the offset being mainly right-lateral strike–slip and a distinct component of vertical slip. Co-seismic surface ruptures are characterized by faults and extensional cracks. Field measurements indicate co-seismic right-lateral strike–slip displacements along the Qingchuan Fault of 0.3–0.6m and vertical offsets of 0.2–0.5m, which differs to the displacements observed along the central and southwestern segments of the Wenchuan surface rupture zone in the displacement amount and sense. The change in slip sense from thrust-dominated slip in the central and southwestern segments of the LSTB to right-lateral strike–slip-dominated displacement along the Qingchuan Fault (northeastern segment of the LSTB) reflects a change in the orientation of compressive stress along the LSTB, associated with eastward extrusion of the Tibetan Plateau as it accommodates the ongoing penetration of the Indian Plate into the Eurasian Plate. [Copyright &y& Elsevier]

Abstract: Deciphering significant sedimentological processes from a set of sediment samples is an important step in reconstructing environmental changes. One approach going beyond classical methods is the unmixing of grain-size distributions. This paper presents a flexible end-member modelling algorithm that is based on eigenspace analysis and considers inherent uncertainties. It has been applied to the detrital grain-size components of lacustrine surface sediment samples of Lake Donggi Cona, Qinghai Province, China. It allows up to five grain-size end-members to be characterised and quantified in an optimal model. An end-member with a major mode in the clay domain accounts for 34% of variance within the grain-size data set. It may represent sedimentation of suspension load from linear and laminar runoff during heavy precipitation events in summer. Three end-members in the fine sand to medium silt domains make up 60% of lacustrine sedimentation. They may represent local to remote aeolian processes that peak in wintertime. A multimodal end-member explaining the remaining 6% of variance may represent further fluvial and littoral dynamics or random fluctuations and measurement errors. Several model runs of different scaling and numbers of end-members provided a suitable way to determine uncertainties inherent to the model. A comparison of 12 different model runs and their respective uncertainties yielded a distinct model of robust end-members. The clay and medium silt end-members are robust features of detrital sedimentation within Lake Donggi Cona. They alone explain 54.4% of total variance in the data. However, no spatial pattern or relation to water depth is found for any of the grain-size end-members. Thus, when past detrital sedimentation at Lake Donggi Cona is reconstructed, a special focus should be on the robust features attributed to aeolian and suspension-related sedimentation processes as well as on effective sediment mixing processes impeding a distinct correlation between grain size and spatial attributes. Further applications of the end-member modelling algorithm to other depositional environments are encouraged to demonstrate its universal applicability. [Copyright &y& Elsevier]

Abstract: In this paper, the 3D Finite Element Method was combined with a Discontinuous Deformation Analysis (DDA+FEM) to study the influence of the Wenchuan earthquake on the stability of the tectonic blocks system of the Qinghai–Tibet Plateau under the background of northward extrusion of the Indian Plate and obstruction of the strong crust of the Sichuan basin. With constraints from GPS data and focal mechanisms, we first calculated the velocity and stress fields of the region. Then, we numerically simulated the rupture process of the seismogenic fault of the 2008 Wenchuan earthquake in overthrust form with a right-lateral component. We then studied the movement and deformation of the tectonic blocks that was caused by the earthquake and its influence on the stress state of the boundary faults. The numerical simulation indicates that the large earthquake causes the most tectonic blocks in the study zone at approximately a 1-mm deviation toward the northeast; in particular, the Wenchuan seismogenic fault obviously deviated eastwards, and the maximum deviation reaches 1.5m. It seems that the large earthquake causes the Bayankala block at the west side of the Longmenshan fracture zone to extend farther eastward. The Wenchuan earthquake causes the Coulomb failure stresses on the boundary faults of the tectonic blocks in the study zone to change to different extents. The maximum change of the Coulomb failure stress reaches about 0.2MPa at both ends of the Wenchuan seismogenic fault, the south section of the Xianshuihe fracture zone and part of the southeast section of the Dongkunlun fracture zone in the upper crust. Additionally, the Coulomb failure stresses also increase to different extents between 0.01 and .02MPa in regions such as the southernmost end of the Xianshuihe fracture zone, part of the southeast section of the Dongkunlun fracture zone, and so on. [Copyright &y& Elsevier]

Abstract: The Miocene vegetation and climate history of western China remains unclear. However, widely-distributed Miocene sediments of the Tianshui Basin in the NE Tibetan Plateau provide a great potential for deciphering the Miocene vegetation and climate history of this region. This paper presents first sporopollen record from these sediments, covering the period from 17.1 to 6.1Ma. Sporopollen data reveal that temperate, warm-temperate broad-leaved forest of Quercus, Ulmus and Betula dominated the Tianshui region between 17.1 and 14.7Ma, which was replaced by forest or forest-steppe of Ulmus, Artemisia and Betula between 14.7 and 11.7Ma. After a return to a broad-leaved forest of Betula and Quercus during 11.7–8.5Ma, the forest decreased rapidly and was replaced mostly by steppe vegetation (mainly composed of Artemisia, Chenopodiaceae and Poaceae) after 8.5Ma. We interpret the observed vegetation changes as a result of global climate change, which is characterized by global cooling, development of Arctic ice-sheets and permanent El Niño state after the Middle Miocene Climatic Optimum. The rapid development of steppe at about 8.5Ma suggested a permanent drying of the Asian interior at this time, coinciding with the onset of the well-known Hipparion red clay deposition in North China. [Copyright &y& Elsevier]

Abstract: Since the pioneer wide-angle seismic profile along the Yadong–Gulu rift acquired in 1974 by the ex-Institute of Geophysics, Chinese Academy of Sciences (CAS), several research programs aimed to deep geophysics, performed thanks to the participation of Chinese national and international institutions, have been developed during last 35years, including 23 wide-angle seismic profiles with total length of about 6000km. These profiles are unevenly distributed, most of them in eastern Tibet and few profiles in western Tibet. In this paper, we make a summarized presentation of all these wide-angle seismic profiles and provide an overall view of the seismic velocity structure of the crust beneath the broad Tibetan plateau, which is the product of the continuous convergence and collision of the Indian and Eurasian plates since about 50Ma ago. Different patterns of crustal thickness variation related to the tectonic blocks and along suture zones of the region are displayed. The crust thickness is confirmed to be about 70–75km under southern Tibet, and 60–65km under northern, northeastern and southeastern Tibet. The leading edge of the subducted lithosphere reaches the northern margin of the plateau and directly contacts with Tarim Basin. Westward of the 90°E boundary, the Indian crust is moving towards the northern edge of the plateau and collides with Tarim Basin at 80°E while reach the Bangong–Nujiang suture belt at 88°E; eastward of the 90°E boundary, the northern edge of the crust should be at 50–100km south of Bangong–Nujiang suture. The results supply helpful constrains to understand the mechanism of the continent–continent collision and its consequences in the plateau and neighbouring areas. [Copyright &y& Elsevier]

Abstract: A N–S-trending active fault zone, which includes the Anninghe, Zemuhe, and Xiaojiang faults, forms the tectonic boundary of the Tibetan Plateau on its southeastern margin, marking the limit of the eastward extrusion of the Tibetan Plateau. In this paper, we document the Late Pleistocene–Holocene activity of the Zemuhe Fault, which is the central segment of the fault zone. We have been able to determine slip rate and the average recurrence interval of large earthquakes upon the fault, based on aerial photograph interpretations, field investigations, trench excavations, and radiocarbon age data. The Zemuhe Fault is mainly characterized by left-lateral offsets with a horizontal slip rate of ~10–12mm/yr, and a vertical slip component of ~2.0–2.4mm/yr. Trench investigations and 14 C ages reveal that at least four large earthquakes occurred during the last 1100–1500years, indicating an average recurrence interval of ~300–400years for M 7.0–7.5 earthquakes, consistent with the documented history of the region. Our results confirm that the Zehume Fault plays an important role as a tectonic boundary in releasing the strain energy caused by the southeastwards motion of the Tibetan Plateau. The energy is released in the form of repeated large earthquakes. [ABSTRACT FROM AUTHOR]

Abstract: The 1076-km-long Golmud–Lhasa oil product pipeline is located closely parallel to the highway constructed 20years earlier within the relatively narrow north–south engineering corridor crossing the treeless central area of the Qinghai–Tibet Plateau. Much of the corridor is at elevations exceeding 4500m and high-elevation, generally warm permafrost is encountered in more than one-half of the length. The pipeline, transporting mostly diesel, motor and aviation fuels at ambient temperatures, is 159mm in diameter, has a wall thickness of 6mm and was buried in a trench at a nominal depth of between 1.2 and 1.4m. The soils encountered, mostly periglacial sands, silts and gravels, often have elevated saline contents and are subject to severe wind erosion and occasional monsoon flash flooding conditions. During its first quarter century of operation, the pipeline suffered at least 30 significant leaks and four pipeline ruptures. About 337km of the pipeline was extensively rehabilitated, including relocations or replacements in major problem areas and, where feasible for an existing pipeline, improvements in pipeline protection during 2001–2004. It was supposed to safely operate for another 30years with proper checks and needed repairs. This paper provides a review on the history of the permafrost and cold regions environmental problems of the pipeline, and their major rehabilitation, repairs and problems in the future, which might have useful implications for similar oil product pipeline at high elevations or permafrost regions. [Copyright &y& Elsevier]

Abstract: There is a shortage of research concerning the relationships between land-use change, soil erosion, and soil organic carbon (SOC) and nitrogen (N) dynamics in alpine environments such as those found in the Tibetan plateau. In this paper, typical sloping farmlands converted from grassland 50 years ago in eastern Tibet were selected to determine dynamics of soil erosion, SOC, and total N associated with land-use change. Soil samples were collected from sloping farmland and control fields (grassland). The 137Cs, SOC, total N contents, and soil particle size fractions were analyzed in these samples. As compared with the control fields, 137Cs, SOC, and total N inventories in the sloping farmlands decreased by 30%, 27%, and 33%, respectively. Meanwhile variations in the three parameters were enhanced in the sloping farmlands, with coefficients of variation (CVs) of 38%, 23%, and 20%, respectively, for 37Cs, SOC, and total N. In addition, SOC and total N inventories significantly decreased with increasing soil erosion in the sloping farmland. In a sloping farmland with a steep 24° gradient, the 137Cs inventory gradually increased along a downslope transect with its lowest value at 0Bqm−2 in the top-slope position (0m). The soil clay (<0.002mm) content in such an area increased with decreasing elevation (r=−0.95, p=0.001). Significant correlations between 137Cs and clay (r=0.92, p=0.003), SOC (r=0.96, p=0.001), or total N (r=0.95, p=0.001) were also found in the farmland. These results showed that converting alpine grassland to sloping farmland accelerates soil erosion, losses in SOC and N, and increases the soil’s spatial variability. The combined impacts of tillage and water erosion contributed a significant decrease in the soil’s organic carbon and N storages. Particularly in steep sloping farmlands, tillage erosion contributed for severe soil loss, but the soil redistribution pattern was dominated by water erosion, not tillage erosion, due to the lack of boundaries across the field patches. It was also found that 137Cs, SOC, and total N moved along the same pathway within these sloping farmlands, resulting in net C and N losses during soil redistribution. The negative influences of land-use conversion from grassland to farmland in sloping areas in the Tibetan plateau should be addressed. [Copyright &y& Elsevier]

Abstract: A Mt. Geladaindong (GL) ice core was recovered from the central Tibetan Plateau (TP) spanning the period 1940–2005 AD. High-resolution major ion (Na+, K+, Ca2+, Mg2+, Cl−, SO4 2−, NO3 −) time-series are used to investigate variations in atmospheric dust loading through time. The crustal source ions vary seasonally with peaks in dust concentrations occurring during the winter and spring which are consistent with atmospheric dust observations at local meteorological stations. However, both similarities and dissimilarities are displayed between the decadal variation of atmospheric dust in the GL core and dust observation records from meteorological stations, which can be attributed to local environmental effects at the stations. This paper compares the 1980s and 1970s as case periods for low and high atmospheric dust loading, respectively, two periods reflecting shifts in spring atmospheric circulation (a weakening of zonal and meridional winds) from the 1970s (a period of enhanced dust aerosol transportation to central TP) to the 1980s (a period of diminished dust aerosol transportation to central TP), especially a significant decrease of meridional wind speeds in the 1980s. GL ice core dust proxies (Ca2+ and K+) are correlated with Total Ozone Mapping Spectrometer (TOMS) Aerosol Index (AI) data in spring over the TP and in the northwestern China (especially for K+). Thus variability of crustal ions in central TP ice core provides a proxy for reconstructing a history of atmospheric dust loading not only on the TP, but also in northwestern China. [Copyright &y& Elsevier]

Abstract: This paper aims to highlight the potential of using elemental and stable isotope analyses of aquatic macrophytes in palaeolimnological studies. Potamogeton pectinatus material was collected from modern plants (n =68) and from late glacial and Holocene-aged sediments from Koucha Lake (northeastern Tibetan Plateau; 34.0°N; 97.2°E; 4540m a.s.l.). It was analyzed for δ13C Potamogeton (modern: −23 to 0‰, fossil: −19 to −4‰) and δ15N Potamogeton (modern: −11.0 to +13.8‰, fossil: −9.5 to +6.7‰) in addition to elemental carbon and nitrogen (modern C/N Potamogeton : 7 to 29; fossil: 13 to 68) and sulfur (fossil: 188–899μmol/g dry weight). Fossil data were interpreted in terms of palaeo-nutrient availability and palaeo-productivity based on the modern relationships between various proxies and certain environmental data. Productivity of Potamogeton pectinatus mats at Koucha Lake as indicated by palaeo-ɛ Potamogeton -TIC (i.e. the enrichment of δ13C Potamogeton relative to the δ13CTIC) was reduced during periods of high conductivity, especially between 10.3 and 7.4cal kyr BP. Potamogeton pectinatus material from these periods was also characterized by high S Potamogeton indicating high sulfide concentrations and anoxic conditions within the sediments. However, C/N Potamogeton ratios and δ15N Potamogeton from the lower core section were found to have been altered by decompositional processes. A pronounced shift in the aquatic productivity of Lake Koucha occurred at ∼7.4cal kyr BP when the hydrological conditions shifted towards an open lake system and water depth increased. At this time a strong increase in productivity led to a strong decrease in the water HCO3 – concentration as inferred from the application of a ɛ Potamogeton -TIC-lnHCO3 − transfer function. A comparison of reconstructed productivity changes from Koucha Lake with further environmental proxies suggests that primary productivity changes are probably a function of internal lake dynamics and were only indirectly triggered by climate change. [Copyright &y& Elsevier]

Abstract: Based on dynamic triaxial test at low temperature of the frozen clay from the Beiluhe permafrost subgrade along the Qinghai–Tibet Railway (QTR), residual deformation laws and dynamic subsidence prediction model of permafrost subgrade under train traffic were studied. First, time history curves of residual strain of frozen soil are obtained and analyzed under different temperatures, frequency, confining pressure and moisture content. And conclusions can be drawn that the axial strain rate is greatly affected by the amplitude of dynamic stress, as well as increases with dynamic to static stress ratio and temperature rising, while it decreases with the raise of frequency and moisture content. Hereby, the power functions were adopted to fit the relationships of axial dynamic strain rate vs. stress ratio, temperature, frequency, and moisture content, respectively. Simultaneously, the permafrost dynamic subsidence mechanism was interpreted rationally and the variation of fitting parameters was discussed. Furthermore, the long-term traffic loading subsidence model was established through observing the axis residual strain time histories of frozen specimens under the longtime cyclic loading and adopting the amendment of vibratory number of times. The model can comprehensively consider the effects of stress state, temperature, moisture content, and confining pressure of frozen soil, as well as the vibratory frequency and vibration number of longtime cyclic loading. Consequently, the model can be applied to the train-induced subsidence forecast investigation of permafrost subgrade. The paper has an important significance for rational safety evaluation on long-term operation of permafrost regions railway such as QTR. Meanwhile, the investigation provides basic data for the further research on dynamic damage constitutive model of frozen soil under train traffic and the gradual improvement of railroading criterion in cold regions. [Copyright &y& Elsevier]

Abstract: It is generally believed that Cenozoic potassic and ultrapotassic volcanic rocks of the Tibetan Plateau were generated by partial melting of enriched mantle. This paper reports new data regarding the elemental and isotopic compositions of the KonglongXiang volcanic rocks (KVR; K2O/Na2O>2 and low MgO contents) in the middle–western Lhasa terrane, Tibetan Plateau. Ar–Ar isotope dating of a sample from the KVR yields an age of 21.3Ma, indicating that the KVR lavas erupted during the Early Miocene. The KVR consists mainly of trachyte and rhyolite. A comparison of the KVR with Cenozoic potassic volcanic rocks of the Tibetan Plateau and the results of melting experiments involving K-rich volcanic rocks, as well as other K-rich volcanic rocks from throughout the world, reveals that the KVR trachytes originated from a mafic lower crust containing K-rich minerals rather than from a mantle source. The KVR rhyolites were probably derived from the middle–upper crust. Based on age data, compositional data, and the regional tectonic setting, we propose that the formation of the KVR and associated N–S grabens was triggered by Early Miocene E–W regional extension in the area of the southern Tibetan Plateau. [Copyright &y& Elsevier]

Abstract: Water level and chemistry of Lake Qinghai are sensitive to climate changes and are important for paleoclimatic implications. An accurate understanding of hydrological and chemical budgets is crucial for quantifying geochemical proxies and carbon cycle. Published results of water budget are firstly reviewed in this paper. Chemical budget and residence time of major dissolved constituents in the lake are estimated using reliable water budget and newly obtained data for seasonal water chemistry. The results indicate that carbonate weathering is the most important riverine process, resulting in dominance of Ca2+ and DIC for river waters and groundwater. Groundwater contribution to major dissolved constituents is relatively small (4.2 ± 0.5%). Wet atmospheric deposition contributes annually 7.4–44.0% soluble flux to the lake, resulting from eolian dust throughout the seasons. Estimates of chemical budget further suggest that (1) the Buha-type water dominates the chemical components of the lake water, (2) Na+, Cl−, Mg2+, and K+ in lake water are enriched owing to their conservative behaviors, and (3) precipitation of authigenic carbonates (low-Mg calcite, aragonite, and dolomite) transits quickly dissolved Ca2+ into the bottom sediments of the lake, resulting in very low Ca2+ in the lake water. Therefore, authigenic carbonates in the sediments hold potential information on the relative contribution of different solute inputs to the lake and the lake chemistry in the past. [Copyright &y& Elsevier]

Abstract: This paper discusses the range of lake level changes, using hydro-acoustic techniques and sediment core data for Lake Nam Co in Central Tibet (China). This second largest Tibetan lake is situated at an elevation of 4718 m a.s.l. Lake level changes with different high stands documented by beach remnants are widespread on the Tibetan Plateau and also in Lake Nam Co. They indicate significant changes in the hydrological system triggered by the monsoonal circulation. Using hydro-acoustic techniques submerged beach remains at approximately 10/15 m, 30 m, 45 m, 70 m and 95 m below present day lake level were detected, indicating a more negative water balance than today. The −10/−15 m lake level is dated to an age equal to the Little Ice Age. All deeper lake levels are assumed to have been formed prior to ∼10000 cal BP. Folded older sediments, detected in the hydro-acoustic profiles indicate a possible larger extent of the glaciers during or prior to the Last Glacial Maximum (LGM). This is followed by a low stand or even by possible desiccation of the entire lake basin during or after the LGM. [Copyright &y& Elsevier]

Abstract: The downward solar or shortwave radiation (SWD) and atmospheric longwave radiation (LWD) play essential roles in controlling alpine environment and ecosystem. Meanwhile, utilization of solar energy has a growing demand by local residents, due to high energy cost in high altitude regions. However, it is always costly for acquiring the radiation data and there are few studies on the radiation modeling in these regions. This paper presented the major characteristics of SWD and LWD over the Tibetan Plateau (TP), which were measured at 11 stations built in the region. The results showed that LWD received by TP is much lower than that of its surrounding areas and their monthly-mean differences can be up to 100Wm−2. On the contrary, SWD over TP is significantly higher than that over its surrounding areas, due to low extinction rate of airmass, water vapor, and aerosol occurred in TP. The recorded maximum value (∼0.9) of daily-mean transmittances much exceeds the upper bound (∼0.75) implied in most of the Angström–Prescott models; therefore, these models may under-estimate SWD over TP. One set of surface data-based estimate by a non-Angström–Prescott model and two sets of satellite estimates were also evaluated against the measurements. It is found that the surface data-based estimate, though not calibrated locally, shows a good agreement with the measurements and has an advantage of producing less root-mean-square errors and higher correlation coefficients than the satellite estimates. Under this condition, it is suggested to combine both the surface data-based estimate together with the satellite estimates in order to improve the accuracy of the SWD and LWD data. [Copyright &y& Elsevier]

Abstract: Analyses of characteristics of vibration response of track structure from train traffic and its attenuation laws, based on the field monitoring of the vibration acceleration response of rail, sleeper, and embankment at the Beiluhe permafrost testing section along the Qinghai–Tibet railway in China, are performed in this paper. The reasonable fitting formula of attenuation relationship of embankment vibration is put forward in a negative exponential function form. The quantitative understanding of the vibration property is obtained according to the statistic of the two well-defined eigenvalues of vibration acceleration response, as well as the analysis of the acceleration time histories and the corresponding frequency spectra. The results suggest that: the effect of rail gap on the maximal vertical vibration response of rail is not evident; vibration response of sleeper near the rail gap is obviously larger than that of other sleepers, especially having intensive shock pulse, and the maximum is more than three times that of the vibration response of the sleeper lying in the very middle of the two rail gaps from one compartment passing by; the rail vibration energy concentrates within 10Hz, and the rail predominant frequencies mainly correlate with train speed and bogie spacing; the dominant frequencies of the embankment vibration, varying from 40 to 70Hz for the embankment shoulder and reducing with the distance increasing from the track, are influenced chiefly by train speed and sleeper spacing. The results mentioned above have important significance for rational cognition of vibration response characteristics of track structure at permafrost site, and moreover for the dynamic stability evaluation for the long-term operation of the Qinghai–Tibet railway. Meanwhile, the investigation provides basic data for the further research on the rail transit dynamics and the improvement of railroading criterion in cold regions. [Copyright &y& Elsevier]

Abstract: The Tibetan Plateau covers an area of about one fourth of Europe, has an average elevation over 4000m above sea level, and is the water sources for about 40% of world''s population. In order to foresee future changes in water quality, it is important to understand what pressures are governing the spatial variation in water chemistry. In this paper the chemistry including major ions and trace elements in the headwaters of four major Asian rivers (i.e. the Salween, Mekong, Yangtze River and Yarlung Tsangpo) in the Tibetan Plateau was studied. The results showed that the content of dissolved salts in these Tibetan rivers was relatively high compared to waters from other parts of the world. The chemical composition of the four rivers were rather similar, with Ca2+ and HCO3 − being the dominating ions. The exception was the Yangtze River on the Plateau, which was enriched in Na+, Cl−, SO4 2− and Li due to silicate weathering followed by strong evaporation caused by a negative water balance, dissolution of evaporites in the catchment and some drainage from saline lakes. The concentrations of heavy metals (Cu, Co, Cr, Ni, Cd, Pb, and Hg) and As, NH4 + were generally low in all the rivers. Anthropogenic impacts on the quality of the rivers were identified at a few locations in the Mekong River and Yarlung Tsangpo basins. Generally, the main spatial variation in chemical compositions of these under studied rivers was found to be governed mainly by difference in geological variation and regional climatic-environment. Climate change is, therefore, one of main determining factors on the water chemical characteristics of these headwaters of Asian major rivers in the Tibetan Plateau. [Copyright &y& Elsevier]

Abstract: In this paper we present sedimentologic, petrographic, and paleoecologic data from a ~810-m-thick section of late Neogene (ca. 9–7 to 1Ma) fluvio-lacustrine deposits in the high-elevation Zhada Basin of SW-Tibet. The tectonic evolution of the Zhada Basin region, located between the Himalayan Mountains in the S and the Transhimalayan Mountains in the N, is poorly understood, but sediment accumulation was probably initiated in response to the middle/late Miocene uplift of the Gurla Mandhata and Leo Pargil domes in the E and W, respectively. The sedimentary record can be subdivided into five stratigraphic units with distinctly different lithofacies associations (LA); these are, from bottom to top: a bedload-dominated fluvial LA (Unit 1, 0–90m); a nearshore lacustrine, deltaic LA (Unit 2, 90–220m); an offshore lacustrine LA (Unit 3, 220–500m); a nearshore lacustrine, fan-delta LA (Unit 4, 500–600m); and a fan-delta/alluvial fan LA (Unit 5, 600–810m). Clast and heavy mineral compositions revealed sediment supply from two different provenance areas, one from the south and one from the north/east, based on catchment geology of the Himalaya and Transhimalaya. Ostracode faunal assemblages are largely comparable to those of modern Tibetan lakes and allow the reconstruction of paleo-lake environments, including lake-level changes and salinity. The sedimentary pattern shows strong cyclicity at various scales (m, 10s m, and >100m). Small-scale cycles are interpreted as intrinsically-controlled depositional processes of deltas (lobe switching), whereas medium- and large-scale cycles are most likely forced by climate fluctuations. The overall evolution of the sedimentologic record includes: a strong and rapid increase in fluvial discharge in the uppermost portion of Unit 1, a transition from fluvial to lacustrine deposition during deposition of Unit 2, rhythmic variations in the style of lacustrine sedimentation during deposition of Unit 3, an increase in the supply of coarse clastics starting with deposition of Unit 4, and a transition from lacustrine to alluvial sedimentation during deposition of Unit 5. We speculate that the increase in discharge and, presumably, precipitation leading to the establishment of lacustrine conditions in the lower part of the section (Unit 2) is largely due to regional summer monsoon intensification during the late Miocene, and that the transition from lacustrine to alluvial sedimentation in the uppper part of the section reflects the onset of Northern Hemisphere glaciation and winter monsoon strengthening at ~2.6Ma. [Copyright &y& Elsevier]

Abstract: Rising as “the roof of the world” the Tibetan plateau is now underlain with the thickest continental crust on Earth. How and when was this crust formed, which would have exerted pivotal controls to the formation of the plateau, has long been an issue of hot debates. This paper reports zircon U–Pb ages and Hf isotope data for postcollisional (~30–9Ma) adakites in the southern Lhasa terrane, southern Tibet. A comparative analysis of whole-rock rare earth element geochemistry and zircon Hf isotopes between the adakites and associated Gangdese igneous rocks suggests that the Tibetan crust underwent a major phase of tectonic thickening between ca. 45 and 30Ma in the region. The lower part of the thickened crust consisted prevailingly of mafic lithologies, which we argue to have resulted from intense basaltic underplating and subsequent remelting that took place during the Late Cretaceous and Eocene time related to the Neotethyan subduction processes including breakoff of the subducted slab at ca. 50Ma in the early stage of the India–Asia collision. These processes were responsible for not only the juvenile crust formation but also for the creation of a thermally softened lithosphere in the southern Lhasa terrane. The indentation of India, consequently, caused distributed lithospheric thickening with formation of an orogenic root beneath southern Tibet. Root foundering during the Oligocene gave rise to the adakitic magmatism, regional topographic uplift, and onset of northward underthrusting of the Indian plate that has since played a key role in forming the entire Tibetan plateau. [Copyright &y& Elsevier]