is the teisseyre tornquist zone an ancient plate boundary of baltica the teisseyre tornquist zone ttz is generally regarded as a fossil plate boundary in europe that extends 2000 km from the baltic sea to the black sea we used an integrated approach merging potential fields and seismic data to explore crustal architecture across the ttz in central poland the aim of the study was to test whether the ttz coincides with an early paleozoic caledonian suture formed through the closure of the tornquist ocean along the sw baltica margin the suture is presumed to separate the east european craton eec from the paleozoic terranes of western europe two seismic reflection lines from the polandspan experiment were used to image the deep structure at the sw margin of the eec lines pl 5300 and pl 5400 run ne sw in central and northern poland respectively the seismic interpretation down to top of basement was integrated with 2 d gravity and magnetic modeling to highlight the structure of the deep crust both the gravity and magnetic models show a suture that welds together two blocks at the base of crust however top of basement above the suture dips uniformly to the sw and is overlain by undisturbed lower paleozoic and younger sediments by implication the suture must have developed in the precambrian and both crustal blocks amalgamated belong to the eec consequently the caledonian suture formed by the closure of the tornquist ocean between avalonia and baltica must be located farther southwest beneath thick upper paleozoic and mesozoic sediments

refined timing and kinematics for baltica avalonia convergence based on the sedimentary record of a foreland basin the caledonian foreland basin of poland onlaps the sw slope of the east european craton and is elongated in a nw sw direction along the margin of the baltica palaeocontinent the base of the synorogenic clastic wedge rises in age from llandovery to ludlow between nw and se poland respectively as the initial influx of orogen derived detritus can be unequivocally identified this diachronism documents a southeastward migration of the basin depocentre parallel to the present day caledonian deformation front our best fit plate model shows an oblique collision of baltica and avalonia the latter initially indenting the baltica margin in the nw afterwards baltica was progressively underthrust beneath avalonia towards the se in response to the oblique soft mode closure of the tornquist ocean the final deformation event within the caledonian foreland took place in the earliest devonian as a far field effect of sinistral orogen parallel displacements along the iapetus suture this article is protected by copyright all rights reserved

assessment of the topex altimeter performance using waveform retracking to assess the accuracy of the topex altimeter data we have reprocessed the raw altimeter waveform data using more sophisticated algorithms than those implemented in the altimeter hardware we discuss systematic contamination of the waveform which we have observed and its effect on very long wavelength errors we conclude that these systematic errors are responsible for a very long wavelength error whose peak to peak magnitude for the ku band altimeter is of the order of 1 cm we also examine the ability of retracked data to reduce the repeat pass variance and correct for significant wave height swh and acceleration dependent errors we find that the ground postprocessing contains swh dependent biases which depend on the altimeter fine height correction

a geosat altimeter wind speed algorithm and a method for altimeter wind speed algorithm development a geosat altimeter wind speed algorithm is derived by cross calibrating geosat and seasat altimeter estimates of the normalized radar cross section 0 and modifying an existing seasat altimeter wind speed model function to obtain a model function appropriate for geosat observations it is argued that the 0 distribution measured by an altimeter is relatively stable over a sufficiently large geographical region and a long enough time period systematic differences between 0 estimates from two altimeters can therefore be identified based on comparisons of their 0 histograms any such systematic differences can then be corrected using independent 0 estimates when this method is applied to the geosat and seasat altimeters a systematic difference between the two 0 histograms is shown to be consistent with differences between seasat altimeter and nadir seasat scatterometer estimates of 0 deduced independently by a previous study this supports the conclusions that 1 the 0 distribution is stable and 2 the seasat altimeter estimates of 0 were miscalibrated after modifying the existing seasat altimeter wind speed algorithm to account for this apparent 0 error the resulting geosat estimates of wind speed agree with high quality buoy observations to within an rms difference of less than 2 m s

use of the topex poseidon dual frequency radar altimeter over land surfaces the capability of nasa radar altimeter topex for land surface studies at regional or global scale is investigated the analyzed data available since mid 1992 consist of dual frequency backscattering coefficients values ku and c band estimated at the nadir pointing angle along the satellite tracks between 66js and 66jn and averaged in 0 75j ground resolution cell mean global backscatter images of the entire land surfaces are presented in ku c band and the difference c ku statistics and major temporal signals over nine entire years are also presented at a global scale finally temporal profiles of backscatters are extracted for main land types desert tropical forest wet and dry savanna boreal regions ice sheet to validate the dataset and to analyze radar response to land surface variability through 9 years results indicate the high capabilities of topex poseidon t p radar altimeter data for monitoring snow covered regions at global and regional scale the use of dual frequency measurements can also improve methods developed with single frequency radar altimeter over complex vegetated areas the complementarities for future synergy with wind scatterometer or satellite imagery data over continents look also promising because of the t p 10 day repeat cycle a 10 year span dataset and a future better spatial resolution with combination of other dual frequency altimetry missions such as envisat or jason

seismic basement in poland the area of contact between precambrian and phanerozoic europe in poland has complicated structure of sedimentary cover and basement the thinnest sedimentary cover in the mazury belarus anteclize is only 0 3 1 km thick increases to 7 8 km along the east european craton margin and 9 12 km in the trans european suture zone tesz the variscan domain is characterized by a 1 to 2 km thick sedimentary cover while the carpathians are characterized by very thick sediments up to c 20 km the map of the basement depth is created by combining data from geological boreholes with a set of regional seismic refraction profiles these maps do not provide data about the basement depth in the central part of the tesz and in the carpathians therefore the data set is supplemented by 32 models from deep seismic sounding profiles and a map of a high resistivity low conductivity layer from magnetotelluric soundings identified as a basement all of these data provide knowledge about the basement depth and of p wave seismic velocities of the crystalline and consolidated type of basement for the whole area of poland finally the differentiation of the basement depth and velocity is discussed with respect to geophysical fields and the tectonic division of the area

timing of the avalonia baltica plate convergence as inferred from palaeogeographic and stratigraphic data of chitinozoan assemblages in west pomerania northern poland timing of the avalonia baltica plate convergence as inferred from palaeogeographic and stratigraphic data of chitinozoan assemblages in west pomerania northern poland

the pliocene pleistocene stratigraphic and tectonic evolution of the central sector of the western periadriatic basin of italy abstract the central portion of the western periadriatic basin is a foreland basins systems associated to the central apennine outer orogenic wedge that stretches along the marche and abruzzi regions of italy an area that has been studied since long time and where a plenty of surface and subsurface data are available the present study is aimed to review and synthetize these data add new surface and subsurface data in order to define a firm stratigraphic and tectonic framework that is base for the reconstruction of the pliocene pleistocene tectonic stratigraphic evolution of the central portion of the western periadriatic basin the study integrates field mapping published geological maps seismic lines well logs and an updated chronostratigraphic scheme six major nne ssw thrust stacks and eight unconformity bounded stratigraphic units have been defined then a ne sw oriented zone separates a northern from a southern sector which have differences in structural styles amount of shortening basins widths and thicknesses of stratigraphic units despite these differences the deformation timing the depositional history and the migration of basins system are common in both sectors and eight tectonic stratigraphic evolutionary stages have been reconstructed with sequential restoration of two representative cross sections the results highlight that the pliocene pleistocene stratigraphic and tectonic evolution of the central western periadriatic basin preserves the records of supra regional and global controls which drive thrust propagation orogen growth basins migration and basins sedimentary infill in particular the stratigraphy preserves global third order eustatic climatic changes that have a strict feed back and concomitance with tectonic pulses the latter are regulated 1 by cyclic growth of an orogenic wedge undergoing coeval erosion and sedimentation and 2 by eastward retreat of a westward subducting and flexing continental lithosphere

shrimp u pb zircon dating for granitoids from the strzegom sobotka massif sw poland constraints on the initial time of permo mesozoic lithosphere thinning beneath central europe abstract new shrimp ii data from the strzegom sobotka composite granitoid intrusion show a successive emplacement of four magma batches with different modal compositions over the period of c 10 15 m y the first emplaced was the two mica granite that crystallised at 304 8 2 7 ma this was followed by the biotite granodiorite the three samples of which were dated at 301 9 3 6 299 3 2 4 and 297 9 3 7 ma respectively the biotite and hornblende biotite granites yielded practically an identical age 301 1 2 7 ma 297 7 2 2 ma and 297 1 3 0 ma but are considered slightly younger based on the field cross cutting relationships the final rock type is the azany granodiorite dated at 294 4 2 7 ma the temperature estimates along with the zircon crystal morphology show the gradual but significant rise of magma temperature with the decreasing age of intrusion the temperature increased from c 720 c in the two mica granite to 740 780 c in the biotite granodiorite and 800 860 c in the biotite hornblende granites and azany granodiorite based on the ages obtained the emplacement of the strzegom sobotka granitoids immediately followed the cessation of compression in the variscan externides of sw poland moreover the intrusion was synchronous with rapid uplift of the variscides and abundant bimodal volcanism in the nearby intramontane troughs consequently the gradual heating of the crust as recorded by the data acquired must have been caused by thermal influx into the lower crust related to the ascent of basaltic magmas since the latter were probably formed during the decompressional melting of lithospheric mantle the emplacement of strzegom sobotka granitoids along with bimodal volcanism signalled the commencement of lithospheric thinning beneath central europe

palaeogeographic significance of mid silurian palaeomagnetic results from southern britain major revision of the apparent polar wander path for eastern avalonia summary wenlock c 430 ma lavas from the east mendips inlier southern briain are characterized by either single component magnetizations type 1 or a more complex system of three magnetization components type 2 during stepwise thermal demagnetization the type of demagnetization behaviour is related to changes in magnetic petrology within the lava pile the lower and intermediate unblocking temperature components of type 2 represent magnetic overprints of tertiary recent and hercynian mid carboniferous origin respectively the primary nature of the high unblocking temperature magnetization component types 1 and 2 dec 095 c inc 24 ag5 8 8 is demonstrated by positive agglomerate tests conversely an overlying upper old red sandstone sequence did not provide primary magnetizations the magnetic signature is governed by syn tectonic hercynian remagnetizations the primary silurian data demonstrate that the east mendips inlier experienced considerable clockwise rotation probably of the order of 80 prior to partial remagnetization during hercynian deformation and folding the silurian palaeopole vgp 13 n 271 e dp dm 5 9 cannot therefore be used for apparent polar wander path construction nevertheless the palaeolatitude estimate 13 f 5s suggests that southern britain eastern avalonia was at comparable mid silurian latitudes to baltica and northern britain 10 20 s both the iapetus ocean and tornquist sea therefore which separated southern britain from laurentia and baltica respectively in ordovician times were closed by wenlock time as ordovician and silurian palaeomagnetic data from baltica and eastern avalonia now record a comparable northwards translation from high southerly to near equatorial latitudes during this time we postulate pre wenlock collision of these blocks to form balonia baltica eastern avalonia a new apparent polar wander path for eastern avalonia constructed on the basis of this palaeogeographic model is presented

first 40ar 39ar age constraints for the caledonian evolution of the trans european suture zone in ne germany from three rugen boreholes g14 rugen 5 loissin 1 across the caledonian deformation front four lower palaeozoic slate samples and three detrital muscovite concentrates from associated sandstones have been analysed by 40 ar 39 ar analysis microprobe analysis of the detrital muscovites show homogeneous but distinct chemical compositions for each concentrate particulate organic matter reflectance and illite crystallinity indicate that all the analysed whole rock samples have experienced anchizonal metamorphic conditions 40 ar 39 ar analysis of the samples from the g14 and loissin 1 wells give almost identical results muscovite concentrates define plateau ages of c 830 ma and show an isotopic rejuvenation of low temperature increments around 440 ma whole rock slate samples give plateau ages of c 440 ma and c 427 ma isotopic rejuvenation in the low temperature increments prior to 350 ma in the loissin 1 sample can be attributed to the permo carbonifereous volcanism which is known from this borehole in contrast samples from the borehole rugen 5 show a different isotope pattern a muscovite concentrate defines a plateau age of 609 ma two whole rock slate samples give internally discordant but identical 40 ar 39 ar spectra with consistent isotopic rejuvenation from high to low temperature increments from 510 ma to 420 ma while for the g14 and loissin 1 sandstone samples a baltica derived provenance can be assumed greywackes of rugen 5 indicate a cadomian influenced perigondwanan detrital source according to the results of whole rock slate samples the main caledonian tectonothermal event in ne germany occurred around the ordovician silurian boundary or in the early silurian 450 425 ma from these data the rugen palaeozoic appears as an allochthonous caledonian nappe complex which has been thrust much further onto the baltic shield than previously thought

analysis of geomagnetic field along seismic profile p4 of the international project polonaise 97 abstract this paper presents relative secular variations of the total intensity of the geomagnetic field against a background of results of magnetic anomaly interpretation along seismic profile p4 profile p4 crosses a variscan folding zone in the paleozoic platform plz the trans european suture zone tesz and the polish part of the east european craton eec secular geomagnetic field variations t measured in 1966 2000 along a line adjacent to seismic profile p4 were analysed the study of secular variations reduced to the base recordings at the belsk magnetic observatory showed that the growth of geomagnetic field at the east european craton was slower than in the trans european suture zone and the paleozoic platform a 2d crustal magnetic model was interpreted as a result of magnetic modelling in which seismic geological and geothermal data were also used the modelling showed that there were significant differences in the magnetic model for geotectonic units which had been earlier determined based on deep seismic survey data it should be noted that a fundamental change of trend of the relative secular variations was observed at the slope of the precambrian platform after analysing the geomagnetic field observed along profile p4 the hypothesis that the contact between phanerozoic and precambrian europe lies in poland s territory can be proven

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

different modes of the late cretaceous early tertiary inversion in the north german and polish basins several selected seismic lines are used to show and compare the modes of late cretaceous early tertiary inversion within the north german and polish basins these seismic data illustrate an important difference in the allocation of major zones of basement thick skinned deformation and maximum uplift within both basins the most important inversion related uplift of the polish basin was localised in its axial part the mid polish trough whereas the basement in the axial part of the north german basin remained virtually flat the latter was uplifted along the sw and to a smaller degree the ne margins of the north german basin presently defined by the elbe fault system and the grimmen high respectively the different location of the basement inversion and uplift within the north german and polish basins is interpreted to reflect the position of major zones of crustal weakness represented by the wnw ese trending elbe fault system and by the nw se striking teisseyre tornquist zone the latter underlying the mid polish trough therefore the inversion of the polish and north german basins demonstrates the significance of an inherited basement structure regardless of its relationship to the position of the basin axis the inversion of the mid polish trough was connected with the reactivation of normal basement fault zones responsible for its permo mesozoic subsidence these faults zones inverted as reverse faults facilitated the uplift of the mid polish trough in the order of 1 3 km in contrast inversion of the north german basin rarely re used structures active during its subsidence basement inversion and uplift in the range of 3 4 km was focused at the elbe fault system which has remained quiescent in the triassic and jurassic but reproduced the direction of an earlier variscan structural grain in contrast n s oriented mesozoic grabens and troughs in the central part of the north german basin avoided significant inversion as they were oriented parallel to the direction of the inferred late cretaceous early tertiary compression the comparison of the north german and polish basins shows that inversion structures can follow an earlier subsidence pattern only under a favourable orientation of the stress field a thick zechstein salt layer in the central parts of the north german basin and the mid polish trough caused mechanical decoupling between the sub salt basement and the supra salt sedimentary cover resultant thin skinned inversion was manifested by the formation of various structures developed entirely in the supra salt mesozoic cenozoic succession the zechstein salt provided a mechanical buffer accommodating compressional stress and responding to the inversion through salt mobilisation and redistribution only in parts of the ngb and mpt characterised by either thin or missing zechstein evaporites thick skinned inversion directly controlled inversion related deformations of the sedimentary cover inversion of the permo mesozoic fill within the mid polish trough was achieved by a regional elevation above uplifted basement blocks conversely in the north german basin horizontal stress must have been transferred into the salt cover across the basin from its sw margin towards the basins centre this must be the case since compressional deformations are concentrated mostly above the salt and no significant inversion related basement faults are seismically detected apart from the basin margins this strain decoupling in the interior of the north german basin was enhanced by the presence of the elbe fault system which allowed strain localization in the basin floor due to its orientation perpendicular to the inferred late cretaceous early tertiary far field compression

palaeozoic terranes and their lithospheric boundaries within the trans european suture zone tesz a review the trans european suture zone tesz is a broad and complex zone of terrane accretion separating ancient lithosphere of the baltic shield and east european craton eec from the younger lithosphere of western and southern europe there is debate about the number of terranes involved and their origins the most significant terrane boundaries originally oceanic sutures are poorly exposed and are defined using faunal provinciality prominent geophysical lineaments may represent sub terrane boundaries within composite terranes the avalonia composite terrane was amalgamated to baltica in latest ician time the provenance of the malopolska and moravo silesian terranes whose neoproterozoic basement is suspect with respect to baltica but with which they nonetheless share faunal affinities is still debated the extent of the variscide rhenohercynian zone defines the southern limit of the early palaeozoic accreted terranes terranes within the bohemian massif exhibit hp metamorphism recording subduction driven collision prior to incorporation in the tesz collage itself associated with a hp event in romania the saxothuringian zone and rheic suture are directly juxtaposed with the eec and the crustal structure of the tesz has been much modified by post palaeozoic tectonism deep seismic reflection data where available show that the oceanic sutures are frequently associated with inclined reflectivity zones irz in the lithospheric mantle here inferred to mark relict subduction zones interpreting the age of subduction is complicated by offset of originally coplanar mantle and crustal segments of the irz resulting from early orogenic lithospheric delamination at the moho interface and or post orogenic reordering processes the mantle irz appear to indicate a n directed polarity for early palaeozoic subduction apparently incompatible with the geological evidence which indicates subduction of the tornquist sea beneath avalonia and a large amount of underthrusting of avalonia by baltica possible explanations for these apparently incompatible observations are evaluated

comment on depth to basement for the east european craton and teisseyre tornquist zone in poland based on potential field data by mikolajczak et al the comment outlines arguments questioning the concept of a gradually dipping crystalline basement of the east european craton across the teisseyre tornquist zone as argued by mikolajczak et al int j earth sci 108 547 567 2019 the results of the gravity modelling and qualitative structural interpretation presented in the commented paper should be taken with care particularly so when considered as a basis for further far reaching regional interpretations

contrasting tectonic and sedimentary history of the central and eastern parts of the polish carpathian foredeep basin results of seismic data interpretation polish carpathian foredeep basin pcfb is located at the junction between western and eastern european platforms such location caused different evolution of various parts of this basin in the central part of the pcfb growth fault propagation folds related to latest badenian stages of thrusting in this segment of the carpathians developed only minor normal faulting related to miocene reactivation of older basement faults was detected paleovalleys mapped within the mesozoic basement were interpreted as palaeogene tectonically controlled erosional features developed after inversion of the polish trough in the central pcfb post evaporitic sediments were supplied into the foredeep basin from south from the eroded carpathians in the eastern part of the pcfb a system of large normal faults related to miocene flexure induced reactivation of inherited mesozoic faults was identified within the hangingwall of this system reverse faults rotated blocks and basement pop up structures were described their formation was related to combined effect of compressional stresses transferred from the carpathian collision zone and reactivation of older large scale fault caused by both flexural extension and strike slip movements during deposition of the miocene foredeep sediments differential compaction also played an important role gentle onlap of the middle badenian evaporites by post evaporitic sediments towards the nw was interpreted as a result of tectonically driven relative sea level rise and re establishment of marine connections with eastern paratethys

the rugen caledonides northeast germany borehole evidence from the isle of rugen and geophysical data from the adjacent baltic sea suggest a caledonian deformation front that caused nne directed thrusting on the east european platform it is thought to mark a caledonian suture zone which was reactivated in syn to post variscan events to form the romio mon fault zone

the margins of avalonia during cambrian and earliest ordovician times avalonia was an area forming an integral part of the huge gondwanan continent probably along the northern margin of amazonia until in early ordovician late arenig or llanvirn time it split off from gondwana leaving a widening rheic ocean to its south today its southern margin with gondwana extends northeast from east of cape cod massachusetts through nova scotia north of the meguma terrane and thence below sea level to the south of newfoundland on the eastern side of the present atlantic the southern margin may separate southwest portugal from the rest of the iberian peninsula it can be traced eastwards with more certainty from the south cornwall nappes to a line separating the northern phyllite belt on the southern margin of the rhenohercynian terrane and the mid german crystalline high there is no certain evidence of avalonian crust to the northeast of the elbe line the northern margin of avalonia extends westwards from south of denmark to the british isles where it merges with the iapetus ocean suture between scotland and england traced westwards it crosses ireland and reappears in northern newfoundland to the east of new world island where it may follow the trace of the dog bay line and the cape ray fault recent work suggests that the northern margin of avalonia may clip the northern tip of cape breton island in nova scotia and then enter the north american mainland at the bay of chaleur it may then be traced from north and west of the popelogan and bronson hill arcs to long island sound near newhaven connecticut the cambrian to devonian faunas reflect the history of avalonia initially they were purely gondwanan but as ordovician time proceeded more genera crossed firstly the tornquist ocean as it narrowed between avalonia and baltica to close in latest ordovician and early silurian times and secondly the iapetus ocean so that by the early silurian most of the benthic shelly faunas apart from the ostracods were the same round the adjacent margins of all three palaeocontinents

reply to comment by m narkiewicz on depth to basement for the east european craton and teisseyre tornquist zone in poland based on potential field data by mikolajczak et al international journal of earth sciences 2019 108 547 567

architecture and orogenic evolution of the northeastern outer carpathians from cross section balancing and forward modeling abstract new balanced and restored cross sections and a 2d kinematic model illustrate the present geometry of the northeastern outer carpathians and quantify their orogenic evolution between the late eocene and the late miocene 35 3 to 11 0 ma the balanced cross section is built on extensive surface and subsurface data and depicts an imbricate fan internally stacked along high displacement out of sequence thrusts section restoration yielded 507 km of minimum orogenic shortening at least 230 km more than proposed in previous studies our shortening estimate relies on accurate thicknesses of lithostratigraphic units in most cases thinner than applied before the average convergence rate between 35 3 and 11 0 ma is estimated at 20 8 km my the forward model constrained by lower and upper ages of syn orogenic deposits traces the advance of the outer carpathian accretionary wedge and proves kinematic admissibility of the balanced and restored cross sections progradation rates of the foreland basin depositional sequences evolving from 9 11 km my between 41 5 and 21 1 ma to 22 39 km my between 21 1 and 11 0 ma suggest a two phase dynamics of the orogenic system the acceleration of foreland migration at 21 1 ma likely reflects the onset of northward subduction retreat linked to the rollback of the european lower plate that gave rise to coeval back arc extension in the pannonian basin

global statistical analysis of topex and poseidon data a global statistical analysis of the first 10 months of topex poseidon merged geophysical data records is presented the global crossover analysis using the cartwright and ray 1990 cr tide model and gaspar et al this issue electromagnetic bias parameterization yields a sea level rms crossover difference of 10 05 cm 10 15 cm and 10 15 cm for topex topex poseidon poseidon and topex poseidon crossovers respectively all geophysical corrections give reductions in the crossover differences the most significant being with respect to ocean tides solid earth tide and inverse barometer effect based on topex poseidon crossovers and repeat track differences we estimate the relative bias between topex and poseidon at about 15 5 1 cm this value is dependent however to the electromagnetic bias corrections used an orbit error reduction method based on global minimization of crossover differences over one cycle yields an orbit error of about 3 cm rms this is probably an upper estimate of the orbit error since the estimation absorbs other altimetric signals the rms crossover difference is reduced to 8 8 cm after adjustment a repeat track analysis is then performed using the cr tide model in regions of high mesoscale variability the rms sea level variability agrees well with the geosat results tidal errors are also clearly evidenced a recent tide model ma et al this issue determined from topex poseidon data considerably improves the rms sea level variability the reduction of sea level variance is 4 cm 2 on average but can reach 8 cm 2 in the southeast pacific southeast atlantic and indian oceans the rms sea level variability thus decreases from 6 cm to only 4 cm in quiet ocean regions the large scale sea level variations over these first 10 months most likely show for the first time the global annual cycle of sea level finally we analyze the topex and poseidon sea level anomaly wavenumber spectral characteristics topex and poseidon have identical spectral characteristics at low wavenumbers for wavelengths shorter than 100 km however poseidon spectra are more energetic this is probably related to the topex tracker characteristics and to the way the acceleration correction is made in the geophysical data records poseidon repeat track noise level is estimated at about 3 cm for a 1 s average the topex repeat track noise level is about 1 8 cm rms but this probably corresponds to averages over several seconds

using altimetry waveform data and ancillary information from srtm landsat and modis to retrieve river characteristics in this paper spaceborne radar altimeters are shown to have the potential for monitoring the height of large rivers with accuracies of approximately 1 m however the need for a better height accuracy and the observations of smaller continental basins have led to studies on how to improve and extend the use of nadir altimeter data conventional retracking techniques over land are limited to the examination of altimeter waveforms on a case by case basis due to the arbitrary geometry which may be present at altimeter river crossings this approach may be limited to large rivers which approximate ocean crossings to overcome this limitation we introduce a waveform fitting method which uses the entire set of waveforms associated with a water crossing rather than individual waveforms by using ancillary data such as digital elevation model obtained from shuttle radar topography mission and gtopo30 and classification maps obtained from landsat and modis it is possible to recast the retracking problems as a maximum likelihood estimation problem theoretical power returns based on the a priori knowledge of the observed scenes are generated resulting in a parametric library of waveform histories which is then used to constrain the estimation for demonstration we concentrate on the river meuse in northern western europe and on the river lena in russia the meuse has important social impact since it has flooded in the past and better real time predictions of its changing stage may improve flood forecasting skill furthermore it presents a challenge to conventional nadir altimeter waveform retracking we will present both theoretical performance results and demonstrate the feasibility based on real altimeter data

reflection seismic constraints on paleozoic crustal structure and moho beneath the ne german basin abstract a 330 km long ne sw trending seismic transect across the ne german basin combined with a 75 km long perpendicular cross line in the basin centre reveals the structure of this intracontinental basin between the stable precambrian baltic shield and the weaker mid european variscides the combination of high fold vibroseis and low fold explosive seismic profiling images both upper and lower crustal structures in detail distinct faults related to a rift stage are not observed below the permian sedimentary basin but there is evidence of lower crustal thinning a moho pattern less reflective below the basin centre than at the margins may be related to magmatic underplating the rather flat lying moho dips slightly towards the basin margins structures further north suggest a southern extent of baltica below the ne german basin the caledonian accretionary wedge may be outlined by sw dipping mid crustal reflectors beneath the basin

a palaeomagnetic study of the builth wells llandrindod wells ordovician inlier wales palaeogeographic and structural implications summary discrepancies exist in the southern british ordovician palaeomagnetic data set with individual studies indicating either high southerly or temperate southerly palaeolatitudes although previous palaeomagnetic investigations from the builth inlier have delineated a three component remanence structure doubts have been raised concerning i the magnetization age of the supposed primary component p ii the structural setting of the sampling area llanelwedd quarry within a zone of strike slip deformation and iii whether detailed step wise demagnetization has fully separated the various magnetization components in addressing these problems we present new palaeomagnetic results as follows i a positive palaeomagnetic conglomerate test establishing a pre late llanvirn age for component p ii an enlarged geographic sampling embracing several tectonic domains indicating that relative rotations linked to strike slip tectonism are minor within the builth sampling area and iii evidence that component p is uncontaminated by overprints at some sites suggesting the resulting palaeolatitude of 35 s to be representative for the builth inlier we also present evidence for local syn volcanic deformation within llanvirn volcanics and for intrusion related deformation of llanvirn shales when the revised llanvirn pole from the inlier 3 s 4 e is combined with other data from southern britain in a statistical spline analysis a mean palaeolatitude of 44 5 s is calculated for builth in llanvirn times a palaeoreconstruction for 468 474 ma c mid llanvirn is presented utilizing this analysis

deep seismic survey images crustal structure of tornquist zone beneath southern baltic sea the tornquist zone is europe s longest tectonic lineament and bisects the continent in a nw se direction from the north sea off nw denmark to the black sea new deep seismic reflection and coinci

baltica a synopsis of vendian permian palaeomagnetic data and their palaeotectonic implications torsvlk t h smethurst m a van der voo r trench a abrahamsen n and halvorsen e 1992 baltlca a synopsis of vendlan permmn palaeomagnetic data and their palaeotectonlc implications earth sci rev 33 133 152 in light of recent additions to the palaeozoic palaeo magnetlc data base particularly for the ordovlclan era a revised apparent polar wander apw path for baltica has been constructed following a rigorous synthesis of all late precambrlan perm lan data the apw path is characterized by two prominent loops firstly a late precambrlan camb rlan loop probably relating to a rifting event and secondly a younger loop relating to a mid silurian scandlan colhsion event these features imply major change in plate tectonic reconfiguratlon baltlca probably represented an individual continental unit m early palaeozoic times and was positioned m high southerly latitudes in an inverted geographic orientation in such a reconstruction baltlca was separated from the northern margin of gondwana by the tornqulst sea and from laurentla by the iapetus ocean the tornqulst zone is thus interpreted as a passive or dextral transform margin during the early palaeozoic while undergoing counter clockwise rotations up to 1 6 ma baltica drifted northward through most ol the palaeozoic except for a short period of southerly movement in late silurian early devonian times after colhslon with laurentla rapid movements in latitude up to 9 cm yr are noted m late precambrlan earl y palaeozoic times and slgmficant decrease in velocities throughout palaeozoic time probably reflect the progressive amalgamation of a larger continent by early devonian euramerlca and permian pangea times the tornqulst sea had a principal component of palaeo east west orientation hence it is difficult to be precise in the timing of when micro continents such as eastern avalonla and the european masslfs ultimately collided along the southwestern margin of baltica these micro continents are considered to have been peripheral to gondwana m high southerly latitudes during the early ordovlclan eastern avalonla clearly had rifted off gondwana by llanvlrn llanded o times and may have collided with baltlca during late ordovlclan times although the present available sdunan palaeomagnetlc data from eastern avalonia may suggest colhslon in late silurian times across the lapetus facing margin of baltica laurentla was s tuated in equatorml to southerly latitudes during most of the lower palaeozoic these continents collided in mid silurian times l e a first collision between southwestern norway and greenland scotla nd which gave rise to the early scandlan orogeny 425 ma in southwestern norway possible followed by a later but less dramatic scandlan event in northern norway at around 410 ma since baltlca was geographically reverted m early palaeozoic times the colhsional margin could not have been a margin that once rifted off laurentm as assumed in a number of plate tectonic models

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

the ordovician history of the iapetus ocean in britain new palaeomagnetic constraints new late tremadoc early arenig palaeomagnetic results from sw wales imply that s britain part of eastern avalonia occupied a southerly latitude of c 60 s in early ordovician times when combined with scottish ordoviaan palaneomagnetic data which indicate a 15 s latitude the results indicate that the british sector of the iapetus ocean reached n latitudinal width of c 5000 km in tremadoc arenig times which was reduced to c 3000 km by llanvirn llandeilo mid ordovician times the new data resolve two previous controversies in palaeozoic palaeogeography first the high southerly palaeolatitude links avdonia to gondwana marginal to w africa thus reconciling codlicting reconstructions based upon either palaeomagnetic or faunal facies evidence alone second reliable llanvim palaeomagnetic data imply that avlonia had rifted northwards by arenig time whereas armorica remained proximal to northern africa throughout the ordovician the combined data therefore establish that avdonia and armorica formed separate micro continents when rifting from gondwana

depth to basement for the east european craton and teisseyre tornquist zone in poland based on potential field data results of a depth to basement study are presented for the east european craton and the teisseyre tornquist zone ttz in poland the terrestrial gravity data are inverted for the top of the paleoproterozoic basement and independently for the top of the ediacaran using seismic horizons from the polandspan seismic survey and well tops as input depth measurements the depth to the ediacaran modelling was additionally extended to cover the ysogory block and northern malopolska block the results are visualised as isobath maps for the top of the paleoproterozoic basement and top of the ediacaran and an isopach map for the ediacaran supplemented with qualitative structural interpretation based on gravity and magnetic data the results of modelling show a smooth crystalline basement slope within the ttz with the top of the paleoproterozoic basement uniformly descending south westwards by 10 14 km the thickness of the ediacaran in se poland increases in the same direction to more than 10 km within the ttz such a crustal architecture in combination with the earlier documented moho elevation of 4 6 km reveals significant thinning of the paleoproterozoic crust within the ttz to form a crustal necking zone due to the ediacaran rifting a smooth geometry of the top of basement along with the lack of basement rooted faults suggests a ductile mode of crustal thinning during rifting of rodinia moreover the development of the nw se oriented rift a precursor of the tornquist ocean was associated with rifting in a ne sw direction parallel to the orsha volyn rift

transcurrent nature of the teisseyre tornquist zone in central europe results of the polcrust 01 deep reflection seismic profile teisseyre tornquist zone ttz corresponds to a crustal boundary between the precambrian east european platform eep and the palaeozoic west european platform although the zone has been controlling phanerozoic evolution of large parts of central europe its course geometry and origin are still poorly constrained deep reflection seismic profile polcrust 01 recently acquired in se poland for the first time allowed a precise comparison of the ediacaran and later tectonic patterns to the deep crustal features of the ttz and adjacent areas the ttz corresponds to the subvertical tomaszow fault separating the radom kra nik elevation composed of the typical eep crust from the bilgoraj narol block bnb in the sw with a thinned crystalline basement showing affinities to the eep crust the bnb is a part of the larger caledonian ysogory terrane as evidenced by its lower palaeozoic stratigraphy and gravity data thus for the first time the proximal baltican affinity of this unit has been documented unambiguously the ysogory terrane is delimited from the sw by the subvertical cieszanow fault zone corresponding to the holy cross suture the adjacent malopolska terrane is characterized by a distinct early palaeozoic stratigraphy and lower middle crust exhibiting sw dipping reflective packages interpreted as ne verging thrust and shear zones of a neoproterozoic orogen the observations from the polcrust 01 profile and regional comparisons indicate that the ttz is a major caledonian transcurrent zone between poland and east romania in central poland the ttz likely forms a narrow subvertical contact between the eep and a proximal kuiavia terrane as constrained by the deep refraction seismic data to the nw the zone extends towards the pomeranian part of the caledonide fold and thrust belt related to the avalonia baltica collision zone thor suture south east of poland the ttz corresponds to the rava ruska fault zone established as a caledonian suture separating adjacent terrane probably of a baltican affinity the east romanian part of the ttz conforms with the sf ntu gheorghe fault separating reworked eep crust of the pre dobrogean depression from the north dobrogea unit bearing a strong variscan and cimmerian overprint

contrasting sources of late paleozoic rhyolite magma in the polish lowlands evidence from u pb ages and hf and o isotope composition in zircon the polish lowlands located southwest of the teisseyre tornquist zone within trans european suture zone were affected by bimodal but dominantly rhyolitic magmatism during the late paleozoic thanks to the inherited zircon they contain these rhyolitic rocks provide a direct source of information about the pre permian rocks underlying the polish lowland this paper presents zircon u pb geochronology and hf and o isotopic results from five drill core samples representing four rhyolites and one granite based on the ratio of inherited vs autocrystic zircon the rhyolites can be divided into two groups northern rhyolites where autocrystic zircon is more abundant and southern rhyolites where inherited zircon dominates we suggest that the magma sources and the processes responsible for generating high silica magmas differ between the northern and southern rhyolites isotopically distinct sources were available during formation of northern rhyolites as the hf and o isotopes in magmatic zircon differ between the two analysed localities of northern rhyolites a mixing between magmas formed from baltica derived mudstone siltstone sediments and avalonian basement or mantle can explain the diversity between the zircon compositions from the northern localities daszewo and wysoka kamienska conversely the southern rhyolites from our two localities contain zircon with similar compositions and these units can be further correlated with results from the north east german basin suggesting uniform source rocks over this larger region based on the ages of inherited zircon and the isotopic composition of magmatic ones we suggest that the dominant source of the southern rhyolites is variscan foreland sediments mixed with baltica avalonia derived sediments

detrital composition of ordovician sandstones from the rugen boreholes implications for the evolution of the tornquist ocean the lower palaeozoic sequences of the rugen boreholes are composed of pelitic clastic sediments which range in age from the cambro ordovician boundary to the late ordovician provenance studies have been carried out on cambro ordovician sandstones from the loissin borehole and on middle upper ordovician greywackes of the rugen 5 borehole

seismic images of caledonian lithosphere scale collision structures in the southeastern north sea along mona lisa profile 2 abstract the unexposed suture between baltica and eastern avalonia is imaged by coincident normal incidence reflection and wide angle reflection refraction seismic data of the mona lisa project we present new results of the upper lithospheric seismic structure from the n s striking profile 2 across the caledonian deformation front which represents the crustal collision suture between baltica and eastern avalonia that formed after closure of the tornquist sea during the caledonian orogeny in late ordovician times three different crustal types are identified with great similarities to the nearby profile 1 1 a three layered crust typical of shields to the north 2 a transitional crust suture zone in the central part and 3 a two layered crust of caledonian origin to the south characterized by very low velocities throughout the crust the crustal thickness varies from 38 35 km under the northern margin of the ringkobing fyn high baltica crust to 28 27 km beneath the north german basin in the caledonian crust to the south the suture zone is imaged by s dipping crustal reflections from 1 9 to 10 6 s two way travel time twt over a horizontal distance of 70 km within the transitional crust the reflection suture zone terminates in a 60 km wide reflective lens with velocities of 6 6 6 8 km s in the lowermost crust the reflective lens may be interpreted as a remnant of oceanic or island arc crust that was accreted to the leading edge of baltica during closure of the tornquist sea alternatively the reflective lens may represent an indentor of baltica crust into the avalonian terrane the change in lower crustal reflectivity and the abrupt transition from a three to a two layered crust further south suggest that the trans european fault and the elbe lineament continue into the north sea the upper mantle reflectivity is dominated by bands of strong amplitude s dipping reflections from 13 5 to 21 8 s twt and a weaker band of n dipping reflections from 12 to 16 s twt reversed wide angle refractions and reflections indicate the presence of a s dipping high velocity layer 8 65 8 8 km s in the uppermost mantle the sub moho high velocity layer partially coincides with the strong s dipping normal incidence mantle reflections we propose that the s dipping mantle structure may represent a late caledonian or late carboniferous to early permian mantle shear zone

caledonian and proterozoic terrane accretion in the southwest baltic sea abstract a marine seismic reflection survey was carried out in 1996 by dekorp potsdam and bgr hannover in the sw baltic sea several tectonic lineaments were crossed nearly perpendicularly for example the caledonian deformation front which is assumed to mark the northern boundary of the terrane avalonia which accreted to baltica ca 400 ma here a bivergent collision is clearly observed confirming early ideas from the babel survey the ne dipping reflections in the uppermost mantle are interpreted as signs of the subducted tornquist ocean a similar tectonic style of compression and indentation is observed in the proterozoic crust northeast of bornholm where in addition a remarkable crustal thickening and a strong increase of reflection power is observed the three dekorp lines in this area provide a certain three dimensional control and allows extension of similar observations from the babel line a southward this proterozoic terrane accretion seems to be connected to major tectonic lineaments in southern sweden either to the gothian thrust or the sveconorwegian front

riphean rifting and major palaeoproterozoic crustal boundaries in the basement of the east european craton geology and geophysics abstract the east european craton which occupies the northeastern half of the european continent is characterized by the presence of giant even transcratonic systems of riphean meso to neoproterozoic rifts aulacogens the largest of these riphean rift systems tend to follow the course of palaeoproterozoic sutures and junction zones that subdivide the craton into three crustal segments with autonomous development histories these segments named fennoscandia volgo uralia and sarmatia are marked by distinct t magsat anomalies genetically the intersegment junction zones represent different types of collisional and accretional interaction between the component crustal segments of the craton in accordance with this the riphean rift systems vary in width the presence or absence of moho uplifts and other properties like for instance heat flow values however all of them follow belts of weakly magnetized crust studded with local magnetic maxima due to the presence of mafic rocks associated with the rifting the rift system intersegment junction zone relationships in consequence similarly represent a range of variation and cannot be referred to one single model

effects of sea maturity on satellite altimeter measurements for equilibrium arid near equilibrium sea states the wave slope variance is a function of wind speed u and of the sea maturity the influence of both factors on the altimeter measurements of wind speed wave height and radar cross section 0 is studied experimentally the necessary theoretical background both on wave statistics and on the near nadir radar backscatter is outlined it is based on a recently proposed view that the effective fractal dimension for a surface patch corresponding to the equilibrium range of wave spectra increases as the wave field matures the experimental part is based on 1 year s worth of geosat altimeter observations colocated with in situ wind and wave measurements by 20 noaa buoys errors and biases in altimeter wind speed and wave height measurements are investigated a geophysically significant error trend correlated with the sea maturity i e with c0 u where c0 is the phase velocity of waves corresponding to the spectral peak and u is the mean wind speed well above the surface is found in wind speed measurements this trend is explained by examining the effect of the generalized wind fetch x gh1 32 u2 on the curves of the observed dependence 0 f u x we conclude in particular that unambiguous measurements of wind speed by altimeter in a wide range of sea states are impossible without accounting for the actual degree of wave development an approach to a more accurate retrieval of wind speeds is suggested as based on accounting for the actual degree of wave development which can be achieved through processing the total radar cross section simultaneously with the significant wave height information contained in altimeter waveforms the potential capability of a satellite altimeter to estimate wave age and similar measures of wind wave coupling is discussed this capability expands the use of satellite altimeters for air sea interaction studies

the corrections for significant wave height and attitude effects in the topex radar altimeter the routine ground processing of data from the nasa radar altimeter of topex poseidon includes instrument corrections for the effects of significant wave height and attitude angle changes on the altimeter s estimates of range backscattered power and significant wave height this paper describes how these instrument corrections were generated and how they are applied detailed waveform fitting to telemetered waveform samples is used to assess the effectiveness of the corrections there are several altimeter hardware caused small waveform departures from the model waveforms and these departures designated waveform features are described in detail a consequence of the waveform features and their positioning relationship to range rate is that range data for ground tracks moving toward the equator may differ systematically by about a centimeter compared to range data for ground tracks moving away from the equator the results and discussion are limited to side a of the redundant altimeter as only side a has been operated on orbit

pomeranian caledonides nw poland a collisional suture or thin skinned fold and thrust belt abstract a main goal of this study was to understand the character of the caledonian deformation front in pomerania nw poland and its relationship to the adjoining teisseyre tornquist zone ttz in the context of the avalonia baltica early palaeozoic collision since the pomeranian caledonides are concealed beneath 1 4 km thick platform cover of upper palaeozoic and mesozoic sediments we used a combination of potential field seismic and well data to investigate the basement architecture and structure of the lower palaeozoic rocks starting from a qualitative review of gravity and magnetic data we built a 2d gravity and magnetic model upon the polandspan pl1 5600 seismic reflection line and applied 3d gravity inversion for a depth to basement study using well tops a top lower palaeozoic horizon and lower palaeozoic isopach map were created we found out that the pomeranian caledonides represent a thin skinned fold and thrust belt involving ordovician and silurian sediments of the caledonian foreland basin the deformation front was developed due to the buttressing effect of a basement ramp occurring directly above the ttz the latter corresponds to a precambrian suture zone overprinted by successive extensional tectonics and buried beneath the foreland basin in northern poland the suture is defined by a remnant crustal keel still preserved underneath the ttz probably resulting from precambrian collision during formation of the rodinia paleocontinent we propose that the extension of the thor suture separating baltica and avalonia must exist west from the ttz probably in the rugen area in our interpretation the ttz represents an intra cratonic crustal discontinuity comparable to its nw prolongation the sorgenfrei tornquist zone that runs across the baltic sea sweden and denmark consequently the basement underlying the palaeozoic platform in nw poland may be considered to have been part of baltica in early palaeozoic times

a new isostatic residual gravity map of the conterminous united states with a discussion on the significance of isostatic residual anomalies to display more clearly the gravity anomalies caused by geologic bodies in the upper parts of the crust a new colored isostatic residual gravity map of the conterminous united states has been prepared using the gravity data set compiled for the gravity anomaly map of the united states society of exploration geophysicists 1982 the new isostatic residual gravity map is based on an airy heiskanen model of local compensation in which the surface load requiring compensation is defined by 5 min topographic and bathymetric data sets a colored first vertical derivative map of isostatic residual gravity further enhances the short wavelength anomalies produced by bodies at or near the surface and emphasizes the regional fabrics and trends in the gravity field for the purpose of displaying gravity anomalies caused by shallow bodies of geologic significance the nature of the isostatic model and the values of its parameters are of lesser importance than the application of an isostatic correction of some sort most isostatic models result in residual gravity maps that appear nearly identical in their main patterns and features anomalies on isostatic residual gravity maps should not be casually interpreted in terms of undercompensation or overcompensation because large amplitude anomalies can be produced by crustal bodies in complete local isostatic equilibrium many isostatic residual gravity anomalies less than several hundred kilometers wide can be related to known geologic bodies we present here a classification scheme that attempts to categorize such anomalies on the basis of tectonic environment in general highs correlate with intruded or accreted mafic material or with upthrusted crustal sections whereas lows occur over low density sedimentary or volcanic sections felsic intrusive bodies or down warped crustal sections although some longer wavelength anomalies such as the broad gravity high centered over montana could be manifestations of density contrasts deep in the mantle many such anomalies can also be modeled by geologically reasonable density contrasts that are isostatically compensated and confined to depths of less than several hundred kilometers so that their source bodies need not be deep the fact that certain of these broader anomalies have well defined boundaries which correlate with near surface geologic features increases the likelihood that their sources lie entirely within the lithosphere if so then the density contrasts required to explain the gravity data imply fundamental anomalies in chemical composition or thermal state for the crustal and upper mantle columns under these regions we have investigated spectral analysis as a method to quantitatively characterize regional anomaly patterns contoured plots of normalized amplitude spectra were prepared for various areas of the isostatic residual gravity field of the united states these fourier domain representations show characteristic patterns that can be interpreted in terms of the trends and wavelengths of anomalies and may help to more objectively distinguish geologic basements with different origins or tectonic histories

late vendian early palaeozoic tectonic evolution of the baltic basin regional tectonic implications from subsidence analysis abstract subsidence analysis was performed on 43 boreholes penetrating the upper vendian lower palaeozoic sedimentary succession of the baltic basin the results were related to lithofacial and structural data to elucidate subsidence mechanisms and the regional tectonic setting of basin development tectonic subsidence patterns are consistent throughout the basin for the time period studied an extensional tectonic subsidence event possibly of two phases is indicated from the late vendian to the beginning of the middle cambrian this event is seen in the southwestern part of the baltic basin peri tornquist zone until the earliest cambrian after which it is also observed in the sw ne trending baltic depression part of the basin basin development during this time is interpreted as recording the latest stages of break up of the precambrian super continent rodinia and ultimately the formation of the tornquist sea the late middle cambrian to middle ordovician tectonic subsidence pattern of the baltic basin is characteristic of post rift thermal subsidence of the newly formed passive continental margin of baltica developed along its southwestern edge a gradual increase in subsidence rate is observed from the middle late ordovician and throughout the silurian particularly for ludlow and pridoli times creating subsidence curves with convex shapes typical of foreland basin development the rate of late silurian tectonic subsidence increases significantly towards the southwest margin of the baltic basin adjacent to the present location of the north german polish caledonides the baltic basin therefore appears to have developed primarily as a flexural foreland basin during silurian oblique collision of baltica and eastern avalonia a foreland setting is supported by the influx of distal turbidites into the basin from southwest sources in the late silurian compressional deformation structures of early devonian lochkovian age are seen in seismic sections in the central part of the baltic basin lithuania these together with a change in subsidence pattern mark the end of the caledonian stage of basin development of the baltic basin

caledonian deformation upon southwest baltica and its tectonic implications alternatives and consequences the continuation of the basement of the southwestern baltic shield toward the sw is of major interest for the caledonian evolution in the southwestern baltic sea and northern germany a reinterpretation of various marine seismic data suggests a reconsideration of the caledonian collision pattern the sorgenfrei tornquist zone forming the northwestern extension of the tornquist zone is regarded as the northeasterly boundary fault and the elbe lineament is regarded as the southwestern limit of an area which suffered from the docking of east avalonia to baltica it shows many northwestsoutheast striking structures anomalies and fault patterns from our studies two alternative models emerge one which considers the caledonian deformation front as the northeastern limit of east avalonia and a zone of major transpression collision and subduction of the tornquist sea another model considers the elbe lineament in schleswig holstein nw germany as a major dextral strike slip fault which is interpreted as the northeasterly limit of east avalonia and the southwest boundary of the baltic shield along the elbe lineament the tornquist sea plus rotating avalonia were displaced to the northwest a large part of the area to be studied might have developed into a passive margin toward the upper ordovician a decision which of the two models is to be prefered has to be the major goal of future geophysical experiments

geomechanical and geochemical effects on sandstones caused by the reaction with supercritical co2 an experimental approach to in situ conditions in deep geological reservoirs the geochemical and geomechanical behaviour of reservoir rocks from deep saline aquifers during the injection and geological storage of co2 is studied in laboratory experiments a combination of geochemical and geomechanical studies was carried out on various sandstones from the north german basin after the mineralogical geochemical and petrophysical characterization a set of sandstone samples was exposed to supercritical sc co2 and brine for 2 4 weeks in an autoclave system one sample was mineralogically and geochemically characterised and then loaded in a triaxial cell under in situ pressure and temperature conditions to study the changes of the geomechanical rock properties after treatment in the autoclaves geochemical alterations mainly in the carbonate but also in the sheet silicate cements as well as in single minerals of the sandstones were observed affecting the rocks granular structure in addition to partial solution effects during the geochemical experiments small grains of secondary carbonate and other mineral precipitations were observed within the pore space of the treated sandstones results of additional geomechanical experiments with untreated samples show that the rock strength is influenced by the saturation degree the confining pressure the pore fluid pressure and temperature the exposure to pure scco2 in the autoclave system induces reduced strength parameters modified elastic deformation behaviour and changes of the effective porosity in comparison to untreated sandstone samples experimental results show that the volume of pore fluid fluxing into the pore space of the sandstones clearly depends on the saturation level of the sample

polonaise 97 an international seismic experiment between precambrian and variscan europe in poland abstract the trans european suture zone tesz comprises a series of sutures that developed by palaeozoic amalgamation of the phanerozoic central europe onto the proterozoic baltica and east european plate during the formation of pangea within tesz the permian basin in poland forms the easternmost part of the permian central european basin which is bordered on the east by the east european craton eec and on the southwest by the bohemian massif the axis of the basin the mid polish trough parallels the edge of the eec the teisseyre tornquist zone ttz is a geological inversion zone in the polish trough a large seismic experiment the polonaise 97 project was conducted in poland during may of 1997 and targeted the deep structure of the tesz and the complex series of upper crustal features associated with it it included contributions from the geophysical communities in poland denmark the usa lithuania germany finland sweden and canada this large lithospheric seismic experiment deployed 613 instruments to record 64 shots along five profiles with a total length of about 2000 km moreover five multichannel seismic reflection stations 90 and 120 channels recorded all signals from shots two dimensional velocity models were derived by p wave tomographic inversion these models provide an initial interpretation of this massive data set and allow us to present a few significant seismic and tectonic observations one of the most important is a very distinct asymmetry between the maximum thickness of the sedimentary cover in the polish trough 16 20 km and the crustal root 50 km associated with tesz ttz

corections for the effects of significant wave height and attitude on geosat radar altimeter measurements range estimates from a radar altimeter have biases which are a function of the significant wave height swh and the satellite attitude angle based on results of pre launch geosat modeling and simulation by the johns hopkins applied physics laboratory a correction for swh and attitude was already applied to the sea surface height estimates from geosat s production data processing by fitting a detailed model radar return waveform to geosat waveform sampler data we can provide an independent estimate of the height bias due to swh and attitude angle the waveform fitting also produces independent estimates of the swh and of the attitude angle the waveform fitting has been carried out for 10 s averages of geosat waveform sampler data over a wide range of swh and attitude values our results confirm that geosat sea surface height correction is good to well within the original decimeter level specification but that an additional height correction can be made at the several centimeter level our results are expressed as additive corrections to the noaa distributed geosat estimates of sea surface height swh and attitude and we provide coefficients for the polynomial expressions for these corrections

retracking ers 1 altimeter waveforms for optimal gravity field recovery summary we have reprocessed ers 1 radar altimeter waveforms using an algorithm designed to minimize sea surface slope error and decouple it from significant wave height swh error standard waveform retracking estimates three parameters arrival time swh and amplitude we show that errors in retracked estimates of arrival time and swh are inherently correlated because of the noise characteristics of the returned waveform this suggests that some of what is called sea state bias in the literature may be caused by correlated errors rather than true electromagnetic or skewness bias we have developed a retracking algorithm that reduces this error correlation and makes the resolution of sea surface slope signals independent of sea state the main assumption is that the swh varies smoothly along the satellite track over wavelengths of 90 km this approach reduces the rms error in sea surface slope to only 62 per cent of that of standard retracking methods while our method is optimized for gravity field recovery it may also improve the resolution of sea surface height signals of interest to physical oceanographers

postprocessing of satellite altimetry return signals for improved sea surface topography accuracy large off nadir attitude deviations and high surface wave heights cause an alteration in the ocean return signal from a satellite radar altimeter this leads to an error in the on board calculation of the height measurement the error can be removed by reprocessing the full radar return signal on the ground in the ground processing the correct tracking point in the return signal is recomputed through a procedure called retracking there has been a controversy over whether or not all altimeter data would be retracked this study analyzes retracked southern ocean data from the first 34 repeat cycles of the geosat exact repeat mission erm covering november 1986 through april 1988 the final data set consists of over 2 5 million smoothed one per second measurements of the ocean surface the significant wave height swh distribution as given on the noaa geophysical data records gdrs for these measurements peaks at around 2 1 m 19 of the measurements and drops down almost linearly to 2 of the measurements at 5 8 m there are over 1100 observations with swh greater than 15 m the difference between the surface heights calculated from the retracked data and the original on board estimates is less than 10 cm for swh less than 10 m but increases to approximately 1 0 m at a swh of 18 m in general the electromagnetic em bias coefficient calculated using the retracked data is slightly less than that using the unretracked data and does not decrease as much with swh as do the em bias coefficients calculated from the unretracked data a map of the sea surface height variability of the southern ocean created using the retracked data shows differences from variability maps created using the unretracked data in regions of high wave heights retracking can be done efficiently on modern unix work stations at 0 064 times real time acquisition this study shows that retracking will improve altimeter precision

insights into the magmatic architecture of the oslo graben by petrophysically constrained analysis of the gravity and magnetic field 1 a new model of the crustal structure of the oslo graben with a special emphasis on the location of magmatic intrusions is presented based on the interpretation of gravity and magnetic data constrained by petrophysical data seismics and surface geology three dimensional modeling shows that the gravity high above the oslo rift is caused by a combination of crustal thinning and the presence of a high density body in the upper crust related to precambrian gneiss complexes at the western flank of the rift the short wavelength gravity anomalies are correlated with the outcropping low density magmatic rocks of permian age that extend to the depths of 1 5 4 km in addition simultaneous modeling of aeromagnetic data sets collected at two flight altitudes 50 and 3400 m using susceptibility and remanence within a range of reasonable magnetic properties suggests an underlying intrusion with a depth extent up to 15 km magnetization and density of the intrusion are increasing with depth leading to a small density contrast but a large contrast in magnetization with the surrounding rocks therefore only modeling of the magnetic field can resolve the nature of the deep intrusions the three dimensional model provides a new estimate of the volume of magmatic material in the oslo graben system 63 000 km3 this is only two thirds of the values proposed earlier 95 000 km3 as we disregard high volume magmatic underplating correlation with structural data surface geology and deep lithospheric features shows that the distribution of extrusive rocks in the oslo rift can be related to the timing and onset of rifting

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

recognition of the trans european suture zone tesz by the palaeobiogeographical distribution pattern of early to middle ordovician acritarchs

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

the global frequency wavenumber spectrum of oceanic variability estimated from topex poseidon altimetric measurements two years of altimetric data from the topex poseidon spacecraft have been used to produce preliminary estimates of the space and time spectra of global variability for both sea surface height and slope the results are expressed in terms of both degree variances from spherical harmonic expansions and in along track wavenumbers simple analytic approximations both in terms of piecewise power laws and pade fractions are provided for comparison with independent measurements and for easy use of the results a number of uses of such spectra exist including the possibility of combining the altimetric data with other observations predictions of spatial coherences and the estimation of the accuracy of apparent secular trends in sea level