imaging diffraction points using the local image matrices generated in prestack migration energy angle distributions in the local image matrix which is a function of local incident and receiving angles at a subsurface point are different for a planar reflector and a diffraction point the former exhibits a linear distribution along a certain dip direction whereas the latter shows a scattered distribution in the entire matrix therefore the singular values of the local image matrix in the local angle domain indicate the energy distribution along different dip directions the difference between the auto and crosscorrelation coefficients of the sets of singular values between adjacent image points can be used to distinguish these two types of targets and obtain prestack images which contain only diffraction points using three synthetic examples we found that the method can effectively image diffraction points seismic images of diffraction points may provide important information about geological discontinuities and diffraction points can be taken as secondary sources for potential applications in imaging subsalt structures which are poorly illuminated by primary waves

results of paleoecological studies in the loess region of szeged othalom se hungary abstract new results of sedimentological magnetic susceptibility geochemical radiocarbon and malacological analysis from a typical and an infusion loess section are presented from se hungary the geologic and geomorphologic value of the area is that aeolian typical loess accumulated on sand dunes that formed during mis3 while in the interdune depressions on the top of lacustrine deposit series infusion loess developed as the two types of loess interfinger it is the first demonstration that the two types of loess formed during the same time period isochron in different environments heterotype at the end of mis3 and during mis 2 between 33 000 13 000 cal bp a temperate steppe forest steppe environment characterized the loess surface of the se great hungarian plain during the first interstadial phase of mis2 a pinus sylvestris charcoal rich paleosol layer developed on the loess covered surface of a wind blown sand hummock while in the interdune depressions a pond phase developed after the formation of the paleosol layer on the surface of the loess covered wind blown sand hummock during the heinrich 2 event vertigo modesta vallonia tenuilabris indicate a cold steppe forest steppe environment and a deeper and colder lake phase in the interdune depressions after that a short microinterstadial phase developed and a pupilla triplicata chondrula tridens dominated temperate steppe forest steppe environment evolved on the terrestrial surface between 23 000 21 000 cal bp after 21 000 cal bp in the last glacial maximum lgm the environment completely changed the average dust accumulation accelerated and coarse silt 0 02 0 06 mm became dominant as a result the lake stage transformed to a marshy environment while on the land area shade loving including closed forest environment preferring mollusca taxa appeared such as vestia turgida vitrina pellucida and mastus venerabilis based on the mollusca fauna composition humidity increased during the cooling of the lgm horizon forestation started and a boreal forest steppe evolved at the study site during the post lgm the interdune depressions filled and aeolian loess layers developed formation of the infusion loess occurred between 24 000 17 000 cal bp loess formation lasted until the beginning of the late glacial maximum last permafrost maximum and ended in a forest steppe environment with boreal central european holarctic palearctic and continental mollusc fauna elements

desert loess versus glacial loess quartz silt formation source areas and sediment pathways in the formation of loess deposits abstract pathways are presented which show the proposed sequence of events involved in the formation of loess deposits both hypothetical deposits and those of central china hungary nigeria and tunisia these pathways illustrate the potential role of and inter relationships between a variety of silt generating mechanisms in the formation of loess using these pathways the existence of desert loess is discussed and it is concluded that this depends on how the terms glacial loess and desert loess are applied if desert loess is taken either to signify nonglacial mechanisms of silt production or to characterise the environment from which aeolian entrainment took place then desert loess is a very real and widely distributed deposit however if the term glacial loess is used to refer to the global climatic regime under which the loess deposit has formed rather than the geomorphic mechanisms responsible for silt generation then desert loess would not be an appropriate term for the classification of loess deposits it is suggested that classifying loess deposits with reference to the global climatic regime under which they accumulated would facilitate a greater understanding of the role of environmental conditions at all stages in the formation of loess deposits

scavenging of thorium isotopes in the canada basin of the arctic ocean abstract investigations on the distribution of thorium isotopes in the water column have been utilized as powerful tracers to investigate the geochemical pathways of particle reactive material in the ocean we measured th 228 th 230 th 232 th and 234 th isotopes in samples collected along a horizontal profile from barrow ak to the canada basin as well as two vertical profiles in the canada basin the suspended particle concentrations were also measured to investigate the role of suspended particulate matter spm in th scavenging the spm inventory is more than an order of magnitude higher than that reported for the alpha ridge ice station indicating that the spm inventories vary over an order of magnitude in the deep arctic basins the conditional partition coefficient of th isotopes between suspended particulate matter and dissolved phase generally appears to be higher than those in non polar regions and this is attributed to more reactive suspended particulate matter the residence times of total 230 th are significantly lower than those calculated for the alpha ridge station while higher than those found in the eurasian basin and beaufort sea in the canadian basin the calculated residence time in all the deep basins of the arctic ocean varied between 13 1 and 45 1 years a reversible scavenging model applied to the distribution of th isotopes 230 th 228 th in the deep waters and 234 th 228 th in the upper 100 m indicates that the forward removal rate constant is higher than the value reported for the alpha ridge while the reverse rate constant is comparable to the alpha ridge station suggesting faster removal onto particulate matter and slower desorption of th from the particulate matter

3d diffraction imaging of linear features and its application to seismic monitoring many subsurface features such as faults fractures cracks or fluid content terminations are defined by geological discontinuities the seismic response from such features is encoded in diffractions we develop an algorithm for imaging such discontinuities by detecting edge diffractions the algorithm exploits phase reversal phenomena of edge diffractions and uses them as a criterion to separate these diffractions from specular reflections and diffractions produced by a leaner object the performance of the method is demonstrated on both synthetic and real 3d seismic data the output image focuses the diffracted energy back to its origin and shows high semblance values at the edge of the object the method is applied on conventionally stacked data producing an image that contains only diffraction events called the d volume we also reveal the potential of diffractions to image and track the changes of a co2 plume using time lapse analysis and detect any possible co2 seepage from its primary containment

anisotropy parameter inversion in vertical axis of symmetry media using diffractions diffractions play a vital role in seismic processing as they can be utilized for high resolution imaging applications and analysis of subsurface medium properties like velocity they are particularly valuable for anisotropic media as they inherently possess a wide range of dips necessary to resolve the angular dependence of velocity however until recently the focus of diffraction imaging or inversion algorithms have been only on the isotropic approximation of the subsurface using diffracted waves we develop a framework to invert for the effective model this effective model is obtained through scanning over possible effective values and selecting the one that best fits the observed moveout curve for each diffractor location the obtained effective model is then converted to an interval model using a dix type inversion formula the inversion methodology holds the potential to reconstruct the true model with sufficiently high accuracy and resolution properties however it relies on an accurate estimation of diffractor locations which in turn requires good knowledge of the background velocity model we test the effectiveness and applicability of our method on the vertical transverse isotropic marmousi model the inversion results yield a reasonable match even for the complex marmousi model

late quaternary aeolian sedimentation in central and south eastern tibet abstract the geomorphology and the cover sediments in the central and south eastern part of the tibetan plateau provide information about climatic change luminescence dating of aeolian and colluvial silts on top of different moraine sequences provides the first indications for the timing of these sediments during the late quaternary and holocene although there is a widespread cover of aeolian mantles in tibet only a few papers have focussed on them up to now samples from silt layers on top of pleistocene moraines or solifluction debris from central and southern tibet at elevations above 4000 m asl provide early holocene ages in most sections the aeolian silt on top of the bomi moraine in southeastern tibet situated at an elevation of about 3000 m asl provides an age of 25 ka according to geomorphological investigations the bomi moraine dates from the last ice age which can be confirmed by the luminescence data moreover one sample from a silt layer in between gravel layers xainxa is also pleistocene in age according to its sedimentary and geomorphological situation in the tibetan plateau pleistocene loess mainly occurs below 4000 m asl the holocene material a more sandy silt lying above 4000 m asl however aeolian material capping the moraines provides only minimum ages for the terminal moraines the time interval between glacier retreat and the accumulation of aeolian sediments may be several thousand years the most important fact is the trapping of dust in general lakes and a denser vegetation cover are or were the main traps for the typical loess found in the mountain areas of the tibetan plateau

measurements of seismic anisotropy and fracture compliances in synthetic fractured media ultrasonic velocities were measured on a stack of synthetic material plexiglass at low 90 120 khz long wavelength range and high 480 khz short wavelength range frequencies plates were pressed together with uniaxial normal stress these measurements were repeated under different uniaxial pressures for two cases 1without circular rubber inclusions between synthetic fractures and 2with circular rubber inclusions between fractures calculation of anisotropy parameters and also normal and shear interface fracture compliances using linear calculus show reasonable variations anisotropy and compliances decreases as overburden pressure increases suggesting that anisotropy is caused by compliances at higher frequencies synthetic fractures seem to be stiffer than at lower frequencies for the long and short wavelength ranges similar variations were observed for anisotropy parameters and fracture compliances vs measurements in different directions show that for the case without rubber inclusions there is a good approximation of vti medium whereas for the case with inclusions there is a significant difference between vs travelling in directions parallel and perpendicular to the plates

loessification and hydroconsolidation there is a connection abstract loessification can be defined as the acquisition of loessic characteristics by ground systems hydroconsolidation in this context is the collapse of the loess ground structure under the influence of loading and wetting loess on aeolian deposition is metastable a pre requisite for eventual collapse the actual collapse mechanism is dependent on the presence of a critical amount of clay mineral material at major particle contacts this clay accumulates via post depositional processes processes which can be described as part of loessification and as a contribution to collapsibility studies at ospringe in kent england support observations made in the bohemian massif in the czech republic about the nature of the loess ground system and the role of clay minerals and calcite crystals fragipan formation another important post deposition event could depend on hydroconsolidation in loess ground

shallow diffraction imaging in an sh wave crosshole configuration abstractimaging shallow subsurface voids such as karsts sinkholes pinch outs dikes and man made voids is an important task in near surface geophysics we have developed a new diffraction based methodology for void detection and imaging due to the low signal to noise ratio of the diffracted signal in surface acquisition setups we advocate the use of an sh wave multicomponent crosshole acquisition naturally the same setup can be used for velocity model building using tomography and for void imaging the sh wave data are migrated using a model based image point dependent automatic muting function that separates direct arrivals from diffracted events in the migration process for the purpose of location and velocity analysis data are migrated to the depth imaging offset domain only when the velocity model and imaging locations are correct will the diffracted energy be coherently focused to the void location and the diffracted event moveout in the migrated gather will be flat we found that the re

tomography of diffraction based focusing operators diffractions carry the same kinematic information provided by common focus point operators cfpos thus cfpo and diffraction time trajectories may be used separately or combined into a single unified tomography for velocity analysis velocity estimation by tomography of cfpos reduces the depth velocity ambiguity compared to two way time tomography cfpo estimation is complicated where there are event discontinuities and diffractions this problem is overcome by using the kinematic information in diffractions in near offset common offset gathers the procedure is illustrated using synthetic data and a single channel field seismic profile from the blake ridge off the east coast of the united states the results show the effectiveness of the proposed method for estimation of velocity from single channel seismic data and for refinement of the velocity field from multichannel data both applications are costcompetitive

prestack time migration velocity analysis using remigration trajectories abstractwe have developed a prestack time migration tool for local improvement of the seismic migration velocity model the method is based on remigration trajectories that describe the position of an image point in the image domain for different source receiver offsets as a function of the migration velocity it determines kinematic migration parameters using local slope information of migrated seismic reflection events these parameters in turn are used to locally correct the velocity model the main advantage of this technique is that it allows us to carry out a moveout correction not just at a fixed point in a zero offset poststack time migrated gather but varying through all offsets of a common image gather taking into account the reflection point displacement in the midpoint direction in other words it provides for time migration velocity analysis from prestack data we have tested the feasibility of the method on synthetic data from four simple models and the sigsbee2b data our tests deter

late quaternary loess like paleosols and pedocomplexes geochemistry provenance and source area weathering manasbal kashmir valley india abstract the late quaternary loess and loess like deposits in kashmir valley are natural archives that have preserved paleoclimate and paleoenvironmental records of the region we present a loess like paleosol located along the margin of the manasbal lake ganderbal which was studied in detail for understanding the pedological processes and reconstructing the late quaternary soil formation in this paper we present loess like paleosol formation of a nearly 10 6 m thick sequence exposed along the margin of manasbal lake ganderbal district srinagar kashmir geochemical and textural data of this loess like sedimentary sequence fluctuate reflecting the varied depositional processes operating in the valley differential intensity of weathering and processes of pedogenesis weathering indices such as chemical index of alteration chemical index of weathering and plagioclase index of alteration reveal weak to moderate weathering of the parent material provenance discrimination diagrams of the present study disclose that the manasbal loess like paleosol sediments are derived from the mixed source rocks suggesting a variety of provenance with variable geological settings which apparently have undergone weak to moderate recycling processes the manasbal paleosol horizons have been dated by the optically stimulated luminescence osl method to the marine isotope stages mid mis 3 41 7 8 0 ka and late mis 2 14 6 3 8 ka during the mis 3 period the climate was wetter forming a strong ahbtk paleosol as inferred from the geochemical data a steady increase in the caco 3 content and c n ratio in the paleosols from 6 50 m mis 3 indicates arid and drier climatic conditions the area around manasbal lake incised because of climate change and neotectonic activity since post 14 ka

on the reliability and comparability of laser diffraction grain size measurements of paleosols in loess records abstract laser diffraction grain size data and size distributions of paleosols are widely used in paleoenvironmental reconstructions as physicochemical alteration related proxies of past changes of the sedimentary environment different laser diffraction devices optical theories and optical settings are being applied nowadays and ignorance of several uncertainty factors and drawbacks of this indirect grain size characterization approach has led to poorly comparable and reproducible granulometric datasets here we present a detailed comparison of grain size results acquired by three state of the art widely used laser diffraction devices fritsch analysette 22 microtec plus horiba partica la 950 v2 and malvern mastersizer 3000 grain size distributions were calculated using both the fraunhofer and mie scattering theories and a wide variety of optical settings 68 different complex refractive indices 1 45 1 6 0 01i 1i for 10 samples from loess paleosol sequences of the carpathian basin our findings demonstrate that optical settings have significant effects on grain size distributions especially for the finest fractions clay and fine silt populations interestingly the selection of laser diffraction devices was an even more deterministic factor in grain size characterization as revealed by network analyses clustering of bulk and size fractionated grain size records was primarily determined by the device used and also by the applied optical settings at the same time the real physical differences of samples were found to be deterministic exclusively for the sand sized fraction as such these findings emphasize the importance of the accurate description of applied methodological details in research papers as comparability and reproducibility of granulometric datasets cannot be ensured with a lack of information about instrumental conditions and settings

interpolating wide aperture ground penetrating radar beyond aliasing abstractmost of the data acquisition in ground penetrating radar is done along fixed offset profiles in which velocity is known only at isolated points in the survey area at the locations of variable offset gathers such as a common midpoint we have constructed sparse heavily aliased variable offset gathers from several fixed offset collinear profiles we interpolated those gathers to produce properly sampled counterparts thus pushing data beyond aliasing the interpolation methodology estimated nonstationary adaptive filter coefficients at all trace locations including at the missing traces corresponding positions filled with zeroed traces this is followed by an inversion problem that uses the previously estimated filter coefficients to insert the new interpolated traces between the original ones we extended this two step strategy to data interpolation by employing a device in which we used filter coefficients from a denser variable offset gather to interpolate the missing traces on a few

an approach to the problem of loess deposit formation some comments on the in situ or soil eluvial hypothesis abstract the problem of loess formation has been widely discussed for a long time and in many languages at the beginning of the 21st century some parts of this debate are still going on a case is still being made for the in situ approach and there are problems of terminology and mechanism for the central asian loess consideration of the origin of loess material has now replaced the discussion on deposit formation as the major intrinsic problem and in the world of ground engineering there is still much investigation on the origins of collapsibility which is in effect a discussion of loess origins there remain some interesting and useful observations to be made on the north african loess and the loess like materials in australia and the desert loess controversy is still running connections of loess to chernozems fragipans and rendzinas are becoming clearer and it seems that it may be possible to appreciate a loess landscape in which the loess contribution is not immediately apparent recent sem observations suggest that collapsibility develops after metastability as the in situ theory appears to imply

seismic monitoring of diffraction images for detection of local heterogeneities diffracted waves contain valuable information regarding both the structure and composition of the media they are in in seismic data processing however these waves are usually regarded as noise in this paper we present an attempt to use scattered diffracted waves for the detection of local heterogeneities the method is based on the detection of diffracted waves by concentrating the signal amplitudes from diffracting points on the seismic section this is done using a correlation procedure that enhances the amplitude of the seismic signal at the location of the diffractors on the common diffraction point section d section the new local time correction for diffraction traveltime curve parameterization is based on the radius of curvature of the diffracted wavefront and near surface velocity we use the idea of seismic monitoring for detection and delineating local objects which may occur within the subsurface resulting from human activity or fast geological processes the method consists of continuou

provenance of loess material and formation of loess deposits on the chinese loess plateau abstract results of a multiple isotopic chemical and mineralogical analysis of loess from the three northwestern inland basins the junggar basin the tarim basin and the qaidam basin and the loess plateau region of china are summarized they suggest a qualification of the conventional views that the three northwestern basins were the important source areas of the loess plateau and that the sand deserts were the primary single source of the chinese loess it is argued that the gobi stony desert in southern mongolia and the adjoining gobi and sand deserts the badain jaran desert tengger desert ulan buh desert hobq desert and mu us desert in china rather than the three inland basins are the dominant source areas of the loess plateau however although these gobi and sand deserts are regarded as the main source regions they serve as dust and silt holding areas rather than dominant producers the mountain processes including glacial grinding frost weathering salt weathering tectonic processes and some fluvial comminution in the gobi altay mts hangayn mts and the qilian mts have played an important role in producing the vast amounts of loess sized material for forming the loess plateau

poststack velocity analysis by separation and imaging of seismic diffractions small geologic features manifest themselves in seismic data in the form of diffracted waves which are fundamentally different from seismic reflections using two field data examples and one synthetic example we demonstrate the possibility of separating seismic diffractions in the data and imaging them with optimally chosen migration velocities our criteria for separating reflection and diffraction events are the smoothness and continuity of local event slopes that correspond to reflection events for optimal focusing we develop the local varimax measure the objectives of this work are velocity analysis implemented in the poststack domain and high resolution imaging of small scale heterogeneities our examples demonstrate the effectiveness of the proposed method for high resolution imaging of such geologic features as faults channels and salt boundaries

loess is not just the accumulation of dust most regrettably there is much misuse of terminology in connection with the concept of loess and the interpretation of its origin people often speak and write incorrectly about loess accumulation even loess specialists who are aware of the fact that loess as a concept has to satisfy at least 10 criteria loess is not simply dust carried and deposited by wind dust only becomes loess after the passage of a certain amount of time in a given geographical zone i e only through diagenesis in certain ecological environments to state that loess is of aeolian origin is an oversimplification and an incorrect definition because an aeolian origin applies only to the dust from which the loess has been formed we are aware of the fact that airborne dust cannot be transformed into loess in every geographical environment but only under those conditions typical of semi arid grassland or steppe or forested steppe the process primarily occurs where the rate of dust accumulation exceeds sheet wash or weathering soil formation rates if the rate of dust accumulation is less than that of surface erosion or of soil biogenetic processes the dust then develops into soil or through intensive weathering and increased precipitation into loam or clay only part of the aeolian dust transported and deposited in a zone suitable for loess formation remains there permanently and is transformed in situ into loess dust not affected by diagenesis is usually further transported by snowmelt or rainwash and is only transformed into loess after it has been redeposited the loess itself however is easily erodible and its minerals are readily reworked and reaccumulated and given the appropriate conditions it readily undergoes diagenesis again we do not always have sufficient evidence to determine whether a given loess body is of primary or secondary origin traditionally the minerals making up primary loess have been regarded as originating in dust accumulated by aeolian processes secondary loess by contrast is different from typical loess in many ways and it is not unusual to find various loess series in which superimposed dust fractions have been transformed into loess by different processes recently we have observed that the origin of various types of loess is governed by differences in litho ecological conditions rather than by the way in which the mineral material from which the loess is derived dust has been primarily accumulated loessification is therefore determined by environmental conditions

diffraction imaging by uniform asymptotic theory and double exponential fitting seismic diffracted waves carry valuable information for identifying geological discontinuities unfortunately the diffraction energy is generally too weak and standard seismic processing is biased to imaging reflection in this paper we present a dynamic diffraction imaging method with the aim of enhancing diffraction and increasing the signal to noise ratio the correlation between diffraction amplitudes and their traveltimes generally exists in two forms with one form based on the kirchhoff integral formulation and the other on the uniform asymptotic theory however the former will encounter singularities at geometrical shadow boundaries and the latter requires the computation of a fresnel integral therefore neither of these methods is appropriate for practical applications noting the special form of the fresnel integral we propose a least squares fitting method based on double exponential functions to study the amplitude function of diffracted waves the simple form of the fitting function has no singularities and can accelerate the calculation of diffraction amplitude weakening coefficients by considering both the fitting weakening function and the polarity reversal property of the diffracted waves we modify the conventional kirchhoff imaging conditions and formulate a diffraction imaging formula the mechanism of the proposed diffraction imaging procedure is based on the edge diffractor instead of the idealized point diffractor the polarity reversal property can eliminate the background of strong reflection and enhance the diffraction by samephase summation moreover the fitting weakening function of diffraction amplitudes behaves like an inherent window to optimize the diffraction imaging aperture by its decaying trend synthetic and field data examples reveal that the proposed diffraction imaging method can meet the requirement of high resolution imaging with the edge diffraction fully reinforced and the strong reflection mostly eliminated

pseudogleyed loess derivates the most common soil parent materials in the pannonian region of croatia abstract loess derived sediments represent the most widespread soil parent materials in the pannonian region of croatia pseudogley as the most common soil type in this region developed mainly on such parent materials pseudogleys largely correlate with the wrb reference soil group of stagnosols on the general soil map of croatia at scale 1 50 000 gsm of croatia the distinction is made between pleistocene loams pl and loess as pseudogley parent materials the initial purpose of this research was to investigate if the criteria for this distinction were clear and consistent and if the terms used for labeling these parent materials were adequate hence we investigated parent materials of 18 pseudogleys across 6 different locations three on loess and three on pl in the pannonian region of croatia we analyzed their morphology including micromorphology of three representative parent materials particle size distribution total porosity ph and mineral assemblages by modal analysis of three representative parent materials following these analyses no systematic differences between the loess parent materials and the pl parent materials were found additionally it was concluded that due to significant geogenetic and or pedogenetic alterations of all studied parent materials none of them should be labeled simply as loess hence parent material at one location was labeled as leached loess derivate and parent materials at all other locations were labeled as pseudogleyed loess derivates both types of parent materials were described in detail and defined in addition the terminology and the classification of loess derived parent materials in general was proposed the analyzed pseudogleyed loess derivates were not completely uniform across the investigated locations primarily this was due to the polygenesis of loess reflected by differences in particle size distributions and compositions of light and heavy mineral fractions secondarily it was due to the 600 1100 mm map gradient along the study region reflected by differences in ph values and properties of redoximorphic features although pedogenesis of the investigated parent materials might have started already during the late glacial and have continued throughout the holocene at varying and overall decreasing rates their morphology indicates that pseudogleization and lessivage are still active processes which occur simultaneously in the analyzed parent materials and agree with the present climate

paleoenvironments from robust loess stratigraphy using high resolution color and grain size data of the last glacial krems wachtberg record ne austria abstract the complex interplay of dust sedimentation pedogenesis and erosion reworking in the formation of loess paleosol sequences lps challenges paleoenvironmental proxies here we show that color and grain size are essential parameters characterizing loess profiles and support robust stratigraphies as a basis for reconstructions in the context of local geo ecological and large scale paleoclimatic evolution detailed paleoenvironmental records from the period since the arrival of anatomically modern humans to the last glacial maximum are scarce in the alpine surroundings the c 7 5 m thick lps krems wachtberg ne austria known for its well preserved upper paleolithic context at a depth of 5 5 m formed between 40 and 20 ka bp by quasi continuous dust sedimentation interrupted by phases of incipient pedogenesis and local reworking the new kw2015 composite is based on three sections studied and sampled at 2 5 cm resolution color and grain size data support a robust stratigraphy for reconstructions of the pedosedimentary evolution the marked transition from oxidized to reduced paleosols of kw2015 around 34 35 ka corresponds to the middle to upper pleniglacial transition as part of a general cooling trend from marine isotope stage mis 3 to 2 intensely modulated by millennial scale climatic fluctuations as recorded in the greenland ice core data the distinct response of kw2015 to these trends highlights that reconstructing lps evolution based on a robust stratigraphy is a prerequisite to paleoenvironmental proxy interpretation

3 d seismic attributes using a semblance based coherency algorithm seismic coherency is a measure of lateral changes in the seismic response caused by variation in structure stratigraphy lithology porosity and the presence of hydrocarbons unlike shaded relief maps that allow 3 d visualization of faults and channels from horizon picks seismic coherency operates on the seismic data itself and is therefore unencumbered by interpreter or automatic picker biases we present a more robust multitrace semblance based coherency algorithm that allows us to analyze data of lesser quality than our original three trace cross correlation based algorithm this second generation semblance based coherency algorithm provides improved vertical resolution over our original zero mean crosscorrelation algorithm resulting in reduced mixing of overlying or underlying stratigraphic features in general we analyze stratigraphic features using as narrow a temporal analysis window as possible typically determined by the highest usable frequency in the input seismic data in the limit one may confidently apply our new semblance based algorithm to a one sample thick seismic volume extracted along a conventionally picked stratigraphic horizon corresponding to a peak or trough whose amplitudes lie sufficiently above the ambient seismic noise in contrast near vertical structural features such as faults are better enhanced when using a longer temporal analysis window corresponding to the lowest usable frequency in the input data the calculation of reflector dip azimuth throughout the data volume allows us to generalize the calculation of conventional complex trace attributes including envelope phase frequency and bandwidth to the calculation of complex reflector attributes generated by slant stacking the input data along the reflector dip within the coherency analysis window these more robust complex reflector attribute cubes can be combined with coherency and dip azimuth cubes using conventional geostatistical clustering and segmentation algorithms to provide an integrated multiattribute analysis

poststack diffraction imaging using reverse time migration abstract we propose a method for imaging small scale diffraction objects in complex environments in which kirchhoff based approaches may fail the proposed method is based on a separation between the specular reflection and diffraction components of the total wavefield in the migrated surface angle domain reverse time migration was utilized to produce the common image gathers this approach provides stable and robust results in cases of complex velocity models the separation is based on the fact that in surface angle common image gathers reflection events are focused at positions that correspond to the apparent dip angle of the reflectors whereas diffracted events are distributed over a wide range of angles the high resolution radon based procedure is used to efficiently separate the reflection and diffraction wavefields in this study we consider poststack diffraction imaging the advantages of working in the poststack domain are its numerical efficiency and the reduced computational time the numerical results show that the proposed method is able to image diffraction objects in complex environments the application of the method to a real seismic dataset illustrates the capability of the approach to extract diffractions

misleading positions of geomagnetic reversal boundaries in eurasian loess and implications for correlation between continental and marine sedimentary sequences abstract the matuyama brunhes boundary mbb where the earth s magnetic field changed to its present orientation is one of the most frequently used time markers in continental quaternary stratigraphy although magnetic signals have been successfully recovered from loess deposits and an apparently coherent magnetostratigraphy seems to be in place a close examination of the published loess records from northern mid latitudes reveals significant uncertainty and variability for the position of the mbb in asia and part of central europe the mbb has been found in loess a glacial deposit this is in contrast to the well established palaeomagnetic records in deep sea sediments where the mbb is located in the interglacial oxygen isotope stage 19 this discrepancy has caused serious confusion in stratigraphic correlation between loess and marine sequences here we examine the causes of the discrepancy between the two sedimentary environments in their records of the mbb our approach includes a comparison of the mbb in loess and other continental records and an evaluation of the stratigraphic significance of the microtektites found around the mbb based on the occurrence of the mbb in an interglacial stage in lake and continental margin sequences and the correlative stratigraphic positions of the microtektites in marine sediments and loess we demonstrate that the measured positions of the mbb in loess are erroneous and misleading and its true occurrence was during the time of formation of the palaeosol corresponding to oxygen isotope stage 19 the most plausible cause for the apparent offset i e the mbb being found in the underlying loess instead is that the acquisition of remanent magnetisation in loess occurs at a certain depth substantially below the land surface the degree of such displacement is dependent on the lithology and structure of the deposits formed prior to the reversal and the time delay is estimated to be in the order of 103 104 years we show that other geomagnetic boundaries such as those of jaramillo and cobb mountain in loess have been similarly displaced though to a varying extent we suggest that the remanence acquisition in loess is closely related to the post depositional evolution in the structure of loessic materials which is in part influenced by regional climate conditions our conclusions on the displaced remanence acquisition have implications for loess chronology magnetostratigraphy as well as the geomagnetic interpretation of detailed magnetic signatures from loess

enhancing the detection of small coal structures by seismic diffraction imaging abstract faults are the most important geological structures that need to be detected in any modern underground coal mining project even a fault with a throw of a few metres can create safety issues and lead to costly delays in mine production while seismic surveys are usually successful at locating faults with throws greater than 5 10 m reliable techniques for resolving more subtle faults dykes and other minor features are yet to be developed in seismic data there are two types of seismic energy signatures that can be used for subsurface imaging specular reflections and diffractions specular reflections are created by relatively smooth surfaces between layers of differing impedance contrasts such as at coal rock interfaces specular reflections are used in conventional seismic reflection surveys diffractions are generated by local discontinuities caused by surface roughness faults dykes and fractures in this paper we describe the use of a moving average error filter which along with a process of reflection event flattening for accommodation of dips and undulations of coal seam reflections can be used to effectively extract diffraction signals from post stack reflection seismic data by identifying diffractions small faults and other minor features that are elusive using conventional seismic reflection processing can be detected suggesting that diffraction imaging may be a superior method to seismic reflection imaging both synthetic and real 2d and 3d coal seismic data are used to illustrate the feasibility of diffraction imaging for small fault detection it is demonstrated from synthetic examples that the extracted diffractions can be used to detect faults with a throw of 1 m while a real data example shows that it is possible to detect igneous dykes with widths of just 4 m

diffraction imaging by multifocusing correct identification of geologic discontinuities such as faults pinch outs and small size scattering objects is a primary challenge of the seismic method seismic response from these objects is encoded in diffractions our method images local heterogeneities of the subsurface using diffracted seismic events the method is based on coherent summation of diffracted waves arising in media that include interface discontinuities and local velocity heterogeneities this is done using a correlation procedure that coherently focuses diffraction energy on a seismic section by flattening diffraction events using a new local time correction formula to parameterize diffraction traveltime curves this time correction which is based on the multifocusing method depends on two parameters the emergent angle and the radius of curvature of the diffracted wavefront these parameters are estimated directly from prestack seismic traces the diffraction multifocusing stack dmfs can separate diffracted and reflected energy on a stacked section by focusing diffractions to the diffraction location and defocusing the reflection energy over a large area

paleoclimate and weathering of the tokaj hungary loess paleosol sequence abstract the tokaj loess paleosol sequence northeast hungary is a well studied site in southeast europe where detailed paleoenvironmental reconstructions of the quaternary have been carried out in this study the geochemical composition of samples from the upper part of the sequence 45 21 ka was analyzed and a variety of commonly used weathering indices and element ratios were applied to estimate weathering intensity a common semi quantitative proxy of paleoclimatic conditions further similarities and differences between these weathering indices and their sensitivity to changes in paleoclimatic conditions were assessed results indicate that all of them accurately track changes in weathering intensity and are with minor exceptions very similar to each other based on different transfer functions for major and trace element concentrations xrf mass specific magnetic susceptibility and stable carbon isotopic 13c data mean annual paleotemperature and mean annual paleoprecipitation for the time intervals of paleosol formation 45 27 ka and dust deposition 27 21 ka were calculated results differ depending on the respective transfer function and method but agree with x 13c based or slightly overestimate xrf based previously published paleoclimate data of the region xrf and 13c based results converge to a mean annual temperature mat range of 8 5 10 c paleosol and 8 9 c loess and a mean annual precipitation map range of 700 900 mm a 1 paleosol and 550 700 mm a 1 loess based results are most consistent with literature data and yield mats of 8 4 c paleosol and 6 6 c loess and maps of 300 500 mm a 1 paleosol and 220 mm a 1 loess

amino acid geochronology applied to the correlation and dating of central european loess deposits abstract numerous localities in the czech republic slovakia and austria have been sampled for fossil gastropod shells for the purpose of an aminostratigraphic evaluation of loess sequences in all three regions alloisoleucine isoleucine aile ile ratios are observed to be significantly higher in shells from loess deposited during the penultimate glacial period cycle c relative to samples from loess of the last glaciation cycle b the difference in aile ile ratio reflects both difference in age of the samples plus the impact on the older samples of the relatively high effective temperature of the last interglacial period amino acid data support the previous correlation suggested between pk ii iii in the czech republic and slovakia and the stillfried a in austria samples have also been recovered from older loess units and previously published correlations within the czech and slovak republics are tested aiie ile ratios appear to distinguish between samples from loess of the last four glacial cycles beyond cycle e 18o stages 10 and 11 the increase in alle ile ratio is relatively small from cycle to cycle in addition shells tend to be poorly preserved and are absent at many localities nevertheless amino acid geochronology offers a means of resolving ages of loess units in the critical time period that is beyond the range of radiocarbon and thermoluminescence methods but post dates the brunhes matuyama paleomagnetic reversal

the loess deposits of buca dei corvi section central italy revisited loess deposits have been described in the past for the upper section of buca dei corvi succession central italy in this paper the deposits were re analysed to clarify the depositional environment and to attempt a paleoclimate reconstruction two radiocarbon dates on pedogenic carbonate constrain the ages to the late glacial and are consistent with previous osl dating of the top of the succession the non marine mollusc assemblage shows typical character of cold and dry climatic conditions testified by strong oligotypical composition mineralogy and geochemistry of the sediments indicate the abundant presence of exotic quartz mineral which can be explained only by wind transport probably wind transport was also responsible of deposition of carbonate which then dissolved and re precipitated producing pedogenic concretions stable isotopes 13c 12c and 18o 16o ratios of the concretions are consistent with a climate drier than present conditions with an environment characterized by sparse vegetation

diffraction imaging by prestack reverse time migration in the dip angle domain prestack image volumes may be decomposed into specular and non specular parts by filters defined in the dip angle domain for space shift extended image volumes the dip angle decomposition is derived via local radon transform in depth and midpoint coordinates followed by an averaging over space shifts we propose to employ prestack space shift extended reverse time migration and dip angle decomposition for imaging small scale structural elements considered as seismic diffractors in models with arbitrary complexity a suitable design of a specularity filter in the dip angle domain rejects the dominant reflectors and enhances diffractors and other non specular image content the filter exploits a clear discrimination in dip between specular reflections and diffractions the former are stationary at the specular dip whereas the latter are non stationary without a preferred dip direction while the filtered image volume features other than the diffractor images for example noise and truncation artifacts are also present synthetic and field data examples suggest that diffractors tend to dominate and are readily recognizable averaging over space shifts in the filter construction makes the reflectors rejection robust against migration velocity errors another consequence of the space shift extension and its angle domain transforms is the possibility of exploring the image in a multiple set of common image gathers the filtered diffractions may be analyzed simultaneously in space shift scattering angle and dip angle image gathers by means of a single migration job the deliverables of our method obviously enrich the processed material on the interpreter s desk we expect them to further supplement our understanding of the earth s interior this article is protected by copyright all rights reserved

automatic detection and imaging of diffraction points using pattern recognition hydrocarbon reservoirs are generally located beneath complex geological structures frequently such areas contain seismic diffractors that carry detailed structure information in the order of the seismic wavelength therefore the development of computational facilities capable of detecting diffractor points with a good resolution is desirable but has been a challenge in the area of seismic processing in this work we present a method for the detection of diffraction points in the common offset gather domain the method applies a two class k nearest neighbours knn pattern recognition technique to amplitudes along diffraction traveltime curves to distinguish between diffractions and reflections or noise while the method in principle requires knowledge of the migration velocity field it is very robust with respect to an erroneous model numerical examples using synthetic seismic and field ground penetrating radar gpr data demonstrate the feasibility of the technique and show its usefulness for automatically mapping diffraction points in a seismic section in our applications the method was able to detect all diffractions present in the data and did not produce any false positives

post stack velocity analysis in the dip angle domain using diffractions interval velocity analysis in complex geological areas is often considered as an unresolved problem a novel approach to improve the velocity analysis process is to perform the analysis in a non conventional domain and to use seismic events that are usually ignored during standard data processing and imaging in this study a method to analyse diffraction data for migration velocity analysis in the time or depth domain is presented the method is based on the clear distinction between diffractions and reflections in the post migration dip angle domain the attractive possibility to perform the analysis using only stacked data as an input is demonstrated on synthetic and real data examples

diffraction imaging by focusing defocusing an outlook on seismic superresolution diffractions always need more advertising it is true that conventional seismic processing and migration are usually successful in using specular reflections to estimate subsurface velocities and reconstruct the geometry and strength of continuous and pronounced reflectors however correct identification of geological discontinuities such as faults pinch outs and small size scattering objects is one of the main objectives of seismic interpretation the seismic response from these structural elements is encoded in diffractions and diffractions are essentially lost during the conventional processing migration sequence hence we advocate a diffraction based data oriented approach to enhance image resolution as opposed to the traditional image oriented techniques which operate on the image after processing and migration even more it can be shown that at least in principle processing of diffractions can lead to superresolution and the recovery of details smaller than the seismic wavelength the so called reflection stack is capable of effectively separating diffracted and reflected energy on a prestack shot gather by focusing the reflection to a point while the diffraction remains unfocused over a large area muting the reflection focus and defocusing the residual wavefield result in a shot gather that contains mostly diffractions diffraction imaging applies the classical isotropic diffraction stack to these diffraction shot gathers this focusingmuting defocusing approach can successfully image faults small size scattering objects and diffracting edges it can be implemented both in model independent and modeldependent contexts the resulting diffraction images can greatly assist the interpreter when used as a standard supplement to full wave images

nonstationary phase estimation a tool for seismic interpretation spectral decomposition is a standard tool in seismic interpretation to highlight variations in layer thicknesses e g in sand channels and turbidites this is done by examining changes in peak frequencies in extracted horizon slices partyka et al 1999 variations in peak frequencies occur due to constructive interference between reflections from the top and bottom of a layer with lower peak frequencies indicating thicker layers

seismic rock physics of steam injection in bituminous oil reservoirs this case study explores rock physics properties of heavy oil reservoirs subject to the steam assisted gravity drainage sagd thermal enhanced recovery process butler 1998 butler and stephens 1981 previous measurements e g wang et al 1990 and eastwood 1993 of the temperature dependant properties of heavy oil saturated sands are extended by fluid substitution modeling and wireline data to assess the effects of pore fluid composition and pressure and temperature changes on the seismic velocities of unconsolidated sands rock physics modeling is applied to a typical shallow mcmurray formation reservoir depth of 135 160 m within the bituminous athabasca oil sands deposit in western canada to construct a rock physics based velocity model of the sagd process although the injected steam pressure and temperature control the fluid bulk moduli within the pore space the effective stress dependant elastic frame moduli are the most poorly known yet most important factors governing the changes of

micromechanics of quartz sand breakage in a fractal context from a quaternary science perspective sand sized quartz as well as silt sized quartz is often acknowledged as final products of glacial abrasion through different evolution mechanisms this view challenges the existence of any universal comminution process which may relate the formation of detrital quartz sand and silt the contribution of grain size energy input and crystalline integrity in the scale of quartz crushability has long been the matter of much debate the present empirical work examines the micromechanics of sand to silt size reduction in the quartz material a series of grinding experiments was performed on leighton buzzard lower greensand using a high energy agate disc mill analogous conditions to glacial abrasion are provided due to the combined abrasion between grains asperity tips and also between grains and rotating smooth tungsten carbide pestle simulation of discontinuous grain breakage allowed the examination of grains crystalline defects to enable an objective assessment of micromechanics of size reduction measurements of particle and mode size distribution fractal indexes and micro morphological signatures were made the crushing approach was probed through varied grinding times at a constant energy input as well as varied energy inputs at constant grinding time breakage pathway was inspected via laser diffraction spectroscopy and transmission light microscopy results suggested that the grain breakdown is not necessarily an energy dependent process non crystallographically pure amorphous quartz sand and silt are inherently breakable materials through a fractal breakdown process results also revealed that the internal defects in quartz are independent from size and energy input

fracture detection by gaussian beam imaging of seismic data and image spectrum analysis localization of fractured areas is of primary interest in the study of oil and gas geology in carbonate environments hydrocarbon reservoirs in these environments are embedded within an impenetrable rock matrix but possess a rich system of various microheterogeneities i e cavities cracks and fractures cavities accumulate oil but its flow is governed by a system of fractures a distinctive feature of wave propagation in such media is the excitation of the scattered diffracted waves by the microheterogeneities this scattering could be a reliable attribute for characterization of the fine structure of reservoirs but it has extremely low energy and any standard data processing renders them practically invisible in comparison with images produced by specular reflections therefore any attempts to use these waves for image congestion of microheterogeneities should first have a preliminary separation of the scattering and specular reflections in this paper the approach to performing this separation is based on the asymmetric summation it is implemented by double focusing of gaussian beams to do this the special weights are computed by propagating gaussian beams from the target area towards the acquisition system separately for sources and receivers the different mutual positioning of beams in each pair introduces a variety of selective images that are destined to represent some selected singular primitives of the target objects such as fractures cavities and edges in this way one can construct various wave images of a target reservoir particularly in scattered diffracted waves additional removal of remnants of specular reflections is done by means of spectral analysis of the scattered diffracted waves images to recognize and cancel extended lineaments numerical experiments with sigsbee 2a synthetic seismic data and some typical structures of the yurubcheno tokhomskoye oil field in east siberia are presented and discussed

marker horizons in the loesses of the carpathian basin abstract two tephra horizons are known in the middle and upper pleistocene loesses of the carpathian basin the older bag tephra has been described from numerous loess outcrops in hungary whereas the younger paks tephra has been described only from the brickyard of paks in southern hungary the most characteristic heavy minerals in these horizons are various clinopyroxenes occurring in different proportions the clinopyroxenes of the bag tephra are extremely rich in ca and al while the volcanic glass is rich in k indicating high k andesitic or shoshonitic volcanism based on comparative geochemical analyses the most likely origin of the bag tephra is the roman or the campanian volcanic fields in italy geochemical investigation of the paks tephra is in progress and preliminary results suggest the same source for this younger tephra in contrast to the tephra horizons the correlation of the numerous paleosols in some hungarian loess sections and their paleoenvironmental interpretation is possible only if they are based on very detailed micromorphological studies the age determination of the loesses containing the paleosols directly by thermoluminescence tl and infrared stimulated luminescence irsl and indirectly by 14 c based isotope work should provide a reliable basis for the identification of soil forming periods in different parts of the carpathian basin

new chronology of the best developed loess paleosol sequence of hungary capturing the past 1 1 ma implications for correlation and proposed pan eurasian stratigraphic schemes abstract in this paper we are presenting a revised chronology of the best developed longest 100 m lps in hungary dating back 1 1 ma borehole udvari 2a it is based on a non tuned age depth model built on the position of the matuyama brunhes boundary jaramillo and olduvai subchrons furthermore on the assignment of formerly recorded uninterpreted geomagnetic reversals in both chrons other chronometric tools ams 14c dating biostratigraphy tephrostratigraphy yielding absolute ages and or ensuring validation of these were also used records of a middle pleistocene gastropod index fossil neostyriaca corynodes 400 140 ka facilitated verification of ages between mis 10 and mis 6 multiple age control points at 15 25 27 45 120 191 362 430 670 780 900 990 1070 ka were established for the last ca 1 1 ma the resulting chronology is the best resolved independent one so far among danubian basin lpss in light of our data the s3 s4 units were fused as s3 in all serbian and some romanian sites and re correlated with mis 9 the results also point to a misassignment of the s5 units at these sites to mis 13 15 leading to erroneous conclusions regarding paleoclimatic conditions and cyclicity in our new stratigraphic scheme these s5 paleosols were taken to represent the s4 paleosol and recorrelated with mis 11 finally an ideal stratigraphic column dating back 1 1 ma for sw hungary was constructed and correlated with the chinese loess paleosol sequence of xifeng and the benthic oxygen isotope record down to mis 31

2d common offset traveltime based diffraction enhancement and imaging the diffracted energy in a seismic recording contains key information about small scale inhomogeneities or discontinuities of the subsurface diffractions can therefore lead to high resolution imaging of subsurface structures associated with hydrocarbon traps however seismic diffracted signals are often much weaker than specular reflections and consequently require enhancement before they can be utilized in this paper diffractions are enhanced relative to reflections based on two traveltime techniques namely the modified common reflection surface approach which uses the common reflection surface technique with some modification to tailor it for diffractions and the replacement media approach derived here for the purpose of a simplified parametrization of diffraction traveltimes both approaches are implemented in the common offset domain with the use of a finite offset central ray unlike the zero or small offset diffraction enhancement techniques that use a zero offset central ray the validity of the two moveout expressions is tested using velocity data taken from a smooth isotropic marmousi model a feasibility test was also carried out with respect to the new replacement media traveltime approximation addressing the various effects of signal to noise ratio depth and lateral displacement of the diffractor location finally diffraction enhancement and imaging was performed on 2d seismic data from the jequitinhonha basin offshore brazil diffractions were significantly enhanced and a high resolution image of the discontinuities of the subsurface was obtained

3d seismic reflection imaging of volcanic hosted massive sulfide deposits insights from reprocessing halfmile lake data new brunswick canada three dimensional seismic reflection data from the halfmile lake area new brunswick canada was reprocessed over an 18 km2 grid to improve the seismic signatures of a 5 million ton volcanic hosted massive sulfide vhms deposit located at 1200 m depth known as the deep zone as well as key host rock structures we chose a prestack dip moveout dmo and poststack migration processing sequence to preserve the possible diffraction signature of the deep vhms zone despite the high level of source generated noise and large statics caused by near surface conditions our processing results revealed improved 3d seismic images for shallow and deep structures many of the imaged structures were easily correlated with known lithological con tacts constrained by boreholes and petrophysical measurements a short flat lying segment of high amplitude reflection at about 800 m depth in the unmigrated cube was interpreted to originate from a small portion of the lower vhms zone the dmo stack was characterized by a l

full azimuth subsurface angle domain wavefield decomposition and imaging part i directional and reflection image gathers we present a new subsurface angle domain seismic imaging systemforgeneratingandextractinghigh resolutioninformation about subsurface angle dependent reflectivity the system enables geophysicists to use all recorded seismic data in a continuousfashiondirectlyinthesubsurfacelocalangledomainlad resulting in two complementary full azimuth common imageangle gather systems directional and reflection the complete setofinformationfrombothtypesofanglegathersleadstoaccurate high resolution reliable velocity model determination and reservoir characterization the directional angle decomposition enables the implementation of specular and diffraction imaging in real 3d isotropic anisotropic geological models leading to simultaneous emphasis on continuous structural surfaces and discontinuous objects such as faults and small scale fractures structural attributes at each subsurface point e g dip azimuth andcontinuity canbederiveddirectlyfromthedirectionalangle gathers the reflection angle gathers display reflectivity as a function of the opening angle and opening azimuth these gathers are most meaningful in the vicinity of actual local reflecting surfaces wherethereflectionanglesaremeasuredwithrespectto the derived background specular direction the reflection angle gathers are used for automatic picking of full azimuth angle domainresidualmoveoutsrmowhich togetherwiththederived background orientations of the subsurface reflection horizons provide a complete set of input data to isotropic anisotropic tomography the full azimuth angle dependent amplitude variations are used for reliable and accurate amplitude versus angle andazimuthavazanalysisandreservoircharacterization the proposed system is most effective for imaging and analysis below complex structures such as subsalt and subbasalt high velocity carbonate rocks shallow low velocity gas pockets and others in addition it enables accurate azimuthal anisotropic imaging and analysis providing optimal solutions for fracture detectionandreservoircharacterization

diffraction imaging of sub vertical fractures and karst with full resolution 3d ground penetrating radar abstract vertical fractures with openings of less than one centimetre and irregular karst cause abundant diffractions in ground penetrating radar gpr records gpr data acquired with half wavelength trace spacing are uninterpretable as they are dominated by spatially undersampled scattered energy to evaluate the potential of high density 3d gpr diffraction imaging a 200 mhz survey with less than a quarter wavelength grid spacing 0 05 m 0 1 m was acquired at a fractured and karstified limestone quarry near the village of cassis in southern france after 3d migration processing diffraction apices line up in sub vertical fracture planes and cluster in locations of karstic dissolution features the majority of karst is developed at intersections of two or more fractures and is limited in depth by a stratigraphic boundary such high resolution 3d gpr imaging offers an unprecedented internal view of a complex fractured carbonate reservoir model analogue as seismic and gpr wave kinematics are similar improvements in the imaging of steep fractures and irregular voids at the resolution limit can also be expected from high density seismic diffraction imaging

3 d seismic discontinuity for faults and stratigraphic features the coherence cube seismic data are usually acquired and processed for imaging reflections this paper describes a method of processing seismic data for imaging discontinuities e g faults and stratigraphic features one application of this nontraditional process is a 3 d volume or cube of coherence coefficients within which faults are revealed as numerically separated surfaces figure 1 compares a traditional 3 d reflection amplitude time slice with the results of the new method to our knowledge this is the first published method of revealing fault surfaces within a 3 d volume for which no fault reflections have been recorded

deep yedoma permafrost a synthesis of depositional characteristics and carbon vulnerability abstract permafrost is a distinct feature of the terrestrial arctic and is vulnerable to climate warming permafrost degrades in different ways including deepening of a seasonally unfrozen surface and localized but rapid development of deep thaw features pleistocene ice rich permafrost with syngenetic ice wedges termed yedoma deposits are widespread in siberia alaska and yukon canada and may be especially prone to rapid thaw processes freeze locked organic matter in such deposits can be re mobilized on short time scales and contribute to a carbon cycle climate feedback here we synthesize the characteristics and vulnerability of yedoma deposits by synthesizing studies on the yedoma origin and the associated organic carbon pool we suggest that yedoma deposits accumulated under periglacial weathering transport and deposition dynamics in non glaciated regions during the late pleistocene until the beginning of late glacial warming the deposits formed due to a combination of aeolian colluvial nival and alluvial deposition and simultaneous ground ice accumulation we found up to 130 gigatons organic carbon in yedoma parts of which are well preserved and available for fast decomposition after thaw based on incubation experiments up to 10 of the yedoma carbon is considered especially decomposable and may be released upon thaw the substantial amount of ground ice in yedoma makes it highly vulnerable to disturbances such as thermokarst and thermo erosion processes mobilization of permafrost carbon is expected to increase under future climate warming our synthesis results underline the need of accounting for yedoma carbon stocks in next generation earth system models for a more complete representation of the permafrost carbon feedback

predictive painting of 3d seismic volumes predictive painting is a numerical algorithm that spreads information in 3d volumes according to the local structure of seismic events the algorithm consists of two steps first local spatially variable inline and crossline slopes of seismic events are estimated by the plane wave destruction method next a seed trace is inserted in the volume and the information contained in that trace is spread inside the volume thus automatically painting the data space immediate applications of this technique include automatic horizon picking and flattening in applications to both prestack and poststack seismic data analysis synthetic and field data tests demonstrate the effectiveness of predictive painting

contemporary glacigenic inputs to the dust cycle the importance of glacigenic dust in the earth s system during glacial periods is widely acknowledged under contemporary conditions the world s largest dust sources are in low lying hot arid regions and this is where most aeolian research is focused however the processes of dust production and emissions are still operating in cold climate regions particularly in proglacial areas this paper assesses current understanding of the relationship between glacierised landscapes and dust emissions and inputs to the global dust cycle it focuses on how elements in the glacial and aeolian geomorphic sub systems interact to determine the magnitude frequency and timing of aeolian dust emissions and on feedback mechanisms between the systems where they have been measured dust emission intensity and deposition rates in glacierised catchments are very high in some cases far exceeding those in lower latitudes however few studies span long time scales the impact of future glacier retreat on the balance between sediment supply availability and aeolian transport capacity and implications for glacigenic dust emissions is also considered this balance depends on relative spatial and temporal changes in meltwater suspended sediment concentration and wind strengths which promote dust emissions and patterns and rates of soil development and vegetation succession on recently deglaciated terrain which protect sediments from deflation retreat of the antarctic ice sheet could mean that in future glacigenic contributions to the dust cycle exceed those of non glacigenic sources in the southern hemisphere copyright 2012 john wiley sons ltd

a multi proxy analysis of two loess paleosol sequences in the northern harz foreland germany two loess paleosol sequences from the northern harz foreland hecklingen and zilly have been investigated in general loess paleosol sequences represent valuable terrestrial archives of regional environmental and climatic conditions during past glacial periods the study area is part of the northern european loess belt and was in the vicinity of the scandinavian ice sheet during the weichselian aiming towards a better understanding of the paleoenvironmental conditions during the weichselian in an area close to the scandinavian ice sheet results from grain size geochemical xrf cns color and magnetic susceptibility measurements are combined the findings demonstrate an increased input of aeolian material during the last glacial maximum and the last cover loess period which is in accordance to the theory of drier and colder conditions during this time frame further data reveal a strong input not only of loess but also of coarser material coming from a shorter distance during the last glacial maximum in both profiles material of the last glacial maximum clearly indicates a shift of wind direction towards easterly winds in hecklingen an enhancement of coarser material has been observed within the recent soil and mis 3 soil material since soil material that dates back to the mis 3 is present in the profile it can be assumed that surface processes were less intrusive during the mis 3 and 2 than in e g the lower rhine embayment and saxony c 2016 elsevier b v all rights reserved

loess accumulation in the tian shan piedmont implications for palaeoenvironmental change in arid central asia whilst correlations have been made between the loess of europe and china deposits in central asia have remained largely overlooked by scientific investigation the nature of the relationship between loess accumulation and palaeoclimate at the core of the eurasian loess belt is particularly poorly understood here we reconstruct palaeoenvironmental change in central asia over the last 40 ky based on data from the remizovka loess profile in the northern foothills of the tian shan in southern kazakhstan our interpretations are based on synthesis of chronostratigraphic colour and magnetic susceptibility data supported by chronostratigraphies from two additional sites nearby maibulak and valikhanova all three sites record substantially increased loess accumulation during late mis 3 into the global last glacial maximum glgm at remizovka increased loess flux occurred in two pulses at c 38 25 ka and 22 18 ka with the intervening period involving incipient pedogenesis at maibulak two loess pulses at c 40 30 ka and c 28 22 ka are separated by a weakly developed paleosol which may date to the same time as pedogenesis at remizovka there is additional possible periglacial influence at maibulak from c 40 33 5 ka at valikhanova there is some age overlap between paleosol and loess samples but overall loess accumulation appears to have increased at c 42 35 ka c 30 ka and the glgm with pedogenesis occurring 40 ka and c 32 ka at all three sites holocene loess accumulation is minimal this period is characterised by pedogenesis the chronostratigraphic variability between our sites highlights a need to interrogate climate driven models for loess formation in piedmont environments we interpret our data in the context of regional palaeoenvironmental archives to indicate that loess accumulation increased coeval with mis 3 glacial advance in the tian shan which was facilitated by northward expansion of the asian monsoon and associated increase in precipitation we hypothesise that increased ice volume impeded teleconnections with the temperate zone westerlies to the north these were compressed against the piedmont resulting in increased wind strength and facilitating increased loess flux peak loess accumulation during the glgm occurred under colder drier climatic conditions with reduced but sustained glacial ice volume and persistent influence of the westerlies in the arid central asian piedmont loess belt in the absence of more widespread reliably dated palaeoenvironmental records from the region our data become of critical importance for understanding past environmental conditions in central asia relative to elsewhere in eurasia and globally

the loess profile at albertirsa hungary improvements in loess stratigraphy by luminescence dating abstract a very detailed upper pleistocene record is exposed in a loess palaeosol sequence at the section at albertirsa in hungary luminescence dating was carried out to establish a more reliable chronological framework for the hungarian loess record the lowermost palaeosol of the section probably an equivalent of the mf2 horizon at the mende key section is superimposed on penultimate glacial loess an irsl age estimate of about 65 ka bp was determined for the lower part of this palaeosol indicating soil formation late in oxygen isotope stage ois 5 or early in ois 3 a significant hiatus most likely occurs in the lower part of the lower fossil soil the loess between the upper and and lower palaeosol yielded a mean luminescence age of about 50 ka bp the upper palaeosol is probably an equivalent of the mf1 horizon at the mende type section formed between 37 and 25 ka bp and so this palaeosol represents the hengelo and or denekamp interstadial of northwestern european stratigraphy the loess is intercalated by a humic horizon which yielded a mean luminescence age estimate between 21 and 19 ka at the albertirsa section

magnetic properties of loess grain size fractions from the section at paks hungary abstract the approximately 50 m thick loess palaeosol sequence at paks brickyard hungary was deposited largely during the brunhes normal polarity chron and its magnetic properties resemble those of similar sections in europe central asia and china in order to get information on the grain size dependence of some of the magnetic parameters two loess and two palaeosol samples were separated into a number of grain size fractions the separation method employs consecutive sedimentation and centrifugation steps performed on bulk samples suspended in water and diluted with calgon ten grain size fractions were obtained ranging from 50 m down to 10 nm several magnetic parameters of the different grain size fractions have been measured at room temperature low field susceptibility hysteresis parameters and at low temperature susceptibility and thermoremanent magnetisation they show a strong grain size dependence for the ferromagnetic minerals low temperature measurements allow discrimination of the paramagnetic vs the ferromagnetic signal and give information on the grain size distribution of the very fine ferromagnetic minerals and on the mineral types carrying the magnetic signal strong relationships between weathering processes destruction of paramagnetic minerals and possibly iron hydroxides and enhancement of the ferromagnetic signal are observed

velocity inversion by differential semblance optimization differential semblance optimization dso is an approach to inversion of reflection seismograms which avoids the severe convergence difficulties associated with nonlinear least squares inversion the method exploits both moveout and amplitude characteristics of reflections we have implemented a version appropriate to plane wave p tau seismograms and layered constant density acoustic earth models theoretical and numerical analyses of this version of dso indicate that stable and reasonably accurate estimates of both velocity trend and reflectivity can be derived to test dso further we applied it to a marine data set from the gulf of mexico where the method produced results which compare favorably to well log information the method can be extended to incorporate laterally heterogeneous velocity models

velocity estimation by image focusing analysis migration velocity can be estimated from seismic data by analyzing focusing and defocusing of residual migrated images the accuracy of these velocity estimates is limited by the inherent ambiguity between velocity and reflector curvature however velocity resolution improves when reflectors with different curvatures are present image focusing is measured by evaluating coherency across structural dips in addition to coherency across aperture azimuth angles the inherent ambiguity between velocity and reflector curvature is directly tackled by introducing a curvature correction into the computation of the semblance functional that estimates image coherency the resulting velocity estimator provides velocity estimates that are 1 unbiased by reflector curvature and 2 consistent with the velocity information that is routinely obtained by measuring coherency over aperture azimuth angles applications to a 2d synthetic prestack data set and a 2d field prestack data set confirm that the proposed method provides consistent and unbiased velocity information they also suggest that velocity estimates based on the new image focusing semblance may be more robust and have higher resolution than estimates based on conventional semblance functionals applying the proposed method to zero offset field data recorded in new york harbor yields a velocity function that is consistent with available geologic information and clearly improves the focusing of the reflectors

loess and soils in the eastern ebro basin abstract wind blown sandy and silty deposits were formed during the late quaternary in the ne iberian peninsula they are the most significant in the west mediterranean region together with those described in the tagus river basin iberian south subplateau forming small scattered patches across parts of the se ebro depression and sw catalan mediterranean range two major depositional environments are distinguished the first largest outcrop covers the lower ebro reaches on the se border of the ebro depression the prelitoral coastal range and the mora d ebre basin a second outcrop to the north consists of a few patches scattered over a wide amphitheatre surrounding the western tributaries of the segre river from the wind exposed segria platforms to the almenara range in its northernmost part they consist of highly sorted fine sands and silts 1 12 m thick though most typically 3 4 m thick and coarser than typical loess they are highly uniform lack any sedimentary structures and are pale ochre the deposits are calcareous 30 45 caco3 basic to alkaline and with some soluble salts five selected sequences of primary loess namely mas de l alerany tivissa guiamets batea and almenara were studied to ascertain deposit characteristics and soil development all sections show a consistent vertical granulometric variability that may be attributed to wind intensity changes and hinders the recognition of spatial particle size distribution pedogenesis is mostly related to calcium carbonate redistribution which accumulates as nodules large rhizocretions or biogenic calcite secondary gypsum batea and almenara sequences is probably related to primary gypsum blown from the source areas that was redistributed by leaching and precipitation at the bottom of the profiles in a few places mas de l alerany outcrop a fersialitic rubefacted recalcified soil indicates the presence of an older generation of loess while the dominant wnw winds and particle coarseness suggest that the loess originates from nearby alluvial fans and fluvial plains the presence of gypsum and mg anomalies may be evidence of more distant sources of the central ebro depression and ondara corb alluvial fans optical stimulated luminiscence osl ages for the more recent deposits guiamets batea almenara are between 18 and 34 ka while the old mas de l alerany sequence is more than 115 ka these ages indicate loess deposition during the last cold phases of the quaternary and with pedogenesis occuring during warm interglacial periods

separation and imaging of seismic diffractions using migrated dip angle gathers abstractcommon reflection angle migration can produce migrated gathers either in the scattering angle domain or in the dip angle domain the latter reveals a clear distinction between reflection and diffraction events we derived analytical expressions for events in the dip angle domain and found that the shape difference can be used for reflection diffraction separation we defined reflection and diffraction models in the radon space the radon transform allowed us to isolate diffractions from reflections and noise the separation procedure can be performed after either time migration or depth migration synthetic and real data examples confirmed the validity of this technique

a comparison of diffraction imaging to incoherence and curvature detecting small subsurface features such as faults fracture swarms steep reef edges and channel edges is a routine task in seismic interpretation common seismic attributes used for this task such as curvature and incoherence are derived from conventional images containing both reflections and diffractions an emerging alternative approach is to interpret these edge features using the diffraction imaging technique which images diffracted energy separately a diffraction imaging volume is generated by separating specular reflections from diffractions in an unmigrated volume followed by migration of those diffractions different methods can be used to separate diffractions from reflections on unmigrated data in a case history they are separated with a plane wave destruction pwd filter an evaluation of diffraction imaging performance is applied to a 3d seismic data set from the cooper basin of australia diffraction imaging horizon maps are compared with corresponding maps made from incoherence and curvature volumes the resolution and the ability to detect faults fractures and channel edge features are compared the results show that diffraction imaging provides superior vertical and spatial resolution over conventional incoherence and curvature attributes for mapping faults and stratigraphy

australian dust deposits modern processes and the quaternary record abstract dust raising and transport are common and important processes in australia today the aridity of the australian continent and high climatic variability result in widespread dust raising in the arid and semi arid areas and transport to the humid margins and surrounding oceans the supply of erodible particles appears to be the greatest limitation on total flux of transported dust dust raising is greatest in the lake eyre basin including the simpson desert and murray darling basin where internal drainage renews supplies of fine particles to the arid zone in the west and northwest dust entrainment is low despite considerable aridity the marine record of dust flux shows at least a threefold increase in dust flux compared with the holocene in the last glacial maximum in both tropical and temperate australia driven by weakened australian monsoon rains and drier westerly circulation respectively despite the widespread confirmation of aeolian dust deposits in southeastern and southwestern australia dated or quantified records are extremely rare the dominant model of australian dust deposits the clay rich parna is shown to be poorly substantiated while modern and ancient dust deposits examined in detail are shown to bear a strong similarity to conventional definitions of loess