seismic images of continental lithosphere seismic reflection profiles in usa and west germany over thirty years ago showed strong reflections from the lower crust but technical advances through the 1970s were needed for the method to image the continental lithosphere the british institutions reflection profiling syndicate birps found advantage in working offshore and has obtained over 12 000 km of profiles around britain during the past decade giving the densest regional coverage anywhere reflections are observed from strata in sedimentary basins from low angle faults that can be followed from surface to mid crust from a laterally variable reflective zone in the lower crust from the moho and from fault like features in the upper mantle there is evidence around britain that faults bounding sedimentary basins are older structures which have been reactivated it is argued that lower crustal reflectivity around britain is mainly due to anastomosing ductile shears which accommodate extension in the lower crust commensurate with extension in the upper crust by faulting and block rotation there is also evidence of reflections preserved from older orogenic features so that reflections interpreted as extensional ductile shears in the lower crust may also derive from older features that have been reactivated most reflections in the lower crust arise from rocks that have been highly strained evidence of lateral variability in the reflective character of the moho suggests that the moho has been actively involved in the structural evolution of the lithosphere upper mantle reflections are interpreted as shear zones which transfer crustal deformation through the lithosphere

geomorphology stratigraphy and facies analysis of some late pleistocene and holocene key deposits along the coast of sardinia italy and geochronology for some key sites along the coast of sardinia italy a note from the editor in chief

heterogeneity spectrum and scale anisotropy in the upper crust revealed by the german continental deep drilling ktb holes crustal heterogeneities and their statistical characteristics bear important information about the dynamic processes and evolution of the crust the velocity well log data from the german continental deep drilling project ktb offer a rare opportunity to measure directly the properties of crustal heterogeneities in this study we first estimated the power spectrum of crustal heterogeneities from the p velocity well logs of the two holes for the first time a power law spectrum of crustal heterogeneities was directly observed in the spatial wavelength range from a few meters to a few kilometers the slope of the vertical 1d power spectrum of the random velocity perturbations is about 1 1 corresponding to a flicker noise random medium the scale anisotropy ratio aspect ratio and the horizontal spectral slope of crustal heterogeneities were also estimated by cross correlation analysis between these two holes to be about 1 8 and 2 0 respectively

the heterogeneous mantle rocks are composed of heterogeneous mixtures of minerals and assemblages of larger units and there is no reason to assume that the earth at large and intermediate scale should be homogeneous however the resolution of geophysical studies of the earth s mantle is limited there is a gap in resolution between studies of rock samples brought to the surface of the earth and seismological results which mainly show large scale structures there is also a gap between global tomographic models and the results of high resolution body wave and scattering techniques it is often assumed that the mantle is homogeneous at intermediate scales the standard model of geochemistry for example assumes that the upper mantle is homogenous

mis 5e at san giovanni di sinis sardinia italy stratigraphy u th dating and eustatic inferences the most representative late pleistocene tyrrhenian outcrop in sardinia san giovanni di sinis was re visited based on detailed sedimentological and stratigraphical analysis supported by u series dating of fossil corals the stratigraphy shows shorefaceebackshore sandstones overlying an erosional surface cut on vertebrate bearing layers facies analysis and sequence stratigraphic approaches suggest eustatic changes during the overall depositional interval of the marine sequence disconformities distinguish two coastal units suggesting a lateral shifts of the depositional environments driven by millennial scale frequency sea level fluctuations never exceeding a maximum height 1t o 3 m and by a subsequent rise to 5 o 5 5 m asl these deposits have historically been assigned to mis 5 on the basis of i their palaeontological content warm senegalese fauna ii lithostratigraphic interpretations and iii amino acid geochronological data and generally attributed to the high sea level episode of mis 5e sub stage through sequential interpretation u series measurements in colonies of cladocora caespitosa from the main outcrop of san giovanni di sinis and other minor deposits from the eastern side of the isthmus and from

structure and seismic response of extended continental crust stochastic analysis of the strona ceneri and ivrea zones italy a two dimensional stochastic seismic model of the crustal cross section exposed in the strona ceneri and ivrea zones northern italy was derived from geologic maps and petrophysical data with techniques used in microfabric analysis the model has a layered self affine structure which agrees with the intrinsic scale independence of geologic phenomena synthetic seismograms from this model replicate many pertinent features observed in deep seismic reflection data and allow insight into crustal structure 1 reflectivity depends on the lithological populations present and their distribution within a crustal unit 2 transparent zones within the reflective lower crust can arise from metamorphic reactions 3 the transition from upper to lower crust may be a change in small scale seismic fabric rather than a first order seismic discontinuity

compositional and metamorphic controls on velocity and reflectivity in the continental crust an example from the grenville province of eastern quebec we present velocity and density data for a suite of gabbros and metagabbros over a range of metamorphic grades from subgreenschist to the eclogite facies most of these rocks have a mesocratic protolith with overlapping bulk chemistry ranges providing an opportunity to investigate the systematics of mineralogy and physical properties across a wide range of metamorphic grades with minimal compositional variation in addition more mafic gabbros in the eclogite facies were also investigated in order to take into account variations in the extent of transformation of gabbro to eclogite controlled by bulk chemistry the physical properties data are used as the basis for a first order crustal model composed of granitic anorthositic and gabbroic components the objective of constructing the crustal model is to evaluate the relative contribution of compositional variation and metamorphism to the velocity density and reflectivity structure of the continental crust the model suggests that in the upper crust if fracture porosity is neglected composition dominates the velocity and density structure while in the middle and lower crust composition and metamorphism play equally important roles simulations designed to predict potential reflection coefficient size distributions for the various bulk chemistries and mineralogies in the crustal model indicate step increases in the potential for large reflection coefficients that are dominantly controlled by metamorphic grade step increases in reflectivity are predicted between the lower and upper amphibolite facies and between incompletely and completely eclogitized metagabbros in the eclogite facies we also consider several alternative mixing models which account for the effects of one of the three lithologic components occurring as isolated bodies rather than perfectly mixed with the other two components these models indicate a reduction of the potential for large reflection coefficients by as much as 50 emphasizing the importance of the degree of mixing for crustal reflectivity

synthetic seismograms for a complex crustal model the algorithm of the original reflectivity method has been vectorized and implemented on a cdc cyber 205 computer calculation times are shortened by a factor of 20 to 30 compared with a general purpose computer with a capacity of several million floating point operations per second mflop the rapid calculation of synthetic seismograms for complex models high frequency sources and all offset ranges is a provision for modeling not only particular phases but the whole observed wavefield as an example we model refraction data of the black forest southwest germany and are able to derive rather tight constraints on the physical properties of the lower crust

underestimation of scale lengths in stochastic fields and their seismic response a quantification exercise summary the possibility that parts of the earth s continental lower crust can be described with stochastic geological models has been suggested for some time recent studies of deeper well logs also indicate a possible stochastic structure at mid crustal levels this motivates a closer examination of the relation between the statistics of reflection wavefields and that of the lower crust such a relation can put important constraints on possible lower crustal models this study follows up earlier efforts to quantify the statistics of both stochastic lower crustal models and the reflected wavefield since modelling of the seismic response of stochastic von karman fields implies the usage of the impedance contrast field of the latter we wish to compare the second order statistics of both types of fields velocity and impedance this study concludes that the vertical derivative operator on a von karman velocity field implicitly present in the impedance contrast field alters the second order horizontal von karman statistics of the velocity fields in a profound way wavefield effects undoubtedly present in observed seismic data which have earlier been proposed as possible causes for the aforementioned change seem to play a secondary role the vertical derivative operation inherent in the impedance contrast field reduces the estimated horizontal scale length and hurst number by a factor of 2 22 and 1 3 respectively original vertical scale length and hurst number of the velocity fields have a quasi linear influence on this underestimation horizontal scale lengths and hurst numbers were also estimated from the seismic response primary reflectivity section of the von karman fields the values obtained are close to those obtained from the causative impedance contrast fields and are similarly underestimated this suggests a dominant role for the vertical derivative operator in the underestimation of horizontal scale length and hurst number this attempt to quantify the relation between the horizontal spatial statistics of von karman fields and the estimates derived from their seismic response may be useful in upscaling the latter

mapping correlation lengths of lower crustal heterogeneities together with their maximum likelihood uncertainties abstract a novel statistical technique has been applied to the ag 48 seismic line from the lithoprobe dataset passing through the abitibi grenville province canada the method maps lateral stochastic parameters representing von karman heterogeneity distributions in the crust estimated from migrated deep reflection data together with these parameters viz lateral correlation length and power law exponent we also compute their associated maximum likelihood uncertainties combining normalised measurements of lateral correlation and their uncertainties objective profiles of crustal fabric can be made these profiles indicate significant spatial variations in macro scale petrofabric correlation length which carries useful information about structural scale lengths of heterogeneous bodies is an especially robust parameter with moderate associated uncertainties although the general outline of the profiles conforms to the earlier tectonic interpretations based on line drawings new features are visible too the macro scale petrofabric is seen to vary significantly within the tectonic terrains identified earlier in depth as well as laterally a consequence of this additional delineation is that we can explain an existing part of the ag 48 line equally well in terms of collisional deformation and in terms of the effects of a major shear zone projected onto a parallel segment of the line

determining the reduction sequence of hawaiian quadrangular adzes using 3d approaches a case study from moloka i hawaiian adze manufacture requires a great deal of skill and undoubtedly required long apprenticeships to achieve the finesse seen in many finished prehistoric adzes despite the presence of more than two dozen adze quarries in hawai i and previous attempts at replicating adze preforms and positing reduction sequences in polynesia there is no detailed study that clearly defines the steps and stages of quadrangular adze preform manufacture the most common form in hawai i and the resulting characteristic debitage in this paper we examine the sequence of adze production for a population of 109 adzes from moloka i documenting the transition from blanks to preforms to the finished objects that were transported away from quarries reduction intensity is measured using the scar density index clarkson 2013 calculated from 3d scans we document the sequence of cumulative additions of characteristic features to adzes e g bidirectional edges bevel poll and tang as reduction intensity increases we also note the reasons for adze rejection at each stage of reduction our study provides the first detailed analysis of adze reduction in polynesia facilitated and standardised by 3d scanning technology hopefully it will serve as a useful benchmark for objectively and systematically comparing adze technology in other parts of hawai i and across polynesia leading to a better understanding of regional and temporal variation in adze technology

deep seismic reflection profiling and the growth of the continental crust abstract deep seismic reflection profiling provides evidence for the style and magnitude of phanerozoic crustal growth by both lateral and vertical accretion profiles across convergent zones have been interpreted as showing tectonic underplating of the continental crust by fragmented oceanic lithosphere profiling across extensional zones provides evidence for magmatic underplating of the crust in addition to studies over active areas deep reflection profiling over large areas of western europe north america and australia shows that the lower crust is strongly reflective and seismically distinct from the upper crust and upper mantle the layering is detected beneath many different terranes of varying crustal type and basement age from archaean to cenozoic and is often apparently younger than the tectonic or metamorphic age of the exposed upper crust thus continental growth curves estimated from upper crustal measurements alone may underestimate phanerozoic crustal additions and mean crustal ages similarly estimated may be too high

wide angle seismic reflections from two dimensional random target zones we have analyzed the shot gather seismic response of a buried zone of isotropic random velocity fluctuations scattering analysis predicts that events at offsets greater than the depth of the target zone will appear more continuous and coherent than events at zero and small offsets due to an effective dip filter inherent to the source target receiver geometry the scattering theory is confirmed with finite difference synthetic seismograms calculated for an idealized crustal model the closely spaced synthetic seismograms show bright events having the appearance of refraction arrivals which suggest a horizontally layered structure in the target zone these effects appear to be independent of the magnitude of the velocity fluctuations provided that the magnitude of the fluctuations is small 3 0 of the mean velocity we have made a second finite difference calculation of a crustal scale model to reinterpret previously published wide angle data from the black forest germany sandmeier and wenzel 1986 the response of the lower crust seen in the conventionally recorded field data can be explained by a lower crustal model of isotropic small amplitude random velocity fluctuations we present this in contrast to a laterally homogeneous model of a finely layered lower crust of alternating high and low velocities proposed by sandmeier and wenzel 1986 the synthetic studies and the scattering analysis demonstrate that the geometry of the wide angle experiment produces signals which appear to be from layered target zones even where no layering exists they also underscore the importance of conducting seismic surveys which make use of closely spaced receivers and which integrate vertical incidence and wide angle recording

small scale heterogeneity and large scale velocity structure of the continental crust since conrad 1925 first identified a midcrustal refraction event in central europe seismologists have developed layered models of the continental crust with velocity steps at various levels modern analysis of crustal refraction data including automated inversion relies on ray theoretical techniques or wave theory for plane layered media which generally parameterize the earth as a series of grossly horizontal layers the bias toward layered models is in part based on physical and geologic intuition but it is to a large measure a result of available interpretation methods for example layer based reflectivity and ray tracing methods in contrast reflection seismology has produced a picture of a highly heterogeneous crust with wavelength scale variations in velocity existing at different levels of the crust in different tectonic regimes finite difference modeling shows that zones of small amplitude random velocity fluctuations not only produce short discontinuous reflection segments as observed on deep seismic reflection data but also produce strong wide angle reflections some of the events identified as crustal wide angle reflections in field data may in fact be the result of scattering from wavelength scale heterogeneities and need not result from reflection from a first or second order velocity discontinuity significant changes in the large scale velocity structure associated with zones of random velocity fluctuations produce relatively small changes in the dynamic properties of the backscattered wave field this observation is in disagreement with the common credo that the seismic refraction method is primarily sensitive to changes in the large scale velocity structure as a consequence the ray theoretical interpretation of such wide angle reflections as first order discontinuities leads to crustal velocity structures that are nonunique and may be erroneous in detail while correctly predicting average crustal velocity and thickness we are not suggesting that crustal velocity does not change with depth on the large scale rather we are proposing that crustal seismic events observed at intermediate and large offsets may be the result of scattering from wavelength scale velocity fabric rather than specular reflection or refraction from first order discontinuities

the effect of hammer mass and velocity on flake mass abstract this paper presents the results of controlled fracture experiments designed to investigate the effects on flake mass of varying the mass and velocity of the hammer it was found that the contribution of these two independent variables are almost negligible for a given combination of exterior platform angle and platform thickness though they must be sufficient to initiate production of a flake of a given potential mass

seismic properties of rocks from an exposure of extended continental crust new laboratory measurements from the ivrea zone abstract compressional wave velocities for new samples from the ivrea verbano zone ivz and strona ceneri zone scz have been measured to 600 mpa in order to better understand the petrologic controls on velocity and to provide an expanded base for seismological models of the crust as represented by these terrains these data coupled with previous measurements show that preferred orientation of mica controls both the velocity hysteresis with pressure and seismic anisotropy of scz and ivz schists and gneisses ivz paragneisses form the basis of a linear velocity density relationship for metagraywackes of various metamorphic grade this relationship falls close to that expected for mafic rocks and overlaps velocity density data for ivz mafic gneisses one dimensional near vertical reflection models based on these data and recent structural reconstructions of the terrain show that lower crustal reflectivity can be related to high reflection coefficients associated with interlayered sequences of upper amphibolite granulite facies paragneiss mafic gneiss and ultramafic rocks transparent upper crustal levels in the model result from the overall similarity of velocities for schists gneisses and granites from the structurally and lithologically complex scz a mean lower crustal velocity of 7 1 km s is calculated for the part of the ivz composed of interlayered mafic gneiss and paragneiss and for another area dominated by a mafic layered igneous complex the velocity density analysis coupled with this observation emphasize the ambiguity inherent in interpretation of crustal composition from p wave velocity data in the absence of other constraints

stochastic characterization and seismic response of upper and middle crustal rocks based on the lewisian gneiss complex scotland summary we have developed statistical models of upper and middle crustal seismic velocity heterogeneity based on geologic maps and petrophysical data from the lewisian gneiss complex scotland the level of heterogeneity we have measured is relevant to seismic exploration of the crystalline crust using conventional reflection and refraction techniques we digitized two 1 10560 geologic maps of laxfordian archean age lewisian rocks on a 26 8m grid both maps are believed to be representative of the upper and middle crust in north western scotland and both are believed to provide cross sectional views of parts of the crust the digital maps were characterized by the statistics of their lithologic populations and by their 2 d spatial autocorrelation functions different lithologies were assigned seismic velocities appropriate for the mid crust using petrophysical data three lithologies are dominant silicic gneisses vp 6 2 km s 1 mafic amphibolites vp 6 75 kms 1 and intermediate composition schists vp 6 5kms 1 both maps have self affine spatial fabrics the first map covers the core of a syncline its autocorrelation function defines a medium with a fractal dimension of 2 78 a horizontal characteristic length of about 244m and a vertical correlation of about 133m aspect ratio is 2 1 it has an essentially trimodal velocity lithology population consisting of 37 per cent silicicgneiss 43 per cent mafic amphibolites and 20 per cent schists this map is representative of 30 40 per cent of laxfordian rocks the second map is a plan view which can be rotated 90 about an axis perpendicular to strike to give a cross section this map is characterized by a fractal dimension of 2 55 with a horizontal correlation length of about 111m and a vertical correlation of about 38m aspect ratio 3 1 it has a nearly bimodal population consisting of 77 per cent silicic gneisses and 22 per cent mafic amphibotites it is representative of 60 70 per cent of laxfordian rocks lastly we examine the seismic response of an upper to middle crust based on our statistical models using acoustic and elastic 2 d finite difference synthetic seismograms short offset shot records demonstrate that a lewisian upper crust produces scattered waves which significantly disrupt signals reflecting from deeper levels measurements of transmission scattering q and coda decay rates confirm that seismic scattering in lewisian type crust is strong the migrated cmp response of a lewisian crustal model shows the characteristic salt and pepper pattern often observed in the upper crust and described incorrectly as transparent we suggest that translucent is a more appropriate descriptor

finite difference simulations of seismic scattering implications for the propagation of short period seismic waves in the crust and models of crustal heterogeneity synthetic seismograms produced by the finite difference method are used to study the scattering of elastic and acoustic waves in two dimensional media with random spatial variations in seismic velocity the results of this study provide important insights about the propagation of short period 5 the self similar medium is characterized by a scattering q that is constant with frequency whereas theory predicts that the apparent q in an exponential medium is proportional to frequency these alternative models of crustal heterogeneity can thus be tested by improved measurements of the frequency dependence of crustal q at frequencies greater than about 1 hz assuming that scattering is responsible for most of the attenuation at these frequencies measurements of the time decay of the synthetic coda waves clearly show that the single scattering model of coda decay is not appropriate in the presence of moderate amounts of scattering attenuation scattering q 200 in these cases q values derived from the coda decay rate using the single scattering theory do not correspond to the transmission q of the medium the cross correlation of synthetic waveforms observed for an array of receivers along the free surface is observed to be dependent on the correlation distance of the medium the self similar random medium proposed here for the crust produces waveform variations at high frequencies 15 30 hz similar to those reported for actual small scale seismic arrays with apertures of hundreds of meters

geochronology for some key sites along the coast of sardinia italy recent stratigraphic surveys and facies analyses have questioned long held interpretations of the development and furthermore the age of quaternary sediments along the coast of sardinia the matter of debate is whether the investigated sediments were deposited during the late wurmian and holocene or during marine isotope stage mis 5 and older stages optically stimulated luminescence standard blue optically stimulated luminescence osl post infrared ir pulsed blue osl and post ir infrared stimulated luminescence irsl dating was applied to shallow marine and aeolian deposits as well as radiocarbon dating to bulk organic material in palaeosols radiocarbon dates suggest sedimentation during the late wurmian and holocene whilst the luminescence results for both quartz and potassium feldspar indicate a depositional age for most of the investigated sites prior to and during mis 5 from a geochronological point of view the luminescence ages are considered reliable because they passed all quality tests furthermore there is good agreement of two dosimeters with different bleaching and luminescence properties the radiocarbon ages might suffer from underestimation due to some contamination with young carbon which however cannot be large enough to yield such young ages

nature and origin of upper crustal seismic velocity fluctuations and associated scaling properties combined stochastic analyses of ktb velocity and lithology logs the main borehole of the german continental deep drilling program ktb extends over 9000 m into a crystalline upper crust consisting primarily of interlayered gneiss and metabasite we present a joint analysis of the velocity and lithology logs in an effort to extract the lithology component of the velocity log covariance analysis of lithology log approximated as a binary series indicates that it may originate from the superposition of two brownian stochastic processes fractal dimension 1 5 with characteristic scales of 2800 m and 150 m respectively covariance analysis of the velocity fluctuations provides evidence for the superposition of four stochastic process with distinct characteristic scales the largest two scales are identical to those derived from the lithology confirming that these scales of velocity heterogeneity are caused by lithology variations the third characteristic scale 20 m also a brownian process is probably related to fracturing based on correlation with the resistivity log the superposition of these three brownian processes closely mimics the commonly observed 1 k decay fractal dimension 2 0 of the velocity power spectrum the smallest scale process characteristic scale 1 7 m requires a low fractal dimension 1 0 and accounts for 60 of the total rms velocity variation a comparison of successive logs from 6900 7140 m depth indicates that such variations are not repeatable and thus probably do not represent true velocity variations in the crust the results of this study resolve disparity between the differing published estimates of seismic heterogeneity based on the ktb sonic logs and bridge the gap between estimates of crustal heterogeneity from geologic maps and borehole logs

gravity interpretation of a unified 2 d acoustic image of the central alpine collision zone summary four individual deep seismic reflection profiles across the eastern and southern swiss alps have been combined along the trend of the bouguer gravity anomalies onto the european geotraverse the profiles were migrated ray theoretically with the migration velocity model derived from a smoothed reinterpretation of the seismic wide angle profiles running parallel to the strike of the alpine arc the contours of this velocity model were ray theoretically depth migrated together with the combined digitized line drawings of the seismic reflection profiles the resulting acoustic image depicts the subduction of parts of the lower crust of the european plate beneath the adriatic promontory of the african plate at a low angle of 15 based on the interpretation of the seismic data orogenic crustal thickening is attributed to the stacking of crystalline nappes onto the upper crust of the european plate and wedging of the european and adriatic middle and lower crusts the latter being ill constrained by the seismic evidence alone the south vergent thrusting of the southern alps can be accounted for by the observed downbending of the adriatic moho and the lower crust in conjunction with the inferred wedging at mid crustal levels using the geometric constraints provided by seismic data gravity modelling of the alpine lithosphere asthenosphere system relative to stable central european platform clearly favours a gently inclined subduction zone reaching down to at least 200 km depth such a gently dipping subduction zone is at odds with prominent models on alpine geodynamics which favour a near vertical orientation of the subducting lithosphere verschluckung in agreement with the wedging hypothesis indirectly inferred from the seismic data the short wavelength part of the alpine gravity anomaly requires a middle crust of anomalously high density in the axial zone of the orogen both seismic and gravimetric evidence therefore suggest that late orogenic lithospheric shortening and crustal thickening was governed by the mechanical decoupling of the upper middle and lower parts of the crust the amount of subducted lower crustal material cannot be constrained by gravity modelling since its gravity effect cannot be separated from the effect of the subducting slab

seismic structure of gneissic granitic upper crust geological and petrophysical evidence from the strona ceneri zone northern italy and implications for crustal seismic exploration summary we present a stochastic seismic model of gneissic granitic upper crust by estimating the amplitude probability distribution and the autocorrelation function of the inferred seismic velocity field of the strona ceneri zone northern italy unlike previous investigations of the adjacent ivrea zone and the lewisian gneiss complex scotland the lithologies mapped in the strona ceneri zone cannot be directly correlated with laboratory measured seismic velocities the amplitude probability distribution of the extensive petrophysical database and the relatively uniform mineralogical composition of the lithologies indicate that the velocity distribution in the strona ceneri zone can be approximated as being continuous and gaussian based on this assumption and using the spatial autocorrelation function measured from a digitized geological cross section we have modelled the fine scale structure of the strona ceneri zone as a self affine medium with a fractal dimension of 2 50 0 15 and horizontal and vertical characteristic scales of 2 6 0 4 km and 1 4 0 3 km respectively on near offset shot gather seismic data strona ceneri type upper crustal heterogeneity produces a reflected field with the appearance of incoherent scattered noise characteristic of non reflective transparent upper crust found in extended phanerozoic provinces this type of heterogeneity has a considerable effect on seismic imaging of underlying reflective lower crust individual reflection segments are disrupted and shifted in time by up to several tenths of a second and the boundaries of the reflective zone become distorted and blurred at far offsets seismic scattering from heterogeneity of this type reproduces the commonly observed rapid decay and scattered distribution of pg amplitudes comparable amplitude decay patterns result from layered deterministic upper crustal velocity structures with velocity inversions

migration of synthetic seismograms for crustal structures with random heterogeneities summary fast frequency wavenumber migration is used to migrate synthetic seismograms calculated by a hybrid method for crustal models with complex 2 d scattering structures in the lower crust scatterers with predominantly horizontal or vertical orientation and scatterers without preferred orientation isotropic scatterers are investigated horizontal scatterers or lamellae have frequently been suggested for the lower crust on the basis of modern reflection seismological experiments in none of the cases studied here are the scattering structures imaged correctly the reason is mainly multiple scattering which can produce coherent arrivals in the seismogram sections and hence coherent signatures in the migrated sections which have no relation to structure imaging is generally acceptable for horizontal scatterers but for isotropic or vertical scatterers the migrated signatures are also horizontal and thus do not represent reality it is concluded that the highly detailed line drawings which are popular in crustal reflection seismology are less reliable than believed as far as the internal structure of scattering zones and the scatterer orientations are concerned horizontal or subhorizontal structures in the lower crust may be less common than assumed the paper also briefly addresses a few methodical aspects of fast frequency wavenumber migration for depth dependent background structure in particular the concept of sounding beams their width and the construction of a migrated section from several sounding beams

evaluating morphological variability in lithic assemblages using 3d models of stone artifacts abstract technological and morphological variability in lithic artifacts is commonly used to identify taxonomic entities in paleolithic research contexts assemblages are mainly studied using either linear distance measurements or qualitative assessments of morphologies here we present a method to quantify morphological variability in lithic artifacts using 3d models of stone artifacts our study on the sequence of the upper paleolithic layers v i from the site yabroud ii in western syria demonstrates that utilizing 3d models provides a new insight into the variability of lithic technologies we use quantitative data on convexities twist and scar patterns on cores and blades attributes previously not readily quantifiable to trace technological change through the archaeological sequence we are able to identify differences and translate these findings into a grouping of the layers while layers vi ii are characterized by technological continuity and were grouped together layers v and i can be separated from this group and represent technologically different groups chronologically before and after our results demonstrate the potential of 3d models for studying morphological variability in lithic assemblages

topo europe studying continental topography and deep earth surface processes in 4d abstract topo europe is a multidisciplinary international research program that addresses the interaction of processes inherent to the deep earth lithosphere mantle with surface processes erosion climate sea level which together shaped the topography of europe the objective of this programme is to assess neotectonic deformation rates and to quantify related geo risks such as earthquakes flooding landslides rock falls and volcanism research incorporating data interactive modeling focuses on the lithosphere memory and neotectonics with special attention on the thermo mechanical structure of the lithosphere mechanisms controlling large scale plate boundary and intraplate deformations anomalous subsidence and uplift and links with surface processes and topography evolution the topo europe natural laboratories in which these processes are analyzed cover a wide range of geodynamic settings these include the post collisional alpine carpathian pannonian basin system the very active aegean anatolian and apennines tyrrhenian orogens and back arc basins the caucasus levant area in the arabia europe collision zone the iberian peninsula caught up between alpine orogens the meta stable west and central european platform the stable east european platform and the seismically active and elevated scandinavian continental margin the topo europe project is a component of the international lithosphere program a european science foundation eurocores project provides funding for part of the research for a total amount of 13 5 m euro creating new research positions for 60 young researchers

accretionary history and crustal evolution of the variscan belt in western europe abstract the variscan belt of western europe is part of a large intra paleozoic belt extending on both sides of the atlantic from the ouachitas in the us and the mauritanides in west africa to the bohemian massif in czechoslovakia and poland the belt was constructed between 500 and 250 ma as a result of convergence and collision between two main continents laurentia baltica and africa after the closure of various oceanic basins iapetus rheic and galicia massif central now recorded as discrete in part cryptic sutures which form the roots of large crystalline nappes in which are found dismembered remnants of oceanic crust and mantle the accretionary history of the variscan belt in western europe is related to the progressive closure of probably two oceanic basins the rheic in the north and another the galicia massif central in the south by respectively southward and northward intraoceanic subduction followed by obduction and intracontinental lithospheric subduction the result is a broad 700 800 km fan like divergent belt which must be considered as a classical obduction collision orogen with a long intracontinental history of about 100 150 ma its arcuate shape is probably due to the northwestward impingement of a promontory of the african continent into laurentia baltica

fractals chaos self organized criticality and tectonics some geological structures have simple geometrical forms and can be analysed using deterministic equations examples include alluvial fans and many sedimentary basins but most geological structures are complex and appear to defy mathematical analyses yet in the complexity there is an order complex geological structures generally obey fractal statistics examples include topography distributions of earthquakes and faults and mineral deposits an unresolved question is whether the fractal order is simply the result of scale invariance or the result of governing equations that yield deterministic chaos in order to try to answer this question a variety of slider block models have been considered the stick slip behaviour of slider block models is a simple analogy to earthquakes a pair of slider blocks has been shown to behave chaotically models that use many slider blocks exhibit self organized criticality and generate fractal statistics similar to the statistics of regional seismicity

a reappraisal of the dwarfed mammoth mammuthus lamarmorai major 1883 from gonnesa south western sardinia italy the gonnesa quaternary deposits have been cited since the end of the 19th century due to the discovery during the construction of a railway of an incomplete postcranial skeleton belonging to an endemic dwarfed elephant afterward described by major as a new species elephas lamarmorae major 1883 although the remains have since been reported in the literature as coming from the aeolian deposits outcropping at funtana morimenta the precise provenance of the findings and their chronostratigraphical setting remained uncertain taking into account the route of the now disused railway the stratigraphical successions of the morimenta area and the fact that the elephant bones were actually collected during a number of excavations spanning several decades the location of the fossiliferous site is most likely on the northeast end slope of guardia pisano hill gonnesa where aeolianites correlate with the funtana morimenta formation fmf outcrop the fmf is supposed to predate the onset of the mis 5e climatic event and the tyrrhenian panchina overlies equivalent deposits cropping out along the gonnesa gulf coast therefore the hypothesis that the elephant remains found in the morimenta area were retrieved from late middle pleistocene deposits cannot be ruled out the anatomical features of the bones suggest they represent a single individual perhaps partially exposed and damaged before the discovery new evidence including a thus far unpublished tusk fragment from the guardia pisano hill gonnesa whose schreger angles fall within the range of mammuthus supports the systematic attribution of the incomplete morimenta skeleton to a dwarfed mammoth the size reduction of this sardinian dwarfed mammoth is discussed in light of body mass changes undergone by insular endemic elephants

synoptic interpretation of seismic reflection and refraction data summary the structure of the upper lithosphere beneath southern germany northern switzerland and west central utah u s a has been investigated in detail by various geophysical methods a synoptic interpretation of travel time and amplitude data obtained in seismic refraction and wide angle reflection surveys combined with near normal incidence reflection observations now permits the elucidation of the fine structure in a more quantitative and unified manner with this scheme it is possible to unambiguously identify low velocity zones and to deduce velocity gradients if reliable amplitude information is included in the inversion process

new experimental evidence on the relation between percussion flaking and flake variation abstract controlled experiments in percussion flaking allowed for objective analysis of relationships between variables of flake production and those variables which are attributes of the final result the independent variables those controlled by the flintknapper in the production of stone tools include force and angle of blow platform thickness and exterior platform angle the dependent variables are those attributes of the flakes which are often used in current lithic analyses and include interior platform angle length thickness and flake termination the results clearly show that exterior platform angle is highly significant for understanding many aspects of flake production these and other relationships between the independent and dependent variables are also discussed

luminescence dating of interglacial coastal depositional systems recent developments and future avenues of research abstract luminescence dating offers new opportunities to explore the evolution of quaternary marine coastal facies and landforms this review highlights the main advances in luminescence geochronology of interglacial coastal sediments through the analysis of 547 luminescence ages most of which were published during the last decade the majority of these reported luminescence investigations have been carried out along passive margin coasts since the turn of the century the discovery of a normalization procedure known as single aliquot regeneration sar has drastically reduced data scatter and improved precision with the consequence that quartz sar optically stimulated luminescence osl has become the dating protocol of choice for the last interglacial lig period a more complex technique known as thermally transferred osl tt osl is presumably proposed for dating older interglacials of the mid pleistocene and beyond feldspar luminescence is increasingly being applied to dating pleistocene sea level high stands due to a much higher dose saturation level than quartz osl the use of feldspar irsl infrared stimulated luminescence is limited by the occurrence of variable but ubiquitous anomalous fading af following the advent of af correction methods several middle pleistocene sites have been amenable to dating albeit with significant related uncertainties recently new protocols involving the measurement of post ir irsl at elevated temperatures have yielded relatively coherent ages for interglacial sediments up to ca 300 ka quartz osl tt osl af corrected irsl and post ir irsl ages are generally correlated with periods of sea level high stands a few ages are reported from the early and middle part of the middle pleistocene as mis11 9 and more commonly mis7 high stands are documented in strongly uplifting active margin coasts however by far the most obvious age peak corresponds to the end of the lig the mis5e shoreline is probably the most studied and luminescence dated coastal feature of all as the chronology of the sea level markers is crucial to assess global eustatic sea level variations through the course of the last interglacial nevertheless the observed abundance of young 100 120 ka luminescence ages for presumed mis5e sediments may underline methodological issues and or reflect the higher preservation potential of late regressive sequences on the other hand the occurrence of geographically distant reports of mis5a high stand might reflect a true eustatic origin for this event age analysis supports the impression of general reliability of luminescence for the timing of former sea level high stands there is a clear need to address issues in dose rate variability in the phenomenology of fading in feldspar and in the behaviour of luminescence growth with dose both in laboratory and natural conditions these could be addressed and properly evaluated by dating different minerals as multiple or single grains with consequent variable internal dose rates more robust practices in the application of luminescence dating techniques could eventually constrain the age uncertainties to no better than 2 3 therefore the strength of luminescence as a dating tool is more in terms of its extended age range and the ubiquity of datable material

introduction seismic wave scattering in three dimensionally heterogeneous earth the classical earth model of spherical symmetry or layered structure is undergoing a revolution the earth has been revealed to be laterally heterogeneous everywhere from the crust mantle to the core with scale from the grain size of rocks to the lowest orders of global spherical harmonics figure 1 shows the strength and scale length of heterogeneities in the crust and mantle of the earth in terms of v the perturbation index of seismic p or s wave speed defined as the r m s fractional variations of wave speed over the measured region the scale length of heterogeneities revealed by seismic waves not including the laboratory measurements of rock samples spans 8 orders of magnitude these heterogeneities with different scales have different effects to seismic waves the velocity and density heterogeneities can cause the change in waveform phase or travel time and amplitude fluctuation as well as apparent attenuation of the direct arrivals they can also generate coda waves such as the p coda s coda and lg coda caused by the lithospheric heterogeneities and precursory waves such as the scattered pkp waves as the precursors to pkikp caused by the heterogeneities near the core mantle boundary the near source or near receiver structures can modify the seismic waveforms by resonance and other effect rough topography or rough interface can cause the coupling between body wave and surface wave aligned cracks in the crust can produce the effective anisotrophy a great complexity arises when heterogeneities have interaction with anisotrophy and nonlinearity

the howiesons poort and msa iii at klasies river main site cave 1a we present the results of a technological analysis of the howiesons poort and msa iii lithic artifacts from cave 1a at klasies river we studied most of the debitage and retouched pieces from deacon s excavations about 3000 pieces and all the cores and retouched pieces from three layers of singer and wymer excavations 640 pieces our analysis shows 1 that hp blade production was based on the use of marginal percussion by soft stone hammer as at rose cottage 2 that impact scars at klasies rose cottage and sibudu indicate that the backed pieces were hafted in two differentways and 3 that the hp backed pieces were an innovativeway of hafting spear tips but are not clear evidence of the invention of bows and arrows we document the gradual evolution of debitage techniques within the hp sequence with progressive abandonment of the hp technological style very similar trends occur in the upper part of the hp sequence at rose cottage the similarity in temporal trends between sites separated by more than 600 km has significant implications for the disappearance of the hp industry we suggest that the disappearance of the hp was not due to a phenomenon of population contraction and isolation that caused the collapse of social networks the internal evolution and parallel process of change documented at klasies and rose cottage speak against a collapse of social systems and are associated with evidence of environmental and subsistence changes at the transition mis 4 3

the grotta dei fiori sardinia italy stratigraphical successions a key for inferring palaeoenvironment evolution and updating the biochronology of the pleistocene mammalian fauna from sardinia abstract in sardinia western mediterranean italy studies of quaternary climatic changes faunal turnovers and evolution of environments have mostly been performed autonomously in various scientific fields the grotta dei fiori cave gfc carbonia south western sardinia is one of the numerous limestone caves in south eastern sardinia that contain deposits of large and small mammals with intercalated flowstones a multidisciplinary study palaeontological sedimentological soil micromorphological analyses and u th dating was performed on three stratigraphical successions sa sc and sd for a finer time resolution and palaeoclimatical setting of the quaternary fossiliferous deposits cropping out in the gfc karst cave relying on u th dating results obtained by the stratigraphical and soil micromorphological analyses integrated with a previously performed stable isotope analysis indicate that the studied fossiliferous successions were deposited under warm alternate wet and dry climatic conditions albeit at different times in particular sediments of sc older than 500 ka were possibly deposited during the early middle pleistocene those of sa in a time interval from about 500 to 250 ka while the sd is older than about 350 ka the presence of microtus tyrrhenicola henseli in deposits older than 500 ka is of particular interest with regard to time and mode of the endemic vole evolution and to the biochronological arrangement of the late early to middle pleistocene sardinian fauna

seismic attenuation in the vicinity of the geothermal anomaly at urach obtained from near vertical reflection profiles1 the attenuation in the vicinity of the geothermal anomaly at urach was determined by means of two near vertical reflection profiles the attenuation in the sediments and in the upper crust 3 4 km depth was estimated by interpretation of the first refracted arrivals for calculating the attenuation the amplitude decay with respect to distance was used corrections for the spread factor i e the geometric amplitude divergence was deduced from the traveltime curves below the anomaly higher attenuation values q 1 0 008 were observed compared with those in the undisturbed crust q 1 0 002 this effect is probably due to the cracks and fissures in the upper part of the crystalline basement the attenuation in the middle and lower crust was determined using near vertical reflections from this depth interval the use of the spectral ratio method leads to higher values of the effective attenuation q 1eff below the heat flow anomaly compared to those of the normal crust this zone of high q 1eff coincides with the low velocity body below the heat flow anomaly both effects the higher attenuation and the lower velocities could be caused by high temperatures cracks and fissures in the crust

estimation of crustal stochastic parameters from seismic exploration data stochastic models for the crystalline crust produce synthetic seismograms that compare well with recorded data for a variety of crustal ages and tectonic environments in this paper we explore the parameter space describing such stochastic models as a basis for formulating the inverse problem that is we wish to estimate the parameters which define a stochastic model from the recorded backscattered wave field we base the estimation on approximate relations between the primary reflectivity series which is the ideal wave field response of a medium and various seismic gathers a two dimensional lateral correlation method is used to investigate the sensitivity of synthetic wave fields to horizontal characteristic length a derived empirical relationship relates the scale length to the half width of the correlation coefficient a horizontal wavenumber time domain spectral analysis successfully estimates the horizontal characteristic length ax and the fractal dimension d of the stochastic medium from which the wave field was backscattered we employ a monte carlo based optimization scheme to fit the observed spectral values to a one dimensional von karman function and simultaneously estimate values for ax and the hurst number the method yields consistent results when tested on synthetic data application of this technique to data sorted into different domains shows that zero offset sections yield the best estimate we also present results of our estimates using this method on a program for array seismic studies of the continental lithosphere passcal dynamite source shot gather and a vibroseis source consortium for continental reflection profiling cocorp data set recorded in the basin and range province

some attributes of wavefields scattered from ivrea type lower crust abstract the ivrea zone in northern italy is a well studied sliver of extended lower continental crust which was brought to the surface in the course of alpine lithospheric shortening based on two 1 25 000 geological maps from the central ivrea zone and petrophysical parameters of the corresponding lithologies we have constructed geologically constrained stochastic seismic models of ivrea type lower crust a stochastic rather than a deterministic approach is applied due to the limited availability of detailed geological maps and the high degree of small scale structural and petrophysical complexity of the ivrea zone the primary characteristic of the resulting model is its layered self affine or fractal structure and its bimodal velocity distribution while we are not suggesting that ivrea type structure is universal for extended lower continental crust synthetic seismograms may help to constrain some pertinent quantitative aspects observed in deep seismic reflection data 1 1 ivrea type lower crust can explain the igh observed reflection coefficients and bright reflectivity in the lower crust 2 2 observed lower crustal q factors can be largely explained by scattering losses and intrinsic q factors of reflective lower crust are likely to be larger than 1000 which is incompatible with the presence of free volatiles 3 3 in agreement with recent broad band studies of the lower crust ivrea type lower crust does not create any tuning effects and 4 4 for ivrea type heterogeneity the lateral correlation of the reflected signal is largely independent of the lateral characteristic scale of the scattering structures which suggests that multiple scattering may be important in the reflective lower crust

lower crustal reflectivity from waveform inversion summary deep seismic reflection profiles show that the lower part of the continental crust often contains many strong subhorizontal reflections based on forward modelling these reflections are interpreted as a sequence of alternating high and low velocity layers a waveform inversion provides an optimum model by minimizing the misfit between observed data and synthetic seismograms however it is very difficult to invert for the whole data set partly because of the large computation time needed in modelling and partly because the high amplitude reflected energy in the upper crust dominates the misfit function to overcome these difficulties we propose a three step strategy for inverting the deeper part of seismic reflection data over a narrow aperture in which the velocity structure can be assumed to be 1 d first both source wavelet and recorded wavefield are propagated in the plane wave domain downwards to a particular depth for a given 1 d medium because the source receiver distances are short for deep reflections it is assumed that these reflections are at normal incidence it is also assumed that the near surface velocity is known or has been estimated using other inversion schemes the downward propagation algorithm takes account of nearsurface effects such as multiple reflections and attenuation second starting from a known background velocity model a non linear iterative waveform inversion is applied to the propagated data set the method is based on minimizing the difference sample by sample between observed and calculated wavefields in a least squares sense the forward modelling which consists of calculating the data from the model uses a reflectivity method to compute the synthetic seismogram in the plane wave domain the model perturbation is calculated with the help of the conjugate gradients method the non linear inversion gives the short wavelengths of impedance contrast which is a function of density and velocity in the lower crust third an interpretational step is tried in order to recover the medium wavelengths of velocity the algorithm is tested on synthetic data and then applied to a part of the wam data set south west of england a good fit to the real data with the optimum model predicts that the velocity contrast of the layers in the lower crust varies from 0 2 km s to 0 5 km s and the thickness from at least 0 075 km to 1 km

rupture dynamics and ground motions from earthquakes in 2 d heterogeneous media we perform 2 d simulations of earthquakes on rough faults in media with random heterogeneities with von karman distribution to study the effects of geometric and material heterogeneity on the rupture process and resulting high frequency ground motions in the near fault region out to 20 km variations in slip and rupture velocity can arise from material heterogeneity alone but are dominantly controlled by fault roughness scattering effects become appreciable beyond 3 km from the fault near fault scattering extends the duration of incoherent high frequency ground motions and at least in our 2 d simulations elevates root mean square accelerations i e arias intensity with negligible reduction in peak velocities we also demonstrate that near fault scattering typically occurs in the power law tail of the power spectral density function quantified by the hurst exponent and another parameter combining standard deviation and correlation length

a deterministic and stochastic velocity model for the salton trough basin and range transition zone and constraints on magmatism during rifting as a high resolution addition to the 1992 pacific to arizona crustal experiment pace a 45 km long deep crustal seismic reflection profile was acquired across the chocolate mountains in southeastern california to illuminate crustal structure in the transition between the salton trough and the basin and range province the complex seismic data are analyzed for both large scale deterministic and fine scale stochastic crustal features a low fold near offset common midpoint cmp stacked section shows the northeastward lateral extent of a high velocity lower crustal body which is centered beneath the salton trough off end shots record a high amplitude diffraction from the point where the high velocity lower crust pinches out at the moho above the high velocity lower crust moderate amplitude reflections occur at midcrustal levels these reflections display the coherency and frequency characteristics of reflections backscattered from a heterogeneous velocity field which we model as horizontal intrusions with a von karman fractal distribution the effects of upper crustal scattering are included by combining the mapped surface geology and laboratory measurements of exposed rocks within the chocolate mountains to reproduce the upper crustal velocity heterogeneity in our crustal velocity model viscoelastic finite difference simulations indicate that the volume of mafic material within the reflective zone necessary to produce the observed backscatter is about 5 the presence of wavelength scale heterogeneity within the near surface upper and middle crust also produces a 0 5 s thick zone of discontinuous reflections from a crust mantle interface which is actually a first order discontinuity

lithoprobe new perspectives on crustal evolution lithoprobe is canada s national collaborative multidisciplinary earth science research program directed toward an enhanced understanding of how the north american continent evolved research in i

sensitivity of the lateral correlation function in deep seismic reflection data in the absence of multiple scattering the lateral correlation function of the reflected wavefield can be related to the lateral correlation function of the medium we have analyzed the lateral correlation function of a series of synthetic seismograms from stochastic models of reflective lower crust with the structural and petrophysical statistics of the ivrea zone our results show that in the presence of ivrea type lower crustal heterogeneity the lateral correlation function of the backscattered wavefield is insensitive to the lateral correlation function of the scattering medium which suggests that multiple scattering is important in the reflective lower crust this interpretation is consistent with lower crustal reflections commonly being shorter than a fresnel zone the absence of clear diffractions and the poor performance of standard migration algorithms on deep seismic reflection data

macroscopic approaches to the identification of expedient bivalve tools a case study investigating polymesoda geloina coaxans bivalvia corbiculidae shell valves from princess charlotte bay queensland australia the identification of expedient bivalve tools recovered from archaeological deposits is currently hindered by a lack of analytical frameworks in order to identify those shell valves which have been used as expedient tools analysts must be able to identify and distinguish between pre mortem and post depositional modifications and use wear from tool use central to this difficulty is a lack of experimental analogues for comparison with archaeological material here we present an analytical framework for the identification of expedient bivalve tools made from polymesoda geloina coaxans valves recovered from australian archaeological sites this analytical framework consists of a series of actualistic experiments designed to determine those variables useful for distinguishing between modifications produced via pre mortem and post depositional processes that can damage molluscan shell and damage produced via use as an expedient tool trampling flaking and scraping experiments and use wear analysis are used as a reference for comparison with an assemblage of p coaxans valves recovered from archaeological sites in princess charlotte bay north queensland australia we demonstrate that an analytical framework consisting of an analysis of shell area loss shell fracture paths and use wear can be successfully applied to archaeological samples to confidently distinguish between those valves which have been used as expedient tools and those which have not this research has wider implications for the identification of this often overlooked class of shell tools from archaeological sites in australia and other regions allowing a more comprehensive understanding of the place of shell tools in coastal economies of the past

a novel ebsd based finite element wave propagation model for investigating seismic anisotropy application to finero peridotite ivrea verbano zone northern italy a novel electron backscatter diffraction ebsd based finite element fe wave propagation simulation is presented and applied to investigate seismic anisotropy of peridotite samples the fe model simulates the dynamic propagation of seismic waves along any chosen direction through representative 2d ebsd sections the numerical model allows separation of the effects of crystallographic preferred orientation cpo and shape preferred orientation spo the obtained seismic velocities with respect to specimen orientation are compared with voigt reuss hill estimates and with laboratory measurements the results of these three independent methods testify that cpo is the dominant factor controlling seismic anisotropy fracture fillings and minor minerals like hornblende only influence the seismic anisotropy if their volume proportion is sufficiently large up to 23 the spo influence is minor compared to the other factors the presented fe model is discussed with regard to its potential in simulating seismic wave propagation using ebsd data representing natural rock petrofabrics

experimental use and quantitative performance analysis of triangular flakes levallois points used as arrowheads the invention and widespread use of projectile weaponry is a characteristic presumed to exist only with homo sapiens however as finds of wooden material during the early development of projectile weapons are extremely rare this remains a contentious topic recent work has proposed a series of ballistically significant morphological characteristics of stone points that yield information about their potential use here we report on initial experimental approaches to quantifying the performance of relatively simple stone points as arrow armatures two experimental trials were performed using a series of 51 levallois points the first against a uniform density target was designed to give an overall indication of performance the second against a simulated animal carcass demonstrated the durability of these points the results of this study suggest that small levallois points could have functioned as arrowheads albeit ones likely to break after limited use they also suggest that these points penetrating power is strongly controlled by their morphometric characteristics most notably their perimeter this latter finding refines a method for assessing hypothetical paleolithic stone points on the basis of tip cross sectional area previously proposed by others

putslaagte 1 pl1 the doring river and the later middle stone age in southern africa s winter rainfall zone abstract existing data suggest weak human occupation of southern africa s winter rainfall zone wrz during later marine isotope stage mis 3 the causes of which are unknown here we report briefly on the results of recent surveys of alluvial terrace sites of the doring river in the wrz which document occupation over a broad expanse of the later middle stone age msa and pleistocene later stone age we then report on test excavations at one terrace site denoted putslaagte site 1 pl1 describe in detail the assemblage of flaked stone artefacts produced from that excavation and present two osl ages obtained from 0 8 m to 1 5 m below surface the results suggest that a artefact accumulations at pl1 are dense b the technological systems documented are characteristically msa but differ in form from the range of systems known from other excavated sites in the region and c that the assemblages accumulated in mis 3 taken together with the survey data the results introduce new variation into the later msa in southern africa and imply reorganisation of land use in the wrz in late mis 3 rather than abandonment we suggest that a research emphasis on rock shelter deposits may have produced misleading depictions of regional occupation

statistical approaches to interpretation of seismic reflection data abstract statistical approaches offer a potentially powerful tool for interpretation of the complex seismic reflection patterns typically recorded from the crystalline crust these methods focus on characterization of the complexity scaling characteristics and spatial variability of the wave field with the ultimate aim of recovering information on the geometric variation of the geology in this paper we examine the potential and limitations of statistical approaches focusing on the issues of quality of the statistical estimator how noise and migration affect spatial statistics and the potential for both qualitative and quantitative approaches to statistics based interpretation the limited spatial bandwidth of typical seismic data presently inhibits complete quantitative recovery of the spatial properties of the geology migration which should increase the spatial bandwidth has to date not proven particularly effective on complex wave fields mapping of relative variation in the spatial properties of the wave field reveals subtle differences that are directly associated with the geometric character of the geology such mapping allows identification and mapping of variations in the geologic fabric at scales significantly larger than the seismic wavelength and objective access to scaling information that has previously been unavailable

seismic refraction investigation of the black forest abstract within the framework of site surveys of the deep continental drilling program ktb deep seismic sounding experiments were carried out in the black forest southwest germany in august 1984 these site surveys comprised seismic refraction as well as seismic reflection measurements this paper will concentrate on the interpretation of the refraction data which were observed along a 240 km long line approximately following the morphological axis of the black forest in a n s direction and extending in the south into the swiss molasse basin from the available seismic refraction data a detailed velocity depth model of the crust and uppermost mantle was derived a clear phase refracted in the basement with a velocity of 5 9 km s is observed for all shots this phase is followed by a reflection from the upper boundary of a low velocity zone this zone is very accentuated under the northern and central black forest and is characterized by a velocity decrease from 6 2 to 5 4 km s between depths of about 8 and 14 km towards the south the velocity inversion gradually loses its intensity under the center of the southern black forest velocities of about 6 km s prevail throughout the upper crust the lower crust which starts at the lower boundary of the low velocity zone shows a very complicated response in the record sections due to long reverberations between travel times of 1 5 3 5 s reduced by 6 0 km s at an epicentral distance of approximately 30 70 km a classical phase correlation is not possible based on a combined interpretation of near angle and wide angle reflection data the lower crust is characterized by a stack of thin layers with alternating high and low velocities the average velocity of the laminated zone is 6 7 km s the reflection from the moho at a depth of 25 26 km is the most prominent phase at epicentral distances greater than 60 km

establishing statistical confidence in cortex ratios within and among lithic assemblages a case study of the middle paleolithic of southwestern france abstract recent studies have demonstrated the usefulness of the cortex ratio for quantifying the cortex composition in lithic assemblages and as a viable index of prehistoric artifact transport yet the lack of means for assigning statistical confidence to archaeologically observed cortex ratios inhibits the approach s utility for objective comparisons and interpretation here we derive statistical confidence for archaeological cortex ratios through monte carlo and resampling techniques experimental data with known geometric properties and measured cortex values were employed as a reference for attaching a probability to an archaeological assemblage s cortex ratio the method is demonstrated on assemblages from the middle paleolithic sites of roc de marsal pech de l aze iv and combe capelle bas in southwestern france

middle stone age reduction strategies at the desert s edge a multi site comparison across the gebel akhdar of northeast libya abstract haua fteah cave situated between the mediterranean coast and the gebel akhdar of northeast libya preserves rich middle stone age msa and late stone age lsa cultural horizons excavated in the 1950s and more recently the richness and time depth of the cave s archaeological record are unsurpassed by any other site in northern cyrenaica as a result the haua fteah sequence has long been used to represent the culture history of the region as a whole recent geoarchaeological surveys of the gebel akhdar as well as pre desert and desert biomes further to the south have resulted in the discovery of numerous msa and lsa sites the vast majority of these sites consist of surface lithics that cannot be dated currently in contrast parts of the haua fteah sequence have been dated using various chronometric methods using data collected through lithic attribute analysis coupled with various statistical approaches including discriminant function analysis or dfa this paper explores variation in core reduction strategies within haua fteah from the early msa to early lsa collections of cores from various sites located throughout the landscape are contrasted against those from haua fteah by comparing undated cores from the landscape with those from different occupation phases at haua fteah dfa classification is tested as a method for imparting an approximate chronology to the former the results indicate notable variation in reduction strategies within the msa at haua fteah and notable similarities between early msa pre aurignacian and early lsa early dabban core morphologies and technologies because of the latter in particular together with several other factors that may be underpinning spatio temporal variability in core reduction strategies caution is recommended in loosely assigning approximate chronologies to surface lithic sites

two dimensional elastic pseudo spectral modeling of wide aperture seismic array data with application to the wichita uplift anadarko basin region of southwestern oklahoma abstract full wave field modeling of wide aperture data is performed with a pseudospectral implementation of the elastic wave equation this approach naturally produces three component stress and two component particle displacement velocity and acceleration seismograms for compressional shear and rayleigh waves it also has distinct advantages in terms of computational requirements over finite differencing when data from large scale structures are to be modeled at high frequencies the algorithm is applied to iterative two dimensional modeling of seismograms from a survey performed in 1985 by the university of texas at el paso and the university of texas at dallas across the anadarko basin and the wichita mountains in southwestern oklahoma the results provide an independent look at details of near surface structure and reflector configurations near surface 70 per cent of the energy in the observed seismograms the interpretation of the data is consistent with the results of previous studies of these data but provides considerably more detail overall the p wave velocities in the wichita uplift are more typical of the middle crust than the upper crust 5 3 to 7 1 km sec at the surface the uplift is either exposed as weathered outcrop 5 0 to 5 3 km sec or is overlain with sediments of up to 0 4 km in thickness ranging in velocity from 2 7 to 3 4 km sec generally increasing with depth the core of the uplift is relatively seismically transparent a very clear coherent reflection is observed from the mountain view fault which dips at 40 to the southwest to at least 12 km depth velocities in the anadarko basin are typical of sedimentary basins there is a general increase from 2 7 km sec at the surface to 5 9 km sec at 16 km depth with discontinuous reflections at depths of 8 10 12 and 16 km

the crust as a heterogeneous optical medium or crocodiles in the mist abstract based on petrophysical data geologic maps and a well log we present statistical descriptions of likely upper middle and lower crustal rocks to characterize the fine scale heterogeneity observed in crustal exposures and inferred from deep crustal seismic data the statistical models developed for granitic and metamorphic upper crust and for an extended metamorphic lower crust are used to construct whole crustal models of seismic velocity heterogenity we present finite difference synthetic cmp data from several models which compare favorably with field data the statistical models also permit classification of the seismic reflection experiment and the crustal heterogeneity according to scattering regime the optical or scattering properties of importance for classification are the velocity fluctuation intensity the horizontal and vertical correlation lengths of the medium the correlation function of the medium and the velocity population function for the crustal properties we measured the bandwidth of a typical deep crustal experiment overlaps from the weak to the strong scattering regime with implications for crustal seismic data processing and imaging notably deep crustal signals are likely to have experienced multiple scattering making common seismic imaging techniques of questionable value moreover the details of the unmigrated cmp stacked section bears little resemblance to the underlying medium

the autocorrelation function an image processing tool for fabric analysis abstract the use of the autocorrelation function acf is proposed as a method for fabric and or strain analysis its chief purpose is to extend fabric analysis to fine grained materials such as clays micrites etc or to materials where the determination of individual grain shapes is tedious or impossible the main advantage of the method is that no segmentation of the image prior to analysis is necessary in other words any bias associated with identifying grain boundaries and the like is avoided in as much as the recognition of grains or grain boundaries is a matter of scale the acf can be used without loss of generality whenever the grain size is small in comparison with the size of the analysed area the method is computer based it requires a scanner for the digitization of the images and sufficient storage space and computing power for digital image processing the method uses half tone images as input these can be obtained from thin sections acetate peels polished surfaces photographic negatives or positives etc the acf is a two dimensional function that is related to the average shape that occurs in the fabric it is scaled with respect to the original image and allows simultaneous analysis of small and large features the acf enables a a quantitative description of the fabric in general terms b an efficient grain size determination and c if strain is a valid interpretation of the fabric the derivation of the finite strains in the plane of observation in the first part of the paper the acf method is introduced by way of a few numerically generated fabrics and compared to other methods of fabric and strain analysis in the second part an application to three samples of experimentally deformed solnhofen limestone is demonstrated

incorporating sinuous connectivity into stochastic models of crustal heterogeneity examples from the lewisian gneiss complex scotland the franciscan formation california and the hafafit gneiss complex egypt stochastic models are valuable and sometimes essential tools for investigating the behavior of complex phenomena in seismology stochastic models can be used to describe velocity heterogeneities that are too small or too numerous to be described deterministically where analytic approaches are often infeasible synthetic realizations of such models can be used in conjunction with finite difference algorithms to systematically investigate the response of the seismic wave field to complex heterogeneity this paper represents a continuing effort at formulating a complete and robust stochastic model of lithologic heterogeneity within the crust and the means of generating synthetic realizations complete implies that the model is flexible enough to describe all types of random heterogeneity within the crust while robust implies sufficiently constrained parameterization that an inversion problem may be well posed as a basis for investigation we use geologic maps of crustal exposures and petrophysically inferred velocities earlier efforts at stochastic modeling have focused on characterization of the univariate probability density function which is typically modal i e binary ternary etc and the covariance function which is typically fit with a von karman function here we provide a means of characterizing the property of sinuous connectivity and for generating realizations that possess this property sinuous connectivity is the tendency for individual lithologic units to be continuous over long and highly contorted paths there is no means in the earlier modeling of either characterizing or synthesizing this property we generate sinuously connective realizations by mapping regions encompassed by two contours in a gaussian distributed surface into the two values of the binary field this operation is nonunique as one can choose in many ways the values for the contours

the influence of raw material size on stone artefact assemblage formation an example from bone cave south western tasmania this paper specifically examines the influence of raw material size on stone artefact assemblage formation in conjunction with two behavioural assemblage formation processes reduction intensity and artefact transport the aim is to establish whether raw material size can influence the way in which reduction intensity and artefact transport form a stone artefact assemblage and should a significant influence be established whether this has any bearing on human behavioural reconstructions this is first investigated in an experimental setting followed by an archaeological setting using a quartzite and chert assemblage from bone cave in south western tasmania reduction intensity and artefact transport are respectively measured using the scar density index flake to core ratio non cortical to cortical flake ratio and cortex ratio while tool blank sizes are also reconstructed the combined experimental and archaeological analyses find that raw material size variation is capable of exerting a substantial influence on stone artefact assemblage formation this particularly with reference to the nature of change in stone artefact assemblages both reduction intensity and artefact transport will alter assemblage composition at faster rates when nodule sizes are smaller this can have significant implications for intra and inter site reconstructions of past human behaviour

evidence for progressive holocene aridification in southern africa recorded in namibian hyrax middens implications for african monsoon dynamics and the african humid period abstract presented here are stable nitrogen isotope data from a rock hyrax procavia capensis middens from northwestern namibia that record a series of rapid aridification events beginning at ca 3800 cal yr bp and which mark a progressive decrease in regional humidity across the holocene strong correlations exist between this record and other terrestrial and marine archives from southern africa indicating that the observed pattern of climate change is regionally coherent combined these data indicate hemispheric synchrony in tropical african climate change during the holocene with similar trends characterising the termination of the african humid period ahp in both the northern and southern tropics these findings run counter to the widely accepted model of direct low latitude insolation forcing which requires an anti phase relationship to exist between the hemispheres the combined dataset highlights 1 the importance of forcing mechanisms influencing the high northern latitudes in effecting low latitude climate change in africa and 2 the potential importance of solar forcing and variations in the earth s geomagnetic shield in determining both long term and rapid centennial scale climate changes identifying a possible mechanism for the variations marking the ahp termination in both the southern and northern tropics

the crustal structure of western europe a thorough understanding of the tectonic processes that formed the con tinental lithosphere under changing geometric and physical conditions through time requires detailed knowledge of the structure of the crust one of the best locations to study this fundamental problem is the northern and western part of europe because it is made up of a number of tectonic provinces ranging in succession from the oldest precambrian areas of fennoscandia to the currently active regions of the mediterranean sea the geology of europe a region extending from the northern tip of scandinavia north cape southward to north africa encompasses the pre 2500 ma archean craton in the northernmost part of the baltic or fennoscandian shield the proterozoic paleozoic and cenozoic pro vinces of northern and central europe that have been added on to this nucleus and the active transition zone between the eurasian and african plates in the mediterranean area cf figure 1 from a tectonic geologic point of view europe can be divided into four main units that cover the whole time span of the history of the continental crust

seismic anisotropy of metapelites from the ivrea verbano zone and serie dei laghi northern italy abstract laboratory measurements of compressional and shear wave velocities up to 600 mpa confining pressure were carried out on amphibolite to granulite facies metapelites from the serie dei laghi and ivrea verbano zone northern italy the metapelite samples show moderate to high compressional wave anisotropy and significant shear wave splitting for propagation directions parallel to foliation serie dei laghi samples are generally transversely isotropic for compressional wave propagation a pattern that based on calculated velocities is the consequence of strong preferred orientation of micas ivrea verbano samples generally have an orthorhombic anisotropy pattern for compressional waves that is caused by the preferred orientation of both mica and sillimanite shear wave anisotropy and shear wave splitting patterns differ significantly for the two fabric types intense static recrystallization can obliterate seismic anisotropy but partial static recrystallization does not appreciably reduce anisotropy we conclude that seismic anisotropy may occur in mid to lower continental crust where it is predominantly composed of metapelitic rocks and if there is a consistent regional fabric this seismic anisotropy may be diminished if there is no consistent regional fabric or if postmetamorphic intrusions have caused static recrystallization

upper crustal seismic velocity heterogeneity as derived from a variety of p wave sonic logs sonic log measurements provide detailed 1 d information on the distribution of elastic properties within the upper crystalline crust at scales from about one metre to several kilometres 10 p wave sonic logs from six upper crustal drill sites in europe and north america have been analysed for their second order statistics the penetrated lithological sequences comprise archean volcanic sequences proterozoic mafic layered intrusions and precambrian to phanerozoic gneisses and granites despite this variability in geological setting tectonic history and petrological composition there are notable similarities between the various data sets after removing a large scale deterministic component from the observed velocity depth function the residual velocity fluctuations of all data sets can be described by autocovariance functions corresponding to band limited self affine stochastic processes with quasi gaussian probability density functions depending on the maximum spatial wavelength present in the stochastic part of the data the deterministic trend can be approximated either by a low order polynomial best fit or by a moving average of the original sonic log data the choice of the trend has a significant impact on the correlation length and on the standard deviation of the residual stochastic component but does not affect the hurst number for trends defined by low order polynomial best fits correlation lengths were found to range from 60 to 160 m whereas for trends defined by a moving average the correlation lengths are dominated by the upper cut off wavenumber of the corresponding filter regardless of the trend removed the autocovariance functions of all data sets are characterised by low hurst numbers of around 0 1 0 2 or equivalently by power spectra decaying as 1 k a possible explanation of this statistical uniformity is that sonic log fluctuations are more sensitive to the physical state in particular to the distribution of cracks than to the petrological composition of the probed rocks

stochastic modeling of seafloor morphology inversion of sea beam data for second order statistics at scale lengths less than 100 km or so statistical descriptions of seafloor morphology can be usefully employed to characterize ridge crest processes off ridge tectonics and vulcanism sedimentation and postdepositional transport we seek to develop methods for the estimation of seafloor statistics that take into account the finite precision resolution and sampling obtained by actual echo sounding systems in this initial paper we restrict our attention to the problem of recovering second order statistics from data sets collected by multibeam devices such as sea beam the seafloor is modeled as a stationary zero mean gaussian random field completely specified by its two point covariance function we introduce an anisotropic two point covariance function that has five free parameters describing the amplitude orientation characteristic wave numbers and hausdorff fractal dimension of seafloor topography we formulate the general forward problem relating this model to the statistics of an ideal multibeam echo sounder in particular the along track autocovariance functions of individual beams and the cross covariance functions between beams of arbitrary separation using these second moments as data functionals we then pose the inverse problem of estimating the seafloor parameters from realistic noisy data sets with finite sampling and beamwidth and we solve this inverse problem by an iterative linearized least squares method the inversion method is applied to sea beam transit data from both the pacific and atlantic oceans sea beam system noise stands out as a sharp spike on the along track autocovariance function and can be modeled as a white noise process whose amplitude generally increases with beam angle the five parameters in our second order model can be estimated from the inversion of data sets comprising 100 200 km of track length in general the cross track wave number is the most poorly determined although uncertainties in the assumed sea beam response may bias the values of the fractal dimension using the assumed beamwidth the measured noise values and the seafloor parameters recovered from the inversion we generate sea beam synthetics whose statistical character can be directly compared with raw sea beam data for most of the track segments we have processed thus far the synthetics are similar to the data in the case of one atlantic profile however the comparison clearly indicates the necessity of incorporating higher order statistics the space domain procedures described in this paper can be extended for this purpose

seismic scattering in the upper crystalline crust based on evidence from sonic logs summary evidence from sonic logs indicates that velocity fluctuations in the upper crystalline crust are remarkably uniform this motivates a generic approach to classifying uppercrustal seismic heterogeneity and to studying implications for seismic wave propagation the resulting canonical model of upper crustal seismic structure is characterized by a spatially isotropic von karman autocovariance function with a z 100 m 0 15 and cj 300 m s small angle scattering theory is used to predict the transition from weak to strong scattering as well as phase fluctuations and scattering attenuation compared with exponential random media v 0 50 the high fractal dimension i e small values of v of upper crustal heterogeneity causes smaller phase fluctuations and transition from weak to strong scattering at lower frequencies and shorter path lengths acoustic finite difference modelling shows that seismic reflections from deterministic features surrounded by heterogeneities are severely degraded when they fall into the strong scattering regime conversely traveltime fluctuations of transmitted waves are found to be relatively insensitive to the transition from weak to strong scattering upper crustal scattering q is predicted to lie between 600 and 1500 which is one to two orders of magnitude higher than q values inferred from seismic data this suggests that seismic attenuation in the upper crystalline crust is dominated by anelastic effects rather than by scattering

the effect of indentor type on flake attributes evidence from a controlled experiment this paper presents the results of a controlled experiment which examined the relationship between two different indentor types and 11 flake attributes it was found that the flake attributes commonly used by archaeologists to infer the prehistoric use of soft indentors are more likely a result of flintknapping technique employed during soft hammer flaking than differences produced by indentor type antler indentors do affect how the flake mass is distributed into the dimensional attributes of flake length and thickness thereby maximizing their efficiency for transport and for raw material conservation

variability in the middle stone age lithic sequence 115 000 60 000 years ago at klasies river south africa abstract stratified samples of artefacts from the late pleistocene deposit at the klasies river main site covering some 60 000 years have been studied variability in the artefact sequence has been documented in the technologies of artefact production in addition to conventional typological analysis particular emphasis has been given to the recognition of the reduction sequences used in producing the pre formed blanks that are a feature of the middle stone age the results show that the variability is due to changes between the dominant blade and or point technological conventions traditions through time technological study supports and gives meaning to the recognition of distinct sub stages msa i klasies river msa ii mossel bay howiesons poort and a post howiesons poort at main site these sub stages are more than convenient site specific organizational entities they delineate separate technological conventions that may have relevance on a sub continental scale

what attributes are important for the measurement of assemblage reduction intensity results from an experimental stone artefact assemblage with relevance to the hoabinhian of mainland southeast asia abstract our understanding of variation in the technology of flaked stone artefacts from mainland southeast asia during the terminal pleistocene and holocene periods has improved little since they were originally labelled hoabinhian in 1932 chronological and geographical variation has been described in terms of typological differences but there are few anthropological explanations of lithic diversity and change an analysis of an experimentally produced hoabinhian assemblage is undertaken here to show which flake variables are significant indicators of assemblage reduction intensity the results show that recording the presence of overhang removal interior platform angle and percentage of dorsal cortex will provide robust data on the extent of assemblage reduction a new method for detecting assemblage variation based on the location of dorsal cortex on flakes is also presented and experimentally verified these methods are designed to take advantage of the typical geometry and reduction patterns of hoabinhian assemblages these findings provide another tool to build anthropological explanations of hoabinhian archaeology

crustal structure of the northwestern basin and range province from the 1986 program for array seismic studies of the continental lithosphere seismic experiment the basin and range province of the western united states is characterized by active east west extension at strain rates of 1 cm yr 1 high regional heat flow of 90 mw m 2 and widespread late cenozoic bimodal rhyolitic basaltic magmatism the 1986 program for array seismic studies of the continental lithosphere basin and range seismic experiment imaged a portion of northwestern nevada to determine the crustal structure and to assess reported differences between refraction versus reflection determinations of moho depth and how the crustal composition and structure has been influenced by volcanic and extension mechanisms our interpretation of the refraction wide angle reflection data suggests that the crust is fairly uniform in thickness and varies by less than 5 km over the 280 km east west profile and 3 km over its 220 km north south length we characterize the velocity structure by five layers 1 an upper most crust composed of sedimentary rocks and basement that has an average velocity of 5 7 km s i 2 a middle crust that extends to a depth of 18 22 with an average velocity of 6 1 km s 1 3 a 10 12 km thick lower crust with an average velocity of 6 6 km s 1 4 a 2 5 km thick transitional crust mantle boundary defined by a 7 6 km s l velocity and 5 an upper mantle with an average pn velocity of 7 9 8 0 km s 1 these data show a uniformily thick crust of 28 km 5 km beneath northwestern nevada and a lack of evidence for significant low velocity crustal layers in general the entire crustal column exhibits uniform positive velocity gradients of 0 02 0 04 s the midcrustal discontinuity is interpreted as a small velocity increase of 0 2 km s l at 18 km depth the absence of a significant midcrustal reflection and the presence of large velocity gradients throughout the crust arises either from 1 a systematic increase in mafic composition with depth or 2 possibly high lower crustal pore pressure that acts to decrease the velocity contrast across the midcrustal boundary our interpreted seismic velocity structure is consistent with a broad range of bulk compositions for the crust upper crustal velocities are consistent with bulk compositions that range from metasediments and granites at shallow depth to diorites at midcrustal levels while lower crustal velocities suggest bulk compositions that range from diorites and amphibolities at midcrustal depths to mafic granulites and gabbros at the base of the crust the uniform crustal thickness of 30 34 km in northwestern nevada is close to the crustal average for the basin and range province but is thin when compared to surrounding regions such as the sierra nevada and colorado plateau where crustal thickness is greater than 40 kin similarily northwestern nevada pn velocities of 7 9 8 0 km s 1 are near the province wide average of 7 9 km s l temperature corrected pn velocities from a 90 mw m 2 geotherm for the basin and range to 60 mw m 2 for the stable interior of the united states are within one standard deviation of the continental average of 8 05 km s i and suggest a uniform upper mantle composition across the basin and range in addition to these observations the homogeneity of the velocity structure beneath the western basin and range argues for a youthful moho and crust that has been reworked by province wide late cenozoic extension episodic magmatism and underplating

features of the water mass front in the northwestern north pacific analysis of the hydrographic data taken in the northern north pacific has revealed a water mass front defined as the abrupt change of mixing rates between the two typical water masses typical water masses are situated above the main thermocline in the subtropical and subpolar gyres this front termed water mass front in the present study can be regarded as the boundary between the subtropical gyre and the subpolar gyre the index for detecting the frontal position from the temperature field is given as the 5 c isotherm at the 300 m level comparisons with data from previous studies are also made and this front appears to correspond to the subarctic front in almost every instance

measuring core reduction using 3d flake scar density a test case of changing core reduction at klasies river mouth south africa a new core reduction index is presented calculated as the ratio of flake scar number to 3d surface area sdi the index is tested experimentally on five types of core blade discoid levallois biface and multiplatform cores and then applied to the core assemblages from five sub stages of the middle stone age at klasies river mouth south africa preliminary results indicate that the sdi possesses the desirable attributes of a successful reduction index and is a significant improvement on traditional proxy measures of core reduction the results of the archaeological case study confirm previous untested observations that cores from the howiesons poort and msaiii sub stages are more heavily reduced than preceding and following stages and that local and exotic raw materials as well as different types of cores are all more heavily reduced during these periods the sdi fills a significant lacuna in available core reduction measures

the structure and nature of the moho beneath central iberia abstract the moho is the most conspicuous feature in the alcudia deep normal incidence and wide angle seismic reflection datasets acquired across the central iberia zone this discontinuity appears to be sub horizontal with a slight dip toward the center of the iberian peninsula beneath the tajo basin densely spaced wide angle seismic reflection data reveal conspicuous pmp and sms reflections in the shot records these reflections arriving over a 1 5 s time window and characterized by a relatively low frequency content are used to infer the internal structure and characteristics of this crustal boundary in an effort to place constraints on its nature beneath the studied area the wide angle shot records were processed in order to generate low fold stacks that reveal gradual deepening of moho pmp phases from 10 2 s twt 31 km in the central iberian zone to 11 8 s twt 36 km beneath the tajo basin the moho seismic signature was the main objective of a series of 1 d and 2 d synthetic modeling simulations reflectivity modeling was used as the 1 d modeling approach and an elastic finite difference scheme was used for the 2 d modeling the moho can be considered to be a self similar fractal heterogeneous media with a bimodal velocity distribution alternating crustal and mantle values with horizontal correlation lengths that range between 1 and 4 km and vertical correlation lengths that range from 0 2 to 1 km the depth of this boundary is most probably the result of late to post variscan re equilibration processes affecting a previously deformed and laminated lower crust the mechanisms that took part in this process might have differed to the north and south of the sampled central iberian zone being more thermally induced to the north near the central system processes leading to the layered structure of the moho boundary either tectonic or magmatic should be further investigated

petrographic interpretation of a complex seismic crust mantle transition in the central eastern alps abstract a recent reinterpretation of the existing dss profiles scarascia and cassinis tectonophysics 271 1997 157 188 led to a reconstruction of the moho boundary and of the lower crust in the central eastern alpine sector where the european and the adriatic domains are deeply indented in that work a complex crust mantle transition composed of alternating low and high velocity layers was observed in the deepest bottom of the european crust in the same work it was confirmed that the european lower crust beneath the alpine range is characterised by a very low seismic velocity while the velocity of the adriatic lower crust reaches the average values found in collisional belts the interpretation of these features has been performed employing a data base of ultrasonic seismic measurements the ivrea verbano zone has been assumed as an analogue of crust mantle transition a statistical approach was used to associate the bodies of the interpreted seismic models to the lithotypes a petrological model is attempted in order to suggest an explanation of the observed phenomena assuming physical and compositional constraints appropriate to the alpine collisional belt cumulitic peridotites and pyroxenites lenses in a gabbroic host rock fit the observed seismic structure of the crust mantle transition the upper mantle lies below a transition zone and is characterised by a velocity of 8 2 km s detected by p n phases in our study it is interpreted as a spinel to garnet peridotite the anomalous low velocity of the european lower crust is discussed but still remains an open subject

seismic attenuation in the continental crust sw of england summary significant variability in crustal attenuation exists off england s sw coast as shown by birps deep seismic reflection lines the presence of the thick cornubian batholith with no sedimentary cover acting as a low attenuating region compared to normal upper crust with about 300 m of sedimentary cover can account for the observed differences in the strength of signal returning from the lower crust application of the spectral amplitude ratio method to determine the effective quality factor q of the lower crust beneath the granite yields a value of 400 200 a modification of the spectral amplitude ratio method to measure relative q s at different locations indicates that the average q of the upper and middle crust containing the granite is twice that elsewhere although the hypothesis that the lower crustal composition differs significantly beneath the granite cannot be ruled out geological and seismic observations suggest that differential attenuation is the main factor causing variation in the observed reflectivity thus thick granites act as low attenuating windows to the lower crust

a stochastic view of lower crustal fabric based on evidence from the ivrea zone despite its complicated history the ivrea zone is considered to be a representative surface exposure of extended continental crust we have digitized two standard 1 25 000 geological maps from this area and evaluated their structural statistics because of the subvertical orientation of the ivrea zone these maps can be considered as small scale cross sections through the lower continental crust the autocorrelation functions of the digitized lithologies measured from these maps show a clear self similar or fractal rather than a gaussian or deterministic trend we found that an anisotropic von karman correlation function with an aspect ratio around 4 and a hurst number of 0 3 corresponding to a fractal dimension of 2 7 matches the observed data our results represent an explicit confirmation of previous indirect evidence for the fractal nature of lithospheric heterogeneities and provide the means to construct realistic crustal scale seismic models of ivrea type lower continental crust

crustal structure of the southern alps beneath the intersection with the european geotraverse abstract newly digitized and amplitude controlled record sections from the 1977 southern alps refraction campaign permitted a reinterpretation of the crustal structure in the area between western lombardy and the giudicaria fault the resulting model exhibits considerable lateral heterogeneity in the west below 7 5 km of sediments of the lombardy basin the crust reaches a depth of only 31 km whereas it thickens towards the more mountainous area in the east reaching a depth of 46 km below the adamello massif although the signal character of the corresponding reflections is somewhat erratic the data are satisfied best by models with a low velocity zone in the upper crust an additional small velocity discontinuity from 6 2 to 6 4 km s was found in the middle crust at around 20 km earlier interpretations based on travel times alone included a layer with a velocity of about 7 km s at this depth this high velocity layer was then interpreted as lower crustal material of the adriatic african plate which had been overthrust onto the european plate during the alpine orogeny thus explaining the uplift of the southern alps however this model of crustal doubling is questionable because such a mid crustal high velocity layer is not in agreement with the amplitude data the relatively thin crystalline part of the crust under the lombardy basin is interpreted in accordance with geological evidence as a relic of a late hercynian rifting event

estimating original flake mass from 3d scans of platform area this study confirms the increased capacity to predict flake mass that arises from more accurately measuring surface area in three dimensions using a digital scanner we also reveal the existence of significantly different relationships between platform area and flake mass for flakes with different platform types and ventral and dorsal morphologies these different relationships between platform surface area and mass have not been previously identified and reveal the complexity of platform mass relationships using multivariate regression of 3d platform surface area and external platform angle we improve the accuracy of predictions of original flake mass we propose a method for studying reduction intensity on retouched flakes based on comparing predictions of the initial mass of the flake with measurements of the mass following retouching to estimate the amount of mass removed through retouching we name this approach the initial terminal mass comparison or itmc our experiments demonstrate that the capacity of the 3d platform scans to predict flake mass and by implication the capacity of the itmc to estimate mass loss rivals or exceeds the capacity demonstrated for existing reduction measures

lower crustal reflectivity patterns in wide angle seismic recordings many features of wide angle reflection data have been attributed to finely layered structure in the lower crust reflections with similar character however can be produced by small amplitude 2 d random velocity variations finite difference seismograms for a lower crustal model with isotropic random velocity variations match field data recorded at the black forest germany at source receiver offsets beyond about twice the target depth waves scattered from a random zone produce the appearance of horizontal layering in wide angle data lower crustal reflectivity patterns can thus be explained by models that have lateral and vertical random fluctutations rather than fine scale layering