palaeo moisture evolution in monsoonal central asia during the last 50 000 years abstract the late quaternary climate history of monsoonal central asia was inferred from 75 palaeoclimatic records which provide information about moisture conditions in the last 50 ka or part of this period wet conditions occurred during middle and late marine isotope stage 3 while the last glacial maximum lgm was characterized by dry climate conditions in the region a stepwise climate amelioration is suggested by the climate records following the lgm several climate signals of this period which were reported from high latitude ice core records are preserved in archives from monsoonal central asia as well during the early holocene high effective moisture was inferred from most records from the area dominated by the indian monsoon e g the tibetan plateau suggesting that holocene optimal climate conditions occurred there during this period in contrast areas which are dominated by the south east asian monsoon se monsoon and the westerlies in north western and north central china mongolia do not uniformly show an early holocene climate optimum for this area optimal conditions prevailed during the mid holocene these apparent contradictions can possibly be explained by the regional uplift and descent of air masses in the holocene during the early holocene strengthened insolation possibly caused an enhanced low level convergence over the tibetan plateau which led to the intensification of the summer monsoon the strong air uplift caused intensified precipitation and air divergence in the upper troposphere over the tibetan plateau the areas adjacent to the north therefore experienced an intensified descent of air masses and consequently increased aridity the majority of the palaeoclimatic records suggest reduced effective moisture since the late holocene in the region

estimation of strain distribution using gps measurements in the kumaun region of lesser himalaya abstract the continuous process of continent continent collision between the indian and the eurasian plates has led to the formation of the himalayan range and continuously caused earthquakes in the region large earthquakes with magnitudes of 8 and above occur in this region infrequently releasing the elastic strain accumulated over years around the plate boundary geodetic measurements can help estimate the strain distribution along the fault system these measurements provide information on active deformations and associated potential seismic hazards along the himalayan arc in order to understand the present deformation around the plate boundary we collected gps data during three campaigns in the years of 2005 2007 at 16 sites in the kumaun region of the lesser himalaya horizontal velocity vectors estimated in itrf2000 are found to be in the range of 41 50 mm yr with an uncertainty level of the order of 1 mm yr the velocity field indicates that the present convergence of around 15 mm yr takes place in the kumaun himalaya further we estimate the strain components in the study area for understanding the currently active tectonic process in the region the estimated dilatational strain indicates that the northern part near the main central thrust mct is more compressional than the southern part maximum shear strain is mostly accommodated in the northern part too the maximum shear and dilatational strain rates are about 1 0 and 0 5 strain yr it is seen that the distribution of high shear strain spatially correlates with seismicity the maximum of extensional and compressional strains due to the force acting along the main central thrust mct in the nw se direction are found to be 0 4 and 0 1 strain yr respectively the maximum shear strain in the northern part of the himalaya appears to be associated with the convergence of the region proposed by other geophysical studies

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

convergence rate across the nepal himalaya and interseismic coupling on the main himalayan thrust implications for seismic hazard we document geodetic strain across the nepal himalaya using gps times series from 30 stations in nepal and southern tibet in addition to previously published campaign gps points and leveling data and determine the pattern of interseismic coupling on the main himalayan thrust fault mht the noise on the daily gps positions is modeled as a combination of white and colored noise in order to infer secular velocities at the stations with consistent uncertainties we then locate the pole of rotation of the indian plate in the itrf 2005 reference frame at longitude 1 34 3 31 latitude 51 4 0 3 with an angular velocity of 0 5029 0 0072 myr the pattern of coupling on the mht is computed on a fault dipping 10 to the north and whose strike roughly follows the arcuate shape of the himalaya the model indicates that the mht is locked from the surface to a distance of approximately 100 km down dip corresponding to a depth of 15 to 20 km in map view the transition zone between the locked portion of the mht and the portion which is creeping at the long term slip rate seems to be at the most a few tens of kilometers wide and coincides with the belt of midcrustal microseismicity underneath the himalaya according to a previous study based on thermokinematic modeling of thermochronological and thermobarometric data this transition seems to happen in a zone where the temperature reaches 350 c the convergence between india and south tibet proceeds at a rate of 17 8 0 5 mm yr in central and eastern nepal and 20 5 1 mm yr in western nepal the moment deficit due to locking of the mht in the interseismic period accrues at a rate of 6 6 0 4 10 19 nm yr on the mht underneath nepal for comparison the moment released by the seismicity over the past 500 years including 14 m w 7 earthquakes with moment magnitudes up to 8 5 amounts to only 0 9 10 19 nm yr indicating a large deficit of seismic slip over that period or very infrequent large slow slip events no large slow slip event has been observed however over the 20 years covered by geodetic measurements in the nepal himalaya we discuss the magnitude and return period of m 8 earthquakes required to balance the long term slip budget on the mht

mantle dynamics uplift of the tibetan plateau and the indian monsoon convective removal of lower lithosphere beneath the tibetan plateau can account for a rapid increase in the mean elevation of the tibetan plateau of 1000 m or more in a few million years such uplift seems to be required by abrupt tectonic and environmental changes in asia and the indian ocean in late cenozoic time the composition of basaltic volcanism in northern tibet which apparently began at about 13 ma implies melting of lithosphere not asthenosphere the most plausible mechanism for rapid heat transfer to the midlithosphere is by convective removal of deeper lithosphere and its replacement by hotter asthenosphere the initiation of normal faulting in tibet at about 8 3 ma suggests that the plateau underwent an appreciable increase in elevation at that time an increase due solely to the isostatic response to crustal thickening caused by india s penetration into eurasia should have been slow and could not have triggered normal faulting another process such as removal of relatively cold dense lower lithosphere must have caused a supplemental uplift of the surface folding and faulting of the indo australian plate south of india the most prominent oceanic intraplate deformation on earth began between about 7 5 and 8 ma and indicates an increased north south compressional stress within the indo australian plate a tibetan uplift of only 1000 m if the result of removal of lower lithosphere should have increased the compressional stress that the plateau applies to india and that resists india s northward movement from an amount too small to fold oceanic lithosphere to one sufficient to do so the climate of the equatorial indian ocean and southern asia changed at about 6 9 ma monsoonal winds apparently strengthened northern pakistan became more arid but weathering of rock in the eastern himalaya apparently increased because of its high altitude and lateral extent the tibetan plateau provides a heat source at midlatitudes that should oppose classical symmetric hadley circulation between the equator and temperate latitudes and that should help to drive an essentially opposite circulation characteristic of summer monsoons for the simple case of axisymmetric heating no dependence on longitude of an atmosphere without dissipation theoretical analyses by hou lindzen and plumb show that an axisymmetric heat source displaced from the equator can drive a much stronger meridianal monsoonlike circulation than such a source centered on the equator but only if heating exceeds a threshold whose level increases with the latitude of the heat source because heating of the atmosphere over tibet should increase monotonically with elevation of the plateau a modest uplift 1000 2500 m of tibet already of substantial extent and height might have been sufficient to exceed a threshold necessary for a strong monsoon the virtual simultaneity of these phenomena suggests that uplift was rapid approximately 1000 m to 2500 m in a few million years moreover nearly simultaneously with the late miocene strengthening of the monsoon the calcite compensation depth in the oceans dropped plants using the relatively efficient c4 pathway for photosynthesis evolved rapidly and atmospheric co2 seems to have decreased suggesting causal relationships and positive feedbacks among these phenomena both a supplemental uplift of the himalaya the southern edge of tibet and a strengthened monsoon may have accelerated erosion and weathering of silicate rock in the himalaya that in turn enhanced extraction of co2 from the atmosphere thus these correlations offer some support for links between plateau uplift a downdrawing of co2 from the atmosphere and global climate change as proposed by raymo ruddiman and froehlich mantle dynamics beneath mountain belts not only may profoundly affect tectonic processes near and far from the belts but might also play an important role in altering regional and global climates

contemporary crustal deformation around the southeast borderland of the tibetan plateau 1 we derive a detailed horizontal velocity field for the southeast borderland of the tibetan plateau using gps data collected from the crustal motion observation network of china between 1998 and 2004 our results reveal a complex deformation field that indicates that the crust is fragmented into tectonic blocks of various sizes separated by strike slip and transtensional faults most notably the regional deformation includes 10 11 mm yr left slip across the xianshuihe fault 7 mm yr left slip across the anninghe zemuhe xiaojiang fault zone 2 mm yr right slip across a shear zone trending northwest near the southern segment of the lancang river fault and 3 mm yr left slip across the lijiang fault deformation along the southern segment of the red river fault appears not significant at present time the region south and west of the xianshuihexiaojiang fault system whose eastward motion is resisted by the stable south china block to the east turns from eastward to southward motion with respect to south china resulting in clockwise rotation of its internal subblocks active deformation is detected across two previously unknown deformation zones one is located 150 km northwest of and in parallel with the longmenshan fault with 4 6 mm yr right slip and another is continued south southwestward from the xiaojiang fault abutting the red river fault with 7 mm yr left slip while both of these zones are seismically active the exact locations of faults responsible for such deformation are yet to be mapped by field geology comparing our gps results with predictions of various models proposed for tibetan plateau deformation we find that the relatively small sizes of the inferred microblocks and their rotation pattern lend support to a model with a mechanically weak lower crust experiencing distributed deformation underlying a stronger highly fragmented upper crust

interplay between soil formation and geomorphic processes along a soil catena in a mediterranean mountain landscape an integrated pedological and geophysical approach soil spatial distribution often shows high variability because of geo environmental settings affecting soil formation and geomorphic processes the paper describes a combined pedological geophysical approach for investigating the interplay among soil forming processes geomorphic dynamics and physico chemical soil properties in a soil catena in a mediterranean mountain landscape southern italy stocks of soil organic carbon soc and total nitrogen stn were determined and their interactions with slope position analyzed five slope units were defined along the soil catena summit shoulder back foot and toe slopes and in each of them a soil profile was dug and analyzed thickness of soil horizons and contact between soil and parent material were determined by a 2d electrical resistivity tomography survey results showed granitic bedrock is characterized by vary weathering degrees strongly affecting soil type development moreover soil properties variation is related to topographic features and water erosion processes soil chemical composition showed high values of sio2 and al2o3 probably due to inheritance from underlying granitic parent material particularly fe2o3 content increased with weathering conditions as shown by chemical index of alteration values along foot and toe slopes reworking and accumulation of colluvial soil lead to the formation of thicker accretionary a horizon consequently summit areas together with foot and toe slopes had greater soc and stn stocks than back and shoulder slopes that because soils are thicker and richer in soc on summit and valley bottom than in shoulder and back slope positions the proposed approach has showed the benefit of an integrated methodology for investigating spatial variations along soil catenas

cenozoic environmental evolution of the qaidam basin and its implications for the uplift of the tibetan plateau and the drying of central asia abstract a complete cenozoic pollen sequence of the qaidam basin has been constructed with absolute age control the cenozoic environmental evolution of the qaidam basin and its implications for the uplift of the tibetan plateau and the drying of central asia during the cenozoic era is discussed based on the interpretation of the pollen sequence the commencement of eolian deposition in central china and the change of climatic distribution pattern of china the results suggest that in the qaidam basin relatively dry climates prevailed in the eocene oligocene and pliocene pleistocene these dry periods resulted from the effects of a subtropical high pressure zone and the uplift of the surrounding mountains and the tibetan plateau respectively about a 600 km northward drift of western china has probably occurred during the late cenozoic resulting in the eocene oligocene arid climate belt twisting about six degrees of latitude the tibetan plateau reached probably 1500 m elevation by the latest miocene 8 5 ma not as high as it was thought previously the cenozoic environmental evolution of northwest china does not support the idea that the retreat of the paratethys sea played an important role in the late cenozoic drying of central asia at least not in northwest china

present day crustal thinning in the southern and northern tibetan plateau revealed by gps measurements gps measurements from sites within the tibetan plateau show not only east southeast west northwest extension but also more importantly horizontal dilation throughout the interior of the plateau assuming conservation of volume vertical thinning strain rates equal horizontal dilation rates and they 8 9 0 8 nanostrain a 1 and 7 4 1 2 nanostrain a 1 in northern and southern tibet and 12 0 3 2 nanostrain a 1 in its southwestern part suggest no measureable difference principal extensional strain rates also are similar in magnitude and orientation if crustal thinning began at 10 15 ma and the current rates of horizontal dilation applied both to the entire crust and to that period the crust should have thinned by 5 5 8 5 km if isostatic equilibrium applied the mean elevation of the plateau would have dropped 1 km the similar rates for northern southern and southwestern tibet suggest that the processes dictating crustal extension normal faulting and crustal thinning in the three regions differ little from one another

using 137cs and 210pbex to assess soil redistribution on slopes at different temporal scales abstract increasing risk of soil loss as a result of climate change has generated a need for reliable information on erosion rates at different temporal scales use of the fallout radionuclides 137 cs 210 pb ex and 7 be as tracers of sediment mobilization and redistribution makes it possible to obtain estimates of soil redistribution rates within both undisturbed and cultivated landscapes over a range of timescales mediterranean landscapes are characterized by a great diversity of physiography and land use and as a consequence erosion and deposition patterns are highly variable spatially to document such spatial variability a slope transect located in the subhumid pre pyrenean mountains ne spain was selected to use 137 cs and 210 pb ex to assess medium and longer term soil redistribution rates a total of 23 sectioned soil cores spaced 50 m apart were collected along the slope transect where 7 be had been previously used to document soil redistribution resulting from an individual storm event the inventories of both radionuclides varied markedly between 409 and 6080 bq m 2 for 137 cs and between 0 and 6734 bq m 2 for 210 pb ex estimates of soil redistribution derived from the 137 cs depth profiles using appropriate conversion models show that erosion rates along the transect vary between 2 6 and 31 9 mg ha 1 year 1 and that sedimentation rates vary between 0 2 and 24 5 mg ha 1 year 1 the highest soil losses occur in cultivated fields within the midslope zone of the transect while the highest deposition rates are found in tilled fields within the lower part of the transect erosion rates from 210 pb ex varied widely between 0 1 and 83 7 mg ha 1 year 1 on the lower slope whereas sedimentation rates ranged between 0 8 and 110 mg ha 1 year 1 also at the bottom slope the spatial distribution of the radionuclides along the transect reflects the effects of different land use and slope gradient on water erosion the results obtained confirm the potential for using 137 cs and 210 pb ex measurements for assessing soil redistribution on slopes in the mediterranean environment over different temporal scales

three dimensional velocity field of present day crustal motion of the tibetan plateau derived from gps measurements 1 using the measurements of 750 gps stations around the tibetan plateau for over 10 years since 1999 we derived a high resolution 3 d velocity field for the present day crustal movement of the plateau the horizontal velocity field relative to stable eurasia displays in details the crustal movement and tectonic deformation features of the india eurasia continental collision zone with thrust compression lateral extrusion and clockwise rotation the vertical velocity field reveals that the tibetan plateau is continuing to rise as a whole relative to its stable north neighbor however in some subregions uplift is insignificant or even negative the main features of the vertical crustal deformation of the plateau are the following a the himalayan range is still rising at a rate of 2 mm yr the uplift rate is 6 mm yr with respect to the south foot of the himalayan range b the middle eastern plateau has a typical uplift rate between 1 and 2 mm yr and some high mountain ranges in this area like the longmen shan and gongga shan have surprising uplift rates as large as 2 3mm yr c in the middle southern plateau there is a basin and endorheic subregion with a series of ns striking normal faults showing obvious sinking with the rates between 0 and 3 mm yr d the present day rising and sinking subregions generally correspond well to the cenozoic orogenic belts and basins respectively e at the southeastern corner of the plateau there is an apparent trend that the uplift rate is gradually decreasing from between 0 8 and 2 3 mm yr in the inner plateau to between 0 5 and 1 6 mm yr outside the plateau with the decrease of terrain height

spatially variable extension in southern tibet based on gps measurements 1 we use global positioning system gps data and kinematic block models to study the present day deformation of southern tibet gps data from 33 sites in southern tibet and nepal surveyed between 1991 and 2000 reveal 13 2 mm yr of n110 e extension between lhasa and shiquanhe 80 e 91 e of which 9 7 3 0 mm yr represents permanent extension of the tibetan crust the remaining 3 mm yr results from elastic deformation from the locked curving main himalayan thrust fault this extension is spatially nonuniform one half to two thirds of the permanent extension is concentrated across the yadong gulu rift with an opening rate of 6 5 1 5 mm yr most of the remainder occurs on or near the thakkola graben with little extension across the rifts between them differential velocities of sites north and south of the yarlung zangbo suture in western tibet imply that the suture or an adjacent structure may be active as a strike slip fault a numerical model suggests that right lateral strike slip on the yarlung zangbo suture may extend from the karakorum fault zone in the west at least to the yadong gulu rift in the east with 3 mm yr slip rate accommodating part of the eastward extrusion of tibet the convergence directions inferred from gps are consistent with slip vectors of earthquakes however the rate of slip of india beneath tibet along the himalaya is lower than those previously estimated we estimate a slip rate of 12 4 0 4 mm yr between longitudes 83 e and 88 e and 17 1 and 19 1 mm yr in the western and eastern himalaya respectively the variable slip rate correlates with the variable extension rate in southern tibet and we suggest that it results from variation in the deformation rate of the overriding tibetan crust we infer that the slower convergence rate in the central himalaya is significant

present day crustal motion within the tibetan plateau inferred from gps measurements 1 using the measurements of 726 gps stations around the tibetan plateau we determine the rigid rotation of the entire plateau in a eurasia fixed reference frame which can be best described by an euler vector of 24 38 0 42 n 102 37 0 42 e 0 7096 0 0206 ma the rigid rotational component accommodates at least 50 of the northeastward thrust from india and dominates the eastward extrusion of the northern plateau after removing the rigid rotation to highlight the interior deformation within the plateau we find that the most remarkable interior deformation of the plateau is a glacier like flow zone which starts at somewhere between the middle and western plateau goes clockwise around the eastern himalayan syntaxis ehs and ends at the southeast corner of the plateau with a fan like front the deformation feature of the southern plateau especially the emergence of the flow zone could be attributed to an eastward escape of highly plastic upper crustal material driven by a lower crust viscous channel flow generated by lateral compression and gravitational buoyancy at the later developmental stage of the plateau the first order feature of crustal deformation of the northeastern plateau can be well explained by a three dimensional elastic half space dislocation model with rates of dislocation segments comparable to the ones from geological observations in the eastern plateau although gps data show no significant convergence between the eastern margin of the plateau and the sichuan basin a small but significant compressional strain rate component of 10 5 2 8 nstrain yr exists in a relatively narrow region around the eastern margin in addition a large part of the eastern plateau northeast of the ehs is not undergoing shortening along the northeastward convergence direction of the ehs but is stretching

deep seismic reflection evidence for continental underthrusting beneath southern tibet the himalaya and adjacent tibetan plateau constituting earth s largest region of elevated topography and anomalously thick crust formed as a consequence of cenozoic collision between india and asia itself considered the archetypal continent continent collision1 3 here we report the first results from an attempt to image the structure of the crust beneath this region using deep seismic reflection profiling our 100 km long profile acquired in the tethyan himalaya shows a mid crustal reflection that prob ably marks the active thrust fault along which the indian plate is underthrusting southern tibet upper crustal reflections with geo metries suggestive of large scale structural imbrication of the upper crust and moho reflections from the base of the double normal thickness crust underlying the region these results lend substantial support to the view that crustal thickening beneath southernmost tibet was accomplished by wholesale underthrusting of indian continental crust beneath the structurally imbricated upper crust comprising the tethyan himalaya

clockwise rotation of the brahmaputra valley relative to india tectonic convergence in the eastern himalaya naga hills and shillong plateau gps data reveal that the brahmaputra valley has broken from the indian plate and rotates clockwise relative to india about a point a few hundred kilometers west of the shillong plateau the gps velocity vectors define two distinct blocks separated by the kopili fault upon which 2 3 mm yr of dextral slip is observed the shillong block between longitudes 89 and 93 e rotating clockwise at 1 15 myr and the assam block from 93 5 e to 97 e rotating at 1 13 myr these two blocks are more than 120 km wide in a north south sense but they extend locally a similar distance beneath the himalaya and tibet a result of these rotations is that convergence across the himalaya east of sikkim decreases in velocity eastward from 18 to 12 mm yr and convergence between the shillong plateau and bangladesh across the dauki fault increases from 3 mm yr in the west to 8 mm yr in the east this fast convergence rate is inconsistent with inferred geological uplift rates on the plateau if a 45 n dip is assumed for the dauki fault unless clockwise rotation of the shillong block has increased substantially in the past 4 8 myr such acceleration is consistent with the reported recent slowing in the convergence rate across the bhutan himalaya the current slip potential near bhutan based on present day convergence rates and assuming no great earthquake since 1713 a d is now 5 4 m similar to the slip reported from alluvial terraces that offsets across the main himalayan thrust and sufficient to sustain a mw 8 0 earthquake in this area

coseismic slip distribution of the 2008 mw 7 9 wenchuan earthquake from joint inversion of gps and insar data on 12 may 2008 the m w 7 9 wenchuan earthquake occurred at the eastern margin of the tibetan plateau along the longmen shan fault based on previous geological and geophysical studies and offset maps from advanced land observing satellite phased array type l band synthetic aperture radar alos palsar data a layered crustal structure and a five segment rupture model are established to study the coseismic deformation of this event using the constrained least squares method a preferred coseismic slip model is derived from global positioning system gps and interferometric synthetic aperture radar insar data in particular the helmert variance component estimation hvce method is used to determine the relative weight ratio between the gps and insar data in contrast to the initial weight ratio 0 752 0 246 0 002 among three type observations gps horizontal gps vertical and insar los displacement the final optimal weight ratio is found to be 0 473 0 279 0 248 and the overall root mean square rms misfit for all three datasets decreases from 9 15 cm without hvce to 5 46 cm with hvce as revealed by the preferred slip the slip changes obviously along the strike direction from southwest to northeast and exhibits four asperities close to hongkou town yuejiashan town beichuan county and nanba town respectively two major asperities are located on the hongkou and beichuan segments with the maximum slip close to 10 m the slips of hongkou yuejiashan and beichuan segments are dominated by the thrust movement with a significant right lateral strike slip component the qingchuan segment experiences a dominant right lateral strike slip with an average magnitude of 1 2 m most of the slip asperities are shallower than 10 km depth except for the southwest part near the hypocenter where the slip may exceed 20 km the seismic moment of the wenchuan earthquake is 8 19 1020 n m m w 7 91 based on the layered crust model which is slightly larger than that using a corresponding homogeneous crust model m w 7 87

one dimensional reference velocity model and precise locations of earthquake hypocenters in the kumaon garhwal himalaya we report an optimum 1d velocity model of the kumaon garhwal himalaya based on analysis of 5000 seismograms generated at 50 digital broadband seismic stations in the region during april 2005 and june 2008 these include data from 385 local earthquakes with azimuth gaps of 180 each of which had a minimum of seven p and five s phase readings this velocity model was then used to map the locations of 1150 earthquakes 1 m 5 that occurred in the region a majority 75 of these earthquakes occurred in the upper 20 km of the crust largely above the main himalayan thrust and forms an 10 km wide band along the surface trace of the munsiari thrust however we also find another parallel band of earthquakes about 70 km to its southwest through the tehri dam in the lesser himalaya and a significant number 15 both in the tethys himalaya and within the flexed crust of the underthrusting indian plate beneath the ganga basin furthermore unlike the reported absence of seismicity in the lower crust of the nepal himalaya and its reappearance in the shallow mantle the kumaon garhwal himalayan crust is found to be seismically active throughout with no event reliably recorded in the shallow mantle of this region during the epoch of our seismic recording online material figures show constrains and distribution of data used in joint inversion and table shows p and s wave corrections obtained from travel time inversion

a 250 000 year climatic record from great basin vein calcite implications for milankovitch theory a continuous record of oxygen 18 18o variations in the continental hydrosphere during the middle to late pleistocene has been obtained from a uranium series dated calcitic vein in the southern great basin the vein was deposited from ground water that moved through devils hole an open fault zone at ash meadows nevada between 50 and 310 ka thousand years ago the configuration of the 18o versus time curve closely resembles the marine and antarctic ice core vostok 18o curves however the u th dates indicate that the last interglacial stage marine oxygen isotope stage 5 began before 147 3 ka at least 17 000 years earlier than indicated by the marine 18o record and 7 000 years earlier than indicated by the less well dated antarctic 18o record this discrepancy and other differences in the timing of key climatic events suggest that the indirectly dated marine 18o chronology may need revision and that orbital forcing may not be the principal cause of the pleistocene ice ages

asynchronous holocene climatic change across china a review of holocene climatic variations in different parts of china shows that they were asynchronous proxy data from ice cores pollen loess lacustrine sediments and changes of sea and lake levels demonstrate that many warm and cold oscillations have occurred in china during the holocene including a most important climatic event known as the holocene optimum a milder and wetter period and that the duration and amplitude of the optimum period as well as its start and end times differed in different parts of china uplift of the tibetan plateau over the past millions of years led to the development of the monsoon climate and to complex atmospheric circulation over continental china during the holocene as a result the holocene optimum began and terminated earlier in high altitude regions of western china than at lower elevations in eastern china and the amplitude of the variations was lower in the east this suggests that the western higher altitude areas were more sensitive to climatic change than were the eastern lower altitude areas holocene climatic records in the dunde and guliya ice cores do not correspond inverse 18o variations between the two cores indicate that the effects of climate and atmospheric processes on the stable isotopes at the two sites differed the correlation between the isotopic composition of carbonates in lake deposits in western china and climatic variations is similar to that in the ice cores the climatic resolution in ice cores and lake sediments is higher than that in other media the lack of precise correspondence of climatic records constructed on the basis of proxy data from different parts of china is a result of the different locations and elevations of the sampling sites the different resolutions of the source material and the varied climatic conditions within china further work is needed to confirm both the conclusions and the inferences presented here

magnesium content of non marine ostracod shells a new palaeosalinometer and palaeothermometer abstract ostracods are microcrustaceans with calcitic carapaces each consisting of two valves or shells that grow by moulting and regeneration of sequentially larger valves up to nine times before reaching maturity the mg content of these valves is species dependent and is a function of their growth stage and the temperature salinity mg content and mg ca ratio of their host water newly formed partly calcified valves of the non marine nektic ostracod mytilocypris henricae have high mg contents 100 000 ppm mg in caco3 at individual shell weights of 2 g this relative mg content decreases as calcification proceeds until shell weights exceed 120 g whereupon the mg content is constant and useful as an indicator of the ostracod s environment mg ca ratios in individual ostracod valves from several species of the genera mytilocypris and australocypris from culture experiments and a series of australian lakes indicate that the valve s mg content increases as a function of increasing temperature and salinity within the range 11 25 c and for waters containing 24 2325 ppm mg the molar mg ca ratio in these ostracods fully calcified valves increases by 0 0015 or 370 ppm mg in caco3 per 1 c and per change of 125 ppm mg in solution for most mainland australian lakes a change in water composition of 125 ppm mg corresponds to a change of 3 5 in salinity for a given mg content of a lake the mg ca ratio of the water may vary within the range of common lacustrine values without significantly affecting mg uptake in the ostracod valves these relationships can provide palaeosalinities and or palaeotemperatures for ostracods recovered from continental sediments for mg partitioning an increase in temperature and salinity produce increased mg content in ostracods whereas for 18o fractionation in biogenic calcite an increase in temperature produces a decrease in 18o of the ostracod and an increase in salinity leads to an increase in 18o of the ostracod thus a combination of 18o and mg measurements on non marine ostracods should enable unique resolution of palaeotemperature and palaeosalinity variations

geodetic model of the 2015 april 25 mw 7 8 gorkha nepal earthquake and mw 7 3 aftershock estimated from insar and gps data

uplift driven climate change at 12 ma a long δ18o record from the ne margin of the tibetan plateau carbonates from fluvial and lacustrine sediments were sampled from multiple measured sections in the linxia basin of western china based on textural and mineralogical evidence lacustrine carbonates are primary precipitates from lake water a 29 million year record of the oxygen isotope composition of meteoric water is inferred from the n 18 o values of these carbonates this inference is based on the most negative n 18 o values in the lake carbonates which represent lake waters that have experienced the least evaporative enrichment carbonate n 18 o values a proxy for rainfall n 18 o are v310 5x throughout the interval of 29 12 ma at 12 ma there is a shift to 39x a value that remains into the pliocene this implies a major reorganization of atmospheric circulation patterns and a shift to more arid conditions at the ne margin of the tibetan plateau with the post 12 ma system similar to that of today the 12 ma event may represent the time at which the tibetan plateau achieves sufficient elevation to block the penetration of moisture from the indian ocean or south pacific into western china the period of greatest aridity is from 9 6 to 8 2 ma a time interval which agrees well with other climate records 2003 elsevier b v all rights reserved

northeastward growth of the tibet plateau deduced from balanced reconstruction of two depositional areas the qaidam and hexi corridor basins china we address the problem of late cenozoic uplift erosion and growth of northeastern tibet by reconstructing from isopach maps and drill holes the volumes and masses of sediments deposited in the qaidam and hexi corridor basins since 35 myr ago the mass budget is based on simple geometrical assumptions such as regional similarity of the thickness ratios between strata of different ages in the qaidam where our record extends back to the oligocene the budget shows a huge rise of the accumulation rates after the beginning of the pliocene 5 3 ma the early pliocene seems to be the period of maximum deposition with accumulation rates in excess of 1 mm yr 1 2 7 kg m 2 yr 1 of compacted rocks throughout the basin there also seems to be a southeastward shift of the largest depocenters between the upper pliocene 3 4 1 6 ma and the quaternary in the hexi corridor sedimentation is confined to small foreland flexural depressions associated with the frontal thrusts of the qilian shan and occurs at an average rate one order of magnitude smaller than in the qaidam basin the accumulation rate is maximum in the quaternary the sedimentation history appears to support a plateau building mechanism resulting from the combination of two geologicallly common processes crustal scale thrusting and sedimentary basin infilling the time needed to completely fill the qaidam basin and make its catchment a plateau closely resembling that of the highest part of tibet qangtang is of the order of 9 myr the mechanism now at work north of the kunlun which involves rapid infilling of broad flat areas separated by relatively narrow mountain ranges has thus probably been important in producing the high smooth topography that characterizes much of central tibet

late cenozoic climate changes in china s western interior a review of research on lake qinghai and comparison with other records abstract we review late cenozoic climate and environment changes in the western interior of china with an emphasis on lacustrine records from lake qinghai widespread deposition of red clay in the marginal basins of the tibetan plateau indicates that the asian monsoon system was initially established by 8 ma when the plateau reached a threshold altitude subsequent strengthening of the winter monsoon along with the establishment of the northern hemisphere ice sheets reflects a long term trend of global cooling the few cores from the tibetan plateau that reach back a million years suggest that they record the mid pleistocene transition from glacial cycles dominated by 41 ka cycles to those dominated by 100 ka cycles during terminations i and ii strengthening of the summer monsoon in china s interior was delayed compared with sea level and insolation records and it did not reach the western tibetan plateau and the tarim basin lacustrine carbonate 18 o records reveal no climatic anomaly during mis3 so that high terraces interpreted as evidence for extremely high lake levels during mis3 remain an enigma following the last glacial maximum lsm several lines of evidence from lake qinghai and elsewhere point to an initial warming of regional climate about 14 500 cal yr bp which was followed by a brief cold reversal possibly corresponding to the younger dryas event in the north atlantic region maximum warming occurred about 10 000 cal yr bp accompanied by increased monsoon precipitation in the eastern tibetan plateau superimposed on this general pattern are small amplitude centennial scale oscillations during the holocene warmer than present climate conditions terminated about 4000 cal yr bp progressive lowering of the water level in lake qinghai during the last half century is mainly a result of negative precipitation evaporation balance within the context of global warming

fault dip angle determination with the jℛi criterion and coulomb stress changes associated with the 2015 mw 7 9 gorkha nepal earthquake revealed by insar and gps data abstract minimizing data misfit has been widely used in geodetic determination of fault dip angle however it ignores the contribution from data noise here we use the j i criterion which takes into account both data misfit and the contribution from data noise to determine dip angle synthetic tests show dip angle estimates with the j i criterion are more accurate and robust than those with data misfit minimization we applied this j i criterion to the determination of the dip angle of the 2015 mw 7 9 gorkha nepal earthquake using interferometric synthetic aperture radar insar and global positioning system gps data the results show that the event ruptured to the north of kathmandu with a maximum slip value of 5 8 m and a dip angle of 9 5 we also calculated the coulomb failure stress changes resolved onto the receiver faults that are generally consistent with the fault geometry of this event suggesting the possible triggering relation to aftershocks with low dip angles and a zone of seismic potential located to the west of the rupture zone

potential earthquake precursory pattern from space the 2015 nepal event as seen by magnetic swarm satellites abstract a large earthquake of 7 8 magnitude occurred on 25 april 2015 06 26 utc with the epicenter in nepal here taking advantage of measurements provided by the swarm magnetic satellites we investigate the possibility to detect some series of pre earthquake magnetic anomalous signals likely due to a lithosphere atmosphere ionosphere coupling that can be a potential earthquake precursory pattern different techniques have been applied to swarm data available during two months around earthquake occurrence from the detected magnetic anomalies series during night and magnetically quiet times or with an automatic detection algorithm we show that the cumulative number of anomalies follows the same typical power law behavior of a critical system approaching its critical time and hence recovers as the typical recovery phase after a large event the similarity of this behavior with the one obtained from seismic data analysis and the application of the analyses also to another period without significant seismicity do support a lithospheric linked origin of the observed magnetic anomalies we suggest that they might be connected to the preparation phase of the nepal earthquake

great earthquakes seismicity gaps and potential for earthquake disaster along the himalaya plate boundary abstract analysis of the space time patterns of seismicity in the himalaya plate boundary has established the existence of three seismic gaps 1 1 the kashmir gap lying west of the 1905 kangra earthquake 2 2 the central gap situated between the 1905 kangra and the 1934 bihar earthquakes 3 3 the assam gap between the 1897 and 1950 assam earthquakes this study has shown that the above great earthquakes were preceded as well as followed by long periods 19 years of decreased levels of seismic activity in the epicentral regions remarkable decrease in the seismicity following the year 1970 has been observed in the western half of the central gap as well as in the assam gap local seismic investigation in the assam gap confirms this feature and the seismicity suggests the existence there of an asperity the local seismic investigations in garhwal himalaya have shown that the small earthquakes are confined to the upper 6 8 km of the crust and may have strike slip motions these earthquakes occur in a region where teleseismically recorded events were few

slip maxima at fault junctions and rupturing of barriers during the 2008 wenchuan earthquake the devastating wenchuan earthquake in 2008 struck along a fault zone that showed low rates of deformation analysis of gps and insar data suggests that as structural barriers failed during a single earthquake the rupture cascaded across multiple fault segments which may explain the high magnitude of the event

paleoseismological evidence of surface faulting along the northeastern himalayan front india timing size and spatial extent of great earthquakes the similar to 2500 km long himalayan arc has experienced three large to great earthquakes of m w 7 8 to 8 4 during the past century but none produced surface rupture paleoseismic studies have been conducted during the last decade to begin understanding the timing size rupture extent return period and mechanics of the faulting associated with the occurrence of large surface rupturing earthquakes along the similar to 2500 km long himalayan frontal thrust hft system of india and nepal the previous studies have been limited to about nine sites along the western two thirds of the hft extending through northwest india and along the southern border of nepal we present here the results of paleoseismic investigations at three additional sites further to the northeast along the hft within the indian states of west bengal and assam the three sites reside between the meizoseismal areas of the 1934 bihar nepal and 1950 assam earthquakes the two westernmost of the sites near the village of chalsa and near the nameri tiger preserve show that offsets during the last surface rupture event were at minimum of about 14 m and 12 m respectively limits on the ages of surface rupture at chalsa site a and nameri site b though broad allow the possibility that the two sites record the same great historical rupture reported in nepal around a d 1100 the correlation between the two sites is supported by the observation that the large displacements as recorded at chalsa and nameri would most likely be associated with rupture lengths of hundreds of kilometers or more and are on the same order as reported for a surface rupture earthquake reported in nepal around a d 1100 assuming the offsets observed at chalsa and nameri occurred synchronously with reported offsets in nepal the rupture length of the event would approach 700 to 800 km the easternmost site is located within harmutty tea estate site c at the edges of the 1950 assam earthquake meizoseismal area here the most recent event offset is relatively much smaller 2 5 m and radiocarbon dating shows it to have occurred after a d 1100 after about a d 1270 the location of the site near the edge of the meizoseismal region of the 1950 assam earthquake and the relatively lesser offset allows speculation that the displacement records the 1950 m w 8 4 assam earthquake scatter in radiocarbon ages on detrital charcoal has not resulted in a firm bracket on the timing of events observed in the trenches nonetheless the observations collected here when taken together suggest that the largest of thrust earthquakes along the himalayan arc have rupture lengths and displacements of similar scale to the largest that have occurred historically along the world s subduction zones

postseismic deformation associated with the 2015 mw 7 8 gorkha earthquake nepal investigating ongoing afterslip and constraining crustal rheology abstract the 2015 mw 7 8 gorkha earthquake has not only imposed effective constraints on the geometrical structures friction behaviours and seismogenic patterns of the nepal himalaya thrust systems but has also provided valuable insights into the uplift mechanism and lithosphere rheology of the tibetan plateau here 1 6 year gps observations are used to reveal the postseismic deformation characteristics following the gorkha earthquake investigate the ongoing aseismic afterslip on the main himalayan thrust mht fault and constrain the crustal rheology of the southern tibetan plateau first afterslip is considered to be solely responsible for the postseismic deformation afterslip only model the results show that afterslip is anticorrelated with peak coseismic slip areas one high afterslip concentration area with a peak of 24 cm is distributed downdip of the coseismic rupture as well as in two other regions one partially overlapping the mainshock rupture and the other next to the mw 7 3 aftershock area second the gps postseismic observations are inverted to jointly investigate afterslip and viscoelastic deformation multiple mechanism model the afterslip inversion results of the above two models are highly consistent indicating the dominant contribution of afterslip to surface deformation during the 1 6 year postseismic period considering the interseismic fault coupling and historical seismicity no appreciable fault slip associated with the gorkha earthquake is found to occur both updip and west of the mainshock rupture areas this reveals that the gorkha earthquake only unzipped the lower edge of the locked portion of the mht leaving the shallow portion and western segment of the seismogenic zone still locked and the nepal region under high seismic risk the viscoelastic mechanism contributes minorly to surface deformation during the 1 6 year postseismic period the middle lower crust is assumed to comprise maxwell material beneath an elastic 25 km thick upper crust and the optimal viscosity is conservatively estimated to be 1 6 1019 pa s beneath the southern tibetan plateau which should be robustly constrained with more long term observations more effective spatial constraints and more detailed crustal models

coseismic fault slip of the 2008 mw 7 9 wenchuan earthquake estimated from insar and gps measurements 1 we infer co seismic fault slip during the 2008 mw 7 9 wenchuan earthquake from interferometric synthetic aperture radar insar and gps observations of ground deformation we use alos palsar data from ascending orbits on six tracks and we do not use data that are strongly affected by ionospheric perturbations we use a fault model composed of three planar fault segments of the beichuan fault and one planar segment representing the parallel pengguan fault maximum thrust slip is up to 6 7 m near the surface and occurs in two locations near yingxiu in the south and beichuan in the center of the rupture maximum strike slip is over 4 m and occurs near pingtong and nanba along the northern end of the rupture we find that the ratio of coseismic thrust to strike slip on the beichuan fault decreases from 1 5 to 0 7 from the sw to the ne citation feng g e a hetland x ding z li and l zhang 2010 coseismic fault slip of the 2008 mw 7 9 wenchuan earthquake estimated from insar and gps measurements geophys res lett 37 l01302 doi 10 1029 2009gl041213

rupture of deep faults in the 2008 wenchuan earthquake and uplift of the longmen shan the longmen shan mountains rise up 6 000 m over a distance of just 100 km but the mechanisms driving formation of this striking topography are debated analyses of crustal movements during the 2008 wenchuan earthquake suggest that fault induced uplift plays a role in building the high topography

continuous deformation of the tibetan plateau from global positioning system data global positioning system velocities from 553 control points within the tibetan plateau and on its margins show that the present day tectonics in the plateau is best described as deformation of a continuous medium at least when averaged over distances of 100 km deformation occurs throughout the plateau interior by ese wnw extension and slightly slower nne ssw shortening relative to eurasia material within the plateau interior moves roughly eastward with speeds that increase toward the east and then flows southward around the eastern end of the himalaya crustal thickening on the northeast ern and eastern margins of the plateau occurs over a zone 400 km wide and cannot be the result of elastic strain on a single major thrust fault shortening there accommodates much of india s penetration into eurasia a description in terms of movements of rigid blocks with elastic strain associated with slip on faults between them cannot match the velocity field

late cenozoic eolian deposition in the north pacific asian drying tibetan uplift and cooling of the northern hemisphere a newly constructed record of eolian dust accumulation from the central north pacific shows that dust deposition increased by an order of magnitude quite rapidly at 3 6 ma we associate this sudden drying with the uplift of at least the northern portion of the tibetan plateau shutting off the indian ocean moisture source to central and western china this ten fold increase in atmospheric dust loading appears to be associated with the 1 m y long shift toward heavy 18o values that occurred at 3 6 2 6 ma the dust grain size record of wind intensity begins its late cenozoic coarsening a million years before the drying event at 4 5 ma the northern hemisphere cooling that results in intensification of the subpolar westerly winds may have as its ultimate cause the drawdown of atmospheric co2 in the latest miocene and the early pliocene closing of the panamanian seaway

the contribution of orbital forcing to the progressive intensification of northern hemisphere glaciation in this study we reconstruct the timing of the onset of northern hemisphere glaciation this began in the late miocene with a significant build up of ice on southern greenland however progressive intensification of glaciation did not begin until 3 5 3 ma when the greenland ice sheet expanded to include northern greenland following this stage we suggest that the eurasian arctic and northeast asia were glaciated at approximately 2 74 ma 40 ka before the glaciation of alaska 2 70 ma and about 200 ka before significant glaciation of the north east american continent 2 54 ma we also review the suggested causes of northern hemisphere glaciation tectonic changes such as the uplift of the himalayan and tibetan plateau the deepening of the bering strait and the emergence of the panama isthmus are too gradual to account entirely for the speed of northern hemisphere glaciation we therefore postulate that tectonic changes may have brought global climate to a critical threshold but the relatively rapid variations in the earth s orbital parameters and thus insolation triggered the intensification of northern hemisphere glaciation this theory is supported by computer simulations which despite the relative simplicity of the model and the approximation of some factors e g using a linear carbon dioxide scenario neglecting the geographical difference between the pliocene and the present suggest that it is possible to build up northern hemisphere ice sheets between 2 75 and 2 55 ma by varying only the insolation controlled by the orbital parameters c 1998 elsevier science ltd all rights reserved

slip model of the 2015 mw 7 8 gorkha nepal earthquake from inversions of alos 2 and gps data we use surface deformation measurements including interferometric synthetic aperture radar data acquired by the alos 2 mission of the japanese aerospace exploration agency and global positioning system gps data to invert for the fault geometry and coseismic slip distribution of the 2015 mw 7 8 gorkha earthquake in nepal assuming that the ruptured fault connects to the surface trace of the main frontal thrust mft fault between 84 34 e and 86 19 e the best fitting model suggests a dip angle of 7 the moment calculated from the slip model is 6 08 1020 nm corresponding to the moment magnitude of 7 79 the rupture of the 2015 gorkha earthquake was dominated by thrust motion that was primarily concentrated in a 150 km long zone 50 to 100 km northward from the surface trace of the main frontal thrust mft with maximum slip of 5 8 m at a depth of 8 km data thus indicate that the 2015 gorkha earthquake ruptured a deep part of the seismogenic zone in contrast to the 1934 bihar nepal earthquake which had ruptured a shallow part of the adjacent fault segment to the east

geochemical evolution of closed basin lakes general model and application to lakes qinghai and turkana in contrast to most previous models for the evolution of closed basin lakes we present an integrated model which considers various water budget patterns clay regradation so4 reduction and subbottom leakage in addition to the classical equilibrium approach of mineral precipitation the model was applied to lakes qinghai and turkana which significantly differ in the lithologies of their drainage areas but are representative of the carbonate rich sedimentary rock province of the tibet qinghai plateau and the silicate rock province of eastern africa both lakes are now topographically closed but to some degree hydrologically open subbottom leakage major results of the mode calculations show that the lithology controls the ultimate brine which is of na k cl type for qinghai lake and of na hco3 cl type for lake turkana so4 reduction delays the onset of sulfatic mineral precipitation and favours the formation of na carbonates such as trona at the expense of calcite clay mineral regradation plays an important role before the saturation of sulfatic or chlorine minerals is reached in particular magnesite formation may be in competition with mg bearing clay minerals finally simulations with various hydrological scenarios have shown that the modern hydrochemistry of both lakes cannot be reproduced by simply evaporating inflow water but reflects long term accumulation and evolution of solutes by continuous inflow over several thousand years the diversity of lake water composition within a uniform lithological province can thus be largely ascribed to varying hydrological conditions

long term growth of the himalaya inferred from interseismic insar measurement the rise and support of the 5000 m topographic scarp at the front of indian eurasian collision in the himalaya involves long term uplift above a mid crustal ramp within the main himalayan thrust mht system locking of the shallower portion of the flat ramp flat during the interseismic period also produces transient uplift above the transition zone however spatial and temporal relationships between permanent and transient vertical deformation in the himalaya are poorly constrained leading to an unresolved causal relationship between the two here we use interferometric synthetic aperture radar insar to measure interseismic uplift on a transect crossing the whole himalaya in central nepal the uplift velocity of 7 mm yr at the front of the annapurna mountain range is explained by an 18 21 mm yr slip rate on the deep shallow dipping portion of the mht with full locking of the mid crustal ramp underlying the high himalaya the transient uplift peak observed by insar matches spatially with the long term uplift peak deduced from the study of trans himalayan river incision although models of the seismic cycle involving thrusting over a ramp of fixed geometry predict an 20 km separation between the two peaks we argue that this coincidence indicates that today s mid crustal ramp in central nepal is located southward with respect to its average long term location suggesting that mountain growth proceeds by frontward migration of the ramp driven by underplating of material from the indian plate under the himalaya

himalayan seismic hazard the devastating earthquake in bhuj on 26 january 2001 highlighted the high earthquake risk in the indian region of gujarat in their perspective bilham et al warn that major earthquakes may be expected in another part of india the himalayan arc an analysis of historic earthquakes suggests that several major earthquakes are overdue in this region but that recent low activity has focused attention away from the himalayan arc projections from earlier earthquakes suggest that just one of the possibly overdue himalayan earthquakes may lead to 200 000 predictable fatalities

afterslip and viscoelastic relaxation following the 1999 m 7 4 izmit earthquake from gps measurements summary intensive global positioning system gps monitoring after the 1999 izmit earthquake provides an opportunity to understand the postseismic behaviour of a strike slip fault and the rheology below the brittle upper crust two data sets are available displacements measured during the first 300 days after the izmit earthquake and velocity measurements between 2003 and 2005 using an inversion method and a forward modelling respectively we investigate two mechanisms 1 afterslip on and below the coseismic rupture plane and 2 viscoelastic stress relaxation in the lower crust and upper mantle described by a maxwell or a standard linear solid sls rheology the inversion results show that the first several months following the izmit earthquake were dominated by afterslip at depths shallower than 30 km and the slip amount decayed with time after that apparent afterslip has a very different spatial distribution and is located much deeper for viscoelastic relaxation a model with an elastic upper crust and a maxwell viscoelastic lower crust overlying a maxwell mantle e m m fits the data measured in the first 300 days better in the far field than in the near field however the observed far field 300 day displacement and the long term 2003 2005 displacement which might be dominated by viscoelastic relaxation cannot be described by a maxwell rheological model with constant viscosity the effective viscosity increases over time therefore we have built a refined rheological model an elastic upper crust and an sls lower crust overlying a maxwell viscoelastic mantle e sls m our best solution yields a viscosity for the lower crust of 2 1018 pa s a relaxation strength of 2 3 and a viscosity for the maxwell mantle of 7 1019 pa s finally we explain the data using a composite model consisting of the preferred e sls m model and the afterslip model obtained from the residual displacement after correcting for viscoelastic relaxation for the early time period the residual displacements can be mainly explained by a shallow afterslip whose magnitude decays with time and whose spatial distribution is stable whereas the residual displacements for the later time period require negligible afterslip it indicates that the postseismic deformation in the later time period induced by a deep source can be almost entirely explained by the e sls m model the composite model can generally explain the data in the entire spatial and temporal space

development of asian monsoon revealed by marked ecological shift during the latest miocene in northern pakistan carbon isotopes from soil carbonate1 4 and soil organic matter5 6 yield palaeoecological information because the carbon in the soil carbonate forms in isotopic equilibrium with local soil co2 refs 1 7 the isotopic composition of which is in turn determined by local plant cover siwalik group sediments in northern pakistan contain a well exposed palaeosol record spanning the past 18 myr here we report on stable carbon isotope results from associated pedogenic carbonate which indicate a dramatic ecological shift from to dominated floodplain biomass beginning 7 4 7 0 myr ago the earlier c3 floodplain biomasses were probably mainly composed of trees and shrubs whereas c4 grasslands dominated in the plio pleistocene oxygen isotopes also exhibit a shift in the latest miocene probably corresponding to a major climate change which may have induced the forest to grassland transition this dramatic ecological shift in the latest miocene may mark the inception or a marked strengthening of the asian monsoon system

coseismic deformations of the 2015 mw 7 8 gorkha earthquake and interseismic strain accumulation in the himalayan tectonic belt and tibetan plateau abstract the principal strain rate derived from gps velocities from the tibetan plateau and the india plate shows that the himalayan tectonic belt exhibits compression deformation in a ne ns ne direction from the west to the east the gps velocity profiles reflect that the distribution of strain accumulation is uneven there is a 17 1 mm yr compressive deformation distributed over 400 km along 85 e longitude a 20 9 22 2 mm yr compressive deformation dispersed across 400 500 km along 79 e longitude and a 15 3 16 9 mm yr compressive deformation spread across 500 600 km along 91 e longitude the mw 7 8 gorkha earthquake occurred at the edge of an intense compression deformation zone of about 6 0 10 8 yr in a north south direction and an about 90 compressive strain is absorbed in the 300 km region near the main frontal thrust mft coseismic displacements larger than three standard deviations 3sd are mainly concentrated within 360 km from the epicenter the nodal plane of the main shock divides the areas where tensile strain release in an exponential attenuation pattern is dominant to the north and where compressive strain with upward movement is dominant to the south the results inversed by the sdm program reveal that the maximal slip of the gorkha earthquake is 5 33 m and its moment magnitude is mw 7 85 and the largest stress drop is 4 21 mpa slips larger than 0 5 m are mainly distributed in a region approximately 135 km 105 km which show that the rupture of the gorkha earthquake does not reach the surface finally we estimate that the recurrence period of this earthquake is about 166 20 years according to the strain accumulation before the earthquake and the coseismic release feature

mobilization and re distribution of major and trace elements during extreme weathering of basalt in hainan island south china major trace and organic elements of a laterite profile developed on neogene basalts in northern hainan island south china were reported in this paper the aim of which was to investigate element mobilization and re distribution during extreme weathering the results indicate that most of the elements have been mobilized and transferred downwards along the profile by aqueous solution organic matter om can significantly improve the transport of insoluble elements among all the elements th is the least mobile as for the general conservative elements during incipient chemical weathering such as fe ti zr hf nb and ta the removals are up to 20 40 in the upper profile however these elements behave as conservatively as th in the lower profile in the middle profile oxic environment occurs accompanied with significant om decomposition the mn and ce transferred downward are readily oxidized into insoluble mn iv and ce iv and precipitate in the oxic front important om decomposition decreases the capacity of transfer of insoluble elements in aqueous solution consequently al significantly precipitates in the oxic front and rees with the exception of ce precipitate largely in the omdepleted layers co and u are also concentrated in the oxic front in association with mn and ce respectively however cr shows a negative correlation with mn because its response to redox condition changes is reversed from that of mn mn oxides hydroxides fe oxides hydroxides and secondary phosphate minerals other than clay minerals are potential hosts for rees except for ce in the profile rees with high concentrations in the profile seem closely associated with mn oxides hydroxides remarkable highly correlated ce and gd anomalies are observed in the profile ce anomalies are caused by ce precipitation in the oxic environment and successive decomposition of organic matter gd anomalies are likely to have resulted from lower stability constants of gd om complexes compared to those of neighboring rees the overall elemental behaviors in this profile suggest that organic matter plays a very important role in the mobilization and re distribution of the elements during extreme weathering

microplate model for the present day deformation of tibet 1 site velocities from 349 global positioning system gps stations are used to construct an 11 element quasi rigid block model of the tibetan plateau and its surroundings rigid rotations of five major blocks are well determined and average translation velocities of six smaller blocks can be constrained where data are well distributed the velocity field can be explained well by rigid block motion and fault slip across block boundaries residual misfits average 1 6 mm yr compared to typical one standard deviation velocity uncertainties of 1 3 mm yr any residual internal straining of the blocks is small and heterogeneous however residual substructure might well represent currently unresolved motions of smaller blocks although any smaller blocks must move at nearly the same rate as the larger blocks within which they lie undetected relative motions between them could be significant particularly where there are gaps in gps coverage predicted relative motions between major blocks agree with the observed sense of slip and along strike partitioning of motion across major faults however predicted slip rates across tibet s major strike slip faults are low only 5 12 mm yr a factor of 2 3 smaller than most rates estimated from fault offset features dated by radiometric methods as 2000 to 100 000 year old previous work has suggested that both gps data and low fault slip rates are incompatible with rigid block motions of tibet the results reported here overcome these objections

elemental mobilisation by sheet erosion affected by soil organic carbon and water fluxes along a radiotraced soil catena with two contrasting parent materials abstract sediment export rates are sensitive to different parent materials changes in land use human impact and climate but the landscape response to such changes is difficult to interpret and more knowledge of soil erosion hot spots is still needed special focus should be directed to examine the role of the erosional impact of water movement in mobilising stable elements in soils that become then available to be transferred in agroecosystems our main objective was to investigate the mobilisation and redistribution of 15 major and trace elements in the soil along a karstic hillslope in north eastern spain to this purpose we selected a representative soil catena with two distinctive sections based on the parent material in which the main soil properties and soil erosion patterns are very well characterised element contents were determined by icp oes and soil redistribution rates were obtained using 137cs for each of the 12 and 11 soil profiles sampled in the upper and lower sections respectively the elemental composition in soil profiles is related to their landscape features and the influence of soil properties and soil redistribution rates are explored in each section of the soil catena the distinctive physiographic characteristics of the slope distribution of land uses presence of linear landscape elements and the intrinsic soil properties namely soc hc and grain size affect runoff and determine the connectivity of eroded sediment thus affecting the geochemical dynamics the results of this investigation showed that the different processes governed by infiltration in the upper section versus runoff in the lower section affect elemental mobilisation along the soil catena and contribute to understanding processes of elemental transference in mediterranean agroecosystems

gps measurements of present day convergence across the nepal himalaya the high elevations of the himalaya and tibet result from the continuing collision between india and asia which started more than 60 million years ago1 4 from geological and seismic studies of the slip rate of faults in asia5 it is believed that approximately one third of the present day convergence rate between india and asia 58 4mmyr 1 is responsible for the shortening uplift and moderate seismicity of the himalaya great earthquakes also occur infrequently in this region releasing in minutes the elastic strain accumulated near the boundary zone over several centuries and accounting for most of the advance of the himalaya over the plains of india the recurrence time for these great earthquakes is determined by the rate of slip of india beneath tibet which has hitherto been estimated indirectly from global plate motions6 from the slip rates of faults in asia7 8 from seismic productivity9 and from the advance of sediments on the northern ganges plain10 here we report geodetic measurements using the global positioning system gps of the rate of contraction across the himalaya which we find to be 17 52 2 mm yr 1 from the form of the deformation field we estimate the rate of slip of india beneath tibet to be 20 5 2 mmyr 1 strain sufficient to drive one or more great himalayan earthquakes with slip similar to that accompanying the magnitude 8 1 bihar nepal 1934 earthquake may currently be available in western nepal

lake baikal record of continental climate response to orbital insolation during the past 5 million years the sedimentary record of biogenic silica from lake baikal in south central siberia suggests that this region of central asia was impacted by two major cooling episodes at 2 8 to 2 6 and 1 8 to 1 6 million years ago the spectral evolution of this continental interior site parallels the evolutionary frequency spectra for various marine oxygen isotope records in the baikal record the 41 000 year obliquity cycle is particularly strong from 1 8 to 0 8 million years ago variance in the 100 000 year eccentricity band increases during the past 0 8 million years the expected precession frequency of 23 000 years is highest during the past 400 000 years the modulation of the predicted 23 000 and 41 000 year insolation forcing by the 100 000 and 400 000 year eccentricity bands indicates that the transfer of variance from the precession and obliquity frequencies to the eccentricity part of the spectrum occurred in the eurasian continental interior as well as in tropical and high latitude ocean sites

lower edge of locked main himalayan thrust unzipped by the 2015 gorkha earthquake faults are unlocked by earthquakes analysis of seismic data from the 2015 nepal earthquake shows that only part of the main himalayan thrust fault was unzipped by the quake leaving much of the fault locked and ready to slip in a future event

stress change from the 2015 mw 7 8 gorkha earthquake and increased hazard in the southern tibetan plateau abstract we examine the co seismic coulomb stress change induced by the 2015 mw 7 8 gorkha nepal earthquake and investigate its influence on the seismic hazard in the southern tibetan plateau we find that the location of the aftershocks coincides with areas where stress was enhanced this stress enhanced area also covers the west and the shallow fault section updip of the 2015 gorkha earthquake rupture in the main himalayan thrust fault mht signaling the raising hazard of the seismic gaps in the west and south to kathmandu the 2015 gorkha earthquake strongly interacted particularly with the normal and thrust faults in the distance of around 100 250 km from the rupture zone by bringing stress closer to the coulomb failure this fault interaction process increased stress by 12 kpa and 100 kpa at the southern end of the tingkye and the nyalam normal faults respectively triggering the ms 5 9 tingri earhquake on 25 may 2015 and the ms 5 3 nyalam earthquake on 26 may 2015 stress in the main frontal himalaya thrust fault mft the main boundary thrust fault mbt in the lalitpur area of nepal was promoted by 40 100 kpa such stress transfer should facilitate the future rupture on these active faults and raise seismic hazard in the southern tibetan plateau

intraplate deformation of the indian subcontinent 1 while deformation at the earth s surface primarily occurs along tectonic plate boundaries major earthquakes have shaken regions deep within continental interiors three of the largest m 7 5 historic intraplate earthquakes occurred within the indian subcontinent suggesting the possibility of significant intraplate deformation we consider surface velocities determined from new gps data collected at 29 continuous gps stations and 41 survey mode gps stations in india between 1995 and 2007 to find a north south shortening rate of 0 3 0 05 nanostrain yr 1 which may be accommodated by 2 1 mm yr of more localized convergence across central india southward motions at 4 7 mm yr of sites on the shillong plateau in northeast india reflect rapid shortening and high earthquake hazard associated with active thrust faults bounding the plateau the width and magnitude of the elastic strain accumulation field across the himalaya varies little from 76 90 longitude but the strain is more broadly distributed and convergence rates are higher along the eastern 200 km of the range

holocene late pleistocene climatic ice core records from qinghai tibetan plateau three ice cores to bedrock from the dunde ice cap on the north central qinghai tibetan plateau of china provide a detailed record of holocene and wisconsin wurm late glacial stage lgs climate changes in the subtropics the records reveal that lgs conditions were apparently colder wetter and dustier than holocene conditions the lgs part of the cores is characterized by more negative 18 o ratios increased dust content decreased soluble aerosol concentrations and reduced ice crystal sizes than the holocene part these changes occurred rapidly 10 000 years ago in addition the last 60 years were apparently one of the warmest periods in the entire record equalling levels of the holocene maximum between 6000 and 8000 years ago

holocene environmental changes in bangong co basin western tibet part 2 the pollen record abstract a better knowledge of environmental variations in key regions such as the tibetan plateau which plays a fundamental role in the indian monsoon dynamics and thus on the whole northern hemisphere atmospheric circulation is of great importance we present here a detailed paleoenvironmental study based on pollen analyses of a sediment core from lake bangong results on the modern pollen rain are also discussed as they give valuable information for the interpretation of the fossil pollen data the pollen results of the bangong sequence and their paleoclimatic interpretation are integrated into a chronological framework on the basis of palynostratigraphical methods because of dead carbon in the lake system it has been difficult to establish a reliable chronology of the bangong sequence using a geochemical model for correcting measured 14c ages the pollen record from lake bangong compares well with the record from lake sumxi in western tibet lake bangong core provides a continuous holocene pollen record before 9600 yr b p the dominance of desertic elements in the pollen record reflects an arid environment at about 9600 yr b p an abrupt shift to steppe vegetation suggests the onset of moister conditions and from 9500 to 6200 yr b p proxy data indicate conditions warmer and wetter than today proxy data also indicate short term changes during this interval climate instability is suggested by the development of a local palustral flora which peaks at 7700 yr b p and is interpreted as a lake regression in phase with increase in the percentage of littoral and saline water diatom species between 8600 and 7700 yr b p the first humid pulse culminating at 9000 8500 yr b p is thus followed by drier conditions around 8000 7700 yr b p the interval between 7200 and 6500 yr b p regarded as optimal for vegetation growth from the pollen record corresponds to a second humid pulse a trend towards aridity is observed during the following period with dry events centered around 5500 3900 3200 and 700 yr b p

quaternary paleoenvironmental change on the tibetan plateau and adjacent areas western china and western mongolia abstract this paper summarises the nature of climatic change during the last glacial interglacial cycle on the tibetan plateau and adjacent areas the results are derived from inland glacier fluctuations lake level changes and dust loess records of central asia including tibet these are based on our field investigations from 1988 to 1998 and literature surveys the changing extents of different climatic controlled geomorphic landscapes and vegetation zones help to provide estimates of the magnitude of climatic change features such as ice wedge casts loess and palaeosols ela reconstruction s and palaeobotanical data are used to help reconstruct palaeoprecipitation and palaeotemperatures weathering characteristics the overlying strata and some luminescence dates indicate that there are two main glacial ice advances during the last glacial cycle these correspond to marine oxygen isotope stages ois 2 and 4 in some areas as the eastern or northern margin of the tibetan plateau remnants of older glaciations are preserved higher lake levels in the deserts of central asia and on the tibetan plateau are dated to 40 to 25 ka ois 3 and to late glacial early to mid holocene periods our work supports the view that in many areas of central asia cold phases during the last glacial correspond with the maximum extent of glaciers and the periglacial activity the last glaciation produced large alluvial fans alternating with periods of high lake stands on the tibetan plateau however at the northern margin of the plateau in the qaidam basin and in some particular desert areas in western china high lake levels occurred also during the pleistocene and are related with alluvial fans

effect of the formation of the isthmus of panama on atlantic ocean thermohaline circulation the late cenozoic closure of the seaway between the north andsouth american continents is thought to have caused extensive changes in ocean circulation and northern hemisphere climate1 2 but the timing and consequences of the emergence of the isthmus of panama which closed the seaway remain controversial1 2 3 4 5 here we present stable isotope and carbonate sand fraction records from caribbean sediments which when compared to atlantic and pacific palaeoceanographic records indicate that the closure caused a marked reorganization of ocean circulation starting 4 6 million years ago shallowing of the seaway intensified the gulf stream and introduced warm and saline water masses to high northern latitudes these changes strengthened deep water formation in the labrador sea over the next million years as indicated by an increased deep water ventilation and carbonate preservation in the caribbean sea and favoured early pliocene warming of the northern hemisphere the evaporative cooling of surface waters during north atlantic deep water formation would have introduced moisture to the northern hemisphere although the pronounced intensification of northern hemisphere glaciation between 3 1 and 2 5 million years ago substantially lagged the full development of north atlantic deep water formation we propose that the increased atmospheric moisture content was a necessary precondition for ice sheet growth which was then triggered by the incremental changes in the earth s orbital obliquity

inversion for rheological parameters from post seismic surface deformation associated with the 1960 valdivia earthquake chile summary data collected during two global positioning system campaigns in 1994 and 1996 across chile and western argentina 22 stations in the area where the m w 9 5 1960 may 22 valdivia earthquake took place shows ground motion velocities that cannot be fully explained by the elastic strain accumulation during the interseismic phase of an earthquake deformation cycle we use dislocation models to reproduce the observed velocities with a 3 d source in a medium with one elastic layer overlying a maxwell viscoelastic half space and a planar rupture surface with uniform coseismic slip the reason for avoiding a more detailed and elaborated model is that knowledge about the valdivia earthquake source parameters and the area where the event took place is poorly constrained we focus therefore on examining the first order postseismic deformation and ignore finer details about the heterogeneity of the earth by means of a grid search inversion over more than a million different models we derived the most likely values for some of the medium and source parameters involved in the deformation process namely viscosity thickness of the elastic layer d average slip on the rupture surface u 0 and the seismic coupling coefficient according to our study the optimum values are 10 20 pa s d 46 km u 0 15 m and 96 a clear difference is seen between the surface deformation caused by silent slip on the rupture surface and the one caused by postseismic relaxation processes two possibilities proposed to explain the anomalous velocities we find that the deformation associated with the 1960 valdivia event can still be observed after several decades and it is the most likely explanation for the velocity component that cannot be explained by plate convergence our model also predicts that this deformation will still be measurable for several more decades our model reproduces the first order pattern of the measured gps velocities showing good agreement with recent finite element studies with the advantage of simplicity and short computation time allowing the extensive search for the best fitting model

stable isotopes in bulk carbonates and organic matter in recent sediments of lake qinghai and their climatic implications abstract multi proxy indices on annual decadal scales during the past 600 years were developed from the surface sediments of lake qinghai based on 210pb and 137cs geochronology the 13ccarb 18ocarb and total carbonate content are consistent with one another in trends and their variations have been mainly ascribed to regional temperature it is suggested that the strong evaporation contributes in modifying 18o of lake water and 13c of the dissolved inorganic carbon of the surface water and appears to be responsible for the covariance between 13ccarb and 18ocarb photosynthesis of the aquatic plants appears to have played a significant role in determining 15n of organic matter the discrimination of 14n and 15n during photosynthesis may have triggered a positive linkage between temperatures and 15norg after removal of the stratigraphic trend variations of total organic carbon toc c n ratio and 13corg have been ascribed to local precipitation toc after removal of the stratigraphic trend is positively correlated with the c n ratio r 0 45

rupture model of mw 7 8 2015 gorkha nepal earthquake constraints from gps measurements of coseismic offsets abstract we estimate coseismic offsets at 20 sites in india due to the 25 april 2015 gorkha nepal mw 7 8 earthquake only four sites in the indian region immediately to the south of the rupture showed discernible coseismic horizontal offsets ranging between 3 and 7 mm toward north we invert these offsets along with 13 other offsets at gps sites in nepal and 33 offsets at sites in china for the estimation of slip distribution on the causative rupture we assume that rupture occurred on the main himalayan thrust mht in our estimated slip model high slip reaching 5 m occurred east of the mainshock epicenter and the slip on rupture terminated close to the main boundary thrust mbt thus the rupture for this earthquake remained blind increasing the potential for future earthquake in the shallow updip unruptured part of the mht

magnitude calibration of north indian earthquakes this article is concerned primarily with the evaluation of the size and location of northern indian and southern tibetan earthquakes during the last 200 yr it draws attention to the problems of assessing intensity of early and more recent earthquakes in a built environment which is different from that for which the intensity scale has been constructed and to the way in which isoseismals are drawn through a re evaluation of intensities and a reassessment of isoseismals a formula for the estimation of surface wave magnitude using isoseismal radii is derived this formula is used to estimate the surface wave magnitudes of 16 earthquakes that occurred in the region between 1803 and 1900 this study shows that it is possible to calculate accurate surface wave magnitudes for earthquakes that occurred before the advent of the scale and that there is no need to resort to empirical formulae for the assessment of the size and seismic moment release of pre 20th century earthquakes also derived are formulae for the conversion of ms to m0 in total locations surface wave magnitudes and m0 estimates are presented for 43 important events that occurred in the region between 1803 and 1974 eight of which were in the lower crust or were subcrustal we find that the m0 ms scaling for india yields smaller ms than the global relation and that the methodology used can help to evaluate more realistic slip rates as well as to address other issues related to earthquake hazard in northern india

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds

kinematics and strain rates of the eastern himalayan syntaxis from new gps campaigns in northeast india abstract newly acquired gps data along transects across himalaya in eastern himalayan syntaxis ehs reveal a clockwise rotation of rigid micro plate comprising part of brahmaputra valley ne himalaya and northern myanmar that rotates about a pole located at 14 5 n 100 8 e at an angular rate of 1 75 0 12 myr the ehs is being torn off from the main indian plate as a rigid block around which the kinematic clockwise rotation of tibetan gps sites toward the sichuan yunnan region occurs in the eurasia fixed frame the residual velocity field of the newly acquired data estimated after removing the rotation that minimizes the gps rates around ehs show a clear ne motion of the ehs sites indentation of the rigid indian plate into a less rigid area of the eurasian plate the most extensive ehs zones of compression and shortening are in the direction of indenter convergence with average values ranging between 50 100 nanostrain year along the frontal segment of ehs from nw to se the shortening rate is reduced from the local maximum value of 160 to 80 nanostrain year thus indicating a possibly locked fault patch of mishmi or lohit thrusts the southernmost part of segment activated during the large 1950 assam earthquake mw 8 6 an elastic block model was invoked to infer the average slip rates of sections around ehs and to estimate an average locking depth of 15 km the slip rate perpendicular to the locked sector of ehs reaches 32 4 mm year and permits to roughly infer a recurrence time of 200 year for an earthquake as energetic as the 1950 assam event