lithospheric dynamics and tectonic stratigraphic evolution of the ebro basin we present analysis of two dimensional modeling of the tectonic subsidence in the ebro basin along three profiles crossing the pyrenees the ebro basin and the catalan coastal range to the east and the iberic cordillera to the west the deformation of the foreland basin during tertiary times is simulated using a lithospheric flexure model incorporating laterally varying elastic thicknesses the deflection of the plate is the combined result of pyrenean loading and the loads exerted by the iberic cordillera and catalan coastal range in the eastern part of the ebro basin no extra driving force on the iberian plate is required the flexural modeling supports the hypothesis that underplating of the iberian plate under the european plate is not associated with subduction of old oceanic lithosphere a good fit with the tertiary basin subsidence data and bouguer anomalies is obtained for an elastic plate with local weakness zones under the ebro basin the inferred lateral variation in the elastic rigidity is consistent with heat flow measurements in northern spain and with major mesozoic extension in the iberic cordillera and valencia trough

quantitative subsidence analysis and forward modelling of the vienna and danube basins thin skinned versus thick skinned extension abstract we present the results of a quantitative study of the tectonic evolution of the vienna and danube basins by comparing tectonic subsidence histories derived from backstripping of more than 90 wells from slovakia hungary and austria with the predictions from forward tectonic modelling subsidence analysis and forward modelling using a modified non uniform extension model address the tectonic relations between different depocentres and the nature of tectonic subsidence we derived stretching values for the vienna basin between 1 04 and 1 30 for the crustal extension and between 1 00 in the northern part and 1 60 southern part for the lithospheric extension the danube basin is characterized by crustal extension values between 1 09 and 1 30 and lithospheric extension values between 1 00 northern part and 1 60 southern part the vienna basin shows a trend from thin skinned extension in the northwestern part to whole lithospheric extension in the central southern part the subsidence history of the northwestern part of the danube basin also reflects a thin skinned extensional basin formation mechanism the central and southern parts of the danube basin show an important component of lithospheric extension the basin evolution is strongly influenced by the rotating stress field through miocene times expressed in different phases of fault reactivation that are observed in the subsidence history

neogene vertical movements and constraints on extension in the catalan coastal ranges iberian peninsula and the valencia trough western mediterranean abstract the catalan coastal ranges mark the transition from the iberian massif to the active tectonic region of the western mediterranean sea in northeastern spain seismic gravity and thermal data indicate that the crust and lithosphere thin from the ebro basin of the iberian massif to the valencia trough of the western mediterranean consistent with the present elevations of these provinces mid tertiary sediment transport directions however indicate that the catalan coastal ranges were below the elevation of the valencia trough during the mid tertiary and that an inversion of their relative topographies has occurred associated with neogene extension in this region a formulation of lithospheric buoyancy has been used to back calculate possible pre extension lithospheric structures consistent with the mid tertiary elevation constraints and lithospheric strength constraints the back calculation method allows to obtain a range of stretching factors for the crust and for the lithospheric mantle independently from each other these calculations suggest a suite of modes of lithospheric deformation ranging from pure shear of an initially heterogeneous lithosphere to differential stretching of a homogeneous lithosphere both with significant components of thermal modification of the lithosphere not directly associated with convection through extension we conclude that although the basic features of basin formation may be explained by elegant simple models of lithospheric extension the details of elevation changes associated with extension suggest a significant degree of non uniqueness in these models

evidence for reflectors in the lower continental crust before rifting in the valencia trough the past decade has seen a rapid advance in our understanding of the deep structure of the continental crust especially in europe1 3 australia4 and north america5 where seismic profiling has revealed a highly reflective layer in the lower crust on many profiles the reflective layer is associated with regions of extension6 7 suggesting that the reflectors originate by some form of ductile flow or magmatic intrusion during rifting8 9 to test this hypothesis we have examined geophysical and geological data from the valencia trough a rift basin10 12 of late oligocene early miocene age from a comparison of profiles in different parts of the trough and independent constraints on the initial crustal thickness we argue that the reflective layer in this basin was probably already in the crust before rifting and that a mid tertiary extensional event is not required to explain it

pliocene uplift of the eastern iberian margin inferences from quantitative modelling of the valencia trough we present the results of quantitative modelling of subsidence in the valencia trough and associated uplift in the catalan coastal ranges and the balearic islands basement subsidence moho depth and gravity anomalies are calculated for different effective elastic thicknesses eet and durations of rifting along two profiles constrained by recently collected multichannel seismic and gravity data the tectonic evolution of the catalan coastal ranges cannot be explained with traditional two layer lithospheric stretching models for the valencia trough but is consistent with a thermomechanical model invoking lithospheric necking combined with a late stage uplift event the modelling of the topography of the balearic islands suggests an interaction of extension in the valencia trough with extension in the south balearic basin our study supports a rifting model with low values for the flexural rigidity an intermediate level of necking and one finite duration stretching event propagating from the northeast towards the southwestern part of the valencia trough the modelling provides constraints on the magnitude of a large scale pliocene uplift of the eastern margin of the iberian peninsula

tertiary sedimentary history and structure of the valencia trough western mediterranean abstract we present here main results of the common depth point cdp data acquired during the valsis 2 cruise in 1988 in the valencia trough the profiles are tied in with industrial well data and this correlation allows the sedimentary and structural history of the region to be deduced the valsis cruise seismic profiles have been supplemented by a very dense grid of industrial seismic lines and these data permit us to establish an accurate depth to basement map the formation of the initial grabens coeval with those of the gulf of lions is related to the early miocene opening of the northwestern mediterranean basin and the barcelona graben is filled by the same sedimentary layers including evaporites as that of the provencal region nevertheless the valencia catalan grabens have been reactivated by young extensional tectonics which could be a consequence of the convergence of africa relative to europe the valencia trough is segmented by transfer faults which trend nw se these faults which have a more accentuated structural expression than the valencia and catalonia grabens may act as transform faults separating the individual balearic islands the transfer faults are in strike with volcanic ridges which have been sampled during the dsdp leg 13 the dense seismic grid allows us to delineate several widespread volcanic features in the valencia trough which have been active from the early miocene to the pleistocene however we note that the volcanic features are mainly miocene in age whereas the recent volcanism is restricted to a narrow zone columbretes islands the compressional tectonics which deformed the balearic islands does not appear to extend far towards the north we delineate the compressional front north of ibiza but we failed to determine any thrust or fold north of mallorca whereas an extensional tectonics is evident

use of sinkhole and specific capacity distributions to assess vertical gradients in a karst aquifer the carbonate rock aquifer in the great valley west virginia usa was evaluated using a database of 687 sinkholes and 350 specific capacity tests to assess structural lithologic and topographic influences on the groundwater flow system the enhanced permeability of the aquifer is characterized in part by the many sinkholes springs and solutionally enlarged fractures throughout the valley yet vertical components of subsurface flow in this highly heterogeneous aquifer are currently not well understood to address this problem this study examines the apparent relation between geologic features of the aquifer and two spatial indices of enhanced permeability attributed to aquifer karstification 1 the distribution of sinkholes and 2 the occurrence of wells with relatively high specific capacity statistical results indicate that sinkholes funnel and collapse occur primarily along cleavage and bedding planes parallel to subparallel to strike where lateral or downward vertical gradients are highest conversely high specific capacity values are common along prominent joints perpendicular or oblique to strike the similarity of the latter distribution to that of springs suggests these fractures are areas of upward convergent flow these differences between sinkhole and high specific capacity distributions suggest vertical flow components are primarily controlled by the orientation of geologic structure and associated subsurface fracturing

a deep seismic sounding investigation of lithospheric heterogeneity and anisotropy beneath the iberian peninsula abstract the dimensions of the iberian peninsula the facility of firing large charges in the surrounding waters the well known and relatively uniform geology and prior knowledge of the crustal structure resulted in it being chosen as a study area for the investigation of the seismic structure of the lower lithosphere via refraction wide angle reflection seismic profiling the iberian lithosphere heterogeneity and anisotropy experiment iliha with a star shaped arrangement of six long range dss profiles was carried out in october 1989 the models derived from a first interpretation of the recorded data are presented three crustal profiles cover the same western and central part of the hercynian massif as the mantle profiles the resulting interpretations all include a middle as well as a lower crustal layer above the mantle the velocities of the layers in all three models are similar however the layer depths vary beneath the profiles interpretation of the mantle derived data suggests a layered lower lithosphere one reversed line and an intersecting unreversed line indicate the layering penetrates to at least 90 km depth the homogeneity of these layers contrasts strongly with the heterogeneous hercynian surface geology velocities derived from reflected data from the deep layers suggest the constituent materials are either anisotropic or that the layers suffer a slight regional dip

a physical explanation of the relation between flank uplifts and the breakup unconformity at rifted continental margins rift flank uplifts and the breakup or postrift unconformity are characteristic features of many rifted passive or atlantic type continental margins but are not predicted as primary features of simple lithospheric stretching models the explanations that have been proposed for their origin remain controversial either because they call upon special circumstances or because they are difficult to test plane strain finite element models are used in this paper to explore the dynamics of lithospheric necking during rifting and rupture the results agree with the conceptual interpretation that uplift of the rift boundaries to form flank mountains and uplift of the basin responsible for the breakup unconformity are related consequences of regional isostatic compensation of mass that is redistributed during the necking and rupture phases although the amplitudes of these uplifts depend on the model parameter values the relations between and relative signs of these two effects appear to be fundamental the explanation we propose may have been missed in recent studies because there has been a tendency to concentrate on kinematic stretching models which assume local isostatic equilibrium through out the rifting process such an approach is predicated on the assumption that the lithosphere has an insignificant strength or flexural rigidity during extension which is not true if our explanation is correct

implications for karst hydrology from 3d geological modeling using the aquifer base gradient approach we use the gradient of the aquifer base to investigate the hydrology of mature shallow karst systems we first present a 3d geological model of the gempen plateau nw switzerland that reveals the geometry of aquifers and aquitards and their displacement at faults then transfer the 3d geological model to a hydrological model the transformation is based on a conceptual karst model approximating subsurface flow in mature shallow karst systems to open surface flow on the top of the uppermost aquitard or aquifer base the gradient of this surface is expected to mainly influence regional groundwater flow patterns we use the hydrological model to delineate spring catchment areas the discharge areas and corresponding catchment areas of the model are compared with the occurrence of springs in the study area and with hydraulic links confirmed by tracer tests we also describe the way in which the hydrological model contributes to identifying flow processes the proposed aquifer base gradient approach enhances vulnerability assessment in mature shallow karst regions by 1 localizing catchment areas as a precondition of source protection strategies and 2 indicating dominant flow processes associated with individual springs

numerical modeling of simultaneous extension and compression the valencia trough western mediterranean a two dimesional kinematic model which incorporates lateral accommodation of extension and differential stretching is used to investigate the geodynamic evolution of the valencia trough this neogene basin located between the iberian peninsula and the balearic promontory underwent two rifting episodes the first one being coeval with compression model predictions are compared with observations of tectonic subsidence bouguer gravity anomaly surface heat flow and the present day crustal structure the best fitting model assumes three stages in the evolution of the basin during the first stage late oligocene early miocene extension is mainly restricted to the central and northwestern parts of the basin whereas its southeastern margin is locked by the alpine deformation front the material expelled from the axial area is partly accommodated under the balearic promontory producing compression and crustal thickening during the second rifting stage middle miocene extension affects a much broader area including the balearic promontory and the algero provencal basin the third stage late miocene to recent corresponds to a postrift thermal relaxation phase our results put further constraints on the geodynamic evolution of the area

analysis of the geological evolution and vertical movements in the valencia trough area western mediterranean abstract the valencia trough located between the iberian peninsula and the balearic islands corresponds to the south west prolongation of the provencal basin the analysis of recently released seismic lines shows that the present day tectonics of the valencia trough are the result of the coeval development of 1 a system of horsts and grabens in the north west part of the basin during the late oligocene early miocene catalan valencian domain and 2 a thrust and fold system which lasted up to the middle miocene and which was followed by extensional tectonics during the late miocene betic balearic domain in an attempt to characterize the evolution of the valencia trough subsidence curves have been calculated for 18 wells and three regional cross sections distributed across the basin backstripping of these data shows two major stages of tectonic subsidence history 1 a first stage coeval with basin formation 30 15 my characterized by a rapid and strong tectonic subsidence which attains its maximum values in the central basin areas and close to the balearic islands and 2 a second stage 15 0 my in which the tectonic subsidence decreases gradually the amount of crustal thinning estimated from a comparison of the observed and modelled tectonic subsidence ranges between 1 5 iberian margin areas and 4 5 central and south western basin areas these values agree with the crustal thicknesses inferred from seismic refraction data and gravimetric modelling nevertheless such a degree of thinning cannot be explained by the neogene extensional structure the presence of thick mesozoic deposits suggests that the present crustal thinning is partly due to previous mesozoic extension

lithospheric structure of the malawi rift implications for magma poor rifting processes this project was supported by the national science foundation continental dynamics nsf cd grant ear 1255233 and office of international and integrative activities oiia grant iia 1358150 this project is also supported by the nsf earthcube integration grant 1740627 we thank the computational infrastructure for geodynamics geodynamics org which is funded by the national science foundation under award ear 0949446 and ear 1550901 for supporting the development of advanced solver for problems in earth s convection

facies patterns and subsidence history of the jumilla cieza region southeastern spain abstract a detailed analysis of the facies patterns and subsidence history since the late cretaceous 100 ma of the jumilla cieza region in southeastern spain has implications for the debate on the mechanisms causing third order changes in sea level the local subsidence history shows periods characterized by specific trends in tectonic subsidence each with a typical concomitant facies pattern the successive periods are considered to illustrate the transition of the southern iberian plate boundary from a passive margin 108 40 ma through an extensional phase 40 20 ma to a thrust and fold belt 20 ma to recent timing and changes in relative sea level derived from the sedimentary record closely match with the regional tectonic events the order of magnitude of these sea level changes exceed those predicted by the global curve therefore we suggest that in the studied area third order sea level fluctuations are of relatively minor magnitude and only enhance the effect of tectonic induced vertical movements

the effect of rift shoulder erosion on stratal patterns at passive margins implications for sequence stratigraphy abstract numerical modelling indicates that the erosion of uplifted rift flanks at passive margins has a profound effect on offshore stratigraphic patterns flexural uplift due to isostatic rebound in response to erosion extends far into the basin and causes uplift of the shelf as a result the contemporaneously deposited sedimentary wedge displays a characteristic offlap pattern when the rift shoulder is largely eroded onlap promoting mechanisms related to cooling of the lithosphere enable sediments to onlap onto the basin margin the initial offlapping and subsequent onlapping strata form one complete second order depositional sequence comprising a shelf margin transgressive and highstand systems tract the modelling inferences are in broad agreement with stratal patterns and basin geometries observed on the u s east coast the southeastern brazilian and southeastern australian passive margins and the transantarctic mountains ross sea shelf system the initial offlaps caused by erosion of rift shoulders have important implications for the deriviation of eustatic signals from coastal onlap patterns

retro wedge foreland basin evolution along the ecors line eastern pyrenees france the eastern aquitaine basin and north pyrenean zone show many characteristics of retro wedge models however they differ significantly in that slow subsidence and low deformation continued throughout orogenesis so that growth and steady state phases cannot be distinguished we show that the eastern pyrenees record two clear phases of convergence and probably never attained steady state analysis of the aquitaine retro foreland basin along the ariege ecors deep seismic line eastern french pyrenees integrates a new litho and chronostratigraphy subsidence analysis low temperature thermochronology data new interpretations of seismic lines and a balanced cross section within an overall regression two shallowing up cycles latest santonian danian thanetian oligocene record slow tectonic subsidence of the eastern aquitaine basin separated by a quiet period continuing thick skinned shortening was low to moderate the early marine basin generated by loading of the weak extended margin was supplied axially from an unknown eastern edifice while the young pyrenean orogeny to the south remained submerged during the quiet period of ultra slow subsidence no basin migration and negligible sediment supply continental conditions characterized the eastern orogen the second marine transgression was quickly followed by continental conditions the basin was supplied by the now emerging pyrenean orogen and continued to subside until miocene time

far field tilting of laurentia during the ordovician and constraints on the evolution of a slab under an ancient continent during a brief period of 10 to 15 million years in the middle ordovician the michigan basin departed from its bull s eye subsidence pattern and tilted toward the east opening to the appalachian basin this tilting is observed in maps of tectonic subsidence estimated for the black river and trenton formations and extends over 300 km across the michigan basin and into eastern wisconsin contours of constant tectonic subsidence rate are approximately parallel to the inferred position of the laurentian iapetus convergent margin the distance between the inferred position of the subduction zone to the limit of tilting is approximately 1000 km three alternative models for the tilting are tested two relying on the rigidity of the continental lithosphere and a third on the viscous flow generated by a subducted slab in the first elastic model we assume the edge of the elastic plate is simply loaded from above by a fold and thrust sheet volcanic pile etc this model however cannot simultaneously satisfy the space of tectonic subsidence and subsidence rate even for lithospheres which have a rigidity of 10 28 nm in the second elastic model the laurentian continental margin descends into a trench of an eastward dipping slab that is a slab descending under the iapetus ocean this process cannot generate any significant far field displacements even for extremely rigid plates and must be rejected for the third model we use finite element solutions of a negatively buoyant slab in a viscous medium with a faulted lithosphere such slabs can easily generate not only realistic trenches on the under thrusting plate but also significantly tilt the lithosphere as much as 1000 km from the plate margin the magnitude and distribution of far field displacements depend on the age length and dip angle of the slab in contrast to the elastic models penetration of a west dipping slab beneath the continent can reproduce both the extent magnitude and rate of tectonic subsidence observed in the trenton and black river formations the observed data are best fit by an old slab 140 ma which initially descended at a moderate dip 20 30 for 10 15 m y which then steepened as the slab penetrated deeper into the mantle at the position of the previous ordovician plate margin there are narrow block faulted basins which underwent rapid subsidence 10 m y before the michigan basin tilted toward the east we propose that these earlier subsidence events were caused by the initial descent of the slab under the preexisting cambro ordovician passive margin the time lag of 10 m y may be due to the time it takes the slab to penetrate the upper mantle this result is important for understanding the time evolution of mantle convection and mechanisms for the initiation of subduction

subsidence history crustal structure and thermal evolution of the valencia trough a young extensional basin in the western mediterranean the valencia trough is an extensional basin that began rifting during the late oligoceneearly miocene yet it is located within a region of compression between the european and african plates seismic reflection seismic refraction well gravity and geoid data have been used to determine the relative importance of extensional and compressional processes in controlling the structure and evolution of the trough although the trough appears symmetric on bathymetric maps seismic and gravity and geoid data indicate a fundamental asymmetry in its deep crustal and upper mantle structure two dimensional flexural backstripping techniques have been used to estimate the total amount of crustal stretching along a transect of the trough between the catalan coastal ranges and mallorca there is good agreement between the predicted depth to the mono based on a stretching model and the seismically constrained depth beneath the catalan margin but poor agreement beneath mallorca the seismic moho beneath mallorca can be explained by a model in which the crust was modified by the flexural effects of thrust fold loading geoid data suggest that the differences in the crustal structure between the two margins extend into the upper mantle the catalan margin is characterized by a thermal and mechanical boundary which marks the transition between cold unstretched lithosphere and hot thin lithosphere while mallorca is located above a broad region of lithospheric thinning the subsidence history and amount of crustal thinning in the catalan margin resemble that of typical atlantic type nonvolcanic margin however a narrow transition zone 60 km the lack of any evidence for a conjugate margin and the absence of oceanic crust suggest fundamental differences in the way that extensional processes may occur in convergent plate settings

quantitative subsidence uplift analysis of the bajo segura basin eastern betic cordillera spain tectonic control on the stratigraphic architecture the bajo segura basin is located in the eastern betic cordillera at present connected with the mediterranean sea to the east it has a complete stratigraphic record from the tortonian to the quaternary which has been separated into six units bounded by unconformities this paper is concerned with the northern edge of the basin controlled by a major strike slip fault the crevillente fault zone cfz where the most complete stratigraphic successions are found the results obtained summarised below are based on an integrated analysis of the sedimentary evolution and the subsidence uplift movements unit i early tortonian is transgressive on the basin basement and is represented by ramp type platform facies organised in a shallowingupward sequence related to tectonic uplift during the first stages of movement along the cfz unit ii lower late tortonian consists of shallow platform facies at bottom and pelagic basin facies at top forming a deepening upward sequence associated with tectonic subsidence due to sinistral motion along the cfz unit iii middle late tortonian is made up of exotic turbiditic facies related to a stage of uplift and erosion of the southern edge of the basin unit iv upper late tortonian consists of pelagic basin facies at bottom and shallow platform facies at top defining a shallowing upward sequence related to tectonic uplift during continued sinistral movement on the basin bounding fault units v latest tortonian messinian and vi pliocene pleistocene p p consist of shallowing upward sequences deposited during folding and uplift of the northern margin of the basin no definitive evidence of any major eustatic sea level fall associated with the messinian salinity crisis has been recorded in the stratigraphic sections studied q 2001 elsevier science b v all rights reserved

post late paleozoic tectonism in the southern catalan coastal ranges ne spain assessed by apatite fission track analysis abstract we report the first apatite fission track thermochronologic data for 17 samples from the southern catalan coastal ranges of ne spain thermal histories of carboniferous metasediments late hercynian intrusions and lower triassic buntsandstein sediments from three tectonic blocks miramar prades and priorat are derived and interpreted within the geodynamic framework and tectonic evolution of the region the apatite fission track ages range from 198 24 to 38 5 ma and mean fission track lengths are all

crustal structure and the mechanical properties of extended continental lithosphere in the valencia trough western mediterranean seismic refraction and reflection gravity and well data have been used to constrain the structure and evolution of the valencia trough a young extensional basin in the western mediterranean seismic refraction data reveal the present day crustal structure while backstripping of seismic reflection and well data reveal the structure at the time of rifting by comparing the seismically constrained crustal structure to that inferred from backstripping we have been able to evaluate whether the moho is in the expected position given the tectonic subsidence uplift and sediment loading history of the trough the best overall fit between the predicted and seismically constrained crustal structure in the trough is for a model in which the extended continental crust and lithosphere has acquired little or no strength following rifting a low strength is in accord with the observed free air gravity anomaly as well as results from other types of rift basins such as the north sea and the continental margin off the east coast of the usa there are discrepancies between the observed and predicted moho depths beneath the flanks of the valencia trough but they are attributed to either the removal of crustal material during or following rifting iberian peninsula or to orogenic loading of previously extended continental crust mallorca the largest discrepancy up to 10 km correlates with the ebro delta which has prograded into the trough by more than 60 km since the pliocene the discrepancy cannot be explained by the same large scale processes that modified the moho beneath the trough flanks and requires that the lithosphere beneath the ebro delta region is associated with a high 60 t c

flexural uplift of rift flanks due to mechanical unloading of the lithosphere during extension we suggest that the uplift of rift flanks results from mechanical unloading of the lithosphere during extension and consequent isostatic rebound this mechanism is presented as an alternative to explanations for rift flank uplift involving thermal or dynamic processes and magmatic thickening of the crust our hypothesis is based on two critical concepts first the lithosphere retains finite mechanical strength or flexural rigidity during extension second isostatic rebound uplift of the lithosphere follows when the kinematics of extension produces a surface topographic depression that is deeper than the level to which the surface of the extended lithosphere would subside assuming local isostatic compensation we develop and analyze two kinematic models for instantaneous extension of the lithosphere to show that flexural rebound is a viable explanation for the uplift of rift flanks we first investigate the isostatic consequences of finite simple slip on an initially planar dipping normal fault cutting the entire lithosphere when the lithosphere retains flexural rigidity during extension the topography resulting from this model resembles a half graben and the footwall rift flank is flexurally uplifted this simple normal faulting model explains free air gravity anomalies and topography observed at rift flanks in oceanic lithosphere such as broken ridge in the eastern indian ocean the caroline ridges sorol trough in the western equatorial pacific and the coriolis trough behind the new hebrides island arc we then investigate a general kinematic model for lithospheric extension where simple slip on a surface of arbitrary shape is accompanied by pure shear extension in the upper and lower plates when the simple slip component is not zero or the distribution of pure shear in the upper and lower plates is not identical the surface of slip can be regarded as a detachment by simplification our general model accounts for pure shear extension of the lithosphere that is uniform with depth in this case detachments have no meaning in the geologic sense however the kinematics of depth independent pure shear may nevertheless be described in terms of a surface which we term a kinematic reference surface at some depth in the lithosphere we speculate that the depth of this surface may be rheologically controlled the magnitude of rift flank uplift by flexure depends critically on the depth of this reference surface in contrast if local isostasy is assumed when the lithosphere undergoes a given amount of depth independent pure shear the resulting topography will be the same regardless of how the kinematics of that extension are formulated the basin and rift flank topography and free air gravity anomaly over young continental rifts such as the rhine graben can be satisfied using our general extensional model with a small amount 5 km of extension along a listric shaped detachment soling into the crust mantle boundary because the flexural rebound mechanism explains the observed topography and gravity anomaly over both oceanic and continental extensional domains we suggest that rheological differences between the two lithospheric types may not be important in their overall response to extension

crust and upper mantle structure of the central iberian meseta spain summary quarry blasts recorded along three lines on the central iberian meseta are used in an attempt to interpret the crustal structure the results of the interpretation of the data together with published surface wave and earthquake data suggest a layered structure of the crust having the following features the basement in some areas covered by up to 4 km of sediments has a p velocity of 6 1 km s 1 a low velocity layer between 7 and 11 km depth seems to exist on the basis of both p and s interpretation of seismic data a thick middle crust of 12 km has a p velocity of 6 4 km s 1 and overlies a lower crust with a mean p velocity of 6 9 km s 1 and a possible slight negative gradient the mean vp vs ratio for the crust is about 1 75 the moho is reached at about 31 km depth and consists of a transition zone at least 1 5 km thick the p velocity of the upper mantle is close to 8 1 km s 1 and the s velocity about 4 5 km s 1 which gives a vp vs ratio of 1 8 for the uppermost mantle a tentative petrological interpretation of the velocities and composition of the layers is given

first two station rayleigh wave velocity measurements for the northern iberian region abstract up to now dispersion analysis of surface waves across the iberian peninsula and adjacent zones has been based on analog data recorded at the long period iberian stations also the northern region of the peninsula has never been investigated due to the lack of seismological stations with the iliha data set now available it is possible to investigate the northern part of iberia from quality digital records to efficiently remove higher mode interference and to improve isolation of the fundamental mode rayleigh wave from the seismograms time variable filtering is employed once the signal is filtered multiple filtering is then used to compute group velocities at each station the interstation rayleigh wave group velocity can thus be easily calculated frequency domain wiener deconvolution is used to determine the interstation phase velocity we carried out inversion of velocity dispersion data containing both rayleigh wave phase velocities and group velocities according to the generalized inversion theory by means of the stochastic inverse operator the theoretical 2 d earth models determined by joint inversion allow us to obtain for the first time the distribution of the shear wave velocity both laterally and with depth for the northern iberian region and to emphasize the main features of the crust mantle structure of this area

a deep seismic crustal transect from the ne iberian peninsula to the western mediterranean the crustal structure of the transition from the ne iberian peninsula to the western mediterranean is characterized by large scale variations related to its successive compressional and extensional cenozoic tectonics the spanish esci spanish acronym for seismic studies of the iberian crust program recorded 450 km of deep vertical reflection profiles on land and at sea to complete a first crustal transect from the pyrenees to the south balearic basin highly energetic north dipping reflections imaged by combining the etude continentale et oceanique par reflexion et refraction sismique ecors and esci land profiles mark a crustal thickening toward the pyrenees the reflective band becomes horizontal beneath the catalan coastal ranges and the moho is found at 11s no evidence of crustal thinning affecting the iberian mainland is observed the transition to the mediterranean basin is constrained by complementary onshore offshore recordings forward modeling combined with multichannel processing of the wide angle data set shows that a strong thinning of the continental crust by a factor of 2 over a distance of 50 km affects both the catalan and balearic flanks of the valencia trough this thinning affects mainly the deep crust characterized by low velocities of 6 4 6 5 km s suggesting a removal of part of the lower crust during the rifting processes velocities of 7 8 7 9 km s are interpreted in the uppermost mantle with no evidence of underplating the moho appears as a marked discontinuity throughout the transect the nw part of the balearic promontory is characterized by a thick and reflective crust from 12 to 30 km depth an intensely fracturated evaporitic sequence is seen for 100 km along the south balearic basin the seismic images of the continent ocean transition are disturbed by these prominent sediments however the deep reflectivity suggests a crustal thinning moho at 6 7 s to be related to the middle miocene present extensional tectonics

crustal and velocity structure of the valencia trough western mediterranean part i a combined refraction wide angle reflection and near vertical reflection study abstract in november 1988 a 2 ship seismic survey was carried out in the valencia trough western mediterranean to collect normal incidence seismic reflection profile data and six expanding spread profiles along the continental shelf and trough velocity depth solutions derived from the analysis of the esp show a pattern that corresponds with that of continental type crust except in the northeastern part of the basin where oceanic type crust is present along the iberian margin and centre of the trough the seismic data show a well developed neogene and quaternary sequence with velocities ranging from 1 6 to 4 8 km s 1 whereas along the mallorca margin these deposits are absent at the base of the neogene there is a tertiary unconformity which marks the top of the pre rift mesozoic carbonate platform the carbonates which have velocities from 5 4 to 5 9 km s 1 thin towards the axis of the trough along both margins the upper and middle crust is characterised by an almost transparent layer of variable thickness 6 9 km with velocities ranging from 6 1 to 6 4 km s 1 dipping reflections are observed however in the southern part of the trough these reflections are the result of a locally thick mesozoic sequence a 6 km thick highly reflective lower crust with velocities from 6 4 to 7 0 km s 1 is seen beneath the iberian margin along the mallorca margin the lower crust is variably reflective with a velocity of about 6 6 km s 1 in the centre of the trough the total crustal thickness is less than 14 km which thickens asymmetrically towards the flanks reaching values of 20 21 km off shore the iberian peninsula and 23 km in the mallorca margin the seismic moho increases in depth from 13 to 16 km in a ne sw direction relatively low upper mantle velocities from 7 6 to 8 0 km s 1 have been found throughout the basin indicating a slightly anomalous uppermost mantle or a crust mantle transitional layer in the northeast the velocities for the sediments are similar to those described above however the crustal velocity solution can be characterised by three velocity gradient layers ranging from 4 8 6 1 6 1 6 7 to 6 7 7 2 km s 1

karst conduit hydro gradient nonlinear variation feature study case study of zhaidi karst underground river through the analysis of monitoring data with a time interval of 10 min during the rainy season of 2012 for three points of g37 zk8 and zk7 which are located on the main conduit of zhaidi karst underground river system the variation features of water level and hydraulic gradient are studied and the relations are established between gradient and water level or amplitude 1 it is first discovered that there are different function relations such as linear parabola and inverse parabola between the g37 s water level and the hydraulic gradients of different conduit part 2 the peak delay times for water level curves are 50 min and the maximum conducting speed of water press is faster than 13 020 m h 3 the upstream and downstream karst conduits have corresponding enlarging and shrinking amplitude function by the coefficients of 1 899 km and 0 125 km 4 the gradient i variation is still linear to the level difference h made by nine rainstorms the conclusion and the methods of this paper have significance on the study of the regulation and storage capacity and groundwater resources evaluation of karst underground river system

effects of finite rifting times on the development of sedimentary basins abstract most thermo mechanical models for the development of sedimentary basins have assumed that the rifting responsible for the formation of the basin occurred instantaneously and have examined the post rift development of the basin this assumption greatly simplifies the mathematical treatment but is not in accord with what is found in nature where 10 to 50 m y rifting events commonly accompany the formation of sedimentary basins and continental margins the effects of a finite rifting time on the development of sedimentary basins are examined using an analytic technique which allows an arbitrary rifting history in both time and space and which considers the effects of both vertical and horizontal heat transfer this technique allows the thermal structure of the lithosphere to be calculated throughout the rifting event and thus permits the subsidence history and surface heat flow of the developing basin to be traced the effect of a finite duration extension event is that heat is lost during rifting increasing the syn rift subsidence at the expense of the post rift lateral heat flow which was not included in previous studies of the effect of finite rifting times has a significant effect on the subsidence history distribution of sediments and thermal history in particular the post rift subsidence is decreased by more than 25 for a 20 m y rifting event and by more than 10 15 for a rifting event as short as 10 m y this will significantly decrease the subsidence rates in the post rift stage and implies that inferences concerning the structure development and thermal history of the basin derived from using curves to interpret backstripped subsidence can be greatly in error variations in syn rift sediment accumulation and lithospheric thermal structure at the end of rifting resulting from different rifting histories can interact with other factors such as the flexural response of the lithosphere to sediment loading to affect the final width of the basin the total amount of sediments that accumulate and the basin stratigraphy

thermo mechanical modeling of the tyrrhenian sea lithospheric necking and kinematics of rifting we present the results of quantitative forward modeling of the sardinian rifted margin of the tyrrhenian sea the purpose of this study is to investigate the thermo mechanical structure that affects the thinning of the lithosphere across the margin the role of lithospheric necking during basin formation constrained by basement topography moho depth and gravity anomalies is modeled for different compensation models independent constraints are obtained from the analysis of the predicted thermal structure a deep level of necking 25 km is required to explain the observed crustal geometries and gravity anomaly signature the model predicts spatial and temporal variations in rheology during extension with important implications for kinematics of lithospheric thinning prerift lithospheric conditions strain rate and temperature during extension appear to be the key controls on the style of lithospheric rifting and necking in the tyrrhenian sea a forward model for basin stratigraphy is presented for the polyphase history of the tyrrhenian rifting this model provides quantitative estimates of time space dependent crustal thinning and rates of extension

change in tectonic force inferred from basin subsidence implications for the dynamical aspects of back arc rifting in the western mediterranean abstract a method has been developed that allows temporal changes in tectonic force during rift basin formation to be inferred from observed tectonic subsidence curves and has been applied to the gulf of lions the provencal basin and the valencia trough in order to gain some understanding of the dynamical aspects of back arc basin rifting in the western mediterranean sea two distinct tectonic force regimes active at different times during the evolution of each of these back arc basins are identified the first which can be seen in both basins is characterized by tensional forces that gradually abate with time to vanish some 20 my after the onset of rifting the magnitude of tectonic force required to initiate the rifting process is significantly greater in the valencia trough than in the provencal basin subsequently the dynamic development of these back arc basins differs in the provencal basin there is a renewal of force with extensional deformation concentrated in the central part of the rift whereas in the valencia trough the second tectonic force regime is inferred to be one that causes compression that subsequently relaxes such temporal patterns of tectonic force are interpreted to be related to the causative driving processes allowing constraints to be placed on the transient interaction between the overriding and subducting plates in a back arc setting the models also allow inferences to be made about the rheological structure of the lithosphere a significant variation of initial crustal thickness is inferred for the provencal basin but not for the valencia trough in both basins a wet rheology is required in order to initiate rifting given currently accepted bounds on tectonic force magnitudes adoption of a dry rheology leads to insufficiently high strain rates for significant lithosphere extension in both cases

tectonic and climatic controls on the development of foreland fan deltas montserrat and sant llorenc del munt systems middle eocene ebro basin ne spain abstract along an early cenozoic foreland hinterland boundary in northeastern spain we synthesize the depositional environment climatic conditions structural evolution age catchment geometry and altitudinal characteristics from sedimentologic palynologic stratigraphic structural and paleomagnetic data as the transpressional catalan coastal ranges rose during the paleogene two large fan deltas prograded into the ebro foreland basin adjacent to the northeastern part of the range the apices of the fans likely were localized by lateral ramps or tear faults along which rivers from hinterland catchments debouched into the foreland beginning in the late lutetian proximal debris flow sheetflood and distal fluvial deposits maintained the fan surface at or above sea level despite rapid basin subsidence during the succeeding 4 4 my palynological data suggest that a warm humid climate prevailed throughout this interval the mapped extent of the two fans permits an estimation of their volumes whereas the spatial distribution of distinctive lithologies within the ancestral catalan coastal ranges serves to delimit the approximate catchment areas for each of the fans we estimate mean hinterland denudation rates to range from 100 to 180 m my and mean catchment elevation to range from 700 to 1250 m the steep gradients between these catchments and the low lying fan deltas is attributed to the tectonic style of the ancestral catalan coastal ranges which are characterized by an uplifted basement block along a steep frontal thrust accompanied by folding of cover rocks the considerable topographic relief of these catchments is inferred to have combined with co seismic shaking to produce landslides and rockfalls which were reworked as debris and fluid gravity deposits on the fan surfaces

stress induced late stage subsidence anomalies in the pannonian basin abstract subsidence sedimentation and tectonic quiescence of the pannonian basin was interrupted a few million years ago by tectonic reactivation this recent activity has manifested itself in uplift of the western and eastern flanks and continuing subsidence of the central part of the pannonian basin low to medium magnitude earthquakes of the carpathian pannonian region are generated mostly in the upper crust by reverse and wrench fault mechanisms there is no evidence for earthquakes of extensional origin 2 d model calculation of the subsidence history shows that a recent increase in magnitude of horizontal compressional intraplate stress can explain fairly well the observed quaternary uplift and subsidence pattern we propose that this stress increase is caused by the overall europe africa convergence in late pliocene consumption of subductible lithosphere at the eastern margin of the pannonian basin was completed and the lithosphere underlying the pannonian basin became locked in a stable continental frame consequently extensional basin formation has come to an end and compressional inversion of the pannonian basin is in progress

evolution of the central catalan margin of the valencia trough western mediterranean abstract the evolution of the central catalan margin was conditioned by major fault activity and thermal processes generated by crustal thinning the continental margin structure is characterised by major ne sw striking southeast dipping basement faults which have given rise to a graben half graben and horst system these faults acted essentially as normal faults no major neogene strike slip activity has affected the continental margin although minor episodic variations from the dominant extensional regime to strike slip tectonics cannot be discounted two major structural evolutionary stages took place at the margin the transition from one stage to the other being gradual 1 rifting stage late oligocene to early burdigalian related to the opening of the valencia trough and from which originated both the barcelona and valles penedes half grabens 2 thermal subsidence stage late burdigalian to present generated by the subsequent crustal cooling and thinning fault activity during this stage was essentially concentrated in the major half graben bounding faults the sedimentary evolution of the central sector of the catalan margin was controlled by the tectonic and crustal evolution as well as by the successive sea level and paleoclimatic changes which affected the region drastic changes in the depositional systems took place during the transition from the rifting stage into the thermal subsidence stage during aquitanian langhian time characterized by an overall trend of pulsating encroachment of marine conditions over the continental margin a noticeable diversity of depositional systems alluvial lacustrine coastal evaporitic fan delta bay shelf carbonate platform systems developed from the latest serravallian up to the present the depositional framework was less varied due to a general lowering of sea level and to the final onlapping of most of older structural highs which are now buried below the miocene sediments two progradational terrigenous shelf talus systems separated by the messinian erosive surface developed during the latest serravallian tortonian and pliocene quaternary

deep crustal configuration of the valencia trough and its iberian and balearic borders from extensive refraction and wide angle reflection seismic profiling abstract new constraints on the crustal structure of the valencia trough and its iberian and balearic borders have been obtained from a seismic experiment carried out in autumn 1989 a total of 290 sea shots were fired along three refraction wide angle reflection profiles recorded by 10 ocean bottom seismometers obss in the valencia trough and 110 land stations distributed on both flanks the huge amount of recorded data in each profile has been integrated and jointly interpreted to obtain a single 2 d velocity depth model along each line the geometry and deep crustal structure of the basin are fairly well defined in terms of laterally inhomogeneous layered media the sedimentary cover shows a layer of consolidated sediments overlain by neogene and quaternary sediments with a velocity of 5 1 km s interpreted as mesozoic carbonates at the northwestern side of the valencia trough a fairly homogeneous crystalline basement is found on all profiles at a mean depth of 4 km below sea level with a velocity of 6 0 6 1 km s the observed critical distances and arrival times of the moho reflected waves are firm evidence supporting a thinning of the crust towards the centre of the basin the moho rises up to 13 km in the axis of the trough in the nw se and e w profiles and up to 15 km in the ne sw profile moreover the analysis of the well defined pmp phase shows differences between the deep structure of the flanks and the trough respectively a sharp velocity contrast at the moho from a fairly uniform lower crust of 6 4 km s velocity is proposed in both flanks in contrast to a high velocity gradient within the lower crust interpreted near the axis of the trough an anomalous upper mantle velocity of 7 8 km s fits the data throughout the valencia trough and mallorca with slightly higher values of 7 9 km s required towards the continent these velocity values do not favour an interpretation in terms of underplating the geometry of the moho discontinuity shows a gradual deepening towards the iberian peninsula in contrast to a more abrupt slope towards mallorca depth values of 30 32 km typical of a continental crust are inferred about 40 km inland on the iberian peninsula in agreement with the crustal thicknesses already reported for the iberian range and the ebro basin the present crustal thinning resulting from rift episodes in the valencia trough and the iberian border is thus confirmed and constrained from our seismic results of the deep crust and upper mantle

structural controls on sedimentary basin evolution introduction this volume contains a collection of papers on structural controls on sedimentary basin evolution presented at the sixth annual workshop of the international lithosphere program task force origin of sedimentary basins in sitges at the rim of the ebro basin september 1995 previous workshops of the ilp task force had been in rueil malmaison france 1990 in matrahaza hungary 1991 on the rim of the pannonian basin in sundvollen norway 1992 in the oslo graben in benevento italy 1993 in the southern apennines fold andthrust belt and in the dead sea rift of israel 1994 the task force also organized a number of sessions during the 1992 and 1996 european geophysical society and the 1993 and 1995 european union of geosciences conferences reports of these meetings have been published in a number of special volumes and papers cloetingh et al 1993a b 1994 1995a b 1996 stephenson 1993 stephenson et al 1996 a position paper cloetingh sassi and task force team 1994 published in m a r i n e a n d p e t r o l e u m geo logy has outlined the task force strategy to pursue the development of a new generation of basin models using natural laboratories with high quality data sets obtained through close partnership with industry the 7th task force workshop was held on the faroe islands northern atlantic in 1996 with the aim of examining the dynamics of rifting

lithospheric folding in iberia integration of stress indicator data gravity data crustal kinematics data and analysis of topography and recent vertical motions demonstrates the occurrence of consistently oriented spatial patterns of large scale alpine to recent intraplate deformation in iberia the inferred upper crustal and lithospheric deformation patterns and the timing of the associated expressions at or near the surface support the existence of a close coupling with plate boundary processes operating at the margins of iberia patterns of lithosphere and upper crustal folds are oriented perpendicular to the main axis of present day intraplate compression in iberia inferred from structural analysis of stress indicator data and focal mechanism solutions these findings suggest the presence of lithospheric folds with wavelengths compatible with theoretical predictions of folding wavelengths of variscan lithosphere stress induced intraplate deformation set up by plate interactions is compatible with indications for the absence of present day deep mantle lithosphere interactions inferred from seismic tomography

post tectonic landscape evolution in ne iberia using staircase terraces combined effects of uplift and climate river incision into bedrock resulting from the combined effects of tectonic uplift and climate governs long term regional landscape evolution we determined spatial and temporal patterns of post orogenic stream incision from a sequence of well preserved staircase terraces developed over the last 1 ma in the central pyrenees and its southern foreland ebro basin ne spain extensive remnants of ten vertically separated terraces qt1 to qt10 from oldest to youngest were mapped along 170 km of the cinca river valley transverse to the pyrenean mountain belt multiple outcrops appear in the upper reach of the valley ainsa sector 50 km from headwaters as well as in the lower reach albalate sector 125 km from headwaters fluvial incision into bedrock was calculated using i differentially corrected gps measurements of the altitude of straths and ii numerical dating of alluvial sediments from the lower terraces qt5 to qt9 by optically stimulated luminescence previously reported by lewis et al 2009 and supplemented with new dates for the upper terraces qt1 qt2 and qt3 based on paleomagnetism and supported by soil development considering altitude differences and the elapsed time between successive well preserved terrace couples qt3 qt7 qt7 qt9 and qt9 active channel mean bedrock incision rates ranged from 0 76 to 0 38 m ka 1 at the upper reach of the valley ainsa section and from 0 61 to 0 20 m ka 1 at the lower reach albalate section river incision along the valley produced vertically separated near parallel longitudinal terrace profiles evidencing a rapid near uniform regional uplift as response to i the tectonic lithospheric thickening in ne iberia and ii the erosional download rebound related to the ebro basin exorheism moreover a subtle upstream divergence of strath profiles may have been a consequence of an increase in uplift rate toward the head of the valley additionally incision rates changed over time as indicate results from the lower reach albalate section the maximum rate was 1 48 m ka 1 between qt7 61 ka and qt8 47 ka and the minimum rate was 0 11 m ka 1 between qt3 401 ka and qt5 178 ka the highest incision rates were produced after the marine isotope stage 4 most likely in response to i an increased snowmelt discharge during the subsequent deglaciation related to the last maximum advance of glaciers in the southern pyrenees and ii a limited width of the valley after qt7 formation resulting from the deactivation of the westward river migration therefore incision rates over the last 1 ma in the cinca river valley were basically controlled by near uniform bedrock uplift in the context of climate variability the results reported in this study represent significant data on fluvial incision in ne iberia and provide an assessment of the regional post tectonic landscape evolution

evaluation of a hydrodynamic threshold in the zhaidi karst aquifer guangxi province china understanding how the discharge rate and the hydraulic gradient of a karst aquifer varies in response to rainfall events is important for the efficient management of water resources in these aquifers the relationship between discharge and hydraulic gradient is related to aquifer properties such as the physical characteristics of the karstic matrix hydraulic conductivity and the extent to which water is exchanged between conduits and the matrix in this study discharge and hydraulic gradient data were monitored at 4 h intervals for 476 continuous days in the zhaidi karst aquifer located in guilin guangxi province china these data showed that the relationship between flow rate and hydraulic gradient in the aquifer became increasing non linear with increasing flow rates after analyzing the time series data a hydrodynamic threshold between quickflow and baseflow conditions was found to take place at a discharge rate of 0 80 m3 s the linear law and nonlinear equations were obtained between discharge and hydraulic gradient which reflected the flow mechanism of groundwater flow in this karst aquifer

the valencia trough western mediterranean an overview abstract the valencia trough located between the spanish mainland and the balearic islands corresponds to a late oligocene to recent sedimentary basin that is characterized by a highly attenuated continental crust its northwestern part evolved in response to a late oligocene to early miocene rifting phase that was followed by a period of post rift subsidence and a late miocene pleistocene phase of renewed crustal extension and magmatism its southeastern part is characterized by late oligocene to mid miocene compressional deformation and subsequent extension in the axial parts of the basin the crust has been thinned by a factor of 3 whereby the lower crust is either absent or very thin upper crustal extension appears to be considerably smaller than indicated by the crustal configuration of the basin a major problem in understanding the evolution of the valencia trough is the lack of knowledge about the physical state and structure of the lithosphere before late oligocene extension evolution of the northwestern part of the basin appears to be linked with the development of the oceanic provencal basin middle miocene compressional deformation of the balearic fold belt forming the southeastern margin of the valencia trough appears to have interfered with the tensional evolution of the latter which only resumed after crustal shortening in the balearic domain had given way to extensional tectonics during the late miocene

mechanical de coupling of the lithosphere in the valencia trough nw mediterranean what does it mean we study the mechanics of lithospheric decoupling in continental extensional basins in relation to the distribution of non competent mechanical layers within the lithosphere and the position of the isostatic compensation level we specifically address the different modes of deformation taking place in crustal levels according to a self consistent formulation of the concept of mechanical decoupling subsequently we investigate the style of lithospheric decoupling in the valencia trough nw mediterranean a prime example of a young continental rift basin during its evolution the lower crust or at least part of it acted as a weak non competent layer that eventually flowed laterally to accommodate deformation in the subcrustal lithosphere and overlying crust which became mechanically decoupled we use a numerical model to discern whether these two layers deformed fully independently vertical decoupling or maintaining a mechanical link horizontal and partial decoupling results of our study constrained by a high quality database exclude fully decoupled mode and favor isostatic compensation level in the asthenosphere interpretation of our results in light of geological and geophysical data suggests that the present valencia trough is best described by partial lithospheric decoupling 6 2003 elsevier science b v all rights reserved

geochemistry and petrology of palaeocene coals from spitzbergen part 2 maturity variations and implications for local and regional burial models the central tertiary basin is an uplifted part of the north barents shelf and should be an ideal location to understand the thermal history maximum burial depth and overburden thickness in this petroleum rich area efforts to quantify the thermal history of the region have been hampered by reports of hyper thermal conditions maturity gaps and maturity inversions in the tertiary vitrinite reflectance ro record this has been attributed to thermal insulation effects vitrinite reflectance due to bitumen impregnation and later tertiary volcanism through the use of ro organic maturity parameters 13c nmr and rock eval pyrolysis this study aims to explain the unusual maturity effects observed and the implications for burial models within single seams ro ranges from 0 5 to 0 78 with increasingly bimodal distribution up seam analysis of coal aromaticity and the results of rock eval analysis confirm that maturity gaps and inversions only occur where the vitrinite reflectance has been suppressed by high bitumen content 300 400 mg g coal samples with the lowest hydrogen index values 250 mg hc toc provide the most accurate estimates of the vitrinite reflectance results indicate maximum burial temperatures of 120 c in the basin centre and 100 c at the basin margins with a hyper thermal gradient of approximately 50 c km this gradient implies a total overburden of 2 km of which 1 km has been lost maximum burial depth and total erosional sediment load to the barents shelf are therefore at the lower end of current estimates

palaeo elevation and effective elastic thickness evolution at mountain ranges inferences from flexural modelling in the eastern pyrenees and ebro basin abstract the results are presented of a two dimensional flexural modelling study of the lithosphere underlying the southern pyrenees and the ebro basin the modelling is based on a crustal scale balanced cross section along a profile through the north eastern part of the iberian plate two time slices of the structural evolutions of the mountain chain are modelled the present day configuration and the configuration at middle lutetian time 47 ma where important structural and sedimentological changes are observed the flexure model incorporates lateral variations in the effective elastic thickness eet of the lithosphere the present day deflection in the profile is simulated using boundary forces and a northward decreasing eet that varies from 30 to 11 km models for middle lutetian times indicate eet values of 26 18 km in the northern part of the profile assuming that the eet at the distal margin of the ebro basin has not significantly changed since middle lutetian times these higher values for the eet at middle lutetian times suggest that the effect of the cretaceous extensional phase on the present day flexural rigidity is small and therfore the inferred northward decreasing rigidity is predominantly related to the pyrenean collision flexural modelling provides also constraints for the palaeo elevation of the inner part of the chain including the assumption that the eet at the distal margin of the ebro basin has not significantly changed since middle lutetian times the model predicts a maximum palaeo elevation of 2000 m which is in agreement with geological observations concerning the relation between basin fill and palaeo elevation