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

tropical zonal momentum balance in the ncep reanalyses the seasonal cycle of the zonal mean zonal momentum balance in the tropics is investigated using ncep reanalysis data it is found that the climatological stationary waves in the tropical upper troposphere which are dominated by the equatorial rossby wave response to tropical heating produce an equatorward eddy flux of westerly momentum in the equatorial belt the resulting westerly acceleration in the tropical upper troposphere is balanced by the advection of easterly momentum associated with the cross equatorial mean meridional circulation the eddy momentum fluxes and the cross equatorial flow both tend to be strongest during the monsoon seasons when the maximum diabatic heating is off the equator and weakest during april may the season of strongest equatorial symmetry of the heating the upper level rossby wave pattern exhibits a surprising degree of equatorial symmetry and follows a similar seasonal progression solutions of the nonlinear shallow water wave equation also show a predominantly equatorially symmetric response to a heat source centered off the equator

a comparison of semi lagrangian and eulerian polar climate simulations abstract at the modest vertical resolutions typical of climate models simulations produced by models based on semi lagrangian approximations tend to develop a colder tropical tropopause than matching simulations from models with eulerian approximations all other components of the model being the same the authors examine the source of this relative cold bias in the context of the ncar ccm3 and show that it is primarily due to insufficient vertical resolution in the standard 18 level model which has 3 km spacing near the tropopause the difference is first diagnosed with the held and suarez idealized forcing to eliminate the complex radiative convective feedback that affects the tropopause formation in the complete model in the held and suarez case the tropical simulations converge as the vertical grid layers are halved to produce 36 layers and halved again to produce 72 layers the semi lagrangian approximations require extra resolution above the original 18 to capture the converged tropical tropopau

stratigraphic and kinematic modeling of thrust evolution northern apennines italy we present a quantitative kinematic model of thrust evolution that allows detailed interpretation of the stratigraphic record of foreland basins simulation of thrusting and syntectonic sedimentation shows that changes in the relative rate of thrusting and mode of thrust activation can be determined by their expression in basin stratigraphy truncations and offlaps reflect thrust activity and hinterland migration of basin depocenters indicates out of sequence thrusting forward modeling of the stratigraphic record of the pliocene quaternary po basin italy enables the quantitative reconstruction of the displacement sequence of the thrust sheets prograding into the basin during the pliocene deep seated middle pliocene thrusting accompanied by out of sequence thrusting provides a consistent explanation for the observed stratigraphic record of the po piggyback basins

stationary eddy response to surface boundary forcing idealized gcm experiments abstract a set of atmospheric general circulation model agcm experiments under idealized conditions is performed to investigate atmospheric response to surface boundary forcing by extratropical land sea contrast large scale orography and tropical sea surface temperature sst distribution stationary eddies forced by the extratropical land sea distribution are strongest in high latitudes but their amplitudes are modest and comparable to internal chaotic variability by contrast the stationary eddy response to zonal variations in tropical sst is strong and robust in both the subtropics and midlatitudes while these sst forced stationary waves are trapped within the troposphere those induced by orography show a strong vertical propagation into the stratosphere analysis of transient eddies indicates that orography is effective in generating a zonally localized storm track while extratropical land sea contrast has little effect on the zonal variation of upper level storm activity a vorticity budget a

on the seasonality of the hadley cell abstract the annual march of the climatological mean meridional circulations mmcs in the ncep ncar reanalyses is dominated by two components of roughly comparable mean squared amplitude 1 a seasonally invariant pair of hadley cells with rising motion centered near and just to the north of the equator and subsidence in the subtropics and 2 a seasonally reversing sinusoidally varying solsticial cell with ascent in the outer tropics of the summer hemisphere and subsidence in the outer tropics of the winter hemisphere the meridional structure and seasonal evolution of the solsticial cell are suggestive of a close association with the monsoons these results are consistent with previous analyses of the mean meridional circulation based on radiosonde data

evolution and depocentre migration in thrust top basins inferences from the messinian velona basin northern apennines italy abstract a structural study of the thrust related messinian velona basin is presented this basin developed in the hinterland area of the northern apennines between two n trending and e verging thrust anticlines the montalcino castelnuovo dell abate anticline to the west and the ripa d orcia anticline to the east the architecture of the basin and the deformation affecting the syntectonic sedimentary deposits show that the velona basin was affected by two strong compressive phases during the messinian the results of this study fit well into the structural evolution of the nearby hinterland basins indicating a neogene tectonic scenario dominated by compression the evolution of the velona basin is compared with simple models of thrust top basins whose development is controlled by the kinematics of two competing thrust anticlines the westward directed depocentre migration recognized in the velona basin is related to a higher displacement rate along the eastern thrust fault ripa d orcia thrust anticline whereas the deformations at the opposite basin margin are related to the montalcino castelnuovo dell abate thrust anticline the general models of thrust top basin evolution presented here were successfully applied to the velona basin case and may be compared with other natural examples as well

eustatic sea level changes interpreted from seismic stratigraphy a critique of the methodology with particular reference to the north sea jurassic record seismic stratigraphic methods for interpreting eustatic sea level change are based on generalized stratigraphic models and chronostratigraphic interpretations that have not been substantiated by publication of the necessary basic supportive data chronostratigraphic correlations of sea level change curves between basins are based partly on circular reasoning onlap and offlap seismic models may not indicate sea level change but flexural subsidence facies shifts or changes in sea level in the opposite direction to that proposed resolution of some of these problems may be achieved by publication of basic data now in confidential industry files the widely acclaimed vail curves should not be used as templates for basin correlation until such data have been provided and such use should be supported by appropriate conventional lithostratigraphic and biostratigraphic documentation from each new basin where such data have been made available as with the north sea jurassic serious questions of interpretation are raised

passive roof thrusting and forelandward fold propagation in scaled brittle ductile physical models of thrust wedges a set of scaled analogue models was performed to investigate the role of a decollement layer in the structural style of fold and thrust belts silicone putty sgm 36 has been employed to represent the ductile decollement while frictional material quartz sand has been used to simulate the brittle behavior of roof and floor sequences situated above and below the decollement respectively in order to explore a wide combination of strength profiles models have been deformed under five distinct rates of compression 0 15 0 3 0 45 0 6 and 1 5 cm h 1 employing four different thicknesses for the silicone layer 0 1 0 2 0 4 and 0 8 cm experimental results indicate that roof sequences exhibit two distinct styles of deformation 1 passive roof duplex prd geometry e g banks and warburton 1986 and 2 outward propagation of folding ofp along the decollement e g davis and engelder 1985 in prd geometry the roof sequence remains relatively stationary being underthrust by a wedge shaped floor duplex while in ofp displacement along the floor thrusts is transferred horizontally along the decollement layer experiments suggest the occurrence of a genetic relationship between shear stresses at the base of the roof sequence b and within the ductile layer d and the development of prd or ofp geometry for a given strain rate the deformation pattern of roof sequences depends upon the b d ratio as well as the absolute b and d values the transition field between ofp and prd styles has been approximated by curvilinear regression of transition style experimental data points with a minimum value of d varying between about 112 and 160 pa to enter the prd field syntectonic sedimentation in the molasse basin is found to inhibit development of folding into the foreland but to promote prd style experiments simulate many of the principal characteristics of fold and thrust belts developed above a basal evaporite decollement as well as the development of passive roof duplexes at mountain fronts shear stress values inferred for many fold and thrust belts correlate well the deformation fields predicted by the present experimental study allowing to propose a simple model describing the mechanical behavior of natural roof sequences underlain by a decollement layer

spontaneous transition to superrotation in warm climates simulated by cam3 1 recent paleoclimate proxy reconstructions show that tropical surface temperatures may have been as high as 35 40 c in the early cenozoic here we study the tropical atmospheric circulation s response to temperatures in this range using a full complexity atmospheric general circulation model agcm we find that when equatorial surface temperatures exceed 33 c the model undergoes a transition to equatorial superrotation a state with strong annual and zonal mean westerlies on the equator the transition is driven by zonal momentum convergence due to large amplitude transient eddies on the equator these eddies have a structure similar to the observed madden julian oscillation mjo the model s mjo variability is weaker than observed when simulating the modern climate but increases sharply with temperature coming to dominate the tropical variability and mean state of the warmest climates

intraplate deformation and basin formation during the tertiary within the northern iberian plate origin and evolution of the almazan basin the tertiary almazan basin was a topographic high during the mesozoic rifting at the northern part of the iberian plate it was bordered by two mesozoic basins 1 the castilian basin with a maximum thickness of more than 2000 m to the south and 2 the cameros basin with a maximum thickness of 9000 m to the north to the east the almazan basin is bordered by paleozoic rocks of the nw se trending aragonian range which underwent little subsidence during the mesozoic the two mesozoic basins show an e w direction during the tertiary nne ssw compression mainly late eocene early miocene both mesozoic basins were inverted and uplifted and the almazan basin with an overall synclinal geometry was filled with syn tectonic terrestrial sediments reaching a maximum thickness of 3500 m deformation during the tertiary was strongly controlled by preexisting structures both mesozoic extensional faults and reactivated variscan folds the depocenter of the tertiary basin migrated southward during the paleogene this migration is consistent with a piggyback transport of the whole basin northward due to the movement on the underlying crustal scale north verging cameros thrust the geometry and sedimentary evolution of the almazan thick skinned piggyback basin was controlled by the uplift associated with the main crustal scale thrust which was the main source area and was separated from the foreland basin since the early stages of filling late eocene this makes the main difference with thin skinned piggyback basins controlled by the foreland thrust belt and separated from the foreland basin only at their late stages

the dependence of the low level equatorial easterly jet on hadley and walker circulations abstract how the time mean hadley and walker circulations affect the formation of a low level equatorial easterly jet is investigated experiments are conducted for equinoctial conditions using a general circulation model the community climate model ccm1 that includes a kuo convective scheme and a lower boundary that is specified to be water at a fixed sea surface temperature sst several zonally symmetric sst forcings are used to determine how various hadley circulations affect the tropical zonal wind field a zonal wavenumber one equatorial sst anomaly superimposed on a zonally symmetric sst distribution forces a wind field that includes both hadley and walker circulations the hadley circulation experiments produce equatorial easterlies and low level jets on the poleward sides of the intertropical convergence zone itcz 10 to 15 from the equator in an experiment with a single dominant off equatorial itcz in the northern hemisphere the southern hemisphere jet moves to within 7 5 of the equa

the role of the divergent circulation for large scale eddy momentum transport in the tropics part i observations abstractthis work investigates the role played by the divergent circulation for meridional eddy momentum transport in the tropical atmosphere it is shown that the eddy momentum flux in the deep tr

book reviewthe techniques of modern structural geology vol 1 strain analysis j g ramsay and m i huber academic press london 1983 xiii 307 pp us 55 00 28 00 hardcover

compaction induced stress variations with depth in an active anticline northern apennines italy 1 it is shown that the stress field can vary with depth even within a homogeneous tectonic setting as documented for the active mirandola fault related fold along the buried front of the northern apennines analyses of borehole breakouts and other well data integrated with seismological information and field evidence show that extension perpendicular to the fold axis above approximately 1200 m changes to a strike slip stress field and finally to compression near the main detachment at depth similar along depth strain variations recognized in non active anticlines are usually explained by invoking tangential longitudinal strain folding i e stretching above and shortening below a neutral surface or gravitational instabilities however in this study we propose that differential compaction may play a significant and generally overlooked role with the aid of numerical modeling it is shown that where fold limbs are onlapped by highly compactable deposits as in the mirandola area differential compaction induces stretching at shallow 1 2 km depths the amount of stretching is a function of the shape of the fold and of the thickness of the syn tectonic sediments we conclude that in the mirandola case study the stress variations observed with depth are the result of a combination of a regional compression at depth and local tension driven by differential compaction of growth strata on the limbs of the anticline with respect to its crest

apennines subduction related subsidence of venice italy 1 the foreland regional monocline related to the northern apennines subduction can be followed from the po basin to the friuli region italy at least 240 km north eastward in seismic reflection profiles of the po basin and of the northern adriatic sea the dip of the regional monocline gradually decreases from about 22 to close to 0 pleistocene sediments onlap and pinchout to the northeast venice is located on a segment of the active monocline dipping about 1 8 to the southwest in sediments around the venice area the 1 43 ma limit is in the 960 1500 m depth range indicating a long term subsidence rate of about 0 7 1 0 mm yr therefore a significant part of the natural component of the town subsidence is related to the north eastward retreat of the adriatic subduction the subduction related downflexure affects the whole of the po plain basin and part of the southern alps where it opposes to the general uplift related to orogenesis

three dimensional architecture of growth strata associated to fault bend fault propagation and decollement anticlines in non erosional environments abstract the evolution of surficial structures at the toes of orogens arises from the complex interplay between tectonic and surface processes the internal architecture of syntectonic sediments has been shown to provide useful insights on the kinematic mechanism of folding two dimensional templates of growth strata patterns associated to thrust related anticlines are available in the literature in this paper we show the results of three dimensional numerical modelling of growth fault bend folds fault propagation folds fixed limb length decollement folds and fixed limb dip decollement folds we point out that total thickness contour maps single syntectonic layer contour maps and above all the computation of their directional first derivative maps provide useful templates for inferring the kinematic mechanism of folding when compared with similar maps from natural examples application of these three dimensional numerical models includes the comparison and supervised best fit with three dimensional seismic reflection data sets numerical results are contrasted with the growth strata map patterns of the mediano oliana and pico del aguila anticlines in the spanish pyrenees

structural setting of the adriatic basin and the main related petroleum exploration plays abstract most of the oil and gas resources located within the adriatic domain are genetically linked to the flexure of the adria continental margin and to the evolution of the apennines fold and thrust belt the source rocks contained in the pre flexure epi continental successions reached the maturity window during the flexural subsidence or alternatively the flexural accommodating siliciclastic flysch themselves generated and stored hydrocarbons the petroleum exploration plays of the adriatic domain are tentatively classified in this paper according to their geological evolution with respect to the apennines fold and thrust belt the description of the geological evolution of these structures and related petroleum plays are described including plays set in undeformed or poorly deformed foreland areas a new isochrones map showing the structural setting of the substratum at the level of the fucoidi fm is presented several different groups of structures can be recognized in the adriatic domain that can be connected to the final phases of deformation of the apennines or to the interaction with the dinarides fold and thrust belt front to the east

simulation of foreland basin stratigraphy using a diffusion model of mountain belt uplift and erosion an example from the central alps switzerland foreland basin stratigraphy can be considered as the result of three interacting processes thrust deformation which builds the tectonic load sedimentary and erosional processes which redistribute that load and the flexural response of the lithosphere the resultant stratigraphy of foreland basins is commonly composed of a small number of shallowing and coarsening upward cycles bounded by regional unconformities to understand the development of these unconformities we present a simple model of these three processes coupling an evolving thrust wedge on a linear elastic plate with erosion and sedimentation defined by the diffusion equation applied to topography our model demonstrates the development of regional unconformities without recourse to either eustasy or complex viscoelastic models for the continental lithosphere the model describes the thrust wedge foreland basin system in terms of four parameters 1 the effective elastic thickness of the foreland plate te 2 the sediment transport coefficient k 3 the thrust wedge advance rate 4 the surface slope of the thrust wedge the model is applied to the oligocene miocene north alpine foreland basin nafb of eastern switzerland the stratigraphy of the nafb can be simplified into two large scale shallowing upward cycles separated by an unconformity at the base of the burdigalian 22 ma geological information is taken from the nafb to estimate suitable values for the parameters listed above assuming a linear elastic lithospheric rheology the te value is estimated at 10 5 km from decompacted sediment columns data to constrain the sequential development of the thrust wedge come from structural geology the early stages 40 24 ma of compression involved a relatively low angle thrust wedge with an advance rate of approximately 2 4 mm yr at about 24 ma the wedge advance slowed down and thickened by underplating crystalline basement of the foreland plate the value for the transport coefficient has been estimated from previous studies prior to attempting to simulate the broad scale geometry of the nafb the role of each parameter was assessed individually the values for te and k are held constant throughout the simulation of the nafb at 7 5 km and 500 m yr respectively the geometry of the base burdigalian unconformity is reproduced by variations in the parameters describing the thrust wedge the surface slope angle of the wedge is increased from 2 5 to 4 over 0 2 m y and the rate of thrust advance is decreased from 2 mm yr to 0 2 mm yr during the thickening event between 24 and 23 8 ma the rejuvenation of the internal parts of the thrust load causes backtilting of the foreland basin sediments and after a time lag erosion of the distal stratigraphy over the forebulge so simulating the base burdigalian unconformity

growth stratal architectures associated to decollement folds and fault propagation folds inferences on fold kinematics abstract in many thrust and fold belts asymmetric folds with overturned or steeply dipping forelimbs and gently dipping backlimbs are commonly interpreted as thrust related folds determining the folding mechanism exclusively from the final fold geometry in the pre growth units is possible only for a limited suite of structures the nature of fold thrust interaction in shallow structures can be inferred by coupling the fold geometric analysis with the study of the syntectonic sediment stratal architectures several factors such as axial surface activity fold uplift limb rotation and limb widening rates together with sedimentation and erosion rates control growth strata patterns because the evolutionary path of most of these parameters depends on the folding kinematics different growth stratal architectures are expected for different thrust related anticlines in this paper we examine the influence of the above factors on growth stratal geometries associated to a simple kink band and then we apply the same approach to kinematic models of decollement folding and fault propagation folding four geometric approaches are used to account for the geometry and kinematics of anticlines located at the tip of a blind thrust fault propagation folding with no excess layer parallel shear fault propagation folding with progressive layer parallel shear constant limb length decollement folding and variable limb length decollement folding whereas fault propagation folding with no excess layer parallel shear is a self similar folding mechanism the other three types involve limb rotation coherent geometries between growth and pre growth sequences develop at high sedimentation rates in the crest of fault propagation folds and incoherent ones in decollement folds minor differences within growth strata patterns occur at low sedimentation rates and when erosion affects the crest of the anticlines

stationary rossby wave propagation through easterly layers abstract the linearized shallow water equations on a sphere are solved numerically to examine the sensitivity of the steady response to midlatitude mountain forcing to the zonal mean basic state the zonal mean basic state consists of meridionally varying zonal winds y and meridional winds v y cases are considered where is westerly everywhere outside a tropical region where it is easterly a zonal wavenumber three mountain confined to the northern hemisphere midlatitudes where 0 provides the forcing when v 0 the usual result of negligible southern hemisphere response to the mountain forcing is found however a modest mean meridional velocity 0 3 m s 1 that is directed from north to south through the easterly layer leads to significant southern hemisphere response an argument based on the local dispersion relation is offered to explain this effect it is concluded that critical latitude effects on wave propagation are sensitive to the structure of the mean meridional circulation in the

introduction to special issue on integrated basin studies ibs a european commission dgxii project this issue contains papers issued from the integrated basin studies project ibs which is part of a larger program of the european commission dgxii entitled geosciences ii the ibs project ec contract jou2 ct92 0110 originated in geosciences consultation meetings the first of them being held in strasbourg in june 1989 under the auspices of mr hubert curien former french minister for research and technology and the subsequent meeting being held in brussels these consultation meetings have resulted in the conclusion that a main axis of future research in geosciences should be the study of sedimentary basins upstream of industrial activities mainly the oil and gas industry but also water resources management the mining industry the storage of undesirable products and coastal engineering they also resulted in the conclusion that future research on sedimentary basins should fulfill two requirements integration of disciplines and modelling such a conclusion may now seem trivial but was not so generally accepted at that time in this spirit the ibs project was designed to provide the oil and gas industry with a new generation of models for basin formation basin evolution and basin fill architecture from basin scale to reservoir scale its main objectives are the linkage of crust thermomechanical behaviour to basin formation and deformation mechanics and the corresponding modelling the quantification of tectonic control on the sedimentary record and the analysis of compaction and mass and heat transfer the ibs strategy is to link subsurface data to field data and an important part of the project is devoted to thematic field studies in european sedimentary basins of different tectonic styles taken as natural laboratories basin research has gone through a rapid evolution during the last decade in particular through the development of new acquisition and processing methods for seismic data and advances in drilling technology modelling provides an important tool to analyse different aspects of basin formation processes and find their tectonic expression in the basin fill the need for 3 d modelling techniques and models capable of linking processes operating on basinwide to subbasin scales is increasingly recognized and a significant effort has been made in the ibs project to develop a new generation of basin formation models coping with these needs see also cloetingh et al 1993a van wees and cloetingh 1994 as many data required to test these models reside in industrial companies ibs has promoted a closer link between academic research and basin studies carried out by industry the participation of the petroleum industry has been vital in this project and ibs has been able to establish a well functioning system of cooperation that not only facilitated data access but most important guaranteed the suitability of the end products of the project this has led to an intensive exchange of modelling concepts and data sets between industry and academia the ibs project has also used extensively the international lithosphere program task force origin of sedimentary basins see cloetingh sassi and task force team 1994 cloetingh et al 1993a b 1994 to implement planning and to discuss preliminary results it also builds partly on joint research through the european commission tempus and peco programs on pannonian basin studies horvath 1993 van balen and cloetingh 1995 van balen et al 1995 horvath and cloetingh 1995 a stimulating aspect of the activity of the ibs group is the creation of a research network in the corresponding field of knowledge which comprises now 30 teams belonging to eight european countries england france germany hungary norway spain switzerland and the netherlands this demonstrates the capacity of the procedures used by the dgxii of the european community to formulate a really european research space phd students and young researchers form an important component of the research groups

equatorial superrotation and maintenance of the general circulation in two level models abstract suarez and duffy have noted an interesting bifurcation in a two level gridpoint general circulation model when strong tropical heating is imposed this bifurcation results in a model climatology with strong upper level westerlies in the tropics in this paper it is argued that this bifurcation is essentially due to the dominant role played by extratropical baroclinic transients in the tropical angular momentum budget a series of numerical experiments is analyzed with a global two level primitive equation model using spectral truncation in the horizontal the model climatologies in these experiments fall into two categories 1 conventional that is weak upper level easterlies westerlies in the tropics and 2 superrotating that is strong upper level westerlies in the tropics an attempt is made to explain the maintenance of the general circulation in these two radically different climatologies by studying the properties of unstable normal modes for the two different time mean states the sp

the neogene evolution of the outer carpathian flysch units poland ukraine and romania kinematics of a foreland fold and thrust belt system abstract various techniques of geometric and kinematic analyses including cross section balancing and forward modeling have been applied successfully to the outer carpathian flysch units along regional geologic profiles crossing the belt from its undeformed foreland to the pieniny klippen belt western carpathians poland or to the central east carpathian allochthon eastern carpathians ukraine and romania the amounts of neogene shortening as well as the mode and the location of basement consumption are discussed on the basis of balanced cross sections compiled along the three most representative regional traverses in addition the complete kinematic evolution of complex carpathian structures such as the fore dukla triangle zone southeastern poland the borislav pokut duplexes ukraine and the marginal folds romania are described in more detail by using a forward modeling approach major results concern the tectonic heritage of laramian inverted structures mesozoic normal faults reactivated as reverse faults during the late cretaceous paleocene compression or transpression in the development of the neogene outer carpathian edifice pre eocene deformation and erosion effectively induce discontinuities in the mid cretaceous blackshale detachment horizon and help to localize the neogene deformations in complex triangle zones the thrust sequence itself evolves alternatively in a piggyback or in an out of sequence mode clearly the critical taper of the outer carpathians is preserved by a constant balance between erosion and thrust reactivations in the inner part of the wedge and sedimentation and tectonic accretion at its front

neotectonics of the subandes brazilian craton boundary using geomorphological data the maranon and beni basins abstract active and abandoned fluvial traces are used together with neotectonic seismotectonic and subsurface structural data to study the neotectonic evolution of the peruvian and bolivian foreland basins the maranon basin to the north and the beni basin to the south are located near the ends of the peru bolivia andean segment this segment lies above the flat slab subduction of the nazca plate beneath the andes the surface of these basins shows a complex network of present day rivers and fossil river traces a relative chronology of the river traces deduced from morphological criteria allows the identification of successive shifting of fluvial belts up to the present position of the main rivers as it enters the ucamara depression the ucayali river is deflected to the northeast successive shifts of the deflection point are directed upstream along the upper reaches of the river along the foothills simultaneously the maranon river is deflected to the north lining up with the straight ne trending lower reaches of the huallaga river in the central part of the depression the rivers trend northeast southwest parallel to the main strike of the basement faults this regional trend is also parallel to 1 the greatest principal stress observed both to the east and the west of the depression and to 2 the neotectonic faults on the margin of the brazilian craton the beni basin is characterized by a counterclockwise shift of the beni river successive shifts of the river involve the northward migration of the deflection point of the beni river as it enters the basin a fault connected to the foothill margin controls this downstream movement recent erosion of the flood plain surface to the east suggests a tendency of the craton margin to ascend no coaxial stress resulting from either plate motion or from collapse of the andean topography seems to control the directional shift of rivers in the basins

syn tectonic sedimentation associated with three dimensional fault bend fold structures a numerical approach abstract syn tectonic sediments growth strata in compressional structures are three dimensional 3d features whose geometry reflects both the style of deformation and the distribution of accommodation space in the system previously numerical modelling of growth strata in compressional settings has generally been done in two dimensions in the plane of the transport direction in contrast in this paper we examine growth strata associated with a 3d fault bend fold that exhibits variations in slip along strike a forward numerical modelling approach is used to investigate the 3d geometry of syn tectonic sediments under a variety of conditions we consider a fault bend fold in which slip decreases linearly from the centre of the structure to zero displacement at the edges in a direction perpendicular to transport we make use of kink band kinematics to describe the growth of the structure two specific models are presented which consider both 1 background regional sedimentation and 2 local erosion transport and sedimentation the first model approximates structures developed in submarine environments where structural growth may lead to the development of a bathymetric high the model shows considerable lateral changes in the geometries of growth strata along the structure with unconformities being limited to regions of high displacement and with growth triangles being variably developed but in some circumstances difficult to recognise the subaerial model approximates structures developed in settings where sediments simply aggrade to the local base level in this model unconformities are much more prominent as growth sedimentation is often limited to regions of lower displacement the results presented here emphasise the utility of using 3d information on stratigraphic architectures to decipher the growth style and deformational history of natural structures in particular we show that cross sections oblique to the transport direction may contain complex and highly variable pre and syn tectonic geometries that reflect both kink band migration and limb rotation the use of oblique two dimensional 2d information to interpret 3d structures could produce misinterpretations if the complexities of stratigraphic configurations in three dimensions are not taken into account

western alpine back thrusting as subsidence mechanism in the tertiary piedmont basin western po plain nw italy abstract basin formation dynamics of the tertiary piedmont basin tpb are here investigated by means of cross section numerical modelling previous works hypothesised that basin subsidence occurred due first to extension oligocene and then to subsequent loading due to back thrusting miocene however structural evidence shows that the tpb was mainly under contraction from oligocene until post pliocene time while extension played a minor role furthermore thermal indicators strongly call for a cold flexure induced mechanism but are strictly inconsistent with a hot thermally induced mechanism our new modelling shows that the tpb stratigraphic features can be reproduced by flexure of a visco elastic plate loaded by back thrusts active in the western alps in oligo miocene times far field compression contributed to the tpb subsidence and controlled the basin infill geometry by enhancing basin tilting forebulge uplift and erosion of the southern margin of the basin these results suggest that the tpb subsidence is the result of a combination of mechanisms including thrust loading and far field compressional stresses

modelling of piggyback basin stratigraphy record of tectonic evolution abstract the tectono stratigraphic evolution of foreland basins is influenced by processes acting on local regional and global scale in this paper the effects of these processes on the basin evolution are investigated using a forward reconstruction model based on the principles of balanced cross section the modelling incorporates the consequences of thrust deformation sedimentation erosion basement subsidence and sealevel changes on the basin stratigraphy basement subsidence due to lithospheric loading is the main cause of foreland basin formation but appears to have minor implications for the occurrence of angular unconformities in the stratigraphie record of piggyback basins thrusting is probably the dominant factor in the control of the stratigraphie evolution of piggyback basins overprinting the effect of eustasy detailed analyses of stratigraphie data enable the reconstruction of the structural evolution of the underlying thrust system modelling of the northern apenninic po basin shows that neogene stratigraphie sequences of the proximal part of the basin can be explained by tectonic activity of the apenninic fold and thrust belt strong basement subsidence accompanied with deep seated mid pliocene thrusting controls the stratigraphie record of the po piggyback basins

plio quaternary vertical motion of the northern apennines insights from dynamic modeling we test the effects of different geodynamic mechanisms on the pliocene to present day dynamics and in particular on the vertical motions of the northern apennines system by means of two dimensional finite element models we show that the pliocene features of the northern apennines exhumation of deep rocks in western italy and fast subsidence rates in the adriatic foredeep can be adequately reproduced by a model slab characterized by the passive sinking of a negatively buoyant adriatic slab and by the upwelling of buoyant asthenosphere beneath western italy model slab is however not able to account for the quaternary and present day pattern of vertical motion of eastern italy and of the adriatic basin a deep configuration of the system characterized by a detached slab model detach may explain the vertical motions of these areas constrained by uplift of the eastern portions of the apenninic chain by an eastward shift of the foredeep depocenter and by lower subsidence rates in the adriatic basin the tectonic and stratigraphic data showing major differences between the tertiary and the quaternary evolution of the northern apennines are discussed

the origin of sedimentary basins a status report from the task force of the international lithosphere program abstract better insights into the mechanisms of basin formation have a direct bearing on the predictive power of forward models for basin fill models that link flexure normal faulting and thrusting on a subbasin scale provide important constraints on the tectonic control of the sedimentary record enabling a quantitative comparsion with eustatic contributions to the basin architecture thus of special importance is the need to link processes with different spatial and temporal scales involved in the evolution of extensional and compressional basins by numerical modelling a new generation of basin modelling concepts and techniques is one of the main objectives of the task force origin of sedimentary basins of the international lithosphere program the focus of this work is on the quantification of the effects of the thermomechanical structure of the lithosphere and its interplay with regional and local stress changes other important developments include the step towards three dimensional modelling and the full integration of rapidly expanding fission track and other data sets to constrain vertical motions in basins as natural laboratories for the interactive testing and development of new basin modelling techniques a number of basins with high quality data from industry government and academia have been selected on the basis of specific testable problems

on the extratropical influence of variations of the upper tropospheric equatorial zonal mean zonal wind during boreal winter abstractvariations in the global tropospheric zonal mean zonal wind u during boreal winter are investigated using rotated empirical orthogonal functions applied to monthly means the first two modes correspond to the northern and southern annular mode and modes 3 and 4 represent variability in the tropics one is related to el nino southern oscillation and the other has variability that is highly correlated with the time series of u at 150 hpa between 5 n and 5 s u150 e and is related to activity of the madden julian oscillation the extratropical response to u150 e is investigated using linear regressions of 500 hpa geopotential height onto the u150 e time series use is made of reanalysis data and of the ensemble mean output from a relaxation experiment using the european centre for medium range weather forecasts model in which the tropical atmosphere is relaxed toward reanalysis data the regression analysis reveals that a shift of the aleutian low and a wave train across the north atlantic are

interplay of extensional and compression in basin formation this volume contains a collection of papers on the interplay of extension and compression in basin dynamics presented at the 4th annual workshop of the international lithosphere project task force origin of sedimentary basins in benevento italy 25 september l october 1993 previous workshops of the ilp task force have been held in rueil malmaison france 19901 in matrahaza hungary 1991 on the rim of the pannonian basin and in sundvollen in the oslo rift 1992 meeting reports have been published in a number of special volumes and papers cloetingh et al 1993a b 1994 cloetingh sassi and task force team 1994 the 5th task force meeting focusing on basin extension and strike slip tectonics was held in the dead sea rift israel 29 september 5 october 1994 a selection of papers presented at the 5th task force workshop will be published in a forthcoming special volume of tectonophysics the 1995 workshop has taken place in the southern pyrenean foreland basin to examine the relationships between tectonics and eustasy in foreland fold and thrust belts the emphasis of the benevento workshop was on

the effect of the hadley circulation on the meridional propagation of stationary waves the effect on the meridional propagation of stationary planetary waves of the inclusion of the zonal mean hadley circulation in linearized models of the atmosphere is examined in a forced barotropic vorticity equation model a meridional wind in the basic state enables wave propagation through tropical easterlies in the direction of the wind this is shown to be consistent with the wkb solution in a multi level linearized steady primitive equation model with an idealized meridional circulation tropical forcing can still produce response through easterlies although propagation from one mid latitude to the other is much less than in the barotropic result this is explained through wkb and wave tracing methods for a simplified three dimensional vorticity equation the near non divergence of the unforced tropical motion permits a wave to travel largely within a layer of favourable winds in a twelve level model using observed january and july zonal mean conditions the hadley circulation changes the response to earth topographic forcing mainly in the subtropics however tropical heat forcing can now produce a large mid latitude response in the winter hemisphere especially the resulting subtropical jets suggest a mechanism for the maintenance of those observed over australia during the northern monsoon season and adjacent to the anomalous forcing of the 1983 el nino

sedimentology stratigraphy and tectonics of evolving wedge top depozone ariano basin southern apennines italy the late zanclean wedge top ariano basin located in the external sector of the southern apennines was initially characterized by alluvial and fan delta environments and successively southward of the benevento buonalbergo fault by a gradual drowning with coastal and alluvial plains evolving to shelf and marine coastal settings respectively basin evolution continued with a synsedimentary uplift of different sectors resulting in variations in the drainage pattern and basin shape and ultimately leading to complete basin closure and transition to continental depositional environments early pliocene paleogeography prior to the ariano basin activity is due to regional subsidence and subsequent differential uplifts that resulted from geodynamic processes related to both the downgoing apulian slab and the allochthonous orogenic wedge slab break off and the migration of a tear in the southeastward apulian slab occurred producing a strong subsidence in the external sectors of the southern apennines recorded by the development of the ariano basin subsequently out of sequence synsedimentary thrusting related to thin skinned tectonics occurred in the allochthonous units and unconformably overlying wedge top basin deposits producing northeastward migration of the main depocenters in the ariano basin finally renewed thrusting related to the inversion of pre existing normal faults located in the buried apulian platform and enhanced by regional uplift affected the whole tectonic and sedimentary pile as recorded by deformation of the overlying pliocene deposits

growth fault bend folding at southeast lost hills san joaquin valley california synsedimentary deformation has created complex structural and stratigraphic relationships along the west side of the san joaquin valley california this case study of lost hills anticline documents how a simple structural process fault bend folding results in complex growth stratigraphy lost hills anticline is a fault bend fold caused by a step in the lost hills thrust the thrust steps up to the northeast at 27 from a detachment at the base of the tertiary to an upper detachment in the reef ridge formation the lower and upper detachments are at 20 000 ft 6 km and 13 000 ft 4 km displacement on the lower detachment is approximately 4 mi 6 5 km folding consumes 1 2 mi 2 km and the remaining 2 8 mi 4 5 km continues northeast beneath the san joaquin va ley forward and back limb dips of 42 and 27 respectively are consistent with fault bend fold theory pliocene pleistocene sediments onlap a time transgressive unconformity on the northeast front limb but have uniform dip and thickness on the southwest back limb this characteristic growth fault bend fold geometry indicates basinal sediments rolled through an axial surface onto the back limb whereas contemporaneous sediments deposited above the front limb are undeformed basinal sediments onlapping the fold crest indicates fault slip is greater than ramp length onlapping growth sediments indicate folding began during deposition of the etchegoin formation 8 ma and continued to the late pleistocene or holocene corresponding to an average displacement rate on the lost hills thrust of 2 700 ft m y 820 m m y continuous burial of the fold during growth caused each material e physical point in the fold to be at its maximum depth of burial contours of equal density and seismic velocity are relatively flat so that the anticline causes little or no gravity anomaly and less than expected pullup in seismic time sections the geometry of growth sediments imaged on seismic lines indicates lost hills and adjacent anticlines grew by uniform displacement to the northeast with no significant rotation oblique convergence between the pacific and north american plates is manifested as synchronous but spatially separate transcurrent and compressive displacements thus lost hills anticline and perhaps other folds in the area are more appropriately described as compressive folds in a transpressive region than as transpressive folds duplicated lower tertiary strata beneath the lost hills kettleman hills trend are potential targets for petroleum exploration

tropical stationary waves in a nonlinear shallow water model with realistic basic states abstract the nonlinear shallow water equations are used to study the tropical stationary wave response to steady thermal forcing near the equator in earthlike zonally symmetric basic states a thin 200 m fluid layer is superimposed over a large 1500 m zonally symmetric topography distribution that decreases smoothly from the tropics to the poles thus providing the large meridional height gradients required to maintain realistic zonal mean zonal winds without introducing unrealistically large tropical wave speeds a mean meridional circulation is maintained by relaxing the fluid toward its initial global mean depth both hemispherically symmetric equinoctial and hemispherically asymmetric solstitial basic states are considered stationary waves are generated by adding a fixed mass source sink distribution near the equator the presence of westerly zonal mean winds in the subtropics amplifies the steady eddy response to the tropical mass forcing and shifts the rossby gyres poleward and eastward r

the walker circulation with observed zonal winds a mean hadley cell and cumulus friction abstract the term walker circulation is used to refer to the zonal overturning across the equatorial pacific driven by enhanced convection over the indonesian region in this work an attempt is made to simulate the walker circulation using a linear model that includes a cumulus friction parameterization the work of geisler is extended by including a realistic mean zonal wind field obtained from the fgge dataset and a prescribed mean hadley cell that is computed from an analytical streamfunction the model is forced by a stationary tropical heat source the sensitivity of the model circulation to changes in the basic state is examined model results show that the inclusion of a nonzero mean zonal wind field tends to enhance the extratropical response in the winter hemisphere including a cumulus friction parameterization tends to damp the zonal wind response near the heating center and also lower the level of zero zonal wind in the model walker circulation including a mean hadley cell in the basic state

tropical wave driving of the annual cycle in tropical tropopause temperatures part ii model results abstract the atmospheric response to a localized distribution of tropical heating is examined in terms of the stationary waves excited and how these impact the mean flow near the tropical tropopause this is done by examining nonlinear simulations of the gill model with a primitive equation model that extends from the surface up into the stratosphere the model produces strong cooling of zonal mean temperatures near the tropical tropopause when the heating is on the equator but weaker cooling with the heating at 15 n the model shows that equatorial rossby waves that penetrate the lower stratosphere and changes in ep flux divergence that correspond to the observed changes between december and august it is suggested that ascent in the upper tropical troposphere is driven by vorticity advection or equivalently potential vorticity fluxes due to these equatorial rossby waves particularly when the heating is close to the equator the model results provide support to the hypothesis that the annual cycle in tr

why are the climatological zonal winds easterly in the equatorialupper troposphere abstract using 16 years of ncep ncar reanalysis data on the 200 mb surface it is shown that in the deep tropics the horizontal transient eddy momentum flux accelerates the zonal mean zonal wind this acceleration is mainly due to transient eddies of intraannual and interannual timescales and to those associated with the madden julian oscillation mjo the interannual timescale eddy fluxes are dominated by eastward propagating disturbances with zonal wavenumber 2 and a period of 2 4 yr suggesting that these eddy fluxes may be tied to the el nino southern oscillation in the deep tropics the single most important factor that decelerates the zonal mean zonal wind is the horizontal momentum flux divergence due to the transient meridional circulation associated with seasonal cycle of the hadley cells the deceleration by the transient meridional circulation is much greater than the acceleration due to the transient eddies this result indicates that a nonzero obliquity of the earth is crucial for maintai

a new active tectonic model for the construction of the northern apennines mountain front near bologna italy 1 we integrate existing and new geologic data retreating trench extension and accretion tectonics retreat project particularly on the origin growth and activity of the mountain front at bologna italy into a new model that explains apennine orogenesis in the context of a slab rollback upper plate retreat process the bologna mountain front is an actively growing structure driving rock uplift 1 mm year cored by a midcrustal flat ramp structure that accommodates ongoing shortening driven by adria subduction at a rate of 2 5 mm year the data we use are assembled from river terraces and associated pleistocene growth strata geodesy including releveling surveys reinterpretation of published reflection lines and a new high resolution reflection line these data constrain a simple trishear model that inverts for blind thrust ramp depth dip and slip apennine extension is recognized both in the foreland as high angle normal faults and modest stretching in the carapace of the growing mountain front and in the hinterland with larger normal faults that accomplish some crustal thinning as the upper plate retreats this coevolution of extension and shortening shares some notable characteristics with other basement involved collisional orogens including the early tertiary laramide orogeny in the american west and the oligocene to miocene evolution of the alps we propose a possible relationship between underplating and the development of the po as a sag basin as a quaternary phenomenon that may also apply to past periods of apennine deformation tortonian continued shortening on the structure beneath the bologna mountain front represents by far the most important and underappreciated seismogenic source in the front of the northern apennines

cyclicity and basin axis shift in a piggyback basin towards modelling of the eocene tremp ager basin south pyrenees spain

on the role of planetary scale waves in the abrupt seasonal transition of the northern hemisphere general circulation the role of planetary scale waves in the abrupt seasonal transition of the northern hemisphere nh general circulation is studied in reanalysis data the winter to summer transition involves the growth of planetary scale wave latent heat and momentum transports in the region of monsoons and anticyclones that dominate over the zonal mean transport beginning in midspring the wave dominated regime coincides with an abrupt northward expansion of the cross equatorial circulation and reversal of the trade winds in the upper troposphere the transition coincides with the growth of cross equatorial planetary scale wave momentum transport and a poleward shift of subplanetary scale wave transport and jet stream the dynamics of the seasonal transition are captured by idealized aquaplanet model simulations with a prescribed subtropical planetary scale wave sea surface temperature sst perturbation the sst perturbation generates subtropical planetary scale wave streamfunction variance and transport in the lower and uppertroposphereconsistentwithquasigeostrophictheory beyondathresholdsst atransitionofthezonalmean circulation occurs which coincides with a localized reversal of absolute vorticity in the nh tropical upper troposphere the transition is abrupt in the lower troposphere because of the quadratic dependence of the wave transport on the sst perturbation and involves seasonal time scale feedbacks between the wave and zonal meanflow in theupper troposphere including cross equatorial wave propagation thezonal mean vertical and meridional flows associated with the circulation response are in balance with the planetary scale wave momentumand latentheat meridionalflux divergences the resultshighlightthe leading order roleofmonsoon anticyclone transport in the seasonal transition including its impact on the meridional extent of the hadley and ferrel cells they can also be used to explain why the transition is less abrupt in the southern hemisphere

the klagenfurt basin in the eastern alps an intra orogenic decoupled flexural basin abstract the klagenfurt basin is an e w trending narrow sarmation to quaternary flexural basin formed by flexure of the austro alpine lithosphere by loading through the southerly adjacent karawanken mountains in the eastern alps austria the tectonic evolution of the basin is kinematically connected to miocene brittle transpressive dextral strike slip deformation along the periadriatic fault which separates the south alpine unit from the austro alpine unit in the eastern alps the final nw directed overthrust of the karawanken mountains onto the foreland is characterised by a positive flower structure which is kinematically linked to dextral transpressive shearing along the periadriatic fault only a small part of the lithosphere appears to support the regional isostatic response to the load by the karawanken mountains the area is characterised by a crustal thickness between 40 and 45 km elevated heat flow and a strength distribution which suggests that only the upper crust elastically supports the topographic load ductile flow of the lower crust is also supported by the absence of a crustal root beneath the karawanken chain rheologic models for this lithospheric configuration indicate a mechanical decoupling of upper crust lower crust and mantle and generally low strengths for the lower crust and mantle

correlating shelf carbonate evolutive phases with fluid expulsion episodes in the foredeep miocene northern apennines italy abstract in the miocene of the northern apennines of italy evolutionary phases of shallow water carbonates in wedge top basins are coeval with methane rich fluid expulsion episodes in the inner foredeep we identified four main correlative events primarily controlled by synsedimentary tectonics sediment input and climate cooling 1 a burdigalian tectonic phase determined the onset of shelfal sedimentation in wedge top areas and is correlated with an important episode of fluid expulsion in marly sediments of the inner foredeep croce di moggiona seep carbonates 2 the decrease of shelfal carbonate production and the increase of detrital input in the early langhian correspond with a second important episode of seep carbonate precipitation in the inner foredeep castagno d andrea 3 the demise of the carbonate shelf and the coeval expulsion of methane rich fluids in the inner foredeep vicchio and m citerna seep carbonates at the langhian serravallian boundary approximate the mi3b cooling event the lower temperatures associated with increased siliciclastic weathering led to the crisis of shallow water carbonate production whereas the pressure drop due to the eustatic fall may have triggered the gas charged fluid expulsion 4 the tectonic related uplift of frontal sectors of the wedge top basin led to the wide erosion of the burdigalian langhian carbonates and caused the precipitation of authigenic seep carbonates deruta seep both in the slope and the adjacent foredeep

subsidence analysis in thrust tectonics application to the southeastern pyrenean foreland abstract this case study conducted in the pyrenees examines the application of 1d subsidence analysis in thrust tectonics by integrating subsidence analysis with sequence stratigraphy and structure significant changes between the subsidence curves of the southeastern pyrenean thrust sheets are seen to occur bearing a close relationship to regional unconformities and variations in the sedimentary record of each thrust sheet a comparative study examining the correlation between the tectonic subsidence curves of the thrust sheets and those of the autochthon shows that the essential structure of the southward sequence of thrust sheets palaeozoic axial zone not included was piggy back developed in only 6 m y the northern garrotxa antiformal stacks started to emplace 50 7 ma ago as can be interpreted from their linear shaped curve and anomalously low subsidence rate 7 cm ka and preservation of continental platform whereas the southern cadi thrust sheet underwent strong subsidence acceleration up to 60 cm ky related to the development of a deep starved continental slope comparison between coeval platform sections with good palaeobathymetric constraints and slope sections provides an estimate for slope palaeobathymetry up to 650 900 m the cadi thrust sheet was emplaced at about 49 5 ma as can be deduced from dramatic subsidence deceleration in its curves related to shallowing resumption of siliciclastic sedimentation and broad erosion of the continental platform areas of the cadi thrust sheet meanwhile the curves of the serrat thrust sheet and those of the autochthon recorded significant subsidence acceleration 30 40 cm ka and 15 cm ka respectively finally the serrat thrust sheet was emplaced at 45 ma as can be inferred from the decelerated subsidence in its curve associated with shallowing emergence and broad molasse sedimentation whereas in the foreland plate the subsidence accelerated and was related to the onset of marine sedimentation

a synthetic stratigraphic model of foreland basin development the processes of erosion and deposition must be included in foreland basin models to predict correctly basin geometry and stratigraphy we present a synthetic stratigraphic model of the development of nonmarine foreland basins that predicts progressive geometry topography and facies patterns in the model steady crustal shortening occurs according to a wedgethickening model erosion and deposition follow a diffusive process and the lithosphere is compensated elastically erosion and deposition are controlled by the transport coefficients r of the diffusion equation for a range of thrust velocities and lithospheric rigidities transport coefficients are of order 102 103 m yr in the mountain belt these values are much higher than those derived from the study of scarp degradation in the sedimentary basin transport coefficients of order 104 m2 yr are appropriate and are compatible with previous studies of fluvial and deltaic deposition rapid thrusting results in a narrow underfilled basin while slow thrusting results in a wide overfilled basin in addition by varying the erosional and depositional transport coefficients while holding other parameters constant we generate both overfilled and underfilled basins these results suggest that changes in the rate of thrust loading the climate or the source rock lithology can create stratigraphic signatures that have been interpreted to record viscoelastic relaxation of the lithosphere clearly to understand either the long term behavior of the lithosphere or to interpret orogenic history from preserved foreland strata the manner in which a basin was filled must be considered we apply the model to the evolution of the modern sub andean foreland and find that an erosional transport coefficient of 3000 m2 yr and a depositional transport coefficient of 20 000 m2 yr successfully predict the observed basin geometry

different foreland basins in italy examples from the central and southern adriatic sea abstract the central adriatic basin cab and the southern adriatic basin sab are foreland or foredeep basins relative to the non coeval apenninic and dinaric hellenic orogenic systems and currently characterized by different physiographies these are separated by a major forebulge of the adriatic lithosphere running throughout the adriatic region from istria to the gargano promontory the clastic basin filling of the cab is mostly plio pleistocene whereas it is upper oligocene pleistocene in the sab stratigraphy reveals that the cab has experienced an overfilling regime throughout the plio pleistocene whereas the sab has been probably continuously underfilled during the same time span in the cab the foreland plate dips westward at an average angle of 5 6 whereas in the sab the basement dips to the east at an angle of 1 2 this discrepancy is congruent with the already noticed distinction between east and west dipping subduction systems and possibly has geodynamical implications in the cab the non homogeneous distribution of thrust sheets suggests strike slip tectonic movements along roughly ne trending lineaments that occurred up to the middle late pliocene on the western part of the sab the overall structural assemblage recalls the fabric typical to strike slip regimes and includesboth extensional and contractional structures it is proposed that the messinian salinity crisis and relative eustatic lowstand affected the subsequent tectono sedimentary evolution of the cab in terms of subsidence rate and depositional style one still tentative hypothesis is that water and sediment removal in the basin lasted for a sufficient time span to promote viscoelastic relaxation temporary migration of the forebulge towards the thrust belt and downwarping of the foreland plate

the residual mean circulation in the tropical tropopause layer driven by tropical waves abstractlatent heating estimates derived from rainfall observations are used to construct model experiments that isolate equatorial waves forced by tropical convection from midlatitude synoptic scale waves these experiments are used to demonstrate that quasi stationary equatorial rossby waves forced by latent heating drive most of the observed residual mean upwelling across the tropopause transition layer within 15 of the equator the seasonal variation of the equatorial waves and the mean meridional upwelling that they cause is examined for two full years from 2006 to 2007 changes in equatorial rossby wave propagation through seasonally varying mean winds are the primary mechanism for producing an annual variation in the residual mean upwelling in the tropical tropopause layer averaged within 15 of the equator and between 90 and 190 hpa the annual cycle varies between a maximum upwelling of 0 4 mm s 1 during boreal winter and spring and a minimum of 0 2 mm s 1 during boreal summer this variabilit

maintenance of the intertropical convergence zones and the large scale tropical circulation on a water covered earth abstract how the surface boundary heating sea surface temperature and cumulus adjustment process affect the location structure energetics and dynamics of the intertropical convergence zones itczs is investigated a series of experiments is performed with a general circulation model where the lower boundary is specified to be water at a fixed sea surface temperature sst an aqua planet all experiments are run using equinoctal insolation with no longitudinal variation in sst two different convective parameterization schemes kuo and moist convective adjustment and several different zonally symmetric sst distributions are used in these experiments the location of the itcz is found to be sensitive to the convective parameterization scheme and the sst distribution the model with the moist convective adjustment scheme produces an itcz over the tropical sst maximum even under conditions where the sst gradient is weak by contrast the model with the kuo convective parameterization is not as sensit

zonal momentum balance in the tropical atmospheric circulation during the global monsoon mature months abstractin this paper zonal momentum balances of the tropical atmospheric circulation during the global monsoon mature months january and july are analyzed in three dimensions based on the ecmwf interim re analysis era interim it is found that the dominant terms in the balance of the atmospheric boundary layer abl in both months are the pressure gradient force the coriolis force and friction the nonlinear advection term plays a significant role only in the asian summer monsoon regions within the abl in the upper troposphere the pressure gradient force the coriolis force and the nonlinear advection are the dominant terms the transient eddy force and the residual force which can be explained as convective momentum transfer over open oceans are secondary yet cannot be neglected near the equator zonal mean equatorial upper troposphere easterlies are maintained by the absolute angular momentum advection associated with the cross equatorial hadley circulation equatorial upper troposphere ea

equatorial superrotation and the factors controlling the zonal mean zonal winds in the tropical upper troposphere the response of the zonal mean zonal winds in the tropical upper troposphere to thermal forcing in the tropics is studied using an idealized general circulation model with 18 vertical levels and simplified atmospheric physics the model produces a conventional general circulation with deep easterly flow over the equator when integrated using zonally invariant and hemispherically symmetric boundary conditions but persistent equatorial superrotation westerly zonal mean flow over the equator is obtained when steady longitudinal variations in diabatic heating are imposed at low latitudes the superrotation is driven by horizontal eddy momentum fluxes associated with the stationary planetary wave response to the applied tropical heating the strength of the equatorial westerlies is ultimately limited by vertical steady eddy momentum fluxes which are downward in the tropical upper troposphere and by the zonally averaged circulation in the meridional plane which erodes the mean westerly shear via vertical advection the transition to superrotation can be prevented by specifying offsetting zonally invariant heating and cooling anomalies on either side of the equator to create a solstitial basic state with a single dominant hadley cell straddling the equator superrotation is restricted in the solstitial climate because the strength of the mean meridional overturning is enhanced which increases the efficiency of vertical advection and because the cross equatorial flow in the upper troposphere provides an easterly zonal acceleration that offsets some of the momentum flux convergence associated with tropical eddy heating the cross equatorial flow aloft also reduces the stationary planetary wave response in the summer hemisphere these results suggest that hemispheric asymmetry in the mean meridional circulation is responsible for maintaining the observed mean easterly flow in the tropical upper troposphere against the westerly torques associated with tropical wave sources

some atmospheric processes governing the large scale tropical circulation in idealized aquaplanet simulations abstract the large scale tropical atmospheric circulation is analyzed in idealized aquaplanet simulations using an atmospheric general circulation model idealized sea surface temperatures ssts are used as lower boundary conditions to provoke modifications of the atmospheric general circulation results show that 1 an increase in the meridional sst gradients of the tropical region drastically strengthens the hadley circulation intensity 2 the presence of equatorial zonal sst anomalies weakens the hadley cells and reinforces the walker circulation and 3 a uniform sst warming causes small and nonsystematic changes of the hadley and walker circulations in all simulations the jet streams strengthen and move equatorward as the hadley cells strengthen and become narrower some relevant mechanisms are then proposed to interpret the large range of behaviors obtained from the simulations first the zonal momentum transport by transient and stationary eddies is shown to modulate the eddy driven jets whic

consequences of thrusting and intraplate stress fluctuations for vertical motions in foreland basins and peripheral areas summary we present a conceptual model for short term and long term alternations in subsidence and uplift in foreland basins convergence of lithospheric plates produces forces at the plate boundaries generating stresses in the accretionary wedge the underthrusted crust and the lithosphere when the stresses reach the shear strength of the rocks in these units deformation which results in the redistribution of mass takes place contemporaneously with reduction of the stress level modelling of both the effects of this alternating building up and relaxation of stress and the effects of the resulting mass redistribution on foreland basin geometry employing an elastic rheology of the lithosphere demonstrates that these processes exert an important control on the shape of foreland basins vertical motions take place on different time scales dependent on the scale of thrusting and the style of deformation short term 10 104 yr vertical motions are related to small scale thrust events while long term vertical motions are induced by larger scale deformation in the overriding thrust wedge furthermore the geometry of faults influences the duration of the magnitude of stress fluctuations stress induced alternations of subsidence may lead to the deposition of alternating sequences in foreland basins on scales of centimetres e g cyclothems to scales of several hundreds of metres on lap and off lap sequences in this respect the mechanical coupling between convergent zones and peripheral areas is of particular importance as it induces simultaneous alternations in regional facies patterns the model also provides an explanation for vertical motions in the foreland basin previously attributed to visco elastic relaxation processes

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

sedimentary basins formed and carried piggyback on active thrust sheets small sedimentary basins that formed on the apennine southern margin of the po basin complex northern italy have been studied using borehole and seismic reflection information and their evolution can be dated using the largely marine biostratigraphy of the miocene to quaternary sediments these studies show that the basins formed and were filled while being carried on moving thrust sheets and they are therefore named piggyback basins each of these basins corresponds to the active phase of a different thrust front ramp on the pyrenean northern margin of the ebro basin complex northern spain similar piggyback basins formed between eocene and mid miocene time they have since been uplifted and eroded and may therefore be studied in outcrop in northern spain much of the basin fill sediment was deposited in nonmarine environments

two and three dimensional numerical simulations of the stress field at the thrust front of the northern apennines italy 1 two and three dimensional mechanical models simulating the seismic cycle along thrust faults are devoted to the active front of the northern apennines buried under the plio pleistocene sediments of the eastern po plain the models aim at understanding two peculiar characters of the stress field in the region 1 analyses of borehole breakouts and other well data integrated with seismological information and field evidence show along depth variations from extensional to strike slip to compressional for increasing depth of the stress style along the active mirandola anticline and 2 seismic and borehole breakout data suggest strong lateral rotations of the stress axes along the frontal and lateral ramp portions of the mirandola thrust fault modeling results allowed us to understand that the mechanical decoupling along faults strongly affects the stress distribution in their vicinity under the form of strong rotations of the principal stress axes as a consequence the slip either fast or slow along active blind thrust faults could drive to local stress fields very different from that associated with regional tectonics this could explain together with other processes such as differential compaction the along depth variation of the stress field observed in the mirandola region and the strong lateral rotations of the principal stress axes observed along the lateral ramp of the mirandola thrust fault finally the seismic activity along one of the thrust fault ramps along the apennines front should not interfere with the state of stress along adjacent ramps

episodicity in foredeep basins the stratigraphic record contained in several foredeep basins is incompatible with the formation of these basins by flexure of a homogeneously strong foreland lithosphere for example the stratigraphy of the early proterozoic kilohigok foredeep basin of northern canada indicates that the inner part of the basin deepened in time without migration of the flexural bulge toward the foreland and that the flexural bulge remained fixed in time relative to the downgoing plate one mechanism that may be responsible for the localization of the flexural bulge in the kilohigok and similar basins is that of lateral strength variations in the flexing lithosphere our results show that lateral strength variations within the foreland lithosphere can produce temporal variations in basin geometry and also serve to localize the position of the flexural bulge relative to the foreland for extended periods of time this produces basin episodicity on a time scale of millions to tens of millions of years perfectly elastic models require a large strength contrast about 50 in elastic plate thickness but a brittle elastic ductile lithosphere rheology reduces the magnitude of the strength contrast required for episodicity to about 10 15 of the initial effective elastic plate thickness we suggest that basin episodicity may induce comparable episodicity in the coeval thrust belt because theoretical studies of thrust mechanics suggest that the deformation in thrust belts is highly sensitive to the dip of the basal thrust angle through mechanisms such as this the laterally heterogeneous continental lithosphere may provide a natural filter that transforms the presumably continuous and smoothly varying processes of the mantle into the spatially irregular and temporally episodic deformation observed in the crust at time scales of tens of millions of years

abrupt transition to strong superrotation driven by equatorial wave resonance in an idealized gcm persistent superrotation is seen in the atmospheres of other terrestrial bodies venus titan but not in that of present earth which is distinguished by equatorial easterlies nevertheless superrotation has appeared in numerical simulations of earth s atmosphere from two layer models to multilevel comprehensive gcms simulations of warm climates that generate enhanced tropical convective variability seem particularly prone to superrotation which has led to hypotheses that the warmer atmospheres of the early pliocene and eocene may have been superrotating and that the phenomenon may be relevant to future climate projections this paper considers a positive feedback leading to superrotation based on an equatorial wave resonance that occurs in a westerly backgroundflow the authors present simulations with an idealized multilevel gcm forced with a zonally varying equatorial heating which show abrupt transitions to strongly superrotating states linearshallowwatertheoryisusedtoshow thatthesetransitions occur asthesuperrotating jetvelocity approaches the phase speed of free equatorial rossby wave modes leading to a resonant amplification of the response to eddy heating and its associated equatorward momentum flux the resonance and transition are most prominent in simulations where the meridional temperature gradient has been reduced and hysteresis behavior is seen when the gradient is eliminated completely no evidence is found in these simulations for the midlatitude wave feedback believed to drive abrupt transitions in two layer models and there is only a minor role for the axisymmetric feedback based on vertical advection by the hadley circulation

seismic stratigraphy of a neogene piggyback basin argentina depositional sequences composed of neogene nonmarine strata are imaged on seismic reflection data from the iglesia piggyback basin argentina the strata accumulated in an internally drained basin located between the frontal cordillera the high andes and the precordillera thrust belt two reflection geometries onlap and truncation are observed along four unconformities within the neogene section onlap of reflections onto unconformities defines five distinct intervals of basin growth local truncation of reflections beneath unconformities defines four intervening intervals of nondeposition or erosion along strike variation in the amount of truncation suggests that erosion was limited to zones through which major streams entered the basin postdepositional thrusting o the east side of the basin produced field exposures of the five sequences and allowed examination of the nature of the sequence boundaries the iglesia depositional sequences are interpreted to result from neogene crustal shortening within the central andes the iglesia basin has been passively transported above a horizontal decollement that links mid crustal deformation beneath the frontal cordillera with surface thrusting in the precordillera deposition resulting generally from simultaneous uplift of the frontal cordillera and the precordillera can be explained by two scenarios thrust controlled accumulation where space for deposition was created only during faulting or drainage controlled accumulation where deposition occurred only when thrusting cut off through going drainages linking the iglesia basin with the foreland

the generation of global rotational flow by steady idealized tropical divergence abstract tropical convective heating is balanced on the large scale by the adiabatic cooling of ascent the horizontal divergence of the wind above this heating may be viewed as driving the upper tropospheric rotational wind field a vorticity equation model is used to diagnose this relationship it is shown that because of the advection of vorticity by the divergent component of the flow the rossby wave source can be very different from the simple fd source often used in particular an equatorial region of divergence situated in easterly winds can lead to a rossby wave source in the subtropical westerlies where it is extremely effective this part of the source can be relatively insensitive to the longitudinal position of the equatorial divergence a divergence field which is asymmetric about the equator can lead to a quite symmetric rossby wave source for a steady frictionless flow the rossby wave source averaged over regions within closed streamfunction or absolute vorticity contours is under cert

flexural behavior of the continental lithosphere in italy constraints imposed by gravity and deflection data a procedure is developed that systematically matches observations of plate flexure and gravity anomalies at simple convergent boundaries to the bestfitting two dimensional flexural geometry obtained by a thin elastic sheet of specified elastic strength the procedure allows analytical solution for three independent variables one of which is the initial preflexure elevation of the reference surface and two of which are related to the vertical forces and bending moments that act on the plate application to four profiles constructed across the apennine convergent system in italy shows that the observed depth of the basal pliocene surface which marks the base of the foredeep basin and the observed bouguer gravity anomalies can be fit by a two dimensional elastic plate model with an effective elastic thickness of about 20 km on three profiles and about 10 km on the fourth profile the initial elevation prior to flexure is determined to have been about 1000 m below sealevel on all profiles large bending moments and or vertical shear forces are required to act at the effective plate ends in order to maintain the observed deflection moments between 0 5 1017 and 3 1017 n and shear forces between 3 1012 and 3 1012 n m gravity modelling indicates that on the two northernmost profiles these terminal forces can not be supplied by a static mass at crustal depths and suggests that on all four profiles the terminal forces are supplied by anomalously dense material present at depths of 75 150 km beneath and west of the west coast of italy this dense material probably corresponds to westward subducted lithosphere of the adriatic plate extending from the northern apennines to the southern apennines and calabria this study suggests that in subduction systems like the apennines that are characterized by backarc extension forces acting on subducted lithosphere at depth can be expressed at the surface in the geometry of the foredeep basin that forms adjacent to the subduction zone

equatorial planetary waves and their signature in atmospheric variability abstractequatorial planetary waves are a fundamental component of the tropical climate system previous studies have examined their structure in the climatological mean circulation their role in the climatological mean momentum balance of the tropics and their contribution to the climatological mean upwelling across the tropical tropopause in this study the authors focus on the contribution of the equatorial planetary waves to variability in the tropical circulation about its climatological mean state the equatorial planetary waves that dominate the climatological mean exhibit considerable variability on intraseasonal and interannual time scales variability in the amplitude of the equatorial planetary waves is associated with a distinct pattern of equatorially symmetric climate variability that also emerges from empirical orthogonal function analysis of various tropical dynamical fields variability in the equatorial planetary waves is characterized by variations in 1 convection in the deep tropics

miocene unconformities in the central apennines geodynamic significance and sedimentary basin evolution abstract this paper shows the results obtained from an integrated study geology biostratigraphy and geochemistry carried out on the miocene edimentary deposits in central italy in order to define the timing of the sedimentary basin evolution this paper deals also with the causes of the unconformities recorded in these basins in the miocene deposits of the latina valley and the ernici simbruini mts several unconformities which distinguish different stratigraphic sequences have been recognized d 0 d 1 d 2 d 3 and d 4 for each unconformity a general description together with a geodynamical significance is provided in particular d 0 unconformity appears to be related to a regional tectonic event adria europe collision as a consequence the adria lithosphere folded and the area underwent a regional erosive event d 1 d 2 and d 3 unconformities have had a more local tectonic control since they represent the stratigraphic record of the migration of the apennines thrust belt foredeep system d 1 and d 2 unconformities are related to the late tortonian foredeep stage whereas d 3 is linked to the early messinian piggy back stage moreover the d 4 unconformity which took place during the messinian piggy back stage is strictly linked to the sea level drop of the messinian salinity crisis in this paper the genesis and evolution of a late tortonian foreland basin is also stressed latina valley foredeep basin finally taking into account sequence boundaries nannofossil biostratigraphy and geochemistry isotopic data a comparison with the curve of the 3rd order of the relative coastal onlap haq et al 1988 has been attempted in order to distinguish the unconformities controlled either by tectonic or eustatic processes

late carboniferous tectonic subsidence in south wales implications for variscan basin evolution and tectonic history in sw britain detailed stratigraphic data have been used to backstrip seven sections from the carboniferous south wales coal basin resulting tectonic subsidence curves for the interval 319 305 ma namurian westphalian d are convex up indicating increasing subsidence rate with time with rates between 130 and 250 m ma 1 suggesting a foreland basin setting forward modelling of subsidence due to flexural loading in front of a propagating orogenic wedge shows that an orogenic load migrating in a north northeasterly direction across sw england between 319 and 305 ma could have generated the backstripped subsidence patterns sensitivity tests show that while many of the forward model parameters are poorly constrained and the model results non unique backstripped subsidence patterns allow reasonable constraint on the different model cases so that model predictions can be treated as one possibility in a limited range the predicted load evolution is consistent with current knowledge of tectonic and stratigraphic features of sw england these results suggest that subsidence in other late carboniferous uk basins may also have been influenced by flexure due to a propagating orogenic load

intrabasinal thrust tectonic versus climate control on rhythmicities in the eocene south pyrenean tremp graus foreland basin inferences from forward modelling abstract small scale 10 m sedimentary cycles of alternating fine grained and coarse grained sediments occur in 40 60 m thick fan delta sequences in eocene deposits in the tremp graus foreland basin these deposits are investigated by means of numerical forward modelling of short term 10 100 kyr scale changes in sediment flux due to orbitally induced climate changes and related fluctuations in precipitation and vegetation de boer et al 1991 and as an alternative control intrabasinal fault activity we show that pulsating intrabasinal uplifting related to deep seated thrusting may serve as an alternative to climate induced fluctuations in sediment flux provided that thrusting is cyclic in the models faulting between the source area and the site of the rhythmic succession causes temporal intrabasinal uplift leading to contemporary erosion of the uplifted area and to a nearly instantaneous redistribution of sediment in a thin veneer across a wide area this reduces the effect of flexural subsidence due to fault activity so that major lateral facies shifts through time are absent while significant changes in sediment flux do occur the models also provide new insights into the dominant geodynamic mechanisms during deposition of the eocene sequence to explain the observed sediment thickness in the studied sequence either a sea level rise accompanied by relatively high transportation coefficients larger maximum erosion rates millimetres per year or orogenic wedge growth accompanied by smaller transportation coefficients lower maximum erosion rates tenths of millimetres per year has to be adopted in the case of the eustasy scenario it is predicted that the basin thins to the north in case of the orogenic wedge growth scenario a northward thickening of the basin fill is predicted unless a subsurface triangular fault zone is adopted

dynamics of extensional basin formation and inversion introduction this volume contains a cohection of papers on the dynamics of extensional basin formation and inversion presented at the 3rd annual workshop of the international lithosphere program task force origin of sedimentary basins in sundvollen norway 18 23 august 1992 previous workshops of the ilp task force had been in rueil malmaison france 1990 and in matrahaza hungary 19911 on the rim of the pannonian basin the task force also organized a number of sessions during the 1992 european geophysical society and the 1993 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 stephenson 1993 cloetingh sassi and task force team 1994 the 4th task force meeting focusing on the interplay of extension and compression was held in benevento southern italy in october 1993 a selection of papers presented at that task force workshop will be published in a forthcoming special volume of tectonophysics the emphasis of the 5th workshop of the task force taking place in the dead sea rift israel is on rifting and strike slip tectonics the 1995 workshop will be organized in the southern pyrenean foreland basin with the aim of examining the relationships between tectonics and eustasy in foreland fold and thrust belts the emphasis of the sundvollen workshop was on modelling studies as well as observational approaches to the dynamics of basin extension and inversion important elements of the meeting were the discussion of extensional tectonics rifting in passive margin settings and volcanism and magmatism in rifts and basins following the task force strategy to link subsurface data to field analogues an important part of the meeting was devoted to a thematic excursion in the oslo rift field guides have been published separately larsen et al 1992a

thermo mechanical controls on intra plate deformation and the role of plume folding interactions in continental topography thermo tectonic age and inherited structure exert the main controls on the bulk strength of the lithosphere in intraplate settings mechanical decoupling within the lithosphere strongly affects the interaction between deep earth and surface processes thermo mechanical models demonstrate the particular importance of the rheological stratification of the lithosphere in the preservation of ancient cratonic blocks in the surface expression of plume and mantle lithosphere interactions and their impact on the dynamic topography in general the same is true for the effect of large scale lithospheric folding on intraplate basin formation and associated differential vertical motions initiation of continental lithosphere subduction crucial for linking orogenic deformation to intraplate deformation appears to be facilitated by plume lithosphere interactions we present a discussion of these aspects focusing on better process understanding of continental deformation in the context of a number of well documented cases of intraplate deformation

deepwater fold and thrust belt along new caledonia s western margin relation to post obduction vertical motions classically deepwater fold and thrust belts are classified in two main types depending if they result from near or far field stresses and the understanding of their driving and triggering mechanism is poorly known we present a geophysical dataset off the western margin of new caledonia sw pacific that reveals deformed structures of a deepwater fold and thrust belt that we interpret as a near field gravity driven system which is not located at a rifted passive margin the main factor triggering deformation is inferred to be oversteepening of the margin slope by post obduction isostatic rebound onshore erosion of abnormally dense obducted material combined with sediment loading in the adjacent basin has induced vertical motions that have caused oversteepening of the margin detailed morpho bathymetric seismic stratigraphic and structural analysis reveals that the fold and thrust belt extends 200 km along the margin and 50 km into the new caledonia trough deformation is rooted at depths greater than 5 km beneath the seafloor affects an area of 3500 km2 and involves a sediment volume of approximately 13 000 km3 this deformed belt is organized into an imbricate fan system of faults and one out of sequence thrust fault affects the seabed the thrust faults are deeply rooted in the basin along a low angle floor thrust and connected to new caledonia island along a major detachment this study not only provides a better knowledge of the new caledonia margin but also provides new insight into the mechanisms that trigger deepwater fold and thrust belts

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