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

salt related structures in the gulf of mexico a field guide for geophysicists in finding economic quantities of oil and gas below a salt sheet the mahogany discovery well in ship shoal south addition offshore louisiana dramatically boosted exploration interest in the gulf of mexico s subsalt play in shallow water interest was initially aroused by the earlier deep water discovery below a salt sheet forming part of mickey mouse a cluster of pancake shaped salt sheets in mississippi canyon block 211 a major technologic obstacle in this play has been the difficulty of imaging the base of salt sheets and the subsalt structures targeted for exploration some recent articles have showcased the spectacular fidelity of 3 d seismic data sets collected on closely spaced survey lines and processed by techniques such as 3 d prestack depth migration and 3 d dip moveout followed by 3 d turning ray kirchhoff migration however at present the cost of this technology limits its use to specific rigorously selected targets

pedogenic carbonates forms and formation processes abstract soils comprise the largest terrestrial carbon c pool containing both organic and inorganic c soil inorganic carbon sic was frequently disregarded because 1 it is partly heritage from soil parent material 2 it undergoes slow formation processes and 3 has very slow exchange with atmospheric co2 the global importance of sic however is reflected by the fact that sic links the long term geological c cycle with the fast biotic c cycle and this linkage is ongoing in soils furthermore the importance of sic is at least as high as that of soil organic carbon soc especially in semiarid and arid climates where sic comprises the largest c pool considering the origin formation processes and morphology carbonates in soils are categorized into three groups geogenic carbonates gc biogenic carbonates bc and pedogenic carbonates pc in this review we summarize the available data and theories on forms and formation processes of pc and relate them to environmental factors after describing the general formation principles of pc we present the specific forms and formation processes for pc features and the possibilities to use them to reconstruct soil forming factors and processes the following pc are described in detail earthworm biospheroliths rhizoliths and calcified roots hypocoatings nodules clast coatings calcretes and laminar caps the second part of the review focuses on the isotopic composition of pc 13c 14c and 18o as well as clumped 13c and 18o isotopes known as 47 the isotopic signature of pc enables reconstructing the formation environment the dominating vegetation 13c temperature 18o and 47 and the age of pc formation 14c the uncertainties in reconstructional and dating studies due to pc recrystallization after formation are discussed and simple approaches to consider recrystallization are summarized finally we suggest the most important future research directions on pc including the anthropogenic effects of fertilization and soil management in conclusion pc are an important part of sic that reflect the time periods and formation processes in soils a mechanistic understanding of pc formation is a prerequisite to predict terrestrial c stocks and changes in the global c cycle and to link the long term geological with short term biological c cycles

recrystallization of shell carbonate in soil 14c labeling modeling and relevance for dating and paleo reconstructions abstract mollusk shells are commonly present in a broad array of geological and archaeological contexts the shell carbonate can serve for numerical age determination 14 c and as a paleoenvironmental indicator 18 o 13 c shell carbonate recrystallization in soils however may re equilibrate the carbon c isotopic signature with soil co 2 the equilibration dynamics remain poorly understood because of the absence of suitable experimental approaches here we used the artificial 14 c labeling technique to study the process of shell carbonate recrystallization as a function of time organic free and organic containing shell particles of protothaca staminea were mixed with loess or a carbonate free loamy soil the mixtures were placed in air tight bottles where the bottle air containing 14 co 2 p co 2 2 the 14 c activity of shells was measured over time and related to the recrystallization of shell carbonate recrystallization of shell carbonate already began after one day the recrystallization rates were 10 3 day 1 in organic containing shell embedded in soil and 1 6 10 2 day 1 in organic free shells in loess removal of organic compounds increased shell porosity and so increased the contact surface for exchange with soil solution organic free shells recrystallized much faster in loess 0 56 in 56 days than in other treatments recrystallization was 2 to 7 times higher in loess in the presence and absence of organic compounds respectively than in carbonate free soil loess carbonate itself can recrystallize and accumulate on shells leading to overestimation of shell carbonate recrystallization a model for shell carbonate recrystallization as a function of time was developed the model considers the presence or absence of organic compounds in shell structure and geogenic carbonates in the embedding matrix the model enabled all results to be fitted with r 2 0 98 the modelled time necessary for nearly full recrystallization 95 of shell carbonate was 88 years for organic free shells in loess and up to 770 years for organic containing shells in carbonate free soil after this period the original isotopic signature will vanish completely and will be replaced by a new 13 c and 14 c signature in the shell structure thus shell carbonate recrystallization may proceed relatively rapidly in terms of geologic time this is necessary to consider in the interpretation of dating results and paleoenvironmental reconstructions

anisotropic shear wave velocity structure of the earth s mantle a global model 1 we combine a new large data set of surface wave phase anomalies long period waveforms and body wave travel times to construct a three dimensional model of the anisotropic shear wave velocity in the earth s mantle our modeling approach is improved and more comprehensive compared to our earlier studies and involves the development and implementation of a new spherically symmetric reference model simultaneous inversion for velocity and anisotropy as well as discontinuity topographies and implementation of nonlinear crustal corrections for waveforms a comparison of our new three dimensional model s362ani with two other models derived from comparable data sets but using different techniques reveals persistent features 1 strong 200 km thick high velocity anomalies beneath cratons likely representing the continental lithosphere underlain by weaker fast anomalies extending below 250 km which may represent continental roots 2 weak velocity heterogeneity between 250 and 400 km depths 3 fast anomalies extending horizontally up to 2000 3000 km in the mantle transition zone beneath subduction zones 4 lack of strong long wavelength heterogeneity below 650 km suggesting inhibiting character of the upper mantle lower mantle boundary and 5 slow velocity superplumes beneath the pacific and africa the shear wave radial anisotropy is strongest at 120 km depth in particular beneath the central pacific lateral anisotropic variations appreciably improve the fit to data that are predominantly sensitive to the uppermost and lowermost mantle but not to the waveforms that control the transition zone and midmantle depths tradeoffs between lateral variations in velocity and anisotropy are negligible in the uppermost mantle but noticeable at the bottom of the mantle

first excavation of intact middle stone age layers at ysterfontein western cape province south africa implications for middle stone age ecology abstract excavations into a coastal cliff at ysterfontein yft 1 south africa have revealed 2 5 3 m of stratified sands containing classic middle stone age msa stone artifacts abundant mussel and limpet shells numerous fragments of ostrich eggshell and somewhat rarer bones from mammals birds tortoises and snakes the sands apparently filled a crevice like calcrete shelter where the artifacts and animal remains accumulated partly in place and perhaps partly through slippage down the face of a dune that once stood between the site and the sea accelerator radiocarbon dating of ostrich eggshell places the sequence before 33 400 years ago artifact typology provisionally suggests that it formed after 70 000 years ago the fauna resembles faunas from the handful of other known coastal msa sites and contrasts with faunas from regional later stone age lsa sites in its low diversity of coastal marine species and in the large size of its limpets and tortoises the difference suggests that msa people exploited local resources less intensively probably because their populations were less dense

a parametric analysis of two dimensional elastic full waveform inversion of teleseismic data for lithospheric imaging the development of dense networks of broad band seismographs makes teleseismic data amenable to full waveform inversion fwi methods for high resolution lithospheric imaging compared to scattered field migration fwi seeks to involve the full seismic wavefield in the inversion we present a parametric analysis of 2 d frequency domain fwi in the framework of lithospheric imaging from teleseismic data to identify the main factors that impact on the quality of the reconstructed compressional p wave and shear s wave speed models compared to controlled source seismology the main adaptation of fwi to teleseismic configuration consists of the implementation with a scattered filed formulation of plane wave sources that impinge on the base of the lithospheric target located below the receiver network at an arbitrary incidence angle seismic modelling is performed with a hp adaptive discontinuous galerkin method on unstructured triangular mesh a quasi newton inversion algorithm provides an approximate accounting for the hessian operator which contributes to reduce the footprint of the coarse acquisition geometry in the imaging a versatile algorithm to compute the gradient of the misfit function with the adjoint state method allows for abstraction between the forward problem operators and the meshes that are during seismic modelling and inversion respectively an approximate correction for obliquity is derived for future application to real teleseismic data under the two dimension approximation comparisons between the characteristic scales involved in exploration geophysics and in teleseismic seismology suggest that the resolution gain provided by full waveform technologies should be of the same order of magnitude for both applications we first show the importance of the surface reflected wavefield to dramatically improve the resolving power of fwi by combining tomography like and migration like imaging through the incorporation of the forward scattered and the backscattered wavefields in the inversion the resolution of fwi is assessed through checkerboard tests and confirms a resolution of the order of the wavelength for both the p and s speeds when the full wavefield is incorporated in the inversion secondly we show that computationally efficient strategies which consist of decimating the number of frequency components involved in the inversion do not apply to teleseismic acquisitions because the scattering angle bandwidth sampled by plane wave sources can be narrow and coarsely sampled compared to that provided by dense profiles of point sources in exploration seismology the waveform inversion is less sensitive to the band of incidence angles spanned by the plane wave sources and to the sampling of this band however the deficit of vertically propagating plane waves hampers the vertical resolution of planar layers aliasing artefacts created by coarse arrays of receivers are illustrated we show how taking into account the hessian in the inversion and the suitable management of frequencies in the inversion help to mitigate these artefacts acceptable reconstructions are shown for both the p and s wave speeds for a receiver spacing of up to 20 km in the 0 1 0 4 hz frequency range building a reliable initial model for fwi is a highly non linear problem in exploration seismology we show how the low frequency content of the teleseismic sources allow us to build accurate p and s wave speed models starting from simple vertical gradient velocity models all of these results are derived using a 2 d realistic synthetic experiment that was performed with noise free data most of conclusions of this parametric study should apply in three dimensions the impact of noise and the footprint of other experimental parameters such as the estimation of the temporal plane wave signature and the estimation of the incidence angle of the impinging plane waves need however to be assessed in the future

a two dimensional hybrid method for modeling seismic wave propagation in anisotropic media national science foundation of china 40504006 40434012 90814002 ear 0609717 chinese academy of sciences

waveform tomography reveals channeled flow at the base of the oceanic asthenosphere understanding the relationship between different scales of convection that drive plate motions and hotspot volcanism still eludes geophysicists using full waveform seismic tomography we imaged a pattern of horizontally elongated bands of low shear velocity most prominent between 200 and 350 kilometers depth which extends below the well developed low velocity zone these quasi periodic fingerlike structures of wavelength 2000 kilometers align parallel to the direction of absolute plate motion for thousands of kilometers below 400 kilometers depth velocity structure is organized into fewer undulating but vertically coherent low velocity plumelike features which appear rooted in the lower mantle this suggests the presence of a dynamic interplay between plate driven flow in the low velocity zone and active influx of low rigidity material from deep mantle sources deflected horizontally beneath the moving top boundary layer

ionospheric variability over indian low latitude linked with the 2009 sudden stratospheric warming in this paper we analyze radar observations of e b drift and plasma irregularities ionosonde observations of e and f layer parameters including spread f and magnetic field observations made from indian low latitudes linked with the 2009 sudden stratospheric warming ssw event e b drift variations presented here are the first of their kind from the indian sector as far as the effect of ssw is concerned difference of magnetic fields observed from the equator and low latitude h and e b drift show linear relation and both show remarkably large positive values in the morning and negative values in the afternoon exhibiting semidiurnal behavior remarkable changing patterns in the critical frequency of f2 layer fof2 and f3 layer fof3 were observed after the occurrence of ssw large variations with quasi 16 day periodicity were observed in h fof2 and fof3 both semidiurnal and quasi 16 day wave modulation observed after the 2009 ssw event are consistent with those reported earlier we also noted quasi 6 day variations in h and fof2 soon after the ssw commencement not much reported before during the counterelectrojet events linked with the ssw event while equatorial es esq disappeared as expected there were no blanketing es esb a finding not reported and discussed earlier esb was also not formed at the off equatorial location indicating the absence of required vertical wind shear but e region plasma irregularities were observed by the ionosonde and radar with a close relationship between the two weak f region irregularities were observed in the postmidnight hours and case studies suggest the possible role of ssw related background electric field in the manifestation of postmidnight f region irregularities

gypsum a joint tomographic model of mantle density and seismic wave speeds 1 gypsum is a 3 d model of mantle shear wave s speeds compressional wave p speeds and density the model is developed through simultaneous inversion of seismic body wave travel times p and s and geodynamic observations while using realistic mineral physics parameters linking wave speeds and density geodynamic observations include the global free air gravity field divergence of the tectonic plates dynamic topography of the free surface and the flow induced excess ellipticity of the core mantle boundary gypsum is built with the philosophy that heterogeneity that most closely resembles thermal variations is the simplest possible solution models of the density field from earth s free oscillations have provided great insight into the density configuration of the mantle but are limited to very long wavelength solutions alternatively scaling higher resolution seismic images to obtain density anomalies generates density fields that do not satisfy geodynamic observations the current study provides a 3 d density model for the mantle that directly satisfies geodynamic and seismic observations through a joint seismic geodynamic inversion process notable density field observations include high density piles at the base of superplume structures supporting the general results of past normal mode studies however we find that these features are more localized and have lower amplitude than past studies would suggest when we consider both fast and slow seismic anomalies in gypsum we find that p and s wave speeds are strongly correlated throughout the mantle however we find a low correlation of fast s wave zones in the deep mantle 1500 km depth with the corresponding p wave anomalies suggesting a systematic divergence from simplified thermal effects in ancient subducted slab anomalies the cratonic lithosphere and d regions are shown to have strong compositional signatures however we argue that temperature variations are the primary cause of p wave speed s wave speed and density anomalies throughout most of the mantle

seismic and electromagnetic controlled source interferometry in dissipative media abstract seismic interferometry deals with the generation of new seismic responses by crosscorrelating existing ones one of the main assumptions underlying most interferometry methods is that the medium is lossless we develop an interferometry by deconvolution approach which circumvents this assumption the proposed method applies not only to seismic waves but to any type of diffusion and or wave field in a dissipative medium this opens the way to applying interferometry to controlled source electromagnetic csem data interferometry by deconvolution replaces the overburden by a homogeneous half space thereby solving the shallow sea problem for csem applications we demonstrate this at the hand of numerically modeled csem data

reverse time migration migration of stacked or zero offset sections is based on deriving the wave amplitude in space from wave field observations at the surface conventionally this calculation has been carried out through a depth extrapolation we examine the alternative of carrying out the migration through a reverse time extrapolation this approach may offer improvements over existing migration methods especially in cases of steeply dipping structures with strong velocity contrasts this migration method is tested using appropriate synthetic data sets

inferring upper mantle structure by full waveform tomography with the spectral element method summary mapping the elastic and anelastic structure of the earth s mantle is crucial for understanding the temperature composition and dynamics of our planet in the past quarter century global tomography based on ray theory and first order perturbation methods has imaged long wavelength elastic velocity heterogeneities of the earth s mantle however the approximate techniques upon which global tomographers have traditionally relied become inadequate when dealing with crustal structure as well as short wavelength or large amplitude mantle heterogeneity the spectral element method on the other hand permits accurate calculation of wave propagation through highly heterogeneous structures and is computationally economical when coupled with a normal mode solution and applied to a restricted region of the earth such as the upper mantle sem importantly sem allows a dramatic improvement in accounting for the effects of crustal structure here we develop and apply a new hybrid method of tomography which allows us to leverage the accuracy of sem to model fundamental and higher mode long period 60 s waveforms we then present the first global model of upper mantle velocity and radial anisotropy developed using sem our model semum confirms that the long wavelength mantle structure imaged using approximate semi analytic techniques is robust and representative of the earth s true structure furthermore it reveals structures in the upper mantle that were not clearly seen in previous global tomographic models we show that semum favourably compares to and rivals the resolving power of continental scale studies this new hybrid approach to tomography can be applied to a larger and higher frequency data set in order to gain new insights into the structure of the lower mantle and more robustly map seismic structure at the regional and smaller scales

simultaneous inversion for 3 d variations in shear and bulk velocity in the mantle until recently most of the seismic tomographic modeling has been addressing the question of lateral heterogeneity either in p or s wave velocities the s wave velocity variations are larger and hence provide stronger signal on long period waveforms the direct p travel times being the first arrivals on the other hand are most frequently reported in the international seismological centre isc bulletins in mineral physics experiments the variation in bulk velocity is more often measured to better understand the differences between vp and vp patterns and better link the results from mineral physics to those of seismic tomography we formulate the inverse problem in terms of relative perturbations in the shear velocity vs 12 and bulk sound velocity v k 12 we use a large data set which consists of waveforms waveform derived travel times and travel times from the isc bulletins the earthquakes are relocated using corrections for lateral heterogeneity the events which cannot be reliably determined are discarded the model is defined as spherical harmonics to degree 12 horizontally and as chebyshev polynomials to order 13 radially for both shear and bulk sound velocity the inversion is performed under smoothness constraint the resolution tests and bootstrapping analysis indicate that the model is well recovered particularly at long wavelength the results indicate a much larger variability of shear than bulk sound velocity the model explains observations well the most intriguing result obtained in this study is that the variations in shear velocity and bulk sound velocity are negatively correlated in the lowermost mantle the explanation is not very clear from the mineral physics point of view it is not unlikely that this could be explained in terms of thermal variation even though we are unwilling to rule out the possibility of large wavelength compositional variations

cation exchange retards shell carbonate recrystallization consequences for dating and paleoenvironmental reconstructions abstract the radiocarbon method has been frequently used to date mollusk shell carbonate the accuracy of estimated ages however depends on the degree and completeness of shell carbonate recrystallization although the effect of contamination of the shell caco 3 with environmental carbon c is well known the role of ca 2 in diagenetic processes remains unclear addition of young c to shells during diagenesis occurs in soil solution where the ca 2 concentration is in equilibrium with exchangeable ca 2 and or weathering of ca bearing minerals while the exchange process takes place within seconds the dissolution equilibrium requires longer timescales on the order of months it has therefore been hypothesized that the dissolution and recrystallization of shell carbonate in soils with higher cation exchange capacity cec should proceed slower compared to those with low cec the objective was to determine the effects of soil cec and exchangeable cations on shell carbonate recrystallization using the 14 c labeling approach shell particles of the bivalve protothaca staminea were mixed with carbonate free sand cec 0 37 cmol kg 1 sand a loamy soil cec 16 cmol kg 1 loam or the same loamy soil saturated with kcl where exchangeable cations were replaced with k exchanged the high sensitivity 14 c labeling tracing approach was used to determine carbonate recrystallization rates shell carbonate recrystallization after 120 days in loam and exchanged 0 016 and 0 024 mg caco 3 respectively showed one order of magnitude lower recrystallization than in sand 0 13 mg caco 3 a high level of soil exchangeable ca 2 decreased the solubility of shell carbonate and consequently its recrystallization because the exchange is faster than dissolution therefore soil cec and cation composition are determinant factors of shell carbonate recrystallization shells in soils with low cec may undergo more intensive recrystallization hence they may need further pretreatments before the dating procedure

mapping the upper mantle three dimensional modeling of earth structure by inversion of seismic waveforms a method is presented for the inversion of waveform data for the three dimensional distribution of seismic wave velocities the method is applied to data from the global digital networks international deployment of accelerometers global digital seismograph network the selected data set consists of some 2000 seismograms corresponding to 53 events and 870 paths the moment tensors of the earthquakes are determined through an iterative procedure which minimizes the corrupting influence of lateral heterogeneity a global model is constructed for shear wave velocity expanded up to degree and order 8 in spherical harmonics and described by a cubic polynomial in depth for the upper 670 km of the earth s mantle although no a priori information is incorporated the model predictions reproduce much of what is known about the dispersion of mantle waves for example high phase velocities for shields low velocities at ridges and a strong degree 2 pattern for rayleigh waves since the method makes use of complete waveforms overtone data are also included it is shown that the model is reproducible in that substantially the same model can be constructed from each half of the total data set considered independently the model shows that shields and ridges are major features in the depth interval 25 250 km the ridges of the southern pacific and the larger shields persist to 350 km but the southeast indian rise is underlain by a high velocity anomaly at this depth as is much of the mid atlantic ridge at 450 650 km the major features are a broad region of high velocities incorporating south america much of the south atlantic and parts of west africa a broad region of low velocities in the central and eastern pacific high velocities in the western pacific and a low velocity anomaly beneath the red sea and the gulf of aden in the absence of a crustal correction degrees 2 and 3 show a high positive correlation with the geoid paradoxically this is largely destroyed when the distribution in crustal thickness is taken into account spherical harmonic degrees 4 7 show a significant negative correlation

radiocarbon dating of organic and carbonate carbon in genyornis and dromaius eggshell using stepped combustion and stepped acidification abstract a technique for determining the radiocarbon age of both organic carbon and carbonate carbon in the eggshell of the large flightless birds genyornis newtoni now extinct and dromaius novaehollandiae extant emu is presented here stepped combustion for organic carbon and stepped acidification for carbonate carbon were used to obtain multiple age determinations for each sample from which an assessment of the reliability of the ages is possible analysis of a genyornis newtoni eggshell fragment known to have an age considerably beyond the limit of radiocarbon dating has indicated that the backgrounds obtainable using this approach are 0 122 0 033 pmc for the organic carbon fraction and 0 070 0 025 pmc for the carbonate carbon fraction these backgrounds suggest that finite ages up to 50 000 55 000 bp are readily achievable on eggshell using stepped combustion acidification analysis of a single fragment of genyornis eggshell from williams point central south australia suggests that significant contamination of the organic carbon fraction of the eggshell is possible while ages for the carbonate fraction appear more reliable and indicate that the eggshell has an age of at least 49 000 2000 bp a total of six analyses of single genyornis newtoni and dromaius novaehollandiae eggshell fragments from the wood point deposit in southern south australia suggest ages for the samples of 41 000 800 and 37 900 700 bp respectively while an optically stimulated luminescence osl sample from a location very close to the genyornis sample has an age of 55 5 ka 1 the osl and calibrated radiocarbon ages for the genyornis sample and the sand matrix overlap at two standard deviations suggesting the most likely age for the eggshell and the sand matrix is 45 cal ka bp or earlier

dating north asian surface assemblages with ostrich eggshell implications for palaeoecology and extirpation east asian ostrich struthio anderssoni lowe was thought to have become extinct sometime in the late pleistocene petroglyphs portray ostrich with pleistocene animals and ostrich eggshell oes fragments and ornaments from holocene sites were considered to be older fossils here we summarize previous radiometric dates for ostrich eggshell oes and present 15 new calibrated accelerator mass spectrometry ams dates indicating that ostrich survived in mongolia and northern china until at least 8 9 ka bp the dates in our sample population suggest a correlation between struthio and warm steppe environments with extirpation probably related to essential changes in holocene steppe ecosystems including human expansion this study assesses the usefulness of asian oes for archaeological dating by ams constrains the date of asian ostrich extirpation and investigates palaeoenvironmental implications of ostrich survival and extinction

3d reverse time migration using the acoustic wave equation an experience with the seg eage data set kirchhoff is the most commonly used 3d prestack migration algorithm because of its speed and other economic advantages but it uses a high frequency ray approximation to the wave equation and therefore has difficulties in imaging complex geologic structures where multipathing occurs e g beneath rugose horizons such as faulted salt domes where traveltime calculations become difficult

joint inversion for global isotropic and radially anisotropic mantle structure including crustal thickness perturbations we present a new global whole mantle model of isotropic and radially anisotropic s velocity structure sglobe rani based on 43 000 000 surface wave and 420 000 body wave travel time measurements which is expanded in spherical harmonic basis functions up to degree 35 we incorporate crustal thickness perturbations as model parameters in the inversions to properly consider crustal effects and suppress the leakage of crustal structure into mantle structure this is possible since we utilize short period group velocity data with a period range down to 16 s which are strongly sensitive to the crust the isotropic s velocity model shares common features with previous global s velocity models and shows excellent consistency with several high resolution upper mantle models our anisotropic model also agrees well with previous regional studies anomalous features in our anisotropic model are faster sv velocity anomalies along subduction zones at transition zone depths and faster sh velocity beneath slabs in the lower mantle the derived crustal thickness perturbations also bring potentially important information about the crustal thickness beneath oceanic crusts which has been difficult to constrain due to poor access compared with continental crusts

vostok ice core provides 160 000 year record of atmospheric co2 direct evidence of past atmospheric co2 changes has been extended to the past 160 000 years from the vostok ice core these changes are most notably an inherent phenomenon of change between glacial and interglacial periods besides this major 100 000 year cycle the co2 record seems to exhibit a cyclic change with a period of some 21 000 years

ostrich expansion into india during the late pleistocene implications for continental dispersal corridors abstract new evidence is presented for the earliest occurrence of ostrich struthio sp in india during the late pleistocene along with a synthesis on the evidence for ostrich populations in the subcontinent direct dating of ostrich eggshell using accelerator mass spectrometry ams radiocarbon methods on excavated samples from katoati rajasthan india is supported by optically stimulated luminescence osl dating of associated sediments to demonstrate the arrival of ostrich in india before 60 thousand years ago ka in addition the first stable isotope studies on ostrich eggshell from india have been conducted yielding a new form of palaeoenvironmental proxy data for the late pleistocene the geographic expansion of ostrich into india corresponds with the distribution of sahel like environments bordering but not substantially colonising endemic indian vegetation zones the dispersal of ostrich into india marks a rare introduction of megafauna into the subcontinent during the late pleistocene the longevity of which spans a period more than 40 ka the timespan and range of this colonisation indicate the availability and exploitation of suitable habitats in india the continental dispersal of ostrich into india during the late pleistocene offers useful insights into the debate surrounding the dispersal of modern humans and contrasts with the hypothesized coastal movement of homo sapiens into india

full wave seismic data assimilation theoretical background and recent advances the seismological inverse problem has much in common with the data assimilation problem found in meteorology and oceanography using the data assimilation methodology i will formulate the seismological inverse problem for estimating seismic source and earth structure parameters in the form of weak constraint generalized inverse in which the seismic wave equation and the associated initial and boundary conditions are allowed to contain errors the resulting euler lagrange equations are closely related to the adjoint method and the scattering integral method which have been successfully applied in full 3d full wave seismic tomography and earthquake source parameter inversions i will review some recent applications of the full wave methodology in seismic tomography and seismic source parameter inversions and discuss some challenging issues related to the computational implementation and the effective exploitation of seismic waveform data

a hybrid method to compute short period synthetic seismograms of teleseismic body waves in a 3 d regional model we present a hybrid method to simulate the propagation of short period teleseismic body waves through 3 d regional models the incident wavefield is computed in an spherically symmetric reference earth model based on the direct solution method the global and regional wavefields are matched at the boundaries of the regional mesh in the regional domain we implement a spectral element method with absorbing boundaries to cancel the outgoing scattered wavefield the hybrid method is successfully benchmarked against the direct solution method in the reference earth model iasp91 the potential of the method is illustrated by computing short period p wave synthetic seismograms in a 3 d model with a 20 km moho offset and or topography on the free surface focusing on the actual example of the pyrenees

dating surface assemblages using pottery and eggshell assessing radiocarbon and luminescence techniques in northeast asia the vast majority of known archaeological sites in arid northeast asia are surface assemblages containing few or no organic remains the lack of stratified sites and a relative absence of organic remains in surface assemblages hinders our ability to date sites create local chronologies and contextualize technological and socio economic change such problems are common in arid regions around the world new radiocarbon and luminescence dates on collections from the gobi desert of mongolia and china are used here to assess the potential for direct dating of commonly occurring artefacts like ostrich eggshell and pottery direct dating also allows for the identification and sorting of mixed age assemblages here we compare dates derived from accelerator mass spectrometry ams on ostrich eggshell ams on pottery and luminescence on pottery our findings show that ams and luminescence are highly complementary methods and produce results consistent with expected archaeological ages while ostrich eggshell dates were older than the associated site assemblages

a holocene climatic record from arid northwestern china abstract the history of climatic changes during the interval 8500 3000 cal yr b p has been reconstructed from stratigraphical and chronological studies and the results of total organic carbon toc total inorganic carbon tic element composition pollen and stable isotope analyses of a section along the hongshui river in the southern tengger desert nw china the record suggests that from 8450 bottom of the studied section to 7500 yr b p the climate was characterized by instability from 7500 to 5070 yr b p the climatic conditions improved and can be divided into two parts a warm humid spell between 7290 and 6380 yr b p during which the average temperature was 3 4 c higher than that of today and a warm dry spell lasting from 5950 to 5720 yr b p the climate deteriorated between 6380 and 5950 yr b p from 5720 to 5070 yr b p the temperature decreased but humidity increased an abrupt temperature drop occurred between 5340 and 5290 yr b p that indicated the decline of the warmer and humid mid holocene climate from 5070 yr b p onward the climate oscillated significantly and there were three large temperature decreases coinciding with high mountain glacier advances between 5070 4670 yr b p 4300 3740 yr b p and 3410 3230 yr b p top of the section respectively the climatic fluctuations recorded in the southern tengger desert appear in phase with climatic changes recognized in the tibetan plateau suggesting that the period between 7290 and 6380 yr b p was the most warm humid spell one extremely dry event occurred at ca 3000 yr b p and subsequently the fluvial lacustrine depositional process terminated and wind action prevailed in the area both of these features can be attributed to the rapid strengthening and weakening of the summer monsoon circulation which are closely connected with global changes

eolian environmental changes in the northern mongolian plateau during the past 35 000 yr abstract this study focuses on an eolian section shaamar section in the northern mongolian plateau and compares the eolian sequences in the northern mongolian plateau with those along the southern boundary of the gobi deserts to better understand the dynamics of the gobi deserts during the past 35 000 14c yr bp only a weak entisol like paleosol was formed around 29 000 14c yr bp in the exposed mis 3 portion at the shaamar section whereas an eolian colluvium paleosol sequence at nearby bureghkanga section exhibits three paleosols formed around 29 000 14c yr bp 31 000 14c yr bp 34 000 14c yr bp loess paleosol sequences in the western siberian lowland exhibit four paleosols formed from 40 000 to 25 000 14c yr bp i e mis 3 during mis 2 two mollisol like paleosols were formed from 25 000 to 21 000 14c yr bp and from 16 000 to 13 000 14c yr bp and one entisol like paleosol was formed around 9500 14c yr bp at the shaamar section the mis 2 was characterized primarily by silt deposition except for the interval between 21 000 and 16 000 14c yr bp that was dominated by sand deposition the holocene began with the mollisol like paleosol formation from 8600 to 7000 14c yr bp the mid holocene 7000 to 3000 14c yr bp was marked by a relatively poor vegetation cover and the late holocene since 3000 14c yr bp by the densest vegetation cover of the entire holocene in summary the maximal extent of hyperarid and arid areas gobi deserts and gobi like occurred twice 1 from 21 000 to 16 000 14c yr bp and from 13 000 to 8600 14c yr bp when the dominant eolian deposition conditions extended from 56 n to 33 n or even larger the extent of hyperarid and arid areas retreated to the area between 38 n and 48 n or even much smaller several times during mis 3 and during the early holocene considering the uncertainties of dates it seems that the holocene bioclimatic conditions might have changed more or less synchronously between the north and the south and that the bioclimatic conditions varied more frequently in the north than in the south during mis 3 two mollisol like paleosols iic 13 000 to 16 000 14c yr bp and iiia 21 000 to 25 000 14c yr bp were well developed during mis 2 in the north but no corresponding major paleosols were discovered in the south suggesting that the climate did not change synchronously during mis 2 the climates during the stadial interstadial mis 3 2 transition 25 000 to 21 000 14c yr bp and during the last glacial maximum deglacial transition 16 000 to 13 000 14c yr bp were much more humid in the north than in the south

230th u burial dating of ostrich eggshell abstract obtaining precise and accurate dates for late quaternary terrestrial sequences containing middle stone age or middle paleolithic archaeological materials ca 30 300 ka can be challenging many such sequences lie beyond the limit of radiocarbon dating 50 ka and lack volcanic ashes suitable for 40ar 39ar dating we report a dating approach with about ten times the range of radiocarbon dating 500 ka based on a novel protocol for 230th u dating of ostrich eggshell a common component of african near eastern and asian archaeological sequences uranium in ostrich eggshell typically at levels of tens to hundreds of ppb is acquired after burial however accurate burial ages can be determined from measured 230th u ages when corrected for uranium uptake via diffusion using ostrich eggshells from a pleistocene holocene east african site we have 1 characterized the spatial distribution of uranium and common thorium 232th concentrations in ostrich eggshell by laser ablation icp ms 2 determined apparent 230th u ages on outer and inner layers of eggshells by solution icp ms analyses of selectively abraded eggshells and 3 calculated 230th u burial ages using a simple model for diffusive uptake of uranium we assess our method by comparing the 230th u burial ages median uncertainty 2 3 1 sd with radiocarbon dates on carbonate from the same eggshells we find good agreement in seven out of nine eggshells confirming the accuracy of their 230th u model ages eggshells that fail to yield reliable 230th u ages may be recognized by anomalous patterns of apparent 230th u ages providing a reliability criterion innate to the 230th u data ostrich eggshells are resistant to diagenesis simplifying 230th u dating compared to bones and teeth eggshells of ostrich emu rhea and other living and extinct ratites found on six continents share similar structure and composition suggesting our new approach to 230th u dating of eggshell may be applicable in diverse late quaternary terrestrial settings

late pleistocene intensification technologies in northern china intensification technologies used in late pleistocene northern china include microblades milling stones and pottery all of which have been implicated in development of agriculture in northern china perhaps influenced by the harsh climate of the younger dryas this paper examines the adaptive function of these technologies in the context of late pleistocene climate and environment it is proposed that microlithic technology was a tool of mobile foragers focused on hunting and the initial use of pottery was probably connected to bone grease production only milling stones were initially a plant oriented intensification technology but their sparse episodic appearance in the late pleistocene did not lead to persistent intensification involved in the development of agriculture it was only after the younger dryas in the context of improved holocene climate and greater primary productivity that these three technologies converged with changes in mobility to become part of the agricultural revolution in northern china

a technological and morphological study of late paleolithic ostrich eggshell beads from shuidonggou north china abstract we report the results of a detailed analysis of ostrich eggshell oes beads derived mainly from cultural layer 2 cl2 of locality 2 at the shuidonggou site sdg2 in north china which is dated to ca 31 ka cal bp the eggshells belong to the extinct ostrich struthio anderssoni based on microscopic examination morphometric analysis and experimental replication we identify clear differences in morphology size technology and style results indicate that the technology of bead making is similar to that used in most middle and later stone age sites in africa and recorded ethnographically both well made and poorly crafted oes beads were produced at sdg2 drilling experiments conducted in the framework of this study show that hafted stone points were probably used to make the perforations only occasionally beads were deliberately polished on inner and outer eggshell surfaces beads morphology and technology suggest that distinct types of beads were made by different individual craftspeople this supports the hypothesis that several human groups visited the shuidonggou site and used oes beads as an information technology about 31 ka cal bp