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

comparison of magnetic hysteresis parameters of unremagnetized and remagnetized limestones for white magnetite bearing mesozoic pelagic limestones from italy which carry a primary magnetization the values of mrs ms and hcr hc generally lie in the pseudo single domain psd field of the day et al 1977 plot the logarithmic plot of mrs ms against hcr hc gives a straight line r 0 814 with slope and intercept close to the empirical mixing line of parry 1982 for single domain sd and multidomain md magnetite for one of the white pelagic limestone formations maiolica formation samples with hysteresis ratios closer to the md field display increased paramagnetic susceptibility and are from the upper part of the formation characterized by increased detrital clay we therefore associate the increased md magnetite with increased detrital influx for pinkish and reddish varieties of the italian pelagic limestones the presence of hematite is manifest by high saturation fields a wide range of hcr hc and wasp waisted hysteresis loops attributed to the mixing of magnetite and high coercivity authigenic hematite the hysteresis ratios for a collection of paleozoic and mesozoic remagnetized magnetite bearing limestones from britain nevada alaska and the appalachians lie mainly outside the psd field and appear to follow a power law trend following jackson et al 1993 the high values of hcr hc and the characteristically wasp waisted hysteresis loops can be interpreted in terms of a fine grained subspherical high coercivity sd magnetite mixed with a high proportion of superparamagnetic magnetite the slope and intercept of the power law relationship for mrs ms and hcr hc in the remagnetized limestones are distinct from those observed for the italian limestones and may provide a means of fingerprinting magnetite of primary as opposed to diagenetic origin

potbellies wasp waists and superparamagnetism in magnetic hysteresis because the response of a magnetic substance to an applied field depends strongly on the physical properties of the material much can be learned by monitoring that response through what is known as a magnetic hysteresis loop the measurements are rapid and quickly becoming part of the standard set of tools supporting paleomagnetic research yet the interpretation of hysteresis loops is not simple it has become apparent that although classic single domain pseudo single domain and multidomain loops described in textbooks occur in natural samples loops are frequently distorted having constricted middles wasp waisted loops or spreading middles and slouching shoulders potbellies such complicated loops are often interpreted in oversimplified ways leading to erroneous conclusions the physics of the problem have been understood for nearly half a century yet numerical simulations appropriate to geological materials are almost unavailable in this paper we discuss results of numerical simulations using the simplest of systems the single domain superparamagnetic sd sp system examination of the synthetic hysteresis loops leads to the following observations 1 wasp waisting and potbellies can easily be generated from populations of sd and sp grains 2 wasp waisting requires an sp contribution that saturates quickly resulting in a steep initial slope and potbellies require low initial slopes the sp contribution approaching saturation at higher fields the approach to saturation is dependent on volume hence the cube of grain diameter therefore there is a very strong dependence of hysteresis loop shape on the assumed threshold size 3 we were unable to generate potbellies using an sp sd threshold size as large as 30 nm and wasp waists cannot be generated using a threshold size as small as 8 nm the occurrence of both potbellies and wasp waists in natural samples is consistent with a room temperature threshold size of some 15 nm 5 4 simulations using a threshold size of 15 20 nm with populations dominated by sp grain sizes that is with a small number of sd grains produce synthetic hysteresis loops consistent with measured hysteresis loops and transmission electron microscopic observations from submarine basaltic glass 5 simulations and measurements using two populations with distinct coercivity spectra can also generate wasp waisted loops a relatively straightforward analysis of the resulting loops can distinguish the latter case from wasp waisting resulting from sp sd behavior

permo carboniferous magmatism of the northeast german basin abstract variscan continent continent collision in central europe was followed by a period of syn to late tectonic magmatism involving the extrusion of large volumes of permosilesian age volcanic rocks particularly in the northeast german basin the volcanic suite up to ca 2000 m thick comprises rhyolites acid and basic andesites and tholeiitic and alkali basalts tectono geochemical analysis in conjunction with volume calculations and petrography reveals changes in volcanic activity over time a total of five eruptive stages are recognised beginning in the stephanian and extending up into the upper rotliegend permian these include the stephanian late carboniferous andesite pre ignimbrite stage i lower rotliegend permian age explosive ignimbrite stage ii post ignimbrite stage iii late rhyolite stage iv and upper rotliegend permian age late basalt stage v in addition several volcanic centres including at least two large caldera like structures are recognised the total calculated volume for the northeast german basin volcanics is ca 48 000 km3 comprising rhyolitic rocks and ignimbrites ca 70 andesitic rocks ca 26 and basalts with cogenetic dolerites ca 4 regional variations in composition and geochemistry are related to diverse crust mantle regimes which correlate with differing positions relative to the heterogeneous basement of the variscan foredeep or within the rhenohercynian orogenic zone the crustal thickening and increasing generation depth of the mafic magmas from north to south may reflect the presence of a pre existing subduction influenced basaltic magma source

nature esr signals of quartz e center shed new light on river sediments provenance a case study in southeast margin of the tibet plateau abstract host rock samples and deposits collected from the upper yangtze river and the dadu river which both drained the southeastern tibet plateau and nature electron spin resonance esr signals of quartz e center were determined with esr spectrometry statistical analyses of the results show that nature signal intensity of quartz e center as a new indicator can be used to fingerprint the source of detrital quartz in modern river sediments firstly nature signal intensities of quartz e center both in bedrocks and its deposits show lower values less than 11 s u in granitic drainages than those in metamorphic drainage and sedimentary drainage more than 19 s u secondly nature signal intensities of quartz e center in deposits will be enhanced by sunlight bleaching from source to sink thirdly with the increasing of transportation distance accumulation nature signal intensities of quartz e center in deposits are changed according to the different mixture ratios of samples which attributed the different types of host rocks the researches indicate that nature signal intensities of quartz e center have a significantly dependence on lithology both in bedrocks and in deposits and nature signal intensities of quartz e center can reflect the mixture ratio of deposits with different types of sourced bedrocks

partly pedogenic origin of magnetic variations in chinese loess quaternary sequences of interbedded aeolian silts loess and buried soils palaeosols potentially provide one of the best terrestrial records of past climates1 5 magnetic susceptibility variations in loess and palaeosol sequences from china are strongly correlated with climate induced fluctuations of oxygen isotope ratios in deep sea sediments2 4 6 8 as an explanation of this correlation it has been suggested that the recorded variations in magnetic susceptibility depend primarily on the degree of dilution by non magnetic bulk loess constituents of a uniform magnetic assemblage derived from remote but unknown sources6 8 it has also been suggested that such a model involving changes in the accumulation rate of loess superimposed on a constant flux of magnetic particles provides a relative geological timescale through the control of loess deposition by astronomically modulated climate fluctuations7 here we report a preliminary test of this model using rock magnetic properties especially sensitive to variations in magnetic grain size our results show that palaeosols are characterized by much finer magnetic grain size assemblages than are the intervening loess units this suggests that a simple model based on constant magnetic influx and dilution by variable amounts of non magnetic loess is inadequate our magnetic measurements establish the close comparability of the fine grained magnetic minerals in the palaeosol samples to those in contemporary soils and thus point to a partially pedogenic origin for the magnetic mineral assemblages in the palaeosols

an la icp ms trace element classification of ochres in the weld range environ mid west region western australia laser ablation inductively coupled mass spectrometry la icp ms is successfully used to distinguish ochre from two nationally heritage listed aboriginal ochre mines in the mid west region of western australia wilgie mia and little wilgie the same technique is then used to test whether either ochre mine is the likely source of ochre used at archaeological sites in the local landscape the archaeological samples were retrieved from rock art and the surface of artefacts in excavated and surface contexts la icp ms offers advantages over other techniques for the geochemical characterisation of ochre including direct analysis of solid sample reduced laboratory preparation and breadth of trace element isotopes analysed this work highlights the potential for trace elemental analyses and profiling to develop an understanding of the past cultural significance of ochre from sources which are also important mythological sites

gulf of mexico tectonic history hotspot tracks crustal boundaries and early salt distribution a late jurassic mantle plume may have generated hotspot tracks on the north american plate and the yucatan penninsula tectonic block as the gulf of mexico opened ca 150 ma the tracks are identified from deep basement structural highs that have been mapped by integrating seismic refraction and gravity data they are associated with high amplitude distinctive gravity anomalies that provide the basis for a kinematic reconstruction that restores the western ends of the hotspot tracks with a 20 clockwise rotation of the yucatan block or almost one half the total rotation required to open the gulf of mexico basin the duration of track generation is estimated to have been about 8 10 m y or almost one half the total time required to open the gulf of mexico basin prior to this rotation extension of continental crust over a 10 12 m y interval was the result of approximately 22 of counterclockwise rotation and crustal thinning autochthonous salt appears to be confined to the continental flanks of the hotspot tracks confirming that salt was deposited during continental extension and not after ocean floor had begun to form a prominent gravity anomaly along the western boundary of the basin is interpreted to be produced by a marginal ridge which was created along the ocean continent transform boundary as the basin opened the eastern flank of this marginal ridge and the northernmost easternmost and southernmost terminations of the hotspot tracks are interpreted to coincide with the oceanic continental crustal boundary in the basin dale e bird consults in the oil and gas exploration industry as a potential fields specialist since 1981 his experience in the industry includes acquisition processing interpreting and marketing geophysical data including positions with aerodat world geoscience marathon oil company digicon and aero service he earned a ph d from the university of houston in 2004 and his research interests are regional geology and tectonics and the integration and interpretation of gravity and magnetic data he is a member of several local and international geological and geophysical societies kevin burke has been a professor of geology in the university of houston since 1983 having previously lived and worked in several parts of the world his main research is in tectonics the large scale evolution of planetary lithospheres his current interests include african and asian geology and the derivation of large igneous provinces from the core mantle boundary stuart a hall is a professor of geosciences specializing in the study of gravity and magnetic fields he received a b sc honors degree in physics from the university of birmingham united kingdom 1968 and a ph d in geophysics from the university of newcastle upon tyne united kingdom 1976 his current research interests are mainly focused on the use of geophysical data to investigate the development of small ocean basins and orogenic belts he is a member of the society of exploration geophysicists american geophysical union royal astronomical society and sigma xi research society john f casey is a professor of geology and chair of the department of geosciences at the university of houston specializing in structure tectonics and geochemisty he received a b a degree in geology from the university of pennsylvania in 1975 and a ph d in geology with honors from the state university of new york albany in 1980 his research has focused on the tectonics and geochemistry of midocean ridges transform faults and ophiolite bearing orogenic belts

mechanisms of formation of deep basins on continental crust in the verkhoyansk fold belt miogeosynclines and cratonic basins abstract the verkhoyansk fold belt is a wide folded area in northeastern asia a large sedimentary basin 10 15 km deep was formed there by a slow subsidence of continental crust during 1000 ma in the late proterozoic middle paleozoic there are no deformations in the sedimentary cover that could indicate significant lithospheric stretching or shortening during this slow subsidence a number of deep basins 5 15 km of the same type exist or existed in other areas they can be called cratonic basins a slow gabbro eclogite transformation in the lowermost crust that occurred in a thick cratonic lithosphere can be suggested as a mechanism for their formation several deep water basins were formed in the verkhoyansk fold belt by rapid subsidence of continental crust during 1 5 ma in the late paleozoic and early mesozoic the subsidence occurred without significant stretching or thrust loading the basins formed were strongly folded in the late mesozoic under the convergent plate motions there were many basins of the same type in the other fold belts among deep basins on continental crust only those produced by rapid subsidence were intensely folded they can be called miogeosynclines rapid gabbro eclogite transformation with the destruction of the basaltic layer may be suggested as the mechanism of their formation this probably occurred under upwelling of hydrous anomalous mantle to the base of the crust

geochemical characterization of ochre from central coastal british columbia canada the use of ochre and its presence in archaeological contexts is well documented archaeologically ethnographically and historically elemental analysis of ochre is becoming increasingly common as a method for identifying ancient quarrying and mining practices and for identifying patterns of resource use trade and exchange as this type of work has become more common it has become apparent that two critical issues need to be considered 1 the need for systematic identification of trends and patterns in ochre geochemistry using appropriate statistical analyses and 2 consideration of geographic and geologic scale in relation to ochre chemistry because ochre is a heterogeneous material relative to other raw material types it is necessary to apply multivariate and discriminant statistics to differentiate geochemical groups within a sample set however caution must be taken when interpreting statistical results at face value local geologic and geomorphologic conditions play a significant role in ochre chemistry and need to be taken into account when interpreting analytical results the purpose of this project was to determine if geochemically distinct groups of ochre could be distinguished through neutron activation analysis naa of archaeological and geological ochres from the central coast of british columbia canada the results show that it is possible to satisfy the provenance postulate and to differentiate chemical groups through elemental characterization and using multivariate statistical methods

application of near surface seismic refraction tomography and multichannel analysis of surface waves for geotechnical site characterizations a case study in this case study two geophysical methods based on seismic waves were employed to evaluate the geotechnical properties of the soil deposits at a site for a planned wind farm regional geological information shows that the study area is mainly covered by recent alluvium which is classified as a mixture of fine sand and gravel twenty five seismic refraction surveys were carried out in the study area the acquired shot gathers were processed from which primary wave p wave and shear wave s wave velocities were derived the p wave velocities were obtained by using the seismic refraction tomography method srt while the s wave velocities were extracted by utilizing the multichannel analysis of surface waves masw technique which is established based on the dispersion characteristics of rayleigh waves seismic hazard at the site was evaluated according to the iranian code using the measured s wave velocities and the friction angles of the soil deposits were approximated using an empirical method and by making use of jaky s formula for earth pressure at rest which yielded similar values the deformation properties of the foundation soil were also estimated based on the correlations between seismic wave velocities and elastic properties of soil as well as janbu s formula for soil modulus the findings of this study may serve as references for economic and non destructive geotechnical site characterizations using seismic wave methods

paleoclimatic significance of the mineral magnetic record of the chinese loess and paleosols the origins of the magnetic susceptibility variations of the chinese loess and paleosols are explored by scanning and transmission electron microscopy of magnetic extracts and by magnetic modeling of magnetic hysteresis data to provide quantified estimates of the major magnetic components microscopy identifies several distinct size and shape characteristics in the magnetic carriers lithogenic magnetites intact and abraded dominate the coarse grained magnetic fraction the smallest of the coarse grains is 2 i m the remaining magnetic materal is ultrafine in size with two types of magnetite particles present type a particles strongly resemble soil magnetites produced by inorganic precipitation type b particles which occur rarely are probably bacterial in origin quantitative modeling of these magnetic assemblages shows that over 90 of the susceptibility variations is accounted for by the superparamagnetic magnetite component compared to the loess units the paleosols are richer in magnetite particularly of superparamagnetic size and have a threefold higher ratio of magnetite to hematite we identify pedogenic formation of magnetite as the major contributor to the loess magnetic record matching this record against other paleoclimatic records we find an extremely high correlation with the standard 18o record the chinese loess sequences record a very high resolution magnetic stratigraphy directly related to changing climate

neogene quaternary magmatism and geodynamics in the carpathian pannonian region a synthesis in the carpathian pannonian region in neogene times westward dipping subduction in a land locked basin caused collision of two lithospheric blocks alcapa and tisia with the southeastern border of the european plate calc alkaline and alkaline magmatism was closely related to subduction rollback collision and extension from the spatial distribution of the magmatic activity four segments can be defined western segment magmatism occurring on the alcapa block central segment magmatism occurring on both alcapa and the tisia blocks south eastern segment and interior segment both on the tisia block most calc alkaline magmatism in the region resulted from melting of a heterogeneous asthenospheric mantle source modified by addition of fluids and sediment assimilation and fractionation processes at shallow crustal levels occurred in most of the segments strongly masking the deeper source processes long term subduction rollback and or delamination led to contamination of the asthenosphere beneath the western segment here large volume partial melts of the contaminated mantle caused underplating and crustal anatexis leading to mixing of mantle derived calc alkaline magmas with crustal melts in the central segment calc alkaline magmas were formed by subduction and rollback followed by back arc extension and slab breakoff avariable mantle source is indicated in the back arc setting and larger amount of fluid induced metasomatism source enrichment and assimilation nearer to the trench in the interior segment evolution from typical calc alkaline magmas to adakite like ones was related to extension due to fast rotations and transtensional tectonics here calc alkaline magmas formed by decompression melting of a heterogeneous crust mantle lithosphere while adakite like melts resulted from fliud dominated melting of the lithosphere along the south eastern segment slab breakoff was responsible for the generation of typical calcalkaline magmas but in the extreme south of the segment shallow level tearing of the slab followed breakoff strike slip tectonics allowed the rise of hot asthenosphere and generation of adakite like magmas via slab melting along the torn edge of the east european plate alkalic basaltic volcanism with an oib like asthenosphere source followed the calc alkaline stage

crustal scale pop up structure in cratonic lithosphere dobre deep seismic reflection study of the donbas fold belt ukraine the dobre project investigated the interplay of geologic and geodynamic processes that controlled the evolution of the donbas fold belt ukraine as an example of an inverted intracratonic rift basin a deep seismic reflection profile provides an excellent image of the structure of the donbas fold belt which is the uplifted and compressionally deformed part of the late paleozoic pripyat dniepr donets basin both the effects of rifting and those of later structural inversion are recognized in the seismic and geologic data the interpretation of the reflection data shows that the inversion of the donbas fold belt occurred at the crustal scale as a mega pop up which involved a major detachment fault through the entire crust and an associated back thrust the dobreflection image provides a simple concept of intracratortic basin inversion the crustal pop up being uplifted and internally deformed the association of such a structure with inverted intracratonic basins such as the donbas fold belt implies brittle deformation of relatively cold crust

evolution of the northeast german basin inferences from a 3d structural model and subsidence analysis abstract a 3d structural model of the northeast german basin was evaluated with special emphasis on its evolution as an intracontinental depression the study includes investigations on subsidence history and structural setting of the basin thickness evolution and calculated tectonic subsidence volumes of permian to quaternary sediments in the northeast german basin indicate that the subsidence history was related to five stages of basin evolution which differ in their subsidence mechanisms for the initial rift phase in the late carboniferous to early permian a dominant thermal event and subordinate horizontal stresses were indicated by thickness variation evolution and by structural evidence the main part of basin subsidence occurred in a nw se oriented basin in the subsequent phase of thermal relaxation with maximum subsidence from early permian rotliegend to middle triassic muschelkalk from middle triassic the thermal subsidence pattern was superposed by further tectonic events in the middle triassic regional extension led to a reconfiguration of the southern part of the basin where new nne ssw trending troughs rheinsberg and gifhorn troughs developed in the jurassic the northwestern part of the basin was uplifted while in the south the keuper subsiding areas continued to sink and nw se trending depressions related to salt margins became important differentiation continued into cretaceous times when regional compression caused uplift of the southeastern part of the basin and basin margins a final subsidence phase occurred in the cenozoic this was accompanied by intensive salt movement recent basin configuration reflects the superposition of structural elements resulting from different evolution stages the main structural characteristics of the basin are 1 a vertical tectonic zonation in a pre zechstein succession which lacks significant internal structures and a strongly deformed post zechstein succession which was decoupled due to the thick zechstein salt and 2 a marked asymmetry of the basin with a shallow northern slope and a steep bounding fault at the southern margin elbe fault system the northwestern part of the basin shows the structural properties of an intracratonic sag basin with persisting subsidence and with minor salt mobilisation in contrast initial structures in the southeastern part are strongly overprinted by younger tectonic events including middle triassic to jurassic extension late cretaceous inversion and late to post cretaceous salt movements tectonic elements that deform the whole sedimentary succession are restricted to the basin s southern eastern and northeastern margins where salt thickness decreases combined volumetric and backstripping investigations show that 2 3 of the total subsidence was induced by the sediment load and 1 3 was caused by tectonics the tectonic subsidence history varies laterally across the basin while tectonic subsidence curves in the northwestern part of the basin show fast subsidence during the permian and early triassic decreasing exponentially with time subsidence curves in the southeastern part indicate repeated tectonic activity however the tectonic subsidence volume created during permian to late triassic is significantly higher than the tectonic subsidence during younger phases of basin history

current plate velocities relative to the hotspots incorporating the nuvel 1 global plate motion model nuvel 1 is a new global model of current relative plate velocities demets et al 1990 which differ significantly from those of prior models here we incorporate nuvel 1 into hs2 nuvel1 a new global model of plate velocities relative to the hotspots hs2 nuvel1 was determined from the hotspot data and errors used by minster and jordan 1978 to determine am1 2 which is their model of plate velocities relative to the hotspots am1 2 is consistent with minster and jordan s relative plate velocity model rm2 here we compare hs2 nuvel1 with am1 2 and examine how their differences relate to differences between nuvel 1 and rm2 hs2 nuvel1 plate velocities relative to the hotspots are mainly similar to those of am1 2 minor differences between the two models include the following 1 in hs2 nuvel1 the speed of the partly continental apparently non subducting indian plate is greater than that of the purely oceanic subducting nazca plate 2 in places the direction of motion of the african antarctic arabian australian caribbean cocos eurasian north american and south american plates differs between models by more than 10 3 in places the speed of the australian caribbean cocos indian and nazca plates differs between models by more than 8 mm yr although 27 of the 30 rm2 euler vectors differ with 95 confidence from those of nuvel 1 only the am1 2 arabia hotspot and india hotspot euler vectors differ with 95 confidence from those of hs2 nuvel1 thus substituting nuvel 1 for rm2 in the inversion for plate velocities relative to the hotspots changes few euler vectors significantly presumably because the uncertainty in the velocity of a plate relative to the hotspots is much greater than the uncertainty in its velocity relative to other plates

palaeoclimatic reconstruction by using the varvite sediments of bharatpur upper lahaul valley nw himalaya india a 6 m thick varvite profile exposed at bharatpur 77 27 e 32 48 n altitude 4692 m in the nw himalaya was investigated to understand the past climatic signatures during the late quaternary period the radiocarbon chronology brackets the varvite sedimentation between 24 3 and 7 2 ka bp and the sedimentary sequence is bounded by river born gravel at the top and glacial outwash at the bottom the proxies used were lithology chronology ams radiocarbon dating geochemical analysis loss on ignition loi and mineral magnetism other parameters e g chemical index of alteration cia chemical index of weathering ciw al2o3 sio2 fe2o3 cao mgo and al na ratio were also used based on the combined data set six phases of warm and cold climatic conditions are reconstructed the mean cia ciw and al na ratios reveal that the sediments were incorporated from sedimentary rocks by moderate silicate chemical weathering process based on the available chronology the basal most glacial outwash event can be estimated as ca 24 3 ka bp and the laminated section shows continuity of sedimentation from the late quaternary to holocene the period between ca 24 3 and 22 6 ka can be regarded as an arid phase from ca 22 6 20 5 ka bp a slight increase in monsoonal precipitation is observed followed by decreased precipitation from ca 20 5 to 18 ka bp the period from ca 18 to 15 7 reveals warm and humid climatic conditions we suggest that a cold event from ca 15 7 to 11 5 may correspond to the younger dryas yd which in turn is followed by a phase of maximum moisture of the holocene climate optimum hco ca 11 5 7 2 ka bp in the study area the increased cia during deglaciation and hco suggest high chemical weathering whereas the lgm last glacial maximum and yd are represented by the low cia the observed climatic phases events are in agreement with the records from other parts of the himalaya

crustal model for the middle east and north africa region implications for the isostatic compensation mechanism summary we present a new 3 d crustal model for the middle east and north africa region that includes detailed topography sediment thickness and moho depth values the model is obtained by collecting integrating and interpolating reliable published sedimentary rock thickness and moho depth measurements in the middle east and north africa region to evaluate the accuracy of the model the 3 d gravity response of the model is calculated and compared with available observed bouguer gravity anomalies in the region the gravity modelling shows that the new crustal model predicts large portions of the observed bouguer anomalies however in some regions such as the red sea and caspian sea regions where crustal structure is relatively well determined the residual anomalies are of the order of a few hundred milligals since the new crustal model results in large residual anomalies in regions where reasonably good constraints exist for the model these large residuals cannot simply be explained by inaccuracies in the model to analyse the cause of these residuals further we developed an isostatically compensated airy type moho depth model and calculated its gravity response isostatic gravity anomalies are in nearly perfect agreement with the observed gravity values however the isostatic model differs significantly from the new 3 d crustal model if isostasy is to be maintained crustal and or upper mantle lateral density variations are needed to explain the large observed gravity residuals

on the origin of the southern permian basin central europe abstract a detailed study of the structural and stratigraphic evolution of the southern permian basin during latest carboniferous to early jurassic times supported by quantitative subsidence analyses and forward basin modelling for 25 wells leads us to modify the conventional model for the rotliegend zechstein development of this basin the late permian early jurassic tectonic subsidence curves are typical for a permian to early triassic extensional stage that is followed by thermal subsidence however a purely extensional model is extremely problematic because active faulting during this time is minor and generally hard to document using inverse techniques to model the subsidence curves we quantitatively show that a significant component of late permian and triassic tectonic subsidence can be explained by thermal relaxation of early permian lithospheric thinning and by delayed infilling of paleo topographic depressions that developed during the early permian in this interpretation stephanian autunian wrenching resulted in thermal destabilisation of the lithosphere deep fracturing of the crust disruption and erosion of its sedimentary cover and regional uplift of the area of the future southern permian basin upon termination of wrench tectonics and associated volcanism towards the end of the autunian the southern permian basin began to subside in response to thermal contraction of the lithosphere the evolving basin was isolated from the world oceans and had subsided possibly up to some 700 m below their level at the beginning of upper rotliegend sedimentation after catastrophic flooding of this paleo topographic depression at the beginning of the zechstein changing sea level sedimentation and subsidence rates remained essentially in balance although the effects of triassic rifting overprinted parts of the southern permian basin its overall subsidence pattern persisted well into the jurassic in contrast to the remainder of the southern permian basin permian and triassic crustal extension contributed significantly to the subsidence of the polish trough

sedimentary evidence for a rapid kilometer scale crustal doming prior to the eruption of the emeishan flood basalts biostratigraphic and sedimentologic investigations in 67 sections have been carried out for the middle permian maokou formation that immediately underlies the emeishan flood basalts in southwest china the results suggest a domal crustal thinning before the emplacement of the emeishan large igneous province variably thinned carbonates in the maokou formation are capped by a subaerial unconformity which is generally manifested by karst paleotopography paleoweathering zone or locally by relict gravels and basal conglomerates provenance analysis indicates that these gravels and conglomerates were mainly derived from the uppermost maokou formation therefore the stratigraphic thinning likely resulted from differential erosion due to regional uplift iso thickness contours of the maokou formation delineate a subcircular uplifted area in accordance with the crustal doming caused by a starting mantle plume as predicted by experimental and numerical modeling the duration of this uplift is estimated to be less than 3 myr and the magnitude of uplift is greater than 1000 m the sedimentary records therefore provide independent supporting evidence for the mantle plume initiation model for the generation of the emeishan flood basalts

a comparison of different magnetic methods for determining the relative grain size of magnetite in natural materials some results from lake sediments abstract a new rapid method for identifying relative grain size variations in magnetic involves the parameter anhysteretic susceptibility arm i e specific arm obtained in a 1 oe steady field which is particularly sensitive to the single domain sd and small pseudo single domain psd grains of the finer magnetite fraction a second parameter low field susceptibility is relatively more sensitive to the coarser magnetite fraction larger psd and smaller multidomain md grains we can then obtain a measure of the ratio of coarse to fine grain magnetite for large numbers of samples by plotting arversus a simple idealized model based on sized magnetite samples is proposed to explain the use of the armversus plot for detecting relative grain size changes in the magnetic content of natural materials the sediments of three lakes that contain magnetite or a similar magnetic carrier and have a wide range of values of arm and are used to test the model the model is used to interpret the magnetic variations observed and the interpretations are supported by high field hysteresis measurements of the same sediments the combination of the high field hysteresis method of day et al 1 and the arm vs method is a powerful technique allowing the rapid identification of both the relative grain size and domain state for large numbers of samples containing magnetite the armvs method should be used as an intial means of identifying distinct groups of samples the high field hysteresis method should then be applied to a few representative samples from each group to confirm the initial interpretation

a combined visual geochemical approach to establishing provenance for pegmatite quartz artifacts a technique for establishing source provenance for pegmatite quartz artifacts was developed using a quarry sample from the churchill river basin of northern manitoba and saskatchewan secondary ion mass spectrometry sims was used to quantify ti ge th and u trace element concentrations and pb isotope ratios coupled with qualitative visual characteristics to distinguish between pegmatite quartz from different archaeologically exploited sources in the churchill river basin region the technique was also applied to a small sample of quartz artifacts recovered from sites in and around the study area in a preliminary attempt to assign or rule out raw material provenance to characterized sources

characterisation of soils by mineral magnetic measurements processes of iron mineral authigenesis diagenesis and dissolution in interaction with primary inputs of iron minerals act to produce vertical differentiation of soil magnetic properties thus magnetic iron oxides in common with other iron forms may both respond to and reflect soil forming processes investigation of the degree of detectable and persistent magnetic differentiation within different soil materials can provide insights into the nature and direction of distinct sets of soil processes evidence of clear association between magnetic variation and discrete types of soil environment also has applied significance in several areas of environmental study for example the observed magnetic variation can be used to discriminate between individual soils and soil horizons for the purposes of soil surveying sediment tagging and tracing and empirical modelling of source sediment linkages this paper reports the use of mineral magnetic techniques to characterise the iron oxide assemblages within soils of varying type and provenance the effect of different pedogenic regimes have been investigated through measurement of a range of magnetic parameters including magnetic susceptibility frequency dependent susceptibility and anhysteretic and saturation remanences contrary to current pedological thought but in accord with other magnetically based studies e g mullins the presence of magnetite maghemite typically of superparamagnetic single domain grain size within soils has been found to be an extremely widespread phenomenon its contemporary neoformation within the soil environment is inferred however the input of artificially generated ferrimagnetic material is indicated for one of the magnetically enhanced soils examined here and the possibility of extraneous sources of magnetite in topsoils should be considered before pedogenic processes of magnetic enhancement are inferred from the data presented discrimination of industrially derived magnetic particles appears possible on the basis of their very low levels of frequency dependent susceptibility fd low anhysteretic remanence arm and dissociation from the finer clay sized not the formation but the active dissolution of ferrimagnetic minerals is indicated for soils affected by the processes of gleying and podsolisation eluvial horizons of podsolised profiles demonstrate almost total loss of detectable magnetic content variations in the form of the iron reprecipitated in the underlying illuvial layers may reflect differences in the pedological characteristics of these horizons within gleyed waterlogged soils processes of magnetite dissolution appear to be grain size specific preferential reduction of those grains of ultrafine superparamagnetic and fine single domain magnetic grain size is indicated where soil forms a major contributor to catchment sediment loads this has significance in the area of source sediment modelling soil derived from permanently wet or highly leached catchment areas is unlikely to contribute to peaks in the magnetic content of deposited sediments further only those erosional processes that operate at a faster rate than those of magnetic depletion will have the capacity to produce peaks in sediment ferrimagnetic concentrations such as have been observed within the historical magnetic record

pleistocene climates in china dated by magnetic susceptibility the magnetic susceptibility of loess and interbedded soils in central china varies with the degree of pedogenesis and serves as a proxy measure of climate the concentration of magnetic minerals in the sediment is inversely proportional to sedimentation rates throughout the brunhes epoch susceptibility measurements combined with the reversal stratigraphy provide a time scale that is independent of astronomic chronology on this scale the susceptibility record closely parallels the oxygen isotope fluctuations in deep sea sediments suggesting a close interdependence of the chinese dust falls the volume of land based ice and global climate

oxygen isotope ratios in quartz as indicators of the provenance of archaeological ochres the oxygen isotope ratios of fine grained quartz extracted from ochre samples can provide an indicator of ochre provenance a pilot study on a small series of red ochres from central australia shows that ochres from different geological provinces can be distinguished using this technique oxygen isotope ratios of fine grained quartz could be used in conjunction with other geochemical methods either to verify the regional provenance of an ochre or to screen a collection for material of exotic origin

the magnetic susceptibility of sedimenting material trapped in lough neagh northern ireland and its erosional significance1 the magnetic susceptibility of sedimenting material trapped at two sites in lough neagh has been measured over 1 year the magnitude of susceptibility in one of the traps correlates with rainfall in the catchment suggesting a link between channel erosion and the magnetic properties of eroded sediment

the timan pechora basin northeastern european russia tectonic subsidence analysis and a model of formation mechanism abstract we study the tectonic subsidence of the timan pechora basin by using a number of exploration wells and lithologic stratigraphic sections along deep seismic sounding profiles the tectonic analysis reveals a rapid phase of subsidence in the late devonian followed by a slower one we suggest a two phase model of persistent subsidence in the basin 1 in the ordovician 505 438 ma b p and 2 in the silurian 438 408 ma b p the thinning of the lithosphere beneath the basin due to these rift phases led to the uplift of the asthenosphere and to partial melting we explain the vertical motions of the crust by a magmatism eclogitization model the formation mechanism includes accumulation of magmatic melt below the lithosphere asthenosphere boundary in the early middle devonian a phase transformation of magmatic material to eclogites during the cooling and a flow in the uppermost mantle induced by the evolved heavy bodies since the late devonian we construct a two dimensional numerical model of the flow in the asthenosphere compute this flow and describe the resulting changes in surface topography the model is in keeping with observed gravity seismic and subsidence data using the results of tectonic subsidence analysis and the model we interpret the geodynamic evolution of the timan pechora basin and discuss the effect of eclogitization in the uppermost mantle on the basin development

dobrefraction 99 velocity model of the crust and upper mantle beneath the donbas foldbelt east ukraine abstract the donbas foldbelt df is the uplifted and deformed part of the up to 20 km thick dniepr donets basin ddb that formed as the result of rifting of the east european craton eec in the late devonian uplift especially of the southern margin of the basin occurred in early permian times in a trans tensional tectonic stress regime while folding and reverse faulting mainly occurred later mainly during the late cretaceous a seismic refraction wide angle reflection survey was carried out in 1999 dobrefraction 99 to complement existing deep seismic sounding dss data from the area that did not record significant pn phase arrivals because of insufficient maximum offset dobrefraction 99 comprised some 245 recording stations along a line of 360 km length with 11 in line shot points as well as a 100 km away parallel 190 km long subsidiary fan profile the main profile runs between the shores of the azov sea in the south to the ukraine russia border in the north across the azov massif ukrainian shield the foldbelt and the voronezh massif particular scientific targets include the nature of the crust mantle transition and the geometry of crustal upper mantle structures related to rifting and subsequent basin inversion tomographic inversion as well as ray trace based velocity modelling has been carried out the velocity signature of the sedimentary basin itself is well resolved indicating an asymmetric form with a steeper basement surface in the south than in the north and a total thickness of about 20 km a thick 10 km high velocity 6 9 km s lower crustal body lies beneath the rift basin itself offset slightly to the north compared to the main basin depocentre likely related to the rifting processes velocities in the crust below the ukrainian shield south of the foldbelt are in general higher than beneath the voronezh massif to the north the moho displays only slight topography around a depth of 40 km along the profile

dniepr donets rift deep structure and evolution from dss profiling abstract forward modelling has been applied to refraction and wide angle reflection traveltime data along two profiles crossing the intracratonic dniepr donets rift ddr a devonian sedimentary basin located in the southwestern part of the eastern european platform between the ukrainian shield and the voronezh massif the 2 d p wave velocity models show that the crystalline crust beneath the rift basin is thinner and characterised by higher velocity values of almost 1 0 km s than beneath the shield differences along the strike of the ddr are also indicated the two profiles cross the dniepr and donets segments of the ddr and reveal respectively sedimentary infill thickness of 7 and 20 km and crystalline crustal thicknesses of 31 and 17 km in both cases the crystalline crust comprises two distinct velocity layers beneath the dniepr basin the moho lies at 38 km and the upper mantle velocity is 8 4 km s in the donets region the crustal layers are underlain by velocity boundaries at depths of 37 and 42 km with velocities of 7 6 and 8 0 km s respectively the velocity models are interpreted to indicate that a key process in the formation and evolution of the ddr was the exchange of material between the crust and uppermost mantle it is hypothesised that the extended and faulted pre rift shield crust was intruded by mantle melts during rifting and that crust mantle material exchange may also have occurred during the subsequent cooling and subsidence stage of development rifting was less intense in the dniepr segment of the ddr compared to the donets to explain other differences in uppermost mantle structure between the two segments of the ddr it is postulated that density reduction of some portion of the donets subcrustal mantle occurred in response to compressional deformation and inversion during the permian uralian orogeny

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

mechanism of formation of hydrocarbon basins the west siberia volga urals timan pechora basins and the permian basin of texas abstract many authors suggest that a large role in the formation of hydrocarbon basins is played by stretching or thrust loading our previous analysis artyushkov and baer 1983 1984a b 1986 has revealed a large number of deep basins on continental crust in fold belts that were formed by rapid subsidence without significant stretching or thrust loading this paper shows that the hydrocarbon basins of west siberia volga urals timan pechora and the permian basin in texas pertain to the same basin type water loaded basins 0 3 0 5 km deep were produced in these regions by rapid subsidence in 1 ma shallow water and deeper water strata cover the same area in the basins which precludes significant stretching during the subsidence there was no folding in the adjacent regions ai the epochs of the subsidence which precludes thrust loading a short duration of the subsidence precludes a significant role of thermal relaxation rapid subsidence was commonly preceded by slight crustal uplift in the volga urals and timan pechora it was also preceded by slight volcanism we suggest destruction of the lower crust under asthenospheric upwelling to the base of the crust as a cause of rapid subsidence the asthenospheric upwelling strongly increases the heat flow which ensures hydrocarbon maturation at shallow depth activization of local tectonic movements from crustal heating occurs after rapid subsidence which produces numerous traps for hydrocarbons deposition of highly organic rocks good source rocks and the formation of reefs and or clinoforms good reservoirs commonly occur after rapid subsidence deposition of shales and evaporites good seals takes place in deeper water basins formed by rapid subsidence diapirism of the latter rocks produces additional hydrocarbon traps the combination of all the above effects associated with rapid subsidence produces very favourable conditions for the generation and preservation of hydrocarbons almost all large hydrocarbon fields in the basins considered are located in regions of rapid subsidence there are no large fields in the adjacent sedimentary basins formed by slow subsidence although the sediment thickness is commonly high

defining fault avoidance zones and associated geotechnical properties using masw a case study on the springfield fault new zealand abstract the springfield thrust fault at dalethorpe west canterbury new zealand provides a test case to explore the correlation between shear wave velocities at a range of scales and direct field observations of distributed deformation and outcrop properties the springfield fault ruptures to the surface through hard torlesse greywacke overlain on a flight of late quaternary glacio fluvial terraces by 5 m of gravel fault slip has displaced all but the lowest terraces revealing the geometry and location of faulting we used multi channel analysis of surface waves and meter scale cross hole measurements to map shear wave velocities below the lowest apparently undisplaced terrace we correlated these surveys with geotechnical parameters measured at outcrops and investigated relationships in the laboratory both field and laboratory results indicate that the shear wave velocity of torlesse greywacke declines sharply with increasing fracture density field surveys further indicate that relatively unweathered high velocity greywacke is being exhumed in a bivergent wedge between two opposite facing thrusts the fracturing and low shear wave velocities are focused in a wide low velocity damage zone that has developed in the hanging wall of the main thrust and a smaller but similar feature in the hanging wall of the backthrust this is consistent with the geomorphology of the site our correlations of geomorphic indicators of deformation with fault zone velocity structure provide a useful method with which to characterize the distribution of cumulative strain this type of analysis has utility for land use planning on or close to active faults especially where they are obscured by fluvial deposits

some new aspects for the modelling of isothermal remanent magnetization acquisition curves by cumulative log gaussian functions rock samples containing ferri magnetic minerals acquire an isothermal remanent magnetization irm after exposure to a direct magnetic field measuring irm b allows to produce irm acquisition curves which were modelled by cumulative log gaussian clg functions robertson and france 1994 to discriminate the different magnetic phases an approach of how to find the best model has been added to this method from the investigation of a magnetite sample it is inferred that with the method the remanence acquisition coercive force for each magnetic component in a sample can be deduced the method allows to detect minute concentrations of magnetically hard material in a predominant magnetically soft sample and vice versa it furthermore allows to extrapolate the irm behaviour of samples that do not reach saturation irm in the experiment the study of a natural hematite renders it possible that even well defined hematite may be contaminated by ferri magnetic impurities biasing the remanence acquisition coercive force of the sample towards lower values

inversion of combined surface and borehole first arrival time site characterization for the design of geotechnical structures such as deep foundations is crucial as unanticipated site conditions still represent the most common and most significant cause of problems and disputes that occur during construction surface based refraction methods have been widely used recently to assess spatial variation but one of the biggest limitations of these methods is that they cannot well characterize reverse profiles decreasing in velocity with depth buried low velocity zones or deep bedrock an addition of borehole data to surface data is expected to improve inversion results in this study the coupling of so called downhole and refraction tomography techniques using only one borehole is presented to both qualitatively and quantitatively appraise the capability of the data a global inversion scheme based on simulated annealing was investigated many synthetic and real test data sets with or without boreholes were inverted using the developed technique to obtain both inverted profiles and associated quantitative uncertainties a comparison of tomograms utilizing the combined borehole and surface data against tomograms developed using just the surface data suggests that significant additional resolution of inverted profiles at depth are obtained with the addition of a borehole the uncertainty estimates provide a quantitative assessment of the reliability of the interpreted profiles it is also found that the quantitative uncertainties associated with the inverted profiles are significantly reduced when adding a borehole in addition the inversion results of the combined data provide credible information for the design of deep foundations particularly useful in implementing the new load and resistance factor design methodology that can explicitly account for spatial variability in design parameters doi 10 1061 asce gt 1943 5606 0000587 2012 american society of civil engineers ce database subject headings radiography deep foundations simulation optimization boreholes site evaluation author keywords tomography deep foundations rock socket simulated annealing global optimization travel time

the evolution of the north german basin and the metamorphism of the lower crust in an integrated analysis metamorphic processes in the accreted crust potential field anomalies temperature field and subsidence history are summarized into a model for the development of the north german basin the model integrates observed phenomena such as the high nitrogen content in natural gases in permian sandstone reservoirs and the structure of the crust with model calculations rock density increase subsequent volume reduction and loss of volatiles during metamorphism lead to a depression at the surface of the earth the load of the sediments which will be deposited in the depression enhances the subsidence and the ongoing metamorphism the model provides an alternative to the application of existing tectonic stretching models for the explanation of the subsidence of sedimentary basins

high resolution seismic refraction method using surface and borehole data for site characterization of rocks abstract the authors have developed a new method for the analysis of seismic refraction data which can handle both surface and borehole data simultaneously the main features of the method we developed are as follows 1 the algorithm of analysis is based on the tomographic reconstruction technique and refraction data can be analyzed almost automatically after traveltime picking 2 the method is applicable to both layered velocity structures and those showing a velocity gradient with depth 3 in order to apply the seismic refraction technique to a site that has a more complex structure the method can use the data obtained from sources and receivers on the surface as well as those within boreholes simultaneously numerical and actual field examples have shown that the method can greatly improve the accuracy and the reliability of the seismic velocity models obtained by the seismic refraction method as compared to the conventional analysis methods it can also shorten the data processing time drastically and reduce the survey cost

magmatism and the geodynamics of rifting of the pripyat dnieper donets rift east european platform abstract the distribution of volcanism in the late devonian pripyat dnieper donets rift within the east european platform based upon the results of deep drilling indicates that pre existing basement structures and the major rift bounding faults played an important role in channelling the magmas towards the surface major and trace element and sr nd isotopic studies of the most primitive basic and ultrabasic magmas combined with estimates of the amount of extension 1 1 to 1 3 strongly suggest that magmatism was triggered by the upwelling of a thermally and geochemically anomalous mantle plume from the deep mantle during the late frasnian the peak of the magmatism occurred in the famennian coincident with the maximum amount of lithospheric extension magmatism rifting and domal basement uplife were contemporaneous at several localities within the eep suggesting that the thermal and geodynamic evolution of the platform could have been influenced by a cluster of mantle plumes during the late devonian

late holocene paleoenvironmental records in eastern bangladesh from lake sediments a multi proxy approach abstract lacustrine sediments in a poorly documented region regarding to lake sedimentation and paleo environments bangladesh were investigated using a multiproxy approach pukurpara lake is located in eastern bangladesh at an elevation of 360 m above sea level with a maximum water depth of 28 m an age depth model allowed us to investigate the changes in sedimentation that occurred since 850 ce the high resolution multielement analyses by micro x fluorescence scanning xrf showed multiple variations over short increments variation in the abundance of elements with depth as well the ratios of the abundance of some elements fe ti and zr rb suggested both rapid and long term changes in the origin of the material deposited which in turn suggested changes in weather conditions principal components analysis pcas mixing xrf and magnetic susceptibility data allow identifying changes in geochemical redox processes between the medieval warm period mwp and little ice age lia the drastic changes in the different proxies magnetic susceptibility diatom assemblages fresh water marine water diatom ratios abundance of fe and s and the fe ti ratio were interpreted to be the result of climate change before and after the mwp lia transition period the little ice age period being relatively wet

cautionary note on magnetic grain size estimation using the ratio of arm to magnetic susceptibility the ratio of anhysteretic remanent magnetization arm to magnetic susceptibility is widely used for rapid estimation of magnetic grain size variations on interpreting arm variations no significant influence of interactions among magnetic grains on arm acquisition is usually assumed implicitly although some previous experiments using artificial sediments and biogenic magnetites opposed this assumption our rock magnetic study of deep sea surface sediments from the pacific ocean showed that arm depends strongly on the concentration of magnetic minerals and on the r value of cisowski 1981 an index of the strength of magnetic interactions this result demonstrates that arm can be influenced significantly by magnetic interactions in natural sediments we corrected for the influence of the magnetic interactions using the observed concentration dependence of arm regional variations of arm values before the correction were geologically unnatural in terms of magnetic grain size variations previous interpretations of arm variations on magnetic grain size without consideration of magnetic interactions may not be valid

analysis of the red ochre of the el miron burial ramales de la victoria cantabria spain abstract this article analyzes the ochre associated with the human burial of magdalenian age in el miron cave that with its unique features deep red color brightness and particle size distribution is clearly differentiated from ochres in other strata of the site the most common techniques in archaeological pigment characterization studies were used binocular microscope inspection thin sections granulometry x ray diffraction xrd scanning electron microscopy sem edx x ray fluorescence xrf raman spectroscopy and inductively coupled plasma mass spectrometry icp ms the results obtained permit the characterization of special ochre in burial layer hematite with idiomorphic crystallinity its origin is completely different from the samples from outcrops inside el miron cave or obtained by prospecting in carranza valley this type of hematite has been identified on the coast in santona about 26 km from the burial given its uniqueness can be associated with some kind of ritual of the time whose roots lay in the middle palaeolithic and continued throughout the rest of prehistory

some aspects of the late and post variscan development of the northwestern german basin abstract the crust of northern germany can be subdivided into three provinces that are evident by differences in crustal density seismic velocity reflectivity magnetic characteristics thermal history and electric conductivity these provinces are limited by the elbe river and the northern foothills of the mittelgebirge during the pre and post variscan evolution the tectonic setting of northern germany has changed repeatedly each of the three recognized basement provinces differs in the timing of basement consolidation caledonian variscan the sequence of basin development during permian mesozoic and cenozoic times and the timing and intensity of magmatic activity permian cretaceous cenozoic

delineating a shallow fault zone and dipping bedrock strata using multichannal analysis of surface waves with a land streamer the multichannel analysis of surface waves masw seismic method was used to delineate a fault zone and gently dipping sedimentary bedrock at a site overlain by several meters of regolith seismic data were collected rapidly and inexpensively using a towed 30 channel land streamer and a rubberband accelerated weight drop seismic source data processed using the masw method imaged the subsurface to a depth of about 20 m and allowed detection of the overburden gross bedding features and fault zone the fault zone was characterized by a lower shear wave velocity vs than the competent bedrock consistent with a large scale fault secondary fractures and in situ weathering the masw 2d vs section was further interpreted to identify dipping beds consistent with local geologic mapping mapping of shallow fault zones and dipping sedimentary rock substantially extends the applications of the masw method

joint inversion of local regional and teleseismic data for crustal thickness in the eurasia africa plate boundary region summary a new map for the moho discontinuity eam02 in the eurasia africa plate boundary region is presented reliable results have also been obtained for the southern and eastern mediterranean basin the northern african coasts and the eastern atlantic ocean regions only occasionally considered in studies on the mediterranean region the moho topography model is derived from two independent sets of constraints information contained in the fundamental and highermode rayleigh waves obtained from waveform modelling is used to constrain the moho depth between estimates of crustal thickness taken from published reflection and refraction surveys gravity studies and receiver function analysis strong lateral variations in the moho topography have been observed in the mediterranean sea confirming the complex evolution of this plate boundary region in the west the moho discontinuity has been found at 15 20 km depth suggesting extended and at least in some locations oceanic crust while in the east the crust is on average 25 30 km thick there it is interpreted either as mesozoic oceanic or thinned precambrian continental crust covered by thick sedimentary deposits standard continental crust 30 35 km is observed along the eastern part of the northern african coast while to the west a rapid change from a relatively deep moho down to 42 km below the atlas mountain range to the thin crust of the southwestern mediterranean sea has been found the crust beneath the eastern north atlantic ocean can be up to 5 km thicker compared with standard oceanic crust 6 km the crust has been interpreted to be heterogeneous as a consequence of irregular magma supply at the mid atlantic ridge in addition serpentinization of the submoho mantle could contribute to the imaging of apparently anomalous thick oceanic crust in europe the presence of crustal roots 45 km beneath the major mountain belts has been confirmed while thin crust 25 km has been found beneath extensional basins comparing the obtained moho topography and moho depth computed assuming isostatic compensation at 60 km depth shows that most of the mediterranean and eastern atlantic region appears to be in isostatic equilibrium the large positive residuals observed for the eastern mediterranean are likely to be due to overestimating crustal thickness owing to the thick sediment deposits present

post variscan evolution of the lithosphere in the rhine graben area constraints from subsidence modelling in the area of the cenozoic rhine rift system crustal and lithospheric thicknesses range between 24 and 35 km and 60 and 120 km respectively this rift system transects the deeply truncated variscan orogen and superimposed permo carboniferous wrench induced troughs and late permian and mesozoic thermal sag basins at the time of its westphlian consolidation the variscan orogen was probably characterized by 45 60 km deep crustal roots that were associated with its rheno hercynian saxo thuringian saxo thuringian bohemian and bohemian moldanubian sutures all of which are transected by the cenozoic rhine rift system during the stephanian early permian wrench induced disruption of the variscan orogen subducted lithospheric slabs were detached causing upwelling of hot mantle material during the resulting thermal surge partial delamination and or thermal thinning of the continental mantle lithosphere induced regional uplift at the same time the variscan orogenic roots were destroyed and crustal thicknesses reduced to 28 35 km in response to the combined effects of mantle derived melts interacting with the lower crust regional erosional unroofing of the crust and on a more local scale by its mechanical stretching towards the end of the early permian the potential temperature of the asthenosphere returned to ambient levels with this regional long term thermal subsidence of the lithosphere commenced controlling the development of a new system of late permian and mesozoic thermal sag basins however the evolution of these basins was repeatedly overprinted by minor short term subsidence accelerations that reflect the build up of far field stresses related to rifting in the tethyan and atlantic domains comparison of observed and modelled subsidence curves suggests that in the area of the rhine rift system the lithosphere had equilibrated with the asthenosphere at the end of the cretaceous at depths of 100 120 km before it became thermally destabilized again by cenozoic rifting and plume related magmatism modelled subsidence curves indicate that by the end of early permian times the thermal thickness of the remnant mantle lithosphere ranged between 10 and 50 km in areas that were later incorporated into mesozoic thermal sag basins this corresponds to mid permian thermal lithosphere thicknesses of 40 80 km the geological society of london 2004

refraction and amplitude attenuation tomography for bedrock characterization trabzon case turkey abstract the purpose of this study was to characterize the geomaterials and rock quality of eocene neogene aged volcanic sedimentary rocks in northeastern pontides trabzon turkey geomaterials characterization is a basic step for constructions structural design excavation and seismic microzonation studies volcanic sedimentary rocks have a wide distribution in the trabzon and are foundation rock for many buildings and roads they are also frequently used for surface work such as road pavement refraction tomography and amplitude attenuation tomography were applied to map p wave velocities vp and attenuation coefficients to determine rock quality and construction plans a 3 d vp and map was created from parallel lines of 2 d seismic data multichannel analysis of surface wave masw was also used to determine shear wave velocities vs four boreholes close to our seismic lines were used to determine the underground structure of the layers rock quality designation rqd and weathering degree laboratory tests were conducted on cylindrical specimens obtained from the boreholes to measure ultrasonic pulse velocities upv for saturated and dry conditions of basalts we also calculated the uniaxial compressive strength ucs water saturation water absorption in weight and effective porosity of samples the results indicated the studied area consists of three layers the surface layer was classified as topsoil with vp from 0 5 to 0 8 km s and thickness from 0 8 to 4 m the second layer was weathered basalt having vp from 1 6 to 2 3 km s and a thickness 2 6 m the bottom layer was identified as slightly weathered and massive basalt vp of this bedrock ranges from 2 4 to 3 8 km s with beginning at depth of about 4 m the average vs from masw was 0 95 km s 1 values were 8 and 23 for weathered and slightly weathered or massive basalt respectively regression analysis assessing the relation among upv ucs and porosity indicated a high correlation among them the seismic velocities 1 values boreholes logs and laboratory tests show that the bedrock is shallower and rock quality is better at the northern part of the study area therefore the northern part seems more suitable for constructions the combination of masw and seismic refraction plus traveltime and amplitude attenuation tomography revealed fractured and weathered zones more reliably and with greater detail than any one method could have done

seismic tomography imaging of an unstable embankment abstract seismic tomography imaging was employed to make a diagnosis and choose a remedy for an embankment supported by a retaining wall showing clear evidence of structural instability the geometry and structural characteristics of the wall the inside geometry of cracks and the physical parameters of the underground materials were the primary objectives of the geophysical survey seismic data were acquired along two vertical sections each one delimited by the lines of the sources within an inclined borehole and of the receivers lying on the ground for each section a total of 744 travel times were inverted to obtain compressional wave velocities on a regular rectangular grid of squared cells 1 m 1 m using an inversion algorithm which is based on the simultaneous iterative reconstruction technique sirt ultrasonic tests carried out in laboratory on intact specimens together with other supplemental site information improved tomography resolution allowing global and node constraints that forced the solution of the inverse problem to match known boundary values tomography imaged two high velocity zones separated by a curved shape low velocity zone the first ones were found to be compatible with the concrete retaining wall and with the schist materials ranging from highly weathered to intact schist while the low velocity zone was interpreted as filling materials and or completely decomposed rock schist the combination of seismic tomography and laboratory measurements allowed extrapolation of important parameters over a large volume of rock mass otherwise only representative of small rock samples near boreholes it also enabled engineering characterization of subsurface rock mass providing useful and accurate information to design a remedy for the embankment

an integrated study of the ne german basin abstract the ne german basin is part of the southern permian basin south of the transeuropean suture zone tesz here we report an attempt to integrate a variety of geological and geophysical data in order to reveal the present day deep crustal structure of the ne german basin special focus is taken on detailed geological information available reflection seismic data wide angle refraction seismic data and gravity data based on this integrative approach a concise crustal model is developed which can be subject to further evaluation furthermore it is shown that the ne german basin is an outstanding feature quite different from classical basin types as the moho is flat below the basin neither a simple shear nor a pure shear extension model can be applied instead a thick high velocity lower crustal layer is present below the basin centre this high velocity lower crust is also observed in the western part of the basin and can be taken as characteristic for east avalonia results of gravity modelling indicate the presence of a high density lower crust thus supporting the wide angle data furthermore changes in crustal structure can be derived from changes in reflectivity pattern and from the gravimetric signature along the elbe fault system indicating the presence of different crustal domains north and south of the fault system an elastic plate model where the forces applied are the sediment load a vertical load at the southern margin accounting for the harz moutains and a nne ssw directed compression indicates a buckling of the crust during late cretaceous to tertiary inversion however the correlation between the observed crustal structure and the tectonic events that have affected the area remains a subject of discussion a permian thermal event affected the upper mantle and the lower crust and therefore may have modified the crustal memory with regard to caledonian and variscan events additional tectonic events affected the area during the mesozoic in conclusion it remains an open question whether the high velocity and high density lower crustal structure represents a remnant of east avalonia whether it is related to the formation of the permo triassic basin or is the cumulative result of a series of events during the palaeozoic and mesozoic

multichannel analysis of surface waves to map bedrock in many geologic settings topographic variations and discontinuities in the surface of bedrock can influence the transport and eventual fate of contaminants introduced at or near the ground surface determining the nature and location of anomalous bedrock can be an essential component of hydrologic characterization preliminary analysis of the hydrologic characteristics of a site in olathe kansas u s based primarily on borehole data alone suggested that a cluster of fractures and or an unmapped buried stream channel may influence fluid movement along the drill defined bedrock surface

the use of mineral magnetic parameters to characterize archaeological ochres the application of several magnetic parameters to ochre samples has found that they can be used to characterize samples from known ochre quarries this technique also allows the sourcing of ochre found in archaeological contexts and provides an alternative to geochemical methods of provenancing ochres simple magnetic parameters susceptibility and isothermal remanence are effective in discriminating between ochre sourced from various quarries however more sophisticated parameters are required to ascribe unknown samples to specific sources

rock magnetism of late neogene and pleistocene deep sea sediments relationship to sediment source diagenetic processes and sediment lithology we use bivariate scatter plots to illustrate variations in selected rock magnetic properties low field susceptibility anhysteretic and isothermal remanence of late neogene and pleistocene deep sea sediments from 16 sites in the arctic ocean north atlantic equatorial atlantic and north pacific ocean and the arabian sea our intention is to examine the ability of the rock magnetic properties to differentiate the sediments according to factors such as lithology geographical area and the dominant mode of terrigenous sedimentation which at these sites is via ice rafting via bottom currents or via eolian processes overall correlations between sediment magnetic properties and gross lithology is poor and factors such as the source and transport path of terrigenous sediment and detrital magnetic minerals together with the action of reductive diagenetic processes are the major controls on the magnetic properties on the bivariate scatter plots sites with major ice rafted contributions tend to have high sedimentary ferrimagnetic mineral concentrations relatively coarse ferrimagnetic grain sizes and scattered sample point distributions in contrast sites where we infer significant bottom current supply of terrigenous material have tightly grouped sample point distributions carbonate sediments in which the terrigenous component is supplied by eolian processes tend to have a broad range of magnetic mineral concentration caused by glacial interglacial fluctuations in carbonate accumulation and eolian activity sediments containing significant volcanogenic material have high concentrations of relatively coarse grained ferrimagnetic material reductive diagenesis is a significant determinant of sediment magnetic properties in high productivity areas and has the effect of preferentially removing the fine grained ferrimagnetic fraction causing a coarsening of the ferrimagnetic grain size distribution and a rise in the antiferromagnetic ferrimagnetic ratio

geophysical characterisation of a rockslide in an alpine region a combination of geophysical methods has been used for the characterisation of a rockslide area located in the graie alps nw of italy where the construction of a roadway tunnel has been planned electrical resistivity tomography ert seismic refraction tomography srt and spectral analysis of surface waves swm have been adopted to determine the overburden thickness and the geometry of the sliding surfaces the geomechanical characterisation of rock mass was performed by means of horizontal seismic profiles hsp and sonic log in a horizontal borehole the results have been calibrated by comparing the geophysical responses with the geological evidence derived from boreholes and with the movements recorded using inclinometric probe moreover borehole geophysics results were validated by the results of laboratory measurements performed on core samples the integration of geophysical and geotechnical results allowed the definition of a subsoil model for the investigated area and provided the necessary data for the design of the roadway tunnel the study shows that surface and borehole geophysical techniques could be an efficient and cost effective tool in rockslide investigations

comparison of 14c and luminescence chronologies at puritjarra rock shelter central australia abstract at puritjarra rock shelter a long comparative sequence permits detailed comparisons of luminescence and radiocarbon chronologies over 35 000 years both techniques produce self consistent chronologies for the puritjarra deposit but observed discrepancies between luminescence dates on unburnt sediments and 14c assays on charcoal are greater than reported elsewhere tl ages are generally older than 14c ages but dates converge at depths below 70 cm dating first significant human occupation of the rock shelter 35 000 years ago the discrepancies are not removed by calibrating 14c dates or adjusting tl ages for lower water content of sediments the 14c chronology is broadly supported by sedimentary or palaeobotanical evidence stone artefact typology and other archaeological data radiocarbon dates on intact hearths agree with those on detrital charcoal tl ages were arrived at using both total bleach and selective bleach methods and the latter agree with optical ages for the same samples incomplete bleaching of sediments during deposition can be ruled out incorporation of old material into the luminescence samples via in situ disintegration of local sandstone remains a possibility and will be an important issue to resolve as luminescence techniques are increasingly deployed to date archaeological deposits in rock shelters

using mineral magnetism to characterise ironworking and to detect its evidence in peat bogs an experimental approach has been used to establish whether medieval ironworking activity could be identified in peat bogs using mineral magnetic measurements the research project comprised three elements first magnetic susceptibility and remanence properties were obtained for materials from an experimental iron smelt in a furnace of medieval design and from material collected during the excavation of the medieval bloomery at llwyn du in coed y brenin snowdonia materials sampled and measured included charcoal aerial dust roasted bog ore and furnace dust a second experiment determined whether small amounts of aerial dust released from the furnace could be detected in accumulating peat samples this was achieved by sprinkling small quantities of dust on to a constructed peat core that had no detectable magnetic signature prior to the addition of the dust the application rates used were within the range expected to fall on a peat bog located close to a medieval furnace thirdly mineral magnetic measurements were made on a peat core collected close to the llwyn du bloomery the results confirm that roasted bog ore aerial dust released from and dust accumulating in the furnace after a smelt are magnetically detectable the aerial dust and roasted bog ore produced enhanced susceptibility and remanence signatures in the constructed peat core experiments peaks in irm 0 88t and hirm were measured in the llwyn du peat monolith and appear to correlate with a time when the medieval bloomery was operational the results presented here suggest that it is possible to identify evidence of past ironworking in peat bogs using mineral magnetic measurements and that the signatures remain well preserved in the peat record even after burial for several hundred years

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

mantle plumes and the metamorphism of the lower crust and their influence on basin evolution abstract since the stretching model appears to be not applicable to the subsidence of accretionary crust basins located on this crust type may have an alternative origin examples of such basins are the west siberia basin and the north german basin both basins showed intensive volcanism and magmatism during the initial phase of their development remarkably the west siberia basin is closely located to the hotspot related siberian flood basalts with a similar permo triassic age and the location of the north german basin in permian times is identical with the present day position of the tibesti hotspot in northern africa these two basins may have specific relations to hotspot heat sources of the earth s underlying mantle due to these heat sources thermal metamorphism within the lower layers of the accretionary crust may occur resulting in rock density increase and subsequent shrinkage of the affected rock volumes these shrinkage processes will lead to the development of topographic lows their filling with sediments and the subsequent start of an exponentially declining isostatic metamorphic basin subsidence in addition to the analyses of metamorphic processes potential field anomalies temperature fields and histories of subsidence have been integrated into one single model that can explain the development of the north german basin similarly the east african rift and eifel hotspots affected parts of the overriding continental plates the east african rift hotspot can be traced back to the afar flood basalts and the dniepr donets basin whereas the eifel hotspot can be linked to the north sea basin continental drift templates present day hotspot locations flood basalt areas metamorphic facies as function of temperature and crust categories are taken as published in recent literature

the southern margin of the east european craton new results from seismic sounding and potential fields between the north sea and poland abstract the extension of eastern avalonia from britain through the ne german basin into poland is in some sense a virtual structure it is covered almost everywhere by late paleozoic and younger sediments evidence for this terrane is only gathered from geophysical data and age information derived from magmatic rocks during the last two decades much geophysical and geological information has been gathered since the european geotraverse egt which was followed by the babel lt 7 mona lisa dekorp basin 96 and polonaise 97 deep seismic experiments based on seismic lines a remarkable feature has been observed between the north sea and poland north of the elbe line el the lower crust is characterised by high velocities 6 8 7 0 km s a feature which seems to be characteristic for at least a major part of eastern avalonia far eastern avalonia in addition the seismic lines indicate that a wedge of the east european craton eec or baltica continues to the south below the southern permian basin spb a structure which resembles a passive continental margin the observed pattern may either indicate an extension of the baltic crust much farther south than earlier expected or oceanic crust of the tornquist sea trapped during the caledonian collision in either case the data require a reinterpretation of the docking mechanism of eastern avalonia and the elbe odra line eol as well as the elbe fault system together with the intra sudedic faults appear to be related to major changes in the deeper crustal structures separating the east european crust from the paleozoic agglomeration of middle european terranes

a rock magnetic record of pleistocene rainfall variations at the palaeolithic site of attirampakkam southeastern india abstract attirampakkam an open air stratified palaeolithic site in southeastern india is the focus of ongoing studies to investigate the nature of lower and middle palaeolithic occupation in relation to changing pleistocene environments the paucity of faunal or palaeobotanical remains at the site required the use of rock magnetic properties lf fd fd arm sirm arm sirm sirm lf arm lf arm fd s ratio hirm and hirm irm 300mt as proxies for deciphering the palaeoenvironments and palaeoclimates of the region rock magnetic data from stratified deposits within excavated trenches show that the bulk of the sedimentation was intermittent with no subaerial exposure of sediments for long periods and points to fluctuating wetter and drier climates associated with the acheulian to late middle palaeolithic levels there is a general trend towards a wetter climate from layer 5 upwards layer 7 offers evidence of bacterial magnetite arm lf 40 and arm fd 1000 suggesting the onset of micro anaerobic environments as a result of floods greigite is indicated in layer 5 sirm lf 30 10 3 a m 1 which indicates a reducing environment layer 2 represents an arid climate higher proportion of haematite and a coarser magnetic grain size layer 1a again is indicative of an arid climate presence of calcrete magnetically hard minerals and coarser magnetic grain size results indicate that the southeast coast of india experienced a mostly dry tropical climate during the pleistocene the detected occurrence of a few notably more arid intervals did not disrupt occupation of the site by successive groups of hominins

seismic structure across the caledonian deformation front along mona lisa profile 1 in the southeastern north sea abstract seismic data from the mona lisa marine and onshore north sea acquisition for lithospheric seismic analysis project in the southeastern north sea image the caledonian deformation front cdf which is the collisional suture between baltica to the north and east and avalonia to the south and west the n s trending mona lisa normal incidence reflection profile 1 was recorded to 26 s twt coincident wide angle data were acquired on nine ocean bottom hydrophones and several onshore mobile seismographs along and off the profile the model of compressional seismic velocity shows three different crustal types a a typical three layered shield type crust below the ringkobing fyn high to the north b a highly complex transitional crust in the central part and c a two layered crust of caledonian origin to the south sharp and strong normal incidence and wide angle reflections from moho were recorded south of the caledonian deformation front in contrast to less distinct reflections further north s dipping crustal reflections from 4 to 11 s twt over 70 km horizontal distance terminate at moho and coincide with a change in the seismic velocity structure this indicates northward obduction of avalonian crust non migrated normal incidence seismic sections show crossing weak n dipping and stronger s dipping reflections to 20 s twt from the uppermost mantle we propose a tectonic model where the closure of the tornquist sea took place along a n dipping subduction zone which was later overprinted by a late or post caledonian s dipping shear zone sub moho velocities are 7 8 7 9 km s under 34 35 km thick baltica crust and 8 1 8 3 km s under 25 26 km thick caledonian crust the sub horizontal moho across the caledonian collision zone implies late or post caledonian re equilibration of the seismological moho we interpret the low velocity upper mantle 7 8 8 1 km s to the north as former baltica lower crust in eclogite facies after pressure induced metamorphism as a result of lithospheric flexure during the caledonian orogeny these rocks today appear as upper mantle that was uplifted to their present position during the middle devonian collapse of the north german polish caledonides