timing of the last interglacial in northern europe derived from optically stimulated luminescence osl dating of a terrestrial saalian eemian weichselian sedimentary sequence in ne germany abstract based on the results of palynological and geochemical analyses a sediment section near the village of vevais north eastern brandenburg is assumed to encompass a succession of saalian eemian and weichselian sediments and is expected to cover a time span from marine isotope stage mis 6 to mis 2 it is regarded as a key site for the study of the last interglacial cycle in north eastern germany palynological analyses had revealed an almost complete record of the eemian mis 5e preserved within a succession of lake marls exposed in the sediment sequence but results from numerical dating methods were still missing within this study five samples from sand layers within the profile have been analyzed using luminescence dating techniques in order to set up a geochronometrical time frame for the eemian interglacial first results from optically stimulated luminescence osl dating of quartz showed severe age underestimation of some samples with regard to their relative stratigraphical position to the eemian lake marls radionuclide analyses revealed disequilibria within the 238u decay chain and inconsistencies concerning the 40k content for most of the samples in order to overcome these dosimetric problems additional infrared stimulated luminescence irsl and post infrared yellow osl post ir yosl measurements from feldspar were conducted and a subtraction dating method was successfully applied hence it was for the first time possible to set up a time frame for the eemian interglacial inferred from luminescence dating techniques of a terrestrial sedimentary archive in north eastern germany the onset of the eemian was dated to 126 16 ka the termination and beginning transition from the eemian to the weichselian cold stage was dated to 108 9 7 8 ka these results are in excellent agreement with the marine isotope record as well as with the results of the analysis of the continuous varve record of lago grande di monticchio with a period of 17 7 0 2 ka from the onset at 127 2 1 6 ka bp for the eemian interglacial

litho1 0 an updated crust and lithospheric model of the earth we present the litho1 0 model which is a 1 tessellated model of the crust and uppermost mantle of the earth extending into the upper mantle to include the lithospheric lid and underlying asthenosphere the model is parameterized laterally by tessellated nodes and vertically as a series of geophysically identified layers such as water ice sediments crystalline crust lithospheric lid and asthenosphere litho1 0 is created by constructing an appropriate starting model and perturbing it to fit high resolution surface wave dispersion maps love and rayleigh group and phase over a wide frequency band 5 40 mhz we examine and discuss the model with respect to key lithospheric parameters such as average crustal velocity crustal thickness upper mantle velocity and lithospheric thickness we then compare the constructed model to those from a number of select studies at regional and global scales and find general consistency it appears that litho1 0 represents a reasonable starting model of the earth s shallow structure crust and uppermost mantle for the purposes in which these models are used such as traveltime tomography or in efforts to create a 3 d reference earth model the model matches surface wave dispersion over a frequency band wider than the band used in the inversion there are several avenues for improving the model in the future by including attenuation and anisotropy as well as making use of surface waves at higher frequency

extension during continental convergence with application to the tibetan plateau the tibetan plateau is the product of crustal thickening caused by the collision between india and asia and is the largest active example of extensional tectonics in a zone of continental collision throughout most of the tertiary the tectonics of the plateau were dominated by north south shortening a significant proportion of which took place on east west striking thrust faults for the last 5 m y or so the plateau has been thinning by the mechanism of extension on north south trending normal faults previous investigations of the collision have been able to account for the large scale features of the tertiary deformation but have failed to explain the transition in the late tertiary to quaternary strain rate field of the plateau from north south compression to east west extension the transition could in principle be effected by a reduction in the rate of convergence between india and asia or by a uniform reduction in strength of the whole continental lithosphere of asia it could not however be effected by a reduction in strength of the elevated region alone this produces increased compressional strain rates in the weakened zone an alternative explanation for the transition to extension comes from considering the thermal evolution of thickened continental lithosphere the lower part of the lithosphere consists of a thermal boundary layer which when thickened by horizontal shortening is colder and denser than its surroundings convective instability of the thickened thermal boundary layer and its replacement by hot asthenosphere would rapidly raise the surface elevation and gravitational potential energy of the overlying part of the lithosphere the convective instability would happen in a time brief compared with the collision time scale 50 m y in the case of india and asia but would only occur after there had already been substantial thickening of the lithosphere numerical experiments show that for a range of lithospheric parameters the increase in surface height as much as 2 km and of potential energy 5 to 10 1012 n m 1 resulting from convective instability of the lower lithosphere are sufficient for east west extension to replace north south compression as the dominant feature of the stress field of the tibetan plateau

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

paleoglaciation of the tibetan plateau and surrounding mountains based on exposure ages and ela depression estimates the tibetan plateau holds an ample record of past glaciations and there is an extensive set of glacial deposits dated by exposure dating here a compilation is presented of 10be exposure ages from 485 glacial deposits with 1855 individual samples on the tibetan plateau and ela depression estimates for the glacial deposits based on a simple toe to headwall ratio approach to recalculate the tibetan plateau exposure ages 10be production rates from 24 calibration sites across the world are compiled and recalibrated yielding an updated global reference 10be production rate the recalculated exposure ages from the tibetan plateau glacial deposits are then divided into three groups based on exposure age clustering to discriminate good well clustered from poor scattered deglaciation ages a major part of the glacial deposits have exposure ages affected by prior or incomplete exposure complicating exposure age interpretations the well clustered deglaciation ages are primarily from mountain ranges along the margins of the tibetan plateau with a main peak between 10 and 30 ka indicating glacial advances during the global lgm a large number of deglaciation ages older than 30 ka indicates maximum glaciation predating the lgm but the exposure age scatter generally prohibits accurate definition of the glacial chronology the ela depression estimates scatter significantly but the main part is remarkably low average ela depressions of 337 197 m for the lgm and 494 280 m for the pre lgm indicate restricted glacier expansion

surface deformation and lower crustal flow in eastern tibet field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern tibetan plateau since about 4 million years ago instead central eastern tibet has been nearly stationary relative to southeastern china southeastern tibet has rotated clockwise without major crustal shortening and the crust along portions of the eastern plateau margin has been extended modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle this model also predicts east west extension on the high plateau without convective removal of tibetan lithosphere and without eastward movement of the crust east of the plateau

evidence for mechanically coupled lithosphere in central asia and resulting implications the recent dramatic increase in seismic anisotropy and surface global positioning system gps data for central asia permits a comprehensive examination of the mantle s role in mountain building a joint analysis of 178 shear wave splitting and 2000 gps observations using a new technique reveals that the crust and lithospheric mantle deform coherently arguing for crust mantle mechanical coupling during deformation the observed spatial variations in anisotropy refl ect the large scale pattern of lithospheric deformation as well as a change in deformational style from simple shear on the tibetan plateau transitioning to pure shear in surrounding regions

a 10be production rate calibration for the arctic we present a baffin bay 10 be production rate calibration derived from glacial deposits in western greenland and baffin island and test our results against published 10 be calibration datasets to develop an arctic 10 be production rate our calibration comprises i 10 be measurements from moraine boulders linked to a 14 c dated moraine at jakobshavn isfjord in western greenland ii an independent and previously published 10 be production rate at jakobshavn isfjord and iii re measured 10 be concentrations from a baffin island calibration site that is included in the north eastern north america dataset combined we calculate a sea level high latitude 10 be production rate for the baffin bay region of 3 96 0 07 atoms g 1 a 1 lal stone scaling model after testing the baffin bay rate against calibration sites in norway and north eastern north america we calculate a more conservative arctic production rate of 3 96 0 15 atoms g 1 a 1 the baffin bay and arctic 10 be production rates are indistinguishable from the north eastern north america 10 be production rate 3 91 0 19 atoms g 1 a 1 and yield overall uncertainties of 2 3 7 1s these production rates reduce systematic uncertainties in 10 be based chronologies of ice margin change and allow 10 be based chronologies to be more confidently compared with high resolution climate records such as those from greenland ice cores copyright 2013 john wiley sons ltd

late glacial and holocene 10be production rates for western norway we present a new regional calibration of the 10be production rate from two well dated surfaces insouthern norway a rock avalanche with 14c dated wood and a precisely dated younger dryas moraine c

evidence from seismites for glacio isostatically induced crustal faulting in front of an advancing land ice mass rugen island sw baltic sea abstract it is hitherto commonly thought that earthquakes triggered by geologically rapid changes in the pressure caused by the fluctuating extent of thick land ice masses occur exclusively during ice retreat our study of deformed sediment layers within an undeformed glaciolacustrine and glaciofluvial succession exposed in a coastal cliff on rugen island south western baltic sea challenges this widespread idea based on their structural and deformational features the layers under investigation are interpreted as seismites which formed as a result of seismically induced liquefaction the stratigraphic context aided by optically stimulated luminescence osl dating indicate that the documented seismites must have formed shortly before the front of the pleistocene scandinavian ice sheet reached the study area during the last glacial maximum thus during a stage of ice advance this implies that the flexural isostatic response of the earth s crust as a consequence of the ice load during ice advance was accompanied by earthquakes probably due to local re activation of pre existing faults the crustal response to an increasing ice load was consequently less gradual than previous studies about glaciation related tectonics suggest

crustal structure of mainland china from deep seismic sounding data abstract since 1958 about ninety seismic refraction wide angle reflection profiles with a cumulative length of more than sixty thousand kilometers have been completed in mainland china we summarize the results in the form of 1 a new contour map of crustal thickness 2 fourteen representative crustal seismic velocity depth columns for various tectonic units and 3 a pn velocity map we found a north south trending belt with a strong lateral gradient in crustal thickness in central china this belt divides china into an eastern region with a crustal thickness of 30 45 km and a western region with a thickness of 45 75 km the crust in these two regions has experienced different evolutionary processes and currently lies within distinct tectonic stress fields our compilation finds that there is a high velocity 7 1 7 4 km s layer in the lower crust of the stable tarim basin and ordos plateau however in young orogenic belts including parts of eastern china the tianshan and the tibetan plateau this layer is often absent one exception is southern tibet where the presence of a high velocity layer is related to the northward injection of the cold indian plate this high velocity layer is absent in northern tibet in orogenic belts there usually is a low velocity layer lvl in the crust but in stable regions this layer seldom exists the pn velocities in eastern china generally range from 7 9 to 8 1 km s and tend to be isotropic pn velocities in western china are more variable ranging from 7 7 to 8 2 km s and may display azimuthal anisotropy

lithospheric structure of the southeastern margin of the tibetan plateau from rayleigh wave tomography lithospheric shear wave velocity beneath the southeastern margin of the tibetan plateau is obtained from rayleigh wave tomography using earthquake data recorded by the temporary chinarray and permanent china digital seismic array fundamental mode rayleigh wave phase velocities at periods of 20 100 s are determined and used to construct the 3 d shear wave velocity model low velocity anomalies appear along or close to the major faults in the middle crust and become a broad zone in the lower crust suggesting block extrusion in the shallow crust and diffuse deformation in the lower crust both of which play important roles in accommodating the collision between the indian and eurasian plates a vertical low velocity column beneath the tengchong volcano is observed which could be caused by upwelling of warm mantle due to the lithosphere extension in the thailand rift basin to the south or by fluid induced partial melting due to the subduction of the burma slab the western yangtze craton is characterized by low velocity in the crust and uppermost mantle above the fast mantle lithosphere indicating possible thermal erosion at the western craton edge resulted from the extrusion of the tibetan plateau a low velocity zone is imaged at the depths of 70 150 km beneath the eastern part of the yangtze craton which could be caused by small scale mantle convection associated with the subduction of the burma microplate and or the opening of the south china sea

two crustal flowing channels and volcanic magma migration underneath the se margin of the tibetan plateau as revealed by surface wave tomography abstract the se margin of the tibetan plateau is an important area to develop a better understanding of the plateau uplift and the indian eurasian continental collision dynamics previous studies have reported widespread low velocity anomalies beneath this region particularly in the tengchong volcanic field tcvf however the spatial distribution and dynamic processes of these low velocity anomalies are not well constrained in this study a 3 d s wave velocity structure model of the crust and upper mantle 10 120 km in the region is constructed by the inversion of surface wave dispersion data a two step inversion procedure is adopted to generate the s wave velocity structure images the measured phase velocities and inverted s wave velocities jointly show a large scale low velocity anomaly distributed in the crust consistent with the view that the region is the passageway of the eastward migration of tibetan plateau material two crustal flowing channels are clearly observed at depths of 20 km and 30 km which connect and rotate clockwise around the eastern himalaya syntaxis beneath the tcvf there are two prominent low velocity anomaly zones at depths of 15 25 km and 50 80 km which indicate the existence of magma chambers one of the crustal flowing channels is connected with the magma chamber of the tcvf and the other has a short branch north of kunming toward the mile shizong fault at a depth of 20 km based on the distribution of the s wave velocities under the tcvf a dynamic model of the tengchong volcano magma system is proposed to explain the migration patterns of the volcanic material

complex structure beneath the southeastern tibetan plateau from teleseismic p wave tomography abstract a high resolution image of the deep structures in the southeastern tibetan plateau and yangtze block was revealed by teleseismic inversion based on the dense teleseismic data collected from the permanent seismic stations and a recently deployed temporary seismic array the results show that low velocity anomaly is imaged mainly in the eastern and southeastern tibetan plateau except the southern panzhihua area above 200 km depth in the upper mantle whereas a high velocity anomaly exists to its east especially beneath the sichuan basin we infer the cold crustal and upper mantle of the sichuan basin prevents the extrusion of mantle materials of the tibetan plateau while the cold lithosphere of the western yangtze block is eroded by the upper mantle materials with high temperature from the extrusion of the tibetan plateau under the tengchong volcanic region a low velocity anomaly extends to 300 km depth a high velocity anomaly is shown beneath the region from the southern sichuan to yunnan in the mantle transition zone and the anomaly reaches deeper to the lower mantle in the western yunnan area the widespread low velocity above the high velocity in the yunnan region indicates the dehydration of the indian plate may occur in the mantle transition zone which causes fast rising heat and lower melting temperature in the upper mantle a small scale high velocity anomaly in the southern panzhihua region is probably related to the late paleozoic mantle plume activity it plays an important role in impeding the southward extrusion of the plateau materials which might be one of the causes for the rapid change of the polarization direction of the fast shear waves around the area

three dimensional p wave azimuthal anisotropy in the lithosphere beneath china seismic anisotropy in the upper mantle beneath east asia has been studied extensively using shear wave sks splitting measurements which have provided important information on mantle dynamics in this region however sks measurements have poor vertical resolution and so their interpretations are usually not unique in this work we use a large number of traveltime data from 34 036 local earthquakes recorded by 1563 seismic stations to determine the first model of 3 d p wave azimuthal anisotropy in the lithosphere beneath china our results show that the fast velocity directions fvds are generally correlated with the surface geologic features such as the strikes of the orogens active faults and tectonic boundaries the fvds in the upper crust are normal to the maximal horizontal stress h in regions with extensive compression such as the tibetan plateau whereas they are subparallel to h in strike slip shear zones such as the western and eastern himalayan syntax the comparison of the fvds of p wave anisotropy with sks splitting measurements indicates that beneath the tibetan plateau the seismic anisotropy in the lithosphere contributes significantly to the sks splitting observations in contrast in east china the p wave fvds in the lithosphere are different from the sks splitting measurements suggesting that the sks splitting is mainly caused by the anisotropy in the deeper mantle such as the asthenosphere and the mantle transition zone under east china these novel results provide important new information on the lithospheric deformation and mantle dynamics in east asia

optically stimulated luminescence dating of sediments over the past 200 000 years optical dating of sediment using optically stimulated luminescence has become important for studying earth surface processes and this technique continues to develop rapidly a group of closely linked luminescence methods can be used to estimate the time since grains of quartz and feldspar were last exposed to daylight by detecting their subsequent response to environmental ionizing radiation exposure the technique is well suited to the dating of deposits as young as one year to several hundred thousand years recent technical developments have established a dating protocol with improved precision a high degree of reliability and an in built means to detect incomplete signal removal during deposition this approach has been extended to age estimation for single grains opening up a wider range of potential environments and new possibilities for understanding postdepositional grain movement ongoing research offers the possibility of significant age range extension and novel applications including low t

quaternary glaciations of northern europe this paper presents the outcome of a workshop held in berlin in february 2009 concerned with current research on the glacial history of northern europe including the british isles the methodologies presently used to resolve this topic are outlined particular attention is given to new analytical methods deriving from high resolution remote imaging of glacial terrain both on land and on the sea bed key new stratigraphic sections higher resolution results from conventional geochronological methods like radiocarbon and more recently developed technologies such as luminescence and cosmogenic radionuclide dating the relationships between the results derived from these two methods are discussed in further detail along with possible explanations for these differences an outline of a most likely glacial history of the scandinavian and british and irish ice sheets is presented along with possible links to global climate change as represented by the marine isotope mis record tentative evidence for glaciation is identified in mis 22 16 12 10 8 6 4 and 2 and correlations of phases within the last glaciation are also explored for both the scandinavian and british and irish ice sheets the results show that the character and extent of glaciation in different parts of the region are not synchronous and much more geochronological work is required before regional correlations can be established with confidence

role of in situ cosmogenic nuclides 10be and 26al in the study of diverse geomorphic processes the central premises of applications of the in situ cosmogenic dating method for studying specific problems in geomorphology are outlined for simple and complex exposure settings in the light of these general models we discuss the information that can be derived about geomorphic processes utilizing concentrations of in situ produced cosmogenic radionuclides 10be half life 1 5 ma and 26a1 half life 0 7 ma in a variety of geomorphic contexts glacial polish and tills meteorite impact craters alluvial fans paleo beach ridges marine terraces sand dunes and bedrock slopes we also compare 10be 26al data with results obtained by other dating methods we conclude that the technique of measuring in situ cosmic ray produced nuclides holds promise for quantitative studies of processes and time scales in a wide range of geomorphological problems

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

the boundary between the indian and asian tectonic plates below tibet the fate of the colliding indian and asian tectonic plates below the tibetan high plateau may be visualized by in addition to seismic tomography mapping the deep seismic discontinuities like the crust mantle boundary moho the lithosphere asthenosphere boundary lab or the discontinuities at 410 and 660 km depth we herein present observations of seismic discontinuities with the p and s receiver function techniques beneath central and western tibet along two new profiles and discuss the results in connection with results from earlier profiles which did observe the lab the lab of the indian and asian plates is well imaged by several profiles and suggests a changing mode of india asia collision in the east west direction from eastern himalayan syntaxis to the western edge of the tarim basin the indian lithosphere is underthrusting tibet at an increasingly shallower angle and reaching progressively further to the north a particular lithospheric region was formed in northern and eastern tibet as a crush zone between the two colliding plates the existence of which is marked by high temperature low mantle seismic wavespeed correlating with late arriving signals from the 410 discontinuity poor sn propagation east and southeast oriented global positioning system displacements and strikingly larger seismic sks anisotropy

from morphostratigraphy to geochronology on the dating of ice marginal positions abstract this study focuses on the glacial landscape of northern germany as a part of the southwestern sector of the scandinavian ice sheet sis as it has a research history reaching back about 130 years since the glacial theory replaced the drift theory in the late 19th century it has experienced a number of key changes including the introduction of the concept of polyglaciation or the differentiation of ice advances within one glaciation which is closely linked to the morphostratigraphical definition of ice marginal positions with the development of numerical dating methods the rather static morphostratigraphically based chronologies which are deeply rooted in research history have been confronted with a growing number of geochronometrical data obtained from glacigenic deposits in order to date ice marginal positions the two most commonly used dating methods for that purpose are optically stimulated luminescence osl and surface exposure dating of erratic boulders this study highlights the dependency of the significance of results from different dating methods on the sampling position within the geomorphological framework results from osl and surface exposure dating for the same ice marginal position in theory cannot be the same as the methods date different processes in the development of the glacial landscape osl dating of fluvioglacial sandur sediments dating the process of active sedimentation at the ice front and surface exposure dating of boulders on end moraines dating the process of stabilisation of end moraines after the retreat of the ice front often qualify as the most useful combination of techniques in order to define a time interval for the formation of the landforms at a specific ice marginal position methodological drawbacks which might occur unfortunately tend to widen the process induced offset between osl and surface exposure ages incomplete bleaching of fluvioglacial sediments might cause an offset towards a maximum osl age for an ice marginal position whereas delayed stabilisation or post exposure relocation of boulders might cause a shift towards a minimum age of key importance are the influence of periglacial processes and the effects of melting of buried ice on landform stabilisation which remain to be quantified a possible solution to this problem combining osl and surface exposure dating is suggested in this study nevertheless the possibility exists to date different geomorphological processes by applying different dating methods to glacigenic deposits this allows for a differentiated reflection of morphostratigraphically based chronologies against the background of the modern concept of dynamic ice sheets in contrast to the traditional morphostratigraphical definition of ice marginal positions a time based definition is proposed because it offers the possibility of a more detailed reconstruction of ice sheet dynamics at a certain point in time

introduction to tectonics of china abstract the continental crust of china is a mosaic of cratonic blocks and orogenic belts containing small cratons and terranes with various tectonic settings they have diverse origins and complex histories of amalgamation and often suffered repeated reworking after multiple episodes of amalgamation in the last three decades extensive geological geochemical and geophysical investigations have been carried out on these cratonic blocks and intervening orogenic belts producing an abundant amount of new data and competing interpretations this provides important insights into understanding the formation and evolution of the chinese continents the papers assembled in this volume present a timely and comprehensive overview on major advancements and controversial issues related to the formation and evolution of continental crust in china complex tectonic histories were experienced not only by the large scale cratonic blocks and orogenic belts but also by small scale terranes and orogens between and inside these blocks nevertheless our understanding of lithotectonic units and geological processes has been greatly advanced by recent studies of zirconology and geochemistry for various rock types from major petrotectonic units in china it has been further advanced from integrated interpretations of geochemical and petrological data for petrogenesis of magmatic rocks an overview of these observations and interpretations provides new insights into understanding the continental plate tectonics and the chemical geodynamics of subduction zones

east asia mantle tomography new insight into plate subduction and intraplate volcanism abstract we present a new p wave tomographic model beneath east asia by inverting 1 401 797 arrival time data recorded by the regional seismic networks in east asia and temporary seismic arrays deployed on the tibetan plateau our high resolution tomography shows that the subducted pacific slab is revealed clearly as a high velocity high v zone and it becomes stagnant in the mantle transition zone beneath eastern china prominent high v anomalies atop the 410 km discontinuity are detected beneath the eastern north china craton and northeast china suggesting that lithospheric delamination may have occurred and greatly affected the thermal state intraplate magmatism and surface topography of this region the indian lithosphere is characterized by a high v anomaly and it is subducting nearly horizontally beneath the entire or most parts of western tibet and with a small dipping angle to the southernmost part of eastern tibet the intraplate magmatism in different parts of east asia has different origins the active tengchong volcano is underlain by a prominent low velocity low v anomaly in the shallow mantle which may be caused by the subduction and dehydration of the burma microplate plate or indian plate the hainan volcano is underlain by a plume like low v anomaly that extends down to at least 1000 km depth and seems to be related to the deep subductions of the burma microplate or indian plate in the west and the philippine sea plate in the east prominent low v anomalies are detected beneath the changbai longgang and xianjindao volcanoes in northeast asia which may be related to the rollback of the subducting pacific slab as well as the convective circulation process in the big mantle wedge above the stagnant slab the origin of the wudalianchi volcano in northeast china seems associated with the upwelling of asthenospheric materials caused by the subduction induced lithospheric delamination

deep structure and seismogenesis of the north south seismic zone in southwest china 1 to understand the deep structure and seismogenesis in the north south seismic zone nssz in southwest china we collected a large number of p and s wave arrival time data from both local earthquakes and teleseismic events to invert simultaneously for the three dimensional p and s wave velocity vp vs structures in the crust and upper mantle the obtained vp and vs models are generally coherent with each other from the crust to the mantle transition zone the nssz is characterized by strong structural heterogeneities from the mountainous areas of southeastern tibet to the yangtze platform low vp and low vs anomalies are generally imaged in the upper crust under the sichuan basin showing good agreement with the surface geological features that the foreland basin contains primarily mesozoic and paleozoic sedimentary rocks with a thickness of several kilometers the deep part of the yangtze platform is characterized by a cratonic lithospheric body dipping southwestward down to 400 km depth beneath the southeastern margin of the tibetan plateau in sharp contrast to low velocity anomalies in the upper mantle beneath the songpan ganzi fold system and the northwest qiangtang block at depths of the lower crust and uppermost mantle a layer with low vp and low vs 1 2 is revealed under a region west of the yangtze platform which may reflect the ductile flow in the lower crust our results indicate that the seismotectonics in the nssz is affected significantly by the ductile flow in the lower crust and strong heterogeneities in the upper mantle under southwest china in addition to the dominant role of the india asia collision

seismic anisotropy in eastern tibet from shear wave splitting reveals changes in lithospheric deformation abstract knowledge about seismic anisotropy can provide important insight into the deformation of the crust and upper mantle beneath tectonically active regions here we focus on the southeastern part of the tibetan plateau in sichuan and yunnan provinces sw china we measured shear wave splitting of core refracted phases sks and skks at a temporary array of 25 iris passcal stations we calculated splitting parameters using a multi channel and a single record cross correlation method multiple layers of anisotropy cannot be ruled out but are not required by the data a fresnel zone analysis suggests that the shallow mantle between 60 and 160 km depth is the most likely source of anisotropy the polarization directions reveal a pronounced transition from primarily north south in the north sichuan to mostly east west orientations in the south yunnan in the southern part of the study region that is south of 26 n the fast polarization directions do not correlate well with known surface features and geodetic estimates of the crustal displacement fields whereas gps campaigns provide evidence suggesting north south crustal flow across the red river fault the pattern of anisotropy argues against such flow in the upper mantle these observations support models that allow differential movement of upper crust relative to lithospheric mantle in the northern part of the study region the relationships are more ambiguous and coherent deformation of the crust and mantle lithosphere cannot be excluded the interpretation of the shear wave splitting results is non unique but we suggest that the observed n s transition reflects a fundamental change in deformation regime across our study region it may be related to lateral variations in lithospheric rheology or may mark a transition from the direct impact of the continental collision to dominance of the far field strain field associated with regional subduction processes understanding the nature of the lateral change in deformation regime may prove critical for our understanding the geotectonic evolution of eastern tibet

love wave phase velocity models of the southeastern margin of tibetan plateau from a dense seismic array abstract love wave dispersion maps across the southeastern margin of the tibetan plateau are obtained using earthquake data recorded by the temporary chinarray and permanent china digital seismic array fundamental mode love wave phase velocity curves are measured by inverting love wave amplitude and phase with the two plane wave method the phase velocity maps with resolution better than 150 km are presented at periods of 20 100 s which is unprecedented in the study area the maps agree well with each other and show clear correlations with major tectonic structures the love wave phase velocity could provide new information about structures in the crust and upper mantle beneath the southeast margin of tibetan plateau like the radial anisotropy

accuracy of cosmogenic ages for moraines analyses of all published cosmogenic exposure ages for moraine boulders show an average age range of 38 between the oldest and youngest boulders from each moraine this range conflicts with the common assumption that ages of surface boulders are the same as the age of the landform the wide spread in boulder ages is caused by erosion of the moraine surface and consequent exhumation of fresh boulders a diffusion model of surface degradation explains the age range and shows that a randomly sampled small set of boulders n 3 7 will always yield a lower age limit for the moraine the model indicates that for identical dating accuracy six to seven boulders are needed from old and tall moraines 40 000 100 000 yr 50 100 m initial height but only one to four boulders from small moraines 20 000 100 000 yr 10 20 m by following these guidelines the oldest obtained boulder age will be 90 of the moraine age 95 probability this result is only weakly sensitive to a broad range of soil erosion rates our analysis of published boulder ages indicates that 3 of all moraine boulders have prior exposure and 85 of these boulders predate the dated moraine

mantle dynamics of western pacific and east asia insight from seismic tomography and mineral physics abstract recent results of high resolution seismic tomography and mineral physics experiments are used to study mantle dynamics of western pacific and east asia the most important processes in subduction zones are the shallow and deep slab dehydration and the convective circulation corner flow processes in the mantle wedge the combination of the two processes may have caused the back arc spreading in the lau basin affected the morphology of the subducting philippine sea slab and its seismicity under southwest japan and contributed to the formation of the continental rift system and intraplate volcanism in northeast asia which are clearly visible in our tomographic images slow anomalies are also found in the mantle under the subducting pacific slab which may represent a small mantle plumes b upwellings associated with the slab collapsing down to the lower mantle or c sub slab dehydration associated with deep earthquakes caused by the reactivation of large faults preserved in the slab combining tomographic images and earthquake hypocenters with phase diagrams in the systems of peridotite water we proposed a petrologic model for arc volcanism arc magmas are caused by the dehydration reactions of hydrated slab peridotite that supply water rich fluids to the mantle wedge and cause partial melting of the convecting mantle wedge a large amount of fluids can be released from hydrated morb at depths shallower than 55 km which move upwards to hydrate the wedge corner under the fore arc and never drag down to the deeper mantle along the slab surface slab dehydration reactions at 120 km depth are the antigorite related 5 reactions which supply water rich fluids for forming the volcanic front phase a and mg surssasite breakdown reactions at 200 and 300 km depths below 700 c cause the second and third arcs respectively moreover the dehydration reactions of super hydrous phase b phases d and e at 500 660 km depths cause the fluid transportation to the mantle boundary layer mbl 410 660 km depth the stagnant slabs extend from japan to beijing china for over 1000 km long indicating that the arc trench system covers the entire region from the japan trench to east asia we propose a big mantle wedge bmw model herein where hydrous plumes originating from 410 km depth cause a series of intra continental hot regions fluids derived from mbl accumulated by the double sided subduction zones rather than the india asia collision and the subsequent indentation into asia are the major cause for the active tectonics and mantle dynamics in this broad region

new insights into crustal and mantle flow beneath the red river fault zone and adjacent areas on the southern margin of the tibetan plateau revealed by a 3 d magnetotelluric study

too young or too old evaluating cosmogenic exposure dating based on an analysis of compiled boulder exposure ages cosmogenic exposure dating has greatly enhanced our ability to define glacial chronologies spanning several global cold periods and glacial boulder exposure ages are now routinely used to constrai

electrical resistivity structure of the xiaojiang strike slip fault system sw china and its tectonic implications abstract it is widely accepted that large scale strike slip faults play an important role in accommodating the india eurasia convergence but the relationships between surface displacements and deep deformation along the faults remain largely uncertain to address this issue new magnetotelluric mt images were obtained along two profiles across the xiaojiang strike slip fault system xjfs one of the most tectonically active areas in southwest china although different in details these two profiles show similar overall crustal structures the upper crust is generally resistive but separated by several narrow subvertical conductors that broadly coincide with the surface traces of the xjfs these fault zone conductors fzcs are interpreted to represent fault damage zones that formed by strike slip faulting shearing along the faults and filled with deeply sourced magmatic and or metamorphic fluids the lower crust is broadly characterized by enhanced conductivity and likely associated with partial melting at high temperatures these observations are consistent with other geophysical measurements in this area and in favor of the development of ductile flow along the xjfs although the pattern of flow is more complex than previously suggested based on these observations we propose that active deformation along the xjfs can be better described in the brittle upper crust by strike slip motion along the fluid weakened faults and by shear enhanced ductile flow in the partially molten lower crust these two mechanisms are not mutually exclusive but rather can be complementary to each other

high resolution mantle tomography of china and surrounding regions 1 a high resolution p wave tomographic model of the crust and mantle down to 1100 km depth under china and surrounding regions is determined by using about one million arrival times of p pp pp and pcp waves from 19 361 earthquakes recorded by 1012 seismic stations the subducting pacific slab is imaged clearly as a high velocity zone from the oceanic trenches down to about 600 km depth and intermediate depth and deep earthquakes are located within the slab the pacific slab becomes stagnant in the mantle transition zone under east china the western edge of the stagnant slab is roughly coincident with a surface topographic boundary in east china the active changbai and wudalianchi intraplate volcanoes in northeast china are underlain by significant slow anomalies in the upper mantle above the stagnant pacific slab these results suggest that the active intraplate volcanoes in ne china are not hot spots but a kind of back arc volcano associated with the deep subduction of the pacific slab and its stagnancy in the transition zone under the mariana arc however the pacific slab penetrates directly down to the lower mantle the active tengchong volcano in southwest china is related to the eastward subduction of the burma microplate the subducting indian and philippine sea plates are also imaged clearly the indian plate has subducted down to 200 300 km depth under the tibetan plateau with a horizontal moving distance of about 500 km high velocity anomalies are revealed in the upper mantle under the tarim basin ordos and sichuan basin which are three stable blocks in china

destruction of lithosphere within the north china craton inferred from surface wave tomography 1 the north china craton ncc is one of the oldest cratons in the world however the lithosphere of the craton was destructed during phanerozoic tectonism and then became tectonically and seismically active because the lithospheric structure of this complex craton has not been well studied the mechanism behind the thinning transformation and destruction of the lithosphere remains debated using an efficient and scalable 3 d surface wave tomography method we obtain a high resolution regional s wave velocity model that shows the three dimensional lithospheric structure of the ncc in addition we convert the s wave structure to an estimated thermal structure using accepted relationships between s wave velocity and temperature the model images a large upper mantle low velocity body beneath the eastern ncc especially beneath the seismically active zone from tangshan to xingtai this body is interpreted to represent hot material or volatiles escaping from the slab edge in the transition zone between the upper and lower mantle the low velocity body is a key piece of evidence in demonstrating thermochemical bottom up erosion transformation of the overlying cratonic lithosphere thereby leading to destruction of the lithosphere which may have occurred during the cenozoic this erosion mechanism appears to have had less influence in the western ncc ordos block however our results reveal a 130 km thick lithosphere beneath the present cratonic ordos block which is thinner than the 200 km thickness of the ncc lithosphere during the paleozoic as determined from analyses of xenoliths

climatic and morphological controls on diachronous postglacial lake and river valley evolution in the area of last glaciation northern poland abstract the wda river valley in northern poland is a polygenetic valley located in a former subglacial meltwater channel that after ice sheet retreat hosted separate and then interconnected lake basins subsequently replaced by a river in one part of the river system an abandoned lateglacial valley is found this dry valley is a unique feature in the area located within the limit of the scandinavian ice sheet during the last glaciation in the central european lowland we investigated lacustrine and fluvial sediments and landforms in the valley and applied palynological analysis combined with radiocarbon dating to reconstruct the valley evolution from the early period of river inception in the lateglacial through the formation of lakes during the pleistocene holocene transition up to the establishment of a modern river system in the early holocene three coeval processes were identified 1 formation of lake basins in the subglacial channel connected by a river 2 erosion of the river bed between the lakes and 3 sediment deposition at the mouths of the channels in the lake basins first generating delta fans and eventually filling the lakes entirely the valley formation was associated with diachronous melting of dead ice blocks buried in the subglacial channel controlled by the capacity of the hydrological system to evacuate the meltwater most of the lake basins in the study area were formed during the bolling allerod period but one section of the subglacial channel not affected by thermokarst processes survived protected by dead ice blocks throughout the entire lateglacial accelerated dead ice decay at the beginning of the holocene triggered widespread lowering of the base level which caused lake disappearance and the formation of the modern river system the processes reconstructed in the central section of the wda river indicate a highly dynamic and diachronous river valley development during the lateglacial and early holocene whereby the valley formation was interwoven with the formation of lake basins within the valley triggered by melting of dead ice blocks in the substratum

shear wave splitting in the southern margin of the ordos block north china 1 the southern margin of the ordos block in north china marks the transition from a stable cratonic block to active transextensional deformation in the weihe graben driven by the northeastward expansion of the tibet plateau we deployed 29 portable digital stations across this boundary and studied the upper mantle anisotropy using sks splitting the anisotropy is weak t 0 5 s at stations within the ordos block and in the north weihe graben but strong t 1 23 0 39 s in the south weihe graben and qinling orogen further south the directions of the fast s wave are 98 7 subparallel to the orientations of surface structures and the gps site velocities relative to stable asian continent we suggest that this e w oriented anisotropy is the result of both the collision between the north and south china blocks in the mesozoic and the eastward upper mantle flow driven by the indo asian collision

subduction of the indian lithosphere beneath the tibetan plateau and burma abstract subduction of the indian lithosphere under eurasia plays an important role in the tectonic evolution of the tibetan plateau and surrounding regions to improve our knowledge of pertinent mantle structures through tomographic imaging we combine p wave arrival time data from temporary arrays in tibet and stations of the chinese seismograph network with reprocessed data from the international seismological centre the new images reveal considerable spatial variations in mantle structure along the collision zone and the horizontal distance over which presumed continental indian lithosphere slides northward beneath the plateau decreases from west where it underlies the himalayas and the entire plateau to east where no indication is found for present day underthrusting beyond the himalayan block and indus tsangpo suture p wavespeed appears low in the shallow mantle beneath much of central and eastern tibet these observations suggest that indian lithosphere underlies only the southwestern part of the plateau and that the central and northeastern part is underlain by lithosphere of asian origin the continental parts of the indian plate that currently underthrust or subduct below the plateau appear generally detached from the oceanic slab fragments that subducted longer ago and that have been detected deeper in the mantle except perhaps in the central part of the collision zone 80 90 e this suggests that ongoing india eurasia collision must increasingly be driven by other forces such as subduction of the indian plate further west and east e g beneath indochina our images reveal structures associated with eastward subduction along the burmese arc southeast of the eastern himalayan syntaxis the tengchong volcanic complex in southwest china is marked by slow wave propagation to 150 km depth suggesting a causal link to subduction along the burmese arc the low velocities beneath the red river fault region extend to greater depth and may be related to upper mantle processes further southeast

mantle structure and dynamics beneath se tibet revealed by new seismic images abstract the structure and dynamics in se tibet are the key to understand the tectonic evolution of the tibetan plateau in this study we determined high resolution p wave seismic images in the upper mantle and transition zone in se tibet by jointly inverting the travel time residuals of local events and the relative travel time residuals of teleseismic events recorded by very dense seismic stations we revealed a high velocity body in the upper mantle beneath south china that represents the root of the yangtze craton the high velocity body extends in the entire yangtze craton at 300 450 km depths but it is constrained just beneath the sichuan basin and surrounded by extensive low velocity zones to the southwest at 65 250 km depths we propose that the yangtze craton is destructed laterally by the mantle flow extruded from the tibetan plateau we obtain a low velocity column in the upper mantle under the tengchong volcano as well as the visible high velocity bodies in the upper mantle and transition zone below the low velocity column the images suggest that the tengchong volcano is closely related to the subduction of the burma plate and caused by the dehydration of the subducted slab the present study reveals unprecedented details of the mantle structures beneath se tibet and provides new insights into the geodynamics of the tibetan plateau and its interaction with the stable yangtze craton

deglaciation of fennoscandia abstract to provide a new reconstruction of the deglaciation of the fennoscandian ice sheet in the form of calendar year time slices which are particularly useful for ice sheet modelling we have compiled and synthesized published geomorphological data for eskers ice marginal formations lineations marginal meltwater channels striae ice dammed lakes and geochronological data from radiocarbon varve optically stimulated luminescence and cosmogenic nuclide dating this is summarized as a deglaciation map of the fennoscandian ice sheet with isochrons marking every 1000 years between 22 and 13 cal kyr bp and every hundred years between 11 6 and final ice decay after 9 7 cal kyr bp deglaciation patterns vary across the fennoscandian ice sheet domain reflecting differences in climatic and geomorphic settings as well as ice sheet basal thermal conditions and terrestrial versus marine margins for example the ice sheet margin in the high precipitation coastal setting of the western sector responded sensitively to climatic variations leaving a detailed record of prominent moraines and other ice marginal deposits in many fjords and coastal valleys retreat rates across the southern sector differed between slow retreat of the terrestrial margin in western and southern sweden and rapid retreat of the calving ice margin in the baltic basin our reconstruction is consistent with much of the published research however the synthesis of a large amount of existing and new data support refined reconstructions in some areas for example the lgm extent of the ice sheet in northwestern russia was located far east and it occurred at a later time than the rest of the ice sheet at around 17 15 cal kyr bp we also propose a slightly different chronology of moraine formation over southern sweden based on improved correlations of moraine segments using new lidar data and tying the timing of moraine formation to greenland ice core cold stages retreat rates vary by as much as an order of magnitude in different sectors of the ice sheet with the lowest rates on the high elevation and maritime norwegian margin retreat rates compared to the climatic information provided by the greenland ice core record show a general correspondence between retreat rate and climatic forcing although a close match between retreat rate and climate is unlikely because of other controls such as topography and marine versus terrestrial margins overall the time slice reconstructions of fennoscandian ice sheet deglaciation from 22 to 9 7 cal kyr bp provide an important dataset for understanding the contexts that underpin spatial and temporal patterns in retreat of the fennoscandian ice sheet and are an important resource for testing and refining ice sheet models

lithospheric structure and its relationship to seismic and volcanic activity in southwest china 1 the sichuan yunnan region in southwest china is located in the boundary area between the active tibetan plateau to the west and the stable south china platform to the east this region is characterized by complex cenozoic structures and active seismotectonics in this study we have used over 30 000 arrival times from 1315 local earthquakes recorded by 172 seismic stations to determine a detailed three dimensional 3 d p wave velocity structure of the lithosphere down to 85 km depth in this region we have taken into account the complex morphology of the moho discontinuity to conduct the tomographic inversions which leads to a better result than that with a flat moho as in the previous studies our results show that large velocity variations of up to 7 exist in the crust and upper mantle in the sichuan yunnan region the velocity image of the upper crust correlates with the surface geological features the sichuan basin is imaged as a prominent low velocity zone while the panzhihua mining district is imaged as a high velocity feature velocity changes are visible across some of the large fault zones and the faults and some large crustal earthquakes seem to occur at the boundary areas between slow and fast velocity anomalies some of the faults such as the red river fault may have cut through the crust and reached up to the upper mantle under the tengchong volcanic area strong low velocity zones are visible down to 85 km depth with a lateral extent of about 100 km suggesting the existence of magma chambers under the volcano it is unclear how the tengchong intraplate volcanism was generated it may be related to the collision processes between the indian plate burma microplate and the eurasian plate and the possible subduction of the burma microplate under the eurasian plate another possibility is that it was caused by the extensional fractures of the lithosphere and the upward intrusion of the hot asthenospheric materials it is also possible that the tengchong volcanism represents a hot spot with a lower mantle origin

oblique stepwise rise and growth of the tibet plateau two end member models of how the high elevations in tibet formed are i continuous thickening and widespread viscous flow of the crust and mantle of the entire plateau and ii time dependent localized shear between coherent lithospheric blocks recent studies of cenozoic deformation magmatism and seismic structure lend support to the latter since india collided with asia 55 million years ago the rise of the high tibetan plateau likely occurred in three main steps by successive growth and uplift of 300 to 500 kilometer wide crustal thrust wedges the crust thickened while the mantle decoupled beneath gently dipping shear zones did not sediment infilling bathtub like of dammed intermontane basins formed flat high plains at each step the existence of magmatic belts younging northward implies that slabs of asian mantle subducted one after another under ranges north of the himalayas subduction was oblique and accompanied by extrusion along the left lateral strike slip faults that slice tibet s east side these mechanisms akin to plate tectonics hidden by thickening crust with slip partitioning account for the dominant growth of the tibet plateau toward the east and northeast

structural model of the lithosphere asthenosphere system beneath the qinghai tibet plateau and its adjacent areas abstract the deep structure of the lithosphere asthenosphere system as imaged from geophysical data of the qinghai tibet plateau the highest on the earth provides important clues in understanding its orogenic processes here we reconstruct the main features of the structure of the crust and upper mantle from surface wave tomography in the qinghai tibet plateau and its adjacent areas in order to understand the modality of the convergence and collision process between the indian and eurasian plates based on rayleigh waves dispersion theory we collected long period and broad band seismic data from the global and regional seismic networks surrounding the study area 20 n 50 n 70 e 110 e after applying instrument response calibration and filtering group velocities of the fundamental mode of rayleigh waves are measured using the frequency time analysis ftan combining the published dispersion data a 2 d surface wave tomography method is applied to calculate the lateral variations of group velocity distribution at different periods in the range from 8 s to 150 s the hedgehog non linear inversion method is performed to obtain shear wave velocity vs versus depth models of the crust and upper mantle for 181 cells with size 2 2 in order to identify the cellular representative models we applied the local smoothness optimization method lso fairly detailed structural models of the lithosphere asthenosphere system have been defined the vs models demonstrate the lateral variation of the thickness of the metasomatic lid between the south and north of the bangong nujiang suture bns and the west and east of tibet the variation in thickness of the metasomatic lid may suggest that the leading edge of the subducting indian slab reaches up to bns

origin of ultramafic hosted vein magnesite deposits abstract large deposits of magnesite mgco3 occur either as carbonated ultramafic rocks or as sedimentary beds the origins of both sedimentary and ultramafic hosted deposits remain controversial as does the relationship between them ultramafic hosted deposits are reviewed herein with an emphasis on veins rather than massive bodies magnesium apparently has been supplied to magnesite veins by their ultramafic host uncertainties concerning ultramafic hosted deposits include the source state and mode of transportation of carbon the cause of its precipitation and the mineralogy of the initial precipitate genetic questions about ultramafic hosted vein deposits are summarized with the aid of flow charts the preferred route through these charts attributes most vein magnesite to an influx of metamorphic degassing co2 and ch4 into groundwater which flows through serpentinite or peridotite the source of co2 ch4 is considered to be deeper than 10 km because metamorphism 300 c is required to release carbonaceous volatiles of the type which apparently induced observed magnesite mineralization however vein magnesite precipitation generally has occurred within just a few hundred meters of the earth s surface vein deposits are considered to be genetically related to massive bodies but the massive bodies typically contain less 12c the 12c rich co2 which has produced vein deposits is attributed to a fluid phase variably mixed ch4 co co2 which rose until it reached upper crustal groundwater the hypothetical water poor fluid presumably became slightly oxidized hence richer in soluble co2 as it encountered near surface sulfate bearing water co2 enriched water is envisioned to have been expelled regionally due to tectonic processes leaving little mineralogical evidence of its expulsion through non ultramafic rock co2 rich water which happened to encounter either serpentinite or peridotite presumably has produced magnesite vein deposits and a common silicate byproduct nontronite according to the following reaction 12 mg3si2o5 oh 4 serpentine 36 hco3 4 fe3o4 o2 12 fesi2o5 oh nontronite 36 mgco3 magnesite 36 oh 18h2o

stratigraphy and age of colluvial deposits indicating late holocene soil erosion in northeastern germany abstract in the focus of this study are the sedimentary characteristics chronology magnitude and causes of past soil erosion dynamics of an agriculturally intensively used glacial lowland landscape from the mesoscale quillow river catchment sedimentary sections bearing colluvial sediments from different landforms were analysed to explore their geoarchive potential and to establish a local chronology of late holocene soil erosion sections from footslopes contain a rather simple stratigraphy with one topping colluvial horizon of up to 1 m thickness burying a palaeosol in contrast glacial kettle holes preserve more complex sequences partly having several colluvial layers with intercalating palaeosols the most complex stratigraphy is associated with a kettle hole being the ultimate sediment trap for a dendritic gully system forming a 4 m thick sequence of alternating peat and colluvial layers thirty osl ages and 13 radiocarbon ages are used to reconstruct phases of soil erosion potentially human induced soil erosion which is corroborated by local archaeological and palynological data can be traced back to the last c 4000 years the oldest colluvial deposits date back to the late bronze age most datings however cluster within the last 600 years with a peak in the last 200 years ascribing the main phase of local soil erosion to the recent past thus although numerous archaeological finds are detected in the catchment since the neolithic considerable agricultural soil erosion does not occur before the last millennium a compilation of osl chronologies based on colluvial sediments from other regions in central europe shows a more complex erosion history there with a pronounced two or three phased distribution of ages primarily dating into the last c 4000 5000 years this study underlines that in northeastern central europe human impact on landscapes was effective apparently at a later stage as compared to some adjacent regions

seismic anisotropy and mantle dynamics beneath china abstract we analyzed the shear wave splitting at 138 permanent seismograph stations to study seismic anisotropy and mantle dynamics under mainland china to obtain reliable results we used three different methods to measure the shear wave splitting parameters using core phases sks skks skiks and pks as well as the direct s waves from regional and distant earthquakes our results show that the fast orientations of the anisotropy wnw ese in eastern china are generally consistent with the absolute plate motion apm direction of the eurasian plate suggesting that the anisotropy is mainly located in the asthenosphere resulting from the lattice preferred orientation of olivine due to the shear deformation there the fast axes in western china generally agree with the strikes of the orogens and active faults while they are perpendicular to the direction of the maximum horizontal stress suggesting that the anisotropy in the lithosphere contributes significantly to the observed shear wave splitting the fast axes in western china are also consistent with the apm direction suggesting that the apm driven anisotropy in the asthenosphere is another source of the shear wave splitting there these results suggest that apm driven anisotropy commonly exists under continents similar to that under oceanic regions even though the continental lithosphere has suffered extensive deformation

luminescence dating of glaciofluvial deposits a review abstract for glacigenic sediments optically stimulated luminescence osl dating offers an opportunity to date the time of deposition of quartz and feldspar minerals that are ubiquitous within the sediment matrix rather than relying upon the chance occurrence of organic material for radiocarbon dating the osl dating signal or charge accumulates in crystal defects of individual quartz and feldspar minerals through exposure to environmental radiation within their depositional setting the osl signal within individual grains can be reset or bleached through exposure to daylight during transportation processes thus osl dating of sediments attempts to determine the time elapsed since burial glacigenic sediments present considerable challenges for osl dating not only in terms of poor bleaching of the osl signal during the transport and deposition cycle but also poor quartz luminescence characteristics which are often related to sediment provenance the nature of the bedrock or source material and the freshly eroded nature of many such deposits this paper reviews luminescence dating techniques as applied to glaciofluvial sediments and explores the challenges that such deposits present to the technique successful application of osl techniques can be judged in a number of ways comparison with the independent chronologies is prevalent in the literature but recently the movement towards measurement of large numbers of small aliquots and single grains allows a more robust assessment of luminescence properties and behaviour for individual samples and ultimately more precise luminescence ages to be determined for glaciofluvial sediments in particular it is important to investigate the depositional sub environment of each sample in relation to the chance of sufficient bleaching during transport and deposition a lithofacies based approach to sampling for optically stimulated luminescence dating of these sediments is suggested whereby hypothetically well bleached deposits are targeted after a detailed investigation into possible environments of deposition this approach together with small aliquot single grain analysis methodologies should further enhance the likelihood of obtaining a sufficiently bleached sample for osl dating

geochronological osl and geomorphological investigations at the presumed frankfurt ice marginal position in northeast germany abstract the weichselian frankfurt ice marginal position in northeast germany has been critically discussed in the past owing to weak morphological evidence and a lack of clear sedimentological records this study aims to contribute to this discussion with new geochronological and geomorphological results apart from very few cosmogenic exposure ages the time frame is to date still based on long distance correlation with radiocarbon chronologies we selected a study site in a key position regarding the classic location of the frankfurt ice marginal position and the recently described arcuate ridge structures on the barnim plateau for the first time we present optically stimulated luminescence osl ages of quartz from glaciofluvial deposits for this weichselian phase our results indicate an advance of the scandinavian ice sheet sis at around 34 1 4 6 ka this is in agreement with osl ages from sandur deposits at the brandenburg ice marginal position located farther south and could also be correlated with the klintholm advance in denmark the subsequent meltdown phase lasted until around 26 3 3 7 ka during the meltdown phase a minor oscillation of the sis caused the formation of the recently described arcuate ridges on the barnim till plain recalculated surface exposure ages of glacigenic boulders with an updated global production rate indicate a landscape stabilization phase at around 22 7 1 6 ka which is in agreement with our ages a phase of strong aeolian activity has been dated with osl to 1 0 1 ka this may have been triggered by human activities that are documented in this region for the medieval period

the timing of the weichselian pomeranian ice marginal position south of the baltic sea a critical review of morphological and geochronological results abstract the pomeranian phase of the weichselian glaciation in northern middle europe has been the object of investigation in various studies aiming to derive numerical ages for this specific phase apart from traditional 14 c chronologies surface exposure dating with in situ produced terrestrial cosmogenic nuclides and optically stimulated luminescence dating have been applied by different authors the ages derived are so far not consistent generally cosmogenic exposure dating results in younger ages 15 ka and luminescence dating results in older ages 20 ka for the formation of the pomeranian phase the apparent age gap has been subject to discussions from both methodological and geomorphological viewpoints we recalculated compiled exposure ages with a recent calibration data set which reflects very recent progress in cosmogenic nuclide dating and received results that differ significantly from the originally published ages the newly calculated ages deviate 9 15 from the original ages from the source studies towards the older age range thus reducing the offset between the different dating methods and supporting the theory that the onset of the pomeranian phase was earlier in the marine isotope stage 2 in one example from northeast germany good agreement between both methods results from the recalculations corroborated also by the local geomorphology nevertheless postdepositional movement of glacial boulders as well as erosion and shielding effects are hard to quantify and most probably cause an underestimation of exposure ages the study aims to contribute to a critical evaluation of existent chronologies for the southern margin of the scandinavian ice sheet

shear wave splitting across the ailao shan red river fault zone sw china 1 a broad band seismic array was set up across the ailao shan red river asrr fault zone sw china the shear wave splitting parameters on sks and skks phases are calculated using the method of silver and chan 1991 and indicate the polarization direction of 105 6 and the delay time of 1 68 0 44 s beneath the asrr fault zone combined with previous studies the average polarization direction is 110 19 and the delay time is 1 58 0 44 s to the sw side of the fault while the values are 83 30 and 1 29 0 29 s to the ne side this result implies that the upper mantle anisotropy to two sides of the asrr fault zone are different compared with the se polarization direction observed in the p s phase and the n to s surface movement in gps data our results suggest decoupling of the crust and upper mantle beneath the study region

fine crustal and uppermost mantle s wave velocity structure beneath the tengchong volcanic area inferred from receiver function and surface wave dispersion constraints on magma chamber distribution the tengchong volcanic area is located in the southeastern margin of the collision zone between the indian and eurasian plates it is one of the youngest intraplate volcano groups in mainland china imaging the s wave velocity structure of the crustal and uppermost mantle beneath the tengchong volcanic area is an important means of improving our understanding of its volcanic activity and seismicity in this study we analyze teleseismic data from nine broadband seismic stations in the tengchong earthquake monitoring network we then image the crustal and uppermost mantle s wave velocity structure by joint analysis of receiver functions and surface wave dispersion the results reveal widely distributed low velocity zones we find four possible magma chambers in the upper to middle crust and one in the uppermost mantle the chamber in the uppermost mantle locates in the depth range from 55 to 70 km the four magma chambers in the crust occur at different depths ranging from the depth of 7 to 25 km in general they may be the heat sources for the high geothermal activity at the surface based on the fine crustal and uppermost mantle s wave velocity structure we propose a model for the distribution of the magma chambers

the geological evolution of the tibetan plateau the geological evolution of the tibetan plateau is best viewed in a context broader than the india eurasia collision zone after collision about 50 million years ago crust was shortened in western and central tibet while large fragments of lithosphere moved from the collision zone toward areas of trench rollback in the western pacific and indonesia cessation of rapid pacific trench migration 15 to 20 million years ago coincided with a slowing of fragment extrusion beyond the plateau and probably contributed to the onset of rapid surface uplift and crustal thickening in eastern tibet the latter appear to result from rapid eastward flow of the deep crust probably within crustal channels imaged seismically beneath eastern tibet these events mark a transition to the modern structural system that currently accommodates deformation within tibet

the magnesite deposit at main creek savage river tasmania the magnesites at main creek a tributary of savage river in northwestern tasmania are associated with dolomite and talc chlorite schist in a mildly metamorphosed belt running northeastward across the area the nearly vertically dipping lens of magnesite is over 218 m thick and although the extension to the south and north is very uncertain reserves most likely exceed 40 million metric tons as a result mining is being considered a further deposit of about equal size is found to the north at arthur river the carbonate mineralogy is well characterized by the use of a very sensitive backscattered electron detector which easily distinguishes magnesite and dolomite and also demonstrates the zoning of mg and fe in both the magnesite and dolomite apart from the thin bands of schist and dolomite the magnesite ore contains about 5 to 10 percent quartz and 5 to 10 percent dolomite in the upper dolomite horizons especially replacement of dolomite by magnesite is evident mg metasomatism by dilute mgcl 2 solutions is considered more likely than a sedimentary origin the amount of feco 3 in the magnesite falls steadily from about 3 percent at the surface to less than 1 percent feco 3 at 305 m experimental studies of johannes 1970 suggest that a mgcl 2 solution with small amounts of fecl 2 would be expected to form more fe rich magnesite at higher cooler horizons and more mg rich magnesite at depth it is also suggested that the savage river magnesites which were once dolomites may be contemporaneous with the savage river dolomites which lie to the west outside the arthur lineament and which are considered to be early cambrian in age

investigation of the moho discontinuity beneath the chinese mainland using deep seismic sounding profiles abstract we herein describe the depth distribution of the moho beneath the chinese mainland determined via compilation and resampling of the interpreted results of crustal p wave velocity structures obtained from deep seismic soundings dsss performed since the pioneering dss work carried out in the qaidam basin in 1958 for the present study 114 wide angle seismic profiles acquired over the last 50 years were collated we included results for crustal structures from several profiles in japan and south korea to improve the reliability of the interpolation of the moho depth distribution our final moho map shows that the depth of the moho ranges from 10 to 85 km the deepest moho discontinuity at approximately 70 85 km beneath the tibetan plateau was formed by ongoing continent continent collision the moho beneath the eastern north china craton at a relatively constant 30 35 km has endured mantle lithosphere destruction the moho depths determined from active seismology are consistent within 3 5 km with results obtained from gravity inversion and surface wave tomography the spatial variation of the moho depth crustal formation and composition of different tectonic blocks contribute to controls on the spatial distribution of the seismicity and rheology in the crust beneath mainland china

early holocene succession of vegetation and molluscs in lake jaczno east central europe abstract here we present results of high resolution palaeoecological studies of the organic deposits accumulated in lake jaczno located in the north eastern poland plant macrofossils and malacological analyses complimented by radiocarbon dating ams were undertaken to reconstruct early holocene succession of the pioneer wetland plants and molluscs in the lake ecosystem numerous presence of charcoal pieces 1 mm and fungal remains sclerotia in the peat layer accumulated on the mineral ground document dry habitat what coincides with warm and dry climate conditions in the early holocene recorded in this part of europe change to lacustrine environment documented by accumulation of the carbonate gyttja on the highly decomposed peat layer took place ca 10 500 cal yr bp the current morphology of lake jaczno in which several basins can be distinguished suggests that different age of sediments accumulated at the bottom part at our sampling sites might result from different sizes of the buried dead ice blocks and their heterochronous final melting the first aquatic plants that appeared in lake jaczno were chara sp ceratophyllum demersum and nymphaea alba the appearance of cladium mariscus in lake jaczno ca 9400 cal yr bp was synchronous with the substantial spread of this plant in this region which coincided with increased climate humidity the first molluscan species that colonized the lake ecosystem were gyraulus crista and bithynia tentaculata species living on macrophytes and valvata piscinalis typical for habitats characterized by a thick layer of plant detritus

deep structure of japan subduction zone as derived from local regional and teleseismic events we have determined a detailed three dimensional p wave velocity structure of the japan subduction zone to 500 km depth by inverting local regional and teleseismic data simultaneously we used 45 318 p wave arrivals from 1241 shallow and deep earthquakes which occurred in and around the japan islands the arrival times are recorded by the japan university seismic network which covers the entire japan islands densely and uniformly we also used 4211 travel time residuals from 100 teleseismic events which are read from seismograms recorded by seismic stations in northeastern japan in comparison with the previous results obtained from only local and regional events the present result for the area around the lower plate boundary and the mantle below the plate is determined more reliably because of the addition of 7035 data from 100 teleseismic events and 41 very deep earthquakes in the crust and uppermost mantle low velocity zones are clearly visible beneath active volcanoes in the mantle wedge the low velocity zones generally parallel with the slab and exist continuously to a depth of about 200 km which is consistent with the petrological geochemical and geodynamic studies we consider that the existence of volcanism related low velocity anomalies in the mantle wedge is a general seismological characteristic of subduction zones in light of all the available tomographic results for many subduction zones in the world the pacific slab beneath japan is imaged more clearly than in previous studies as a high velocity zone with a thickness of 80 90 km and a p wave velocity 4 6 higher than the normal mantle lower velocity anomalies are found in the mantle below the slab

late quaternary landscape development at the margin of the pomeranian phase mis 2 near lake wygonin northern poland abstract in central europe late quaternary landscapes experienced multiple phases of geomorphologic activity in this study we used a combined geomorphological pedological sedimentological and palynological approach to characterize landscape development after the last glacial maximum lgm near lake wygonin in northern poland the pedostratigraphical findings from soil pits and drillings were extrapolated using ground penetrating radar gpr and electric resistivity tomography ert during the pomeranian phase glacial and fluvioglacial processes dominated the landscape near lake wygonin at the end of the glacial period periglacial processes became relevant and caused the formation of ventifacts and coversands containing coated sand grains at approximately 15 290 14 800 cal yr bp a small pond formed in a kettle hole profile bwi 2 the lacustrine sediments lack eolian sand components and therefore indicate the decline of eolian processes during that time the increase of juniperus and rock rose helianthemum in the pollen diagram is a prominent marker of the younger dryas at the end of the younger dryas a partial reshaping of the landscape is indicated by abundant charcoal fragments in disturbed lake sediments no geomorphologic activity since the beginning of the holocene is documented in the terrestrial and wetland archives the anthropogenic impact is reflected in the pollen diagram by the occurrence of rye pollen grains secale cereale and translocated soil sediments dated to 1560 1410 cal yr bp proving agricultural use of the immediate vicinity with the onset of land use gully incision and the accumulation of colluvial fans reshaped the landscape locally since 540 460 cal yr bp further gully incision in the steep forest tracks has been associated with the intensification of forestry outside of the gully catchments the weakly podzolized rubic brunic arenosols show no features of holocene soil erosion

implications of shortening in the himalayan fold thrust belt for uplift of the tibetan plateau 1 recent research in the himalayan fold thrust belt provides two new sets of observations that are crucial to understanding the evolution of the himalayan tibetan orogenic system first u pb zircon ages and sm nd isotopic studies demonstrate that 1 greater himalayan medium to high grade metasedimentary rocks are much younger than true indian cratonic basement and 2 these rocks were tectonically mobilized and consolidated with the northern margin of gondwana during early paleozoic orogenic activity these observations require that greater himalayan rocks be treated as supracrustal material in restorations of the himalayan fold thrust belt rather than as indian cratonic basement in turn this implies the existence of greater himalayan lower crust that is not exposed anywhere in the fold thrust belt second a regional compilation of shortening estimates along the himalayan arc from pakistan to sikkim reveals that 1 total minimum shortening in the fold thrust belt is up to 670 km 2 total shortening is greatest in western nepal and northern india near the apex of the himalayan salient and 3 the amount of himalayan shortening is equal to the present width of the tibetan plateau measured in an arc normal direction north of the indus yalu suture zone this information suggests that a slab of greater indian lower crust composed of both indian cratonic lower crust and greater himalayan lower crust with a north south length of 700 km may have been inserted beneath the tibetan crust during the cenozoic orogeny we present a modified version of the crustal underthrusting model for himalayan tibetan orogenesis that integrates surface geological data recent results of mantle tomographic studies and broadband seismic studies of the crust and upper mantle beneath the tibetan plateau previous studies have shown that incremental mesozoic and early cenozoic shortening had probably thickened tibetan crust to 45 55 km before the onset of the main cenozoic orogenic event thus the insertion of a slab of greater indian lower crust with maximum thickness of 20 km tapering northward could explain the cenozoic uplift of the tibetan plateau the need for tibetan crust to stretch laterally as the greater indian lower crust was inserted may explain the widespread east west extension in the southern half of the plateau our reconstruction of the himalayan fold thrust belt suggests that indian cratonic lower crust of presumed mafic composition and high strength should extend approximately halfway across the tibetan plateau to the banggong suture from there northward we predict that the tibetan plateau is underlain by more felsic and therefore weaker lower crust of greater himalayan affinity two slab break off events are predicted by the model the first involved neotethyan oceanic lithosphere that foundered 45 35 ma and the second consisted of greater indian lithosphere most likely composed of greater himalayan material that delaminated and foundered 20 10 ma asthenospheric upwelling associated with the break off events may explain patterns of cenozoic volcanism on the tibetan plateau although the model predicts a northward migrating topographic front due solely to insertion of greater indian lower crust the actual uplift history of the plateau was complicated by early middle tertiary shortening of tibetan crust

geodynamics of the southeastern tibetan plateau from seismic anisotropy and geodesy ongoing plate convergence between india and eurasia provides a natural laboratory for studying the dynamics of continental collision a fi rst order process in the evolution of continents regional climate and natural hazards in southeastern tibet the fast directions of seismic anisotropy determined using shear wave splitting analysis correlate with the surfi cial geology including major sutures and shear zones and with the surface strain derived from the global positioning system velocity fi eld these observations are consistent with a clockwise rotation of material around the eastern himalayan syntaxis and suggest coherent distributed lithospheric deformation beneath much of southeastern tibet at the southeastern edge of the tibetan plateau we observe a sharp transition in mantle anisotropy with a change in fast directions to a consistent e w direction and a clockwise rotation of the surface velocity surface strain fi eld and fault network toward burma around the eastern himalayan syntaxis the coincidence between structural crustal features surface strain and mantle anisotropy suggests that the deformation in the lithosphere is mechanically coupled across the crust mantle interface and that the lower crust is suffi ciently strong to transmit stress at the southeastern margin of the plateau in yunnan province a change in orientation between mantle anisotropy and surface strain suggests a change in the relationship between crustal and mantle deformation lateral variations in boundary conditions and rheological properties of the lithosphere play an important role in the geodynamic evolution of the himalayan orogen and tibetan plateau and require the development of three dimensional models that incorporate lateral heterogeneity

groundwater flow under a paleo ice stream of the scandinavian ice sheet and its implications for the formation of stargard drumlin field nw poland

the last deglaciation of the southeastern sector of the scandinavian ice sheet the scandinavian ice sheet sis was an important component of the global ice sheet system during the last glaciation but the timing of its growth to or retreat from its maximum extent remains poorly known we used 115 cosmogenic beryllium 10 ages and 70 radiocarbon ages to constrain the timing of three substantial ice margin fluctuations of the sis between 25 000 and 12 000 years before the present the age of initial deglaciation indicates that the sis may have contributed to an abrupt rise in global sea level subsequent ice margin fluctuations identify opposite mass balance responses to north atlantic climate change indicating differing ice sheet sensitivities to mean climate state

timing of the late vistulian weichselian glacial phases in poland abstract the lower vistula region in northern poland is a stratotype area for the vistulian weichselian glaciation and during last glacial maximum lgm the southernmost extension of the scandinavian ice sheet occurred in western poland and in eastern germany reinterpretation of the available geochronological data radiocarbon 36 cl and 10 be ages supplied with new field geological evidence mostly for the late vistulian ice sheet limits and movement directions was focused in three key regions in poland during the late middle vistulian there was one or two ice sheet advances in the lower vistula region the late vistulian maximum ice sheet limit in poland was time transgressive and occurred at 24 19 kyrs bp generally the younger to the east ice sheet limits during the leszno phase occurred at 24 cal 10 be 36 cl kyrs the poznan phase ice sheet limit was dated to 19 10 be 36 cl kyrs and the pomeranian phase ice sheet limit about 16 17 10 be 36 cl kyrs every late vistulian glacial phase in poland was preceded by an ice sheet retreat

the role of melting dead ice on landscape transformation in the early holocene in tuchola pinewoods north poland abstract on the basis of macrofossil and pollen analyses ams 14 c dating and geomorphological investigations we reconstructed the development of hydrological changes during the lateglacial to early holocene transition in tuchola pinewoods bory tucholskie in northern poland in this region the wda river flows in polygenetic valleys typical for the young glacial landscape of the northern central european lowlands the middle section of this river provides a suitable setting to demonstrate the environmental and hydrological changes in the late glacial and early holocene because 1 it is a small and well defined area and 2 the existence of a morphologically preserved river valley from late glacial period in this study we focused on a short terrestrial sediment core 48 cm that represents four phases of landscape evolution during the early holocene telmatic lacustrine lacustrine fluvial and alluvial abrupt changes in lithology and sediment structures exhibit rapid changes and threshold processes in environmental conditions the ams 14 c dating of terrestrial plant remains revealed an age for the basal sediments of 11 223 23 cal bp and thus falls within the preboreal biozone plant macrofossil indicators provide evidence of water level and edaphic changes in the basin the results of our study demonstrate a strong influence of melting buried ice blocks on the geomorphological development hydrological changes in the catchment and the biotic environment in the early holocene

varied thermo rheological structure mechanical anisotropy and lithospheric deformation of the southeastern tibetan plateau abstract to investigate the lithospheric structure and deformation of the tibetan plateau we present thermo rheological models for two transects across the southeastern tibetan plateau se tibet showing strong lateral heterogeneity the geodynamic implications are also investigated in relation to gps motions seismic anisotropy seismicity distribution and crustal isostatic state the unmatched pattern between pms and sks splittings which even intersect at right angles to the south of 26 n suggests the crust mantle decoupling constrained by a brittle load bearing layer at the uppermost mantle beneath the indochina block the decoupling may occur below the uppermost mantle the strong crust beneath the south china plate and indochina block implied by the seismicity distribution has two thick brittle load bearing layers indicating a coupled system the crust beneath the emeishan large igneous province elip also has two brittle load bearing layers but the brittle deformation is restricted to the topmost 10 km of the upper and lower crust only one brittle load bearing layer resides in the upper crust in the other part of the chuandian block combining with gps and pms splitting we can infer that the weak crust with seismicity restricted into the depth of

palaeosols and their cover sediments of a glacial landscape in northern central europe spatial distribution pedostratigraphy and evidence on landscape evolution abstract knowledge of the distribution types and properties of buried soils i e palaeosols is essential in understanding how lowlands in northern central europe have changed over past millennia this is an indispensable requirement for evaluating long term human impact including soil erosion and land cover dynamics in the serrahn area 62 km2 a young glacial landscape representative for northeastern germany and part of the muritz national park 26 pedosedimentary sections were documented and analysed to this end a multiproxy approach was applied using pedology micromorphology geochronology and palaeoecology statistical and spatial analyses of c 5200 soil profiles of which 10 contain palaeosols show that buried soils cover an area of 5 7 km2 i e 9 of the area studied most palaeosols are cambisols arenosols and gleysols palaeosols are mainly covered by aeolian and colluvial sands as well as by lacustrine sands and peat radiocarbon and luminescence dating together with palynological and anthracological data reveal that former land surfaces were dominantly buried through erosion triggered by human activity in the late holocene in addition but to a clearly smaller extent lateglacial early holocene palaeosols and cover sediments occur following medieval clear cutting and intensive land use the study area is today again widely forested the high share of buried land surfaces detected here is expected to be representative for the hilly glacial landscapes even in the wider region i e in northern central europe and should be considered in soil mapping soil carbon budgeting and assessments of past human impact

metallogeny and tectonic development of the tasman fold belt system in tasmania abstract in western tasmania precambrian sedimentary sequences form the basement for narrow trough accumulations of eocambrian and younger sequences the main trough the meridional dundas trough is flanked to the west by the rocky cape region of precambrian rocks within which major apparently stratiform exhalative magnetite pyrite deposits are intercalated with metabasaltic volcanics and ultramafic bodies the eocambrian cambrian troughs apparently developed during extension of precambrian continental crust early shallow water deposition includes thick dolomite units in some troughs deepening of the troughs was accompanied by turbidite sedimentation with minor limestone and submarine basaltic volcanism with associated minor disseminated native copper ultramafic and related igneous rocks were tectonically emplaced in some troughs during a mild compressional phase they contain only minor platinoids copper nickel sulphides and asbestos but are source rocks for tertiary secondary deposits of platinoids chromite and lateritic nickel in the dundas trough eocambrian early cambrian rocks are separated by an inferred erosional surface from structurally conformable overlying middle to late cambrian fossiliferous turbidite sequences the structural conformity continues through overlying ordovician to early devonian terrestrial and shallow marine stable shelf deposits a considerable pile of probable middle cambrian felsic volcanics accumulated between the sedimentary deposits of the dundas trough and the tyennan region of precambrian rocks to the east a lava dominated belt within the volcanics hosts major volcanogenic massive sulphide deposits including those of the exhalative type which in the south are enriched in copper gold and silver whereas in the north they are rich in zine lead copper gold and silver cambrian movements along faults near the margin of the tyennan region resulted in erosion of the mineralized volcanics locally exposing sub volcanic granitoids above the local unconformities occur unmineralized volcaniclastic sequences that pass conformably into ordovician to early devonian shelf deposits ordovician limestone locally hosts stratabound disseminated and veined base metal sulphide deposits pre middle devonian rocks of western tasmania differ for most part from those in the northeast where deeper marine turbidite quartz wacke sequences were deposited during the ordovician and early devonian the eocambrian to early devonian rocks of tasmania were extensively deformed in the mid devonian the precambrian regions of western tasmania behaved as relatively competent blocks controlling early fold patterns in northeastern tasmania folding is of similar age but resulted from movements inconsistent with those affecting rocks of equivalent age in western tasmania the final metallogenic event is associated with high level granitoid masses emplaced throughout tasmania during the middle to late devonian in northeastern tasmania extensive i type granodiorite and s type granite with alkali feldspar granites are associated with mainly endogranitic stanniferous grelsens and wolframite cassiterite vein deposits in contrast scheelite bearing skarns and cassiterite stannite pyrrhotite carbonate replacement deposits are dominant in western tasmania associated mainly with s type granites several argentiferous lead zinc vein deposits occur in haloes around tin tungsten deposits a number of gold deposits are apparently associated with i type granodiorite but some have uncertain genesis the contrasting regions of western and northeastern tasmania have probably been brought together by lateral movement along an inferred fracture flat lying late carboniferous and younger deposits rest on the older rocks and the only known post devonian primary mineralization is gold associated with creta ceous syenite

late quaternary ice sheet extents in northeastern germany inferred from surface exposure dating abstract we determined in situ cosmogenic 10 be ages for 11 boulders on the hoher flaming ice marginal belt and five boulders on the gerswalder moraine a recessional moraine of the pomeranian stage previous time estimations for the deposition of these moraines along the southern margin of the scandinavian ice sheet sis in northeastern germany are mostly based on geomorphology and stratigraphy and on few radiocarbon dates and recently published surface exposure ages in the case of the pomeranian moraine our new exposure ages range from 21 7 1 2 10 be ka to 172 6 6 0 10 be ka for the hoher flaming ice marginal belt the wide range of exposure ages may reflect episodic ice marginal belt modification due to intensified erosion by meltwater channeled in the baruther urstromtal ice marginal valley accompanied by long lasting erosional processes like solifluction and aeolian deflation for the gerswalder moraine our new exposure ages range from 12 3 0 6 10 be ka to 16 6 1 0 10 be ka excluding the youngest sample ber 97 03 we calculated error weighted mean ages ranging from 15 2 0 5 10 be ka to 16 0 0 5 10 be ka n 4 depending on choice of scaling methods surface erosion and snow cover these results firmly establish the position of the southern margin of the sis in northeastern germany during the gerswalder substage a recessional phase of the pomeranian stage

surface dating of dynamic landforms young boulders on aging moraines the dating of landforms is crucial to understanding the evolution history and stability of landscapes cosmogenic isotope analysis has recently been used to determine quantitative exposure ages for previously undatable landform surfaces a pioneering application of this technique to date moraines illustrated its considerable potential but suggested a chronology partially inconsistent with existing geological data consideration of the dynamic nature of landforms and of the ever present processes of erosion deposition and weathering leads to a resolution of this inconsistency and more generally offers guidance for realistic interpretation of exposure ages

insight into the origin of the tengchong intraplate volcano and seismotectonics in southwest china from local and teleseismic data received 18 june 2008 revised 22 february 2009 accepted 10 march 2009 published 13 may 2009 1 a high resolution tomographic image of the crust and upper mantle under yunnan province in southwest china was determined by using a large number of teleseismic data measured precisely from digital seismograms as well as local earthquake arrival times recorded by the dense yunnan seismic network the grid spacing of the tomographic model is 70 km 78 km in the horizontal directions and 4 70 km in depth our resulting model shows a clear low velocity low v 0 3 with respect to the average one dimensional velocity model column extending from the surface down to about 400 km depth under the active tengchong volcano and some high velocity high v anomalies existing in the mantle transition zone furthermore the low vanomaly extends horizontally toward the northeast at 250 to 400 km depth combining our tomographic results with geochemical and geological investigations we infer that the tengchong volcano is a rift related volcano caused by the subduction and dehydration of the indian plate as well as corner flow in the mantle wedge though the subducted slab is a continental plate our results show that the upwelling flow under tengchong originates at 400 km depth a prominent low v anomaly along the red river fault zone extends down to the upper mantle 100 km depth reflecting that the red river fault zone may have cut through the crust to the upper mantle the two dayao earthquakes m 6 1 and m 6 2 in 2003 occurred on the margin of high v anomalies and are underlain by a prominent low v anomaly in the lower crust and upper mantle suggesting that the dayao earthquakes may be associated with fluids released from the dehydration of the subducted indian slab these results are significantly improved compared with previous studies and provide new seismic constraints on the dynamic processes of the india asia collision

optical dating of sediments a new method for dating sediments is proposed which determines the time since the sediment was last exposed to sunlight an argon ion laser is used to excite electrons from thermally stable light sensitive traps and the subsequent luminescence used as a measure of the past radiation dose two sample sequences spanning the periods 0 700 kyr and 0 6 kyr show steadily increasing luminescence with age an age of 62 8 kyr is obtained for a silt radiocarbon dated at 58 8 0 3 kyr problems were found with two much younger samples

on the age of the young morainic morphology in the area ascribed to the maximum extent of the weichselian glaciation in north eastern germany abstract in this case study the first numerical ages from the area ascribed to the maximum extent of the weichselian glaciation in north eastern germany are presented the ages were derived from fluvioglacial sandur sediments of the luckenwalde area using optically stimulated luminescence dating techniques for the dating of quartz the ages reveal a primary formation of the luckenwalde outwash plain in the warthe stage of the saalian glaciation 130 150 ka and a limited reworking of the sediments mainly linked to meltwater activity during the weichselian glaciation due to the insufficient zeroing of the osl signal of the sediments the timing of that event can only be determined by a maximum age of around 35 ka nevertheless this age is in accordance with results from the beelitz outwash cone indicating an ice advance in mis 2 the results of the luminescence measurements are supported by additional stratigraphical and petrographical findings it is likely that a considerable number of landforms attributed to the weichselian glaciation are originally of saalian age only partly overridden by the weichselian glaciation but not reshaped by this process with transformation of the relief mainly linked to meltwater processes this implies a very thin probably warm based ice cover of a fast paced and short lived weichselian ice advance adapting to a pronounced saalian morphology

cenozoic rifting and volcanism in eastern china a mantle dynamic link to the indo asian collision abstract the indo asian continental collision is known to have had a great impact on crustal deformation in south central asia but its effects on the sublithospheric mantle remain uncertain studies of seismic anisotropy and volcanism have suggested that the collision may have driven significant lateral mantle flow under the asian continent similar to the observed lateral extrusion of asian crustal blocks here we present supporting evidence from p wave travel time seismic tomography and numerical modeling the tomography shows continuous low velocity asthenospheric mantle structures extending from the tibetan plateau to eastern china consistent with the notion of a collision driven lateral mantle extrusion numerical simulations suggest that at the presence of a low viscosity asthenosphere continued mass injection under the indo asian collision zone over the past 50 my could have driven significant lateral extrusion of the asthenospheric mantle leading to diffuse asthenospheric upwelling rifting and widespread cenozoic volcanism in eastern china

joint inversion of surface wave dispersions and receiver functions with p velocity constraints application to southeastern tibet we introduced a p velocity model into the traditional joint inversion of p receiver function rf and surface wave dispersions to reduce model ambiguity the method was implemented using a global search based algorithm and a flexible parameterization of a sedimentary layer and spline based parameterization that can represent sharp discontinuities we applied the method to a dense array in se tibet longitude 97 5 e to 107 e latitude 25 3 n extensive tests using synthetic and real data suggest that the method is suitable and robust for a variety of velocity structures and moho discontinuities and can simultaneously provide the crustal vp vs profile and better constrained moho depth the flexibility of the parameterization and the inclusion of the vp constraint are crucial in the improved model recovery artifacts may be created without including the sedimentary layer even when it is less perfect a reasonable vp model is valuable in such a joint inversion we showed that crustal multiples in rfs may bias the traditional h k results when the crust structure is complex and should be avoided in a joint inversion before appropriate corrections can be made the results from the joint inversion show two low velocity zones lvzs reported previously and were identified as channels of crustal flow a prominent isolated lvz is observed in the mid lower crust under the xiaojiang fault area which correlates with anomalously high vp vs ratios indicating possible partial melting however the other lvz is imaged to be in the brittle shallow upper crust without very high vp vs ratios which is likely associated with crustal fault zones rather than partial melting we observe clear low velocity structures in the mantle beneath the two crustal lvzs which also correlate with zones of low resistivity the crust mantle correlation may suggest influence of mantle processes on crustal deformation