lithic raw material units based on magnetic properties a blind test with armenian obsidian and application to the middle palaeolithic site of lusakert cave 1 classification of lithic artifacts raw materials based on macroscopic attributes e g color luster texture has been used to pull apart knapping episodes in palimpsest assemblages by attempting to identify artifacts produced through the reduction of an individual nodule these classes are termed raw material units rmus in the old world and minimum analytical nodules in the new world rmus are most readily defined for lithic artifacts in areas with distinctive cherts and other siliceous raw materials allowing pieces from different nodules to be recognized visually opportunities to apply rmus however are strongly limited at sites where lithic material visual diversity is low the magnetic properties of obsidian which result from the presence of microscopic iron oxide mineral grains vary spatially throughout a flow consequently obsidian from different portions of a source i e different outcrops or quarries can vary in magnetic properties this raises the possibility that magnetic based rmus mrmus for obsidian artifacts could be effective to distinguish individual scatters from multiple production episodes and offer insights into spatial patterning within a site or specific occupation periods first we assess the potential of mrmus using obsidian pebbles from gutansar volcano in armenia second we evaluate the validity of this approach based on a double blind test involving an experimental assemblage of gutansar obsidian flakes cluster analysis can successfully discern flakes from obsidian specimens containing high concentrations of iron oxides obsidian with more magnetic material has more opportunities for that material to vary in unique ways e g grain size morphology physical arrangement finally we apply the mrmu approach to obsidian artifacts from the middle palaeolithic site of lusakert cave 1 in armenia and compare the results to traditional rmu studies at contemporaneous sites in europe in particular we seek but do not find differences between retouch flakes which reflect rejuvenation of tools and the other small debris which reflect other reduction activities this result likely reflects the local landscape specifically the abundance of obsidian and thus little pressure to curate and retouch tools as this approach is applied to additional sites such findings will play a central role in regional assessments about the nature and timing of the middle to upper palaeolithic transition and the relationship or lack thereof between technological behaviors and presumed population dynamics

structure and emplacement of a rhyolitic obsidian flow little glass mountain medicine lake highland northern california many rhyolitic obsidian flows show consistent stratigraphic relations among textural units exposed in the flow fronts of undissected flows and in cross sections of older flows the stratigraphy of the holocene little glass mountain rhyolitic obsidian flow consists of from bottom to top air fall tephra deposits basal breccia coarsely vesicular pumice obsidian finely vesicular pumice and surface breccia slightly crystalline rhyolite occurs near the vent areas a model of obsidian flow emplacement based on these textural relations is presented this stratigraphy may reflect the distribution of volatiles within the magma source region with the interlayered contact between coarsely vesicular pumice and overlying obsidian indicating stratification of volatiles in the magma body the distribution of pumiceous and glassy zones along with the orientations of flow banding can be used to map the surface structure of rhyolitic obsidian flows this complex structure as mapped on the little glass mountain flow reflects both the initial flow stratigraphy and subsequent deformational processes during emplacement of the lava three processes disrupt the initial flow configuration the rise of coarse pumice diapirs from the base of the flow the inward propagation of fractures in areas of extension and surface folding in sites of flow parallel compression subvertical flow banding in vent areas indicates that fracturing accompanies the emergence of lava most of the observed upper surface of a dome originates as a fracture plane the structure of domes that form over vent areas may reflect the orientation of dike like conduits as well as the local state of stress during extrusion

sourcing geochemically identical obsidian multiscalar magnetic variations in the gutansar volcanic complex and implications for palaeolithic research in armenia abstract in obsidian rich armenia one of the most archaeologically significant obsidian resources is the gutansar volcanic complex gvc numerous palaeolithic sites across armenia consist of little more than deposits of obsidian tools and debris and within the hrazdan gorge the vast majority of artifacts is crafted from gvc obsidian for example about 93 of the lithic assemblages from the lower palaeolithic site of nor geghi 1 and the middle palaeolithic site of lusakert cave 1 are gvc obsidian although erupted from multiple volcanic centers gvc obsidians are geochemically identical and cover an area more than 70 km2 for studies seeking to reconstruct movements of palaeolithic hunter gatherers throughout the local landscape the expansive gvc is problematic geochemically identical obsidians dominate the foraging territories of sites within and near the complex here we explore the potential of obsidian magnetic properties to reveal hitherto unobservable patterns in gvc obsidian utilization with the ultimate goal of elucidating palaeolithic behavioral patterns our results show that magnetic properties vary over multiple scales within the gvc allowing obsidian sourcing to become multiscalar these measurements are rapid inexpensive and entirely nondestructive for small artifacts measuring a few basic magnetic properties enables us to distinguish geochemically identical obsidians from three eruptive centers and potentially to attribute artifacts to specific quarrying sites recognize changes in provisioning strategy and estimate a minimum number of cores represented by a lithic scatter

upper mantle structure along a profile from oslo noress to helsinki to leningrad based on explosion seismology abstract waveforms from the noress array were analyzed for 147 industrial explosions during the 1985 to 1988 period along a profile running east from oslo noress to helsinki to leningrad ohl profile the events were 250 to 1300 km from noress and had local magnitude in the range 2 0 to 3 5 event locations and origin times constrained by the university of helsinki9s regional seismic network provide a reliable basis for travel time estimation at noress we also used data recorded by norsar in 1979 for three shots on the fennolora north south long range seismic profile which were near the ohl profile analysis of mantle p wave signals from the explosions showed that first arrivals could be traced continuously to a distance of 750 to 800 km where there is a cutoff and shift of approximately 2 0 to 2 5 sec in the travel time curve and an increase in average apparent velocity interpretation of the observed travel times and waveforms for this profile suggests a low velocity zone from approximately 105 to 135 km depth combined analysis of the seismic data with a bouguer gravity map indicates the presence in the upper mantle of a high velocity high density body of linear extent approximately from 200 to 300 to 500 to 600 km east of the noress array it is postulated that this body may represent the root of an ancient volcanic system in which lighter silicic constituents were depleted from the upper mantle during the eruptive phase

deep structure of the european mediterranean area from seismological data abstract over the past 20 years the study of p and s wave velocities in the upper mantle of the european mediterranean area has been the subject of intensive research work we present a summary of results based on inversion of available surface wave dispersion data and p wave travel time observations in the european mediterranean area the correlation between the lithosphere and upper mantle structure obtained from the aforementioned analysis with other geophysical data is discussed

environment and collapse eastern anatolian obsidians at urkesh tell mozan syria and the third millennium mesopotamian urban crisis the early to middle bronze age transition in northern mesopotamia has received great attention for the apparent concurrence of aridification deurbanisation and the end of the akkadian empire around 2200 bce our understanding of the crisis has been almost exclusively shaped by ceramics demography and subsistence exchange and the associated social networks have been largely neglected here we report our sourcing results for 97 obsidian artefacts from urkesh a large urban settlement inhabited throughout the crisis before the crisis six obsidian sources located in eastern anatolia are represented among the artefacts such a diversity of eastern anatolian obsidians at one site is hitherto unknown in mesopotamia it implies urkesh was a cosmopolitan city with diverse visitors or visitors with diverse itineraries during this crisis however obsidians came from only two of the closest sources two to three centuries passed before varied obsidians reappeared even when an obsidian source reappears the raw material seems to have come from a different collection spot we discuss the likely exchange mechanisms and related social networks responsible for the arrival of obsidians at urkesh and how they might have changed in response to climatic perturbations and regional government collapse

paleointensities of phonolitic obsidian influence of emplacement rotations and devitrification 1 a paleomagnetic study on phonolitic obsidian from six sites in tenerife spain is presented two sites are located at the 750 ka el pasajiron at the southern wall of las canadas caldera four sites correspond to the 115 17 bce montana blanca complex paleointensity determinations are performed with a modified thellier technique using checks for alteration and domain state additionally the anisotropy of the thermoremanence and the magnetic cooling rate dependency of each specimen are measured it was not possible to obtain good quality paleointensity data for el pasajiron thermal alteration was observed in most measurements systematic changes in rock magnetic properties and paleointensities within the profile of one site also suggest the presence of a chemical remanence crm which was probably acquired during devitrifiction of the upper part of the flow this crm cannot be seen in the arai plots themselves but only by comparison of data from different samples this underlines the importance of sampling only fresh glassy looking obsidians and not devitrified ones paleointensity determinations at montana blanca are of very good quality leading to an high success rate of 82 samples at one site show acquisition of trm during emplacement rotations however it could be shown that paleointensity data of rotated samples are reliable if the remanence carriers are in the single domain range an atrm anisotropy tensor of thermoremanent magnetization and cooling rate corrected paleointensity of 48 4 2 1 t and a vdm of 9 64 0 42 1022am2 were determined which are in very good agreement with other data from spain and morocco and to various geomagnetic field models

high resolution body wave tomography beneath the svekalapko array ii anomalous upper mantle structure beneath the central baltic shield high resolution body wave tomography beneath the svekalapko array ii anomalous upper mantle structure beneath the central baltic shield

tomographic estimates of sub moho seismic velocities in fennoscandia and structural implications abstract pn and sn velocity estimates are derived for the sub moho structure beneath fennoscandia using a tomographic conjugate gradient scheme observational data stem from local earthquake recordings of crustal phases pg sg lg and the sub crustal phases pn and sn by the fennoscandian seismograph network unknowns are pn and sn velocities and event hypocenter parameters crustal thicknesses are assumed as known and are not estimated whereas velocities are allowed to vary the most prominent p and s velocity anomalies are found in the northwest inland lofoten and southwest more of norway and for shear waves also in central finland there is a good correlation between the velocity anomalies in norway and observed negative bouguer anomalies indicating the presence of low density sub moho material in these areas geologically the pn and sn velocity anomalies appear to be associated with geodynamic processes tied to the opening of the norwegian greenland sea

the east pacific rise near 21 n 13 n and 20 s inferences for along strike variability of axial processes of the mid ocean ridge abstract data obtained along various segments of the mid ocean ridge mor are used to construct an idealized model for crustal accretion the model seeks to predict the topographic volcanic tectonic and hydrothermal characteristics of any given spreading segment of the mor as a function of distance away from the bounding transform faults this model is based on a series of detailed mapping efforts carried out on segments of the mor having a broad range of spreading rates between 2 and 16 cm yr this paper includes the results of the french searise program carried out during the summer of 1980 aboard the n o jean charcot and two american cruises conducted in 1981 aboard the r v melville

complex lithospheric structure under the central baltic shield from surface wave tomography complex lithospheric structure under the central baltic shield from surface wave tomography

late collision rhyolitic volcanism in the north eastern part of the armenian highland abstract plio pleistocene acidic volcanism of the northeastern part of the armenian highland is related to a continental collision zone as a result of convergence between eurasia and arabia lithosphere plates the development of volcanism is divided into three stages of 10 17 4 5 7 5 and 0 1 2 8 ma a crustal origin model is proposed to explain the geochemical and petrogenetic aspects of the acidic volcanism formation spatially separated ba rich and rb rich geochemical types of rhyolites were revealed indicating more evolved and primitive rhyolitic magma types respectively the variation interval of the primary 87sr 86sr ratio was found to be from 0 70438 to 0 70636 age and lateral variation of geochemical and isotopic parameters were determined by differences of initial substrates and degrees of their partial melting the mechanisms of rhyolitic magma evolution were the remelting of heterogeneous sialitic materials and low pressure fractional crystallization in isolated magmatic chambers these facts confirm the model of crustal anatexis origin of the eutectic melts the eutectic rhyolitic magma was generated by an open system melting in the presence of deep horizon mobile k rb fluids initiated by mantle resources

the magnetic sourcing of obsidian samples from mediterranean and near eastern sources abstract the magnetic properties of obsidians are examined for their potential in sourcing obsidian artifacts the three simplest to determine magnetic parameters initial intensity of magnetization saturation magnetization and low field susceptibility are found to be effective discriminants of many mediterranean central european and near eastern sources although the between source precision is not as good as geochemical analyses of minor and rare earth elements the technique demonstrated the existence of new sources that were subsequently confirmed by minor element analyses unfortunately some key sources do not appear to be readily distinguishable on these three simple magnetic parameters alone although more sophisticated magnetic analyses may prove diagnostic despite this it would appear that effective discrimination can be made in many cases occasionally with more precision than minor element analyses this technique therefore offers as a minimum a preliminary sourcing tool for use in many areas of the world thus reducing the number of expensive geochemical analyses furthermore its very low cost non destructive nature and speed open the possibility of quantitative evaluation of trade routes based on obsidian distributions particularly as versions of the equipment are now suitable for use in the field

from flow to quarry magnetic properties of obsidian and changing the scale of archaeological sourcing abstract previous studies have endeavored to use petrophysical traits of obsidian particularly its magnetic properties as an alternative to conventional geochemical sourcing one of the greatest successes in archaeological science magnetic approaches however have not seen widespread application due to their mixed successes in a time when geochemical analyses can be conducted non destructively in the field and in a minute or two magnetic measurements of obsidian must offer novel archaeological insights to be worthwhile not merely act as a less successful version of geochemistry to this end we report the findings of our large scale study of obsidian magnetism which includes 734 geological obsidian specimens and 97 artifacts measured for six simple magnetic parameters based on our results we propose rather than using magnetic properties to source artifacts to a particular obsidian flow inter flow sourcing these properties are best used to differentiate quarrying sites within an individual flow intra flow sourcing our results also demonstrate that certain magnetic properties are highly affected by ancient knappers material selection criteria furthermore depending on the spatial scales of variation which likely vary from flow to flow we envision several potential applications of this approach including integration into minimum analytical nodule analysis mana magnetic data appear to shift the scale of obsidian sourcing from flows to quarries and in turn enable new insights into raw material procurement strategies group mobility lithic technology and the organization of space and production

heat flow and thermal structure of the lithosphere across the baltic shield and northern tornquist zone abstract terrestrial heat flow data from archean and proterozoic provinces of the baltic shield its southwestern margin and the tectonic transition to the younger tectonic units of central europe northern segment of the european geotraverse are compiled and examined for local and regional variations a 2 d numerical lithospheric temperature and heat flux model is presented covering 1800 km of the deep seismic fennolora profile across the baltic shield and 500 km of eugeno s northern eugemi seismic lines across the northern tornquist zone and the danish and north german basins thermal lithosphere defined as the outer layer with relatively low temperatures t c in which heat transfer is dominantly by conduction is found to vary markedly in thickness from 85 110 km beneath basins and tornquist zone to about 150 km in central shield areas and 200 250 km in areas of low heat flow along the northern shield profile these results are in very good agreement with seismological information from surface wave dispersion analysis and the refraction wide angle seismic interpretation of fennolora data the combined thermal and seismologic evidence indicates that the uppermost mantle region stratified in seismic velocity is restricted to the upper relatively cold thermal layer which is interpreted to constitute shield lithosphere local and to some extent regional variations in surface heat flow are found to be closely related to variations in near surface radiogenic heat production for the southern baltic shield a heat flow heat production relationship of q 0 32 8 7 6 h 0 is derived regional increase in heat flow from northern and central shield provinces to the shield margin and the tornquist zone is interpreted to be related partly to differences in upper crustal heat generation partly and in southernmost areas mainly to an increased heat flux from the upper mantle upper mantle heat flux is estimated at 20 25 mw m 2 along the northern and central shield transect increasing to 30 40 mw m 2 beneath the shield margin basins and tornquist zone lithospheric thickness variations in this region of northern europe are found to be closely associated with variations in heat flux from the uppermost mantle and perhaps to a large extent controlled by geodynamically determined lateral differences in upper mantle heat flux earthquake focal depth data and information on crustal strength show baltic shield seismicity to be limited generally to the upper 20 25 km brittle part of the crust at temperatures less than 300 400 c maximum source depth of magnetic anomalies at temperatures near 600 c is in the deepest part of the crust near the crust mantle boundary in the southern region about 25 km depth along the tornquist zone and about 35 40 km in southern shield areas and in the uppermost mantle 60 70 km depth in the northern shield areas some petrologic implications are discussed the present deep crust is supposed to be at lower temperature pressure conditions than at early stages of formation however also the present deepest parts of the shield crust 35 40 km are within the stability field of eclogites the general absence of significant gravity anomalies in areas of marked crustal thickness variations indicate high density eclogites to be present in significant amounts in the deep shield crust

on upper mantle seismic heterogeneities beneath fennoscandia abstract three dimensional seismic mapping of the upper mantle beneath fennoscandia baltic shield using an ach type of inversion technique in combination with p wave travel time residual observations from the local seismograph network gave the following results the central parts of the baltic shield are characterized by relatively high seismic velocities down to approximately 300 km those parts of the shield most affected by the caledonide orogeny exhibit relatively low velocities particularly in the uppermost 100 km depth interval the lower part of the upper mantle 300 600 km does not exhibit pronounced seismic velocity anomalies and in this respect is in contrast to results from similar studies in regions subjected to neotectonic processes like parts of central and southeastern europe the seismic anomaly pattern in the presumed thickened lithosphere is in quantitative agreement with similar ones derived from surface wave dispersion analysis and inversion of electrical measurements the general orientation of these anomalies coincides with that of the glacial uplift

a decade of progress in earth s internal properties and processes a major component of the inter union commission on geodynamics project labeled internal properties and processes included certain experimental and theoretical research in tectonophysics seismology geochemistry petrology volcanology and planetology this review focuses on a few research areas in which there have been surprises and reversals in particular attention is given to the attempts to quantify the thermal profile in the earth s interior and the material properties of the earth s interior

lithospheric studies based on holographic principles earth holography was applied to norwegian seismic array norsar earthquake p wave recordings simulation of the norsar sensor configuration indicates that a satisfactory reconstruction of the essential features of an embedded body is feasible with a depth resolution which seems to be better than that attained using more traditional time and amplitude inversion schemes the earth holography concept was tested using norsar recordings of three deep earthquakes at teleseismic distances the results indicate lithospheric heterogeneous bodies with a significant vertical extent the most pronounced scattering features of these inhomogeneities are located at depths around 100 148 and 212 km

long wavelength heterogeneities in the upper mantle as seen by satellites abstract modern satellite methods have made it possible to study the gravity field of the earth with methods that primarily give increased information of the lower harmonics in a spherical harmonic expansion for areas covered with water we have recently obtained very interesting results from the seasat satellite earlier studies of the gravity field have mainly resulted in geophysical evaluations for the very low degrees which mostly reflect information from the core and the lower mantle now available studies seem to give evidence for geophysical activities which originate from convection currents as well as glacio isostatic uplifts most of this information is probably generated in the upper mantle methods for mapping of the terrestrial gravity field with satellite technique are presented and some of the problems with the geophysical evaluation are further discussed

transport models for crust and mantle evolution the exact solutions for the isotopic compositions and the concentrations of two models for mantle crust evolution are given for arbitrary rates of crustal growth and of backflow to the mantle in model i continents are derived by melt extraction over the history of the earth from undepleted mantle in model ii new additions to the continents are derived from a mantle reservoir which becomes increasingly depleted through time by repeated extraction of melts the key parameters are the chemical fractionation factors for crustal growth and refluxing and the integrated fractional mass removal rates from the crust and the mantle the relationships between the mean age of the mass of the continents and the isotopic parameters are given the models suggest that the pre archean era prior to 3 8 ae was dominated by rapid refluxing of crust to the mantle which during the early archean gave way to a regime where transport from the mantle to the crust substantially dominated over refluxing of crust to the mantle the mean age of the mass of the continents appears to be 1 8 ae even for small amounts 10 of refluxing model ii shows that highly incompatible elements have very short residence times in the mantle mass balance considerations implies that the continents were derived from only a small fraction 30 of the mantle

delay time tomography of the upper mantle below europe the mediterranean and asia minor summary the method of linearized delay time tomography is applied to retrieve the p velocity heterogeneity of the upper mantle in central europe the mediterranean and asia minor the upper mantle is parametrized in slowness cell functions with lateral dimensions of 1 the model parametrization includes event mislocation vectors and station delay time corrections in all 20 000 parameters describe the model delay time data selected from the isc data base 1964 1982 from regional events and from stations up to 90 of epicentral distance are used about 18 000 events and 937 stations contributed nearly 500 000 delay times we discuss the tomographic method the data processing the cell model employed the computation of the ray geometry the use of composite rays in tomography and the cell hit count the inversions are performed with two different iterative row action methods lsqr and sirt results obtained with the lsqr method will be shown only the spatial resolution is investigated with sensitivity analyses using two different synthetic velocity models a spike model and a model with harmonically varying velocity anomalies the spatial resolution is estimated to be high on the order of the cell size in the mantle below central and southeastern europe the mapped velocity heterogeneity exhibits primarily low velocities around a depth of 200 km and just above the transition from upper to lower mantle this indicates a systematic deviation of the reference model jeffreys bullen from the radially averaged earth structure which may violate the basic assumptions underlying the linearized approach a posteriori investigation of the data also indicates the presence of a low velocity zone and the existence of strong velocity depth gradients

a seismic cross section through the east european continent summary a 2 d pro le for the shear wave velocity and anisotropybetween egypt and spitsbergen is presented the pro le is constructed using fundamental and higher mode love and rayleigh waves recorded by stations of the nars deep iris and geofon networks the surface wave data have been inverted for shear velocity and anisotropy using a waveform inversion in the eastern mediterranean lithosphere we observe a large diierence 7 per cent between sh and sv velocities we interpret this anomaly as an anisotropic oceanic lithosphere beneath the eastern mediterranean an interpretation which is consistent with tectonic reconstructions of the region the east european continent is imaged as a high velocity body whose thickness increases with the estimated age of the lithosphere the continental root of the ukrainian and baltic shields and east european platform extends to a depth of 200 km this is in contrast to the surrounding younger continental regions which appear to be less than 100 km thick we further studied the structure of the continental lithosphere by investigating a possible relation between seismic velocities and tectonic age both a logarithmic and a square root relation have been tted to the average seismic velocities in each tectonic region the data slightly favour a logarithmic relation but a square root relation cannot be excluded

the moho depth distribution in fennoscandia and the regional tectonic evolution from archean to permian times abstract from a variety of seismic refraction and reflection profiling results a new detailed moho depth map for the fennoscandian part of the baltic shield has been compiled a complementary crystalline crustal thickness map was compiled for denmark the skagerrak sea offshore western norway and adjacent areas where sedimentary strata reach maximum thicknesses of 10 km and even more these maps are discussed in relation to tectonic evolution and crustal ages of fennoscandia seismic velocities bouguer gravity and seismicity areas deviating from the proposed age thickness relationships are the kola peninsula archean and the oslo rift permian the average crustal thickness in the former area is around 44 km while the latter area is associated with a moho elevation of 3 5 km maximum crustal thicknesses in excess of 50 km have been found in southwestern and central finland and correlate with a crust of proterozoic age the caledonides of western norway do not exhibit as elsewhere a crustal root sub moho p n and s n seismic velocities are relatively small in that area and bouguer gravity values are strongly negative intracrustal p velocity variations do not seem to reflect geological age or specific tectonic features although the seismicity is moderate in fennoscandia most of the earthquake activity and in particular the largest earthquakes are confined to areas where the crustal thinning is most pronounced

observations of the electrical asthenosphere beneath scandinavia the recent recognition that long period i e of the order of hours electromagnetic induction studies could play a major role in the detection of the asthenosphere has led to much interest amongst the geophysical and geological communities of the geomagnetic response functions derived for differing tectonic environments experiments carried out on the ocean bottom have met with considerable success in delineating the electrical asthenosphere i e a local maximum in electrical conductivity minimum in electrical resistivity in the upper mantle in this paper observations of the time varying magnetic field recorded in three regions of scandinavia northern sweden kiruna kir northern finland northeastern norway kevo kev and southern finland sauvamaki sau are analysed in order to obtain estimates of the inductive response function c for each region the estimated response functions are compared with one from the centre of the east european platform eep and it is shown that the induced eddy currents at periods of the order of 103 104 s in the three regions flow much closer to the surface than under the platform centre specifically at a period of 3000 s these currents are flowing at depths of the order of kev 120 km kir 180 km sau 210 km eep 280 km implying that the transition to a conducting zone of 0 2 s m occurs at around these depths one dimensional inversion of ckev and ckir shows that there must exist a good conducting zone of 0 1 1 0 s m under each of the two regions of 40 km minimum thickness at depths of kev 105 115 km kir 160 185 km this is to be contrasted with eep where the d profile displays a monotonically decreasing resistivity with depth reaching 0 1 s m at 300 km finally a possible temperature range for the asthenosphere consistent with the deduced conducvitity is discussed it is shown that at present there is insufficient knowledge of the conditions water content melt fraction etc likely to prevail in the asthenosphere to narrow down the probable range of 900 1500 c

fragmented reduction processes middle palaeolithic technical behaviour in the abri du maras shelter southeastern france new excavations at the abri du maras located in the southeast of france have yielded middle palaeolithic assemblages with evidence of rock shelter occupations in a cold climatic context contemporaneous with mis 4 few mis 4 sites are known in this part of france and especially in this state of preservation the paper is focused on one sedimentological layer divided into two archaeological levels sub levels 4 1 and 4 2 our goal was to examine the middle palaeolithic lithic assemblage of these two levels by interdisciplinary approaches technology origin of flint and functional analysis of stone tools in order to identify the technical strategies and the land use patterns in a specific environmental context the two occupations do not show differences in behaviours the technical strategies applied to flint and other stones indicate a fragmentation of the reduction processes in a local and semi local perimeter around the site the main core technology is levallois generally on flint cortical cores on flakes flint flakes blades and points are the main components of the series and the technological aims of the debitage due to the small size of the flakes used for flaking large flint flakes blades levallois or cortical and levallois points were produced elsewhere to the north and south of the site up to 20 30 km according to the geological study and then brought to the shelter flakes in other lithic materials quartz quartzite were also knapped elsewhere before being transported to the shelter some of the large flint flakes but also nodules and fragments of slabs were then used for onsite flaking flake tools are very rare evidence of impact fractures and tcsa tcsps values of the corpus of unretouched levallois points suggest that some points brought or prepared on the site could have been used as projectile tips the lithics attest to management of local and semi local stones in a perimeter of 30 km around the site possibly more due to some unidentified flint and an anticipation of domestic needs in relation to reindeer hunting the predominant activity imported artefacts and artefacts made on the site were used for the same diversity of activities and materials butchery plant and woodworking the technological strategies and the type of management differ slightly from those from cave assemblages in the same area located in valleys and on low plateaux near the rhone corridor possibly due to the type of the site a vast shelter data from the abri du maras are compared to data from the other middle palaeolithic sites of the region and the role of the topographic aspect of the site on the type of occupations is discussed

three dimensional seismic structure beneath southwest japan the subducting philippine sea plate abstract a three dimensional seismic structure beneath southwest japan has been investigated in detail by applying an inversion method this analysis clearly reveals the present and possibly the past subduction of the philippine sea plate beneath southwest japan beneath the izu peninsula the philippine sea plate does not appear to subduct but collides against the continental asian plate here and its thickness appears thinnest at most about 30 km from the tokai to the shikoku regions the high velocity zone corresponds well to the zone of subcrustal earthquakes down to a depth of about 60 70 km indicating that the subduction of the present philippine sea plate does not reach below this depth here however a small high velocity portion appears at depths between 100 km and 150 km beneath a part of the kinki region and probably extends to the chugoku region where no corresponding seismic activities exist these high velocities might be an indication of the remnants of the past subduction of the philippine sea plate in the kyushu region the high velocity zone continues down to a depth of about 150 km or even to 200 km in the southern part corresponding to a steeply inclined seismic zone the philippine sea plate in this region appears to be thicker than in regions east of the kyushu palau ridge it was also found that there exist narrow low velocity zones intervening within the philippine sea plate where two aseismic ridges the kyushu palau and shichito iwojima ridges extend northwards and the nankai trough shows warping these low velocity zones give support to the buoyant subduction hypothesis it also appears that lateral heterogeneities existing within and around the subducting plate are closely related to the mode of rupture of large earthquakes occurring around there

magnetotelluric and audiomagnetotelluric measurements in finland abstract joint finnish hungarian mt magnetotelluric and amt audiomagnetotelluric measurements were carried out in finland in the framework of the international elas project the conditions for mt measurements are favorable at these latitudes five mt and 150 amt stations gave information on the electrical conductivity distribution in the area amt results guided the choice of mt sites with minimal near surface distortion effects and helped the interpretation of the mt soundings the mt measurements indicate the presence of large conductivity anomalies and can be best interpreted as lateral induction effects of near surface dyke structures this result is confirmed by a certain correspondence between the directions of the maximum impedances and of the tectonic zones of the area any information about the upper mantle would require the use of sq harmonics because of the crustal conductivity anomalies detected by the mt measurements

upper mantle heterogeneities beneath central europe summary an inversion of isc travel time data from selected earthquakes in the distance range 30 90 to 53 stations in central europe has been used to model velocity down to 600 km depth the model explains 0 1 0 2s of the residuals as for other array studies leaving 0 5 s unexplained as noise the uppermost 100 km of the mantle and crust contains inhomogeneities that correlate remarkably well with the geology this may be due to deep seated thermal anomalies or in some areas to delays introduced by passage of the rays through sedimentary cover the deeper anomalies are smaller and unrelated to those in the lithosphere which suggests that the asthenosphere is decoupled from the rigid lithosphere the structure at 600 km depth is again quite inhomogeneous and might be due to undulations of the 650 km discontinuity the models show some suggestion of a high velocity slab trending from east to west beneath the alps

volcanism and massive sulfide formation at a sedimented spreading center escanaba trough gorda ridge northeast pacific ocean seismic reflection profiles over the sediment filled escanaba trough at the southern gorda ridge reveal a series of volcanic centers that pierce the sediment the volcanic edifices are 3 to 6 km in diameter and are spaced at 15 to 20 km intervals along the axis of the trough the volcanic intrusions have uplifted the sediment as much as 100 m and in places fresh basaltic flows are exposed at the sea floor unoxidized pyrrhotite rich massive sulfide samples were obtained from the flanks of one of these volcanic centers the composition and form of the sulfide samples suggest significant interaction between hydrothermal fluids and sediment at depth and deposition of sulfide within the sediment pile

three dimensional seismic inhomogeneities in the lithosphere and asthenosphere evidence for decoupling in the lithosphere and flow in the asthenosphere newly discovered three dimensional seismic velocity anomalies in the earth s lithosphere and asthenosphere are interpreted in terms of decoupling in the lithosphere and flow in the asthenosphere a rough estimate of flow in the asthenosphere under california was made using stokes law on the basis of the size of anomalies and density contrast estimated from the velocity contrast the result depends on the cause of velocity anomalies if they are due to any effect which obeys birch s law the flow is as rapid as that of morgan s 1972 plume driving the plate motion on the other hand if they are due to partial melts in thin cracks or at grain boundaries the flow is negligible in accordance with elsasser s 1971 model of plate tectonics driven quietly by the ridge push and slab pull in which the asthenosphere under the base of the plate is only passively dragged the result of cockerham and ellsworth 1979 1980 that the low velocity zone in the mantle under central california appeared to have preserved the shape of the downgoing slab for up to 10 m y supports elsasser s rather than morgan s model the shapes of low velocity bodies found by iyer and his colleagues under several geothermal areas in the western united states may be interpreted in terms of decoupling between the upper brittle lithosphere and the ductile substratum the misalignment of the axis of the low velocity column from the center of the granite outcrop in the roosevelt hot springs area utah and the inclined low velocity column under the geysers clear lake region california indicate a decoupled lithosphere in these areas whereas the upright column found under yellowstone national park suggests an intact lithosphere there

large scale p velocity structures in the euro mediterranean area summary the 3 d velocity structure beneath the euro mediterranean domain is investigated down to 1200 km by using teleseismic p arrival times collected by the euro mediterranean seismological centre emsc in strasbourg the simultaneous iterative reconstruction technique sirt is used to invert the data while the direct problem is formulated by using a spherical block partition of the model space and an analytical ray tracing so that the whole ray path lies in the investigated 3 d model box only events located within epicentral distances of 30 70 are considered in this study after reviewing the sirt method a synthetic test has shown the reliability of the results for structures beneath the lithosphere while for shallower parts of the model and depths larger than 900 km limited reliability is achieved for the upper mantle the model shows clear correlations with major known surface tectonic features in particular a well marked sub vertical slab in the calabrian arc and the presence of a roughly north orientated slab in the aegean area at greater depths our model shows slow velocities around 600 km beneath the two main hercynian massifs in europe

heat flow measurements on a hydrothermally active slow spreading ridge the escanaba trough maximum heat flow measurements at three locations in the sediment filled escanaba trough of the gorda ridge exceed 1200 mw m at other ridge crests with thick sediment cover heat flow values of this magnitude are accompanied by high temperature hydrothermal vent activity and massive sulfide deposition a dredge haul from the southernmost high heat flow location recovered pyrrhotite thereby confirming the presence of recent high temperature venting

organic geothermometry of petroleum from escanaba trough offshore northern california abstract we have measured the extent of hopane and sterane isomerization and of monoaromatic steroid hydrocarbon aromatization in a sample of hydrothermally derived petroleum from the escanaba trough a sediment covered volcanically active ridge axis the results along with kinetic parameters predict the possible time temperature history of the petrolum forming process for this sample the extent of these reactions is consistent with petroleum formation by intense heating about 300 350 c if the time period of this heating was as short as about 100 yr such a time scale is reasonable for hydrothermal discharge events associated with ridge crest volcanism

oceanic ridge crest processes oceanic ridge crest processes constitute a vigorous frontier of multidisciplinary research with global ramifications in the earth atmospheric and biologic sciences this deep ocean frontier is gradually opening in response to investigations which are elucidating the role of these processes in the lithosphere hydrosphere atmosphere and biosphere and the application of advanced instrumental and interpretive techniques which are increasing the quality and quantity of data these techniques include crustal drilling with borehole logging deep sea drilling project reports high resolution bathymetry sea beam etc side scan sonar seamarc i and ii gloria etc imagery with video and photography multichannel seismics determination of water column properties ctd with rosette sampler etc and submersible applications

marine tectonics processes at mid ocean ridges the use of multibeam echo sounders and various side looking sonar systems has greatly increased our knowledge and understanding of mid ocean ridge mor processes since the last iugg review on mid ocean ridge research macdonald 1983 the extensive use of swath mapping tools such as sea beam deep tow seamarc i and ii the application of multichannel seismic reflection techniques to the detection of axial magma chambers and the use of satellite data in the study of oceanic lithosphere have rejuvenated marine tectonics and have generated and stimulated a large number of important contributions this review will focus on what we feel were the major developments in marine tectonics with an emphasis on mid ocean ridges in the last four years certain topics such as marine seismicity and satellite studies are only briefly mentionned for reference and will be covered in greater detail in other reviews because of the exponential growth in the number of publications related to mors during 1982 1986 only a few references pertinent to each of the major research topics will be quoted in the text as examples but the reader will find an extensive bibliography at the end of the text references published prior to 1982 were added only where appropriate

lateral heterogeneity of europe s upper mantle as inferred from modelling of broad band body waves summary the upper mantle velocity structure beneath europe is investigated by body wave modelling of broad band seismograms from earthquakes in the eastern mediterranean recorded by stations in north west europe the gross features of the p and s wave velocity distribution as inferred from the data show a high velocity lid a low velocity zone and two discontinuities at depths of approximately 420 and 650 km the seismograms also present evidence for lateral heterogeneity of at least a few per cent 2 5 per cent for p 4 per cent for s to a depth of approximately 400 km many of the inferred velocity variations can be related to the tectonic setting of the region between source and receiver broad band seismograms are essential for such detailed study of upper mantle structure using body wave modelling

asymmetric lithosphere as the cause of rifting and magmatism in the permo carboniferous oslo graben compared to other permo carboniferous rift basins of nw europe the oslo graben has two distinct characteristics first it initiated inside cold and stable precambrian lithosphere whereas most permo carboniferous basins developed in weaker phanerozoic lithosphere and second it is characterized by large volumes of magmatic rocks despite relatively little extension seismic reflection surveys show that the crust thickens from southern norway to southern sweden the most significant moho deepening occurring from the oslo region eastwards deep seismic studies also suggest that the base of the lithosphere deepens markedly eastwards from the oslo region such a long wavelength lithospberic geometry cannot be explained by the permian or post permian evolution of the area hence the oslo graben appears to have evolved at the transition between two lithospheric domains with contrasting thickness numerical thermo mechanical modelling is applied to test if this transitional position can influence the dynamics of rifting different models with varying lithosphere thickness contrast are considered model results show that a crust and lithosphere thickness contrast comparable to the oslo region can explain rifting and focusing of magmatism in a narrow zone with minor thinning of the crust models also account for the major characteristics of the oslo graben in terms of location and strain distributions in the crust the geological society of london 2004

the oslo graben gravity high and taphrogenesis abstract the paleo oslo rift oslo graben system is geophysically characterized by a pronounced gravity high a reinterpretation of gravity data in the region using a flexible inversion scheme indicates that the causative body has a density contrast of 0 06 g cm 3 the inversion results also suggest that this body is most likely located in the upper part of the lower crust and extends eastward well outside the graben area proper estimates of crustal thicknesses before and after the rifting aborted suggest that rifting commenced in the south and then progressed northwards the corresponding pole of rotation was located approximately 240 km nne of the city of oslo the hypocentres of 7 small local earthquakes were found to be located on the periphery of the anomalous body as derived from gravity modeling seismic investigations including 3 d imaging using norsar data have failed to provide conclusive evidence on intrusion of asthenospheric material in the lithosphere as part of the oslo graben taphrogenesis the explanation proposed here is that the geophysical imprints of oslo rift oslo graben evolutionary processes within the upper mantle have been considerably weakened over the associated time span of some 150 200 ma finally it is hypothesized that the asthenospheric injection into the lithosphere took place over a relatively small cross sectional area of the moho the further ascent of the gabbroic magma was partly hindered by the relatively rigid upper crust thus causing extensive lateral flow eastwards outside the oslo graben proper in the 10 20 km depth range

magnetite grain size analysis and sourcing of mediterranean obsidians abstract the potential of magnetic grain size variations as an obsidian source characteristic is investigated using geological and archaeological obsidians from five islands of the mediterranean sea lipari sardinia palmarola pantelleria melos four parameters are used magnetic and anhysteretic a susceptibilities saturation isothermal remanent magnetizations at room sirm 293 and liquid nitrogen sirm 77 temperature the ratio s t sirm 77 sirm 293 which depends on the superparamagnetic grains relative abundance varies little in each individual site with the exception of lipari which is characterized by large variations and the highest content of superparamagnetic grains the a vs plot king et al 1982 shows some within site dispersion of the samples but the ratio q a a which is strongly influenced by the single domain grains content is characteristic for each site the combined use of the king and q a vs s t plots discriminates the samples from most of the sites and suggests that the grain size analysis is a promising approach in sourcing obsidian archaeological artefacts moreover the measurements of the four parameters used are simple quick and feasible with no or little damage to archaeological finds

upper mantle heterogeneities beneath eastern europe abstract p wave travel time residuals for seismograph stations in eastern europe as reported by isc for the years 1964 1977 were used for constructing a seismic image of upper mantle heterogeneities in the network region for the depth range 0 100 km dominant tectonic features like the pannonian basin and the aegean sea and western turkey correlate well with pronounced velocity lows which a ppear to extenddown to a 300 km depth the velocity anomaly patterns in the depth intervals 300 500 km and 500 600 km are broadly similar but quite different from those of shallower depths the observed seismic heterogeneities are briefly discussed in terms of large scale tectonic and geophysical heat flow characteristics of eastern europe

the lithosphere asthenosphere system in fennoscandia abstract we present a summary of the available information on rayleigh wave dispersion data for the fennoscandian region the observations have been combined to produce regional dispersion relations which have then been subjected to the hedgehog inversion procedure the results are presented on a map outlining the thickness of the lid and the shear velocities in both the lid and the asthenosphere channel lid thickness up to around 135 km is found in the bothnia north central finland area with if any weak shear velocity contrast to the underlying layer the surrounding areas are characterized by lid thickness up to around 75 km a stronger low velocity zone to lid contrast may be found in the caledonian and baltic sea area 0 25 0 45 km s taking into account moho depth data and the aforementioned results a map of the lithosphere asthenosphere system was derived

structure of the scandes lithosphere from surface to depth abstract in this review we give an overview of geophysical data and models available for the scandinavian mountains and adjacent areas as they are of relevance to the debate about the existence and cause of neogene uplift emphasis is given to potential field and petrophysical data of which the earth science communities of norway and sweden have a long tradition of acquisition and interpretation this is reflected in the wealth and dense coverage of data available the topography of the scandes mountain chain correlates to a large degree with a bouguer gravity low which suggests isostatic compensation but comparison with magnetic and petrophysical data shows that the gravity low is partly influenced by the trans scandinavian igneous belt signals due to the effects of surface geology can be further eliminated by considering the near surface density distribution as provided by petrophysical sampling to illuminate the entire lithospheric structure active and passive seismic and magnetotelluric data can be used recent and ongoing experiments are aimed at improving the existing models of the lithosphere integration of these different geophysical data sets allows the structure of the lithosphere of the scandes and its surroundings to be addressed seismic models show no pronounced crustal root below the scandes which could provide isostatic compensation but instead an increase of crustal thickness towards the central fennoscandian shield from the integrated model isostatic compensation is inferred to be largely controlled by the density distribution of the crust and that a high density lower crust to the east of the scandes is necessary to achieve isostatic equilibrium on a regional scale we demonstrate the typical crustal structure with profiles crossing from the scandes into the shield and a combined onshore offshore basement map

sharp contrast in lithospheric structure across the sorgenfrei tornquist zone as inferred by rayleigh wave analysis of tor1 project data abstract this work is a part of the tor1 project 1996 1997 and is devoted to determining the lithospheric structure across the sorgenfrei tornquist zone in northern europe for the first time in europe a very dense seismic broadband array has offered the possibility of determining very sharp lateral variations in the structure of the lithosphere at small scales using surface wave analysis we measure phase velocities for rayleigh waves with periods ranging between 10 and 100 s both within arrays with apertures of 40 50 km small compared to the wavelength and along long profiles of at least 100 km dispersion curves are then inverted and shear wave velocity models down to the depth of 200 km are proposed we show that the sorgenfrei tornquist zone is a major tectonic feature within the whole lithosphere north east of this feature in sweden beneath the baltic shield no lithosphere asthenosphere boundary is observed to exist to depths of 200 km south west of the sorgenfrei tornquist zone beneath denmark we find a lithospheric thickness of 120 20 km the transition across the sorgenfrei tornquist zone is sharp and determined to be very steeply dipping to the south west we also demonstrate the existence of a sharp discontinuity between the lithospheres beneath denmark 120 20 km thick and beneath germany characterized by thicknesses of 50 10 km in the northernmost part and 100 20 km in the southwest this discontinuity is most likely related to the trans european fault at the surface

hotspots basalts and the evolution of the mantle the trace element concentration patterns of continental and ocean island basalts and of mid ocean ridge basalts are complementary the relative sizes of the source regions for these fundamentally different basalt types can be estimated from the trace element enrichment depletion patterns their combined volume occupies most of the mantle above the 670 kilometer discontinuity the source regions separated as a result of early mantle differentiation and crystal fractionation from the resulting melt the mid ocean ridge basalts source evolved from an eclogite cumulate that lost its late stage enriched fluids at various times to the shallower mantle and continental crust the mid ocean ridge basalts source is rich in garnet and clinopyroxene whereas the continental and ocean island basalt source is a garnet peridotite that has experienced secondary enrichment these relationships are consistent with the evolution of a terrestrial magma ocean

tomographical mapping of the lithosphere and asthenosphere beneath southern scandinavia and adjacent areas abstract in this paper we report on a seismic tomographical survey of the lithosphere asthenosphere beneath southern scandinavia and adjacent areas the ach inversion technique has been used and the observational data in the form of p wave travel time residuals have been obtained from seismogram records from networks in denmark southern norway and southern sweden the volume under investigation subdivided into four levels layers of 7 7 knots blocks each for estimation of velocity perturbations covers the area 54 62 n and 7 20 e and depth range 0 600 km major findings are as follows level 1 0 100 km pronounced velocity lows beneath southern jutland zealand the variscan foredeep and the sveco norwegian province of southeastern norway 1500 ma old the svecofennides of southeastern sweden exhibit relatively high velocities while the sveco norwegian province of southwestern sweden 1700 ma old is characterized by moderately high velocities the transition between velocity highs and lows coincides with the tornquist teisseyre line ttl or fennoscundian border zone level 2 100 300 km velocity anomalies are less pronounced at this level although velocity lows are found beneath the northern jutland zealand area and slightly northwestwards of the oslo rift the only velocity high is found beneath the southeasternmost part of sweden the ttl does not appear to have a clear counterpart in the velocity anomaly pattern in this depth range although a clearly unambiguous answer here would require far more extensive observational data a research goal of the future level 3 300 500 km and level 4 500 600 km velocity anomalies are weak which is not unexpected for the upper mantle beneath shield areas