accelerator mass spectrometry radiocarbon dating of rock varnish accelerator mass spectrometry ams 14c dating off rock varnish provides minimum limiting ages for landforms and archaeological artifacts in arid and semiarid lands that are undatable by conventional radiocarbon methods experiments on sample collection the effect of different individuals preparing samples the influence of different chemical extraction procedures the incorporation of carbonate detritus possible contamination from rock underlying varnish the role of bio geochemical erosion of varnish and other influences reveal procedures that yield reproducible results conventional radiocarbon dates from charcoal beneath lava flows of hualalai volcano hawaii and from arid sites in western north america provide controls to test varnish radiocarbon dating ams radio carbon ages on the very bottom layer of varnishes are typically 10 younger than the 14c ages of these controls applications are illustrated here for fluvial aeolian peri glacial hillslope lacustrine and glacial geo morphology as well as rock art research in archaeology

shear velocity structure in the aegean area obtained by inversion of rayleigh waves summary the purpose of this work is to derive a 3 d tomographic image of the shear wave velocity structure of the crust uppermost mantle in the aegean area using the group velocities of rayleigh wave fundamental mode the database consists of 185 regional earthquakes recorded at broad band stations that were installed for a period of 6 month in the aegean area within the framework of a large scale experiment in a previous work karagianni et al 2002 an averaged group velocity has been determined using the method of frequency time analysis ftan for each epicentre station ray path and the data were used in order to determine the local group velocities for different periods over the area covered by the seismic ray paths taking into account additional resolution results obtained for the local group velocities a grid of 0 5 was adopted for the aegean area and a local dispersion curve was defined for each gridpoint more than 80 local dispersion curves were finally inverted using a non linear inversion approach deriving the corresponding 1 d shear velocity models the interpolation of these models resulted in a 3 d s wave tomographic image of the crust and uppermost mantle in the broader aegean area as expected as a result of the complex tectonic setting of the aegean area strong lateral variations of the s wave velocities of the crust and uppermost mantle of the studied area are found in the southern aegean sea as well as in a large part of the central aegean sea a thin crust of approximately 20 22 km is observed whereas the remaining aegean sea area exhibits a crustal thickness less than 28 30 km on the contrary a crustal thickness of 40 46 km is observed in western greece along the hellenides mountain range whereas in the eastern continental greece the crust has a typical thickness of approximately 30 34 km for shallow depths 10 km low s wave velocities are observed under the sedimentary basins of the north aegean sea the gulf of thermaikos axios basin and western greece at depths ranging from 10 to 20 km low s wave velocities are mainly found in western greece under peloponnesus as well as in rhodes this low velocity zone seems to extend along the hellenic arc and can be correlated to the hellenides mountain range and the alpine orogenesis in agreement with previous p wave tomographic results in the southern aegean sea very low s wave velocities 3 6 4 0 km s 1 are observed at depths of approximately 30 40 km just below the moho discontinuity while in the rest of the inner aegean sea and continental greece the uppermost mantle is characterized by velocities around 4 3 4 4 km s 1 this low velocity zone in the southern aegean sea can be associated with the high temperatures and the presence of significant percentage partial melt in the mantle wedge of the southern aegean subduction zone in agreement with previous studies

geological characterization of remote field sites using visible and infrared spectroscopy results from the 1999 marsokhod field test upcoming mars surveyor lander missions will include extensive spectroscopic capabilities designed to improve interpretations of the mineralogy and geology of landing sites on mars the 1999 marsokhod field experiment mfe was a mars rover simulation designed in part to investigate the utility of visible near infrared and thermal infrared field spectrometers to contribute to the remote geological exploration of a mars analog field site in the california mojave desert the experiment simultaneously investigated the abilities of an off site science team to effectively analyze and acquire useful imaging and spectroscopic data and to communicate efficiently with rover engineers and an on site field team to provide meaningful input to rover operations and traverse planning experiences gained during the mfe regarding effective communication between different mission operation teams will be useful to upcoming mars mission teams field spectra acquired during the mfe mission exhibited features interpreted at the time as indicative of carbonates both dolomitic and calcitic mafic rocks and associated weathering products and silicic rocks with desert varnish like coatings the visible near infrared spectra also suggested the presence of organic compounds including chlorophyll in one rock postmission laboratory petrologic and spectral analyses of returned samples confirmed that all rocks identified as carbonates using field measurements alone were calc silicates and that chlorophyll associated with endolithic organisms was present in the one rock for which it was predicted rocks classified from field spectra as silicics and weathered mafics were recognized in the laboratory as metamorphosed monzonites and diorite schists this discrepancy was likely due to rock coatings sampled by the field spectrometers compared to fresh rock interiors analyzed petrographically in addition to somewhat different surfaces analyzed by laboratory thermal spectroscopy compared to field spectra

shear wave velocity structure of africa from rayleigh wave analysis the 3d s velocity structure beneath africa is shown by means of a 2d s velocity mapping for depths raging from zero to 500 km determined by the regionalization and inversion of rayleigh wave dispersion the traces of 94 earthquakes occurred from 1990 to 2009 in the study area have been used to obtain the rayleigh wave dispersion these earthquakes were registered by 61 seismic stations located on africa and the surrounding area the dispersion curves were obtained for periods between 5 and 300 s by digital filtering with a combination of mft and tvf filtering techniques after that all seismic events and some stations were grouped to obtain a dispersion curve for each source station path these dispersion curves were regionalized and after inverted according to generalized inversion theory to obtain shear wave velocity models for rectangular blocks with a size of 5 5 the 3d s velocity structure obtained through this procedure is shown in the 2d s velocity maps plotted for several depths these results agree well with the geology and other geophysical results previously obtained the obtained s velocity models suggest the existence of lateral and vertical heterogeneity the zones with consolidated and old structures as cratons present greater s velocity values than the other younger zones nevertheless in the depth range from 20 to 40 km the different moho depths present in the study area generate the principal variation of s velocity a similar behaviour is found for the depth range from 60 to 230 km in which the lithosphere asthenosphere boundary generates the principal variations of s velocity finally it should be highlighted a new and interesting feature obtained in this study the definition of the base of the asthenosphere for depths ranging from 160 to 280 km in the whole african continent

analysis of folding and deformation within layered evaporites in blocks bm s 8 9 santos basin brazil the sao paulo plateau in the deepwater santos basin is the site of numerous recent pre salt petroleum discoveries the area is characterized by a thick sequence of layered evaporites comprising primarily halite with subordinate anhydrite and carnalite and trace amounts of other minerals the sequence is divided into six stratigraphic packages three relatively competent beams containing the bulk of the stronger anhydrite and three relatively weak detachment layers observed structural styles range from the simple to the complex including upright open folds inclined thrusted folds recumbent isoclinal folds sheath folds and superposed folds mul tiple detachments lead to polyharmonic folding disharmonic folding and overtightened folds major anticlinal structures contain acoustically transparent material surrounding disrupted highly deformed pieces of the lower two beams the deformation is non coaxial with anticlines forming a polygonal pattern and fold hinges that are highly curvilinear the sao paulo plateau is a contractional province that formed in response to proximal extension at the albian gap during convergent gravity gliding spreading of the margin shortening possibly began during the waning stages of evaporite deposition but the bulk of the movement occurred during the santonian mid eocene the evaporite sequence shortened much more than the cover because of extreme updip attenuation and consequent basinwards flow beneath the cover deeper levels of evaporite exhibit more shortening due to strain partitioning across internal detachments

dynamic restoration of profiles across diapiric salt structures numerical approach and its applications abstract the backstripping method that is widely used in basin analysis sometimes fails for salt bearing basins because the highly mobile and buoyant salt deforms its sedimentary overburden we present a numerical approach for 2 d dynamic restoration of cross sections through successive earlier depositional stages the approach is based on a solution of the inverse problem of the gravitational rayleigh taylor instability and combines the galerkin spline finite element method with interface tracking and a backstripping method our model interprets basin profiles as multiple layers of viscous fluids with various densities and viscosities the evolution of salt structures is modelled backward in time by removing successively younger layers and restoring older layers and any diapirs to the stage they were likely to have been we test the sensitivity of the restoration technique to small variations in density of the layers at different stages in the evolution of diapiric structures the applicability of the technique was demonstrated by reconstructions of upbuilt and downbuilt diapirs the technique is used to restore a depth converted seismic cross section through the south eastern part of the pricaspian salt basin mature salt diapirs in the section are shown to have been downbuilt from a salt layer with an initially uniform thickness as a result of differential sedimentary loading until the end of the triassic before one of the diapirs was buried and actively upbuilt the numerical approach is well suited for restoration of cross sections with ductile overburdens but despite limitations can be developed to 3 d restorations and other rheologies

constraints on absolute s velocities beneath the aegean sea from surface wave analysis summary the 3 d structure of the lithosphere beneath the aegean sea is investigated through surface wave dispersion analysis rayleigh and love waves recorded by 12 broad band stations installed for a duration of 6 months in the aegean region are processed through array analysis and wiener filtering data from three geofon stations in the area of crete were also used the resulting two station phase velocities are used to determine lateral variations of rayleigh wave phase velocities between periods of 20 and 100 s by a 2 d ray tomography method the obtained phase velocities are inverted to calculate variation of s wave velocity with depth using a combination of linearized inversion and a monte carlo based non linear inversion the absolute s wave velocity is resolved to a depth of approximately 200 km a highvelocity anomaly of 3 per cent is observed in the southern aegean attributed to the hellenic subduction in the northern part of the aegean in the prolongation of the north anatolian fault which is influenced by strong extensional movements we found low absolute s wave velocities at 50 100 km depth this supports a model of a distributed deformation of the upper mantle in the area separate rayleigh and love wave phase velocity inversions along common profiles reveal a strong love rayleigh discrepancy in the northern aegean down to at least 150 km depth i e most probably including the top of the asthenosphere

seismotectonics and the earthquake frequency magnitude distribution in the aegean area summary a study of aegean seismotectonics and the resulting frequency magnitude distribution on a broad scale is undertaken using the tectonic model of le pichon angelier this implies a tectonic moment release rate due to the spreading of the aegean of 17 8 times 1018 n m 1 yr 1 over the past 13 ma if stretching is due mainly to a series of normal faults dipping at about 45 in a seismogenic crust 10 20 km deep the moment magnitude relation from an instrumental magnitude catalogue is log m0 a bm with a 10 970 0 294 b 1 206 in si units this is established from 50 events of magnitude ms 5 3 whose scalar seismic moments m0 have been evaluated in a homogeneous manner for the region by spectral analysis of surface waves at 30 60 s period by contrast published body wave analyses from waveform modelling at 20 s period and moment tensor analyses seem to produce seismic moments which are lower by a factor of two or so on average this moment magnitude relation implies a seismogenic moment release rate due to stretching in the aegean of 14 times 1018 n m 1 yr 1 during the time period 1918 81 and 17 times 1018 n m 1 yr 1 for the period 1964 81 within a factor of two or so uncertainty this implies that the energy release in the brittle crust due to aegean spreading is substantially seismic within the stated accuracy and is also relatively stationary even when compared with the tectonic moment release rates a similar comparison using the same tectonic model shows that the subducting slab is sinking beneath the hellenic arc almost completely aseismically and that processes such as near vertical slab pull and confined thermal expansion could explain most of the observed seismic energy release by internal deformation of the slab the frequency magnitude statistics for the area of active extension has a characteristic earthquake of magnitude 7ms corresponding approximately to fault depths of 10 14 km for an aspect ratio of 2 and a strain drop of 10 4 this is close to the observed seismogenic depth 10 20 km for well determined earthquakes in the aegean area

varnish sediment and rock controls on spectral reflectance of outcrops in arid regions field observations in the meatiq dome eastern desert egypt show that amphibolite weathers to form massive outcrops and dense desert pavements that are extensively varnished laboratory based reflectance spectra of representative samples covering 5 cm 2 and spectra extracted from landsat thematic mapper data covering 2 25 x 10 4 m 2 confirm that varnish dominates the reflectance properties of amphibolite outcrops field laboratory and landsat data indicate that granite gneiss weathers to expose mainly bare rock whereas granitic out crops evolve to a mix of rock and locally generated sediment penetrative foliation in quartz phyllonite leads to production of slab shaped clasts that cover the surface the data show that mass wasting of the slabs results in a mix of rock varnish and sediment exposures outcrop reflectance properties for arid regions are thus dependent on both rock mineralogy and texture because both parameters modulate bedrock weathering and erosion

multispectral remote sensing as stratigraphic and structural tool wind river basin and big horn basin areas wyoming stratigraphic and structural analyses of the wind river basin and big horn basin areas of central wyoming are in progress one result has been the development of an approach to stratigraphic and structural analysis that uses photogeologic and spectral interpretation of multispectral image data to characterize the attitude thickness and lithology of strata new multispectral systems that have only been available since 1982 are used with topographic data to map upper paleozoic and mesozoic strata exposed on the southern margin of the bighorn mountains landsat acquired thematic mapper tm data together with topographic data are used to map lithologic contacts measure dip and strike and develop a stratigraphic column that is correlated with conventional surface and subsurface sections aircraft acquired airborne imaging spectrometer ais and thermal infrared multispectral scanner tims data add mineralogic information to the tm column including the stratigraphic distribution of quartz calcite dolomite smectite and gypsum results illustrate an approach that has general applicability in other geologic investigations that could benefit from remotely acquired information about areal variations in attitude sequence thickness and lithology of strata exposed at the earth s surface application of our methods elsewhere is limited primarily by availability of multispectral and topographic data and quality of bedrock exposures

thermal infrared analysis of weathered granitic rock compositions in the sacaton mountains arizona implications for petrologic classifications from thermal infrared remote sensing data 1 critical to spectral interpretations of geologic surfaces on the earth and mars is an understanding of the relationship between the composition of weathered rock surfaces and whole rock mineralogy in this study thermal infrared spectroscopic and remote sensing analyses were used to determine the composition of weathered granitoid rock surfaces in the sacaton mountains arizona a linear spectral deconvolution approach was employed to determine the mineralogies of naturally exposed weathered surfaces and artificially exposed fresh rock surfaces deconvolution results from fresh rock surfaces yield similar bulk mineralogy to results from point counting of rock slabs and thin sections deconvolution of weathered rock spectra indicate that compared to fresh samples weathered surfaces are deficient in plagioclase feldspar and are enriched in clay minerals the differential weathering of feldspar minerals impacts the interpretation of whole rock mineralogy and the spectral classification of bedrock geology which for plutonic rocks is dependent on the relative proportions of different feldspars deconvolutions of multispectral remote sensing or laboratory data show a deficiency of total feldspar in the weathered rock units but lack sufficient spectral resolution for the discrimination between different feldspars these results demonstrate that the differential breakdown and removal of primary minerals in rock surfaces due to weathering can affect the interpreted rock petrology from remote sensing studies the relationships observed in our granitic samples could be applied to any rock type and may be important to consider for remote sensing of mars

seismicity in the hellenic volcanic arc relation between seismic parameters and the geophysical fields in the region summary a study of the spatial distribution of seismicity and seismic hazard and geophysical parameters is undertaken along the hellenic volcanic arc hva seismicity of the area is divided in a cellular manner allowing analysis of the localized seismicity parameters and representation of their regional variation as contour maps extreme value analysis locates a zone of highest seismicity just west of centre of the hva around the cyclades islands non probabilistic modelling of the strain energy release process in terms of magnitudes equivalent to the average annual energy release rate m and the maximum possible energy release in a seismic cycle m3 enhances this picture maximum values of m and m3 are more tightly localized in the central cyclades west of amorgos island and also in the east of the hva in the sporadhes north west of rhodes isocyclic contours of the waiting times for m3 show values in excess of 70 years in the cyclades and eastern sporadhes i e the zones of largest earthquakes show the longest strain accumulation periods the waiting time for the hva as a whole is about 54 years and at present it appears to be about 75 per cent through to accumulation of the notional maximum strain energy the b value of the magnitude frequency distribution shows a consistent spatial variation along the hva which is not sensitive to subdivision into different focal depth ranges regional contour maps of the b values and maps of local values of heat flow magnetic and electrical anomalies compared with the bouguer gravity anomaly map indicate correlations which reflect the deformation of the aegean shallow crust in relation to the deep intrusive magmatic processes the correlations between the different geophysical fields are displaced commensurate with an aegean extension of approximately 45 km

objective regionalization of rayleigh wave dispersion data by clustering algorithms an application to the mediterranean basin abstract the main target of the present study is an objective and automated regionalization of rayleigh wave dispersion data for the mediterranean basin without a priori seismotectonic constraints and to determine the corresponding regional shear velocity structures the database used is formed by almost 200 rayleigh wavetrains corresponding to 42 regional events with surface wave magnitude greater than 4 5 recorded at the mednet very broad band stations in the mediterranean area path averaged group velocities for the rayleigh wave fundamental mode are derived for each available epicentre station trajectory crossing the mediterranean basin after this a principal component analysis and a clustering process are applied to local group velocities obtained for 13 different periods from 10 to 70 s in order to classify the mediterranean basin into several homogeneous regions the stochastic inversion of the averaged group velocity dispersion curve obtained for each region provides the respective shear velocity structures down to a depth of 150 160 km the characteristics of these areas and their possible correlation with the main seismotectonic features of the mediterranean region are discussed the regional models reveal significant lateral changes in the elastic structure with the main differences concerning particularly the upper 35 40 km within this depth range low shear velocities varying from 2 8 to 3 9 km s 1 characterize the eastern mediterranean whereas higher velocities ranging from 3 0 to 4 2 km s 1 are deduced for the western mediterranean these results suggest a thicker crust in the eastern part but with a greater thickness of sedimentary layers however for depths of between 80 and 110 km lower shear velocities are obtained in the western part while higher shear velocities are derived for the eastern mediterranean sea in the aegean sea greece the south of italy sicily and tunisia this velocity pattern suggests an averaged thicker lithosphere under the latter areas as the top of the asthenosphere is detected at a mean depth of 75 km for the remaining regions this thicker lithosphere can be related to processes associated with the convergence of the eurasian and african plates and subduction under the calabrian and hellenic arcs

the aegean region deep structures and seismological properties summary 3 d p wave velocity anomaly patterns the geometry of the hellenic wadatibenioff zone and of the seismically active fracture zones in the overlying continental wedge and the depth distribution of seismogenic properties seismic activity energy and b value for the aegean region are examined in this study the western and eastern parts of the area studied differ significantly in terms of the depth distribution of the considered seismological parameters and the velocity structures the results indicate different physical conditions in the western and eastern parts of the region in question data for the surface heat flow and the evolution of the volcanism in the aegean region since the early eocene are employed to interpret the results of the present study possible geodynamic processes at the plate boundaries between africa and eurasia are discussed

the influence of different rheological parameters on the surface deformation and stress field of the aegean anatolian region the aegean anatolian region is characterised by an inhomogeneous deformation pattern with high strain rates and a high seismicity both at the boundaries and in the plate interior this pattern is controlled by the geometry and rheology of the structural units involved and their tectonic setting a numerical analysis with a finite element model of the region is used to quantify the influence of different rheological parameters viscoelastic material behaviour is implemented for the mantle lithosphere whereas the crust is modelled with an elastic plastic rheology the variation of the inelastic material properties viscosity and plastic strength quantifies the influence of these material parameters on the deformation stress and strain patterns comparison of the modelled results with geodetic and geophysical observations reveals that the viscosity of the mantle lithosphere is the key to explaining the inhomogeneous deformation pattern the best fit model yields a viscosity of 1020 pa s beneath anatolia whereas adjacent regions have viscosities between 1021 and 1023 pa s the model also explains the intra plate seismicity and the stress field as well as its partitioning into regions with strike slip and normal faulting the final model is in good agreement with seismological geodetic and geological observations local deviations can be tracked down to small scale structures which are not included in the model

dust coatings on basaltic rocks and implications for thermal infrared spectroscopy of mars 1 thin coatings of atmospherically deposited dust can mask the spectral characteristics of underlying surfaces on mars from the visible to thermal infrared wavelengths making identification of substrate and coating mineralogy difficult from lander and orbiter spectrometer data to study the spectral effects of dust coatings we acquired thermal emission and hemispherical reflectance spectra 5 25 m 2000 400 cm 1 of basaltic andesite coated with different thicknesses of air fall deposited palagonitic soils fine grained ceramic clay powders and terrestrial loess the results show that thin coatings 10 20 m reduce the spectral contrast of the rock substrate substantially consistent with previous work this contrast reduction continues linearly with increasing coating thickness until a saturation thickness is reached after which little further change is observed the saturation thickness of the spectrally flat palagonite coatings is 100 120 m whereas that for coatings with higher spectral contrast is only 50 75 m spectral differences among coated and uncoated samples correlate with measured coating thicknesses in a quadratic manner whereas correlations with estimated surface area coverage are better fit by linear functions linear mixture modeling of coated samples using the rock substrate and coating materials as end members is also consistent with their measured coating thicknesses and areal coverage a comparison of ratios of thermal emission spectrometer tes spectra of dark and bright intracrater and windstreak deposits associated with radau crater suggests that the dark windstreak material may be coated with as much as 90 areal coverage of palagonitic dust the data presented here also will help improve interpretations of upcoming mini tes and thermal emission imaging system themis observations of coated mars surface materials

pre mesozoic geodynamics of the precaspian basin kazakhstan abstract this paper concentrates on the pre mesozoic history of the precaspian basin representing more than half of the 20 km of its sedimentary thickness we present the evolution of sediments deposited in the basin through time by several regional sections of the basin these image from the devonian the creation and evolution of a deep intercontinental basin which existed from carboniferous to permian palinspastic reconstructions show also the evolution of the basin s margins their relations with the southern pre uralian foredeep in the east and carbonate build ups in the southeast we present a reconstruction for the early history of the precaspian basin which became an individual basin only at the end of the permian as a result of the uralian orogeny the basement of the central precaspian depression is characterised by a thin crust where a low velocity layer is absent a layer of abnormally high velocities exists below the crust which on the basis of structural and gravitational field data is interpreted as eclogite we put forward a scenario for the age and emplacement of eclogite lenses at the base of the crust they are possibly implemented in the hangingwall from a westward subduction zone existing during the vendian before the collision giving birth to the proto urals most of the basin subsidence is due to the thinning mainly during devonian and increase of the average density of the crust present crustal density has characteristics of intermediate to lower crust interpreted by some authors as oceanic we propose that the loading effect of the eclogites emplacement may explain also a part of the precaspian basin subsidence

primary basins and their boundaries in the deep water northern gulf of mexico origin trap types and petroleum system implications primary basins form stratigraphically continuous successions on autochthonous salt and therefore in the northern gulf of mexico contain all the components of a petroleum system source reservoir trap and seal most primary basins are encased entirely in salt or in some combination of salt and welds petroleum exploration in the deep water gulf of mexico is currently focused on primary basin targets and increasingly those at their lateral boundaries however as these boundaries are commonly poorly imaged robust structural models are critical to interpretation of their structural evolution and relative petroleum system risk using three dimensional seismic data we define three tectonostratigraphic provinces that characterize primary basin depocenters 1 a disconnected salt stock canopy province in mississippi canyon 2 an amalgamated salt stock canopy province in northern atwater valley southeastern green canyon walker ridge and southern keathley canyon and 3 a bucket weld province in western green canyon garden banks and northern keathley canyon we recognize six trap types in the primary basins 1 autochthonous salt cored folds 2 turtle structures 3 base of salt truncations 4 salt feeders 5 salt ridges and 6 bucket welds most primary basin explorations to date have targeted traps in one of the first four styles future primary basin exploration will increasingly focus on the traps formed by bucket welds and salt cored ridges the contrasting evolution of these features has implications for reservoir continuity charge access and trap configuration of primary basin boundary trap types salt feeders have the lowest petroleum system risk followed by bucket welds with salt cored ridges having the highest risk

mapping surface mineralogy and scattering behavior using backscattered reflectance from a hyperspectral midinfrared airborne co sub 2 laser system miraco sub 2 las airborne high spectral resolution thermal infrared tir miraco sub 2 las reflectance data were evaluated for mapping surface mineralogy and scattering behavior for a variety of semi arid geological test sites in australia miraco sub 2 las is a rapidly tuned airborne co sub 2 laser system that measures backscattered bidirectional reflectance at 100 wavelengths between 9 1 and 11 2 spl mu m for 2 m footprints in line profile mode an operational methodology is described that permits reduction of the raw airborne signal to ground reflectance this ground reflectance has two major properties namely wavelength dependent mineralogical variations and reflection albedo variations related to surface roughness comparisons between the airborne miraco sub 2 las spectra and laboratory directional hemispherical reflectance dhr spectra show the same spectral shapes though differences in average reflectance albedo occur for some types of rocks the minerals identified using miraco sub 2 las include silicates for example quartz microcline plagiodase almandine spessartine talc tremolite and kaolinite and carbonates dolomite and magnesite as well as vegetation dry and green many of the diagnostic spectral features that allow identification of these materials are narrow 0 2 spl mu m making them difficult to detect with broadband tir systems like the airborne tims and satelliteborne aster based on an empirical relationship between the minimum and maximum reflectance established using laboratory dhr spectra a method is proposed that allows the use of miraco sub 2 las data to identify surfaces that are characterized by lambertian or specular scattering the miraco sub 2 las results show that lambertian type scatterers include soils and many types of isotropic rocks

shear wave velocity tomography of the lithosphere asthenosphere system beneath the mediterranean area abstract the purpose of this study is deriving a 3d tomographic image of the shear wave velocity structure of the lithosphere asthenosphere system of the mediterranean region from rayleigh wave fundamental mode dispersion data the database consists of almost 200 wavetrains corresponding to regional events recorded at the mednet very broad band stations placed in the mediterranean area on the basis of the path averaged group velocities derived for each epicentre station trajectory local group velocities over the area covered by the seismic paths have been obtained for the 10 90 s period range by means of yanovskaya s formulation for laterally heterogeneous media according to the resolution of these local velocities a grid of 1 of latitude per 1 of longitude has been defined over the mediterranean area and a local group velocity dispersion curve has been then assigned to each gridpoint the stochastic inversion of almost 450 local dispersion curves permits deriving the respective 1d shear velocity structures from which the elaboration of a 3d tomographic image of the lithosphere asthenosphere system of the mediterranean region is straightforward as expected taking into account the complexity of this area the shear velocity model reveals significant lateral changes in the crust and uppermost mantle elastic structure as a main feature low shear velocities are deduced for most part of the central and eastern mediterranean basin at shallow depths down to 35 40 km whereas significantly higher velocities are obtained for the basins of the western mediterranean at this depth range this velocity pattern suggests a thicker crust in the centraleastern part with a greater thickness of sedimentary layers on account of the lower velocities deduced for the uppermost levels on the contrary for depths 80 km low shear velocities are obtained towards the west while the highest shear velocities are derived for the eastern mediterranean sea the aegean sea greece the centre and the south of the italian peninsula and the adriatic sea sicily and tunisia the velocity pattern at this depth range suggests a deeper beginning of the asthenosphere varying between 100 and 150 km under these areas while a shallower top around 70 km depth is found beneath the western mediterranean sea the areas where a thicker lithosphere has been deduced depict the main contact between the eurasian and african plates this feature being related to the collision and subduction processes linked to the convergence of both lithospheric plates

gravity anomalies and possible formation mechanism of the dnieper donets basin abstract two dimensional gravity models are presented along several seismic lines intersecting the dnieper donets basin these models are based on velocity sections and the experimental data on the relationship between density and p wave velocity the detailed gravity modelling of gradient layered crustal and upper mantle features clearly reveals increased density in the upper mantle explainable by rock eclogitization using the gravity models we propose a possible mechanism of the dnieper donets basin evolution since the middle devonian the mechanism includes accumulation of magmatic melt in the asthenospheric bulge during post rifting phase transition to ecologite in the uppermost mantle and a flow induced by the evolved heavy bodies we construct a 2 d numerical model of the flow beneath the dnieper donets basin compute this flow and the resulting changes in the surface topography the subsidence curve calculated in the suggested model gives the best fit to the observed tectonic subsidence than curves of thermal subsidence predicted by the stretching model numerical results confirm the observed gravity high over the dnieper donets basin

the hellenic subduction zone a tomographic image and its geodynamic implications new tomographic images of the hellenic subduction zone demonstrate slab penetration in the aegean upper mantle to depths of at least 600 km beneath greece the lower part of the slab appears to be detached at a depth of about 200 km whereas it still seems to be unruptured beneath the southern aegean schematically we derive minimum time estimates for the duration of the hellenic subduction zone that range from 26 to 40 ma this is considerably longer than earlier estimates which vary between 5 and about 13 ma

relative dating of hawaiian lava flows using multispectral thermal infrared images a new tool for geologic mapping of young volcanic terranes the weathering of hawaiian basalts in arid and semiarid environments is accompanied by change in their thermal infrared emittance spectra the spectral differences can be measured and mapped with multispectral imaging systems the differences appear to be related to the degree of development preservation and alteration of glassy crusts the oxidation of iron and the accretion of silica rich surface veneers because the measurements are quantitative and in image format they are useful for estimating relative ages in geologic mapping of lava flows in hawaii this technique is most diagnostic for distinguishing among sparsely vegetated flows less than 1 5 ka in age

geothermal evolution of the astrakhan arch region of the pricaspian basin the astrakhan arch region contains one of the largest sub salt structures of the pricaspian basin where perspectives for hydrocarbon generation and accumulation in the devonian to carboniferous deposits are considered to be high the paper addresses the problem of structural and geothermal evolution of the region deformed by salt movements initially we developed a model of the regional structural evolution along a geological profile using the volume balancing and back stripping methods and geo logical constraints on the sedimentation erosion and paleo water depths then we developed geothermal models along the study profile associated with the regional structural evolution the models were constrained by the temperatures measured in four deep boreholes along the profile we show that the present temperatures and heat flux are influenced by the presence of salt diapirs since the early carboniferous and till middle permian times the temperatures predicted by the models vary significantly due to the regional transgression and the presence of sea water the temperature of devonian carboniferous carbonates increases since the late permian time of post salt deposition and attains its maximum values in the sw part of the profile if the model assumptions concerning the constant vertical and zero lateral heat fluxes are valid we can conclude that hydrocarbons are most likely to be generated in the sw part of the region for the post early permian time

origin and assembly of the tethyside orogenic collage at the expense of gondwana land abstract the tethysides are a superorogenic complex flanking the eurasian continent to the south and consisting of the cimmerides and alpides products of palaeo and neo tethys respectively we here review their evolution mainly on the basis of new maps showing the distribution of sutures magmatic rocks certain palaeobiogeographically and palaeoclimatologically significant taxa and facies and fragments of pan african 900 450 ma orogenic system forming the basement of many tethyside blocks these are supplemented by palaeomagnetic data reported in the literature a fundamental tenet of this paper is that major sutures which contain ophiolite fragments represent tectonic sections between continental blocks where oceanic crust has been subducted palaeo tethys came into existence largely in late carboniferous time coevally it began to be consumed by both internal and peripheral subduction zones which continued into the permian some of these had been inherited from pre tethyan times in the later permian rifting subparallel with the northern margin of gondwana land began between the zagros and malaysia separating a cimmerian continent from n gondwana land and thus heralding the opening of neo tethys and other smaller oceans that were back arc basins of palaeo tethys this rifting possibly also extended farther west into crete and mainland greece however the north china block yangtze block huanan block the eastern moity of the qangtang block north tibet and annamia all originally pieces of the end proterozoic early palaeozoic gondwana land had already separated from it in pre late carboniferous times possibly during the devonian all of these blocks and the cimmerian continent were characterized by cathaysian floral elements in late palaeozoic time palaeomagnetic and palaeontological data showing the original gondwana land affinity of these continental blocks are supplemented by correlating late proterozoic early palaeozoic pan african sutures orogenic belts and sedimentary basin fragments across tethyside sutures late permian foraminiferal provinces are related to this palaeogeographical interpretation by triassic times most cimmeride subduction zones were already in existence the cimmerian continent accelerated its separation from gondwana land and locally in the late permian began disintegrating internally along the waser rushan pshart banggong co nu jiang mandalay ocean by late triassic time all of the chinese blocks except lhasa and annamia had collided with each other and with laurasia the resulting enormous orogenic collage had a soft cushion between itself and laurasia in the form of the enormous accretionary complex of the songpan ganzi this connection enabled laurasian land vertebrates to reach south east asia by late triassic time in late triassic to middle jurassic times most major cimmeride collisions were completed widespread aridity in central asia occurred in late jurassic time probably in the rain shadow of the newly formed cimmeride mountain wall neo tethyan subduction systems formed along the s margin of the cimmerides or within neo tethyan oceanic lithosphere during the jurassic most if not all were north or east dipping they continued the northerly migration of the tethyside blocks evolution of the tethysides influenced the distribution of marine and terrestrial organisms and affected sea level changes and patterns of atmospheric circulation during much of the mesozoic and cainozoic it is likely to have reflected the surface expression of a persistent trend in the large scale convective circulation in the mantle that continuously transported material northward into the tethyan domain

lithologic mapping in arid regions with landsat thematic mapper data meatiq dome egypt digital landsat thematic mapper tm data were evaluated for lithologic mapping capabilities over the meatiq dome area in the hyper arid eastern desert of egypt bi directional spectral reflectance data 0 4 2 5 m for powders of the major rock types exposed in the dome and published spectral reflectance data were used as guides in selecting tm band reflectance ratios that maximize discrimination of individual rock types on the basis of their respective mineralogies comparison of tm data with field and petrographic observations shows 1 increasing amounts of magnetite and other opaque minerals with low flat spectral reflectances decrease the ratio of tm band 5 1 55 to 1 75 to band 1 0 45 to 0 52 m 2 increasing amounts of hydroxyl bearing minerals with hydroxyl ion vibrational absorptions in tm band 7 wavelength region 2 08 to 2 35 m increase the ratio of tm band 5 to band 7 3 increasing amounts of fe bearing aluminosilicates that absorb in the band 4 wavelength region 0 76 to 0 9 m increase the product of the following two tm ratios band 5 to band 4 and band 3 0 63 to 0 69 m to band 4 and 4 thin 5 m desert varnish that covers many outcrops modulates but does not obscure the spectral reflectance signatures of the meatiq rocks the varnish consists of amorphous to poorly crystalline dioctahedral smectite iron oxides and or oxyhydroxides serpentinite mafic mylonite massive amphibolite quartzofeldspathic mylonite biotite schist and quartz phyllonite were mapped on the basis of their unique values in one or more of the three ratio images whereas coarse and fine grained granites granite gneiss and tonalite with similar mineralogies and tm band ratios were mapped as a group finer subdivisions were made where field traverses provided local verification results demonstrate that appropriate processing and presentation of landsat tm data can significantly augment field observations for lithologic mapping of large areas in arid regions

rayleigh wave group velocity tomography in the aegean area data from a large scale experiment which took place in greece during the period january july 1997 have been used to investigate the structure of the aegean area using surface waves during this experiment 30 seismic broadband instruments were deployed throughout the whole greek area additional data during the period 1996 2000 from other temporary networks have been included in the dataset one hundred eighty five events with magnitudes 4 0vmwv5 5 recorded by these stations have been collected and processed the individual dispersion curves of the group velocity of rayleigh waves for each source station path have been calculated producing more than 700 paths covering the studied region these curves have been used to determine rayleigh group velocity maps using a 2d tomography method on the basis of a regionalization of the dispersion measurements local averaged dispersion curves have been obtained and non linearly inverted to obtain models of shear wave velocity versus depth since the dispersion curves in the period range 5 svtv30 s are mostly affected by the crustal structure the model velocities are estimated down to a depth of approximately 35 45 km the results from the non linear hedhehog inversion as applied to a few local dispersion curves show a crustal thickness of approximately 32 km for the northern aegean sea and a relatively thin crust of approximately 22 24 km for the southern aegean sea d 2002 elsevier science b v all rights reserved

3 d structure of the lithosphere in the aegean region summary p wave traveltime residuals from about 300 local and 400 teleseismic earthquakes recorded by the athens seismological network were used to study the structure of the lithosphere in the aegean region teleseismic data included readings from local stations which do not routinely report to the isc the large values of the residuals up to f3 s and their variation with azimuth and epicentral distance indicate significant velocity heterogeneity in the upper mantle p wave traveltime residuals were inverted simultaneously for both local and teleseismic earthquakes tomographic results which are best resolved at lithospheric depths reveal a heterogeneous lithosphere down to a depth of 100km or so a high velocity anomaly is found dipping at an average of 45 to the ne away from the hellenic trench and supports the hypothesis of subduction due to a cooler descending slab of oceanic composition an area of low velocities is observed at depths less than 80 km in the aegean back arc corresponding well with observed high heat flow values in the area in contrast an area of relatively higher velocity anomalies is resolved in the lithosphere underlying the sea of crete the tectonic structure of the crust and upper mantle in the eastern mediterranean area results from the complex interaction of several different geodynamic processes not all of which can be described by simple plate tectonic models at present the eurasian and african plates are converging at a rate of about lcmyr in an approximately n s direction minster jordan 1978 with the latter descending

shear wave attenuation tomography of the lithosphere asthenosphere system beneath the mediterranean region abstract 3 d tomographic images of the shear wave attenuation structure of the lithosphere asthenosphere system beneath the mediterranean region are derived from the inversion of anelastic attenuation coefficients obtained for the fundamental mode of nearly 3100 rayleigh wavetrains recorded at very broad stations placed in the mediterranean region the two station method is used to compute 124 interstation path averaged attenuation coefficients within the 15 120 s period range an adaptation to attenuation coefficients of the yanovskaya ditmar formulation specifically devoted to path averaged surface wave dispersion data and body waves permits to obtain the local attenuation coefficients and their uncertainties for all the period range at every node of a grid covering the studied region maps of stretching azimuths and mean radii of the resolution ellipses are also obtained for every period all of these parameters are strongly related to the spatial path coverage data quality and data coherency a local attenuation dispersion curve is defined then in each grid node and the stochastic inversion of these curves yields 1 d models of inverse shear wave intrinsic quality factor q 1 the shear wave velocity models obtained for every grid node in an elastic tomography developed in a previous work for the same domain are taken as reference models for the inversion process the kriging contouring algorithm is used to represent the resulting 3 d q 1 structure by means of horizontal and vertical cross sections down to 160 km depth the main patterns of this anelastic structure are mostly in agreement with the structural and tectonic features obtained in the reference shear velocity tomography the local attenuation maps manifest notable lateral changes for periods of 20 and 40 s whereas more moderate spatial variation is observed for longer periods the 3 d anelastic models show that at shallow levels the attenuation in the western mediterranean is usually slightly higher than in the central eastern part the area from corsica sardinia islands to italy presents high q 1 values of 40 0 70 0 10 3 down to 75 km depth whereas q 1 does not exceed 20 0 10 3 in the rest of the mediterranean basin except for the south eastern part where slightly higher values are obtained 20 0 30 0 10 3 those high q 1 values suggest the presence of asthenospheric material at shallow levels which would be related to distensive tectonic processes responsible for the recent opening of extensional basins as the tyrrhenian sea and the ligurian provencal basin in the eastern mediterranean the vertical cross sections at different latitudes and longitudes reveal at deep levels some structural patterns consistent with signs of subduction which are linked to the convergence between the african and eurasian plates

the geodynamic evolution of the precaspian basin kazakhstan along a north south section abstract several hypotheses exist for the origin and evolution of the precaspian basin there are more than 20 km of sediments deposited yet there is little consensus on the causes of the subsidence except for the presence of a thick salt layer lower permian the main problem is the chronostratigraphic interpretation of the sediments in the centre of the basin where the calibration of seismic data with well data from the basin margins is problematic at deep levels the age of the deepest sediments could be either riphean or devonian a generalised cross section of the precaspian basin roughly perpendicular to the central elongated e w depocentre is used to represent the basin s evolution several evolutionary steps from the end of the riphean until the present are demonstrated tectonic subsidence analysis indicates that there are six main phases of evolution 1 subsidence during an active rifting phase in riphean times 2 rifting during the vendian ordovician poorly dated 3 significant subsidence during the late devonian in an extensional context possibly due to back arc rifting 4 acceleration of subsidence during the late carboniferous permian synchronous with or just following the closure of the uralian ocean a major subsidence phase in the dniepr donets basin and possible subduction to the south of the basin 5 renewed rifting during the triassic coincident with a general phase of extension in eurasia and the opening of the neo tethys and 6 neotectonic subsidence resulting from crustal down bending in a generally compressional setting the nature of the crust underlying the basin is not well known it could be riphean early palaeozoic or devonian oceanic crust or continental crust attenuated during the several episodes of supposed rifting between the riphean and the triassic estimations of crustal thickness in the basin vary and they depend on the interpretation of a high velocity layer situated at the base of the crust the presence and general distribution of this layer is confirmed by gravity data it may be considered as the uppermost mantle as oceanic crust metamorphosed into eclogite at depth during collision and then exhumed and emplaced at the base of the crust or as lower crust transformed in situ into eclogites the crustal thinning factor leading to the observed present crustal thickness assuming an initial thickness of 40 km is 3 3 in the two first cases and 2 in the latter if the crust is considered to be continental the geophysical and subsidence data are discussed in terms of basin forming mechanisms such as 1 intracontinental rifting of early palaeozoic devonian or permo triassic ages 2 oceanisation of continental crust during riphean or devonian time 3 eclogititisation at the base of the crust in the upper mantle or by metamorphism of subducted oceanic crust and 4 down bending due to compressional forces or mantle flow induced by subduction collision processes in carboniferous and recent times

crustal scale structure and evolution of an arc continent collision zone in the southern urals russia the outcropping geology of the southern urals contains a well preserved accretionary complex related to the paleozoic collision that took place between the magnitogorsk arc and the former east european craton the crustal scale structure of the accretionary complex has been determined from outcropping field geology that is integrated with three reflection seismic profiles the reflection profiles show the accretionary complex to be highly reflective allowing direct comparison of many reflections with surface geological features we interpret the accretionary complex to be a thrust stack that is composed of shallowly subducted continental shelf and rise material syncollisional sediments derived from the arc deeply subducted high pressure gneisses that are intercalated with eclogites and blueschist and at the highest structural level ophiolite complexes it is bound at the base by a thrust and at the rear by a highly deformed zone the main uralian fault adjacent to the backstop the magnitogorsk arc deposition of the late devonian volcaniclastic sediments of the zilair formation appears to be related to collision uplift and erosion of the arc possibly following the arrival of the full thickness of the east european craton continental crust at the subduction zone with the arrival of the continental crust at the subduction zone offscraping and underplating of paleozoic slope and platform material took place at the base of the accretionary complex uplift of the arc was followed by its collapse and the unconformable deposition of lower carboniferous shallow water carbonates on top of it a time lag of 10 15 myr occurred between the high pressure metamorphism and the subsequent arrival of the east european craton at the subduction zone

thermal infrared 2 5 13 5 μm spectroscopic remote sensing of igneous rock types on particulate planetary surfaces fundamental molecular vibration bands are significantly diminished by scattering thus such bands in spectra of fine particulate regoliths i e dominated by 5 m particles or regoliths displaying a similar scale of porosity are difficult to use for mineralogical or rock type identification consequently other spectral features have been sought that may be more useful in spectroscopic remote sensing of composition we find that mineralogical information is retained in overtones and combination tones of the fundamental molecular vibrations in the 3 0 to 7 0 m region but that relatively few minerals have a sufficiently distinctive band structure to be unambiguously identified with currently available techniques more significantly identification of general rock type as defined by the scfm chemical index scfm sio2 sio2 cao feo mgo is possible using spectral features associated with the principal christiansen frequency and with a region of relative transparency between the si o stretching and bending bands however environmental factors may affect the appearance and wavelengths of these features finally prominent absorption bands may result from the presence of relatively small amounts of water hydroxyl or carbonate because absorption bands exhibited by these materials in the 2 7 to 4 0 m region where silicate spectra are otherwise featureless increase strongly in spectral contrast with decreasing particle size such materials are thus detectable in very small amounts in a particulate regolith composed predominantly of silicate minerals

structure and kinematics of the central sivas basin turkey salt deposition and tectonics in an evolving fold and thrust belt this work has been made possible by funding from total s a in the framework of the structural geology chair at e2s university of pau pays adour held by jean paul callot

the impact of base salt relief on salt flow and suprasalt deformation patterns at the autochthonous paraautochthonous and allochthonous level insights from physical models

s velocity structure and radial anisotropy in the aegean region from surface wave dispersion summary the lithospheric structure of the aegean region is investigated by analysis of rayleigh wave fundamental mode dispersion measurements isotropic 1 d models for almost 100 two station ray paths across the region display distinct variations in the moho depth and crustal s wave velocities the descending slab of the subducting african plate can be resolved down to 120 km depth beneath the volcanic arc three different regions are distinguished in terms of moho depth 1 the forearc with large crustal thicknesses between 38 and 48 km and an average of 43 km 2 the northern aegean with an average moho depth of 28 km and 3 the southern aegean central volcanic arc i e cyclades and sea of crete with an even thinner crust of around 25 km lateral variations in structure between 25 and 55 km depth indicate a marked difference between the western and eastern forearc collocated with pronounced changes in trench and slab geometry as well as published deformation rates s velocities between 25 and 55 km depth are low everywhere beneath the forearc but increase from the peleponnesus to crete an abrupt change occurs between western and central crete in terms of the visibility of the aegean moho and the seismic structure of the lithospheric mantle wedge an aegean mantle wedge with s velocities above 4 4 km s 1 is only observed to the east of central crete whereas to the west velocities of less than 4 0 km s 1 occur down to the plate contact these low velocities above the slab may indicate the presence of a melange of metamorphic rocks at the depths a low velocity asthenospheric layer is observed beneath the sea of crete and the cyclades below 40 km depth between the thinned lithosphere above and the slab below the observed radial anisotropy in the northern part of the aegean is likely to be due to preferred orientation of anisotropic minerals within the lower crust possibly caused by lateral ductile flow associated with recent lithospheric extension

thermal infrared spectral character of hawaiian basaltic glasses multispectral thermal infrared remote sensing of hawaiian basalts younger than a few hundred years old can be used to discriminate basalt lava flows that are difficult to map with visible and near infrared images laboratory thermal infrared reflectance spectra of the exposed surfaces of mauna loa and kilauea basalts show systematic changes with age fresh glass collected from active lava flows shows a broad reflectance feature between 8 and 12 m indicative of a strong degree of disorder after a few weeks of exposure to the environment the spectra of the top surfaces of samples begin to exhibit spectral features suggestive of ordering into silicate chainlike and sheetlike units with progressive aging features of apparent sheetlike structures become the preferred mode as soon as 3 years after emplacement a silica rich coating can begin to develop on the surfaces adding another spectral feature to the laboratory reflectance measurements the thermal infrared multispectral scanner tims with six channels between 8 and 12 m has been used to take advantage of these spectral differences in basalts to map flows in hawaii remote sensing instruments with increased spectral resolution in the thermal infrared would aid in further discrimination of basalts with more subtle differences in age quenching and weathering histories

measured effects of desert varnish on the mid infrared spectra of weathered rocks as an aid to tims imagery interpretation the thermal infrared spectral properties 7 12 mu m of natural rock surfaces from silver lake ca are discussed although the reflectance of weathered rocks is largely a function of the quartz content in rocks the presence of desert varnish clay coating on rocks reduces the reflectance and spectral contrast with features unique to the rock spectra persisting if varnish is thin thick varnish has a spectrum with a reflectance peak near 9 6 mu m due to clays and resembles the spectra of clay rich playa surfaces comparison of laboratory reflectance spectra for varnish and weathered rock samples with thermal infrared multispectral scanner tims emissivity spectra for silver lake suggests that tims signatures for felsic rocks are dominated by weathered rock and rock debris in contrast it is likely that varnish plays an important role in the tims signatures of mafic rocks

structure and genetic mechanisms of the precambrian rifts of the east european platform in russia by integrated study of seismic gravity and magnetic data abstract integrated models of the deep structure and origin of rifts located within the russian portion of the east european platform have been developed from recent dss results new gravity and magnetic modelling and geological and older geophysical data acquired over the last 50 years the mezen rift province the middle russian rift the valday rift the pachelma rift and the rifts within the pre caspian depression were studied all of these rifts were affected by extension and filled with syn rift sediments at different times through the riphean 1650 650 ma post rift sedimentary basins developed from the end of the neoproterozoic until the cenozoic the models indicate that the crustal structure and genesis of the individual rifts are different the mezen rift province was formed under a condition of limited extension of the continental crust the mckenzie pure strain mechanism is acceptable for lithosphere extension in the middle russian rift the wernicke model best expresses the valday and pachelma rifts the rift process in the pre caspian area is explained in terms of large scale sliding apart of lithospheric plates and approached the stage of development of oceanic crust

seismic wave attenuation in the upper mantle beneath the aegean region a detailed study of p and s waves from earthquakes located along the hellenic arc and recorded by the greek seismological network shows an abnormal distribution of the seismic waves in the central aegean sea the data indicate a zone of anomalously high seismic wave attenuation in the upper mantle beneath the cyclades plateau and the inner part of the volcanic arc several independent observations suggest the presence of magma beneath the cyclades massif

lithospheric structure in the southern canadian cordillera from a network of seismic refraction lines lithospheric velocity structure and its relationship to regional tectonics and development of the southern canadian cordillera are derived from a synthesis of interpretations from nine in line seismic refraction wide angle reflection profiles and broadside data recorded during the lithoprobe southern cordillera refraction experiment score and other refraction experiments across southern british columbia and one profile in northwestern washington consistency of the score two dimensional models at their intersection positions is achieved through application of a simultaneous inversion of all relevant traveltime data the cross sectional and map presentations demonstrate the strong degree of three dimensional heterogeneity within the crust and upper mantle a first order characteristic is the continuous increase in crustal velocities westward from the foreland belt to the insular belt the variations do not correlate with the morphogeological belts they do correspond with large scale geological and or

late palaeozoic to triassic evolution of the turan and scythian platforms the pre history of the palaeo tethyan closure abstract a number of en echelon arranged southwest facing arc fragments of palaeozoic to jurassic ages sandwiched between two fairly straight east northeast trending boundaries constitute the basement of the scythian and the turan platforms located between the laurasian and tethyside units they have until now largely escaped detection owing to extensive jurassic and younger cover and the inaccessibility of the subsurface data to the international geological community these units are separated from one another by linear gently curved faults of great length and steep dip those that are exposed show evidence of strike slip motion the arc units originally constituted parts of a single silk road arc located somewhere south of the present day central asia for much of the palaeozoic although by the late carboniferous they had been united into a continental margin arc south of the tarim basin and equivalent units to the west and east they were stacked into their present places in northern afghanistan turkmenistan caucasus and the northern black sea by large scale right lateral strike slip coastwise transport along arc slicing and arc shaving strike slip faults in the triassic and medial jurassic simultaneously with the subductive elimination of palaeo tethys this gigantic dextral zone the silk road transpression was a trans eurasian structure and was active simultaneously with another similar system the gornostaev keirogen and greatly distorted eurasia the late palaeozoic to jurassic internal deformation of the dniepr donets aulacogen was also a part of the dextral strain in southern europe when the emplacement of the scythian and turan units was completed the elimination of palaeo tethys had also ended and neo tethyan arcs were constructed atop their ruins mostly across their southern parts the western end of the great dextral zone that emplaced the turan and scythian units horsetails just east of north dobrudja and a small component goes along the tornquist teisseyre lineament

a model of palaeozoic obduction and exhumation of high pressure low temperature rocks in the southern urals abstract a new evolutionary geodynamic model of devonian continental subduction and exhumation of high pressure low temperature metamorphic rocks in the southern urals is proposed based on the results of physical modelling geological and geophysical data and on the comparison of this belt with other orogens the model includes the following principal phases 1 closure of the western uralian ocean by eastward intraoceanic subduction associated with the magnitogorsk volcanic arc 2 subduction of the european continental margin causing failure of the overriding plate in the arc area along a fault dipping eastward under the arc 3 subduction into the mantle of the fore arc block together with the underlying continental crust and sedimentary layer the sedimentary cover as well as the crustal and mantle fragments of this block are scraped off and accreted in front of and under the arc the continental crust shielded from the hot mantle by the fore arc block subducts to depths of more than 150 km remaining at a relatively low temperature the crust then fails at depths of several tens of kilometres 4 the subducted crustal slice starts to rapidly rise and intrude the interplate zone scraping and pushing up the sediments and slivers of the oceanic fore arc block previously dragged down to different depths 5 exhumation of the rising high pressure low temperature rocks within the uraltau dome separating the subduction accretionary complex from the magnitogorsk arc the eastern border of the uraltau dome coincides with the main uralian fault this fault represents a complex suture zone which at the stage of deep crustal subduction was associated with a major thrust subduction fault and at the exhumation stage with a major normal fault corresponding to the upper surface of the rising crustal sedimentary body

active airborne infrared laser system for identification of surface rock and minerals emissivity and reflectivity in the thermal infrared spectral region 8 13 m may be used to discriminate among rocks and minerals although considerable success has been achieved in remote sensing classification of rock types based on emissivity measurements made with nasa s thermal infrared multispectral scanner tims classification based on reflectivity offers several advantages much narrower bandwidths are used higher signal to noise ratios are possible and measurements are little affected by surface temperature as a demonstration an airborne co2 laser instrument was flown along the margin of death valley california measurements of spectral reflectance collected with this device were compared with emissivity measurements made with the tims data from either instrument provided the means for recognizing boundaries between geologic units including different rock types and fan surfaces of different ages

one dimensional models of shear wave velocity for the eastern mediterranean obtained from the inversion of rayleigh wave phase velocities and tectonic implications summary on a sw ne profile from the libyan coast towards central turkey phase velocity curves of the fundamental rayleigh mode were measured using a two station method the inversion of phase velocity curves yields 1 d models of shear wave velocity down to approximately 200 km depths that may be interpreted as estimates of average models between neighbouring stations on the profile strong lateral variations in the shear wave velocity structure are imaged along the profile the subducted oceanic african mantle lithosphere is indicated in 1 d models for the region around crete by significantly enlarged shear wave velocities it is also imaged by an average model of the structure between stations on crete and santorini on a path crossing the libyan sea south of crete the resulting model is slower than a model expected for 110 myr old oceanic lithosphere the passive african margin is thus assumed to extend northwards beneath the libyan sea anomalous low shear wave velocities are found for the uppermost mantle beneath central turkey down to a depth of approximately 130 km using two stations on crete the average depth of the oceanic moho within the subducting slab is estimated to be at approximately 50 km beneath crete for this arc parallel path an enlarged standard deviation of the measured phase velocities of approximately 0 2 km s 1 between 10 and 30 mhz is observed that is probably caused by strong lateral heterogeneity related to the subducting slab in addition in this frequency range an anomalous propagation of the fundamental rayleigh mode is detected that is indicated by measured phase velocities that are approximately one standard deviation faster than phase velocities expected from a great circle approximation an average shear wave velocity of approximately 3 5 km s 1 is observed above the oceanic moho in order to explain the recent lithospheric structure of the hellenic subduction zone a tectonic model is assumed for the ne sw striking profile considered it is based on the calculated 1 d models tectonic reconstructions and on a model derived from the metamorphic history of rocks exposed on crete the suggested model summarizes the tectonic development at a lithospheric scale starting in the late cretaceous accretion of crustal material of two microcontinents to eurasia is assumed while continuous subduction of the oceanic lithosphere of different ocean basins and possibly of the mantle lithosphere of the microcontinents resulted in a single slab the length of the oceanic lithosphere that was subducted south of crete is estimated to be not greater than approximately 550 km

microearthquake seismicity and fault plane solutions in the southern aegean and its geodynamic implications summary seismicity mi 3 5 in the southern aegean located using data collected during seven weeks of recording by a temporary network of seismological stations largely follows the hellenic arc the sea of crete is nearly aseismic and only little activity is located south of the hellenic trench within the african plate focal mechanisms exhibit reverse faulting in the external part of the arc and normal faulting inside it this normal faulting indicates n s extension in the northern aegean the gulf of corinth the cyclades and dodecanese islands but nw se extension in southern peloponnese and western crete and e w extension in eastern crete this non uniform strain pattern suggests that the aegean region not only extends in a n s sense with the hellenic arc moving south westward relative to the eurasian plate but also by e w extension of its southern margin so that there is a net divergence of material

shear velocity structure in the aegean region obtained by joint inversion of rayleigh and love waves we present a shear velocity model of the crust and uppermost mantle under the aegean region by simultaneous inversion of rayleigh and love waves the database consists of regional earthquakes recorded by portable broadband three component digital stations that were installed for a period of 6 months in the broader aegean region for each epicentre station ray path group velocity dispersion curves are measured using appropriate frequency time analysis ftan the dispersion measurements for more than 600 love wave paths have been used we have also incorporated previous results for c 700 rayleigh wave paths for the study area the single path dispersion curves of both waves were inverted to regional group velocity maps for different values of period 6 32 s via a tomographic method the local dispersion curves of discrete grid points for both surface waves were inverted nonlinearly to construct 1d models of shear wave velocity v depth in most cases the joint inversion of rayleigh and love waves resulted in a single model from the multiple models compatible with the data that could interpret both rayleigh and love wave data around 60 local dispersion curves for both rayleigh and love waves were finally jointly inverted as expected because of the complex tectonic environment of the aegean region the results show strong lateral variations of the s wave velocities for the crust and uppermost mantle our results confirm the presence of a thin crust typically less than 28 30 km in the whole aegean sea which in some parts of the southern and central aegean sea becomes significantly thinner 20 22 km in contrast a large crustal thickness of about 40 45 km exists in western greece and the remaining part of continental greece is characterized by a mean crustal thickness of about 35 km a significant sub moho upper mantle low velocity zone lvlmantle with velocities as low as 3 7 km s is clearly identified in the southern and central aegean sea correlated with the high heat flow in the mantle wedge above the subducted slab and the related active volcanism in the region the results obtained results are compared with independent body wave tomographic information on the velocity structure of the study area and exhibit a generally good agreement although significant small scale differences are

lateral mobility of minibasins during shortening insights from the se precaspian basin kazakhstan abstract minibasin provinces are widespread and can be found in all types of salt tectonic settings many of which are prone to shortening previous studies of how minibasin provinces shorten assume that the salt between the minibasins is homogeneous and that the base of salt is flat or of low relief such that minibasins are free to move laterally here we investigate how minibasin provinces respond to shortening when the lateral mobility of the minibasins is restricted by intra salt sediment bodies in order to gain a greater understanding of the controls on the structural styles and modes of tectono stratigraphic evolution exhibited in minibasin provinces we examine a borehole constrained 3d seismic reflection dataset from the se precaspian basin onshore western kazakhstan the study area is characterised by large supra salt minibasins and an array of smaller intra salt sediment packages distributed between these larger minibasins we first outline the evidence of episodic shortening between the late triassic and present after the onset of supra salt minibasin subsidence next we document spatial variations in shortening style showing how these relate to the concentration of intra salt sediment packages finally we develop synoptic models showing how intra salt sediment packages influence both the lateral mobility of minibasins during shortening and the resultant structural style and we compare and contrast our findings with existing models and other natural examples of shortened minibasin provinces we conclude that minibasin provinces may have different degrees of lateral mobility depending on the presence or absence of intrasalt barriers and that these variations provide a first order control on basin shortening style and tectono stratigraphic evolution

seismicity depth pattern seismic energy and b value depth variation in the hellenic wadati benioff zone abstract the statistics of the vertical distribution of the foci of earthquakes which occurred in the hellenic wadati benioff zone during the period 1964 1982 show that the seismicity pattern energy and b value of the frequency magnitude relation vary with depth in a specific manner the seismicity patterns of the western and the eastern flanks of the hellenic subduction zone vary with depth in a similar manner whereas the seismic energies and b value depth variations for these two flanks of the subduction zone do not show such a similarity

the subsidence of the williston basin a detailed comparison between the pre cretaceous stratigraphic record in the williston basin and the available information about phanerozoic sea level changes indicates that most stratigraphic breaks in the basin reflect eustatic control the basin appears to have been subsiding continuously and steadily about the same centre for most of the phanerozoic above a thick 55 km continental crust deposition kept up with subsidence and most of the sedimentary record was laid down close to sea level erosional breaks in the stratigraphic record may represent periods of removal of strata during episodes of low sea level a possible explanation of this essentially steady nonexponential subsidence record is that a mafic subcrustal body is undergoing transformation to eclogite

exhumation of high pressure rocks a review of concepts and processes the exhumation of high pressure metamorphic rocks requires either the removal of the overburden that caused the high pressures or the transport of the metamorphic rocks through the overburden exhumation cannot be achieved simply by thrusting or strike slip faulting it may be caused by erosion of shortened and thickened crust but this is unlikely to be the only mechanism for exhuming rocks from depths greater than about 20 km one or more of the following additional mechanisms may be involved 1 corner flow of low viscosity material trapped between the upper and lower plates in a subduction zone can cause upward flow of deeply buried rock and may explain some occurrences of high pressure tectonic blocks in melange this process does not however appear to be adequate to explain the exhumation of regional high pressure terrains 2 buoyancy forces acting directly on metamorphic rock bodies may cause them to rise relative to more dense surroundings this is likely to be the most important mechanism of exhumation of crustal rocks subducted into the mantle but cannot explain the emplacement of coherent tracts of high density metamorphic rock into shallow crustal levels some high pressure blocks emplaced at shallow levels in accretionary terrains may have been entrained in diapiric intrusions of low density mud or serpentinite 3 extension driven by the forces associated with contrasts in surface elevation may explain the exhumation and structural setting of many high pressure terrains extension may occur in the upper part of an accretionary wedge thickened by underplating or it may affect the whole lithosphere in a region of intracontinental convergence if surface elevation has been increased by the removal of a lithospheric root in the second case extension may be accompanied by magmatism and an evolution towards higher temperature during decompression of the metamorphic terrain

variations in salt expulsion style within the sable canopy complex central scotian margin1 1this article is one of a series of papers published in this cjes special issue on the theme of mesozoic cenozoic geology of the scotian basin there are two allochthonous salt canopies within the central scotian margin one on the shelf and another in deeper waters on the scotian slope the sable shelf canopy trends southwest northeast and covers an area approximately 650 km2 salt thickness within this canopy is generally 1000 m reloading of the salt has welded out the margins of the canopy significantly reducing its extent salt tectonics related to this canopy produced many of the exploration targets drilled on the shelf the sable slope canopy is 50 km basinward on the scotian slope this canopy is significantly larger covering 12 700 km2 and the allochthonous salt is as thick as 3500 m although the two canopies are separated by a significant distance a common detachment surface connects them in multiple locations extensional systems detach in the sable shelf canopy displace strata downdip and expel salt into the sable slope canopy the outer shelf and slope region separating these two canopies is dominated by detachment systems o

greek tectonics and seismicity abstract the validity of existing tectonic models for the area of greece is examined in the light of the new recalculated parameters for earthquakes of the region makropoulos and burton 1981 relocated hypocentral positions are extracted from the catalogue to form radial and vertical distance depth cross sections centred on a reference point near the mid point of the aegean volcanic arc and these are used to form a three dimensional topography of the base of earthquake occurrence below 60 km isodepth maps are extracted from this topography as both three and two dimensional map presentations these maps reveal several significant features of deep seated tectonic processes in the region isodepths exceeding 150 km are seen in the northwest aegean and these are more closely linked to the sporadhes and gulf of thermaicos rather than the north aegean trough the 150 km isodepths are also seen in the northeast aegean straddling the dardanelles in the northeastern part of the peloponnesus gulf of saronikos and eastern gulf of corinth in the southern peloponnesus towards crete and extending from north of kos to south of rodos the largest extent of deepest activity is seen south of rodos and this continues towards southwest of turkey the subduction zone of the hellenic arc is clear but smooth benioff zones are not the norm and these data show that structural complexity is more readily observed it is concluded that none of the proposed tectonic models completely explain the observed activity over the whole area and rather than propose yet another model places where further work is still particularly necessary are identified

rocky 7 prototype mars rover field geology experiments 1 lavic lake and sunshine volcanic field california experiments with the rocky 7 rover were performed in the mojave desert to better understand how to conduct rover based long distance kilometers geological traverses on mars the rover was equipped with stereo imaging systems for remote sensing science and hazard avoidance and 57fe mossbauer and nuclear magnetic resonance spectrometers for in situ determination of mineralogy of unprepared rock and soil surfaces laboratory data were also obtained using the spectrometers and an x ray diffraction xrd xrf instrument for unprepared samples collected from the rover sites simulated orbital and descent image data assembled for the test sites were found to be critical for assessing the geologic setting formulating hypotheses to be tested with rover observations planning traverses locating the rover and providing a regional context for interpretation of rover based observations analyses of remote sensing and in situ observations acquired by the rover confirmed inferences made from orbital and simulated descent images that the sunshine volcanic field is composed of basalt flows rover data confirmed the idea that lavic lake is a recharge playa and that an alluvial fan composed of sediments with felsic compositions has prograded onto the playa rover based discoveries include the inference that the basalt flows are mantled with aeolian sediment and covered with a dense pavement of varnished basalt cobbles results demonstrate that the combination of rover remote sensing and in situ analytical observations will significantly increase our understanding of mars and provide key connecting links between orbital and descent data and analyses of returned samples

models of convergent boundary tectonics implications for the interpretation of lithoprobe data physical models of convergent boundary processes can provide insights into compressional orogens such as those studied by lithoprobe we summarize the qualitative tectonic style of a series of mode

three dimensional seismic attenuation structure beneath the aegean region and its tectonic implication abstract the three dimensional attenuation structure beneath the aegean sea and the surrounding regions is determined by inversion of seismic intensity data a large number of seismic intensity data have been accumulated in a uniform scale in the aegean region where the seismic activity is much higher than that of the other mediterranean regions nearly 7000 seismic intensity data from 50 earthquakes that have occurred in these regions are used to determine seismic attenuation structure and source acceleration of the earthquakes the resultant structure reveals a remarkable contrast of attenuation in the top layer depth 0 40 km low q is dominant in the aegean sea while high q is dominant in the surrounding land areas except for the southwestern turkey the low q regions correspond to areas of neogene quaternary grabens where the high seismicity of shallow earthquakes appears in the upper mantle high q zones corresponding to the subducting african plate dominate along the hellenic arc the irregular shape of high q zones might reflect the split or disintegration of the african slab some low q spots corresponding to the distribution of volcanoes exist along the volcanic arc the low q spots might correspond to diapirs causing the subduction volcanism

structural evolution of salt influenced fold and thrust belts a synthesis and new insights from basins containing isolated salt diapirs abstract lateral shortening is expressed in unique ways in salt basins especially if pre shortening diapirs are present we present an overview of previously published and new physical models and present new 3 d conceptual models that capture the evolution of shortening structures in salt provinces dominated by precursor isolated diapirs termed isolated diapir provinces in such provinces isolated diapirs form only a minor volumetric component of a sedimentary basin however due to the relative weakness of rock salt and their ability to localize strain during shortening they have a disproportionately large influence on structural development we find three key mechanical principles govern the processes and structural styles developed during shortening of isolated diapir provinces first salt diapirs shorten before surrounding sedimentary rocks due to their relative weakness and so form salients in the thrust front during early shortening second diapirs tend to nucleate folds and faults which radiate out from the diapirs third as diapir walls converge the roof must shorten extrusive salt sheets are expelled through thin roofs but thicker roofs resist piercement and so tend to undergo complex folding and faulting as a result of these principles the first order controls on the structural styles expressed across a shortened isolated diapir province are the configuration the diapir array prior to shortening the connectivity of these diapirs prior to shortening total strain magnitude and diapir roof thickness second order controls include the initial cross sectional and map view geometry of diapirs diapir size and diapir orientation with respect to the shortening direction

shear wave velocity models from rayleigh wave dispersion in the broader aegean area an analysis of rayleigh waves generated by earthquakes in the broader aegean is undertaken to estimate variations in the shear wave velocity structure in the crust and upper mantle down to about 70 km depth the study centres literally on the vertical component long period standard seismograph at athens ath and is only possible because this station has provided good quality data over many years of continuous operation rayleigh waves from 81 earthquakes during 1963 87 with surface wave magnitudes in the range 4 2 to 5 4 and epicentral distances of 300 500 km from athens are analysed these earthquake epicentres are selected in clusters defining 12 propagation paths across the broader aegean and radial to athens the highest concentration of azimuthal sampling traverses the hellenic volcanic arc the ensuing group velocity curves over these radial paths are inverted to shear wave velocity depth models using linear and then monte carlo hedgehog inversion schemes the resulting velocity depth solutions from both schemes presented as individual path velocity depth profiles 3 d azimuthal perspectives and contoured velocity depth panoramas over the whole broader aegean are corroborative the western arc of azimuths extending from chalkidiki north of athens to sw crete south of athens have velocity depth profiles which consistently reach sub moho velocities at about 45 km depth the most striking feature revealed by the contoured shear wave velocity depth panoramas is an extensive zone of relatively low velocity about 3 8 km s 1 centred around 30 km depth which may extend from 20 to 40 km depth this low velocity zone is contained in the wedge of paths from carpathos rhodes and sw turkey which traverse the hellenic volcanic arc and subtend an angle of about 33 at athens there is also slight evidence for anomalously low velocities at greater depths around 4 1 4 2 km s 1 at about 50 60 km depth but these are at the limits of useful resolution of the available data nevertheless these indications are at their strongest in the same wedge below the hellenic volcanic arc