changing features of the climate and glaciers in china s monsoonal temperate glacier region 1 climatic data ice core records the tree ring index and recorded glacier variations have been used to reconstruct a history of climatic and glacial changes in the monsoonal temperate glacier region of southwestern china during the last 400 years the region s temperature has increased in a fluctuating manner during the twentieth century after two cold stages of the little ice age seventeenth to nineteenth centuries with a corresponding retreat of most of the glaciers against a background of global warming retreat rates accelerated after the 1980s the few advancing glaciers that did exist have started to retreat in recent years the amount trend and amplitude of variation of precipitation have differed in different parts of the region the dasuopu ice core from the western part of the region shows a decreasing trend in precipitation the converse of the trend in temperature in the eastern part of the region however a rising trend of rainfall has accompanied increasing temperatures as a result of the variable atmospheric circulations from different sources the southwest monsoon the principal controlling factor in the chinese monsoonal temperate glacier region can be classified into the indian monsoon and the bengal monsoon the former passes across the indian peninsula from the arabian sea and transports vapor for precipitation in the western part of the monsoonal temperate glacier region the bengal monsoon originating in the bay of bengal is the major source of precipitation in the eastern part of the region the eastern part is also influenced by the southeast monsoon arriving from the western pacific and the western part is affected in winter by the southern branch of the westerly circulation this complex atmospheric situation results in differing patterns of precipitation in the western and eastern zones although it is clear that both temperature and precipitation affect the glaciers further work is needed to confirm which of these is the major factor influencing present glacier change

quantifying global warming from the retreat of glaciers records of glacier fluctuations compiled by the world glacier monitoring service can be used to derive an independent estimate of global warming during the last 100 years records of different glaciers are made comparable by a two step scaling procedure one allowing for differences in glacier geometry the other for differences in climate sensitivity the retreat of glaciers during the last 100 years appears to be coherent over the globe on the basis of modeling of the climate sensitivity of glaciers the observed glacier retreat can be explained by a linear warming trend of 0 66 kelvin per century

origin of perylene in ancient sediments and its geological significance the distributions of polycyclic aromatic hydrocarbons pahs in sediments of three upper triassic to middle jurassic sedimentary sequences from the northern carnarvon basin australia have been investigated perylene was found to be a major pah component in the top lower to base middle jurassic sediments that are immature or at low maturity its depth age profiles are not related to the combustion derived pahs that have been believed to be produced during ancient vegetation fires before deposition this suggests a diagenetic origin for perylene the concentration of perylene in the sediments is proportional to the amount of terrestrial input decreasing with distance from the source of land sediments its carbon isotope composition is slightly heavier than higher plant derived pahs but still in the range of the terrestrially sourced pahs including higher plant pahs and combustion derived pahs as suggested previously fungi are proposed to be the major precursor carriers for perylene in sediments based on the facts that 1 perylenequinone structures have been previously suggested to be the natural precursors for perylene 2 perylenequinone pigments exist in many fungal bodies 3 fungi have played an important role during geological processes

recent climatic significance of chemical signals in a shallow firn core from an alpine glacier in the south asia monsoon region abstract there are 19 sub tropical temperate glaciers on mount yulong the southernmost currently glacier covered area in eurasia controlled by the south western monsoon climate in the summer of 1999 a firn core 10 10 m long extending down to glacier ice was recovered in the accumulation area of the largest glacier baishui no 1 periodic variations of climatic signals above 7 8 m depth were apparent and net accumulation of four years was identified by the annual oscillations of isotopic and ionic composition the boundaries of annual accumulation were confirmed by higher values of electrical conductivity and ph and by dirty refreezing ice layers at the levels of summer surfaces calculated mean annual net accumulation from 1994 95 to 1997 98 was about 900 mm water equivalent the amplitude of isotopic variations in the profile decreased with increasing depth and isotopic homogenization occurred below 7 8 m as a result of meltwater percolation variations of 18 o above 7 8 m showed an approximate correlation with the winter climatic trend at lijiang station 25 km away concentrations of ca 2 and mg 2 were much higher than those of na and k indicating that the air masses for precipitation were mainly from a continental source and that the core material accumulated during the winter period the close correspondence of cl and na indicated their common origin the decreasing trend of na cl ratios with increasing depth further reflects a progressive homogenization process caused by meltwater percolation concentrations of so 4 2 and no 3 in the core are quite low the mean annual net accumulation in the core and the estimated ablation indicate that the average annual precipitation above the glacier s equilibrium line is 2400 3100 mm but this needs to be confirmed by long term observation of mass balance

three dimensional prestack plane wave migration of teleseismic p to s converted phases 1 theory 1 we present the theoretical foundations for a prestack migration technique to image teleseismic p to s converted phases the method builds on teleseismic p wave deconvolution pseudostation stacking neal and pavlis 1999 and on the idea of using a plane wave decomposition for imaging as introduced by treitel et al 1982 deconvolution operators are constructed by pseudostation stacking of the array aligned to the incident p wave arrival times to produce a space variable deconvolution operator the resulting data are then muted to remove the deconvolved direct p wave pulse and pseudostation stacked over a grid of feasible slowness vectors the pseudostation stack interpolates the wave field onto a regular grid along earth s surface producing a series one per slowness vector of uniformly sampled three dimensional data cubes two space variables and time the plane wave components can be propagated downward using a form of approximate ray tracing with a three dimensional earth model this yields a series of distorted cubes topologically equivalent to the original uniformly sampled data cubes these data volumes are summed as a weighted stack with the weights derived from an integration formula for inverse scattering based on the generalized radon transform this allows an image of the subsurface to be constructed on an event by event basis beneath the array we apply this technique to data from the lodore array that was deployed in northwestern colorado the results suggest the presence of a major lithospheric scale discontinuity defined by a south dipping boundary

mantle discontinuities beneath southern africa 1 seismic velocity discontinuities within the top 1000 km of the earth beneath southern africa are imaged by stacking about 1300 source normalized broadband seismograms recorded by the southern african seismic experiment the moho 410 and 660 kilometer discontinuities are clearly detected the mean mantle transition zone thickness is 245 km essentially the same as the global average suggesting that the transition zone is not anomalously warm thus the lower mantle african superplume beneath our study area has no discernible effect on transition zone temperature and is consequently confined to the lower mantle variations in transition zone thickness appear to be related to the presence or absence of thick lithosphere we do not detect several previously reported discontinuities beneath continents such as the hales or lehmann discontinuities and find no evidence for a 520 km discontinuity nor do we detect a previously proposed low velocity zone just above the transition zone

paleoenvironmental application of taxodium macrofossil biomarkers from the bobov dol coal formation bulgaria abstract this study correlates paleobotanical observations with chemical tracers and geological interpretation for bulgarian coals two samples were studied i e clay sediment with embedded twigs paleobotanically assigned to taxodium dubium and plant material scraped off from the leaf imprint of a macrofossil an assignment of the geological age is presented by considering the biomarker assemblage and paleobotanical data in comparison with information already available for taxodium dubium the geochemical data with paleobotanical and geological observations indicate a late oligocene geological age for the bobov dol coal the following points support this assignment i triterpenoids were completely altered to des a lupane or chrysene derivatives and ii diterpenoids were diagenetically converted to their aromatized end products

high molecular weight polycyclic aromatic hydrocarbons in hydrothermal petroleums from the gulf of california and northeast pacific ocean hydrothermal petroleums and heavy tars have been analyzed for polycyclic aromatic hydrocarbons pah with molecular weights greater than that of coronene 300 da samples from the hydrothermal systems in the guaymas basin gulf of california and in the escanaba trough and middle valley northeastern pacific were analyzed by gas chromatography mass spectrometry and high pressure liquid chromatography with diode array absorbance detection mass spectra and fluorescence spectra were used to characterize the compounds several large pahs with six and more rings were identified among the heavy pah production routes via one ring build up and scholl condensation are proposed to explain the observed structures the variations in pah concentrations and distributions between samples from different locales are a consequence of the hydrothermal conditions of generation migration and post depositional alteration

a hypothesis for the origin of perylene based on its low abundance in sediments of green bay wisconsin abstract perylene a polycyclic aromatic hydrocarbon pah that is common in sediments is believed to originate principally from anaerobic diagenesis of organic matter but its precursor material remains enigmatic we have investigated the formation of perylene in a dated sediment core from green bay wi comparisons of sedimentary profiles of perylene anthropogenic pahs land plant derived hydrocarbons and aquatic contributions of organic matter rule out a specific industrial terrigenous or aquatic precursor for perylene instead perylene seems to be formed from any kind of organic matter as a consequence of a specific type of microbial activity in sub bottom sediments despite an abundance of organic matter the amount of perylene is low in green bay and in other organic carbon rich lake sediments the abundant availability of organic matter that stimulates microbial activity in green bay sediments would seem to favor perylene formation in such sediments we therefore hypothesize that the microorganisms responsible for perylene formation do not compete successfully with those that flourish in sediments rich in organic matter perylene formation consequently does not become significant until deeper in sediments after the more reactive types of organic matter have been consumed

decomposition of phase d in the lower mantle and the fate of dense hydrous silicates in subducting slabs abstracthigh pressure high temperature quench type experiments were carried out on serpentine to pressures of 53 gpa andtemperatures between 800 1800oc x ray analyses show that recovered phase assemblages varied considerably for thedifferent high pressure and high temperature studies the dense hydrous magnesium silicate phases decompose sequentiallyas the pressure increases and appear to serve as reservoirs for h 2 o in the mantle eventually releasing it at the highestpressure superhydrous phase b is stable up to pressure equivalent to the boundary between the transition zone and lowermantle phase d decomposes at pressures of 44 gpa equivalent to about 1250 km depth this may de ne the lower depthlimit for the presence of dense hydrous magnesium silicates beyond this pressure only nominally anhydrous phases havebeen recovered in high pressure experiments this may indicate a lack of stoichiometric hydrogen bearing silicate phasesat higher pressure 1998 elsevier science b v all rights reserved keywords x ray diffraction analysis lower mantle serpentine high pressure

soluble ionic and oxygen isotopic compositions of a shallow firn profile baishui glacier no 1 southeastern tibetan plateau in the summer of 2004 a firn profile 18 3m long extending down to glacier ice was recovered in the accumulation area of the largest glacier baishui no 1 on yulong mountain the southernmost glacier covered area in mainland eurasia multivariate empirical orthogonal function eof and statistical correlation analyses of major ion data from the profile demonstrate that three distinct types of ionic material contribute to the chemical characteristics of firn in this monsoonal region material of marine origin which is transported by the indian southwest monsoon crustal materials which come from local sources and anthropogenic pollutants which are produced by industrial and agricultural activities in south asia although the influence of post depositional processes on the seasonal isotopic and soluble ionic compositions is significant dust layers in the firn profile are clearly visible due to the effects of meltwater percolation the dust layers generally coincide with latesummer snow surfaces we therefore use the dust layers combined with the seasonal variations of electrical conductivity ec ca and mg to establish a depth age scale for the firn profile the reconstructed net accumulation has a significant negative correlation with the temperature at lijiang whereas the correlation between the net accumulation and the precipitation amount at lijiang is weak although the do time series of the firn profile was modified significantly by meltwater percolation the correlation between annual mean do values and the indian southwest monsoon index wsi1 is significant this result suggests that do records from monsoon influenced temperate glaciers can provide a valuable record of past variations of the indian southwest monsoon

perylene in lake biwa sediments originating from cenococcum geophilum in its catchment area abstract perylene which is composed of five benzene rings is commonly found in sediments throughout the world at concentrations and distributions that are different from those of other polycyclic aromatic hydrocarbons the only information available on the origin of perylene comes from 4 9 dihydroxyperylene 3 10 quinone dhpq which originates from fungal component symbiosis or from parasites on plants however there is no direct evidence of a mechanism of perylene formation in this study we examined the relationship between sedimentary perylene and cenococcum geophilum c geophilum in a catchment area at lake biwa sclerotium grains of c geophilum containing dhpq were found in this catchment area approximately 40 balls kg 1 dried soil for 1 mm and small sclerotium grains were frequently found in the sediment in the sediment sample we also found broken particles containing perylene and they had a porous structure characteristic of sclerotium grains furthermore the particles contained dhpq in different transformation stages to perylene via 3 10 perylenequinone 3 10 pq this finding was consistent with results from elemental analysis oxygen carbon because a remarkable amount of dhpq originating from c geophilum also exists in the humic acids of soils and because the inputs of compounds to the lake depend strongly on the rivers perylene in the lake biwa sediment originates mainly from the dhpq of c geophilum in its catchment area

seismic evidence for accumulated oceanic crust above the 660 km discontinuity beneath southern africa 1 high pressure assemblages of subducted oceanic crust are denser than the normal upper mantle but less dense than the uppermost lower mantle thus subducted oceanic crust may accumulate at the base of the upper mantle direct observational evidence for this hypothesis however remains elusive we present an analysis of a negative polarity shear wave converted from compressional wave at a seismic discontinuity near 570 600 km depth beneath southern africa the negative polarity of the converted phase indicates a 2 2 0 2 s velocity decrease with depth at the seismic discontinuity this velocity reduction is associated however with a low velocity contrast at the 660 km discontinuity the exsolution of ca perovskite in former oceanic crust at depth greater than 600 km and the associated small volume fraction of ringwoodite are plausible explanations for the apparent paradox between the negative velocity discontinuity and the low velocity contrast at the 660 km discontinuity

a possible terrigenous origin for perylene based on a sedimentary record of a pond lorraine france abstract the origin of perylene a five ring polycyclic aromatic hydrocarbon pah in sediments has been a matter of constant debate and its formation mechanisms remain unclear a perylene record in sediment was described and could support a clear link between perylene and terrigenous organic matter om input the distributions of pahs the variations of organic proxies such as the ratio of terrigenous to aquatic n alkanes tar hc and 5 h stanols 5 sterols ratio in sediments have been investigated sediments were sampled from a pond artificially created during the middle ages from a swampy area in the period prior to the pond creation for which high contributions of terrigenous om were evidenced perylene was found to be the predominant pah furthermore perylene content was shown to increase in response to the establishment of more reducing conditions this result supports the common idea that the main source of perylene is natural and derives from biogenic precursors under reducing conditions the creation of the pond in this wetland is marked by the deposition of a wood rich level characterized both by more oxygenated conditions and higher concentrations of perylene these high concentrations could result from the introduction of high concentrations of biogenic precursors of perylene under oxidative conditions subsequently the progressive burial of the woody level could have allowed the establishment of oxygen depleted conditions and the formation of perylene these results validate the use of perylene as a paleoenvironmental marker of terrigenous sources but it must be carefully used as a marker for syn or post depositional oxygen depleted conditions in lacustrine environments

recent accelerating mass loss of southeast tibetan glaciers and the relationship with changes in macroscale atmospheric circulations the mass balance history 1980 2010 of a monsoon dominated glacier in the southeast tibetan plateau is reconstructed using an energy balance model and later interpreted with regard to macroscale atmospheric variables the results show that this glacier is characterized by significant interannual mass fluctuations over the past three decades with a remarkably high mass loss during the recent period of 2003 2010 analysis of the relationships between glacier mass balance and climatic variables shows that interannual temperature variability in the monsoonal season june september is a primary driver of its mass balance fluctuations but monsoonal precipitation tends to play an accentuated role for driving the observed glacier mass changes due to their covariation concurrence of warm dry and cold wet climates in the monsoon influenced southeast tibetan plateau analysis of the atmospheric circulation pattern reveals that the predominance of anticyclonic cyclonic circulations prevailing in the southeastern northern tibetan plateau during 2003 2010 contributes to increased air temperature and decreased precipitation in the southeast tibetan plateau regionally contrasting atmospheric circulations explain the distinct mass changes between in the monsoon influenced southeast tibetan plateau and in the north tibetan plateau tien shan mountains during 2003 2010 the macroscale climate change seems to be linked with the europe asia teleconnection

the lithosphere asthenosphere boundary in the north west atlantic region abstract a detailed knowledge of the thickness of the lithosphere in the north atlantic is an important parameter for understanding plate tectonics in that region we achieve this goal with as yet unprecedented detail using the seismic technique of s receiver functions clear positive signals from the crust mantle boundary and negative signals from a mantle discontinuity beneath greenland iceland and jan mayen are observed according to seismological practice we call the negative phase the lithosphere asthenosphere boundary lab the seismic lithosphere under most of the iceland and large parts of central greenland is about 80 km thick this depth in iceland is in disagreement with estimates of the thickness of the elastic lithosphere 10 20 km found from postglacial rebound data in the region of flood basalts in eastern greenland which overlies the proposed iceland plume track the lithosphere is only 70 km thick about 10 km less than in iceland which is located directly above the proposed plume at the western greenland coast the lithosphere thickens to 100 120 km with no indication of the iceland plume track identified below jan mayen the lithospheric thickness varies between 40 and 60 km

timing and style of late quaternary glaciation in northeastern tibet glacial successions in the anyemaqen and nianbaoyeze mountains of northeastern tibet are reassessed and new glacial chronologies are presented for these regions cosmogenic radionuclide and optically stimulated luminescence dating indicates that two glacial advances occurred in marine isotope stage mis 3 and mis 2 in the anyemaqen mountains a third advance occurred in the early holocene we suggest that glaciation was synchronous in the anyemaqen and nianbaoyeze mountains as well as in other glaciated areas of tibet and the himalaya that are influenced by the asian monsoon the maximum extent of glaciation occurred early in the last glacial cycle mis 3 during a time of increased insolation when the monsoon intensified and supplied abundant precipitation as snow at high altitude to feed high altitude glaciers this suggests that precipitation as snow is fundamental in controlling glaciation in these regions however the occurrence of glacial advances during the insolation minimum of mis 2 suggests that despite reduced precipitation at this time the annual temperatures were cold enough to maintain positive glacier mass balances the numerically defined chronologies for the anyemaqen and nianbaoyeze mountains presented here provide a framework for comparing glacial advances in other parts of high asia

heterogeneous distribution of water in the mantle transition zone inferred from wavefield imaging abstract the amount of water in the earth s deep mantle is critical for the evolution of the earth mineral physics studies revealed that the mantle transition zone can store several times the volume of water in an ocean however the actual water distribution in the transition zone remains enigmatic we used the highest resolution images produced of scatterers in the north american transition zone derived from teleseismic data recorded by the earthscope transportable array we find that the transition zone is filled with previously unrecognized small scale heterogeneities that produce pervasive negative polarity signals simulations demonstrated the images can be explained by low velocity bodies shaped as distributed blobs or near vertical structures we suggest these low velocity bodies may be heterogeneously distributed water enriched subducted harzburgites produced through long term accumulation

analyses of recent observations of urumqi glacier no 1 chinese tianshan mountains as a reference glacier in the world glacier monitoring service urumqi glacier no 1 is the best observed glacier in china and provides the longest glaciological and climatological monitoring record a topographic survey was carried out in 2012 using the real time kinematic global positioning system glacier thickness was surveyed using ground penetrating radar in the same year in addition glacier terminus change and mass balance were surveyed every year until 2014 the glacier area was totally 1 59 km2 and the east and west branches occupied 1 02 and 0 57 km2 in 2012 respectively the glacier area had decreased by 0 31 km2 from 1962 to 2012 average ice thickness was 44 50 m in 2012 and had thinned by 0 34 m a 1 over 1981 2012 the shrinkage of this glacier is mainly due to climate warming especially summer temperature rise topographic characteristics resulted in a difference in terminus retreat thickness decrease and area shrinkage between the east and west branches of this glacier the analysis suggests that this glacier will possibly continue to shrink in future at least in a coming decade since it needs a response time to previous warming

perylene degradation during gradual onset of organic matter maturation abstract perylene and benzo a pyrene concentration changes during the gradual increase of thermal maturity have been analyzed for the palaeogene podhale flysh deposits and other palaeozoic to cenozoic sedimentary rock samples perylene is present in high relative concentration in the samples of maturation below 0 6 of the vitrinite reflectance rr while in the range of 0 6 0 7 rr its abundance rapidly decreased in the case of samples with vitrinite reflectance higher than 0 7 rr perylene compound disappeared completely benzo a pyrene is also thermally unstable at elevated temperatures and its relative concentration is very low above vitrinite reflectance values of ca 0 9 such results could have important palaeoenvironmental implications if these five ring polycyclic aromatic hydrocarbon compounds are characterized by low to moderate thermal stability then their use as a wood degrading fungi tracer in the case of perylene and palaeo wildfire indicator in the case of benzo a pyrene is limited only to samples of maturation below the oil window range and below the major phase of oil generation respectively these results explain the scarcity of perylene in palaeozoic sedimentary rocks which are generally of higher maturation than the younger deposits

the lithosphere asthenosphere boundary in the tien shan karakoram region from s receiver functions evidence for continental subduction 1 significant s to p converted wave energy from the crust mantle and lithosphere asthenosphere boundaries the moho and the lab respectively has been observed in the tien shan and karakoram orogenic belts and used for the determination of the thickness of the crust and the mantle lithosphere the moho lies at depths of 45 65 km in the tien shan and adjacent regions and deepens to 70 km depth in pamir and karakoram the thickness of the lithosphere varies between 90 and 120 km underneath the tien shan and increases to a value of 160 km beneath the tarim basin to the south of the tarim basin the lower boundary of the asian lithosphere can be clearly followed to a depth of 270 km beneath central pamir and karakoram while the indian lithosphere is observed beneath the karakoram dipping from 130 km to 170 km towards the north the observations indicate a scenario of continental collision and subduction consistent with seismicity and the surface wave tomography results

mantle discontinuity structure beneath the colorado rocky mountains and high plains analysis of mantle discontinuity structure using converted p to s pas phases beneath colorado from the program for array seismic studies of the continental lithosphere passcal rocky mountain front rmf experiment reveals significant topography at the 410 and 660 km depth discontinuities and corresponding transition zone thickness variations a stack of all radial receiver functions resolves the 410 and 660 km discontinuities at average depths of 419 and 677 km respectively imaging of lateral variations in mantle discontinuity structure is accomplished by geographically binning the pds conversion points and then stacking the receiver functions in each bin to form spatial images analogous to common depth point stacking corrections for lateral velocity heterogeneity are calculated using the local s wave tomographic model of lee and grand 1996 and a constant lnvs lnvp scaling of 1 3 this scaling value is determined from the relative scaling between teleseismic p and s wave travel time residuals measured from the rocky mountain front deployment mantle discontinuity images using 150 km square bins show 20 km of 410 km discontinuity topography 30 km of 660 km discontinuity topography and up to 40 km of transition zone thickness variation features of the discontinuity structure include a 20 km depression of the 660 km discontinuity beneath western colorado and a gradual 10 km dip of the 410 km discontinuity beneath the high plains the thickening of the transition zone beneath southwest colorado is consistent with the presence of the subducted farallon slab in this region as imaged by van der lee and nolet 1997 in general our results show that the transition zone discontinuity structure is more complex than that predicted by the simple model of olivine phase boundaries modulated by vertically coherent thermal anomalies

unraveling the geometry of the farallon plate synthesis of three dimensional imaging results from usarray abstract we compare 12 recent three dimensional 3d seismic imaging results that made extensive use of data from the earthscope transportable array ta our goal is to sort out what can be said about the geometry of the farallon plate our main approach is 3d visualization using a kinematic plate motion model as a framework comparison of results from all 12 image volumes indicates that the results are most consistent with a single coherent farallon slab overridden by north american the farallon can be tracked from the trench in the pacific northwest to its remnants in the lower mantle under eastern north america from the trench the lithosphere has a low dip to the volcanic arc immediately east of the arc the slab steepens sharply before undergoing a decrease in dip above the 410 km discontinuity the gently dipping section varies along strike under washington the deflection is minor but to the south the slab flattens to become nearly horizontal beneath southern idaho there is a strong agreement that the high velocity anomaly associated with the slab vanishes under eastern oregon scattered wave imaging results however suggest the top of the anomaly is continuous these can be reconciled if one assumes the wavespeed anomaly has been neutralized by processes linked to the yellowstone system we find that all results are consistent with a 4d kinematic model of the mendocino slab window under nevada and utah in the eastern us the larger scale models all show a lower mantle anomaly related to the older history of farallon subduction the link between the lower mantle and new results in the u s cordillera lies under the high plains where the required usarray coverage is not yet complete image volumes in a unified format are supplied in an electronic supplement

changes of six selected glaciers in the tomor region tian shan central asia over the past 50 years using high resolution remote sensing images and field surveying as the major water resource of the tarim river glaciers in the tomor region have suffered major losses of ice in the last several decades based on topographic maps high resolution remote sensing image field survey data and previous studies changes of the six selected glaciers in the tomor region qingbingtan glacier no 72 qingbingtan glacier no 74 keqikekuzibayi glacier tomor glacier keqikar glacier and qiongtailan glacier over the past similar to 50 years were analyzed in this study analysis shows that all of the six glaciers showed continuous shrinkage the reduction rate of glacier no 72 terminus retreat of 41 m a 1 and area loss of 21 5 during 1964 2009 was higher than the others with a dramatically increased rate this dramatic ice thinning related glacier front retreat and area loss of the six glaciers suggests that glaciers in the tomor region might currently be suffering negative mass balance in response to the ongoing temperature rise differences in changes of the six glaciers are influenced by debris cover and other topographical factors c 2013 elsevier ltd and inqua all rights reserved

environmental significance and hydrochemical processes at a cold alpine basin in the qilian mountains isotope geochemistry of precipitation river water well water and spring water in the babao river basin china during different seasons showed that regional runoff was dominated by precipitation in summer and autumn and by underground water in winter and spring the 18o and d values of precipitation and spring water displayed a clear altitude effect water from the main stream and tributaries displayed a converse altitude effect in the summer wet season the isotopic composition of the various water sources was not well correlated with elevation during the winter dry season the spatial distribution of the stable isotope signals of river water demonstrated the influence of rainfall inputs evaporation and variable flow an end member mixing model used for hydrograph separation indicated that in the summer wet season the babao river water was recharged by precipitation 71 9 spring water 11 7 and well water 16 4 whereas the winter dry season recharge was sourced from spring water 28 2 and well water 71 8

geochemical characterization of the upper mississippian goddard formation noble ranch group and related oils in the anadarko basin of oklahoma the woodford shale is anecdotally assumed to be the major source of oil for plays in the anadarko basin including the stacked oil and condensate play in the southcentral oklahoma oil province scoop however there is little published geochemical work to confirm this assumption this study set out to identify a characteristic geochemical fingerprint for the goddard formation another potential source rock in the scoop to determine if the goddard is contributing to oil accumulations within the scoop the upper mississippian goddard formation has been a target for unconventional production in scoop since 2012 published geochemical interpretations for the goddard formation are still limited and this study represents the first detailed oil source rock correlation for the goddard in the scoop area the most characteristic geochemical signature of the goddard extracts is a predominance of tricyclic terpanes relative to the hopanes in the mass to charge ratio 191 chromatogram possibly related to enrichment via thermal stress or a unique source signature additional distinctive signatures were also identified for the triaromatic steroid hydrocarbons sesquiterpenoids and steranes the biomarker fingerprints of scoop oils are nearly identical with those of the goddard extracts in this study oils in the scoop therefore appear to originate from a mississippian source such as the goddard rather than the woodford this observation demonstrates the value of oil source rock correlation studies and suggests that there may be effective source rocks in the anadarko basin that have been overlooked in the past and should be re evaluated in detail

a ubiquitous low velocity layer at the base of the mantle transition zone global stacks of receiver functions clearly exhibit the upper mantle stratification besides the most prominent seismic discontinuities such as the moho and the 410 and 660 km discontinuities a negative discontinuity is detected at a depth of 600 km indicating a low velocity layer at the base of the mantle transition zone the slant slack technique helps to identify the primary conversions from the multiple reverberations presence of the negative 600 km discontinuity underneath both continent and ocean island stations where the crustal thickness significantly differs also precludes the possible cause of crustal reverberations we conclude that the negative 600 km discontinuity could be a global feature possibly resulted from accumulation of ancient subducted oceanic crust the x discontinuity at 300 km depth is also observed in our global stacks which can be explained by the coesite stishovite phase transformation

a six hundred year annual minimum temperature history for the central tibetan plateau derived from tree ring width series the recent unprecedented warming found in different regions has aroused much attention in the past years how temperature has really changed on the tibetan plateau tp remains unknown since very limited high resolution temperature series can be found over this region where large areas of snow and ice exist herein we develop two juniperus tibetica kom tree ring width chronologies from different elevations we found that the two tree ring series only share high frequency variability correlation response function and partial correlation analysis indicate that prior year annual january december minimum temperature is most responsible for the higher belt juniper radial growth while more or less precipitation signal is contained by the tree ring width chronology at the lower belt and is thus excluded from further analysis the tree growth climate model accounted for 40 of the total variance in actual temperature during the common period 1957 2010 the detected temperature signal is further robustly verified by other results consequently a six century long annual minimum temperature history was firstly recovered for the yushu region central tp interestingly the rapid warming trend during the past five decades is identified as a significant cold phase in the context of the past 600 years the recovered temperature series reflects low frequency variability consistent with other temperature reconstructions over the whole tp region furthermore the present recovered temperature series is associated with the asian monsoon strength on decadal to multidecadal scales over the past 600 years

new insights into the origin of perylene in geological samples abstract the origin of the polycyclic aromatic hydrocarbon pah perylene in sediments and petroleum has been a matter of continued debate reported to occur in phanerozoic organic matter om fossil crinoids and tropical termite mounds its mechanism of formation remains unclear while a combustion source can be excluded structural similarities to perylene quinone like components present in e g fungi plants crinoids and insects potentially suggest a product precursor relationship here we report perylene concentrations 13c 12c and d h ratios from a holocene sediment profile from the qingpu trench yangtze delta region china perylene concentrations differ from those of pyrogenic pahs and rise to prominence in a stratigraphic interval that was dominated by woody vegetation as determined by palynology including fungal spores in this zone perylene concentrations exhibit an inverse relationship to the lignin marker guaiacol d h ratios between 284 and 317 similar to the methoxy groups in lignin as well as co variation with spores from wood degrading fungi 13c 12c of perylene differs from that of land plant wax alkanes and falls in the fractionation range expected for saprophytic fungi that utilise lignin which is isotopically lighter than cellulose and whole wood during progressive lignin degradation the relative carbon isotopic ratio of the perylene decreases we therefore hypothesise a relationship of perylene to the activity of wood degrading fungi to support our hypothesis we analysed a wide range of phanerozoic sediments and oils and found perylene to generally be present in subordinate amounts before the evolutionary rise of vascular plants and to be generally absent from marine sourced oils few exceptions being attributed perhaps to a contribution of marine and or terrestrial derived fungi anoxia especially under marine conditions and or contamination of core material by fungi a series of low molecular weight aromatic quinones bearing the perylene backbone were detected in devonian and cretaceous sediments potentially representing precursor components to perylene

probable fungal origin of perylene in late cretaceous to paleogene terrestrial sedimentary rocks of northeastern japan as indicated from stable carbon isotopes abstract perylene is present in high concentration in paleogene sediments from the sanriku oki borehole of the ministry of international trade and industry miti northeastern japan the borehole penetrates a thick sequence of late cretaceous to neogene sediments deposited under a range of conditions including fluvial deltaic and shallow marine organic petrological and geochemical data show the sediments to be rich in organic matter om derived from higher plants biomarker analysis of aliphatic and aromatic hydrocarbons confirms a significant input from higher plants with extracts dominated by numerous gymnosperm and angiosperm derived biomarkers such as diterpanes oleanenes des a triterpanes and their aromatized counterparts the highest concentration of perylene occurs in middle eocene sediments deposited in a relatively reducing environment stable carbon isotope compositions show 13 c enrichment in perylene compared to gymnosperm and angiosperm biomarkers consistent with a fungal origin this elevated abundance of sedimentary perylene could relate to a paleogene continental climate where fungi probably flourished

changes of the hailuogou glacier mt gongga china against the background of climate change during the holocene large changes have occurred at hailuogou glacier mt gongga china during the holocene various data indicate that it retreated by 1 88 km during the 20th century and mass balance records show that it suffered a sustained mass loss of snow and ice in the period 1959 60 2003 04 with an accumulated mass balance of 10 83 m water equivalent hydrological data demonstrate that runoff from the glacier has been increasing both seasonally and annually the principal cause being an increase of ice and snow melt water as the mean temperature in the hailuogou basin rose by 0 1 degrees c between 1994 and 2004 the runoff increased by 2 6 m 3 s 1 changes of glacier morphology which occurred during this period include a decrease of thickness enlargement of glacial caves and reduction of the size of seracs the hailuogou glacier advanced three times during the little ice age in response to three cold periods in the mt hengduan region there also were three noticeable advances in the neoglacial there was a very clear relationship between glacier change climate change and forest line change in the period 3000 a bp 100 a bp overall it is clear that changes of the hailuogou glacier in the holocene have been responded to climatic fluctuations but quantitative evaluation of the relationship is difficult owing to the sparse spatial coverage of reliable evidence and the limited available longer term data c 2008 elsevier ltd and inqua all rights reserved

global seismic data reveal little water in the mantle transition zone abstract knowledge of the earth s present water content is necessary to constrain the amount of water and other volatiles the earth acquired during its formation and the amount that is cycled back into the interior from the surface this study compares 410 and 660 km discontinuity depth with shear wave tomography within the mantle transition zone to identify regions with seismic signals consistent with water the depth of the 410 and 660 km discontinuities is determined from a large updated dataset of ss s410s and ss s660s differential travel times known as ss precursors the discontinuity depths measured from binning and stacking the ss precursor data are then compared to the shear velocity model hmsl s06 in the transition zone mapping all the possible combinations very few locations match the predictions from mineral physics for the effects of water on discontinuity depth and shear velocity the predictions although not yet measured at actual transition zone temperatures and pressures are a shallow 410 km discontinuity a deep 660 km discontinuity and a slow shear velocity only 8 of the bins with high quality data are consistent with these predictions and the calculated average water content within these bins is around 0 6 wt a few isolated locations have patterns of velocity topography that are consistent with water while there are large regional scale patterns consistent with cold hot temperature anomalies combining this global analysis of long period seismic data and the current mineral physics predictions for water in transition zone minerals i find that the mantle transition zone is generally dry containing less than one earth ocean of water although subduction zones could be locally hydrated the combined discontinuity and velocity data show no evidence that wadsleyite or ringwoodite have been globally hydrated by subduction or initial earth conditions

climatic and topographic controls on the style and timing of late quaternary glaciation throughout tibet and the himalaya defined by 10be cosmogenic radionuclide surface exposure dating abstract temporal and spatial changes in glacier cover throughout the late quaternary in tibet and the bordering mountains are poorly defined because of the inaccessibility and vastness of the region and the lack of numerical dating to help reconstruct the timing and extent of glaciation throughout tibet and the bordering mountains we use geomorphic mapping and 10 be cosmogenic radionuclide crn surface dating in study areas in southeastern gonga shan southern karola pass and central western nyainqentanggulha shan and tanggula shan tibet and we compare these with recently determined numerical chronologies in other parts of the plateau and its borderlands each of the study regions receives its precipitation mainly during the south asian summer monsoon when it falls as snow at high altitudes gonga shan receives the most precipitation 2000 mm a 1 while near the margins of monsoon influence the karola pass receives moderate amounts of precipitation 500 600 mm a 1 and in the interior of the plateau little precipitation falls on the western nyainqentanggulha shan 300 mm a 1 and the tanggula shan 400 700 mm a 1 the higher precipitation values for the tanggula shan are due to strong orographic effects in each region at least three sets of moraines and associated landforms are preserved providing evidence for multiple glaciations the 10 be crn surface exposure dating shows that the formation of moraines in gonga shan occurred during the early mid holocene neoglacial and little ice age on the karola pass during the lateglacial early holocene and neoglacial in the nyainqentanggulha shan date during the early part of the last glacial cycle global last glacial maximum and lateglacial and on the tanggula shan during the penultimate glacial cycle and the early part of the last glacial cycle the oldest moraine succession in each of these regions varies from the early holocene gonga shan lateglacial karola pass early last glacial western nyainqentanggulha shan and penultimate glacial cycle tanggula shan we believe that the regional patterns and timing of glaciation reflect temporal and spatial variability in the south asian monsoon and in particular in regional precipitation gradients in zones of greater aridity the extent of glaciation has become increasingly restricted throughout the late quaternary leading to the preservation of old 100 ka glacial landforms in contrast in regions that are very strongly influenced by the monsoon 1600 mm a 1 the preservation potential of pre lateglacial moraine successions is generally extremely poor this is possibly because lateglacial and holocene glacial advances may have been more extensive than early glaciations and hence may have destroyed any landform or sedimentary evidence of earlier glaciations furthermore the intense denudation mainly by fluvial and mass movement processes which characterize these wetter environments results in rapid erosion and re sedimentation of glacial and associated landforms which also contributes to their poor preservation potential

intraplate volcanism due to convective instability of stagnant slabs in the mantle transition zone the study of volcanism can further our understanding of earth s mantle processes and composition continental intraplate volcanism commonly occurs above subducted slabs that stagnate in the mantle transition zone mtz such as in europe eastern china and western north america here we use two dimensional numerical models to explore the evolution of stagnant slabs in the mtz and their potential to sustain mantle upwellings that can support volcanism we find that weak slabs may go convectively unstable within tens of million years upwellings rise out of the relatively warm underbelly of the slab are entrained by ambient mantle flow and reach the base of the lithosphere the first and most vigorous upwellings rise adjacent to lateral heterogeneity within the slab ultimately convective instability also acts to separate the compositional components of the slab harzburgite and eclogite from each other with harzburgite rising into the upper mantle and eclogite sinking into the lower mantle such a physical filtering process may sustain a long term compositional gradient across the mtz

three dimensional prestack plane wave migration of teleseismic p to s converted phases 2 stacking multiple events 1 in part 1 we developed the theoretical foundations of a prestack migration procedure to image forward scattered p to s pds converted waves in the coda of teleseismic p waves this paper addresses the issue of how to optimally stack data from multiple events migrated by this procedure we apply matrix perturbation theory to develop an objective way to quantify noise in deconvolved pds data application of the theory demonstrates that an optimal stack requires weighting the migrated data from each event by a signal to noise ratio criterion we also find that the migrated pds images have to be binned by back azimuth and balanced prior to the final stack this is necessary to mitigate coherent noise that results from aliased microseism noise that is enhanced by our processing method we processed 23 events recorded by the lodore array in northwestern colorado with our procedure the results indicate the presence of a major lithospheric scale discontinuity defined by a south dipping boundary within the crust that we interpret as the subsurface expression of the cheyenne belt the suture is also marked by a transition in crustal thickness from 35 km on the archean side to over 40 km on the colorado plateau side we also observe a strong difference in the lithospheric mantle pds conversion signature on opposite sides of the suture that suggests delamination and northward convergence of the colorado lithosphere beneath the wyoming province

crustal structure of the indian shield new constraints from teleseismic receiver functions teleseismic earthquake waveform data from 10 broadband stations spread over the indian shield and in operation since 1997 were analyzed to infer the crustal structure using the receiver function technique the south indian shield is characterized by a 33 39 km thick and remarkably simple crust with an average poisson s ratio close to 0 25 the archaean crust is devoid of any prominent intra crustal discontinuities the velocity contrast at the well developed moho is large resulting in very clear p to s conversions as well as first order multiples in contrast the predominantly proterozoic crust in the northern part of the shield exhibits a complex character due to the presence of additional seismic discontinuities moho conversions which are considerably weaker compared to the archaean terrains indicate crustal thicknesses of more than 40 km

biomarker and stable carbon isotope systematics of fossil wood from the second lusatian lignite seam of the lubstow deposit poland abstract decay of fossil wood gelification collected from the middle miocene 2nd lusatian lignite seam at the lubstow open cast mine poland is characterised by its maceral variety fluorescence intensity and cellulose content cellulose decomposition leads to lower molar h c ratio values of the organic matter as indicated by higher total organic carbon toc content of samples characterised by low cellulose content biochemical formation of hydrocarbons in the wood due to enhanced microbial activity is evidenced by higher hydrocarbon content in the extracts higher relative proportions of n alkanes and hopanoids are observed in the hydrocarbon fractions of wood remains characterised by low cellulose yield the results provide evidence for the formation of these compounds during biogeochemical transformation of organic matter hopanoid contents are considered to reflect the activity of aerobic bacteria and or fungi because of enhanced perylene content in the hydrocarbon fractions from gelified wood samples fungi are considered as the major precursor carriers of this polycyclic aromatic hydrocarbon the results provide evidence that biomarker composition of fossil wood can be used to trace biochemical transformation processes chemotaxonomical classification of fossil wood fragments as gymnosperms most probably species of the coniferales families taxodiaceae cupressaceae are based on the molecular composition of terpenoid hydrocarbons and a mean 13 c value of 24 5 depletion of gelified samples in 13 c as compared to ungelified wood is caused by the effect of progressive decomposition of cellulose the data indicate that cellulose 13 c data mean 13 c 20 8 are also affected by wood decomposition and so only samples with comparable cellulose content should be used for the reconstruction of environmental changes inter species as well as intra plant variation in carbon isotope differences and of decay resistance between cellulose and lignin have to be taken into account

origin of organic matter from tectonic zones in the western tatra mountains crystalline basement poland an example of bitumen source rock correlation abstract solid bitumens of unknown origin found in brittle tectonic shear zones cutting the crystalline basement of the western tatra mts show uniform geochemical characteristics that suggest a uniform source for the original hydrocarbons on the basis of gc ms data a similarity between these solid bitumens and organic matter dispersed in the mesozoic source rocks of podhale trough and sedimentary cover of the northern tatra mts is observed the organic matter in the mesozoic source rocks shows a higher maturation level than that in the solid bitumens the molecular composition of the organic matter in both the solid bitumens and the basement rocks is significantly different from that in the paleogene sedimentary rocks infilling the podhale trough these immature to early mature paleogene sedimentary rocks contain organic compounds typical of terrestrial plants both conifers simonellite and retene and angiosperms lupane oleanane and taraxastene which are absent in the solid bitumens and in the mesozoic source rocks water co2 fluid inclusions in quartz sealing the shear zones have marine like salinity a dominance of cacl2 and mg2 depletion suggesting genetic affinity to dolomitised carbonate rocks such as potential middle triassic source rocks the low maturity of the solid bitumen in the shear zones relative to its mesozoic source can be explained by continued maturation of the mesozoic source rocks after expulsion and migration into the shear zones the results of hydrocarbon generation modeling indicate that oil expulsion from the mesozoic source rocks its migration through the shear zones and the subsequent maturation of the mesozoic source rocks all occurred within a short oligocene time interval

roughness of the mantle transition zone discontinuities revealed by high resolution wavefield imaging we processed two independent data sets 2 458 973 three component seismograms from all earthscope transportable array usarray stations and 141 080 pairs of high quality receiver functions from the earthscope automated receiver survey using the generalized iterative deconvolution method and shaped the output with a 0 1 hz ricker wavelet we used these data as input to our 3 d plane wave migration method to produce an image volume of p to s scattering surfaces under all of the lower 48 states model simulations show that compared to the widely used common conversion point stacking method our method is capable of resolving not only dipping discontinuities but also subtler details of amplitude and topography variations at scales near the diffraction limit maps of attributes derived from these discontinuities reveal several previously unobserved features of the 410 and 660 discontinuities d410 and d660 topography with many tens of kilometers is resolved at a range of scales additionally we observed large variations of amplitude on the radial component and in the radial to transverse amplitude ratio that correlate with inferred variations in discontinuity topography we argue that this combination of observations can be explained by roughness at a range of scales the structural fabric we imaged is preferentially aligned orthogonal to the farallon north american relative motion two regions we infer to have exceptional roughness show spatial correlation with locations where tomography models indicate that the subducted slab is passing through the transition zone we suggest that these rough regions are indicators of vertical mantle flows through the transition zone

imaging the colliding indian and asian lithospheric plates beneath tibet 1 a high resolution image of the base of the lithosphere from s to p converted seismic waves revealed the collision architecture of the indian and asian continental plates beneath the tibetan plateau the base of the indian lithosphere dips northward from a depth of 160 km beneath the himalayas to a depth of 220 km just south of the bangong suture the base of the asian lithosphere is nearly horizontal at the depth of 160 180 km from central to northern tibet there is a vertical gap of about 50 km between indian and asian lithospheres our observation of a well defined thick lithosphere throughout the entire plateau is not consistent with models of wholesale convective instability of a thickened mantle lithosphere which would predict a very thin asian lithosphere the hypothesized sequential southward subduction of tibetan and asian continental lithospheres leading to the growth of the tibetan plateau if correct cannot be occurring below 180 km depth our results along with available geological and geophysical data strongly support that the plateau is predominantly formed by a relatively coherent north dipping subducted indian continental lithosphere in the south which presently can be traced to the middle of the plateau and a south dipping subducted asian lithosphere in the north at a shallower depth

multiple transition zone seismic discontinuities and low velocity layers below western united states with p to s converted waves recorded at seismic stations of the us transportable array we image the fine structure of upper mantle and transition zone tz beneath the western us we map the topographies of seismic discontinuities by stacking data by common conversion points along profiles systematic depth and amplitude measurements are performed not only for the well known 410 and 660 interfaces but also for minor seismic discontinuities identified around 350 590 and 630 km depths the amplitude of conversion suggests shear wave velocity vs increase by 4 at the 410 and the 660 the observed 660 velocity contrast is smaller than expected from the 6 in iasp91 but consistent with a pyrolitic model of mantle composition the gorda plate subducted under northern california is tracked to the tz where it seems to flatten and induce uplift of the 410 under northern nevada maps of 410 660 amplitude topography reveal that the tz is anomalous beneath the geographical borders of washington oregon and idaho with i a thickened tz ii a sharp change in depth of the 660 iii a reduced 410 conversion amplitude in the north and iv a positive 630 discontinuity such anomalous structure might be inherited from the past history of plate subduction accretion a thinned tz under the yellowstone suggests higher than average temperatures perhaps due to a deep thermal plume both the 350 and the 590 negative discontinuities extend over very large areas they might be related either to an increased water content in the tz a significant amount of oceanic material accumulated through the past 100 my or both

responses of two branches of glacier no 1 to climate change from 1993 to 2005 tianshan china abstract clear understanding of how alpine glaciers respond to climate change is critical to accurately evaluate water resources and to retrieve climate information from the alpine glaciers however different glaciers may have different responses to climate change this study focuses on two branches of glacier no 1 at the head of urumqi river tianshan china these two branches west branch wb and east branch eb have experienced the same pattern of climate warming since their separation in 1993 however these glaciers have responded differently as observed by fieldwork and analysis of their annual mass balances lengths areas equilibrium line altitudes elas to illustrate the different responses of climate change increase in both temperature and precipitation the glacier length response time t rl and climate sensitivity c are calculated for the two branches the length response time and climate sensitivity are 1 89 y and 8 81 for the eb and 1 63 y and 5 92 for wb the different responses are interpreted to be controlled by glacial topographical features with larger slopes and smaller areas making the wb more sensitive to the recent climate warming

tree ring recorded may august temperature variations since a d 1585 in the gaoligong mountains southeastern tibetan plateau abstract high resolution proxy data are still scarce in the southeastern tibetan plateau which limit our understanding of climatic variability before instrumental records in this study we developed 595 year tree ring width chronology from larix speciosa near the timberlines of the gaoligong mountains southeastern tibetan plateau ring width site chronologies and a well replicated regional chronology rc showed significant positive correlations with warm season temperatures from may to august using rc as predictor we reconstructed mean may august temperature for the study region that extends back to a d 1585 cold conditions prevailed during the periods 1600s 1620 30 1640 50s 1700s 1730 40s 1760s 1810 20s 1850s 1900 10s and 1955 70 warm episodes occurred during 1610s 1660 1680s 1710 20s 1750s 1780 90s 1820 40 1920 50 and 1980 present spatial correlations with gridded land surface temperatures revealed that our reconstruction represents regional temperature signal for the southern tibetan plateau comparison with other tree ring based temperature reconstructions from surrounding areas implies a high degree of confidence for our reconstruction

seismic discontinuities in the mantle transition zone and at the top of the lower mantle beneath eastern china and korea influence of the stagnant pacific slab we have analyzed broadband data to identify and determine mantle discontinuities in the mantle transition zone mtz beneath eastern china where the pacific slab is stagnant the depths of the 410 and 660 km discontinuities are generally shallower and deeper respectively than the global averages in and near the pacific slab beneath eastern china the mtz is thicker in the slab than the global average this observation is consistent with the thermally controlled olivine to wadsleyite transformation for the 410 km discontinuity and the post spinel transformation for the 660 km discontinuity other discontinuities appear from 690 to 750 km in the lower mantle part of the pacific slab recent mineralogical experiments indicate that the most plausible interpretation of these deep discontinuities is that they represent the ilmenite to perovskite transformation in a cold environment such as that in the pacific slab

perylene as an indicator of conifer fossil wood degradation by wood degrading fungi the occurrence of perylene in middle jurassic fossil wood and miocene xylites from poland is described along with its correlation with unsubstituted polycyclic aromatic hydrocarbons pahs as well as cellulose content both middle jurassic and miocene wood remnants were of relatively low maturity ca 0 2 0 3 vitrinite reflectance rr had excellent preservation of biomarkers and biomolecules and in the case of the middle jurassic fossil wood samples generally good preservation of anatomical structures due to early diagenetic mineralisation the results from 42 middle jurassic and 8 miocene most taxonomically defined fossil wood fragments demonstrated a negative correlation between the concentration of perylene and those of generally typical conifer biomarkers e g cadalene dehydroabietane simonellite and retene in addition good correlation r2 0 81 was observed between the ratio of perylene to the above conifer biomarkers and the ratio of pahs phenanthrene and fluoranthene and pyrene to the conifer biomarkers this implies that the high concentration of perylene in fossil wood indicate its extensive degradation during decay transport and early diagenesis we defined a conifer wood degradation index as cwdi perylene perylene cadalene retene simonellite dehydroabietane cwdi perylene perylene cadalene retene simonellite dehydroabietane and observed a wide range of values 0 001 for less degraded wood to 0 95 for highly degraded samples anatomical wood preservation was associated with cwdi values in most of the samples characterised by poorly preserved anatomy high cwdi values were observed while anatomically well preserved samples generally had lower cwdi values we determined similar 13c values for perylene from the fossil wood samples 26 4 to 27 8 whereas the values for the conifer biomarkers were slightly higher and varied from 25 6 to 26 6 in contrast pyrene was depleted in 13c 27 5 to 28 2 the carbon isotope values of perylene are consistent with an origin from wood degrading fungi

extracting a climate signal from 169 glacier records i constructed a temperature history for different parts of the world from 169 glacier length records using a first order theory of glacier dynamics i related changes in glacier length to changes in temperature the derived temperature histories are fully independent of proxy and instrumental data used in earlier reconstructions moderate global warming started in the middle of the 19th century the reconstructed warming in the first half of the 20th century is 0 5 kelvin this warming was notably coherent over the globe the warming signals from glaciers at low and high elevations appear to be very similar

significance of polycyclic aromatic hydrocarbons pahs in permian triassic boundary sections abstract in this study the abundances of several polycyclic aromatic hydrocarbons pahs table 1 i xxi have been measured throughout three permian triassic p tr sections from meishan south china kap stosch area east greenland and peace river basin western canada dibenzothiophene i and dibenzofuran ii were found to decrease in abundance just before or shortly after the p tr transition in all three sections while perylene iii was observed to increase in abundance at the onset of the main extinction horizon bed 25 in meishan perylene has been attributed to a wood degrading fungal source and therefore it seems possible these phenomena are related to the demise of land plants further distinct patterns of various combustion derived pahs occurring in each section imply that forest fire events occurred within the late permian and early triassic in the meishan section high amounts of combustion derived pahs pyrene iv fluoranthene v benzo a anthracene vi benzofluoranthenes sum i e vii benzo a pyrene viii benzo e pyrene ix and coronene x occur within bed 25 also containing ash attributed to the fallout from massive volcanic eruptions in siberia and or china

sound velocities of hydrous ringwoodite to 16 gpa and 673 k article i nfo 0 026 si1 00h0 179o4 with 1 1 wt h2o using brillouin scattering combined with x ray diffraction in an externally heated diamond anvil cell up to 16 gpa and 673 k up to 12 gpa at 300 k the presence of 1 1 wt h2o lowers the elastic moduli of ringwoodite by 5 9 but does not affect the pressure derivatives of the elastic moduli compared to anhydrous ringwoodite the reduction caused by hydration is significantly enhanced when temperatures are elevated at high pressures at 12 gpa increasing temperature by t 100 k leads to a 1 3 2 4 reduction in the elastic moduli c11 c12 and c14 comparing our results with seismic observations we have evaluated the potential h2o content in the lower part of the transition zone our results indicate that the observed seismic velocity anomalies and related depth depression of the 660 km discontinuity could be attributed to thermal variations together with the presence of 0 1 wt h2o 2012 elsevier b v all rights reserved

stagnant slab wet plumes and cenozoic volcanism in east asia abstract data from seismology and mineral physics indicate the existence of low velocity zones in the deep part of the upper mantle wedge and the mantle transition zone under east asia zhao and ohtani 2009 zhao et al 2009 it suggests a link between the deep subduction and stagnation and deep dehydration of the pacific slab below this area and the cenozoic volcanism observed at the surface here we present a numerical model describing the dynamics of a hydrated layer covering a slab that is stagnating in the earth tm s mantle transition zone specifically our model includes the effects of water on density and viscosity of the mantle minerals we conclude that the presence of water is likely to induce rayleigh taylor type instabilities wet plumes that are able to transport water up to the base of the surficial lithosphere in a relatively short time scale a few million years under initial conditions representative of the subducting pacific slab under east asia melting is induced where wet plumes reach the base of the lithosphere according to our results and analysis of the known composition of cenozoic basalts from southwest japan iwamori 1991 iwamori 1992 wet plumes and their melting induced by water related to the stagnant slab provides an appealing hypothesis to explain cenozoic volcanism in east asia

controls on the deep water cycle within three dimensional mantle convection models earth s mantle is known to harbor water in the form of hydrous and nominally anhydrous minerals how much water the mantle holds and whether it has remained constant through time are open questions previous numerical studies of the deep water cycle have been limited to box models or 2 d calculations here we present for the first time results from 3 d mantle convection models we address the evolution of the mantle s total water content by adapting a well benchmarked mantle convection code to track water including its feedbacks on dynamics while earth s surface is presently covered by one ocean mass of water our results suggest that the mantle holds approximately two ocean masses of water based on the best estimates from mineral physics this value varies only weakly for a wide parameter space of additional complex dynamics such as viscosity laws density controls and phase change considerations our result of a mantle holding two ocean masses conforms with estimates from other branches of earth science suggesting that these models could be an excellent tool in understanding the spatial heterogeneity of the water found in the mantle

mantle discontinuity structure beneath the southern east pacific rise from p to s converted phases receiver functions derived from teleseismic body waves recorded by ocean bottom seismometers on the southern east pacific rise reveal shear waves converted from compressional waves at the mantle discontinuities near 410 and 660 kilometer depth the thickness of the mantle transition zone between the two discontinuities is normal relative to the global average and indicates that upwelling beneath the southern east pacific rise is not associated with an excess temperature in the mantle transition zone

insights into the origin of perylene from isotopic analyses of sediments from saanich inlet british columbia perylene is an abundant and common polycyclic aromatic hydrocarbon in sedimentary settings yet its origin remains puzzling we have investigated the relation of perylene to the amount and type of organic matter in the sediments of saanich inlet a coastal marine anoxic basin organic matter is predominantly marine in origin but the proportions of marine and land derived components have varied perylene concentrations generally increase with sediment depth relative to toc which indicates continued formation of this compound by microbially mediated diagenesis perylene 13c values range between 27 7 and 23 6 whereas toc 13c values vary narrowly from 21 7 to 21 2 over the same sediment depth interval the variation in isotopic difference suggests that perylene originates from more than one precursor material both aquatic and continental organic matter different microbial processes or some combination of these possibilities

the upper mantle transition zone beneath the ibero maghrebian region as seen by teleseismic pds phases abstract we investigate the upper mantle transition zone thickness beneath the ibero maghrebian region using teleseismic events recorded at 258 seismic stations from the iberarray of the spanish topoiberia project for this purpose the 410 km and 660 km depth discontinuities are mapped through the detection of p to s conversions in order to add consistency and robustness to the detections the final results are based on a joint analysis of receiver functions and two different cross correlation functionals discontinuity depths are determined using time corrections obtained from a 3 d velocity model this study presents the first high resolution topography maps for the 410 and 660 discontinuities which show lateral variations in the transition zone thickness beneath the study area the results are discussed to add new constraints on temperature and composition to seismic velocity anomalies observed in the transition zone beneath the controversial ibero maghrebian region we obtained a thickened transition zone beneath the alboran sea and the north balearic sea suggesting low transition zone temperatures and coinciding with the position of the high velocity anomalies in the tomographic images related to the betic alboran slab and the alpine tethys remnant slab respectively a dominantly thinned transition zone beneath the gulf of cadiz and its surroundings suggest high mantle temperatures we also found evidences of the presence of a low velocity layer atop the 410 discontinuity beneath the study area

tree ring density inferred late summer temperature variability over the past three centuries in the gaoligong mountains southeastern tibetan plateau long and high resolution proxy records are still sparse in the southeastern tibetan plateau tp hampering our understanding of past climatic variability from a long term perspective in this study we developed a regional maximum latewood density mxd chronology of larix speciosa stretching up to 523 years based on 72 tree ring cores 44 trees collected from three sites close to the tree line in the gaoligong mountains southeastern tp this chronology responded well to temperatures during august through september and was thus used to reconstruct late summer august september temperature over the period a d 1690 2008 the reconstruction explains 40 9 of the total temperature variance during the calibration phase cold conditions prevailed during the periods 1695 1702 1806 1821 the 1850s 1882 1889 the 1900s and the 1960s warm phases occurred in 1734 1745 the 1770s 1824 1840 the 1890s 1927 1936 the 1940s 1950s and 2002 2008 spatial correlation with the gridded temperature data set showed that our reconstruction captures large scale regional temperature variations for the southeastern and southern tp comparison with other tree ring inferred temperature time series in the surrounding areas glacier fluctuations and historical documental records imply a high degree of confidence for our reconstruction c 2015 elsevier b v all rights reserved

imaging the earth with passive seismic arrays earthquake and exploration seismology share a common foundation in elastic wave propagation most of what we know about earthquakes is known from the elastic waves they emit while seismic methods in exploration are all about using scattered elastic waves to image earth structure seismologists have been using elastic waves to probe the earth since the very earliest instruments after all it was early seismic measurements that led to the spherical shell model of earth structure crust mantle and core taught to grade school students

effect of hydration on the single crystal elasticity of fe bearing wadsleyite to 12 gpa the single crystal elastic properties of fe bearing wadsleyite with 1 93 wt h2o mg1 634fe0 202h0 305sio4 have been determined by brillouin scattering at ambient conditions the aggregate bulk and shear moduli ks0 g0 of this wadsleyite are 156 2 5 and 98 0 3 gpa respectively compared to the corresponding anhydrous wadsleyite 1 93 wt h2o lowers ks0 and g0 by 8 1 and 9 3 respectively high pressure measurements up to 12 gpa show that the pressure derivative of

mantle transition zone shear velocity gradients beneath usarray broadband p to s scattering isolated by teleseismic receiver function analysis is used to investigate shear velocity v s gradients in the mantle transition zone beneath usarray receiver functions from 2244 stations were filtered in multiple frequency bands and migrated to depth through p and s tomography models the depth migrated receiver functions were stacked along their local 410 and 660 km discontinuity depths to reduce stack incoherence and more accurately recover the frequency dependent amplitudes of p410s and p660s the stacked waveforms were inverted for one dimensional v s between 320 and 840 km depth first a gradient based inversion was used to find a least squares solution and a subsequent monte carlo search about that solution constrained the range of v s profiles that provide an acceptable fit to the receiver function stacks relative to standard references models all the acceptable models have diminished v s gradients surrounding the 410 a local v s gradient maximum at 490 500 km depth and an enhanced v s gradient above the 660 the total 410 v s increase of 6 3 is greater than in reference models and it occurs over a thickness of 20 km however 60 of this v s increase occurs over only 6 km the 20 km total thickness of the 410 and diminished v s gradients surrounding the 410 are potential indications of high water content in the regional transition zone an enhanced v s gradient overlying the 660 likely results from remnants of subduction lingering at the base of the transition zone cool temperatures from slabs subducted since the late cretaceous and longer term accumulation of former ocean crust both may contribute to the high gradient above the 660 the shallow depth of the 520 km discontinuity 490 500 km implies that the regional mean temperature in the transition zone is 110 160 k cooler than the global mean a concentrated v s gradient maximum centered near 660 km depth and a low v s gradient below 675 km confirms that the ringwoodite to perovskite magnesiowustite reaction is the dominant cause of the 660 in the region

the removal of free surface interactions from three component seismograms summary the effect of the free surface can be removed from three component seismic recordings to recover the incident upgoing wavefield if the slowness and azimuth of the current wavefront are known as a function of time for a single threecomponent station it is usually possible to estimate an azimuth for an event from the first arriving p waves but slowness estimates are less reliable when more than one wavetype is presented in the seismic wavetrain however the free surface correction operators are generally slowly varying functions of slowness and so some error in slowness can be tolerated effective approximations for the removal of the free surface effects can be made for hard rock sites to cover slowness bands for the main regional phases pn pg sn and lg by applying these operators in turn over group velocity windows appropriate to the particular phases the relative amplitude of the p sv and sh contributions to the wavefield can be estimated because the free surface amplification effects have been removed the amplitudes can be compared directly and provide useful constraints on the radiation characteristics of the source this procedure is therefore helpful for developing discrimination measures for different classes of sources

p and s wave tomography of the mantle beneath the united states mantle seismic structure beneath the united states spanning from the active western plate margin to the passive eastern margin was imaged with teleseismic p and s wave traveltime tomography including usarray data up to may 2014 to mitigate artifacts from crustal structure 5 40 s rayleigh wave phase velocities were used to create a 3 d starting model major features of the final p and s models include two distinct low velocity anomalies at depths of 60 300 km beneath the central and northern appalachians and passive margin the central appalachian low velocity anomaly coincides with eocene basaltic magmatism and the northern anomaly is located along the cretaceous track of the great meteor hot spot at depths of 300 700 km beneath the central and eastern u s large high velocity anomalies are inferred to be remnants of the farallon slab that subducted prior to 40 ma during the laramide orogeny

seismic evidence for water deep in earth s upper mantle water in the deep upper mantle can influence the properties of seismic discontinuities in the mantle transition zone observations of converted seismic waves provide evidence of a 20 to 35 kilometer thick discontinuity near a depth of 410 kilometers most likely explained by as much as 700 parts per million of water by weight

seismic shear wave reflectivity structure of the mantle beneath northeast china and the northwest pacific 1 using multiple scs reverberations we examine the mantle reflectivity structure beneath northeast china and the northwest pacific we find several upper mantle discontinuities including a melt layer with a mean thickness of 64 km atop the 410 km discontinuity present on both sides of the subducting slab near the nankai trench the transition zone contains a split 520 km discontinuity in several paths and tomographic images show stagnant slabs at this depth we believe that this may be slab related based on experimental work a negative reflector is found in one path beneath the northeast china craton at a depth of 598 km mid mantle reflectors are found in all of our paths and are present throughout a wide depth range 750 1600 km

seismic evidence for an ancient rift beneath the cumberland plateau tennessee a detailed analysis of broadband teleseismic p waveforms broadband receiver functions developed from teleseismic p waveforms recorded on the midperiod passband of regional seismic test network station rscp are inverted for vertical velocity structure beneath the cumberland plateau tennessee the detailed broadband receiver functions are obtained by stacking source equalizd horizontal components of teleseismic p waveforms the resulting receiver functions are most sensitive to the shear velocity structure near the station a time domain inversion routine utilizes the radial receiver function to determine this structure assuming a crustal model parameterized by many thin flat lying homogeneous layers lateral changes in structure are identified by examining azimuthal variations in the vertical structure the results reveal significant rapid lateral changes in the midcrustal structure beneath the station that are interpreted in relation to the origin of the east continent gravity high located northeast of rscp the results from events arriving from the northeast show a high velocity midcrustal layer not present in results from the southeast azimuth this velocity structure can be shown to support the idea that this feature is part of a keweenawan rift system another interesting feature of the derived velocity models is the indication that the crust mantle boundary beneath the cumberland plateau is a thick probably laminated transition zonemore between the depths of 40 and 55 km a result consistent with interpretations of early refraction work in the area less

changes of climate glaciers and runoff in china s monsoonal temperate glacier region during the last several decades changes of climate glaciers and runoff during the last several decades in china s monsoonal temperate glacier region have been studied temperature has increased in a fluctuating manner during the last several decades and temperature rise has accelerated since the 1980s net accumulation of dasuopu ice core has consistently declined and the precipitation decrease was also obvious from the end of 1970s through the middle 1980s and particularly after the 1990s in china s monsoonal temperate glacier region as a response to climate change eight monsoonal temperate glaciers were stationary or advancing between the 1900s 1930s and the 1960s 1980s and were in retreat from the 1930s to the 1960s and from the 1980s to the present ablation is heavy in the glacier tongue areas and the mean ablation water equivalent in hailuogou glacier during 1990 91 1997 98 was 876 mm more than that in 1982 83 ablation depth on the exposed ice area increased by 1 4 m a 1 over the period 1983 84 1990 91 mass balance records also show that glaciers suffered a constant mass loss of snow and ice and the accumulated mass balance in hailuogou basin and baishui glacier no 1 was 10 83 m water equivalent in the past 45 years and 11 38 m in the past 52 years as glaciers become shorter narrower and thinner under the background of climate warming changes of internal and upper surface morphology also occurred providing evidence of the response to climatic warming in recent years local hydrological and climatic data demonstrated that in yanggong basin during 1979 2003 and hailuogou basin during 1988 2004 runoff from the glacier areas has been increasing both seasonally and annually overall it is clear that china s monsoonal temperate glaciers are losing mass and are retreating under the background of climate warming c 2009 elsevier ltd and inqua all rights reserved

perylene occurrence alkylation and possible sources in deep ocean sediments abstract 81 deep ocean sediment samples obtained from the dsdp ipod program legs 63 66 and six gravity cores from dsdp ipod leg 64 guaymas basin gulf of california site survey cruise sio were analyzed for perylene s perylene was found to be most abundant in anoxic diatomaceous sediments containing moderate amounts of silts and or clays elevated perylene yields normalized to organic carbon contents coincided with enhanced preservation of autochthonous tetraterpenoid and tetrapyrrole pigments indicating a requirement of anoxia in the formation of perylene strongly euxinic conditions correlate with decreased perylene yields but not its total absence as found for strongly aerobic deposition and or redeposition perylene alkylation occurs in response to increasing in situ temperatures alt sub bottom depth this alkylation was found to begin with the generation of methyl c 1 perylene and to eventually yield a perylene alkyl perylene homologous series in decreasing abundance through the equivalent of c 3 trimethyl methyl ethyl propyl perylene the realm of most intense perylene alkylation for quaternary or pliocene miocene sediments corresponds with present in situ temperatures of 40 50 c or 30 35 c respectively thus the degree of perylene alkylation may represent an organic indicator for the thermal history of immature sediments geological phenomena such as reworking and igneous intrusions were found to complicate downhole perylene alkylation patterns a substituted c4h7o2 perylene was isolated from several anoxically deposited diatomaceous oozes and may represent one of the many possible perylene precursors the possible source compounds and biota for sedimentary perylene are discussed in light of the present study and review of past reports

effects of weathering on organic matter abstract bulk geochemical petrographical mineralogical and molecular compositions of unweathered weathered and transitional zones of a middle jurassic fossil wood were analyzed to trace changes caused by oxidative weathering of the immature terrestrial organic matter om the occurrence of such zones was confirmed by the mineral composition showing replacement of siderite and pyrite by goethite vitrinite reflectance analysis of weathered and unweathered fossil wood samples revealed that weathering elevated the vitrinite reflectance values by ca 0 1 which should be taken into account during modeling of low maturity terrestrial om in the weathered part of the wood most of the biomarkers and biomolecules were totally removed or the concentration decreased significantly the concentration of most of the polynuclear aromatic hydrocarbons pahs decreased by 50 80 being 90 for the more reactive and less stable benzo a pyrene and perylene on the other hand several aromatic compounds like phenanthrene and its methyl derivatives phenyl naphthalenes fluoranthene and oxygen containing aromatic compounds increased in concentration in the weathered zone this results from processes such as formation of phenyl derivatives of pahs and their cyclization as well as aromatization of diterpenoids and incorporation of oxygen into aromatic structures weathering should always be considered in studies of fossilized terrestrial om especially in the case of thermal maturation modeling because it significantly decreases the om content and total sulfur content changes vitrinite reflectance values and alters the extract composition as a result of organic compound degradation

morphodynamics and lake level variations at paiku co southern tibetan plateau china abstract proxy records from lakes on the tibetan plateau are commonly used to infer monsoon related climatic changes during the late quaternary specific influences of catchment processes and their interaction with the lake basin are seldom utilized based on morphological field investigations supported by remote sensing analyses in combination with radiocarbon dated sediment data from lacustrine sequences along paleoshorelines and terraces we can demonstrate that close relationships exist between glacier dynamics fluvial alluvial fan terrace formation and lake level and lake area changes of paiku co southern tibet our results show that the formation of large scale fluvial alluvial fans f1 predates the maximum advance of the xixiabangma glaciers the latter formed a distinct terminal moraine complex north of the present glaciers during the local lgm llgm at 42 21 cal ky bp a younger fan generation f2 developed from the llgm to the late holocene which was accompanied by lake level fluctuations with a generally decreasing trend the highest morphologically traceable lake level at 4665 m asl existed prior to 25 cal ky bp and induced a potential overflow to the neighboring langqiang co and pengqu river a high level also existed during the llgm followed by a minor decline until ca 15 cal ky bp owing to reduced meltwater discharge under cold and dry climatic conditions a return to the previous level during the late glacial early holocene period between 11 9 and 9 5 cal ky bp is likely caused by climate warming increased meltwater discharge and enhanced indian summer monsoon ism moisture supply afterwards paiku co shrank gradually toward its present level while the youngest fan f3 generation evolved as individual small sized bodies under ephemeral discharge conditions from the mid holocene to the present the formation of four terrace levels t4 1 is likely the result of sequential incision into the fan generations with a mean erosion rate of 50 cm ky caused by lake level lowering tectonic impact cannot be completely ruled out since 1976 the glaciers lost ca 15 in area accompanied by lake area loss of 3 7 between 1972 and june 2014 seasonal lake level variations of about 1 2 m in height occur in response to summer monsoon rainfall our data show a close interaction between glacial dynamics fluvial processes terrace formation and water budget changes throughout the last 25 cal ky bp in response to the well known insolation driven ism effective moisture supply during the late glacial and holocene period temperature driven meltwater dynamics were the controlling factors for variations in water balance of paiku co

characteristics of water stable isotopes and hydrograph separation in baishui catchment during the wet season in mt yulong region south western china glaciers are of crucial importance for the livelihood of the local populations which depend on their meltwater for water and energy supplies for this reason seasonal variations of oxygen 18 of glacial stream water and their sources within a small glacial catchment in south western china were investigated during the wet season the results showed significant difference of oxygen 18 existed among meltwater rainwater ground water and stream water and significantly seasonal variation of precipitation occurred during the observed period the streamflow of baishui catchment was separated into components of ice snowmelt and precipitation using oxygen 18 as shown by the result of the two component mixing model on average 53 4 of the runoff came from ice snowmelt during the wet season whereas the remaining 46 6 were contributed by precipitation in the catchment according to monthly hydrograph the contribution of snow and glacier meltwater varied from 40 7 to 62 2 and that of precipitation varied from 37 8 to 59 3 in wet season uncertainties for this separation were mainly caused by the variation of tracer concentrations the roles of glacier and snow meltwater should be noticed in water resource management in those glacial regions in south western china copyright c 2012 john wiley sons ltd

timing of multiple late quaternary glaciations in the hunza valley karakoram mountains northern pakistan defined by cosmogenic radionuclide dating of moraines moraines and associated landforms in the upper hunza valley karakoram mountains northern pakistan provide an excellent record of multiple glaciations during the late quaternary glaciers advanced at least eight times by using 10 be and 26 al surface exposure dating on moraine boulders and scoured bedrock we determined the timing of glaciation for four of these glacial advances ca 54 7 43 2 ka borit jheel glacial stage ca 25 7 21 8 ka ghulkin i glacial stage ca 18 4 15 3 ka ghulkin ii glacial stage and ca 10 8 9 0 ka batura glacial stage for two of the older advances the yunz and shanoz glacial stages our data set a limit of 60 ka although at present the uncertainties in dating make it impossible to describe unequivocally the climate processes controlling glaciations in the hunza valley the results suggest that precipitation changes related to oscillations in the southwest asian monsoonal system combine with cooling that is broadly associated with heinrich events to cause glacial advances in this region

glacier no 4 of sigong river over mt bogda of eastern tianshan central asia thinning and retreat during the period 1962 2009 rtk gps data aerial photographs and aster images were used to quantify volume surface elevation terminus position and area changes of glacier no 4 of sigong river over mt bogda tianshan during the period from 1962 to 2009 glacier surface elevation of the tongue area decreased by 15 8 m 0 32 0 17 m a 1 and ice volume loss reached 0 014 0 008 km3 0 013 0 007 km3 w e the glacier terminus retreated at a rate of 8 0 m a 1 and the area decreased by about 0 53 km2 accounting for 15 8 of the glacier area in 1962 3 33 km2 the changes can be primarily attributed to the significant increase in temperature in this region a comparison with glacier changes by field measurements in other regions of eastern tianshan showed obvious spatial differences in the magnitude of the changes owing to a combination of regional climate change and topographical factors

lithospheric structure of the arabian and eurasian collision zone in eastern turkey from s wave receiver functions summary crustal and upper mantle seismic discontinuities beneath eastern turkey are imaged using teleseismic s to p converted phases three crustal phases are observed the moho with depth ranging between 30 and 55 km indicating variable tectonic regimes within this continental collision zone an upper crustal discontinuity at approximately 10 km depth and various crustal low velocity zones possibly associated with recent quaternary volcanism imaging of the upper mantle is complicated by the 3 d geometry of the region in particular due to the bitlis zagros suture zone however several upper mantle s to p converted phase are identified as being the signature of the lithosphere asthenosphere boundary lab the inferred lab for the eastern anatolian accretionary complex indicates that eastern turkey has an anomalously thin between 60 and 80 km lithosphere which is consistent with an oceanic slab detachment model the observed lab phases for the arabian shield and iranian plateau indicate that lithospheric thickness for these stable regions is on the order of 100 to 125 km thick which is typical of continental margins

pervasive seismic low velocity zones within stagnant plates in the mantle transition zone thermal or compositional origin abstract we exploit conversions between p and s waves for large scale high resolution imaging of the mantle transition zone beneath northwest pacific and the margin of eastern asia we find pervasive reflectivity concentrated in two bands with apparent wave speed reduction of 2 to 4 about 50 km thick at the top of the transition zone and 100 km thick at the bottom this negative reflectivity associated with the scattered waves at depth is interpreted jointly with larger scale mantle tomographic images and is shown to delineate the stagnant portions of the subducted pacific plate in the transition zone with largely positive shear wave velocity contrasts the upper reflectivity zone connects to broad low velocity regions below major intra plate volcanoes whereas the lower zone coincides locally with the occurrence of deep focus earthquakes along the east asia margin similar reflectivity is found in pacific northwest of the usa we demonstrate that the thermal signature of plates alone is not sufficient to explain such features alternative explanations for these reflective zones include kinetic effects on olivine phase transitions meta stability compositional heterogeneities within and above stagnant plates complex wave propagation effects in the heterogeneous slab structure or a combination of such factors we speculate that part of the negative reflectivity is the signature of compositional heterogeneities as revealed by numerous other studies of seismic scattering throughout the mantle and that such features could be widespread across the globe

elevation changes measured during 1966 2010 on the monsoonal temperate glaciers ablation region gongga mountains china abstract temperate glaciers are more sensitive to climate change than are polar or continental glaciers and can drive remarkable runoff variation in local water catchments changes in the glacier area and surface elevation of the three monsoonal temperate glaciers in the gongga mountains china were analyzed using series of remote sensing images and digital elevation model dem data all possible sources of uncertainty were considered in detail the results showed that the total glacier area decreased by 4 3 km 2 6 7 between 1966 and 2010 a comparison of glacier surface elevations using dems derived from dual frequency differential gps dgps surveys in 2010 and from 1966 to 1989 from topographic maps the three glaciers underwent significant mass loss from 1966 to 2010 and the mean surface elevation changes were 0 90 0 45 m y 1 06 0 45 m y and 1 12 0 45 m y for hailuogou hlg dagongba dgb and yanzigou yzg glaciers respectively from 1966 to 2010 analysis of the meteorological data showed that the mean annual air temperature increase was the main reason for the thinning and volume loss thinning of the glacier tongue and volume loss was more intense in the period 1989 2010 than in 1966 89 debris thickness and other factors are also believed to play important roles in differential thinning among different areas and periods

global variations of temperature and water content in the mantle transition zone from higher mode surface waves abstract we performed a fully nonlinear joint inversion of surface wave overtone phase velocities for velocity structure down to a depth of 1500 km and topography of transition zone discontinuities using neural networks the resulting models are compared with existing mantle models from linearized inversions techniques and the agreement between vertically averaged s wave velocity models and various 660 km topography models is very good whereas the agreement between all the 400 km topography models is very poor the latter might be due to a broader than previously reported 400 km discontinuity where the minerals co exist with water induced melt from our models of transition zone thickness and s wave velocity we estimated lateral variations of temperature and water content in earth s mantle transition zone linearly relating variations in s wave velocity and transition zone thickness to variations in temperature and water content within the transition zone we observe relatively cold subduction zones as well as relatively warm regions beneath continents and hot spots we find that the transition zone is wettest away from subduction zones