finite difference calculation of traveltimes in three dimensions the traveltimes of first arriving seismic rays through most velocity structures can be computed rapidly on a three dimensional numerical grid by finite difference extrapolation head waves are properly treated and shadow zones are filled by the appropriate diffractions differences of less than 0 11 percent are found between the results of this technique and ray tracing for a complex but smooth model this scheme has proven useful for earthquake location and shows promise as an inexpensive well behaved substitute for ray tracing in forward modeling and kirchhoff inversion applications

faults and folds fact and fiction abstract after reviewing the microscopic and macroscopic texture of fault zones the localisation of rupture and creep is described and the reduced strength of fault zones is investigated simple strength and viscosity models for the whole lithosphere play a major role for the geometry of fault zones compressional faults thrusts show ramp and flat structures often soling in a weak detachment zone extensional faults prefer a listric shape often turning subhorizontal and being invisible in the seismic lamellae of the ductile lower crust which according to the models is also a broad zone of detachment and decoupling faults in the lower crust are rare and restricted to strain hardened fault rocks or intrinsically rigid rocks like oceanic mafic ultramafic rocks of suture zones transient faults in the lower crust are created by rupture processes of large earthquakes some deep faults moderately dipping or flat are again observed in the rather rigid uppermost mantle the observation of folding inside the crust seems to be connected with an intermediate viscosity range and with a broad vertical transition zone where rigid reactions and ductile processes are mixed various methods of detecting faults by seismic studies are critically reviewed and some sequence of reliability is suggested impedance contrasts polarity dip thickness and multiple fault strings have to be deciphered by wavefront modelling origin and survival of faults are considered to be a consequence of tectonic and thermal evolution under specific stress systems

towards a mechanical model for the formation of the pannonian basin abstract new maps showing crustal and lithospheric thickness variations in the pannonian basin and the surrounding east alpine carpathian and dinaric mountains have been prepared on the basis of recent seismic seismologic and electromagnetic data a map presenting miocene faults of regional significance has been also constructed for the same region by using a wealth of recently available national and or more local studies it is suggested that observed crustal and lithospheric structural contrasts have been controlled primarily by neogene kinematic history of the region kinematic history is characterized by the following main patterns 1 1 indentation by adria and large scale backthrusting in the southern alps 2 2 eastward escape and extension of the eastern alps 3 3 extensional collapse in the pannonian basin area 4 4 formation of broad wrench fault systems along strike in the dinarides and southern carpathians and the western carpathians with dextral and sinistral shear respectively 5 5 compression and accretion of the external thrust and fold belt in the eastern carpathians these kinematic patterns are thought to be interrelated and all are manifestations of the late stage evolution of an overthickened orogenic wedge in order to arrive at a better understanding of the mechanism of extension which formed the pannonian basin deep crustal seismic profiles hydrocarbon exploration reflection lines and borehole data have been analyzed in the little hungarian plain this plain represents the transition zone between the alps and the pannonian lowlands and the results are illustrated by eight interpreted cross sections one result of regional importance is the clear recognition that the transdanubian central range at the southeastern flank of the little hungarian plain is composed of alpine pre senonian thrust sheets this finding marks the end of a century of debate the allochthony of the substrata of the pannonian basin can be now considered proven another result of more general interest is that these cross sections document the mode of lithospheric extension preexisting compressional detachment planes reactivate as low angle normal faults and lead to tectonic unroofing of deeply buried metamorphic terranes characterized by ductile flow along subhorizontal lineation

sedimentology and hydrocarbon habitat of the submarine fan deposits of the central carpathian paleogene basin ne slovakia abstract the central carpathian paleogene basin accommodates a subsiding area of the destructive plate margin the basin history comprises marginal faulting and alluvial fan accumulation e 2 transgressive onlap by shoreface sediments and carbonate platform deposits e 2 glacio eustatic regression induced by cooling terminal eocene event forced regression tectonic subsidence and growth fault accumulation of basin floor and slope fans e 3 decelerating subsidence aggradation and sea level rising during the mud rich deposition o 1 high magnitude drop in sea level mid oligocene event retroarc backstep of depocenters and lowstand accumulation of sand rich fans and suprafans o 2 m 1 subduction related shortening and basin inversion along the northern margins affected by backthrusting and transpressional deformation o 2 m 1 the basin fill sequence has poor toc 0 5 to fair toc

3 d finite element modelling of deformation and stress associated with faulting effect of inhomogeneous crustal structures summary modelling of deformation and stress caused by earthquake faulting or fault motion based on a homogeneous elastic half space model does not include crustal rigidity layering and lateral variations geological data and seismic surveys indicate that the crust is elastically inhomogeneous and that rigidity layering and heterogeneities are likely to affect the magnitude and pattern of deformation and stress we use the finite element method fem to investigate deformation and stress generated by strike slip tensile and thrust faulting considering rigidity layering in the crust for a fault with a dimension of 25 10 km and a slip value of 0 5 m cutting through the top 10 km of the crust the deformation and stress change associated with the three modes of faulting are calculated for an island arc crustal structure represented by three models of rigidity layering the results indicate i the maximum effect in horizontal displacements due to crustal layering for the investigated models is 19 7 mm and 28 8 mm for strike slip and tensile faulting respectively for thrust faulting the effect is up to 58 3 mm this remarkable effect is due to the offset of layers by thrust faulting which dynamically changes the crustal structure both horizontally and vertically ii the maximum effect in vertical deformation due to crustal rigidity layering for strike slip and tensile faulting is 5 mm in contrast the effect for thrusting is 30 3 mm iii the effect in the shear stress change at a depth of 7 5 km for the different styles of faulting ranges from 0 02 mpa to 0 10 mpa an additional modelling analysis of subduction thrusting at the japan trench with a detailed structural model based on seismic surveys further confirms the significant distortion caused by a homogeneous model that ignores crustal structural information overall the effect of crustal rigidity layering is at least 20 per cent for surface deformation and 15 per cent for stress changes at depth in light of the present accuracy of global positioning system gps observations 2 mm and the estimate of stress change required for earthquake hazard analysis ca 0 01 mpa the results from the numerical experiments indicate that crust inhomogeneity rigidity layering and lateral variations should be included in any quantitative models of faulting

review of neogene and quaternary volcanism of the carpathian pannonian region abstract development of the pannonian basins as well as thrusting and folding of the carpathians was accompanied by widespread volcanic activity this volcanism can be divided into three main genetic types 1 1 early miocene mainly acidic volcanism tuffs and ignimbrites the recent spatial separation of these volcanics may be due to large right lateral displacement along the mid hungarian shear zone during the early miocene 2 2 middle miocene pliocene calc alkaline mainly intermediate stratovolcanic complexes in the inner western carpathians and in the east carpathians related to a subducted oceanic slab their geochemical compositions show a transitional character between active continental margin and island arc type magmatic rocks the thickness of the crust increased with time and from west to east beneath this volcanic arc 3 3 pliocene pleistocene alkali basaltic volcanism was related to an upwelling then cooling asthenospheric dome this is thought to have initiated the thermal regime from which these melts ascended the compositional difference in space and in time might reflect the existence of local individual small sized diapiric bodies as well as several processes e g fractional crystallization mixing which modified the original magma the eruption of these basaltic melts was temporally associated with the final phase of development of the pannonian basin this volcanism was associated with recent uplifts and tectonic rejuvenation of the area

seismic reflection coefficients from mantle fault zones summary several bright reflections from structures within the mantle can be seen on birps deep seismic reflection profiles we have calculated apparent reflection coefficients for the brightest of these events and obtain values around 0 1 it is not possible to produce such large reflections by either compositional layering or seismic anisotropy if olivine and pyroxene are the only significant minerals in the mantle these large reflections can be produced by a mafic layer or a partially hydrated layer within normal peridotite the brightest reflections seem to be best explained as major faults or shear zones within the mantle

the western carpathians interaction of hercynian and alpine processes abstract the complicated structural and rheologic properties of western carpathian lithosphere reflect the complex geodynamic history of the carpathian orogen based on critical analysis of earlier models new interpolation of existing geophysical data and results of integrated modelling a new map of the lithosphere thickness for the carpathian pannonian region has been constructed the map allows for the distinction of a frontal orogen collision zone in the ne from increased lithosphere thickness as well as a zone of oblique collision with the bohemian massif in the west where lithosphere is not significantly thickened the moho discontinuity beneath the western carpathian hinterland danube and east slovak basins as defined by deep reflection seismic profiling is relatively shallow this probably reflects recent crustal extension related to oblique collision between the european plate and the alcapa block and an increase of the asthenospheric updoming from the middle miocene onward crustal thickness reflects the combined effects of deep seated orogenic processes and mantle thermal evolution beneath the pannonian basin system in this study we focus particularly the structures of 1 the late alpine collision and neogene back arc basin development including deep seated contacts between colliding plates a zone of slab detachment the compressional accretionary wedge of the outer western carpathian flysch belt and extensional structures produced by subduction rollback and asthenosphere upwelling 2 early alpine structures related to cretaceous thrust stacking including subhorizontal reflection packages interpreted as multi generational extensional structures the underplated intra penninic oravic continental ribbon and ophiolite traces of the meliatic oceanic suture and 3 north dipping reflectors interpreted as remnant hercynian lithotectonic fragments with opposed vergency to the subducted alpine units

lithospheric structure of the trans european suture zone along the ttz cel03 seismic transect from nw to se poland abstract the large scale celebration 2000 seismic experiment investigated the velocity structure of the crust and upper mantle between western portion of the east european craton eec and the eastern alps this area comprises the trans european suture zone the carpathian mountains the pannonian basin and the bohemian massif this experiment included 147 chemical shots recorded by 1230 seismic stations during two deployments good quality data along 16 main and a few additional profiles were recorded one of them profile cel03 was located in southeastern poland and was laid out as a prolongation of the ttz profile performed in 1993 this paper focuses on the joint interpretation of seismic data along the nw se trending ttz cel03 transect located in the central portion of the trans european suture zone first arrivals and later phases of waves reflected refracted in the crust and upper mantle were interpreted using two dimensional tomographic inversion and ray tracing techniques this modelling established a 2 d quasi 3 d p wave velocity lithospheric model four crustal units were identified along the transect from northwest to southeast thickness of the crust varies from 35 km in the pomeranian unit nw to 40 km in the kuiavian unit to 50 km in the radom ysogory unit and again to 43 km in the narol unit se the first two units are thought to be proximal terranes detached from the eec farther to the southeast and re accreted to the edge of the eec during the early palaeozoic the origin of the remaining two units is a matter of dispute they are either portions of the eec or other proximal terranes in the area of the polish basin first two units the p wave velocity is very low vp

behavior of sm and nd in a lateritic soil profile a study of lateritic soils and samples of ground and river waters was carried out in the nsimi zoetele a tropical watershed in the southern cameroon the nd isotopic compositions and concentrations of nd and sm were determined it was found that the nd isotopic composition of the river waters was much more radiogenic than the parent rocks and that the nd in the waters is not homogeneous but is carried by different dissolved and complexed components that are not isotopically homogenized the soil profile shows a regular increase in e nd going from the parent rock e nd 36 to e nd 18 near the top of the profile the nd transported in the river is thus not representative of the parent rock but reflects the results of differential weathering of constituent minerals and the redeposition of ree in phosphates and a significant contribution of radiogenic nd from dust the concentration of nd in the river water is far above that found in temperate climate rivers and thus this type of tropical river may play a dominant role in the marine nd and ree budget it is suggested that the correlation of ree with doc is related to doc fixing some dissolved ree but that the ree in solution is governed by other mechanisms no major shifts were found in sm nd however a regular progression from the parent rock through the lateritic profile was found the upper laterite profile shows large almost uniform depletions in all ree below tb and enrichment above complementary behavior was found in the lower part of the section the concentration of nd relative to the immobile elements zr and ti in the laterite is depleted by a factor of 10 th nd and sm are enriched in the lowest zone sampled and must reflect redeposition of ree from the upper part of the weathering section and is associated with phosphate formation it is concluded that the soil evolution involves both differential dissolution of primary phases from the parent rock significant to major input of ree from atmospheric dust from other regions and the formation of diagenetic phases particularly phosphates

seismic evidence of caledonian deformed crust and uppermost mantle structures in the northern part of the trans european suture zone sw baltic sea abstract collisional structures from the closure of the tornquist ocean and subsequent amalgamation of avalonia and baltica during the caledonian orogeny in the northern part of the trans european suture zone tesz in the sw baltic sea are investigated a grid of marine reflection seismic lines was gathered in 1996 during the dekorp basin 96 campaign shooting with an airgun array of 52 l total volume and recording with a digital streamer of up to 2 1 km length the detailed reflection seismic analysis is mainly based on post stack migrated sections of this survey but one profile has also been processed by a pre stack depth migration algorithm the data provides well constrained images of upper crustal reflectivity and lower crustal uppermost mantle reflections in the area of the caledonian suture a reflection pattern is observed with opposing dips in the upper crust and the uppermost mantle detailed analysis of dipping reflections in the upper crust provides evidence for two different sets of reflections which are separated by the o horizon the main decollement of the caledonian deformation complex s dipping reflections beneath the sub permian discontinuity and above the o horizon are interpreted as caledonian thrust structures beneath the o horizon sw dipping reflections in the upper crust are interpreted as ductile shear zones and crustal deformation features that evolved during the sveconorwegian orogeny the caledonian deformation complex is subdivided into 1 s dipping foreland thrusts in the north 2 the s dipping suture itself that shows increased reflectivity and 3 apparently ne dipping downfaulted sedimentary horizons south of the avalonia baltica suture which may have been reactivated during mesozoic normal faulting the reflection moho at 28 35 km depth appears to truncate a n dipping mantle structure which may represent remnant structures from tornquist ocean closure or late collisional compressional shear planes in the upper mantle a contour map of these mantle reflections indicates a consistent northward dip which is steepest where there is strong bending of the caledonian deformation front the thin skinned character of the caledonian deformation complex and the fact that n dipping mantle reflections do not truncate the moho indicate that the baltica crust was not mechanically involved in the caledonian collision and therefore escaped deformation in this area

deep crustal structure beneath the central and inner west carpathians abstract the 150 km long deep seismic transect 2t crossing the central part of the slovakian west carpathians has revealed an important whole crustal seismic suture zone dipping to the south this zone is dominated by six large and several minor reflection events because of our good knowledge of the surface geology and a large number of comparative studies of the eastern alps it is clear that the upper reflections are due to overthrust sheets that originated during compression of the apulian passive margin tectonically deeper reflections are interpreted as being due to ligurian oceanic igneous and sedimentary rocks sheared in ductile domain during continental collision with the brianconnais passive margin and continental masses north of the central apulian west carpathians cwc behind a significant strike slip fault are the cenozoic structures of the pieniny klippen belt and the magura rhenodanubian flysch south of the cwc the inner tethyan west carpathians iwc are thrust over the cwc the iwc originated during the late jurassic early cretaceous closure of the tethyan ocean and the seismic image of the iwc is different from the highly reflective cwc suture these three pre neogene nappe systems amalgamated as one overthrust system during the neogene subduction of the moldavian sea as the moldavian accretionary wedge the vepor gemer block of the west carpathians where the cretaceous suture is observed has been untouched by any major cenozoic deformation and has remained relatively rigid this unique structure therefore enables us to observe seismically the cretaceous suture zone which elsewhere in the european alpine belt has been almost completely destroyed more general data about the beginning of subduction and subsequent collision processes are presented significant compression and partial subduction of the apulian upper plate passive margin lasted from the hauterivian to the beginning of the turonian for about 25 30 ma subduction of the ligurian ocean occurred from turonian to campanian times after the early campanian the collision of the apulian and brianconnais plates took place

paleogene retroarc flexural basin beneath the neogene pannonian basin a geodynamic model abstract the neogene middle miocene recent pannonian basin is superimposed on an earlier paleogene middle eocene early miocene basin complex as a result of back arc extension although the stratigraphy of the latter is very well known due to raw material exploration its formation and structural evolution is much less understood a transtensional origin was generally proposed for the paleogene basin of hungary assuming an origin analogous to that of the overlying neogene pannonian basin we suggest an alternative geodynamic scenario for the development of the paleogene basin complex as we think that the observations are better understood in terms of a retroarc foredeep basin model according to this a flexural basin developed south of the backthrust inner west carpathian units the thrust load resulted in a generally deep underfilled flysch basin during middle eocene early oligocene times in the late oligocene early miocene predominantly shallow marine and continental deposition occurred indicating the gradual cessation of thrusting in the adjacent thrust fold belt and the beginning of molasse sedimentation throughout the whole paleogene a shift can be observed of the bathyal dominantly siliciclastic in the axis of the foredeep and neritic partly carbonate in the foreland flank of the foredeep facies belts this migration of the middle eocene early miocene depocenters of the hpb hungarian paleogene basin to the east northeast in present day coordinates is the result of two processes 1 1 the advancement of backthrusting to the southeast 2 2 along strike shift of thrusting to the northeast while a thin skinned thrust front can be reconstructed for the late eocene buda anticline the diosjeno hurbanovo line is interpreted as the result of a major thick skinned thrusting event at the base of the np24 zone 31 ma the subsidence pattern the distinct depositional environments and the structural observations can be more easily integrated into a flexural basin model than into a wrench basin model based on the flexural basin model of this work the early tertiary western carpathians formed a compressional arc while this arc probably developed above a b subduction zone during the late eocene with a corresponding trench magura a forearc basin central carpathian or podhale and a retroarc flexural basin hungarian paleogene from the early oligocene to the early miocene it was characterized by a subduction with a corresponding peripheral foredeep dukla and silesian and a retroarc flexural basin hungarian paleogene

upper mantle reflectors modelling of seismic wavefield characteristics and tectonic implications summary deep seismic experiments on continental lithosphere generally reveal marked reflectivity from structures in the crust and a significant decrease in reflectivity from the upper mantle however reflected and refracted energy from mantle lithosphere are observed in both near normal incidence and wide angle data the origin of the reflective structures is a matter of debate hypotheses include remnant subduction zones shear zones fluids and seismic anisotropy through analytical and numerical modelling studies including full wavefield modelling we investigate seismic characteristic signatures generated from a variety of geologically plausible models we have found that both upper mantle shear zones of reduced velocity and density and remnant subduction slabs containing high density eclogites may contain sufficient seismic impedance contrasts to normal mantle peridotites to generate near normal incidence reflectivity wide angle energy originates from subduction slabs containing either high or lowvelocity eclogites whereas intermediate velocity eclogites are unlikely to produce significant wide angle phases in general energy of seismic phases originating from upper mantle zones of anomalous seismic velocities and densities is significantly increased if homogeneous zones are replaced by zones of inhomogeneous petrophysical properties resulting from constructive interference maximum wavefield anomalies are generated from sub moho dipping slabs of incomplete transformation of low velocity low density crustal material to high velocity highdensity eclogites localized shear zones generated in mantle peridotite generally do not produce significant wide angle energy only if highly inhomogeneous structures containing material of marked ca 10 per cent velocity and density reduction are present may shear zones be observed in wide angle data analyses of two specific deep seismic data sets mona lisa data from the north sea and babel data from the baltic sea show good agreement between observations and modelling results for dipping remnant subduction slabs containing small scale inhomogeneities associated with incomplete transformation our modelling results improve our possibilities of distinguishing between two often contrasting tectonic interpretations for dipping upper mantle seismic reflectors the remnant subduction and shear zone models

the border of the east european craton in south eastern poland based on gravity and magnetic data according to recent geological interpretations the border of the east european craton eec in se poland is located in the ne foreland of the holy cross mts results of gravity and magnetic anomaly interpretations presented herein confirm this according to 3d and 2d gravity and magnetic modelling the eec borders the sw flank of the regional crystalline feature with increased magnetic and density properties which occur in the se part of the teisseyre tornquist zone ttz this flank rests near a deep fracture delimiting the ttz on sw the feature is a cause of the regional magnetic gradient observed there two se nw belts of residual gravity anomalies dislocations are also identified in the magnetic gradient zone cutting mesozoic and palaeozoic formations results of geophysical and geological investigations show the importance of this dislocation zone and confirm that it occurs in all crustal complexes and the upper mantle

lithospheric structure beneath trans carpathian transect from precambrian platform to pannonian basin celebration 2000 seismic profile cel05 1 in 2000 a consortium of european and north american institutions completed a huge active source seismic experiment focused on central europe the central european lithospheric experiment based on refraction or celebration 2000 this experiment primarily consisted of a network of seismic refraction profiles that extended from the east european craton along and across the trans european suture zone region in poland to the bohemian massif and through the carpathians and eastern alps to the pannonian basin the longest profile cel05 1420 km is the focus of this paper the resulting two dimensional tomographic and ray tracing models show strong variations in crustal and lower lithospheric structure clear crustal thickening from the pannonian basin 24 25 km thick to the trans european suture zone region 50 km together with the configuration of the lower lithospheric reflectors suggests northward subduction of mantle underlying carpathian pannonian plate under the european plate this however conflicts with strong geological evidence for southward subduction and we present three tectonic models that are to not totally mutually exclusive to explain the lithospheric structure of the area 1 northward old subduction of the pannonian lithosphere under the east european craton in the jurassic lower cretaceous 2 a collisional zone containing a crocodile structure where carpatho pannonian upper crust is obducting over the crystalline crust of the east european craton and the carpathian pannonian mantle lithosphere is underthrusting cratonic lower crust and 3 lithosphere thinning due to the effects of neogene extension and heating with the slab associated with young subduction southward in the miocene having been either detached and or rolled back to the east in the last case the northwestward dipping in the lithosphere can be interpreted as being due to isotherms that could represent the lithosphere asthenosphere boundary in the pannonian region

the moho depth map of the european plate summary the european plate has a 4 5 gy long and complex tectonic history this is reflected in the present day large scale crustal structures a new digital moho depth map is compiled from more than 250 data sets of individual seismic profiles 3 d models obtained by body and surface waves receiver function results and maps of seismic and or gravity data compilations we have compiled the first digital high resolution map of the moho depth for the whole european plate extending from the mid atlantic ridge in the west to the ural mountains in the east and from the mediterranean sea in the south to the barents sea and spitsbergen in the arctic in the north in general three large domains within the european plate crust are visible the oldest archean and proterozoic crust has a thickness of 40 60 km the continental variscan and alpine crust has a thickness of 20 40 km and the youngest oceanic atlantic crust has a thickness of 10 20 km

lower crustal rejuvenation and growth during post thickening collapse insights from a crustal cross section through a variscan metamorphic core complex the variscan lower crust of europe acquired its main features seismic layering intrusion of mantle derived magmas granulite grade metamorphism when the upper crust underwent post thickening extension through gravitational collapse we suggest that post thickening collapse is a geodynamic process that contributes to the growth and differentiation of continental lithosphere in collapsed mountain belts

partial detachment of a lithospheric root under the southeast carpathians toward a better definition of the detachment concept the southeast corner of the carpathian mountains romania provides a unique opportunity to study the very final and shortlived stage of plate convergence when a piece of subducted lithosphere finally detaches from the overriding plate and begins to sink into the mantle research efforts commonly focus on trying to image the cold lithospheric slab tomographic techniques and on trying to understand the tearing process from the earthquakes it generates here this issue is tackled from a different perspective emphasizing that the southeast carpathians are extremely low considering crustal thickness the crust there is almost as thick as the crust of the alps 50 55 km but the elevation is less than onehalf of the elevation of the alps it is interesting that the apennines italy are just the opposite they are rebounding after slab breakoff to reach elevations higher than expected from their crustal thickness 30 35 km like the crust of most passive margin coasts it is thus proposed that although seismologic studies indicate that the cold mantle body under the southeast carpathians is already partly detached from the overriding lithosphere it is still viscously coupled to the lithosphere and pulls it downward by utilizing residual topography analysis observed topography minus the contribution of the crust to it the subcrustal load is quantified and interpreted in terms of mantle lithosphere thickness extending to a depth of 300 km a particularly interesting finding is that the seismically active region is shifted 50 km east of the place of maximum pull down indicating that lithospheric tearing is now occurring at one side of the detaching root and not above it this interpretation is consistent with the idea of lateral delamination of the lower lithosphere

gravity constraints on the crustal structure and slab evolution along a transcarpathian transect abstract a new unified bouguer anomaly map of the carpathian arc and the pannonian basin has been compiled from previously prepared and recently published gravity maps in order to constrain the crustal structure and the tectonic evolution of the area a two dimensional gravity model is presented along a western carpathians pannonian basin southern carpathians transect the model is based on deep seismic lines where available and on detailed geological sections the results confirm that the extensional crustal structure of the pannonian basin revealed by deep seismic surveys agrees with the gravity data furthermore they suggest that the western and southern carpathians area at different stages of their evolution the subducted oceanic slab under the western carpathians has already been assimilated to the asthenosphere while a crustal slab is still present under the southern carpathians these findings are compatible with the observation that the last major phase of crustal shortening terminated at the early middle miocene in the western carpathians but continued throughout the pliocene in the southern carpathians

lithospheric growth at margins of cratons abstract deep seismic reflection profiles collected across proterozoic archean margins are now sufficiently numerous to formulate a consistent hypothesis of how continental nuclei grow laterally to form cratonic shields this picture is made possible both because the length of these regional profiles spans all the tectonic elements of an orogen on a particular cratonic margin and because of their great depth range key transects studied include the lithoprobe snorcle 1 transect and the babel survey crossing the slave and baltic craton margins respectively in most cases the older archean block appears to form a wedge of uppermost mantle rock embedded into the more juvenile proterozoic block by as much as 100 200 km at uppermost mantle depths and archean lithosphere is therefore more laterally extensive at depth than at the surface particularly bright reflections along the moho are cited as evidence of shear strain within a weak low viscosity lower crustal channel that lies along the irregular top of the indenting wedge the bottom of the wedge is an underthrust subduction zone and associated late reversal in subduction polarity beneath the craton margin emerges as a common characteristic of these margins although related arc magmatism may be minor

seismic and geological structure of the crust in the transition from baltica to palaeozoic europe in se poland celebration 2000 experiment profile cel02 abstract the celebration 2000 together with the earlier polonaise 97 deep seismic sounding experiments was aimed at the recognition of crustal structure in the border zone between the precambrian east european craton baltica and palaeozoic europe the cel02 profile of the celebration family is a 400 km long sw ne transect running in poland from the upper silesia block usb across the malopolska block mb and the trans european suture zone tesz to the east european craton eec the structure along cel02 was interpreted using both 2d tomography and forward ray tracing techniques as well as 2d gravity modelling the crustal thickness along cel02 varies from 32 35 km in the usb to 45 47 km beneath the tesz and the eec the usb is a clearly distinctive crustal block with the characteristic high velocity lower crust 7 1 7 2 km s interpreted as a fragment of gondwana the krakow lubliniec fault is a terrane boundary produced by soft docking of the usb with the mb the malopolska crust fundamentally differs from the usb and has a strong connection with baltica it is a transitional 150 to 200 km wide unit composed of the extended baltican lower crust and the overlying low velocity 5 15 5 9 km s neoproterozoic metasediments in the up to 18 km thick upper crust the ysogory unit has its crustal structure identical with that of malopolska thus it is connected with baltica and cannot be interpreted as a gondwana derived terrane higher velocity and density bodies found below the mazovia lublin graben at a depth of 12 km and at the base of the lower crust might be a result of mantle derived mafic intrusions accompanying the extension of baltica by the preliminary 2d gravity modelling we have reconfirmed the need for considering the increased tesz mantle density in comparison to the eec and usb mantle

crustal and upper mantle structure of the western carpathians from celebration 2000 profiles cel01 and cel04 seismic models and geological implications summary celebration 2000 was a large international experiment that focused on the lithospheric structure in central europe it consisted of several wide angle reflection and refraction seismic profiles profiles cel01 and cel04 are located in the transition from the precambrian and palaeozoic platforms to the carpathian orogen the data were modelled using 2 d tomographic and forward modelling techniques the profile cel01 about 900 km long extends from the southwestern margin of the east european craton to the pannonian basin system the depth of moho boundary varies along the profile from 27 33 km under the pannonian basin system area 30 39 under the carpathians and within the tesz to 40 45 km under the east european craton the cel04 profile 630 km long starts in the polish trough pt and reaches the pannonian basin system along the cel04 profile the moho interface shallows from 40 km beneath the pt to about 35 km in the maopolska unit the crustal thickness is 43 km beneath the carpathians and 25 km beneath the pannonian basin system the results obtained are consistent with a commonly accepted view of the carpathians thought to be formed largely due to the interplay between palaeogene to middle miocene subduction of oceanic or suboceanic crust and subsequent collision a feature that we interpret as the subduction related orogenic root is at least partially preserved in both profiles and is manifested by a crustal thicknesses of 39

evolution of the pannonian basin system 2 subsidence and thermal history analysis of sedimentation and thermal data indicates that for most parts of the pannonian basin observed heat flow thermal gradients rates of thermal subsidence and vitrinite reflectance are about twice those predicted by assuming a uniform extension model for basin formation in late miocene time a modified extension model whereby large amounts of heat are added to the uppermost mantle during extension roughly equivalent to replacing the entire sub crustal lithosphere by asthenosphere produced results in good agreement with observation and could also account for periods of uplift observed during extension crustal extension beneath most parts of the basin is estimated to have been about 80 to 170 1 8 to 2 7 although in the deepest parts of the basin deeper than 4 km crustal extension could have been much greater analysis of extension within the danube and zala basins indicates that the late miocene extension in these basins involved the entire lithosphere but subsidence and heat flow data are not well enough constrained to determine if extra heating is required during extension on the basis of tectonic and structural data the vienna basin has been interpreted as the result of thin skinned extensional tectonics above a shallow detachment surface within the upper crust royden et al this issue analysis of thermal and subsidence data from the northern vienna basin suggests that little or no heating occurred during basin extension these data are consistent with a thin skinned extensional origin for the vienna basin and are in better agreement with this interpretation than with the assumption of a uniformly extended lithosphere beneath the basin this study emphasizes the need for good thermal subsidence and structural data in making reconstructions of extensional and thermal histories of sedimentary basins when such data are available it is found that a simple uniform extension model does not explain very well the evolution of some sedimentary basins such as the vienna and pannonian basins in the first instance the basin is thought to be the result of upper crustal extension only due to its special tectonic setting in the second instance the extra heating during extension is due to some unknown processes in the lower lithosphere that may be a general feature of lithospheric extension thus lithospheric extension and associated heating may be distributed in a variety of ways not all extensional sedimentary basins form in the same way application of a uniform subsidence model to basins for which good thermal subsidence and structural data are not available or not properly analysed can lead to reconstructions of thermal histories in error by a factor of 2 or more

modeling wide angle seismic data for crustal structure southeastern grenville province a modeling methodology for obtaining two dimensional 2 d crustal structure from wide angle seismic data is applied to data from the southeastern grenville province pre modeling steps include 1 assignment of arrival pick uncertainties for appropriate data fitting and weighting using an empirical relationship based on signal to noise ratio 2 using a modified form of travel time reciprocity to avoid unreasonable levels of model heterogeneity and 3 identifying data unsuitable for 2 d modeling the goal of the travel time inversion amplitude modeling approach is to obtain a minimum structure and minimum parameter model that takes into account both horizontal and vertical variations in the resolution of typical wide angle data each step of a layer stripping procedure involves a series of inversions in which a one dimensional or simple starting model is improved with additional velocity and or interface nodes until a satisfactory trade off between travel time fit parameter resolution and complete ray coverage of all source receiver pairs is achieved using zero vertical velocity gradient layers and head waves during preliminary first arrival inversion can 1 decrease the number of intermediate models 2 allow greater lateral heterogeneity to be imaged and 3 simplify incorporation of amplitude modeling constraints into the final model using amplitude distance curves allows quantitative modeling of the relative amplitude and offset variations of phases discrepancies between observed and calculated reflection amplitudes are used to infer fundamental non step like velocity changes at layer boundaries later arrivals due to unresolved velocity anomalies are modeled using reflecting segments that float within the model without an associated velocity structure these reflectors provide a spatial image like that obtained from vertical incidence reflection data as opposed to a velocity image the model of grenville crustal structure is more detailed than a model obtained from a previous interpretation of the data and includes elements analogous to those imaged in nearby deep reflection data a crustal scale zone of wide angle reflectors with an average easterly apparent dip of 13 defines a major grenvillian terrane boundary

subducted continental margin imaged i n the carpathians of czechoslovakia deep seismic reflection data across the frontal part of the carpathian arc image subducted european continental crust beneath the thick accretionary wedge of the neogene west carpathian arc the upper continental crust of the lower plate is depressed with high curvature to a depth off about 25 km below the arc but the corresponding moho appears to be nearly horizontal flow within the lower crust may account for strain mismatch between the two parts of the subductiog continent although the subdued relief on the moho may partly have evolved after subduction ceased perhaps owing to a gabbro eclogite phase change in a mafic lower crust

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

deep structure of the earth s crust in the contact zone of the palaeozoic and precambrian platforms in poland tornquist teisseyre zone abstract one of the major tectonic problems in europe concerns the southwest margin of the east european platform in the region of the so called polish danish trough in general this margin is assumed to be the tornquist teisseyre t t line running approximately from northwest to southeast in this part of europe determination of deep crustal structure of the contact zone between the precambrian platform and the palaeozoic platform was the main aim of the deep seismic sounding dss programme in poland in 1965 1982 deep seismic soundings of the earth s crust have been made in the t t line zone along nine profiles with a total length of about 2600 km the results of deep seismic soundings have shown that the crust in the marginal zone of the east european platform has highly anomalous properties the width of this zone ranges from 50 km in northwest poland to about 90 km in southeast poland the crustal thickness of the palaeozoic platform in poland is 30 35 km and of the precambrian platform 42 47 km while in the t t tectonic zone it varies from 50 to 55 km above the moho boundary in the t t zone at a depth of 40 45 km there is a seismic discontinuity with p wave velocities of 7 5 7 7 km s boundary velocities mean velocities and stratification of the earth s crust vary distinctly along the t t zone there are also observed high gravimetric and magnetic anomalies in the t t zone the t t tectonic zone determined in this manner is a deep tectonic trough with rift properties the deep fractures delineating the t t tectonic zone are of fundamental importance for the localization of the plate edge of the precambrian platform of eastern europe in the light of dss results the northeastern margin of the t t tectonic zone is a former plate boundary of the east european platform

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