least squares reverse time migration with a wavefield separation imaging condition and updated source wavefields abstractdirectly imaging steeply dipping fault zones is difficult for conventional migration including reverse time migration rtm we developed a new least squares rtm lsrtm method to directly image steeply dipping fault zones the method uses a wavefield separation imaging condition and updated source wavefields during each iteration our new imaging method produces horizontal looking images that show mostly steeply dipping fault zones conventional least squares rtm does not update source wavefields and cannot directly image vertical fault zones we numerically determined that it is crucial to update source wavefields to image steeply dipping fault zones using synthetic seismic data we proved that our new lsrtm method can directly image steeply dipping fault zones with dipping angles up to 90 compared with conventional lsrtm our lsrtm method was less sensitive to the smoothness and the velocity error of the initial migration velocity model

linearized inversion of seismic reflection data this is the first of a series of papers giving the solution of the inverse problem in seismic exploration the acoustic approximation is used together with the assumption that the velocity field has the form the forward problem is then linearized thus neglecting multiple reflected waves and the inverse problem of estimating is set up its rigorous solution can be obtained using an iterative algorithm each step consisting of a classical kirchhoff migration hyperbola summation plus a classical forward modeling step circle summation

depth image focusing in traveltime map based wide angle migration wide aperture prestack depth migration requires application of challenging and time consuming velocity analysis and depth focusing collectively referred to here as depth focusing we present an approach to depth focusing using 1 a detailed starting velocity model obtained by a 1 d transformation of the first arrival times followed iteratively by 2 interactive analysis of the common image gathers 3 computation of coherency attributes of the wavefield in the depth domain and 4 2 d traveltime tomography to update the background velocity model we employ two interactive method of migration velocities refinement in the first method similar to the common midpoint velocity spectrum approach residual velocity updates are picked directly from the common image gathers in another method analogous to the common velocity stacks we pick the velocity updates from the areas of maximum coherency in depth sections that are migrated using rescaled traveltime maps both types of migration velocity picks

hierarchies and spatial scale in process geomorphology a review abstract the form and functioning of a geomorphic system is the end product of a set of interacting processes which operate at a large variety of spatial and temporal scales an appreciation of the nested hierarchical structure of geomorphic systems offers insight into the effect of scale in process geomorphology a literature review led to the formulation of a series of propositions concerning the spatial scale problem in process geomorphology these propositions are presented in a theoretical framework indicating their association central to the spatial scale problem in process geomorphology is that a geomorphic system must be viewed in its complex hierarchicl context every geomorphic system consists of an array of ever smaller lower level systems and is at the same time part of a sequence of ever larger higher level system in a geomorphic system there exists a similarity between the scales of process and form furthermore within a geomorphic system there is a similarity between spatial and temporal scales so that the timespan to present system behaviour and morphology increases with system size in a geomorphic system differences occur in the sensitivity of morphology to changing process conditions depending on the time elapsed since a change in process conditions morphology in a geomorphic system may be either polygenetic when only partial adjustment of the morphology i e only at smaller scales has occurred or characteristic of the process domain when all aspects of morphology i e at all scales are adjusted to present process conditions in the latter case dominance of landscape evolution by high frequency low magnitude process results in a smooth landscape having small scale irregularities whereas dominance by low frequency high magnitude processes produces an irregular landscape having large scale irregularities when spatial scale is held constant the model of evolution of a geomorphic system varies with the timescale of interest conversely when temporal scale is held constant the model of evolution varies with the spatial scale of interest in both cases the canon fixed rules and options of a geomorphic system vary with the scale temporal or spatial of interest the linkages between spatial and temporal scale and between the scales of form and process of geomorphic systems lead to four additional points first whether or not an event is catastrophic depends on the hierarchical level of the geomorphic system second because of increased travel time and a larger variety of possible pathways differences between the temporal patterns and material properties of input and output increase with the hiirarchical level and scale of a geomorphic system third frequent small scale processes may cause infrequent large scale events when viewed at the same hierarchical level fourth and last differences between geomorphic systems at the same level are controlled by variables varying over distances equal to or smaller than the distance between the system but equal to or larger than the spatial dimensions of the systems

on the relationship between climate and neandertal fire use during the last glacial in south west france abstract both environmental and cultural factors dictate how when and where hunter gatherers use fire in the landscape as well as how well evidence for any one fire will preserve in the archaeological record variability in the production and preservation of anthropogenic fire traces can potentially skew our perception of fire use in the past with this in mind the research presented in this article weighs in on the debate concerning neandertal fire use and fire making specifically the assertion that neandertals were unable to produce fire for themselves sandgathe et al 2011a 2011b this hypothesis is based on the inferred correlation between climatic deterioration concurrent lowering of lightning ignited fire frequencies and reduced signals for fire use in layers presumably deposited during the lower pleniglacial marine isotope stage 4 at the middle palaeolithic sites of roc de marsal and pech de l aze iv aquitaine basin southwestern france the logic being that if neandertals could produce fire at will fire use signals would remain largely consistent throughout the deposits despite there being limited access to natural fires in the landscape during this colder period this review challenges these assertions at multiple scales by looking at regional lightning and fire regime dynamics comparing the fire signals observed at roc de marsal and pech de l aze iv to those of other sites nearby and around france and exploring the various environmental and cultural factors likely influencing these signals ultimately the data suggests that estimated reductions in lightning frequencies and fire regime during the lower pleniglacial and colder stadial periods in general were not adequate to severely limit neandertal access to natural fire while possible artefactual evidence for neandertal fire making challenges the assumption that they were at all reliant on lightning ignited fire moreover at the nearby neandertal site of combe grenal the majority of the layers exhibiting evidence of fire use have cold climatic signals suggesting the fire use trends observed at roc de marsal and pech de l aze iv are potentially local expressions of changes in regional site use patterns possibly brought on by increased reliance on highly mobile migratory reindeer prey species and reductions in local woodfuel availability during cold periods other factors potentially reducing the archaeological visibility of cold climate fire use are discussed

sensitivity of post hurricane beach and dune recovery to event frequency the recovery of santa rosa island in northwest florida is characterized following hurricane katrina september 2005 which was preceded by hurricanes ivan 2004 and dennis 2005 beach and dune recovery were quantified to the east and west of pensacola beach through a comparison of lidar data collected immediately following hurricane katrina and in july 2006 after almost a year of recovery east of pensacola beach the santa rosa unit the shoreline retreated by an average of 64 m during the 2004 2005 hurricane season and recovered by an average of 19 m to the west of pensacola beach the fort pickens unit the shoreline retreated by an average of 30 m and while no significant shoreface recovery was observed the presence of vegetation on low profile dunes promoted backshore accretion it is found that beachface recovery in the santa rosa unit and backshore accretion in the fort pickens unit occurred at the widest sections of the island where the pre storm profile volume had been relatively large and overwash penetration was at a minimum the narrow sections of the island between cuspate headlands had a smaller profile volume before the storms leading to greater overwash penetration and in some cases island breaching in both sections which limited the volume of sediment available for shoreface recovery the alongshore variation in recovery is not only related to the island width but also the offshore bathymetry height of the pre storm dunes and the overwash penetration if sufficient time is allowed for the return of vegetation and the recovery of the dunes the variations in storm impact observed during hurricane ivan will be reinforced during subsequent storms in this respect the level of impact during subsequent storms and the ability of the island to recover will depend on the frequency of storm events copyright 2009 john wiley sons ltd

recent stabilization of active sand dunes on the canadian prairies and relation to recent climate variations the historical activity of sand dunes on the southern canadian prairies was investigated in order to determine the relation with recent climate variations changes in dune activity were determined from historical aerial photographs at seven sites with active parabolic dunes in saskatchewan and manitoba the methodology developed combines digital image processing and geographical information system gis analysis to measure changes in dune activity from the aerial photographs as well as correlation analysis to determine the relation between dune activity and climate variations overall dune activity has been decreasing since the early to mid 1900s as evidenced by greater vegetation colonization than sand dune migration or reactivation the decrease in dune activity is significantly correlated with decadal scale variations in aridity and is coincident with a decrease in annual wind speed evidence suggests that this response is superimposed on a longer trend towards stabilization possibly in place since the late 1700s taken together the effect of this complex response is that dune recovery on the southern canadian prairies is prolonged well after an initial disturbance and therefore gives the impression of anomalous levels of activity for extended periods thereafter for this reason dune mobility indices predicated on short term climate variations years to decades do not fully describe the present level of dune activity on the southern canadian prairies

post storm beach and dune recovery implications for barrier island resilience abstract the ability of beaches and dunes to recover following an extreme storm is a primary control of barrier island response to sea level rise and changes in the frequency and or magnitude of storm surges whereas erosion of the beach and dune occurs over hours and days it can be years to decades before the beach and dune are able to recover to their pre storm state as a consequence there are numerous descriptions of near instantaneous beach and dune erosion due to storms the immediate onshore transport of sand and the initial phases of beach and dune recovery following a storm but a paucity of data on long term beach and dune recovery a combination of previously published data from galveston island texas and new remotely sensed data from santa rosa island florida is used in the present study to quantify the rate of dune recovery for dissipative and intermediate beach types respectively recovery of the dune height and volume on galveston island was observed within two years following hurricane alicia 1983 and was largely complete within six years of the storm despite extensive washover in contrast the dunes on santa rosa island in northwest florida began to recover four years after hurricane ivan 2004 and only after the profile approached its pre storm level and the rate of vegetation recovery regrowth was at a maximum results show that complete recovery of the largest dunes in height and volume will take approximately 10 years on santa rosa island which suggests that these sections of the island are particularly vulnerable to significant change in island morphology if there is also a change in the frequency and magnitude of storm events in contrast the areas of the island with the smallest dunes before hurricane ivan exhibited a rapid recovery but no further growth in profile volume and dune height beyond the pre storm volume and height despite continued recovery of the largest dunes to their pre storm height a change in storm magnitude and or frequency is a potential threat to barrier island resilience particularly for those sections of the island where dune recovery has historically taken the longest time further study is required to determine how and why dune recovery varies for the dissipative and intermediate beaches of galveston island and santa rosa island respectively

least squares reverse time migration in a matrix based formulation this paper describes least squares reverse time migration the method provides the exact adjoint operator pair for solving the linear inverse problem thereby enhancing the convergence of gradient based iterative linear inversion methods in this formulation modified source wavelets are used to correct the source signature imprint in the predicted data moreover a roughness constraint is applied to stabilise the inversion and reduce high wavenumber artefacts it is also shown that least squares migration implicitly applies a deconvolution imaging condition three numerical experiments illustrate that this method is able to produce seismic reflectivity images with higher resolution more accurate amplitudes and fewer artefacts than conventional reverse time migration the methodology is currently feasible in 2 d and can naturally be extended to 3 d when computational resources become more powerful

biogeomorphic model of dunefield activation and stabilization on the northern great plains abstract a conceptual model is proposed for the activity of sand dune systems on the northern great plains that incorporates vegetation growth theory and geomorphic system theory dunefield activity is modeled as a cyclic phenomenon alternating between active and stable states with the latter as the system state attractor the model is divided into two constituent parts an activation model and a stabilization model the activation model is qualitative and describes the transition from stable to active dunes as the result of a climatic perturbation such as drought that decreases vegetation cover the intensity and duration of the climatic perturbation determines the rate of decline of vegetation cover the stabilization model is quantitative and describes the transition from active to stable dunes using a logistic model of vegetation growth small perturbations during stabilization can prolong the duration of recovery enabling dunes to remain active well after the initial perturbation despite the geographic focus of this study the model appears applicable to a variety of environments where dune activity is limited in part by vegetation cover

ash deposits in hayonim and kebara caves israel macroscopic microscopic and mineralogical observations and their archaeological implications abstract a study of the hearths and ash layers preserved in hayonim and kebara caves israel showed that they are composed of one or several different minerals these include the polymorph of caco3 calcite a variety of phosphate minerals and a suite of siliceous minerals the major component of the latter are siliceous aggregates that are present in wood detailed studies of the mineral associations in these fossil ash layers as well as in fresh wood ash using optical and scanning electron microscopy in the back scattered electron mode together with elemental analyses showed that ash in these caves undergoes a series of diagenetic changes the best preserved ash layers resemble fresh ash and are composed mainly of calcite with minor amounts of siliceous minerals the calcite reacts with phosphate rich solutions to form carbonated apatite and with time the latter dissolves and a variety of other phosphate containing minerals form with each diagenetic change some of the more soluble minerals are lost and ultimately only the ash derived siliceous minerals remain in both caves there are local accumulations of such siliceous minerals that are metres thick in fact ash derived minerals in general are major components of the sediments in both kebara and hayonim caves their diagenesis involves a hugh reduction in volume which in turn may have important effects on the geological structures and stratigraphy of the sediments the changing mineralogy of the sediments due to diagenesis complicates the use of present day estimates of radiation content of the sediments for correcting age estimates by thermoluminescence and electron spin resonance finally the presence of the relatively stable ash derived siliceous minerals in a sedimentary layer in other caves could be a useful means of identifying the presence of ash in other archaeological sites where macroscopic hearth features are absent

aeolian system responses to global change challenges of scale process and temporal integration aeolian sediment systems are extensive components of the earth s surface not just in today s active desert environments but in coastal locations and as presently stable loess and peri desert ergs all these systems are subject to potentially significant 21st century changes in dynamics due to global warming impacts on atmospheric circulation sediment moisture and vegetation cover but do we know enough in the critical areas of science to allow robust models of likely future dynamics to be developed since the establishment of modern aeolian science research has largely taken two divergent routes 1 small scale investigations of the processes of wind shear sediment entrainment and transportation and 2 landform and landscape analyses with bedform systems described and relationships to circulation explained an intermediate sedimentological route has generated attempts towards a more integrated understanding of system behaviour at a range of scales four recent developments provide the potential for more robust multiscale integrations of aeolian system behaviour these are 1 advances in empirical measurement that allow wind power and sediment flux relations to be better described 2 modelling of dune and dust dynamics and interactions with key controls 3 monitoring systems that allow high resolution observations of sediment flux variations to be recognized and aeolian deposit structures to be understood and 4 chronometric advances that permit the assessment of the frequency and drivers of dune system activity in the past we explore and analyse these methodological advances and their potential contribution to the multiscale integrations that are essential for better informed predictions of future global aeolian system dynamics considering whether the integration of these advances in reductionist and holistic elements of aeolian science represent an example of the effective application of the principles of earth system science copyright 2008 john wiley sons ltd

microstratigraphic and multi analytical evidence for advanced neanderthal pyrotechnology at abric romani capellades spain abstract the complexity of social behaviour by neanderthal communities is consolidated by illustrating the sophistication of fire linked activities in their home based contexts this was achieved by relating the microfacies analysis of cultural deposits to combustion structures at the abric romani capellades spain the geometry and nature of cultural microfacies from a selection of hearths and their surrounding empty areas were characterized in thin sections the related bulk fraction from the distinctive individual microstrata was extracted water sieved and examined under the binocular microscope the selective micro sampling was performed from the collection of undisturbed blocks in combustion structures of layer j 1995 excavation the procedure was applied to combustion structures from the lower layer o 2009 excavation the integrated micromorphological observation and binocular sorting allowed identification of a similar assemblage of components that are closely linked to distinctive anthropic microfacies individual grains were characterized by esem edax x ray diffraction and raman spectrometry x ray fluorescence analysis was performed on the host matrix the specific association of remarkable components cultural microfacies is identical for the combustion structures of layers o and j the four groups components identified comprise carbonaceous polymorphs allochthonous mineral clasts organo phosphatic compounds and native metals the phase association of organic and mineral phases allowed recognition of a common natural precursor rich in hydrocarbon species and metallic compounds that were probably extracted from a miocene source microscale analysis in thin sections linked the combustion microfacies to the transformation contexts of the metal rich carbonaceous precursors heat resistant polymers and graphitic components associated with wood ash are suggested to trace pyrolitic residues from flaming combustion the intimate mixing of the metal rich carbonaceous polymorphs to finely crushed heated bones allowed identification of pyrogenic transformations of the fossil fuel with fresh biomass analysis at microscale in thin sections linked the processed by products to finely prepared and meticulously consolidated surfaces showing distinctive colours yellow brown blue green red white and black the repeated surface preparation and their exceptional preservation at microscales illustrate the great concern of neanderthal occupants for maintaining the long term memory of their carefully designed home space the recognition of advanced pyrotechnology by using fossil fuels for lighting firing spatial design colouring in the combustion structures of abric romani incites speculation on the exceptional social status of this home based camp site further development of the microfacies multi analytical analysis should more deeply penetrate the social sophistication of neanderthal communities

seismic imaging of the crust and upper mantle using regularized joint receiver functions frequency wave number filtering and multimode kirchhoff migration 1 receiver functions provide an indispensable tool for producing discontinuity images of the crust and upper mantle from teleseismic earthquake arrivals however image quality can be significantly compromised by instabilities inherent in the deconvolution process and by irregularities in data coverage driven by source and or receiver geometries we present receiver function estimation and prestack migration techniques which both reduce receiver function deconvolution instability and produce regularized multimode receiver function images the receiver function estimation technique exploits frequency wave number filtering methods using frequency pseudowave number domain filtering of gathers to enhance arrivals with consistent moveout characteristics synthetic tests confirm robust recovery of features in the presence of high noise levels to process regularized receiver functions into accurate images of the subsurface seismic scattering potential we employ a regularized kirchhoff migration that migrates both direct and reverberated p to s converted modes to their correct subsurface locations the subsequent images can be stacked to mute mismigrated modes synthetic studies and model resolution tests demonstrate that this methodology is well suited to irregularly spaced stations and uneven data coverage and does not require the recording of a single earthquake at multiple stations

reconstructing the sedimentary history of lezetxiki ii cave basque country northern iberian peninsula using micromorphological analysis abstract micromorphological analysis is an invaluable research tool for reconstructing detailed depositional and post depositional processes of cave infill sequences and for providing paleoenvironmental insight in this work we present the results of a micromorphological and mineralogical study of the sedimentary sequence at the lezetxiki ii cave northern iberian peninsula the cave forms part of the lezetxiki archaeological complex which has yielded early middle palaeolithic tools and archaic human remains we have identified three main clastic sedimentary processes as being significant at lezetxiki ii 1 fluviokarst or runoff processes which are characterised by yellow sandy illite rich microfacies 2 infiltration processes which produce a massive red silty clay vermiculite rich microfacies and 3 inwash processes which generate a reworked illite and vermiculite rich silty sand microfacies the most common post depositional processes observed are calcite precipitation infilling pore spaces and compression structures derived from specific vertical loading events in order to improve the chronological framework of the sedimentary sequence at lezetxiki ii we have revised previous radiometric and relative dating results from faunal and archaeological remains and have dated the lowermost stratigraphic level using single grain thermally transferred optically stimulated luminescence dating sedimentation at the lezetxiki ii cave started during marine isotope stage mis 7 through fluviokarst processes we interpreted that runoff prevailed during mis 6 while soil infiltration processes became more significant towards the mis 5 optimum gradually inwash processes prevailed over infiltration until the end of the interglacial phase during the following glacial phases runoff and erosion dominated but were subsequently replaced by inwash processes during mis 1

spectral signatures of characteristic spatial scales and nonfractal structure in landscapes 1 landscapes are sometimes argued to be scale invariant or random surfaces yet qualitative observations suggest that they contain characteristic spatial scales we quantitatively investigate the existence of characteristic landscape scales by analyzing two dimensional fourier power spectra derived from high resolution topographic maps of two landscapes in california in both cases we find that spectral power declines sharply above a frequency that corresponds roughly to hillslope length implying that the landscape is relatively smooth at finer scales the spectra also show that both landscapes contain quasiperiodic ridge and valley structures and we derive a robust measure of the ridge valley wavelength by comparing the spectra with the statistical properties of spectra derived from randomly generated topography we show that such uniform valley spacing is unlikely to occur in a random surface we describe several potential applications of spectral analysis in geomorphology beyond the identification of characteristic spatial scales including a filtering technique that can be used to measure topographic attributes such as local relief at specific scales or in specific orientations

least squares reverse time migration inversion based imaging toward true reflectivity abstract as an inversion based imaging algorithm least squares reverse time migration lsrtm refines seismic images toward true reflectivity earth models it overcomes the shortcomings of conventional migration algorithms via iterative least squares inversion to gradually correct migration errors lsrtm also suppresses side lobes of image wavelets to generate images with high spatial resolution recovered weak events and steep dips are enhanced during iterations with balanced illumination the true amplitude behavior of lsrtm will greatly benefit quantitative seismic interpretations lsrtm can be a practical image domain broadband solution to generate high resolution images with fine layers as well as accurate complex structures

combustion structures of archaeological level o and mousterian activity areas with use of fire at the abric romani rockshelter ne iberian peninsula abstract the human use of fire generates a cultural sedimentary record that can be used to characterize prehistoric activity areas the aim of this paper is to develop a field guide for recognizing and describing combustion structures the use of fire as suggested by the results of ethnoarchaeological and prehistoric archaeological studies has served as the foundation for the analytical design of the field observations of the combustion structures at the abric romani rockshelter flat and concave combustion structure types have been uncovered in archaeological level o the systematic recording of the sedimentary and dimensional attributes of the combustion structures can be used as empirical evidence with which to characterize the use of fire differences in the use of fire represent a significant finding in the cultural repertoires of neanderthals recognizing and recording the specific organizational patterns of these activity areas such as fire use in sleeping and resting activity areas indicate the definitive emergence of home bases in the spatial record of the living floors of the archaic human groups

deconstructing a polygenetic landscape using lidar and multi resolution analysis abstract it is difficult to deconstruct a complex polygenetic landscape into distinct process form regimes using digital elevation models dems and fundamental land surface parameters this study describes a multi resolution analysis approach for extracting geomorphological information from a lidar derived dem over a stabilized aeolian landscape in south texas that exhibits distinct process form regimes associated with different stages in landscape evolution multi resolution analysis was used to generate average altitudes using a gaussian filter with a maximum radius of 1 km at 20 m intervals resulting in 50 generated dems this multi resolution dataset was analyzed using principal components analysis pca to identify the dominant variance structure in the dataset the first 4 principal components pc account for 99 9 of the variation and classification of the variance structure reveals distinct multi scale topographic variation associated with different process form regimes and evolutionary stages our results suggest that this approach can be used to generate quantitatively rigorous morphometric maps to guide field based sedimentological and geophysical investigations which tend to use purposive sampling techniques resulting in bias and error

true amplitude migration of 2d synthetic data true amplitude ta migration which is a kirchhoff type modified weighted diffraction stack recovers possibly complex angle dependent reflection coefficients which are important for amplitude versus offset avo inversion the method can be implemented using existing prestack or post stack kirchhoff migration and fast green s function computation programs here it is applied to synthetic single shot and constant offset seismic data that include post critical reflections complex reflection coefficients and caustics comparisons of the amplitudes of the ta migration image with theoretical reflection coefficients show that the possibly complex angle dependent reflection coefficients are correctly estimated

a 10 000 year record of dune activity dust storms and severe drought in the central great plains dune fi elds and loess deposits of the great plains of north america contain stratigraphic records of eolian activity that can be used to extend the short observational record of drought we present a 10 000 yr reconstruction of dune activity and dust production in the central great plains region based on 95 optically stimulated luminescence ages the integration of data from both eolian sand and loess is an important new aspect of this record clusters of ages defi ne episodes of extensive eolian activity which we interpret as a response to frequent severe drought at 1 0 0 7 ka and 2 3 4 5 ka with peaks centered on 2 5 and 3 8 ka sustained eolian activity occurred from 9 6 to 6 5 ka parts of this record may be consistent with hypotheses linking holocene drought to sea surface temperature anomalies in the pacifi c or atlantic oceans or to the el nino southern oscillation phenomenon but the record as a whole is diffi cult to reconcile with any of these hypotheses

automated landslide mapping using spectral analysis and high resolution topographic data puget sound lowlands washington and portland hills oregon abstract landslide inventory maps are necessary for assessing landslide hazards and addressing the role slope stability plays in landscape evolution over geologic timescales however landslide inventory maps produced with traditional methods aerial photograph interpretation topographic map analysis and field inspection are often subjective and incomplete the increasing availability of high resolution topographic data acquired via airborne light detection and ranging lidar over broad swaths of terrain invites new automated landslide mapping procedures we present two methods of spectral analysis that utilize lidar derived digital elevation models of the puget sound lowlands washington and the tualatin mountains oregon to quantify and automatically map the topographic signatures of deep seated landslides power spectra produced using the two dimensional discrete fourier transform and the two dimensional continuous wavelet transform identify the characteristic spatial frequencies of deep seated landslide morphologic features such as hummocky topography scarps and displaced blocks of material spatial patterns in the amount of spectral power concentrated in these characteristic frequency bands highlight past slope instabilities and allow the delineation of landslide terrain when calibrated by comparison with detailed independently compiled landslide inventory maps our algorithms correctly classify an average of 82 of the terrain in our five study areas spectral analysis also allows the creation of dominant wavelength maps which prove useful in analyzing meter scale topographic expressions of landslide mechanics past landslide activity and landslide modifying geomorphic processes these results suggest that our automated landslide mapping methods can create accurate landslide maps and serve as effective objective and efficient tools for digital terrain analysis

true amplitude seismic migration a comparison of three approaches knowledge of elastic parameter compressional and shear velocities and density contrasts within the earth can yield knowledge of lithology changes elastic parameter contrasts manifest themselves on seismic records as angle dependent reflectivity interpretation of angle dependent reflectivity or amplitude variation with offset avo on unmigrated records is often hindered by the effects of common depth point smear incorrectly specified geometrical spreading loss source receiver directivity as well as other factors it is possible to correct some of these problems by analyzing common reflection point gathers after prestack migration provided that the migration is capable of undoing all the amplitude distortions of wave propagation between the sources and the receivers a migration method capable of undoing such distortions and thus producing angle dependent reflection coefficients at analysis points in a lossless isotropic elastic earth is called a true amplitude migration the principles of tr

subsurface imaging using reversed vertical seismic profiling and crosshole tomographic methods a combined reversed vertical seismic profile rvsp crosshole and surface seismic experiment was performed to image the subsurface between two 1000 ft wells separated by 600 ft explosives were used as downhole sources and a 24 channel hydrophone streamer provided the downhole receivers surface shots were 1 3 lb dynamite charges and the surface receivers were vertical geophones rvsp data consisting of 48 offsets ranging from 25 ft to 1200 ft were processed with a ray tracing method to produce an equivalent stacked seismic section the crosshole data were processed with an sirt traveltime transmission tomography algorithm to produce a velocity cross section the stacked rvsp subsurface image and the crosshole tomography velocity cross section both have higher resolution than does the surface seismic image for example the velocity map from tomography exhibits a rapid lateral velocity change that is not resolved by surface seismic however all three methods agree within the limits of their common re

controls on coastal dune morphology shoreline erosion and barrier island response to extreme storms abstract the response of a barrier island to an extreme storm depends in part on the surge elevation relative to the height and extent of the foredunes which can exhibit considerable variability alongshore while it is recognized that alongshore variations in dune height and width direct barrier island response to storm surge the underlying causes of the alongshore variation remain poorly understood this study examines the alongshore variation in dune morphology along a 11 km stretch of santa rosa island in northwest florida and relates the variation in morphology to the response of the island during hurricane ivan and historic and storm related rates of shoreline erosion the morphology of the foredune and backbarrier dunes was characterized before and after hurricane ivan using empirical orthogonal function eof analysis and related through canonical correlation analysis cca the height and extent of the foredune and the presence and relative location of the backbarrier dunes varied alongshore at discrete length scales of 750 1450 and 4550 m that are statistically significant at the 95 confidence level cospectral analysis suggests that the variation in dune morphology is correlated with transverse ridges on the inner shelf the backbarrier cuspate headlands and the historical and storm related trends in shoreline change sections of the coast with little to no dune development before hurricane ivan were observed in the narrowest portions of the island between headlands west of the transverse ridges overwash penetration tended to be larger in these areas and island breaching was common leaving the surface close to the watertable and covered by a lag of shell and gravel in contrast large foredunes and the backbarrier dunes were observed at the widest sections of the island the cuspate headlands and at crest of the transverse ridges due to the large dunes and the presence of the backbarrier dunes these areas experienced less overwash penetration and most of the sediment from the beachface and dunes was deposited within the upper shoreface it is argued that this sediment is returned to the beachface through nearshore bar migration following the storm and that the areas with larger foredunes and backbarrier dunes have smaller rates of historical shoreline erosion compared to areas with smaller dunes and greater transfer of sediment to the washover terrace since the recovery of the dunes will vary depending on the availability of sediment from the washover and beachface it is further argued that the alongshore pattern of dune morphology and the response of the island to the next extreme storm is forced by the transverse ridges and island width through alongshore variations in storm surge and overwash gradients respectively these findings may be particularly important for coastal managers involved in the repair and rebuilding of coastal infrastructure that was damaged or destroyed during hurricane ivan

joint ray born least squares migration and simulated annealing optimization for target oriented quantitative seismic imaging a seismic processing workflow based on iterative ray born migration inversion and target oriented postprocessing of the migrated image is developed for fine scale quantitative characterization of reflectors the first step of the workflow involves linear iterations of the ray born migration inversion the output of the first step is a true amplitude migrated image parameterized by velocity perturbations in a second step postprocessing of the migrated image is performed through a random search with a very fast simulated annealing vfsa algorithm the forward problem of the global optimization is a simple convolutional model that linearly relates a vertical profile of the band limited migrated image after depth to time conversion to a 1d velocity model composed of a stack of homogeneous layers of arbitrary velocity and thickness the aim of the postprocessing is to eliminate the limited bandwidth effects of the source from the migrated image for resolution improvement and enhanced geological interpre

palaeoecology of neanderthals during dansgaard oeschger cycles in northeastern iberia abric romani from regional to global scale abstract the sequence from abric romani has provided several palaeoecological studies this paper presents a synthesis of the results yielded by palynology including the data from the entire non excavated deposits and the data obtained through the study of large mammals micromammals herpetofauna and anthracology from the excavated layers the palaeobotanical studies show that the sequence is mainly related to pine forests and near or within these dominant forests there were smaller plant formations and or secondary species with a mediterranean and or atlantic character nevertheless continuous forest did not dominate the entire region the fauna occupying the territory indicate open spaces in which seasonal grasslands proliferated dry assemblages in sunny areas and humid ones in mountain shadows the non excavated archaeological layers correspond to mis 4 initially characterized by temperate and humid conditions and thereafter cool and humid until hs 6 and mis 3 afterwards at the beginning of the mis 3 the dansgaard oeschger cycles 1500 yr rapid and abrupt climatic changes occurred during the deposition of the archaeological levels o n m l k and j later these events were interrupted by a cold and dry phase between ca 49 and 47 ka bp which affected levels ja i and h culminating with hs 5 finally this cold episode was followed by the hengelo interstadial or do 12 characterized by a temperate and humid climate identified in levels e and d

dune mobility and aridity at the desert margin of northern china at a time of peak monsoon strength wind blown sands were mobile at many sites along the desert margin in northern china during the early holocene 11 5 8 ka ago based on extensive new numerical dating this mobility implies low effective moisture at the desert margin in contrast to growing evidence for greater than modern monsoon precipitation at the same time in central and southern china dry conditions in the early holocene at the desert margin can be explained through a dynamic link between enhanced diabatic heating in the core region of the strengthened monsoon and increased subsidence in drylands to the north combined with high evapotranspiration rates due to high summer temperatures after 8 ka ago as the monsoon weakened and lower temperatures reduced evapotranspiration eolian sands were stabilized by vegetation aridity and dune mobility at the desert margin and a strengthened monsoon can both be explained as responses to high summer insolation in the early holocene

topographic elastic least squares reverse time migration based on vector p and s wave equations in the curvilinear coordinates elastic least squares reverse time migration has been applied to multi component seismic data to obtain high quality images however the final images may suffer from artefacts caused by p and s wave crosstalk and severe spurious diffractions caused by complex topographic surface conditions to suppress these crosstalk artefacts and spurious diffractions we have developed a topographic separated wavefield elastic least squares reverse time migration algorithm in this method we apply p and s wave separated elastic velocity stress wave equations in the curvilinear coordinates to derive demigration equations and gradient formulas with respect to p and s velocity for the implementation of topographic separated wavefield elastic least squares reverse time migration the wavefields gradient directions and step lengths are all calculated in the curvilinear coordinates numerical experiments conducted with the two component data synthetized by a three topographic layer with anomalies model and the canadian foothills model are considered to verify our method the results reveal that compared with the conventional method our method promises imaging results with higher resolution and has a faster residual convergence speed finally we carry out numerical examples on noisy data imperfect migration velocity and inaccurate surface elevation to analyse its sensitivity to noise migration velocity and surface elevation error the results prove that our method is less sensitive to noise compared with the conventional elastic least squares reverse time migration and needs good migration velocities as other least squares reverse time migration methods in addition when implementing the proposed method an accurate surface elevation should be obtained by global positioning system to yield high quality images

fuel origin and firing product preservation in archaeological occupation contexts abstract we intend here to examine the range of factors involved in the preservation at short to long term of firing byproducts with respect to the nature of combustion processes and the fuel origin our objective is to refresh the cultural and palaeoenvironmental relevance of combustion deposits the study is based on the comparison of two recent situations of natural fires and a selection of well preserved firing records from rockshelters and caves in diverse geographical and cultural contexts the recent analogues comprise a two year investigation of the 2012 july large forest fire at alt emporda northern cataluna spain and a study of the 2014 lightning struck pine tree allanche cantal france in situ characterization at micro to nanoscale of firing products has been performed using the sem eds in backscatter mode on individual grains and composite aggregates which were extracted by gentle water sieving from combustion microstrata and firing products meticulously sampled in the field the survey of the alt emporda firing record confirms the rapid loss of intact ashes and heating scars leaving after two years a regenerated soil without any obvious evidence of this fire except for scattered charcoal the study of allanche lightning struck pine tree shows that lightning produces a suite of robust components diagnostic of flash heating and plasma assisted combustion polymer filaments vitreous char metal coatings and singular minerals their durability expresses the refractory and hydrophobic properties of materials formed by transient heating and plasma processes the identification of similar robust components in all the firing products of the archaeological contexts tested here shows that plasma assisted combustion and flash heating exert a major role on the durability of firing records the archaeological combustion contexts are separated into two types of intact firing records 1 the ones with abundant mineralised charcoal vitreous char and metal coatings would trace the use of fuel acquired from wood affected by a lightning strike 2 the thick white ash with polymer films refractory minerals and metal coatings would indicate wood fuel collected during periods of active aeroplasma processes in the atmosphere due to increased dust loading and intense ionization the study is suggested to offer a challenging perspective to elucidate further the role that lightning and plasma processes exerted on ancestral pyrotechnology by occasionally providing wood fuel resources of long durability low degradability and high calorific power

geospatial technologies and digital geomorphological mapping concepts issues and research geomorphological mapping plays an essential role in understanding earth surface processes geochronology natural resources natural hazards and landscape evolution it involves the partitioning of the terrain into conceptual spatial entities based upon criteria that include morphology form genetics process composition and structure chronology environmental system associations land cover soils ecology as well as spatial topological relationships of surface features landforms historically the power of human visualization was primarily relied upon for analysis introducing subjectivity and biases with respect to selection of criteria for terrain segmentation and placement of boundaries this paper reviews new spatio temporal data and geocomputational approaches that now permit earth scientists to go far beyond traditional mapping permitting quantitative characterization of landscape morphology and the integration of varied landscape thematic information numerous conceptual theoretical and information technology issues are at the heart of digital geomorphological mapping dgm and scientific progress has not kept pace with new and rapidly evolving geospatial technologies consequently new capabilities exist but numerous issues have not been adequately addressed therefore this paper discusses conceptual foundations and illustrates how geomorphometry and mapping approaches can be used to produce geomorphological information related to the land surface and landforms process rates process form relationships and geomorphic systems

principal component spectral analysis spectral decomposition methods help illuminate lateral changes in porosity and thin bed thickness for broadband data an interpreter might generate 80 or more somewhat redundant amplitude and phase spectral components spanning the usable seismic bandwidth at 1 hz intervals large numbers of components can overload not only the interpreter but also the display hardware we have used principal component analysis to reduce the multiplicity of spectral data and enhance the most energetic trends inside the data each principal component spectrum is mathematically orthogonal to other spectra with the importance of each spectrum being proportional to the size of its corresponding eigenvalue principal components are ideally suited to identify geologic features that give rise to anomalous moderate to high amplitude spectra unlike the input spectral magnitude and phase components the principal component spectra are not direct indicators of bed thickness by combining the variability of multiple components principal component spectra highlight stratigraphic features that can be interpreted using a seismic geomorphology workflow by mapping the three largest principal components using the three primary colors of red green and blue we could represent more than 80 of the spectral variance with a single image we have applied and validated this workflow using a broadband data volume containing channels draining an unconformity which was acquired over the central basin platform texas u s a principal component analysis reveals a channel system with only a few output data volumes the same process provides the interpreter with flexibility to remove any unwanted high amplitude geologic trends or random noise from the original spectral components by eliminating those principal components that do not aid in delineation of prospective features with their interpretation during the reconstruction process

continual fire making by hominins at gesher benot ya aqov israel this paper presents the culmination of an extensive study of fire use at the early and early middle pleistocene site of gesher benot ya aqov using software available in the gis package we have examined the spatial distribution of burned and unburned flint microartifacts from eight acheulian archaeological horizons the results of this study demonstrate that the burned microartifacts are never evenly distributed and dense concentrations are observed the circumstances that introduced these burned flint artifacts to the archaeological layers are examined suggesting that anthropogenic rather than natural fires are responsible for the observed patterns as the evidence for the use of fire is recorded throughout the long stratigraphic sequence it seems that fire was continually used by the acheulian hominins of the site this repetitive use of fire indicates that the hominins of gesher benot ya aqov had a profound knowledge of fire making enabling them to make fire at will

the black layer of middle palaeolithic combustion structures interpretation and archaeostratigraphic implications certain aspects of the formation processes of simple flat archaeological combustion structures such as those present in the middle palaeolithic record remain unexplained such kind of combustion structures are commonly affected by postdepositional agents and often their only distinct well preserved component is a thin black lens on the ground hence understanding the nature of this black lens is essential towards archaeological interpretation from an interdisciplinary microstratigraphic approach we present a case study in which for an entire experimental series of flat combustion structures the black layer represents the fire altered topsoil on which the fire was made parallel analysis of archaeological middle palaeolithic combustion structures from the site of el salt alicante spain reveal similar patterns leading to significant implications for archaeological interpretation in the light of these results special attention must be paid to the formation processes of flat middle palaeolithic combustion features as black layers and the material contained in them are not necessarily linked with combustion but with preceding activities or events in such cases black layers represent intact remnants of occupation surfaces concealing significant behavioural and palaeoenvironmental information relevant to the reconstruction of middle palaeolithic societies

middle holocene drought on the southern high plains abstract the climate of the southern high plains during the middle holocene is indicated by data from a variety of sources stratigraphic geomorphic and pedologic research at six localities in draws several dune sites and one playa lake basin show that widespread eolian erosion and sedimentation began in some areas by 9000 yr b p and culminated 6000 4500 yr b p probably because of warmer drier conditions that reduced the vegetative cover archaeological investigations at three sites provide evidence for the excavation of wells at this time apparently because of a declining water table studies of a few vertebrate and invertebrate faunas also indicate warming and drying in the middle holocene climate models and very limited isotopic data from bison bone suggest that summers in the middle holocene were warmer than present with reduced effective precipitation all lines of evidence indicate that the southern high plains was subjected to prolonged drought in the middle holocene with a maximum between 6500 and 4500 yr b p conforming climatically and chronologically to the altithermal

archaeological soil and pollen analysis of experimental floor deposits with special reference to butser ancient farm hampshire uk archaeological stratigraphies that may contain floors are often encountered for more than a decade soil micromorphologists working on archaeological sequences have benefited from having access to reference thin sections of ethnoarchaeological and experimental floors including those from the floors of iron age houses reconstructed by the late dr peter reynolds at butser ancient farm hampshire uk this paper reports upon experimental studies mainly carried out at butser during 1990 95 and their suggested application to microstratigraphic and microfacies analysis of occupation sites sampling at butser in 1990 was very much a rescue operation nevertheless fundamental differences in soil micromorphology were found between domestic house beaten floor deposits and those formed in a stable these differences were also reflected in the parallel study of pollen from these deposits with microchemical analyses helping to explain anomalous pollen preservation in the unsuitable soil at butser the limited bulk chemical study produced less clear results but when compared with findings from some roman and early medieval sites in london showed that the chemical trends hinted at butser are probably replicated in some ancient floors a preliminary interdisciplinary study of samples from the london guildhall clearly suggested the potential of such microstratigraphical and microfacies analyses and intimates at the potential of attaining rigorous consensus interpretations stable floor deposits are both organic and phosphate rich with homogeneous soil micromorphological and pollen characteristics beaten floors are much more mineralogenic and heterogeneous in terms of their microfabric and pollen that also indicate trampling in of a wide variety of allocthonous materials the last commonly responsible for raised magnetic susceptibility at archaeological sites these findings prove the worth of the ethnoarchaeological simulations carried out at the moel y gar stable and domestic pimperne house this microfacies approach is viewed as complementary to site reconstruction through macrofossil analysis of beetles and plant remains especially where sites are being investigated at the microstratigraphic level the phosphate content of stabling deposits may allow preservation of pollen in what may otherwise be deemed unsuitable material as demonstrated at butser

site formation dynamics and human occupations at bolomor cave valencia spain an archaeostratigraphic analysis of levels i to xii 100 200 ka abstract the definition of temporal scales related to human occupations is one of the most important elements for the reconstruction of occupational patterns in palaeolithic sites the complex sedimentary formation processes usually present in rock shelters and cave deposits result in the overlapping of archaeological remains from different occupations and events in the same stratigraphic unit formed by the sum of cultural and natural episodes this common characteristic which is widely discussed in the specialised literature as a palimpsest phenomenon may lead to equivocal associations and interpretations of the archaeological assemblages therefore the analysis of these assemblages should include the definition of synchronous relations between activity episodes identified in the search for high temporal resolution units which allow the establishment of the most accurate interpretations of the archaeological assemblages from this perspective we discuss the interpretative potential of archaeostratigraphic analysis for the study of homogeneous sedimentary units frequently present in palaeolithic sites in which the palimpsest phenomenon is frequently present in the formational processes of the sedimentary deposit the bolomor cave archaeological site valencia spain with a sedimentary deposit composed of seventeen stratigraphical levels ranging from mis 9 to mis 5e ca 350 100 ka shows evidence of human activity in almost all levels in many cases the archaeological remains mainly bones lithics and hearths appear overlapped in wide deposits thus proving the repeated use of the cave by different human groups here we present the archaeostratigraphic analysis of the upper sedimentary sequence of bolomor cave ranging from level i to level xii mis 5e 6 in which several occupational phases have been identified from the tridimensional placement reconstruction of the entire archaeological record and the definition of existing periods of abandonment along the stratigraphic sequence the analyses are complemented with information that helps us to define these periods such as the site formation processes and carnivore tooth marked bones the aim of this study is to contribute to the palimpsest dissection debate based on the definition of high temporal resolution units for the analysis of archaeological assemblages

late holocene aeolian activity in the cimarron river valley of west central oklahoma abstract this investigation uses a multidisciplinary approach including geomorphic surface mapping soil stratigraphic analysis radiocarbon dating and optically stimulated luminescence osl dating to investigate the chronology of soil formation and aeolian activation periods recorded in ridge dune deposits as well as the spatial variability of aeolian processes during active aeolian episodes this study shows that aeolian landforms superimposed on fluvial terraces adjacent to the cimarron river in southeastern major county and northwestern kingfisher county oklahoma are the product of distinct late holocene climatic conditions in which periods of dune activity are episodic and accumulation of sediments is relatively rapid soil forming processes operated on the stabilized dunes during intervening periods we also demonstrate that the synthesis of geomorphic techniques soil stratigraphy 14c dating and osl dating can provide complimentary and high resolution data about aeolian activity in the southern plains

wavefront sets analysis of limited aperture migration sections although geophysical literature is quite rich in papers on migration there are only a few papers that treat lam limited aperture migration deterministic and stochastic criteria for the reconstruction of reflection interfaces in prestack migration were derived and demonstrated on synthetic and real data examples a real data set was acquired offshore the brazilian coast courtesy of petrobras the reconstruction of reflection interfaces in lam depends on the relative position of normal bundles as defined here and gradients to the reflection interfaces the derived stochastic criterion relates the variance of normal bundles to the variance of slowness in the medium these criteria will help the geophysicist to identify directly distorted regions caused by lam and those regions that are correctly migrated

late holocene dune migration on the south texas sand sheet abstract there are a wide variety of vegetated eolian depositional landforms associated with the south texas sand sheet attesting to the past dominance of eolian processes mapping identified two sets of parabolic dunes elongating with winds from the southeast and the northwest parabolic dunes elongated by northwesterly winds are older than ca 200 years and may be associated with eolian depositional events ca 2700 and or 2000 years ago the latest dune migration event associated with southeasterly winds occurred ca 200 years ago and at one site is inset into northwesterly extended parabolic dunes this period of dune migration may be coincident with particularly severe drought identified in the tree ring record centered at ad 1790 when the palmer drought severity index was 4 a threshold of dune movement may have occurred ca in the 11th 15th and 20th centuries when there are two or more consecutive years with a palmer drought severity index of

the dakhleh glass product of an impact airburst or cratering event in the western desert of egypt impact cratering is a ubiquitous geological process on the terrestrial planets meteorite impact craters are the most visible product of impact events but there is a growing recognition that large aerial bursts or airbursts should occur relatively frequently throughout geological time in this contribution we report on an unusual impact glass the dakhleh glass dg which is distributed over an area of 400 km 2 of the dakhleh oasis egypt this region preserves a rich history of habitation stretching back to over 400 000 years before the emergence of homo sapiens we report on observations made during recent fieldwork and subsequent analytical analyses that strengthen previous suggestions that the dg formed during an impact event the wide distribution and large size of dg specimens up to 50 cm across the chemistry e g cao and al2o3 contents up to 25 and 18 wt respectively the presence of lechatelierite and burnt sediments and the inclusion of clasts and spherules in the dg is inconsistent with known terrestrial processes of glass formation the age and other textural characteristics rule out a human origin instead we draw upon recent numerical modeling of airbursts to suggest that the properties of dg coupled with the absence of a confirmed crater can best be explained by melting of surficial sediments as a result of a large airburst event we suggest that glass produced by such events should therefore be more common in the rock record than impact craters assuming that the glass formed in a suitable preserving environment

ecogeomorphic state variables and phase space construction for quantifying the evolution of vegetated aeolian landscapes cellular automaton modelling for the simulation of dune field formation and evolution has developed progressively in aeolian geomorphology in the last decade or so a model that incorporates the effects of vegetation and its interactions with geomorphic landscape development the discrete ecogeomorphic aeolian landscapes decal model can replicate a number of important visual and qualitative aspects of the complex evolution of aeolian dune landscapes under the influence of vegetation dynamics in coastal environments a key challenge in this research area is the analysis and comparison of both simulated and real world vegetated dune landscapes using objective and quantifiable principles this study presents a methodological framework or protocol for numerically quantifying various ecogeomorphic attributes using a suite of mathematically defined landscape metrics to provide a rigorous and statistical evaluation of vegetated dune field evolution within this framework the model parameter space can be systematically explored and simulation outcomes can be methodically compared against real world landscapes based on a simplified scenario of parabolic dunes developing out of blow outs the resulting dune field realizations are investigated as a function of variable growth vigour of two simulated vegetation types pioneer grass and successional woody shrub by establishing a typological phase diagram of different landscape classes the set of simulation outcomes furthermore defines a higher dimensional phase space whose axes or dimensions can be interpreted by analysing how individual ecogeomorphic landscape metrics or state variables contribute to the data distribution principal component analysis can reduce this to a visual three dimensional 3d phase space where landscape evolution can be plotted as time trajectories and where we can investigate the effects of changing environmental conditions partway through a simulation scenario the use of landscape state variables and the construction of a 3d phase space presented here may provide a general template for quantifying many other eco geomorphic systems on the earth s surface

short communication multi scale topographic anisotropy patterns on a barrier island abstract barrier islands exhibit a range of landforms that reflect the complex and varied combination of coastal and aeolian processes realized over the evolution of the island a detailed analysis of the topography can be used to describe the evolution of a barrier island and provide insight on how it may be affected by a change in sea level storm activity and wind exposure patterns topographic anisotropy or the directional dependence of relief of landforms can be used to determine the relative importance of different processes to island evolution at a range of scales this short communication describes the use of scale dependent topographic anisotropy to characterize the structure of santa rosa island in northwest florida scale dependent topographic relief and asymmetry were assessed from a lidar derived dem from may 2004 a few months before the island experienced widespread erosion and overwash during hurricane ivan this application demonstrates how anisotropy can be used to identify unique scale dependent structures that can be used to interpret the evolution of this barrier island results of this preliminary study further highlight the potential of using topographic anisotropy to controls on barrier island response and recovery to storms as well as island resiliency with sea level rise and storm activity

stratigraphic evidence of desertification in the west central great plains within the past 1000 yr stratigraphic and geomorphic relations archeological data and eight radiocarbon ages at five widely scattered localities in northeastern colorado indicate that eolian sand was mobilized over broad areas within the past 1000 yr the mobilization began after 1 ka was episodic and ended at some as yet undetermined time prior to the latter part of the nineteenth century given that climate model simulations suggest only slight variation in average surface temperature and annual precipitation in this region during the past 1000 yr this part of the great plains evidently is near the threshold of widespread eolian sand transport under the present climate

deconstructing aeolian landscapes abstract semi stabilized dune systems are important indicators of quaternary drought variability across central north america the south texas sand sheet stss is the southernmost relict dune system on the great plains and is exposed to higher evapotranspiration and moisture variability than similar landscapes farther north in this study a combination of surface and sub surface remote sensing is used to analyze the semi stabilized dune landscapes of the stss in order to delineate distinct aeolian sediments that can represent generations of sedimentation or particular climate conditions the combination of multi resolution analysis of a lidar dataset electromagnetic conductivity surveys and xrf scans of soil cores are shown to be useful tools for deconstructing and modeling the environmental history of the stss optically stimulated luminescence osl dating of identified surfaces suggests that the stss is older than previously thought since dune systems are excellent repositories of climate and biophysical data for a landscape and are also sensitive to changes in climate and ecology the methodology employed in this study can be used to characterize the vulnerability of other similar environments to climate change through the holocene and over the next century

30 000 year old wild flax fibers a unique finding of wild flax fibers from a series of upper paleolithic layers at dzudzuana cave located in the foothills of the caucasus georgia indicates that prehistoric hunter gatherers were making cords for hafting stone tools weaving baskets or sewing garments radiocarbon dates demonstrate that the cave was inhabited intermittently during several periods dated to 32 to 26 thousand years before the present kyr b p 23 to 19 kyr b p and 13 to 11 kyr b p spun dyed and knotted flax fibers are common apparently climatic fluctuations recorded in the cave s deposits did not affect the growth of the plants because a certain level of humidity was sustained

interdependence of geomorphic and ecologic resilience properties in a geographic context abstract ecology and geomorphology recognize the dynamic aspects of resistance and resilience however formal resilience theory in ecology has tended to deemphasize the geomorphic habitat template conversely landscape sensitivity and state and transition models in geomorphology downweight mechanisms of biotic adaptation operative in fluctuating spatially explicit environments adding to the interdisciplinary challenge of understanding complex biogeomorphic systems is that environmental heterogeneity and overlapping gradients of disturbance complicate inference of the geographic patterns of resistance and resilience we develop a conceptual model for comparing the resilience properties among barrier dunes the model illustrates how adaptive cycles and panarchies the formal building blocks of resilience recognized in ecology can be expressed as a set of hierarchically nested geomorphic and ecological metrics the variance structure of these data is proposed as a means to delineate different kinds and levels of resilience specifically it is the dimensionality of these data and how geomorphic and ecological variables load on the first and succeeding axes that facilitates the delineation of resistance and resilience the construction of dune topographic state space from observations among different barrier islands is proposed as a way to measure the interdependence of geomorphic and ecological resilience properties

understanding linear dune chronologies insights from a simple accumulation model abstract dunefields are today often found in regions where environmental conditions are no longer conducive to widespread aeolian transport and deposition and are thus seen as potential archives of palaeoenvironmental information some dune types are more suitable for this purpose than others and linear dunes used here synonymously with longitudinal dunes have been most frequently employed they are commonly found in dryland and dryland marginal regions and they are apparently less migratory than some other dune forms thereby offering the potential for longer environmental histories most recent studies have employed optical osl dating surveys which directly date the emplacement of dune sands to attempt to produce a representative history of aeolian accumulation at a dunefield scale yet such studies have not always given due consideration to the geomorphology of linear dune accumulation although linear dunes do not rework their sand as readily as say barchans dunes it is clear that sand deposited during an aeolian event is likely to have been removed from elsewhere on the dunefield s surface for this reason all dune archives must be assumed to be discontinuous over long timescales the effect of sediment redistribution on dune preservation and thus palaeoenvironmental interpretation is difficult to observe and poorly understood we present a simplified probabilistic model to replicate deposition erosion of sand at a linear dune crest thus simulating the type of profile sampled in many field studies in order to produce a local accumulation history the modelled sand flux incorporates various feedbacks and the simulations are run with varying boundary conditions in which the simulated surface is assumed to be in equilibrium over the multi millennial timescales of the model s duration periodic instabilities in the landscape are generally well recorded by the modelled dune accumulation history particularly when the events involve the system as a whole briefly functioning out of an equilibrium state i e the probabilities of deposition and reworking are not equal however under forcing conditions where the probabilities are unchanged throughout the duration of the model run the results can show apparent structure within the data when sample sizes are low although at large sample sizes the preservation potential decays with burial age according to a power law the model confirms the importance of rigorous sampling strategies for such studies but also suggests that if such precautions are taken the reworking inherent to linear dune aeolian systems does not preclude their use as a quaternary palaeoenvironmental archive of environmental change

thermal curved fragments a method for identifying anthropogenic fire in the archaeological record abstract the archaeology of fire is a developing field one challenge centers on equifinality distinguishing the affects of wildfire versus anthropogenic fire especially where evidence for control of fire by humans in the early pleistocene remains debated there is little consensus regarding what constitutes clear evidence of human control another concern is preservation bias which reduces clearly identifiable archaeological signatures of fire in this paper we argue that a peculiar lithic angular fragment termed thermal curved fragment tcf exhibits statistically distinct quantitative evidence of the confluence of human knapped stone tools and exposure to a high energy long duration ground level fire i e campfires experimental tcfs are described and compared to unfired knapping debitage natural exfoliations and suspected archaeological tcfs the provenance of these archaeological specimens has previously been argued to infer hominin controlled fire at 1 5 1 6 ma at the koobi fora formation we also present data from experiments exposing stone flakes arranged as scatters of similar raw materials to those found in the koobi fora formation to usda prescribed burns in a variety of conditions approximating landscape fires results indicate that tcfs are formed specifically where previously knapped stone is exposed to high energy ground level fires similar to those seen in ethnographic campfires our analysis indicates that tcfs can be used in conjunction with other lines of evidence indicating the presence of anthropogenic fire in the archaeological record

imaging of offset vsp data with an elastic iterative migration scheme vsp data are usually acquired in order to obtain high resolution images of complex structures in reservoirs and near boreholes the authors present an elastic iterative migration scheme which has few limitations regarding the complexity of the geology and where the macromodel for both p and s wave velocities is automatically improved and updated at each iteration they avoid wavefield separation up down and p s and the simplifying assumptions of small dips underlying most such methods the migration scheme is based on elastic inversion theory the wavefield extrapolation is based on a high order coarse grid finite difference solution to the elastic two way wave equation at each iteration the macromodel is updated using a gradient method in which the gradient is computed by correlation of forward modelled fields with back propagated residual fields the first iteration of the migration scheme is equivalent to elastic reverse time migration with an imaging condition similar to claerbout s principle both p and s wave reflections contribute to the images in numerical examples with both synthetic and real offset vsp data they find that increasing the number of iterations improves the image quality images based on both p and s wave energy give more near well information and higher spatial resolution than images on only acoustic energy more in the real data example the authors show that the iterative migration scheme can image a relatively complex geological structure a fault and a small graben intersecting the well can be identified less

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

formation processes and stratigraphic integrity of the middle to upper palaeolithic sequence at cova gran de santa linya southeastern prepyrenees of lleida iberian peninsula sediments from cova gran de santa linya southeastern prepyrenees of lleida iberia are investigated by geoarchaeological means micromorphological textural quartz grain morphoscopy and geochemical analyses are coupled with stratigraphic and sedimentary macroscopic data to provide new insights into the formation processes and the integrity of the occupation layers and embedded sterile deposit documented at the middle to upper palaeolithic boundary direct indicators of the anthropogenic and natural dynamics involved in the deposition and alteration of the sediments investigated are provided results reveal the presence of in situ combustion structures as a major sedimentary indicator of human activity and occupation surfaces at the site the overall good preservation of the combustion residues indicates that occupation layers have been preserved in their original context of deposition traits of surface exposure in parallel to progressive lessening of evidence related to human activity at the top of the middle palaeolithic sequence suggest discontinuity in the occupation of the site and a possible abandonment of the rock shelter at the end of this period formation processes of the sterile deposit documented between the mousterian and the early upper palaeolithic levels involved the accumulation of debris from local sediments and soils as well as from the structure of the rock shelter soil forming dynamics related to palaeoenvironmental moisture fluctuations have also been recorded throughout the sequence investigated and indicate periods of surface stability during the formation of the sterile deposit environmental dynamics active during the formation of the sterile partially disturbed the top of the mousterian layer however our data indicate that such dynamics did not substantially affect the overall integrity of the archaeological record our results highlight the crucial contribution of geoarchaeology and microstratigraphy to the characterisation and assessment of the anthropogenic and natural dynamics involved in the accumulation and taphonomy of middle to upper palaeolithic sequences

large wind shift on the great plains during the medieval warm period spring summer winds from the south move moist air from the gulf of mexico to the great plains rainfall in the growing season sustains prairie grasses that keep large dunes in the nebraska sand hills immobile longitudinal dunes built during the medieval warm period 800 to 1000 years before the present record the last major period of sand mobility these dunes are oriented nw se and are composed of cross strata with bipolar dip directions the trend and structure of the dunes record a drought that was initiated and sustained by a historically unprecedented shift of spring summer atmospheric circulation over the plains moist southerly flow was replaced by dry southwesterly flow

kirchhoff modeling inversion for reflectivity and subsurface illumination because of its computational efficiency prestack kirchhoff depth migration is currently one of the most popular algorithms used in 2 d and 3 d subsurface depth imaging nevertheless kirchhoff algorithms in their typical implementation produce less than ideal results in complex terranes where multipathing from the surface to a given image point may occur and beneath fast carbonates salt or volcanics through which ray theoretical energy cannot penetrate to illuminate underlying slower velocity sediments to evaluate the likely effectiveness of a proposed seismic acquisition program we could perform a forward modeling study but this can be expensive we show how kirchhoff modeling can be defined as the mathematical transpose of kirchhoff migration the resulting kirchhoff modeling algorithm has the same low computational cost as kirchhoff migration and unlike expensive full acoustic or elastic wave equation methods only models the events that kirchhoff migration can image kirchhoff modeling is also

did stones speak about people flint catchment and neanderthal behavior from area 3 canaveral madrid spain abstract middle paleolithic catchment patterns have been exhaustively studied in the past however it is essential to clearly define neanderthal technical and strategic abilities in relation to raw materials self provide from a temporal perspective here we present a study of quarrying activities in open air sites occupied during mousterian period in madrid spain with different patterns of lithic catchment at the el canaveral archaeological complex several sites have been identified in relation with natural flint outcrops from these we have gained information about flint supplying patterns both in primary and secondary deposits in addition different operative chains and diverse systems of ramification and recycling were employed depending on the final objectives we were able to appreciate additional actions by analyzing the diacritic superposition of knapping series in blanks cores and supports of different qualities changes in categories dimensions and raw material qualities allow a first identification of lithic actions throughout time as a proxy of standardized or random human behavior when catchment actions took place

evidence of active dune sand on the great plains in the 19th century from accounts of early explorers eolian sand is extensive over the great plains of north america but is at present mostly stabilized by vegetation accounts published by early explorers however indicate that at least parts of dune fields in nebraska colorado kansas new mexico and texas were active in the 19th century based on an index of dune mobility and a regional tree ring record the probable causes for these periods of greater eolian activity are droughts accompanied by higher temperatures which greatly lowered the precipitation to evapotranspiration ratio and diminished the cover of stabilizing vegetation in addition observations by several explorers and previous historical studies indicate that rivers upwind of great plains dune fields had shallow braided sandy channels as well as intermittent flow in the 19th century wide braided sandy rivers that were frequently dry would have increased sand supplies to active dune fields we conclude that dune fields in the great plains are extremely sensitive to climate change and that the potential for reactivation of stabilized dunes in the future is high with or without greenhouse warming

least squares data to data migration an approach for migrating free surface related multiples free surface related multiples can provide extra illumination of the subsurface and thus can be usefully included in migration procedures however most multiple migration approaches require separation of primaries and free surface related multiples or at least prediction of multiples in advance which is time consuming and prone to errors the data to data migration ddm method migrates free surface related multiples by forward and backward propagating the recorded full data containing primaries and free surface related multiples for ddm there is no need to predict or separate multiples but the migration results suffer from the crosstalk generated by crosscorrelations of undesired seismic events e g primaries and second order free surfacerelated multiples we have developed least squares ddm lsddm for marine data to eliminate the crosstalk generated by ddm in each iteration the forward propagated primaries and free surface related multiples are crosscorrelated with the backward propagated primary and free surface related multiple residuals to form the reflectivity gradient we use a three layer model and the marmousi model for numerical tests the results validate that lsddm can provide a migrated image with higher signal to noise ratio and more balanced amplitudes than ddm the lsddm approach might be valuable for general subsurface imaging for marine seismic data when the migration velocity is accurate and the acquired data have sufficient recording time

least squares migration of incomplete reflection data a least squares migration algorithm is presented that reduces the migration artifacts i e recording footprint noise arising from incomplete data instead of migrating data with the adjoint of the forward modeling operator the normal equations are inverted by using a preconditioned linear conjugate gradient scheme that employs regularization the modeling operator is constructed from an asymptotic acoustic integral equation and its adjoint is the kirchhoff migration operator we tested the performance of the least squares migration on synthetic and field data in the cases of limited recording aperture coarse sampling and acquisition gaps in the data numerical results show that the least squares migrated sections are typically more focused than are the corresponding kirchhoff migrated sections and their reflectivity frequency distributions are closer to those of the true model frequency distribution regularization helps attenuate migration artifacts and provides a sharper better frequency distribution of estimated reflectivity the least squares migrated sections can be used to predict the missing data traces and interpolate and extrapolate them according to the governing modeling equations several field data examples are presented a ground penetrating radar data example demonstrates the suppression of the recording footprint noise due to a limited aperture a large gap and an undersampled receiver line in addition better fault resolution was achieved after applying least squares migration to a poststack marine data set and a reverse vertical seismic profiling example shows that the recording footprint noise due to a coarse receiver interval can be suppressed by least squares migration

late holocene dune activity linked to hydrological drought nebraska sand hills usa dunee elds of the great plains contain stratigraphic records of episodic holocene aeolian activity potentially providing a valuable record of climatic change it has been dife cult to establish unambiguous links between activity at specie c sites and regional palaeoclimate however here we demonstrate that widespread late holocene aeolian activity in the nebraska sand hills the largest dunee eld on the great plains of north america occurred during a period of hydrological drought aeolian sand sheets are interbedded with peat that accumulated in interdunes throughout much of the holocene the youngest of these sand sheets was deposited between 950 and 650 cal bp about the same time as the most recent major episode of aeolian activity at upland sites up to 120 km apart sand sheets could only have advanced across the interdunes if the local groundwater e ow systems that maintain interdune wetlands were temporarily reduced or eliminated by a reduction in recharge both reduced recharge and upland aeolian activity are best explained by regional megadrought

efficient amplitude encoding least squares reverse time migration using cosine basis least squares reverse time migration provides better imaging result than conventional reverse time migration by reducing the migration artefacts improving the resolution of the image and balancing the amplitudes of the reflectors however it is computationally intensive to reduce its computational cost we propose an efficient amplitude encoding least squares reverse time migration scheme in the time domain although the encoding scheme is effective in increasing the computational efficiency it also introduces the well known crosstalk noise in the gradient that degrades the quality of the imaging result we analyse the cause of the crosstalk noise using an encoding correlation matrix and then develop two numerical schemes to suppress the crosstalk noise during the inversion process we test the proposed method with synthetic and field data numerical examples show that the proposed scheme can provide better imaging result than reverse time migration and it also generates images comparable with those from common shot least squares reverse time migration but with less computational cost

short term changes in the morphodynamic states of beaches and surf zones an empirical predictive model a time series of 6 5 years of daily observations of beach states and wave characteristics from southeastern australia was analyzed with the aim of determining the degree to which time varying beach state can be explained and predicted the six commonly occurring beach states dissipative longshore bar trough rhythmic bar and beach transverse bar and rip low tide terrace and reflective discussed earlier were related by means of discrete discriminant analyses to the parameter hb wst where hb is breaker height ws is the fall velocity of the beach sand and t is peak breaker period using a total of 1545 cases two values were used in the analyses the immediate value occurring on the day the particular state was observed and a weighted mean value expressing recently antecedent conditions the immediate value made a negligible contribution to explaining day to day beach state observations however the antecedent conditions showed a strong relationship and provide a successful means of prediction by examining cases where the time derivatives of both state and were near zero it was possible to define the equilibrium conditions associated with each state directions of change erosional or accretionary are predicted in terms of departures of from the equilibrium value appropriate to the beach state prevailing at the time change begins