3 d density model of the crust of southern and central finland obtained from joint interpretation of the svekalapko crustal p wave velocity models and gravity data 3 d density model of the crust of southern and central finland obtained from joint interpretation of the svekalapko crustal p wave velocity models and gravity data

the glueckstadt graben of the north german basin new insights into the structure from 3d and 2d gravity analyses the structure of the glueckstadt graben has been investigated by use of 3d gravity backstripping technique and by 2d gravity and magnetic modelling subtracting the gravity effects of the meso cenozoic sediments together with permian salt reveals a positive residual anomaly within the glueckstadt graben this anomaly includes two local maxima over the westholstein and eastholstein troughs the 2d gravity models point to the presence of a high density body within the lower crust of the glueckstadt graben in addition the results of 2d magnetic modelling indicate that the central part of the high density body is overlain by an area with high susceptibility most probable the formation of this high density body is a result of complex poly phase tectonic history of the study area finally the results of gravity modelling indicate that permian salt is not homogeneous 3d gravity analysis and especially 2d gravity modelling have distinguished the differences in degree of salt saturation in salt rich bodies and elucidate the proportion of rotliegend salt

the density contrast at the mohorovicic discontinuity summary the compilation of new global mohorovicic moho topographic data enables us to estimate the density contrast between the crust and mantle assuming that this contrast is constant the minimization of the external gravitational potential induced by the earth s topographic masses and the moho discontinuity gives the value of 0 28 gcm 3 for the density jump at the moho under the continental areas for the oceanic areas where the information about the moho depths is unavailable or poor the procedure has not been applied

chloride bearing materials in the southern highlands of mars chlorides commonly precipitate during the evaporation of surface water or groundwater and during volcanic outgassing spectrally distinct surface deposits consistent with chloride bearing materials have been identified and mapped using data from the 2001 mars odyssey thermal emission imaging system these deposits are found throughout regions of low albedo in the southern highlands of mars geomorphologic evidence from orbiting imagery reveals these deposits to be light toned relative to their surroundings and to be polygonally fractured the deposits are small

gravity modelling of the litho asthenosphere system in the central mediterranean abstract the results of the 2 5 d gravity modelling of the litho asthenosphere system in the central mediterranean along two regional geotransects are presented and their possible implications for the geodynamical evolution of this area are discussed particularly gravity data on the tyrrhenian and provencal balearic basins were interpreted introducing significant constraints by means of several main petro physical parameters tied to the litho asthenospheric evolution during the extensive tectonics by this approach based on the model of mckenzie and bickle in j petrol 29 pp 625 679 1988 and white and mckenzie in j geophys res 94 b6 pp 7685 7729 1988 the estimation of the vertical density distribution in the lithosphere asthenosphere system has been possible significant differences in the gravity anomaly field occur when different density models of asthenospheric upwelling are considered this depends on factors like the thermal regime the stretching of the lithosphere and its thickness before it the obtained results contributed to the validation of models interpreting the origin of the tyrrhenian and ligurian provencal basins as related to a passive extensional process rather than to the presence of an active upwelling asthenosphere beneath the central mediterranean basins

searching at the right time of day evidence for aqueous minerals in columbus crater with tes and themis data the primary objective of the thermal emission imaging system themis experiment which has been in orbit at mars since early 2002 is to identify minerals associated with hydrothermal and subaqueous environments data from themis have supported the presence of clays silica rich deposits and chlorides but has not before provided definitive evidence for the presence of sulfates this is an especially puzzling result given that sulfates have been extensively identified with other instruments at mars if present sufficiently exposed and in high enough abundances such minerals should be detectable in orbital thermal infrared spectra at the resolution of themis the extended mission proposal for themis on mars odyssey suggests that the detection of all minerals may be enhanced by observing at an earlier time of day and thus at warmer temperatures therefore in 2009 odyssey moved to an earlier orbit time here we examine themis data collected when the earlier orbit time coincided with the martian local southern late summer ls 270 for columbus crater where compact reconnaissance imaging spectrometer for mars crism data have detected a number of aqueous minerals some of the warmest themis images show evidence for aqueous minerals although not in the same locations where crism finds the highest concentrations several factors contribute to this result including differences in the diurnal temperature curve and levels of induration and particle size for themis earlier time of day and proper seasonal observations combine to provide warm surface temperatures and ideal low atmospheric opacity that significantly increases the ability to definitively identify low spectral contrast aqueous minerals at the surface of mars

thermomechanical lithospheric structure of the central fennoscandian shield abstract the deep seismic sounding dss profiles baltic including its southern continuation the sovetsk kohtla jarve skj profile sveka the northern part of babel polar fennia and pechenga kovdor kostomuksha were used in studying the present day thermomechanical structure of the central fennoscandian shield these profiles are located in different tectonic units which represent different stages in precambrian crustal and lithospheric growth first present day geotherms were constructed for several points along the dss profiles successively strength envelopes were calculated using the obtained geotherms and rheological flow laws variations in strain rate were also considered in the computations of the strength envelopes the integrated crustal and lithospheric strengths the thicknesses of the mechanically strong crust msc and mechanically strong lithosphere msl and the rheological thickness of the lithosphere were derived from these strength envelopes the obtained mechanical structures for different regions were analysed and compared with other geophysical data e g seismicity depth and isotherm depth distributions the rheological results show lateral variations in the lithospheric strength reflecting the geometry of the lithosphere and following roughly the same trend as the geochronological development of the fennoscandian shield the mechanical structure shows distinct decoupling of the weak lower crust and the strong upper mantle particularly with a wet rheology this decoupling interrupts the transmission of the differential stress from the brittle upper crust to the ductile lower crust and through it to the mantle lithosphere the weak lower crustal layer is also detected with a dry rheology in the svecofennian area whereas in the archaean side it is not distinct the assumed frictional transition temperature of 350 c varies between the depths of 25 and 44 km with an average value of 35 km this is in good agreement with the observed focal depth limit of 31 km consequently it seems that the velocity weakening velocity strengthening explains best the real lower boundary of seismicity

mapping the lithosphere asthenosphere boundary through changes in surface wave anisotropy abstract the alignment of olivine crystals is considered as the dominant source of seismic anisotropy in the subcrustal lithosphere and asthenosphere different components of large scale anisotropy can be traced in depth distributions of the radial and azimuthal anisotropy of surface waves we propose a global model of the lithosphere asthenosphere boundary lab as a transition between a frozen in anisotropy in the lithosphere to anisotropy in the sublithospheric mantle related to the present day flow due to different orientations of velocity maxima in the anisotropic subcrustal lithosphere and the asthenosphere the velocity contrast related to the lab can increase in particular directions because of their long wavelengths and horizontal propagation surface waves suffer from poor lateral resolution however surface waves with various wavelengths allow us to map gross features of the lab with a good vertical resolution we estimate depths to the lab to be between 200 and 250 km for the precambrian shields and platforms around 100 km for the phanerozoic continental regions and 40 70 km beneath oceans from the world wide depth distribution of the radial and azimuthal anisotropy of surface waves

mineralogy of the msl curiosity landing site in gale crater as observed by mro crism orbital data acquired by the compact reconnaissance imaging spectrometer for mars crism and high resolution imaging science experiment instruments on the mars reconnaissance orbiter mro provide a synoptic view of compositional stratigraphy on the floor of gale crater surrounding the area where the mars science laboratory msl curiosity landed fractured light toned material exhibits a 2 2 m absorption consistent with enrichment in hydroxylated silica this material may be distal sediment from the peace vallis fan with cement and fracture fill containing the silica this unit is overlain by more basaltic material which has 1 m and 2 m absorptions due to pyroxene that are typical of martian basaltic materials both materials are partially obscured by aeolian dust and basaltic sand dunes to the southeast exhibit differences in mafic mineral signatures with barchan dunes enhanced in olivine relative to pyroxene containing longitudinal dunes this compositional difference may be related to aeolian grain sorting

searching for regional crustal velocity density relations with the use of 2 d gravity modelling central europe case in this paper we search for a reference relation between seismic p wave velocity v and density ref for the continental crust based on the results of modern seismic experiments we compiled 2 d seismic models into a network of four each about 1100 1400 km long continental scale seismic transects cutting all main tectonic units in central europe the moho depth about 52 km beneath the tesz in se poland to about 25 km beneath the pannonian basin and the crustal structure of this area are characterised by a large variation this structural variation provides an interesting basis for gravity studies and especially for analysing the difference of the density structure between two major tectonic provinces of distinctive age difference precambrian and phanerozoic the 2 d gravity modelling applied for crustal cross sections representing the regional structure based on a unified gravity anomaly map of the area allows for a stable determination of some general features of the regional reference velocity density relation for the continental crust in general three major seismo petrological types of rocks can be distinguished sediments crystalline crust and mantle in compacted sediments the reference velocity density relation is well described by the gardner or nafe drake model calculated gravity anomalies using unified velocity density relation for the whole crystalline crust well describe observed anomalies with an average difference of 14 mgal however calculated gravity anomalies using separated velocity density relations for the crystalline crust of precambrian and phanerozoic europe describe observed anomalies better than for the entire crust with an average difference 12 mgal the most important feature of these relations is the large differentiation of the derivative d ref dv in the crystalline crust being about 0 3 g s m4 for precambrian and about 0 1 g s m4 for the phanerozoic crystalline crust the modelling suggests a very small density value in the uppermost mantle 3 11 g cm3 below the younger area while for the older area it is 3 3 g cm3

a global view of martian surface compositions from mgs tes thermal emission spectrometer tes data from the mars global surveyor mgs are used to determine compositions and distributions of martian low albedo regions two surface spectral signatures are identified from low albedo regions comparisons with spectra of terrestrial rock samples and deconvolution results indicate that the two compositions are a basaltic composition dominated by plagioclase feldspar and clinopyroxene and an andesitic composition dominated by plagioclase feldspar and volcanic glass the distribution of the two compositions is split roughly along the planetary dichotomy the basaltic composition is confined to older surfaces and the more silicic composition is concentrated in the younger northern plains

regional scale stratigraphy of surface units in tyrrhena and iapygia terrae mars insights into highland crustal evolution and alteration history 1 the compositional thermophysical and geologic characteristics of surface units in iapygia and tyrrhena terra 60 e 100 e 0 30 s provide new insights into the compositional stratigraphy of the region intercrater plains are dominated by two surface units the older unit unit 1 is deficient in olivine and more degraded and likely consists of a mixture of impact volcanic and sedimentary materials the younger unit unit 2 is enriched in olivine exhibits a resistant morphology and higher thermal inertia and likely represents volcanic infilling of plains units 1 and 2 bear a strong resemblance to those previously mapped in mare serpentis a section of highlands crust located northwest of hellas basin thus the two major intercrater plains units are even more widespread than previously thought and therefore likely constitute important components of mars highland stratigraphy many craters in the region contain high thermal inertia deposits unit 3 that are compositionally identical to unit 2 these may have formed via volcanic infilling or may represent sedimentary materials that have been eroded from crater walls and lithified less common units include olivine and or pyroxene rich massifs and crater central peaks these are primarily found within hellas basin rim units and may represent mantle materials brought toward the surface during the hellas impact putative chloride deposits are primarily associated with olivine deficient surfaces unit 1 that may be heavily degraded occurrences of unit 2 the observations raise a variety of questions related to martian crustal evolution and alteration that may have more widespread implications outside the study region

identification of quartzofeldspathic materials on mars 1 a unique spectral component has been identified near and on the central peaks of two 30 km diameter craters in northern syrtis major these exposures are clearly visible in thermal emission imaging system themis color radiance images as well as themis and thermal emission spectrometer tes surface emissivity data both tes and themis data indicate the presence of increased 1050 1250 cm 1 8 9 5 m absorption compared to the surrounding basaltic plains and tes data also display other absorptions at 400 470 and 800 cm 1 25 20 and 12 m consistent with the presence of quartz ratio and isolated central peak spectral unit spectra match laboratory emissivity spectra of granitoid rocks composed primarily of quartz and plagioclase feldspar deconvolution results also indicate that the surface contains quartz and feldspar in addition to a high si glass and or sheet silicate component because central peak materials are brought up from depth during the cratering event the association of the quartzofeldspathic mineralogy with the central peaks of the craters indicates that the quartz bearing material was excavated from depth the occurrence in the two adjacent craters may imply a granitoid pluton of considerable extent a plausible formation mechanism for this relatively silicic material may be similar to that of terrestrial trondhjemites which do not require plate tectonics the rarity of the exposures implies that the process that formed the granitoid composition was probably not widespread the presence of quartz bearing material on mars indicates that mechanisms that produce highly differentiated magmas have been present and extends the diversity of surface compositions identified

dune morphology sand transport pathways and possible source areas in east thaumasia region mars an aeolian system located in aonia terra eastern thaumasia region consists of six dark dune fields the dune pattern suggests an organized extended sand transport system which is characterized by the presence of long sand corridors the latter connects the different ergs with potential sources the sand stored in the ergs is provided by layered materials exposed in pits and crater walls and by the ergs themselves most of the sand converges from the marginal dune fields into the central erg c the latter develops in an area of convergence of at least three different winds from the southwest the northeast and the northwest the northwesterly flows seem to postdate the other winds as suggested by the development of a complex dune pattern in the western portion of the erg c representing a successive episode of aeolian construction collectively such complex dune patterns show how dune fields could record major changes in the wind regimes of mars

comparison of the mineral composition of the sediment found in two mars dunefields ogygis undae and gale crater three distinct endmembers identified abstract the composition of two dune fields ogygis undae and the ne sw trending dune field in gale crater the bagnold dune field and western dune field were analyzed using thermal emission spectra from the mars global surveyor mgs thermal emission spectrometer tes and the mars odyssey thermal emission imaging system themis the gale crater dune field was used as a baseline as other orbital compositional analyses have been conducted and in situ sampling results will soon be available results from unmixing thermal emission spectra showed a spatial variation between feldspar mineral abundances and pyroxene mineral abundances in ogygis undae other datasets including nighttime thermal inertia values also showed variation throughout the dune field one explanation proposed for this variation is a bimodal distribution of two sand populations this distribution is seen in some terrestrial dune fields the two dune fields varied in both mineral types present and in uniformity of composition these differences point to different source lithologies and different distances travelled from source material examining these differences further will allow for a greater understanding of aeolian processes on mars

space geodetic constraints on glacial isostatic adjustment in fennoscandia analysis of global positioning system gps data demonstrates that ongoing three dimensional crustal deformation in fennoscandia is dominated by glacial isostatic adjustment our comparison of these gps observations with numerical predictions yields an earth model that satis es independent geologic constraints and bounds both the average viscosity in the upper mantle 5 x 10 20 to 1 x 10 21 pascal seconds and the elastic thickness of the lithosphere 90 to 170 kilometers we combined gps derived radial motions with fennoscandian tide gauge records to estimate a regional sea surface rise of 2 1 0 3 mm year furthermore ongoing horizontal tectonic motions greater than 1 mm year are ruled out on the basis of the gps derived three dimensional crustal velocity field

lithosphere structure of europe and northern atlantic from regional three dimensional gravity modelling summary large scale 3d gravity modelling using data averaged on a 1 grid has been performed for the whole european continent and part of the northern atlantic the model consists of two regional layers of variable thickness the sediments and the crystalline crust bounded by reliable seismic horizons the seismic basement and the moho surface inner heterogeneity of the model layers was taken into account in the form of lateral variation of average density depending on the type of geotectonic unit density parametrization of the layers was made using correlation functions between velocity and density for sediments sediment consolidation with depth was taken into account offshore a sea water layer was included in the model as a result of the modelling gravity effects of the whole model and its layers were calculated along with the gravity modelling an estimation of isostatic equilibrium state has been carried out for the whole model as well as for its separate units residual gravity anomalies obtained by subtracting the gravity effect of the crust from the observed field reach some hundred mgal 10 5 ms 2 in amplitude they are mainly caused by density heterogeneities in the upper mantle a mantle origin of the residual anomalies is substantiated by their correlation with the upper mantle heterogeneities revealed by both seismological and geothermal studies regarding the character of the mantle gravity anomalies type of isostatic compensation crustal structure age and supposed type of endogenic regime a classification of main geotectonic units of the continent was made as a result of the modelling a clear division of the continent into two large blocks precambrian east european platform eep and variscan western europe has been confirmed by their specific mantle gravity anomalies 0 50 10 5 ms 2 and 100 150 10 5 ms 2 correspondingly this division coincides with the tornquist teisseyre zone ttz marked by a gradient zone of mantle anomalies in the central part of the eep over the russian plate an extensive positive mantle anomaly probably indicating a core of ancient consolidation of the eep has been distinguished to the west and to the east of this anomaly positive mantle anomalies occur which coincide with a deep suture zone ttz and an orogenic belt the urals positive mantle anomalies of the alps the adriatic plate and the calabrian arc correlating well with both high velocity domains in the upper mantle and reduced temperatures at the subcrustal layer are caused by thickened lithosphere below these structures negative mantle anomalies revealed in the western mediterranean basin and in the pannonian basin are the result of thermal expansion of the asthenosphere shallowing to near moho depths below these basins

interpretation of geoid anomalies in the contact zone between the east european craton and the palaeozoic platform i estimation of effects of density inhomogeneities in the crust on geoid undulations summary in our paper we compile a detailed 3 d velocity model of the crust for the territory of poland and investigate the effect of a 3 d density distribution in the crust on geoid undulations the major tectonic feature in the study area is the trans european suture zone tesz separating the precambrian east european craton from younger tectonic units of palaeozoic europe high resolution seismic models of the crust and upper mantle from recent controlled source experiments were interpolated into a 3 d p wave velocity model for the whole poland the model was converted to a density model assuming different equations connecting seismic velocities to densities for crustal rocks sediments and the uppermost mantle the crustal density model was used to calculate synthetic geoid undulations for the territory of poland and to estimate influence of separate layers topography sediments crust and uppermost mantle on the geoid to calculate the gravity effect of a large scale 3 d density model we developed a code based on a point mass algorithm as well as prisms algorithm that uses some easy to implement optimizations the synthetic geoid undulations were compared to an existing gravimetric quasi geoid solution the modelling showed that the difference in crustal structure between the east european platform and palaeozoic platform explains significant part of the observed geoid undulations in the study area the remained residual could be related to density inhomogeneities in the upper mantle

shear wave velocity variations in the upper mantle beneath central europe summary a new model eur s91 of shear wave velocity variations in the upper mantle beneath central europe and surrounding regions down to a depth of 670km is presented the model is derived from the inversion of the waveforms of 217 seismograms using the partitioned waveform inversion method for the seismogram in the time window from the s wave arrival to the fundamental mode of the rayleigh wave the seismograms were mostly assembled from digitally recording long period and broad band stations in europe the resulting 3 d model accurately predicts most of the observed waveforms in a wide band of frequencies body waves were fit for frequencies up to 60mhz the fundamental rayleigh mode which at high frequencies is more prone to scattering and multipathing was generally low passed at 25 mhz the resolving power of the data set depends strongly on the density of available wave paths and varies as a function of geographical position small scale heterogeneities like the subducted lithosphere in the hellenic collision zone were imaged in the region with the highest density of wave paths which indicates an optimum resolution of better than 200 km the main new results of this study pertain to the transition between east and central europe we present new information about the structure below the tornquist teisseyre zone ttz the ttz is generally regarded as the boundary between the precambrian crust of the baltic shield russian platform and the younger crust of central europe our 3 d s velocity model reveals that below this line a sharp lateral boundary extends down to at least 140 km depth with high velocities beneath the baltic shield and russian platform contrasting to the low velocities beneath the younger regions of europe the observed velocity contrast across the ttz is largest between the pannonian basin and the russian platform where it is equal to 12 per cent at 80 km depth at depths of 300 400 km the ttz is underlain by a zone of low s velocity which indicates a local thinning of the deeply rooted high velocity structure or tectosphere that underlies most of eastern europe in addition to these new results on the transition region between east and central europe a number of features that are present in other tomographic results have been confirmed the precambrian provinces of europe are characterized by high s velocities low velocities are found beneath the pannonian basin the western mediterranean northern aegean sea turkey and a small region south west of the massif central the lithosphere beneath the paris basin has a positive s velocity anomaly the resolution of all these anomalies has been established with sensitivity tests

seismic anisotropy a key to resolve fabrics of mantle lithosphere of fennoscandia abstract by merging different regional sets of body wave data we compile a relief of the lithosphere asthenosphere boundary in one of the oldest continental regions on the planet the fennoscandian shield a maximum lithospheric thickness of 200 220 km is observed in the central part of the shield and a significant thinning at its margins particularly in the southwest at the trans european suture zone fabric of the mantle lithosphere is modelled from independent sets of anisotropic parameters relative p residual spheres and shear wave splitting the mantle lithosphere of fennoscandia consists of several domains consistent olivine fabrics of dipping foliations in 3d anisotropic models of the proterozoic lithosphere or predominantly dipping lineations in models of the archean lithosphere the strength of seismic anisotropy agrees with findings from mantle xenoliths we interpret the anisotropic domains as fragments of mantle lithosphere retaining an old fossil olivine fabric which was created before these micro continents assembled we envisage an early form of plate tectonic processes such as successive subduction episodes stacking of oceanic plates and accretion of magmatic arcs such processes could create the generally observed fossil dipping fabrics of the thick precambrian mantle lithosphere starting as early as the archean

geoid anomalies and the structure of continental and oceanic lithospheres geoid anomalies in the wavelength range corresponding to spherical harmonies 6 to 30 are used to bring new constraints on the deep structure of the continental lithosphere on the nature of upper mantle seismic anomalies and on the thermal evolution of the oceanic lithosphere for the shallow lithospheric density anomalies considered here the geoid anomaly is shown to follow approximately the moment law derived from isostasy by a procedure of least squares inversion the geoid over old cratons is found to be equal to that over relatively young 50 myr oceanic lithosphere the oceanic geoid as a function of age follows the expected linear trend with flattening at old ages these results are independent of the degree at which the spherical harmonics are truncated if the tectosphere consisted only of a thick thermal boundary layer marked geoid lows with an amplitude larger than 20 m should be present over cratons in disagreement with the present observation the predicted geoid agrees with the observations if the negative density anomalies associated with a depleted peridotitic layer are present to the bottom of the lithosphere this analysis of the geoid confirms the petrological inferences that the deep roots observed seismically in the top upper mantle form a chemically differentiate reservoir the density of these cold roots is similar to that of mantle material elsewhere because the increase in density resulting from their lower temperature is largely balanced by the decrease in density caused by their depletion analysis in wavelength range corresponding to harmonics 6 to 30 in the oceans confirms that the geoid flattens at old ages and thus supports the view that an important amount of heat is transferred at the base of the lithosphere by small scale convection

crustal structure below the polish basin is it composed of proximal terranes derived from baltica abstract the large scale seismic refraction and wide angle reflection experiment polonaise 97 together with lt 7 and ttz profiles carried out with the most modern techniques gave a high resolution of crustal structure of the trans european suture zone tesz in nw and central poland the results of seismic investigations show the presence of relatively low velocity rocks vp

the lithospheric density structure of the eastern alps the three dimensional 3d lithospheric density structure of the eastern alps was investigated by integrating results from reflection seismics receiver function analyses and tomography the modelling was carried out with respect to the bouguer gravity and the geoid undulations and emphasis were laid on the investigations of the importance of deep lithospheric features although the influence of inhomogeneities at the lithosphere asthenosphere boundary on the potential field is not neglectable they are overprinted by the response of the density contrast at the crust mantle boundary and intra crustal density anomalies the uncertainties in the interpretations are in the same order of magnitude as the gravity field generated by the deep lithosphere after including the deep lithospheric geometry from the tomographic model it is shown that full isostatic equilibrium is not achieved below the eastern alps however calculation of the isostatic lithospheric thickness shows two areas of lithospheric thickening along the central axis of the eastern alps with a transition zone below the area of the transalp profile this is in agreement with the tomographic model which features a change in lithospheric subduction direction c 2005 elsevier b v all rights reserved

geologic context of in situ rocky exposures in mare serpentis mars implications for crust and regolith evolution in the cratered highlands abstract global acquisition of infrared spectra and high resolution visible and infrared imagery has enabled the placement of compositional information within stratigraphic and geologic context mare serpentis a low albedo region located northwest of hellas basin is rich in spectral and thermophysical diversity and host to numerous isolated exposures of in situ rocky material most martian surfaces are dominated by fine grained particulate materials that bear an uncertain compositional and spatial relationship to their source thus location and characterization of in situ rock exposures is important for understanding the origin of highland materials and the processes which have modified those materials using spectral thermophysical and morphologic information we assess the local and regional stratigraphy of the mare serpentis surface in an effort to reconstruct the geologic history of the region the martian highlands in mare serpentis are dominated by two interspersed surface units which have distinct compositional and thermophysical properties 1 rock dominated surfaces relatively enriched in olivine and pyroxene and depleted in high silica phases and 2 sediment or indurated material depleted in olivine and pyroxene with relatively higher abundance of high silica phases this is a major previously unrecognized trend which appears to be pervasive in the mare serpentis region and possibly in other highland areas the detailed observations have led us to form two hypotheses for the relationship between these two units either 1 they are related through a widespread mechanical and or chemical alteration process where less mafic plains materials are derived from the mafic bedrock but have been compositionally altered in the process of regolith formation or 2 they are stratigraphically distinct units representing separate episodes of upper crust formation existing observations suggest that the second scenario is more likely in this scenario plains materials represent older degraded and possibly altered basement rock whereas the rocky exposures represent later additions to the crust and are probably volcanic in origin these hypotheses should be further testable with decimeter resolution imagery and meter resolution short wavelength infrared spectra

ultrasonic velocity and attenuation measurements on basalt melts to 1500 c role of composition and structure in the viscoelastic properties viscoelastic properties of basalt melts of a wide range of composition are determined from ultrasonic compressional wave velocity vp and quality factor qp measurements in the frequency range of 3 4 22 mhz and the temperature range of 1150 1500 c the basalt samples are grouped into two types low magnesia group a containing 5 9 wt mgo and high magnesia group b containing 18 23 wt mgo the vp values of the melts determined at 1400 c are in the range 2 53 2 64 km s for group a basalts and 2 79 2 86 km s for group b basalts the relaxed low frequency velocity vr is a principally linear function of the melt density least squares fits of the data give velocity density relations vr km s 0 691 0 712 g cm3 for group a basalts and vr 0 328 0 907 for group b basalts at 1400 c the mean molecular weights m are 65 0 0 3 and 58 2 0 5 g mol for groups a and b basalts respectively suggesting that m is also a principal factor determining the melt velocity the relaxed modulus mr of the basalt melts range from 16 5 to 22 8 gpa and is also a linear function of the melt density the values of longitudinal l and volume v viscosities are calculated from the measured vp and qp and the available shear viscosity s data the viscosities and related activation energies decrease almost linearly as nbo t nonbridging oxygens per tetrahedrally coordinated cation increases

constraints on seismic velocity anomalies beneath the siberian craton from xenoliths and petrophysics high seismic vp velocity anomalies 8 7 9 0km s 1 have long been known about in regions of the uppermost mantle of the siberian craton often in association with kimberlite fields laboratory measurement of seismic properties of five xenoliths three peridotites and two eclogites from the udachnaya kimberlite under confining pressures up to 600 mpa were extrapolated to uppermost mantle p t conditions of 1500 mpa and 500 c however none of the velocities are high enough to explain the observations eclogites or peridotites are commonly considered to be the source of anomalous high velocities we prefer a peridotitic source to an eclogitic source due to the unusual chemistry and regional uniformity of eclogitic garnets required maximum velocity limitations on laboratory measurements of seismic properties of natural eclogites and purported abundance of eclogites in the lithosphere alternatively a highly depleted peridotite such as dunite or harzburgite can produce velocities high enough to match observations olivine petrofabrics in most peridotites including the three peridotites used in this study are great enough to produce the observed high velocities provided olivine petrofabrics are continuous enough and correctly oriented to be seismically detectable and the modal proportion of olivine is high there have been suggestions by other authors that the siberian upper mantle is highly depleted and that a lithosphere scale shear zone exists which may have acted to organize fabrics into segments large enough for detection anomalously high vp vs velocity ratios of greater than 1 8 are expected parallel to the olivine 100 maxima required to be present in a high velocity olivine dominated upper mantle vp vs velocity ratios can serve as a means of inferring large scale anisotropy when limited seismic data are available as in siberia 2006 elsevier b v all rights reserved

mineralogical characterization of mars science laboratory candidate landing sites from themis and tes data abstract data from the mars global surveyor thermal emission spectrometer tes and the mars odyssey thermal emission imaging system themis instruments are used to assess the mineralogic and dust cover characteristics of landing regions proposed for the mars science laboratory msl mission candidate regions examined in this study are eberswalde crater gale crater holden crater mawrth vallis miyamoto crater nili fossae trough and south meridiani planum compositional units identified in each region from tes and themis data are distinguished by variations in hematite olivine pyroxene and high silica phase abundance whereas no units are distinguished by elevated phyllosilicate or sulfate abundance though phyllosilicate minerals have been identified in all sites using near infrared observations these minerals are not unambiguously detected using either tes spectral index or deconvolution analysis methods for some of the sites small phyllosilicate outcrop sizes relative to the tes field of view likely hinder phyllosilicate mineral detection porous texture and or small particle size 15 possibly up to 40 of a high silica phase such as amorphous silica or zeolite high silica phase abundance over phyllosilicate bearing surfaces in mawrth vallis is higher than that of surrounding surfaces by 10 15 with the exception of these high silica surfaces in mawrth vallis regions examined in this study exhibit similar bulk mineralogical compositions to that of most low albedo regions on mars the msl scientific payload will thus be able to provide important information on surface materials typical of low albedo regions in addition to investigating the origin of phyllosilicate and or sulfate deposits with the exception of gale crater all of the landing sites have relatively low dust cover compared to classic high albedo regions tharsis arabia and elysium and to previous landing sites in gusev crater utopia planitia and chryse planitia

a new method for the semiquantitative determination of major rock forming minerals with thermal infrared multispectral data application to themis infrared data 1 we have developed a new method least residual iterative spectral mixture analysis lrisma to semiquantitatively determine major rock forming minerals feldspar pyroxene olivine high silica phases and quartz with multispectral thermal infrared data sublibraries of minerals are generated from a master library of minerals based on prior knowledge to produce a suite of realistic mineral end member combinations to fit the target spectra mineral abundances that correspond to the least root mean square errors best fit generally agree best with previous petrographic studies of laboratory measured rock samples and thermal infrared hyperspectral analysis of materials on the surface of mars given the greatly reduced spectral range and resolution of thermal emission imaging system themis spectra the accuracy and reproducibility of lrisma is 4 16 and 5 20 respectively while the accuracy of petrographic and previous hyperspectral studies is 5 15 lrisma can be applied to semiquantitatively refine the bulk surface mineralogy of small scale 1 km2 geologic features with high quality themis spectral data high surface temperature 260 k low atmospheric opacity total ice 0 04 and total dust 0 15 with the ultimate goal of better understanding regional geologic processes

mgs tes thermal inertia study of the arsia mons caldera 1 temperatures of the arsia mons caldera floor and two nearby control areas were obtained by the mars global surveyor mgs thermal emission spectrometer tes these observations revealed that the arsia mons caldera floor exhibits thermal behavior different from the surrounding tharsis region when compared with thermal models our technique compares modeled and observed data to determine best fit values of thermal inertia layer depth and albedo best fit modeled values are accurate in the two control regions but those in the arsia mons caldera are consistently either up to 15 k warmer than afternoon observations or have albedo values that are more than two standard deviations higher than the observed mean models of both homogeneous and layered such as dust over bedrock cases were compared with layered cases indicating a surface layer at least thick enough to insulate itself from diurnal effects of an underlying substrate material because best fit models of the caldera floor poorly match observations it is likely that the caldera floor experiences some physical process not incorporated into our thermal model even on mars arsia mons is an extreme environment where co2 condenses upon the caldera floor every night diurnal temperatures range each day by a factor of nearly 2 and annual average atmospheric pressure is only around one millibar here we explore several possibilities that may explain the poor modeled fits to caldera floor and conclude that temperature dependent thermal conductivity may cause thermal inertia to vary diurnally and this effect may be exaggerated by presence of water ice clouds which occur frequently above arsia mons

the relative density to shear velocity scaling in the uppermost mantle we perform inversions of gravity data geopotential model egm96 and seismic tomography model s16rlbm for the scaling factor which relates relative density anomalies to relative s wave velocity anomalies the gravity data and tomographic model are anti correlated below continents down to a depth of z 200 km this anti correlation is not present below oceans except for smoothness which is controlled by a damping factor no a priori information is added to the inversion data are filtered between degrees 11 and 16 of the spherical harmonic expansion this spectral window is well suited for the study of intermediate size 2000 4000 km anomalies in the uppermost mantle calculations are made separately for sub continental and sub oceanic mantle the sub continental and sub oceanic scaling factors are significantly different at depths shallower than 260 km in both cases the magnitude of is around 0 05 the sub continental scaling factor has a positive root down to z 220 km whereas the sub oceanic scaling factor yields positive values down to z 140 km only at depth shallower than 350 km models of do not depend on the damping factor or the viscosity model at depths greater than 350 km the resolution of z decreases significantly and low degrees 2 4 add information from large scale anomalies and from the lower mantle as a result the shape and values of for 2 16 and 11 16 are significantly different at depths greater than 350 km a possible explanation of the discrepancies between the sub continental and sub oceanic scaling factor is that intermediate scale anomalies are more important in the continental uppermost mantle than in the oceanic uppermost mantle 2001 elsevier science b v all rights reserved

evidence for extensive olivine rich basalt bedrock outcrops in ganges and eos chasmas mars 1 several localized outcrops of olivine enriched bedrock have been previously identified in the ganges and eos chasma area on the eastern end of valles marineris with the thermal emission imaging system multispectral images these outcrops form a layer in the walls of ganges chasma and appear to be the remnants of a once continuous unit which was mapped over 100 km in this study we further characterize the composition forsterite content of 0 68 olivine abundance 10 to 15 thermal inertia 600 jk 1 m 2 s 1 2 consistent with in place rocky material vertical dimension 60 to 220 m extent 1100 km laterally volume 9 9 104 km3 dip 0 013 ne and continuity of this layer utilizing thermal emission spectrometer hyperspectral thermal emission imaging system multispectral and mars orbiter laser altimeter elevation data morphologic data from high resolution imagery display a relatively unmantled rough and pitted surface associated with the olivine enriched material consistent with thermal inertia data four possibilities for the origin of the olivine enriched unit are 1 volcanism associated with tectonic rifting of the valles marineris system 2 a volcaniclastic flow deposit 3 an intrusive mafic sill or 4 a discrete episode in martian history during which flood lavas were erupted onto the surface the most likely origin is an eruptive event consisting of compositionally uniform flood lavas originating from a primitive mantle source region possibly associated with the initiation of tharsis volcanism this unit is one of the largest continuous compositional units found on mars and is strikingly similar to other olivine enriched deposits identified in previous studies where compositional morphologic and thermophysical similarities are observed these similarities may indicate that there was a period in early martian history where compositionally uniform and extensive olivine enriched flood basalts were erupted on the martian surface

long and short wavelengths of indian ocean geoid and gravity lows mid to upper mantle sources rapid drift and seismicity of kachchh and shillong plateau india abstract spectral analysis of the indian ocean geoid low provides depth to the large wavelength sources as 1300 700 and 340 km that are supported from the spectral analysis and the modeling of the corresponding large wavelength regional gravity anomaly with negative density contrasts at these levels the three levels coincide with the sharp changes in the gradient of the seismic velocities related to the olivine spinel transformation of successively increasing fe mg ratio as depth increases known as transition zones the first two segments are supported from continuous wavelet transform analysis of the large wavelength component of the corresponding gravity field the low density rocks in this section appear to be related to the subducted indian tethyan lithosphere that roll back and drifted southwards after subduction as inferred from tomography experiments the relatively short wavelength sources of the spectrum of the geoid data at depths of 162 and 85 km suggest sources along the lithosphere asthenosphere boundary lab under the indian continent and surrounding oceans respectively a low viscosity zone has been envisaged below 660 km discontinuity that may correspond to the low density rocks in this section which is popularly referred to as graveyards of the subducted rocks under geoid lows the subducted slab is hydrated due to dehydration from metamorphism that causes upwelling in the mid to upper mantle which is likely to set in baby plumes presence of fluid may transform part of olivine to serpentine further reducing the bulk density of rocks in this section they would make this region buoyant that appears to be responsible for the central indian ocean deformation zone with large scale folding faulting seismicity and high heat flow the same also appear to be responsible for the rapid drift of the indian plate short wavelength component of the indian ocean geoid low reflects most of the surface shallow tectonics of the region similar to the gravity anomaly providing an additional data set for this purpose kachchh and the shillong plateau inspite of being in the intra plate region are highly seismogenic that compare almost to the activity along the plate boundaries tectonics and residual geoid anomalies of the indian continent and adjoining regions suggest that the geoid highs of kachchh and the shillong plateau along the nw and the ne corners of india are connected to the geoid highs of the plate boundaries through several lineaments and faults that also show geoid highs and trends of seismic activity leading to plate boundaries geoid highs indicating high density mafic rocks suggest their connections extensions to plate boundaries indicating them to be plausibly part of diffused plate boundaries besides both these regions are affected by i prominent lithospheric flexure of the indian plate ii large scale mafic intrusions and iii interaction of proterozoic mobile belts with effects of present day himalayan orogeny that make them more vulnerable for seismic activity

the formation of infilled craters on mars evidence for widespread impact induced decompression of the early martian mantle flat floored craters have long been recognized on mars with early work hypothesizing a sedimentary origin more recently high resolution thermal inertia measurements show that these craters contain some of the rockiest materials on the planet inconsistent with poorly consolidated sedimentary materials in this study the distribution physical properties morphology and thermal inertia and composition of these craters are thoroughly investigated over the entire planet the majority of the 2800 rocky crater floors identified are concentrated in the low albedo 0 1 0 17 cratered southern highlands these craters were infilled at 3 5 ga and are associated with the highest thermal inertia values and some of the most mafic materials identified on the planet although several processes may have led to the formation of the crater floors the most likely scenario is volcanic infilling through fractures created by the impact event the primitive magma source directly results from decompression melting of the martian mantle by the removal of the crustal material excavated by the impactor volcanic infilling of craters by decompression melting appears to only have occurred in early martian history when the lithosphere was still relatively thin and the thermal gradient was high this process was widespread and responsible for the eruption of significant volumes of primitive material inside and likely outside of craters impact induced decompression melting of the martian mantle accounts for the unusual infilling of martian craters and is a widespread planetary process that has gone previously undocumented

lithospheric structure of the tornquist zone resolved by nonlinear p and s teleseismic tomography along the tor array lithospheric structure of the tornquist zone resolved by nonlinear p and s teleseismic tompgraphy along the tor array

three dimensional mapping of magma source and transport regions from seismic data the mantle wedge beneath northeastern japan we investigate the distribution of partial melt in island arc using the seismic velocity structure of the mantle wedge beneath northeastern japan the comparison of the seismic tomography with laboratory velocity data on a partially molten mantle rock yields estimates of melting zones in three dimensions we employ experimental data on the degree of partial melt in hydrous peridotite to give constraints on the melt fraction and temperature melting and magma rich zones derived from the velocity structure coincide with observed low q zones the results of the three dimensional mapping indicate that the source of magma in island arc is diapir like melting patches localized within the low velocity zones of the mantle wedge extensive volcanic activity along the volcanic front is due to the presence of vast magma rich zones just beneath the moho those melting zones in the uppermost mantle may in turn cause melting of lower crustal materials and produce felsic magma melt appears to stay at and beneath the moho where crystallization fractionation may proceed melt exists at greater depths in the back arc region which may correlate with across arc variations of chemical compositions of the volcanic rocks observed in northeastern japan we suggest that magma migration in the ductile lower crust may cause low frequency microearthquakes and magma penetration into the brittle upper crust may produce mid crustal s wave reflectors

sedimentation on a lower jurassic carbonate platform flank geometry sediment fabric and related depositional structures djebel bou dahar high atlas morocco abstract along the southern margin of the high atlas morocco carbonate platforms of lower jurassic age developed in a transtensional basin the south atlas trough complete exposure and preservation of the platform margin flank and basin of the djebel bou dahar allowed the subdivision of the slope into an upper mid and lower slope based on geometry sediment fabric and depositional structures at ca 50 m below the platform margin coral algal patch reefs and ooid sand shoals grade into the depositional slope the straight upper slope showing discontinuous bedding at angles up to 29 extends down to ca 250 m and consists mainly of poorly sorted mixtures of sand and gravel almost devoid of mud avalanching rockfall and shearing of the coarse gravelly sediment are the dominant processes readjusting the upper slope the middle and lower part of the slope profile extending down to ca 500 m below the margin is separated from the upper slope by a distinct slope break slope angles range from 19 near the slope break down to 4 8 where the slope merges with the basin plain the irregularly bedded mid slope is characterized by scouring and deposition of muddy sands and non cohesive gravelly debris flows sedimentation on the dominantly muddy concave upwards lower slope can be separated into evenly bedded shales muddy sands and mud free gravel sand mixtures deposited as debris sheets the results of this study emphasize the relationship between sediment fabric and the slope geometry of a carbonate platform flank the overall geometry internal heterogeneity and depositional structures are suggested to be strongly related to the original character of the sediment supplied to the djebel bou dahar platform flank

mosaicking of global planetary image datasets 1 techniques and data processing for thermal emission imaging system themis multi spectral data 1 the mosaicking of global planetary data sets allows for the examination of local regional and global scale processes on all planetary bodies processing techniques that allow us and other users to crate mosaics of tens of thousands of images are documented along with the associated errors introduced by each image processing algorithm these techniques e g non uniformity correction running contrast stretches line and row correlated noise removal and random noise removal were originally developed for the 2001 mars odyssey thermal emission imaging system themis infrared multispectral imager data but can be adapted and applied to other data sets by the alteration of input parameters the techniques for mosaicking planetary image data sets e g image registration blending and normalization are also presented along with the generation of qualitative and quantitative products these techniques are then applied to generate themis daytime and nighttime infrared viking context imager ctx and mars orbiter camera moc visible mosaics using a variety of input and output types at a variety of scales by creating mosaics of the same area using different data sets such as those that illustrate compositional diversity thermophysical properties or small scale morphology it is possible to view the surface of the planet and geologic problems through many different perspectives in addition to the techniques used to create large scale seamless mosaics we also present the themis daytime and nighttime relative temperature global mosaics which are the highest resolution 100m pixel global scale data sets available for mars to date

physical abrasion of mafic minerals and basalt grains application to martian aeolian deposits abstract sediment maturity or the mineralogical and physical characterization of sedimentary deposits has been used to identify sediment sources transport medium and distance weathering processes and paleoenvironments on earth mature terrestrial sands are dominated by quartz which is abundant in source lithologies on earth and is physically and chemically stable under a wide range of conditions immature sands such as those rich in feldspars or mafic minerals are composed of grains that are easily physically weathered and highly susceptible to chemical weathering on mars which is predominately mafic in composition terrestrial standards of sediment maturity are not applicable in addition the martian climate today is cold and dry and sediments are likely to be heavily influenced by physical weathering rather than chemical weathering due to these large differences in weathering processes and composition martian sediments require an alternate maturity index this paper reports the results of abrasion tests conducted on a variety of mafic materials and results suggest that mature martian sediments may be composed of well sorted well rounded spherical polycrystalline materials such as basalt volcanic glass is also likely to persist in a mechanical weathering environment while more fragile and chemically altered products are likely to be winnowed away a modified sediment maturity index is proposed that can be used in future studies to constrain sediment source paleoclimate mechanisms for sediment production and surface evolution this maturity index may also provide insights into erosional and sediment transport systems and preservation processes of layered deposits

mineralogical composition of sands in meridiani planum determined from mars exploration rover data and comparison to orbital measurements constraints on the mineralogical composition of low albedo low sulfur sands at meridiani planum are determined from mars exploration rover mer opportunity miniature thermal emission spectrometer mini tes mossbauer and alpha proton x ray spectrometer measurements results of this work show that the sand is olivine basaltic in composition with minor amounts of sulfate and a high silica phase glass or secondary amorphous silica measurements from all three instruments indicate that pyroxene is twice as abundant as olivine and that the pyroxene composition is dominated by the low calcium variety the volume abundance of olivine is constrained to be 10 15 results from detailed analyses of mer data are used to ground truth the spectral emissivity and mineral abundances derived from orbit with mars global surveyor tes data tes derived mineral abundances are within 5 of those derived from mer data which is generally within the statistical errors associated with tes derived phase abundances the agreement lends support to global and regional scale variations in mineralogical composition determined from tes data in previous studies an alternative method of least squares minimization is used for modeling the tes and mini tes data the benefits of this method are demonstrated by comparison with conventional least squares techniques previously used by tes data users

tectonic fabric of the subcontinental lithosphere evidence from seismic magnetotelluric and mechanical anisotropy abstract knowledge of anisotropy is key to our understanding of tectonic fabrics in the lithosphere and sublithospheric mantle anisotropy provides a unique constraint on the character of past and present deformation and thus is critical to our understanding of dynamics of the plate tectonic system in particular how continents with their thick lithospheric mantle roots form stabilize and interact with underlying mantle regions improved observational methods and rapid developments of geophysical inversion techniques are contributing to more realistic earth models that include various types of anisotropy and heterogeneity a more robust characterization of anisotropic parameters can be achieved by integrating complementary datasets incorporating constraints from seismology magnetotellurics geodynamics and mineral physics valid comparisons between different measures of anisotropy however require a solid understanding of the principles and limitations of the various techniques to this end we briefly summarize a new compilation of original articles with a common focus on anisotropy of continental lithosphere including theory laboratory experiments and observations that span a range of different geophysical techniques

mars global digital dune database and initial science results 1 a new mars global digital dune database mgd3 constructed using thermal emission imaging system themis infrared ir images provides a comprehensive and quantitative view of the geographic distribution of moderate to large size dune fields area 1 km2 that will help researchers to understand global climatic and sedimentary processes that have shaped the surface of mars mgd3 extends from 65 n to 65 s latitude and includes 550 dune fields covering 70 000 km2 with an estimated total volume of 3 600 km3 this area when combined with polar dune estimates suggests moderate to large size dune field coverage on mars may total 800 000 km2 6 times less than the total areal estimate of 5 000 000 km2 for terrestrial dunes where availability and quality of themis visible vis or mars orbiter camera narrow angle moc na images allow we classify dunes and include dune slipface measurements which are derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification for dunes located within craters the azimuth from crater centroid to dune field centroid referred to as dune centroid azimuth is calculated and can provide an accurate method for tracking dune migration within smooth floored craters these indicators of wind direction are compared to output from a general circulation model gcm dune centroid azimuth values generally correlate to regional wind patterns slipface orientations are less well correlated suggesting that local topographic effects may play a larger role in dune orientation than regional winds

deep structure and mechanical behavior of the lithosphere in the hangai hovsgol region mongolia new constraints from gravity modeling we investigate the deep structure and mechanical behavior of the lithosphere beneath the hangai ho vsgo l region central mongolia asia in order to explain the origin and support of large scale doming in this deforming area we propose a gravity and topography based model which accounts for constraints provided by other independent results from xenolith and tomography studies deviations of the measured gravity from the theoretical airy compensation model are examined a long wavelength low gravity anomaly is spatially correlated with low pressure and shear velocity anomalies in the mantle and with the extent of cenozoic volcanic outcrops we interpret it as a deep seated low density asthenosphere and model its effect on the bouguer gravity signal using a 600 km wide light asthenospheric body density reduction 310 kg m 33 located between 100 and 200 km north and south of the hangai ho vsgo l dome short wavelength highs and lows in the bouguer gravity field are clearly correlated with fault activity they seem to reflect opposite senses of flexure of a rigid lithosphere across two major active faults the sayan and bogd transpressional systems and are modeled by moho deflections of 10 and 5 km respectively finally a shortwavelength 200 km high amplitude 350 mgal gravity residual remains beneath the highest part of the mountain bulge namely the hangai dome based on previously published xenolith analyses we interpret it as an anomalous low density body which may represent underplated cumulates or mafic granulites at the uppermost mantle we conclude that upper mantle dynamics necessarily play an important role in the origin and evolution of the hangai ho vsgo l dome but without requiring significant thinning of the lithosphere fl 2002 elsevier science b v all rights reserved

a global isostatic gravity model of the earth the long wavelength features of the external gravity field of the earth contain the gravitational signal from deep seated lateral mass and density inhomogeneities sustained by dynamic earth mantle processes to interpret the observed gravity field with respect to mantle dynamics and structures it is essential first to remove the lithosphere induced anomalous gravitational potential which is generated by the topographic surface load and its isostatically compensating masses based upon the most recent global compilation of crustal thickness and density data and the age distribution of cooling oceanic lithosphere residual topography and gravity are calculated by subtracting the known crustal and oceanic lithosphere compensating masses and gravitational effects from the surface fields empirical admittances between residual topography and gravity are then computed to estimate the effective depths of the remaining compensating masses which are not explained by the initial data and model assumptions this additional compensation is eventually placed by adjusting the density in the uppermost mantle between the moho and on average 70 km depth with a maximum of 118 km under tibet the lithospheric mass distribution is used in a subsequent forward computation to create a global model of the lithosphere induced gravitational potential the resulting isostatic model is considered to be valid for spatial wavelengths longer than 500 km the isostatic lithosphere model field expressed in terms of both gravity and geoid heights is subtracted from the observed free air gravity field to yield a global set of 1 1 isostatic gravity disturbances and from a satellite derived long wavelength geoid to yield the isostatic residual geoid the comparison of residual mantle gravity residual topography and isostatic corrected gravity allows us to identify the main characteristics of the underlying mantle for example dynamic support by mantle flow of the north atlantic topographic high applying the isostatic correction the overall pattern of the geoid becomes smoother and the most pronounced features which are separated in the observed geoid tend to get connected to larger structures these results stress the importance of separation of the lithospheric gravitational impact for a correct interpretation of the external gravity field even in its very long wavelength constituents also the isostatic corrected geoid spectrum reveals a stronger decrease in power from degree 3 to degree 4 and degree 5 to degree 6 which is in accordance with seismological models of deep mantle structures

the minimum depth of compensation of topographic masses summary based on the recently compiled crustal thickness data it is shown that the airy heiskanen model of compensation only partly compensates the surface topographic masses to fit the external gravitational potential induced by the surface topography the pratt hayford concept of compensation has also to be considered employing the dynamical flattening of the earth the minimum depth of compensation has been estimated to be of the order of 100 150 km this means that the topographic masses are compensated throughout the earth s lithosphere at least

interpretation of geoid anomalies in the contact zone between the east european craton and the palaeozoic platform ii modelling of density in the lithospheric mantle summary we present analysis of lateral variations of density in the upper mantle in the area of contact of the precambrian east european craton eec and the palaeozoic platform pp in poland obtained by analysis of the gravimetric geoid undulations a precise 3 d density model of the crust in the study area down to a depth of 50 km discussed in the first part of this paper majdanski et al in press did not explain all features of the observed geoid this suggests that these features can be due to density inhomogeneities in the upper mantle to estimate them we performed inversion of a residual between the observed geoid and undulations caused by the 3 d density distribution in the crust basing on the assumption of local isostatic compensation and pratt hayford isostasy model the density distribution in the upper mantle was parametrized as a 40 km thick layer located above the assumed compensation depth of 140 km and subdivided into irregular blocks the boundaries of the blocks were defined according to boundaries of major tectonic units in the study area and position and shape of the most pronounced anomalies in the residual geoid a series of sensitivity tests calculated for such density heterogeneities in the upper mantle showed that they can produce geoid undulations of the order of several metres the density values in each unit were taken as model parameters for the inversion procedure and inverse problem was solved using global optimization with constraints the density variations in the upper mantle in the final model correlate well with the surface heat flow this suggests that these variations can be due to diversity in mantle temperature the trans european suture zone tesz which is a major suture separating the eec from the pp is not observed as a distinct unit in the mantle instead our study suggests continuation of the lithosphere of the eec beneath the pp and confirms subdivision of the tesz into terranes with distinctly different evolution a simple calculation shows that condition of local isostatic equilibrium is almost achieved at the assumed compensation depth with the exception of several small scale units however different loads and mass deficiencies in the lithosphere are compensated at different depth levels this proves that the lithosphere is alternation of mechanically strong and weak layers both in the crust and upper mantle and that different loads can be compensated at different depth however the total compensation of all lithospheric loads occurs in the upper mantle

lithospheric flexure and thermal anomalies plots of effective elastic thickness te of the oceanic lithosphere as a function of age when elastically deformed show a general increase in te with the square root of age although there is much scatter some of the scatter can be eliminated by correcting for the effect of finite yield strength in rocks which makes te for more sharply bent plates underestimate the true depth tm to the rheological boundary at the base of the high strength mechanical lithosphere after converting effective values te to true thicknesses tm it appears that the mechanical lithosphere is always thinner beneath islands and seamounts compared to lithosphere of similar age flexed at subduction zones from several other lines of evidence such as depth anomalies seamount subsidence and heat flow data it has been suggested that the thermal structure in plates subjected to hot spot type volcanism is reset to values appropriate for much younger lithosphere the reduction in mechanical plate thickness beneath hot spot volcanoes is also consistent with this concept of thermal rejuvenation since the strength of rocks decreases exponentially with rising temperature this dependence implies that variations in mechanical plate thickness can be used to map temperature anomalies in the lithosphere since the mechanical plate thickness depends principally upon the temperature at one depth specifically the depth at which the temperature reaches 550 600 c depending on strain rate flexural data are particularly sensitive indicators of the vertical structure of lithospheric reheating compared to quantities dependent on depth integrals of temperature such as swell height and subsidence the thermal rejuvenation hypothesis predicts that the flexural profile should mimic viscoelastic relaxation in the first 10 ma after loading if initially reheating is confined to depths close to and below the 550 c isotherm the flexural data combined with depth anomaly information for hawaii point to extremely rapid reheating localized in the lower lithosphere rejuvenation in the society islands on the other hand is compatible with slower methods of heat injection involving the entire lithospheric column

eurid a regionalized 3 d seismological model of europe abstract this paper presents a 3 d regionalized model of the european crust and mantle velocity structure down to depths of approximately 300 km the model is entirely based upon the existing geological and geophysical literature and it incorporates topographic and bathymetric features the resulting model which we call eurid european i data set consists of approximately 6400 1 d vertical structures having an average separation of about 100 km eurid is compared quantitatively with eur s91 a recent s wave velocity tomographic model obtained from body and surface wave waveform inversion zielhuis a nolet g 1994 shear wave velocity variations in the upper mantle beneath central europe geophys j int 117 695 715 it is found that the s wave velocities in eurid and in eur s91 zielhuis and nolet 1994 do not differ by more than about 4 over most of the area to validate eurid surface wave dispersion analysis is performed along some selected paths the fundamental mode group velocity curves obtained using 1 d average models derived from eurid are found in good agreement with those determined from observations broadband waveform synthetics are also calculated along the same paths and compared with the observed time series overall we believe that eurid is representative of our current knowledge of the crust upper mantle structure beneath europe and it can be used to model realistically ground motion for periods above 10 s within structurally homogeneous regions the first digital version of this structure database is available for public use

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

on the interpretation of geoid anomalies in europe with special regard to the egt profiles abstract we have studied medium wavelength geoid anomalies over europe in particular along three main egt profiles fennolora profile central profile through west germany alpine profile across the alps and the po basin in relation to the lithospheric structure for a general interpretation of the whole european area we used a simple model prescribing topography moho depth undulations and appropriate densities and applying the concept of pratt isostasy with this simple model we could explain most of the larger features in the geoid while in northern europe the crustal thickness is crucial for central and southern europe it is the combination of both topography and moho depth we found a geoid gradient of 4 06 m km for topography and 0 58 m km for moho undulations with a compensation depth of 60 km to be the best to explain the observations however also a compensation depth of 27 km for topography and 80 km for crustal thickness undulations fits the data the negative anomalies over the north sea and the po basin become even more pronounced if crustal effects are considered which means they can not be explained adequately by crustal thickness of constant density but need additional thermal or lithological effects to locally reduce the densities a remaining negative anomaly in fennoscandia of about 4 m might reflect the effect of post glacial return flow but can also be explained by increased crustal density compared to central europe along the fennolora profile the geoid undulations can be explained by the combined effect of the increased thickness of the crust and lithosphere lateral density variations in each layer are not necessary to explain the geoid observation and upper and lower crustal density is high the density decrease at the lithospheric base is small along the central profile the effect of topography together with the low density sediments in the northern german lowland already explains most of the geoid anomaly the existence of a large low velocity body in the middle crust which might be a trapped granitic intrusion is weakly supported by the geoid observation a clear decrease in density at the transition to the asthenosphere fits the geoid observation the short but structurally most complicated alpine profile is difficult to interpret geoid observations can well be explained by the effect of low compensated topography and sedimentary layers this means that isostasy in the alps demands considerable lateral intra crustal density variations and can not be mainly attributed to the moho deflection however isostasy can well be incomplete across the alps two seismically detected crustal bodies penetrating into the upper mantle are best compatible with the geoid observation if their density is around 3 g cm 3 which agrees with an eclogitic composition of these bodies

2 d seismic tomographic and ray tracing modelling of the crustal structure across the sudetes mountains basing on sudetes 2003 experiment data the seismic data obtained during sudetes 2003 experiment are analysed and detailed crustal structure for profiles s02 s03 and s06 is presented using three different 2 d techniques 1 smooth tomography of refracted waves travel times 2 ray tracing of reflected and refracted waves and 3 joint velocity and depth of reflector tomographic inversion in spite of different interpretation techniques used the models of the crustal structure show common characteristic features the low velocity vp 4 km s sedimentary layer was documented in the northeastern part of the study area the topmost basement has in general a velocity of 5 8 6 0 km s and velocities at ca 20 km depth are 6 15 6 25 km s the strong reflecting boundaries were found at 20 23 and 25 28 km depth with a velocity contrast about 0 4 km s and the highest velocities in the lowermost crust are 6 8 7 2 km s in general the crust of the bohemian massif is slightly thicker 33 35 km than in the northern part of the area velocities beneath moho are relatively low of 7 95 km s on the basis of well recorded reflected waves mantle reflectors were discovered in the depth interval ca 40 70 km apart of new results for the geology and tectonics of the area some conclusion could be made about different techniques used in the 2 d case the clasical ray tracing method with using all correlated phases gives the most adequate model of the structure because of full manual control of the model creation the smooth first arrival travel times tomography although very fast is not satisfactory enough to describe the complex structure so the best candidate in 3 d case seems to be travel time tomography for both refracted and reflected waves in multi layers models

crustal structure across the tesz along polonaise 97 seismic profile p2 in nw poland abstract the polonaise 97 po lish l ithospheric on set a n i nternational s eismic e xperiment 1997 seismic experiment in poland targeted the deep structure of the trans european suture zone tesz and the complex series of upper crustal features around the polish basin one of the seismic profiles was the 300 km long profile p2 in northwestern poland across the tesz results of 2d modelling show that the crustal thickness varies considerably along the profile 29 km below the palaeozoic platform 35 47 km at the crustal keel at the teisseyre tornquist zone ttz slightly displaced to the northeast of the geologic inversion zone and 42 km below the precambrian craton in the polish basin and further to the south the depth down to the consolidated basement is 6 14 km as characterised by a velocity of 5 8 5 9 km s the low basement velocities less than 6 0 km s extend to a depth of 16 22 km in the middle crust with a thickness of ca 4 14 km the velocity changes from 6 2 km s in the southwestern to 6 8 km s in the northeastern parts of the profile the lower crust also differs between the southwestern and northeastern parts of the profile from 8 km thickness with a velocity of 6 8 7 0 km s at a depth of 22 km to ca 12 km thickness with a velocity of 7 0 7 2 km s at a depth of 30 km in the lowermost crust a body with a velocity of 7 20 7 25 km s was found above moho at a depth of 33 45 km in the central part of the profile sub moho velocities are 8 2 8 3 km s beneath the palaeozoic platform and ttz and about 8 1 km s beneath the precambrian platform seismic reflectors in the upper mantle were interpreted at 45 km depth beneath the palaeozoic platform and 55 km depth beneath the ttz the polish basin is an up to 14 km thick asymmetric graben feature the basement beneath the palaeozoic platform in the southwest is similar to other areas that were subject to caledonian deformation avalonia such that the variscan basement has only been imaged at a shallow depth along the profile at northeastern end of the profile the velocity structure is comparable to the crustal structure found in other portions of the east european craton eec the crustal keel may be related to the geologic inversion processes or to magmatic underplating during the carboniferous permian extension and volcanic activity

crustal structure of the trans european suture zone region along polonaise 97 seismic profile p4 1 the large scale polonaise 97 seismic experiment investigated the velocity structure of the crust and upper mantle in the trans european suture zone tesz region between the precambrian east european craton eec and paleozoic platform that comprises terranes added during the caledonian and variscan orogenies 530 370 and 370 225 ma respectively this experiment included 64 shots recorded by 613 seismic stations during two deployments very good quality data were recorded along five profiles and the longest and most important one p4 is the focus of this paper clear first arrivals and later phases of waves reflected refracted in the crust and moho were interpreted using two dimensional 2 d tomographic inversion and ray tracing techniques the crustal thickness along the profile varies from 30 35 km in the paleozoic platform area to 40 km below and due northeast of the tesz to 43 km in the polish part of the eec and to 50 km in lithuania the paleozoic platform and eec are divided by the polish basin so the upper crustal structure varies considerably in the area of the polish basin the p wave velocity is very low vp 6 1 km s down to depths of 15 20 km indicating that a very thick sedimentary sequence is present we suggest two possible tectonic interpretations of the velocity models 1 baltica indented avalonia obducting its upper crust and underthrusting its lower crust in a tectonic flake structure and 2 a rifted margin of baltica underlies the polish basin this model is similar to other interpretations of seismic profiles recorded in the baltic sea the second model implies that the paleozoic platform solely consists of avalonian lithosphere and the eec of baltica lithosphere it offers a simple explanation of the difference in crustal thickness of the two platforms it also implies that the caledonian and variscan orogenies in this area were relatively soft collisions that left this continental margin largely intact

the lithosphere in central europe seismological and petrological aspects abstract the lithosphere thickness in the variscan belt of central europe varies between about 60 and 150 km with typical values of 100 120 km our estimates derived from directionally independent representative p wave residuals are in good agreement with magnetotelluric determinations of a layer with increased conductivity in the upper mantle the large scale anisotropies of the subcrustal lithosphere beneath four seismological stations determined from spatial variations of relative p residuals vary between 6 5 and 15 2 for p velocities the s wave anisotropies determined from sks polarizations vary between 2 2 and 6 7 these values are in reasonable agreement with the anisotropies of peridotites determined in laboratory systematic spatial variations of the directional terms of relative residuals in dependence on azimuths and incidence angles suggest the existence of large dipping anisotropic structures in the subcrustal lithosphere the residual patterns at most stations in the saxothuringicum rhenohercynicum and in the massif central imply northwesterly orientated dips of the anisotropic structures while stations in the moldanubicum the alpine foredeep and most of the alps north of the insubric line suggest southeasterly orientated dips in our interpretation the dipping anisotropic structures may represent paleosubductions which retain olivine preferred orientations originating from an ancient oceanic lithosphere the variscides of central europe may thus represent a collision zone characterized by two systems of paleosubductions divergent relative to the suture between the moldanubicum and the saxothuringicum

surface mineralogy of martian low albedo regions from mgs tes data implications for upper crustal evolution and surface alteration 1 mars global surveyor thermal emission spectrometer mgs tes data are used to derive the modal mineralogy of spectrally distinct martian low albedo regions and to identify spatial trends in mineralogic assemblages results from this work are consistent with the major results of previous spectroscopic studies 1 plagioclase and clinopyroxene are the dominant minerals of most southern highlands regions 2 the northern plains exhibit the lowest pyroxene abundance within martian low albedo regions and 3 the highest concentrations of high silica phase s are found in the northern plains solis planum and a few southern high latitude regions low albedo regions may be classified into four units on the basis of relative abundances of plagioclase pyroxene and high silica phase s unit distributions between 45 latitude exhibit moderate correlation with distinct provinces e g syrtis major aonium sinus defined by large scale morphology elevation and to some extent surface age suggesting that the spectral and compositional differences between these units are more strongly controlled by original bedrock mineralogy than by surface atmosphere interactions and alteration syrtis major exhibits a difference in mineralogy from the surrounding highlands suggesting a differing degree of fractional crystallization assimilation or source region composition areas with thick crust near the tharsis plateau exhibit lower abundances of olivine and greater plagioclase pyroxene ratios than surrounding highland terrains suggesting that magmas in this region may have undergone increased olivine fractionation regions where surface alteration is more likely to be the primary control on observed spectral signatures are the high latitude areas 45 where globally surfaces dominated by high silica phase s are most commonly found

paleolithospheric structure revealed by continental geoid anomalies abstract lithospheric geoid anomalies record changes in elevation and potential energy experienced by continental lithosphere estimates of local isostatic equilibration and potential energy in tandem with lithosphere related geoid anomalies can be used to estimate paleolithospheric thickness providing a clearer understanding of how and why continental topography is developed we employ several simplifying assumptions about the crustal and mantle lithosphere density and structure and readily acknowledge that our results are therefore first order approximations to predict the pre orogenic structure of the lithosphere at the outset we emphasize that while this approach does not provide an exhaustive evaluation of the deformation mechanism it does serve to quantify the relative role played by the variations in the crustal and upper mantle components of the lithosphere in this way we are able to use independent measurement of lithospheric geoid anomalies current post orogenic elevation and lithospheric structure and paleoelevation information to estimate topographic development and structural support over time application of this technique to the southwestern united states indicates that the uplift of the colorado plateau is the result of processes in both the crust and mantle lithosphere and that the lithosphere of the pre orogenic southern basin and range was thinned relative to the northern basin and range and colorado plateau although we use the southwestern u s as an example this method can help constrain uplift mechanisms for any region for which the structure and geoid anomaly of the modern lithosphere is well understood