Temporal and Spatial Variation Characteristics of Snow Cover Area in the Pamirs from 2010 to 2020

Scientific and comprehensive monitoring of snow cover changes in the Pamirs is of great significance to the prevention of snow disasters around the Pamirs and the full utilization of water resources. Utilize the 2010-2020 snow cover product MOD10A2, Synthesis by maximum, The temporal and spatial variation characteristics of snow cover area in the Pamirs in the past 11 years have been obtained. Research indicates: In terms of interannual changes, the snow cover area of the Pamir Plateau from 2010 to 2020 generally showed a slight decrease trend. The average snow cover area in 2012 was the largest, reaching 54.167% of the total area. In 2014, the average snow cover area was the smallest, accounting for only 44.863% of the total area. In terms of annual changes, there are obvious changes with the change of seasons. The largest snow area is in March, and the smallest snow area is in August. In the past 11 years, the average snow cover area in spring and summer showed a slow decreasing trend, and there was almost no change in autumn and winter. In terms of space, the snow cover area of the Pamirs is significantly affected by altitude, and the high snow cover areas are mainly distributed in the Karakoram Mountains and other areas with an altitude greater than 5000 meters.

A Preliminary Study on the Soft–Sediment Deformation Structures in the Late Quaternary Lacustrine Sediments at Tashkorgan, Northeastern Pamir, China

This study identified soft-sediment deformation structures （SSDS） of seismic origin from lacustrine sediments in the late Quaternary paleo-dammed lake at Tashkorgan, northeastern Pamir. The observed deformation structures include sand dykes, liquefied diapir and convolute structures, gravity induced SSDS, and thixotropic pillar and tabular structures. We conducted a preliminary study on the morphology, formation and trigger mechanisms of pillar and tabular structures formed by liquefaction of underlying coarse sand and thixotropy of the upper silty clay. The regional tectonic setting and distribution of lacustrine strata indicate that the most probable trigger for the SSDS in lacustrine sediments was seismic activity, with an approximate earthquake magnitude of M〉6.0; the potential seismogenic fault is the southern part of the Kongur normal fault extensional system. AMS ^4C dating results indicate that the SSDS were formed by seismic events occurring between 26050±100 yrBP and 22710±80 yrBP, implying intense fault activity in this region during the late Pleistocene. This study provides new evidence for understanding tectonic activity and regional geodynamics in western China.

Glacier changes since the early 1960s, eastern Pamir, China

Glaciers in the eastern Pamir are important for water resources and the social and economic development of the region.In the last 50 years,these glaciers have shrunk and lost ice mass due to climate change.In order to understand recent glacier dynamics in the region,a new inventory was compiled from Landsat TM/ETM+ images acquired in2009,free of clouds and with minimal snow cover on the glacierized mountains.The first glacier inventory of the area was also updated by digitizing glacier outlines from topographical maps that had been modified and verified using aerial photographs.Total glacier area decreased by 10.8%±1.1%,mainly attributed to an increase in air temperature,although precipitation,glacier size and topographic features also combined to affect the general shrinkage of the glaciers.The 19.3–21.4 km^3 estimated glacier mass loss has contributed to an increase in river runoff and water resources.

Late Cenozoic Deformation Sequence of a Thrust System along the Eastern Margin of Pamir,Northwest China

A thrust belt formed in the basin along the eastern margin of Pamir.The thrust belt is about 50 km wide,extends about 200 km,and includes three compressive structures from south to north：the blind Qipan structural wedge and Qimugen structural wedge,and the exposed Yengisar anticline.The thrust belt displays a right-stepping en echelon pattern.The Qipan structural wedge dies out northward to the west of the Qimugen structural wedge,and the Qimugen structural wedge dies out northward to the west of the Yengisar anticline.Detailed analysis of seismic reflection profiles of the western Tarim Basin reveal that fan-shaped growth strata were deposited in the shallow part of the thrust belt,recording the deformation sequence of the thrust belt.The depth of the Cenozoic growth strata decreases from south to north.The growth strata of the Qipan structural wedge is located in the middle-lower section of the Pliocene Artux Formation（N2a）,the growth strata of the Qimugen structural wedge is close to the bottom of the Pleistocene Xiyu Formation（Q1x）,and the growth strata of the Yengisar anticline is located in the middle section of the Xiyu Formation（Q1x）.Combined with magnetostratigraphic studies in the western Tarim basin,it can be preliminarily inferred that the deformation sequence of the thrust belt along the eastern margin of Pamir is progressively younger northward.The geometry and kinematic evolution of the thrust belt in the eastern margin of Pamir can be compared with previous analogue modeling experiments of transpressional deformation,suggesting that the thrust belt was formed in a transpressional tectonic setting.

The 2008 Nura Mw6.7 earthquake: A shallow rupture on the Main Pamir Thrust revealed by GPS and In SAR

The 2008 Nura Mw6.7 earthquake occurred in front of the Trans-Alai Range, central Asia. We present Interferometric Synthetic Aperture Radar （InSAR） measurements of its coseismic ground deformation that are available for a major earthquake in the region. Analysis of the InSAR data shows that the earthquake ruptured a secondary fault of the Main Pamir Thrust for about 20 kin. The fault plane striking N46~E and dipping 48~SE is dominated by thrust slip up to 3 m, most of which is confined to the uppermost 2-5 km of the crust, similar to the nearby 1974 MwT.0 Markansu earthquake. The elastic model of interseismic deformation constrained by GPS measurements suggests that the two earthquakes may have resulted from the failures of two high-angle reverse faults that are about 10 km apart and rooted in a locked dScollement at depths of 5-6 kin. The elastic strain is built up by a freely creeping decollement at about 16 mm/a.

Mesozoic–Cenozoic Tectonic Evolution and Uplift in Pamir:Application of Fission Track Thermochronology

The Pamir Plateau can be divided into three secondary tectonic units from north to south:the North,the Middle and the South Pamir Blocks.The North Pamir Block belonged to the southern margin of Tarim-Karakum,thermochronological study of the Pamir structural intersection indicates that accretion of the Middle Pamir Block to the Eurasian Continental Margin and its subduction and collision with the North Pamir Block occurred in the Middle–Late Jurassic.Due to the Neo-Tethys closure in the Early Cretaceous,the South Pamir Block began to collide with the accretion(the Middle Pamir Block)of the Eurasian Continental Margin.Affected by the collision and continuous convergence between the Indian Plate and the Eurasian Plate since the Cenozoic,Pamir is in a multi-stage differential uplift process.During 56.1–48.5 Ma,North Pamir took the lead in uplifting,that is,the first rapid uplift in the Pamir region began there.The continuous compression and contraction of the Indian and Eurasian plates during 22.0–15.1 Ma forced the Pamir tectonic syntaxis to begin its overall uplift,i.e.Pamir began to enter the second rapid uplift stage in the Early Oligocene,which lasted until the Middle Miocene.During 14.6–8.5Ma,South Pamir was in a rapid uplift stage,while North Pamir was in a relatively stable state,showing asymmetry of tectonic deformation in the Pamir region in space.Since 6.5 Ma,Pamir began to rapidly uplift again.

Origin of Early Creceouscalc-alkaline granite, Taxkorgan: Implications for evolution of Tethys evolution in central Pamir

The Pamir plateau may have been a westward continuation of Tibet plateau.Meanwhile,the Rushan-Pshart suture is correlative to the Bangong-Nujiang suture of Tibet,and the Central Pamir is the lateral equivalent of the Qiangtang Block.We present the first detailed LA-ICPMS zircon U-Pb chronology,major and trace element,and Lu-Hf isotope geochemistry of Taxkorgan two-mica monzogranite to illuminate the Tethys evolution in central Pamir.LA-ICPMS zircon U-Pb dating shows that two-mica monzogranite is emplaced in the Cretaceous(118 Ma).Its geochemical features are similar to S-type granite,with enrichment in LREEs and negative Ba,Sr,Zr and Ti anomalies.All the samples show negative zirconεHf(t)values ranging from 17.0 to 12.5(mean 14.5),corresponding to crustal Hf model(TDM2)ages of 1906 to 2169 Ma.It is inferred that these granitoids are derived from partial melting of peliticmetasedimentary rocks analogous to the Paleoproterozoic Bulunkuole Group,predominantly with muscovite schists component.Based on the petrological and geochemical data presented above,together with the regional geology,this work provides new insights that Bangong Nujiang Ocean closed in Early Cretaceous(120114 Ma).

Intermediate-depth earthquakes beneath the Pamir-Hindu Kush Region:Evidence for collision between two opposite subduction zones

We employed a double-difference algorithm （hypoDD） to relocate earthquakes within the region bounded by 66°E-78°E and 32°N-42°N in the period of 1964-2003 reported by the International Seismological Center （ISC）. The improved hypocentral locations delineate a double-layered Wadati-Benioff zone in the eastern Hindu Kush intermediate seismic belt. Based on this feature and other evidences, we propose that the intermediate-depth earthquakes beneath the Pamir-Hindu Kush region may occur in two collided subduction zones with opposite dip directions.

A study on physical property of crustal material and seismogenic environment in northeastern Pamir

2-D crustal structure and velocity ratio are obtained by processing S-wave data from two wide-angle reflec-tion/refraction profiles in and around Jiashi in northeastern Pamir, with the result of P-wave data taken into con-sideration. The result shows that: 1) Average crustal velocity ratio is obviously higher in Tarim block than in West Kunlun Mts. and Tianshan fold zone, which reflects its crustal physical property of 'hardness' and stability. The relatively low but normai velocity ratio (Poisson's ratio) of the lower crust indicates that the 'downward thrusting' of Tarim basin is the main feature of crustal movement in this area. 2) The rock layer in the upper crust of Tianshan fold zone is relatively 'soft', which makes it prone to rupture and stress energy release. This is the primary tectonic factor for the concentration of small earthquakes in this area. 3) Jiashi is located right over the apex or the inflection point of the updoming lower crustal interface C and the crust-mantle boundary, which is the deep struc-tural background for the occurrence of strong earthquakes. The alternate variation of vp/vs near the block bounda-ries and the complicated configuration of the interfaces in the upper and middie part of the upper crust form a par-ticular structural environment for the Jiashi strong earthquake swarm. vp/vs is comparatively high and shear modulus is low at the focal region, which may be the main reason for the low stress drop of the Jiashi strong earthquake swarm.

THE CENTRAL PAMIR—AN ALPINE COLLISION ZONE

The Alpine zone of Central Pamir is elongated in sublatitudinal direction between the Hercynians of Northern Pamir and the Cimmerians of Southern Pamir south of the Vanch\|Akbaital thrust. Its western continuation is overthrusted by the Herat fault and its eastern continuation is cut by the Karakoram strike\|slip fault.. The Central Pamir is a mainly S\|vergent (at the southern part N\|vergent) Alpine nappe stack then folding in antiform. It comprises deposits from Vendian to Neogene which have a thickness of 10km. Paleozoic and Mesozoic tectonic activity was poorly displaied in its limits. Rifting took place in Early and probably Upper Paleozoic. Pre\|Upper Cretaceous unconformity is known only in southern (autochthonous) part of the Zone as a result of closing of Bangong\|Nu Jiang ocean. In northern (allochthonous) part of the zone the sequence of Mesozoic and Paleogene rocks has no unconformities. Alpine endogenous processes were developed very intensively. They implied nappes and imbricate structures, linear folding, different igneous activity, zonal metamorphism. Slices of pyroxenites and gabbroids occured. Calc\|alkaline lavas and tuffs constitutes the major part of Paleocene to Miocene sequence (andesites\|ryolites\|in Paleogene, alkaline basalts in Oligocene—Miocene). Oligocene—Miocene zonal metamorphic belt of the intermediate type of high pressure including series of granitegneiss domes can be traced along the Central Pamir. Cores of domes include migmatites and remobilized bodies of the Early Paleozoic gneissic granites. The decompression took place at a later stage and rocks were overprinted by the andalusite\|sillimanite type metamorphism.. Syenite and leucogranite bodies, pegmatite and aplite veins were emplaced.

TECTONIC TRANSFER ON THE EASTERN EDGE OF PAMIR

Deformation during the uplift of Pamir Since the Himalayan movement, the Punjab block of Indian plate has intruded into the interior of Eurasian plate, produced a protrusive Pamir knot in eastern Tethys. The Pamir knot is where crustal shortening is most intensive in Tethys. After India\|Eurasia collision, giant relief resulted from fast uplifting of Karakorum due to the convergence and underplating in northern and southern margins of Karakorum, the uplifting rates changed with times, and thrusting would be one of the most important factors controlling the uplifting. At the same time, large scale strike\|slip faulting could produced large vertical offsets, so that the exhumation of the rocks from middle and lower crust has drawn much attention. The post\|collisional deformation and evolution of Karakorum would involve the processes of continental escape, crustal shortening and thickening, and orogenic collapse in extensional regime. The thrusting started in late Jurassic and early Cretaceous, but two peaks occurred in late Cretaceous and Eocene, respectively. A large amount of klippen produced by thrusting from north to south have been discovered in the northern slope of the Kungai in front of Pamir. Molnar and Tapponnier noted that the mount of crustal shortening in Pamir would be up to 2000km in the past 40～45Ma, and Coward proposed that 300～400km shortening has happened only in southern Pamir to northern Pakistan. In western Pamir from Kabul of Afghanistan to Quatta of Pakistan, the Chaman left\|lateral strike\|slip fault system extends 1000km long. Multiple structural superposition in eastern Pamir, due to the effects of the uplifting of Qinghai\|Tibet plateau, resulted in complex deformation patterns.

THE NORTHWARD PROPAGATION OF THE ARC TECTONICS OF THE NORTHEAST PAMIR AND NORTHWEST TARIM BASIN

The geological, geographic and seismicity data indicate that three arc tectonic belt developed on the northeast Pamir, which was the south Pamir arc, the north Pamir arc and the external Pamir arc from south to north. In addition to these three belts, there are two nascent arc tectonic belts developed in its fore\|deep depression, the Kashi depression in the northwest Tarim basin, which is the northward propagation of the arc tectonics of northeast Pamir.The south Pamir is an ancient folded belt, composed of the Proterozoic metamorphic layers and igneous complex. It was pushed northward since the collision between the India and Asia, and uplifted since the end of the early Tertiary. The elevation of the Plateau is 4800～5300m, and several intermontane basins distributed in the plateau. At its northeast boundary is the Kalakorum right lateral strike slip fault. Strong strike slip earthquakes occurred along this fault. In the hinterland of the plateau, several normal faulting earthquakes occurred,which are consistent with the extensional dynamic environment of the south Pamir. Deep earthquakes occurred under the 70km depth crust of south Pamir. The N—S cross section of the focal depth show that the earthquake occurred within the south Pamir crust are lower than 70km, and the deep earthquakes with depth of 100～200km occurred in the crystal basement of Tarim basin which are under\|thrusting southward into the root of the south Pamir.

Geohazards in Pamir Mountains,Tajikistan

We want to talk about the geohazards in Pamir mountains,in Tajikistan,using different materials and researches about it.Also we are trying to look deeply into this problem,and want to research how about

GEODYNAMICS OF THE PAMIRS—HIMALAYA REGION

The Pamirs—Himalaya region possessing a complex tectonic structure and high seismic activity is located at the central part of the Alpine—Himalayan fold belt. During long\|term geodynamical studies we revealed new features of its modern structural plan steadily traced at different deep levels. The reconstruction of paleostresses by analyzing fracture patterns of Mesozoic—Cenozoic sedimentary rocks has been carried out in order to establish geodynamic regularities of the region under study and to propose a model of its development. Unlike traditional approaches to the problem of paleostress reconstruction from orientation of systems of rock joints, approaches which are based usually on the local strength criteria, we consider the formation of joint sets as a rheological instability manifesting in localized form. The systems of layers of localized plastic deformation are formed during lithification of sedimentary rocks and evolve with time into joint sets. The corresponding method of reconstruction of paleostress axes was developed. It was tested for some tectonically active regions: Central Asia, the Caucasus, the Crimea, Cuba, Iran, and others. The method was found to be useful for reconstruction of both history and spatial distribution of paleostress axes in active crustal blocks and near large geological structures. In the Pamirs—Himalaya region the fracturing of rocks has been investigated in about 1000 outcrops. By analyzing the Mesozoic—Cenozoic paleostress history it was confirmed that the structural features of the region (including an arc\|like shape of the Pamirs—Tian Shan junction zone) are caused by movement of the Hindustan mobile plate towards the rather stable Eurasian plate during the Alpine cycle of development.

Study on basement structures of the northeast Pamirs

Basement structures and basement interfaces are obtained by finite-difference and time-term methods using Pg-wave data from two deep seismic sounding (DSS) profiles in the Artush-Jiashi strong earthquake area. The geological units differ considerably in basement depth. The basement structures of contact zones between two geological units also vary obviously, which marks the existence of boundary faults. Finally, we make a remark upon the relationship between characteristics of basement structures and seismicity in the Artush meizoseismal area and the Jiashi earthquake swarm area.

Pn wave velocity and anisotropy beneath Pamir and its adjacent regions

As the western end point of continental collision between the Indian and Eurasian plates, Pamir is an ideal place to research uplifting mechanisms in the Tibetan plateau. In this study, 141 644 Pn arrivals were used to obtain seismic wave velocities and anisotropy in the uppermost mantle beneath Pamir and its adjacent regions by performing tomographic inversion of Pn travel times. The data were selected from multiple databases, including ISC/EHB, the Annual Bulletin of Chinese Earthquakes, and regional bulletins of Xinjiang. The tomography results reveal significant features with high resolution and correlate well with geological structures. The main results are as follows： （1） The Pn wave velocities are particularly high in the old stable blocks such as Tarim basin, Indian plate and Tajik basin, while the low Pn velocities always lie in tectonically active regions like the western Tibetan plateau, Pamir, Tianshan and Hindu Kush. （2） Strong Pn anisotropy is found beneath the Indian-Eurasian collision zone; its direction is parallel to the collision are and nearly perpendicular to both the direction of maximum compression stress and relative crustal movement. The result is probably caused by the pure shear deformation in the uppermost mantle of the collision zone. （3） A geodynamic continent-continent collision model is proposed to show anisotropy and collision mechanisms between the Indian plate and the Tarim and Tajik basins.

KINEMATICS OF QUATERNARY EXTENSION IN THE PAMIR

We present kinematic constraints on the direction of Quaternary extension within the tectonically thickened crust of the Pamir,based on seismicity and fault\|slip data.The Pamir mountain belt of Central Asia is a direct consequence of the collision of the NW\|corner of the Indian indenter with Asia.It comprises Asian crust that is wedged between two opposite\|dipping continental subduction zones in the N and S,laterally blunted by strike\|slip and transgressive fault zones,and locally more than 70km thick (e.g.,Burtman and Molnar,1993).Active deformation in the Pamir is concentrated on compression and transgression along its margins.However,recently published seismic and neotectonic data also presented evidence for approximately E—W directed extension,roughly parallel to the main structural trends within the Pamir,along a N—S trending belt within the high terrain in the interior of the orogen (Strecker et al.,1995).or the central and southern portions of this N—S belt,preliminary kinematic analyses of seismic data from the Harvard moment tensor catalog indicate an extension direction of about 74=B0.This direction is based on presently available focal mechanisms for shallow earthquakes,weighted by their seismic moment;the extension directions calculated for the individual earthquakes vary between 52=B0 and 92=B0=46 or the northern most portion of this belt,earthquake focal mechanisms are not available.

Early Cretaceous deformation in the southern Tashkorgan region: Implications for the tectonic evolution of the northeastern Pamir

The Pamir Plateau comprises a series of crustal fragments that successively accreted to the Eurasian margin preceded the India-Asia collision,is an ideal place to study the Mesozoic tectonics.The authors investigate the southern Tashkorgan area,northeastern Pamir Plateau,where Mesozoic metamorphic and igneous rocks are exposed.New structural and biotite ^(40)Ar-^(39)Ar age data are presented.Two stages of intense deformation in the metamorphic rocks are identified,which are unconformably covered by the Early Cretaceous sediment.Two high-grade metamorphic rocks yielding 128.4±0.8 Ma and 144.5±0.9 Ma ^(40)Ar-^(39)Ar ages indicate that the samples experienced an Early Cretaceous cooling event.Combined with previous studies,it is proposed that the Early Cretaceous tectonic records in the southern Tashkorgan region are associated with Andean-style orogenesis.They are the results of the flat/low-angle subduction of the Neotethyan oceanic lithosphere.

Status of Mountain Pastures, Including Geobotanical Description of the Main Vegetation Associations in Western Pamir-Alay

The article gives a brief description of the vegetation cover of the Western Pamir-Alai range, as well as a method of describing the phytocenosis of the vegetation of the studied region.

A Demographic Structure of Populations of <i>Salvia Lilacinocoerulea</i>Nevski, a Rare Species Endemic to the Western Pamir-Alay (Uzbekistan, Turkmenistan)

Salvia lilacinocoerulea Nevski (Lamiaceae) is an endemic to the Western Pamir-Alay mountain range. Usually it grows on eroded clay soils among sparse juniper forests in the middle mountain belt. Studied coenopopulations of S. lilacinocoerulea are normal, but are not complete. Coenopopulations self-maintenance is carried out by the seed of renewal. The characteristic spectrum of S. lilacinocoerulea coenopopulation is centered, with a peak in the middle-generative individuals. In most cases, specific developmental spectrum of coenopopulation does not coincide with the characteristic ones. The demography structure of mostly investigated coenopopulations is satisfactory. The population growing on the grey clay soil, on strongly eroded slope among sparse juniper woodland was evaluated as critical due to absence in ontogenetic spectrum young individuals and small percentage of generative plant as well.