a balanced section across the pyrenean orogenic belt evolutionary models that have been proposed for the pyrenean orogenic belt involve gravitational gliding of major thrust sheets to both the north and south of an uplifted central axial zone it has been suggested by previous workers that uplift is a result of alpine compression or long lived strike slip movement on the north pyrenean fault we critically assess these models and propose a new model based on the generation of a thin skinned linked thrust system due to alpine collision of iberia and europe pyrenean alpine tectonics is dominated by southward thrusting on a major sole fault dipping north at approximately 6 within hercynian basement northerly directed thrusts of the north pyrenean zone and northern folded foreland are backthrusts from this sole fault a total orogenic shortening of 106 km in the central pyrenees was achieved between the palaeocene and oligocene at a time averaged rate of 0 62 cm yr 1 a thin skinned model requires that the north pyrenean fault is truncated by both northward and southward moving thrusts and occurs in the footwall of the sole fault some 60km north of its present surface trace

links between orogenic wedge deformation and erosional exhumation evidence from illite age analysis of fault rock and detrital thermochronology of syn tectonic conglomerates in the spanish pyrenees abstract we present new geochronologic data illuminating the tectonic and erosional history of the orogenic wedge exposed in the south central pyrenees spain we interpret illite age analyses from four fault gouges that record thrust belt development and document the importance of out of sequence thrusting fault activity occurs in pulses with slip occurring contemporaneously on multiple faults throughout the wedge new apatite fission track data from syn orogenic sediments of the sis conglomerate body reveal ages of 48 to 42 ma with no consistent variation upsection in strata deposited from 41 to 30 ma we interpret these data as well as thermal modeling of track length distributions to imply rapid cooling in the interior of the pyrenean wedge during the middle eocene the record of fault activity and erosion suggests that orogenic wedges may not evolve in a steady fashion but generally exhibit significant changes in rates of deformation and exhumation the observed correlation in the timing of tectonism and erosional exhumation provides evidence for links between tectonic and surface processes

the ainsa fold and thrust oblique zone of the central pyrenees kinematics of a curved contractional system from paleomagnetic and structural data this work was funded by the project intectosal cgl2010 21968 c02 01 and by the grup de recerca de geodinamica i analisi de conques 2009sgr1198 secretaria d universitat i recerca del departament d economia i coneixement de la generalitat de catalunya josep poblet acknowledges financial support by research projects geociencias en iberia estudios integrados de topografia y evolucion 4d topo iberia csd2006 041 and desarrollo de fracturas y venas asociadas al plegamiento fraveple cgl2011 23628 funded by spanish ministries

syntectonic fluid flow along thrust faults example of the south pyrenean fold and thrust belt abstract during compressive events deformation in sedimentary basins is mainly accommodated by thrust faulting and related fold growth thrust faults are generally rooted in the basement and may act as conduits or barriers for crustal fluid flow most of recent studies suggest that fluid flow through such discontinuities is not apparent and depends on the structural levels of the thrust within the fold and thrust belt in order to constrain the paleofluid flow through the jaca thrust sheet top basin paleogene southwest pyrenean fold and thrust belt this study compares on different thrust faults located at different structural levels the microstructures in the different fault zones studied are similar and consist of pervasive cleavage calcite shear veins sv1 extension veins ev1 and late dilatation veins ev3 in order to constrain the nature and the source of fluids involved in fluid rock interactions within fault zones a geochemical approach based on oxygen and carbon stable isotope and trace element compositions of calcite from different vein generations and host rocks was adopted the results suggest a high complexity in the paleohydrological behaviors of thrust faults providing evidence for a fluid flow compartmentalization within the basin previous studies in the southern part of the axial zone north of the jaca basin indicates a circulation of deep metamorphic water probably derived from the paleozoic basement along fault zones related to the major basement gavarnie thrust in contrast in northern part of the jaca basin the monte perdido thrust fault is affected by a closed hydrological fluid system involving formation water during its activity the jaca and cotiella thrust faults in turn both located more to the south in the basin are characterized by a composite fluid flow system indeed stable isotope and trace element compositions of the first generations of calcite veins suggest a relatively closed paleohydrological system whereas the late calcite vein generations which are probably associated with the late tectonic activity of the basin support a contribution of both meteoric and marine waters based on these results a schematic fluid flow model is presented this model allows visualization of three main fluid flow compartments along a n s transect

borehole water level response to barometric pressure as an indicator of aquifer vulnerability the response of borehole water levels to barometric pressure is a function of the confining layer and aquifer properties this study aims to use this response as an aid towards quantitative assessment of groundwater vulnerability applying the techniques to the confined semi confined part of the chalk aquifer in east yorkshire uk time series analysis techniques are applied to data collected from twelve monitoring boreholes to characterize and remove components contributing to the borehole water level signal other than barometric pressure such as recharge and earth tides barometric response functions are estimated using the cross spectral deconvolutionaveraging technique performed with up to five overlapping frequency bands a theoretical model was then fitted to the observed barometric response functions in order to obtain estimates of aquifer and confining layer properties derived ranges for pneumatic and hydraulic diffusivities of the confining layer vary over four orders of magnitudes 0 9 to 128 0 m2 day and 10 0 to 5 0 104 m2 day respectively indicating that the aquifer is nowhere purely confined discrepancies between estimates of aquifer transmissivity derived from the barometric response function and pumping tests have been explored using slug tests and results suggest that aquifer model transmissivity are highly sensitive to borehole construction a simple flow model constructed to test the potential impact of confining layer heterogeneity on the barometric response function shows that while high frequencies reflect the immediate vicinity of the borehole low frequencies detect confining layer properties up to some 500 meters distant from the borehole a characteristic time scale is introduced as a function of derived properties of the confining layer and is used as a quantitative measure of the degree of aquifer confinement it is concluded that barometric response functions are sensitive to confining layer properties and thus can provide a useful tool for the assessment of aquifer vulnerability

structural evolution of the cape smith thrust belt and the role of out of sequence faulting in the thickening of mountain belts out of sequence thrusting represents a mechanism capable of heterogeneous internal deformation in thrust belts and was largely responsible for internal thickening in the early proterozoic cape smith belt the south verging thrust belt is marked by a complex history of accretion internal deformation thickening induced metamorphism uplift and erosion an overall chronology for thrust belt evolution is built around the timing of thermal peak metamorphism prethermal peak deformation includes 1 initial piggyback stacking of basalt dominated thrust sheets above a basal decollement localized at the basement cover contact 2 greenschist to amphibolite grade metamorphism accompanied by development of a ductile shear zone at the base of the thrust belt and 3 out of sequence thrusting precipitating the metamorphic thermal peak both above and below these faults synthermal peak out of sequence thrusting was responsible for accretion of autochthonous crystalline basement slices and eventual abandonment of the external basal decollement postthermal peak deformation is characterized by the continued development of out of sequence thrusts which appear to young toward the hinterland north internal thickening by development of flattening cleavages or folding appears to be regionally insignificant when compared to that accomplished by the out of sequence faults this suggests that 1 an eroding and accreting thrust wedge may be able to maintain its critical shape by out of sequence thrusting and 2 this style of internal deformation is favored in belts dominated by relatively strong material e g basalt as in the cape smith belt

neoproterozoic to paleozoic geology of the altai orogen nw china new zircon age data and tectonic evolution abstract we present a synthesis and a new account of the geological and tectonic history of the terranes of the chinese paleozoic altai orogen together with new single zircon ages for granitic and rhyodacitic rocks a central terrane consists of neoproterozoic to silurian amphibolite facies metasedimentary rocks and abundant devonian carboniferous granites the presence of precambrian basement is indicated by sinian fossils our xenocryst ages and published nd mean crustal residence ages of granites felsic arc type lavas on the southern margin of the terrane have a mean 207pb 206pb zircon age of 505 ma reflecting the time of arc volcanism and the presence of xenocysts with ages between 614 and 921 ma suggests derivation by intracrustal melting accordingly we suggest that a cambro ordovician continental magmatic arc was built on the southern margin of the central terrane by northward subduction a low grade ordovician andean type arc with a continental basement is situated above a normal fault on

inversion of a transfer system into lateral ramps an example from the south central pyrenees spain field work in the south central pyrenees suggests that omission contacts i e younger over older rocks occur at the base of the cadi unit cadi thrust and pass laterally into thrusts this change occurs across tear faults which are present in the hangingwall of the cadi thrust sheet and which controlled the deposition of upper cretaceous sediments adraen formation detailed mapping in the contact area between the nogueres and cadi units has shown that the actual thrust geometry in the study area is controlled by preexisting normal and transfer faults which developed in an already compressional context lateral ramps or tear faults develop depending on the angle between the pre existing extensional transfer fault and the thrust transport direction

gravity modelling to assess salt tectonics in the western end of the south pyrenean central unit a new gravity survey almost 900 new sites and more than 4000 sites from previous studies reveals the existence of pyrenean oriented long wavelength residual gravity anomalies ranging from 18 to 28 mgal associated with frontal structures and short wavelength gravity lows up to 16 mgal distributed along an oblique zone in the western sector of the south pyrenean central unit of the spanish pyrenees these clearly correlate with the occurrence of several bodies and diapirs of triassic evaporites and mudstones the subsurface geometry and regional location of these evaporitic bodies is derived from four 2 5d gravity models that tie data from field geology rock density analysis seismic reflection profiles boreholes and our gravity survey gravity constrained cross sections allow us to distinguish between vertically well developed and poorly developed diapirs that belong to the sierras marginales unit and to characterize the relationships between thrusting and diapirism during eocene oligocene time

tectonics and sedimentation in the gulf of corinth and the zakynthos and kefallinia channels western greece abstract single channel seismic reflection profiling data are presented from the gulf of corinth and from the continental margin outside the gulf of patras different tectonic styles are exhibited in the two regions the gulf of corinth is occupied by a complex asymmetrical graben structure with major faults trending nearly perpendicular to the local tectonic zones of the internal hellenides the gulf is interpreted to have formed during the quaternary in response to approximately north south extensional stress the deep floor of the gulf is underlain by a sequence of turbidites up to 1 km thick affected by normal growth faulting that extends up to the sea floor the sea areas inside the ionian islands of zakynthos and kefallinia zakynthos and kefallinia channels occupy a broad structural depression that trends parallel to the local tectonic zones of the external hellenides and is situated on the continental side of the strophades continental margin rise the channels contain local nw se trending structural basins zakynthos and kefallinia basins whose geometry is controlled by reverse faults or thrusts with associated diapirism in triassic evaporites hydra bank is interpreted as a tilted fault block with a diapiric core and its faulted western margin can be traced into the zone of thrusting and diapirism in southeast kefallinia at the boundary between the ionian and pre apulian paxos zones of the external hellinides the zakynthos and kefallinia structural basins are filled with a variety of sediments including prodeltaic deposits in front of the modern delta complex of the acheloos river slumped masses and debris flow deposits and in the zakynthos basin occasional turbidites the boundary separating zones of extensional and compressional focal mechanisms for shallow earthquakes crosses the gulf of patras the inner part of which exhibits wnw ese trending graben tectonics apparently related to the gulf of corinth tectonic province onshore neotectonic studies around the gulf of patras are required in order to understand the nature and cause of the westward tectonic transition from wnw ese graben structures in the gulfs of corinth and patras to nw se oriented zones of subsidence with associated compressional tectonics and diapirism in the zakynthos and kefallinia channels

timing of deformation in overthrust belt and foreland of idaho wyoming and utah a review of the timing and displacement evidence of the major structures of the western wyoming overthrust belt and foreland shows there is a progression in thrust displacement apparent duration of motion and palinspastic position of thrust traces from west to east those toward the west moved farther for an apparently longer period of time and are more widely spaced in their restored positions than those toward the east however average thrust velocities are all on the order of 0 5 0 5 cm yr 0 2 in yr foreland events are in part synchronous with thrust belt events and had an effect on them although dating precision varies widely on major normal faults present evidence does not contradict the generally held view that all normal faults postdate the youngest thrusting

cretaceous tertiary tectonic inversion of the cotiella basin southern pyrenees spain the cotiella nappe includes one of the most important mesozoic basins of the southern pyrenees which was subsequently inverted during the tertiary compression the late cretaceous cotiella basin is here interpreted as the western sector of the cretaceous cotiella boixols basin 100 20 km wide located in the central part of the southern pyrenees the present day complex structure of the cotiella nappe is the result of the inversion process linked to the emplacement of basement thrust sheets of the axial zone in its western sector the cotiella nappe consists of several superimposed thrust sheets with complex geometry becoming simpler towards the east with a single thrust surface and smaller displacements the cotiella boixols basin underwent strong subsidence during the early cretaceous at its eastern sector and its depocentre migrated westward during the late cretaceous the reconstruction of the sedimentary basin to the pre compressional stage shows that during the mesozoic the cotiella boixols basin was located to the south of a basement high which later became the pyrenean axial zone from a balanced cross section it can be inferred that the cotiella north verging extensional system was connected with the north pyrenean rift by means of a 10 km deep horizontal detachment the compressional tertiary detachment within the upper crust was shallower than the extensional detachment and individualised four basement thrust sheets which form the axial zone antiform

evolving alluvial stratigraphy and thrust front development in the west jaca piggyback basin spanish pyrenees in the southwestern pyrenees distinctive alluvial mega sequences correlate with the development of a shallow mountain front thrust structure the pena flexure the flexure evolved during the oligocene to early miocene and is interpreted as a duplex marking the limit of thrust front advance three main depositional facies preserved completely across the pena flexure are described a pre thrust emergence high sinuosity fluvial sequence the c 2300 m thick sheet sandstone facies of the campodarbe formation a syn thrust emergence conglomeratic alluvial fan sequence the c 1100 m thick conglomeratic facies of the bernues formation and a post thrust emergence low sinuosity fluvial sequence the 700 m thick ribbon sandstone facies of the uncastillo formation collectively their continuous exposure across the pena flexure provides a more or less complete record of the sedimentary evolution of a mountain front syn deformational features in the alluvial fan sequence of the bernues formation and marked contrasts in palaeochannel morphology sandstone body geometry and palaeocurrent patterns between the two fluvial sequences are best understood by invoking a strong tectonic control over their deposition an increased rate of vertical sediment accretion was a key process in determining fluvial style the onset of major thrusting led to more rapid basin floor subsidence thereby promoting a change from lateral to vertical accretion as channels responded to the rising base level

architecture of the tectonically influenced sobrarbe deltaic complex in the ainsa basin northern spain abstract the syn tectonic sobrarbe deltaic complex eocene of the ainsa basin spanish pyrenees is confined by lateral thrust ramps and influenced by intra basinal growth anticlines six facies associations have been distinguished within the deltaic complex i slope marls and turbidite sandstones ii distal delta front silty and bioturbated sandstones iii proximal delta front and delta plain deposits tidal inlet tidal flat mouth bar bay distributary channel and floodplain environments iv biogenic deposits at flooding surfaces v collapse zone sediments and vi nummulite dominated shallow marine carbonates the deltaic complex comprises four composite sequences which each contain a number of minor sequences of the genetic maximum flooding surface bounded type regressive unconformities and their correlative surfaces separate the composite sequences cs and each cs can be divided into lowstand transgressive and highstand components at the base the comaron cs is a wnw prograding deltaic complex containing six minor sequences characterized by basinward stepping sandstone wedges separated by transgressive mudstones double regressive unconformities are often associated with these sandstone wedges proximally in the basin growth of the intra basinal arcusa anticline caused gentle folding of the comaron cs and syn growth strata at the base of the overlying las gorgas cs contain a prominent forced regressive sandstone wedge the las gorgas sandbody and display thinning of bedsets onto the crest of the anticline moreover it can be demonstrated that relative sea level rise took place in the growth synclines at the same time as a fall in relative sea level occurred on the growth anticlines the tectonic deformation caused a shift in the direction of deltaic progradation towards the north northwest as demonstrated by the well developed clinoforms in the highstand sequence set of the las gorgas cs a second phase of tectonic activity this time triggering large scale collapse of the delta front occurred at the transition between the las gorgas and barranco el solano cs tilting of the basin floor led to the development of coeval transgressive and regressive strata separated by a fulcrum line of zero net vertical movement of the shoreline in the post tilt phase reduced sediment supply and accelerated subsidence led to widespread transgression and a change from clastic to carbonate dominated sedimentation this phase was terminated by a gradual increase in sediment supply causing progradation of a mixed clastic carbonate system dominated by large nummulite banks and bioturbated shoreface marls and sandstones finally a pronounced fall in relative sea level associated with the transition to the buil cs triggered slope instabilities and eventually established fluvial conditions all over the study area with the exception of the anticline crests the relatively high rate of tectonic subsidence in the study area suppressed relative sea level falls resulting in development of discontinuous lowstand strata and bounding surfaces the segmented nature of many regressive unconformities may be related to incremental growth of thrust related structures and each segment is separated from neighbouring segments by gaps of limited vertical and lateral displacement precursors of progressive unconformities are seen in the upper proximal part of the comaron cs by downdip fanning and updip convergence of minor sequences these differentially tilted stratal units provide reliable indicators of syn sedimentary tectonism

the terminology of structures in thrust belts abstract a review of structures and geometric relationships recognized in thrust belts is presented a thrust is defined as any contractional fault a corollary being that thrusts must cut up section in their transport direction flats are those portions of a thrust surface which were parallel to an arbitrary datum surface at the time of displacement and ramps are those portions of thrusts which cut across datum surfaces ramps are classified on the basis of their orientation relative to the thrust transport direction and whether they are cut offs in the hangingwall or footwall of the thrust lateral variations in the form of staircase trajectories are joined by oblique or lateral ramps which have a component of strike slip movement an array of thrusts which diverge in their transport direction may form by either of two propagation models these are termed piggy back propagation which is foreland directed and overstep propagation which is opposed to the thrust transport direction an array of thrust surfaces is termed an imbricate stack and should these surfaces anastamose upwards a duplex will result the fault bounded blocks are termed horses a duplex is bounded by a higher roof thrust and a lower floor thrust the intersection of any two thrust planes is termed a branch line thrusts can be classified on the basis of their relationship to asymmetric fold limbs which they cut a further classification arises from whether a particular thrust lies in the hangingwall or footwall of another one the movement of thrust sheets over corrugated surfaces or the local development of thrust structures beneath will fold higher thrust sheets these folds are termed culminations and their limbs are termed culmination walls accommodation of this folding may require movement on surfaces within the hangingwall of the active thrust these accommodation surfaces are termed hangingwall detachments and they need not root down into the active thrust this category of detachment includes dip slip hangingwall drop faults which are developed by differential uplift of duplex roofs and out of the syncline thrusts which develop from overtightened fold hinges back thrusts as well as forming as hangingwall detachments may also form due to layer parallel shortening above a sticking thrust or by rotation of the hangingwall above a ramp

growth of the south pyrenean orogenic wedge a six step reconstruction of the south pyrenean foreland fold and thrust belt in spain delineates the topographic slope basal dtcollement angie internal deformation and thrust front advance from the early eocene until the end of contractional deformation in the late oligocene style of thrust front advance dip of the basal dtcollement slope of the upper surface and internal deformation are decoupled and not simply related internal deformation increased decreased and maintained surface slope angle at different stages from the onset to the cessation of deformation the basal dtcollement angle decreased overall suggesting translation of the thrust belt onto stronger crust with time taper angle of the pyrenean thrust wedge was fundamentally controlled by the flexural rigidity of the lower plate the relative rate of creation of structural relief in the rear versus the front of the wedge the extent of deposition of eroded material within the deforming wedge and the taper of the pretectonic stratigraphic wedge

thrust tectonics in the south central pyrenees abstract surface structural data and published stratigraphies are combined to construct two balanced and restored sections through the nogueras zone of the south central pyrenees the allochthonous nogueras zone units are interpreted as the foreland dipping margin of a major antiformal stack in the palaeozoic rocks of the pyrenean axial zone their structural evolution is summarized in a hangingwall sequence diagram this reinterpretation of the nogueras zone is incorporated into a new n s balanced and restored section from the centre of the pyrenean axial zone to the ebro basin a classical rocky mountains piggy back thrust model is employed and the resulting section is a significant departure from those previously published it is argued that gravity gliding has never been an important mechanism in the alpine pyrenees section restoration casts doubt on the correlation of the surface expression of the north pyrenean fault and the seismically detected moho step beneath it

a new age model for the middle eocene deep marine ainsa basin spanish pyrenees abstract the middle eocene ainsa basin spanish pyrenees comprises 4 km of deep marine sedimentary rocks belonging to the hecho group despite extensive study of these exemplary deep marine clastic successions there has been no comprehensive chronostratigraphic framework that provides primary ages for the submarine fan and related deposits here we present a new composite basin stratigraphy based upon biostratigraphic analyses of the upper hecho group submarine fan and interfan deposits calcareous nannofossil data suggest that deposition of the gerbe through to guaso systems occurred during biozones np14 16 42 6 and 48 9 ma based on our age model additional biostratigraphic ages from the lower hecho group suggest that the entire hecho group no older than biozone np13 51 ma the improved chronostratigraphic control enables correlations between submarine canyons and submarine fans of the ainsa and jaca basins to be assessed our new age model provides a means of comparison of stratigraphic events with regional sections allowing a better understanding of the lateral and temporal evolution of these depositional systems from source to sink

strains and folds within thrust sheets an analysis of the heilam sheet northwest scotland abstract the changes of shape and orientation of fossil worm burrows have been used to carry out a detailed strain analysis of the heilam thrust sheet in the moine thrust zone northwest scotland the strains have been factorised into components of layer parallel shear 1 layer normal shear 2 and layer parallel shortening or elongation variations in the 1 shear are largely lithologically controlled some strain is due to flexural processes as the thrusts and overlying beds change dip over thrust ramps or are tightened by later deformation while there may also be a component of drag which increases towards the overlying thrust this predating the shear due to flexure a contoured map of the values suggests that major folds within the thrust sheet developed as a result of stick or drag on the floor thrust prior to ramp climb this led to differential movement in the transport direction causing layer parallel shortening accompanied or followed by buckling of the layers a map showing layer normal shear strains 2 suggests that the heilam sheet forms a major surge zone the central part having moved further wnw than the northern and southern parts this has led to components of lateral shear along parts of the sheet especially in the north producing curvature of the imbricate faults

rotational velocity for oblique structures boltana anticline southern pyrenees abstract despite the large amount of paleomagnetic and structural studies on fold and thrust belts many key questions about rotational kinematics remain unsolved pace of rotation subsequent accommodation of the hanging wall etc excellent exposure conditions and syntectonic sedimentation related to the growth of oblique structures in the southern pyrenees allow an accurate investigation that sheds light on the rotational kinematics of thrust systems fifty nine paleomagnetic sites 819 specimens are homogeneously distributed in both limbs along the marine and continental sedimentary sequences contemporary with the uplift of the boltana anticline and its post folding evolution they indicate a clockwise rotation of about 52 during ypresian to priabonian times primary stable 350 580 c pre folding magnetization in the eocene rocks is attested by a positive fold test and the antipodality proof with magnetite and iron sulphide traces as magnetic carriers rotation velocity fits a logarithmic model and shows a low rate during the ilerdian middle lutetian interval ca 1 m y and much higher up to 10 m y in the late lutetian priabonian interval most of the clockwise rotation of the boltana anticline can therefore be constrained within the 42 35 m a interval partially post folding indicating a period of strong differential displacement in the southern pyrenean zone probably related to the emplacement of the underlying external sierras thrust sheets tozal alcanadre

post emplacement extension within a thrust sheet from the central pyrenees secondary faults and related veins in a small thrust sheet the pic de port vieux thrust sheet in the footwall of the gavarnie thrust in the central pyrenees are used to infer the deformation sequence that accompanied its emplacement initial deformation was characterized by distributed bedding parallel simple shear this was superseded by localized deformation involving arrays of extensional faults the first faults to form were x shears and were succeeded first by conjugate faults x x9 shears and then arrays of r shears that locally cut the thrust i e developed subsequent to its emplacement extension veins are used to infer the orientation of the ambient stress system during the deformation sequence a forward rotation of the stress sytem towards the vertical was associated with the x and x x9 shears and is considered to reflect loading of the 4 km thick overlying gavarnie thrust sheet a later backward rotation of the stress system then occurred returning 1 to 45 obliquity to the pic de port vieux thrust and was associated with the r shear development this later event produced extensional shearing of the thrust sheet and is equated with a proposed episode of spreading gliding within the overlying thrust pile a model for this spreading gliding relates it to the active tectonics of the developing south pyrenean thrust belt

climate forcing of fine grained deep marine systems in an active tectonic setting middle eocene ainsa basin spanish pyrenees abstract a multi proxy approach to understand environmental change in deep time was undertaken on about 150 m of core from a 230 m long middle eocene core from the ainsa basin spanish pyrenees representing deep marine siliciclastic sediments using detailed sedimentary logging high resolution multi element xrf geochemistry total organic carbon and stable carbon isotopes the well a6 was drilled as part of an industry university consortium through siltstones fine very fine grained sandstone turbidites and hemipelagic structureless mudstones that were deposited as overbank and off axis deposits from a sandy submarine fan and interfan deposits for comparative mineralogy between the sandstone turbidites and siltstones scanning electron microscopy sem and x ray diffraction xrd were undertaken on selected samples the sandstone turbidites show enrichment of detrital elements such as si zr and ti that can be linked to greater quartz and heavy mineral content compared with adjacent siltstones structureless hemipelagic mudstones comprise mainly clay minerals and carbonate we interpret the sandstone turbidites as from hyperpycnal flows during high river sediment discharge whilst hemipelagic mudstones resulted from the suspension fall out of hypopycnal flows cyclostratigraphic analysis of the core reveals milankovitch cyclicity at frequencies of 0 03 cycles m short eccentricity 0 09 cycles m obliquity 0 15 cycles m precession couplet and 0 19 cycles m precession couplet orbital parameters appear to have controlled the cyclic delivery of coarser grained sediment by turbidity currents two equally plausible depositional models both as milankovitch driven can explain the cyclical changes in the deep marine sediments 1 climatic cycles with humid periods of enhanced chemical weathering increased storminess and greater riverine run off leading to high sediment flux to the deep basin as sandstone turbidites 2 climatic cycles with cooler conditions linked to high frequency small scale eustatic sea level fluctuations with lowstand shelf edge delta progradation resulting in greater volumes of coarse detrital sediment to the seafloor by hyperpycnal flows this study provides an insight into the likely depositional effects of orbitally induced climate change on the nature and delivery of terrigenous sediment into deep marine environments

constraints on the age of movement of the montsech and cotiella thrusts south central pyrenees spain palaeocene to oligocene thrusting in the pyrenees was synchronous with the development of the south pyrenean foreland basin collectively the tremp graus ainsa and jaca basins sedimentological and stratigraphical evidence from the foreland basin is used to constrain the age of movement of the montsech cotiella and external sierras thrusts movement on the emergent imbricate fan at the montsech front began in the early eocene illerdian during an early phase of thrusting that detached in the triassic evaporites in that region this phase of thrusting defined the tremp graus basin as a thrust sheet top basin following the early thrusting cuisian age tectonics in the tremp graus and ainsa basins was dominated by minor normal fault movements during flexural subsidence associated with thrust sheet loading growth of the boltana anticline to the west of the ainsa basin indicates that the ainsa basin had become detached as a thrust sheet top basin in the lutetian movement on the pena montanesa thrust and by inference on the cotiella thrust began in post lutetian times during the propagation of lower thrusts that involved pre triassic variscan basement thrusting in the external sierras caused folding and faulting of oligocene sediments indicating the continued southward propagation of basement involved thrusts in the upper eocene and oligocene many faults in the southern pyrenees have evidence of early normal and later reverse senses of movement indicating reactivation of normal faults during thrusting

structural and stratigraphic evolution of the west jaca thrust top basin spanish pyrenees thrust top basins form and fill during their detachment from the foreland margin by active thrust sheets strike normal n s sections from the west jaca thrust top basin southwest pyrenees to the ebro basin show that the pena flexure the local expression of the thrust front can be interpreted as a passive roof duplex the duplex accommodated up to 7 km bulk shortening at the tip of the gavarnie thrust sheet unravelling the timing of uplift and sedimentation in the west jaca basin has revealed that development of the pena flexure represented the climactic phase of deformation lateral e w diachroneity of gross stratigraphy and thrust emergence throughout the southwest pyrenees suggests that the thrust front propagated both toward the foreland and westward parallel to the orogen axis

controls on stratigraphic architecture in contemporaneous delta systems from the eocene roda sandstone tremp graus basin northern spain abstract the eocene roda sandstone of the spanish pyrenees is comprised of two coeval coarse grained delta systems which share correlatable surfaces but show a markedly different internal facies architecture the two deltas developed contemporaneously with the differences in internal architecture attributed to basin morphology and the role of two distinct sediment sources while the correlatability of the larger scale packages indicates an external allocyclic control as such the roda sandstone provides the possibility to address the relative roles of different parameters known to interact and control stratal architecture the roda sandstone crops out at the ne margin of the tremp graus basin a piggyback basin initiated in palaeogene times in the foreland of the southern pyrenees the study area 30 km2 is composed of the well understood and well exposed parts of the roda sandstone cropping out along the isabena valley and the less worked and less exposed outcrops to the north along barranco de ricans and barranco de codoneras data for this study include a combination of conventional sedimentology data coupled with analyses of 3d virtual outcrop models based on these methods 8 different facies associations have been distinguished their distribution suggests that the roda sandstone is composed of two different but coeval delta systems and their linked subenvironments a gilbert type delta outcropping along isabena valley and a shoal water fan delta along barranco de ricans and barranco de codoneras along the isabena valley the outcrops of the gilbert type deltaic system are composed of at least 6 distinct packages roda u z characterized by texturally mature delta front sandstones separated by offshore mudstones the stacked basinward stepping architecture of the roda u y units here represents a minimum of 3 major phases of sw directed progradation capped by hardground horizons formed during the subsequent flooding phases tidally modified delta front deposits found in the distal exposures of roda y represent the redistribution of the delta toeset by w nw directed ebb tidal currents active during advanced stages of progradation of the gilbert type delta the more gentle sloping shoal water fan delta system found in barranco de ricans and barranco de codoneras is characterized by progradational to aggradational stacking of texturally immature wave modified mouth bar sandstone packages separated by offshore mudstones the zone of interference between the gilbert type and shoal water delta is dominated by wave reworked sediments deposited as shoreface barrier and spit deposits biostratigraphic dating suggests that the roda sandstone was deposited during a 3rd order relative sea level cycle as a shelf margin systems tract however the stacking of the individual roda u y units demarcated by offshore mudstones both within the gilbert type and the shoal water deltaic systems suggest that 4th order fluctuations occurred these 4th order units are physically correlatable between the two deltaic systems which implies that both deltas responded synchronously to a combination of regional subsidence and eustatic sea level fluctuations the differing internal architecture such as the steeply dipping textural mature foreset beds of the gilbert type delta versus the more gentle sloping textural immature mouth bars of the shoal water fan delta are controlled by different hinterland characteristics and intrabasinal topography

multi fluid flow record during episodic mode i opening a microstructural and sims study cotiella thrust fault pyrenees abstract syntectonic veins commonly have been used to assess the composition and source of fluids involved in fault zone activity such veins also provide information on the ambient stress conditions during deformation and mineralization based on bulk sampling and bulk o and c isotope analysis combined with fluid inclusion microthermometry many studies have demonstrated that syntectonic veins provide snapshots of fluid composition and stress conditions over the course of fault history this is widely acknowledged for mode i extension veins that develop in the damage zones of faults however an important and unanswered question is the extent to which such veins record a more detailed fault history at the micron scale in this study we present new detailed in situ micron scale 18 o data measured using secondary ion mass spectrometry sims combined with detailed fluid inclusion microthermometry and 47 clumped isotope thermometry to document the fluid and temperature conditions during mode i vein growth related to deformation along the cotiella thrust fault pyrenees all the studied veins show three distinct episodes of vein opening recording a complex history of varying fluid composition and temperature results show that the studied fault portion passed from a hydrological rock buffered system in which formation waters were in isotopic equilibrium with the host sediments to a fluid buffered system involving meteoric water however such information is only achievable at the micron scale using secondary ion mass spectrometry this study demonstrates the potential of these new micro beam techniques for investigating fault behavior in more detail than previously available particularly with respect to the nature of the fluids involved and the p t conditions extant during fault activity

role of lateral thickness variations on the development of oblique structures at the western end of the south pyrenean central unit abstract the montsec unit is one of the most important detached south verging nappes within the south pyrenean central unit spcu southern pyrenees a n s cross section of its western sector based on seismic reflection profiles shows a hangingwall ramp geometry in mesozoic strata overlain by a syntectonic series of lower eocene sediments with growth geometry the geometry of growth strata constrains the age of its movement between the paleocene and the middle eocene the geometry of the western oblique ramp of the south pyrenean central unit is defined by a series of n s folds in some cases associated with underlying west verging thrusts as indicated by seismic reflection profiles and field data in this paper we propose that the geometry of the thrust wedge of mesozoic units progressively thinning from east to west strongly contributed to constrain the location and geometry of the western termination of the montsec thrust the hypothesis proposed is checked by a series of experimental wedges developed in a sandpack with lateral and three dimensional thickness variations oblique structures form as thrusting progresses at the tip of the sand wedge

out of sequence thrusts out of sequence thrusts oost are those thrusts which do not obey the foreland propagating or in sequence deformation style they include both isolated thrusts which develop hindward of the thrust front and sequences of break back thrusts which propagate from the foreland to the hinterland two end members of a series of oost types are recognized 1 older in sequence thrusts which are reactivated along their entire length and 2 completely new thrusts which propagate through already deformed thrust sheets between the two end members are thrusts composed partially of reactivated in sequence thrust sequences and partially of new entirely out of sequence segments oosts can be initiated for a variety of reasons including 1 keeping the orogenic wedge at critical taper 2 break back sequences from the suture zone in the overriding plate 3 ramping to overcome a sticking point which inhibits in sequence thrust propagation and 4 during simultaneous displacement along two stacked thrusts culminations which bow up segment of the upper thrust may be chopped through to permit continued displacement on the upper thrust many different types of thrust behavior including gravity sliding plucking and derivation of isolated horses from ramps may mimic some of the characteristics of oosts consequently it may be difficult to conclusively prove an oost origin for a complex thrust geometry

restoring paleomagnetic data in complex superposed folding settings the boltana anticline southern pyrenees abstract complex kinematic scenarios in fold and thrust belts often produce superposed and non coaxial folding interpretation of primary linear indicators must be based on a careful restoration to the undeformed stage following the reverse order of the deformation events therefore sequential restoration to the ancient coordinate system is of key importance to obtain reliable kinematic interpretations using paleomagnetic data in this paper a new paleomagnetic study in the western flank of the boltana anticline southern pyrenees illustrates a case study of a complex tectonic setting having superposed non coaxial folds the first stage of nw se folding linked to the oblique boltana anticline took place during lutetian times the second stage was linked to the vertical axis rotation and placed the boltana anticline in its present day n s configuration our data support a long lasting lutetian to priabonian period with main rotational activity during the bartonian priabonian other authors support a var coeval with anticlinal growth the third stage resulted in southwards tilting related to the emplacement of the n120e striking guarga basement thrust oligocene early miocene based on this deformational history a sequential restoration was applied and compared with the classic bedding correction at the site scale single bedding correction gives errors ranging between 31 and 31 in the estimation of vertical axis rotations at the locality scale in sites grouped in three folds from w to e arbella planillo and san felizes the bedding corrected data display rotation values in accordance with those found in the ainsa basin by other authors sequential restoration based on the afore mentioned evolution in three steps improves both some locality means and the internal consistency of the data therefore reasonably constrained sequential restoration becomes essential to reconstruct the actual history of superposed folding areas

fossiliferous intervals and sequence boundaries in shallow marine fan deltaic deposits early eocene southern pyrenees spain abstract carbonate rich fossiliferous intervals are commonly intercalated in shallow marine siliciclastic successions in a sequence stratigraphic approach to basin modelling such layers tend to be used for interpretation in terms of sea level changes as reflecting maximum flooding events however in this paper it will be demonstrated that such interpretation may not be generally applicable during the eocene a fan delta system developed in the tectonically active tremp graus basin a southern pyrenean foreland basin in spain fan delta lobes prograded rapidly during periods of active sediment supply fossiliferous calcareous intervals were formed during local abandonment of individual fan delta lobes and distributary channel mouthbars and occur on top of the depositional lobes on their foreslopes and on their more distal toes calcareous intervals originated as a consequence of the local development of an in situ macrofauna association during periods of clastic abandonment the macrofauna typically reflects environmental conditions ranging from shallow high energy conditions to somewhat deeper water and more tranquil conditions two laterally equivalent faunal associations dominate a high energy and shallow water fauna typified by mytilus spondylus cardiacea and a low energy and somewhat deeper water fauna characterized by turritella corbulidae each calcareous horizon is related to a pause in clastic sedimentation as a result of autocyclic lateral shifting of the local depocentre differences in faunal associations and substrate conditions are related to water depth which is largely defined by clastic sediment accumulation although each calcareous interval was caused by local starvation of clastic sediment supply the macrofauna associated with abandonment surfaces indicates that relatively little time was involved in their development suggesting that such surfaces do not mark regional discontinuities in a sequence stratigraphic frame the in situ macrofauna associations can be used for estimating the significance of hardground like layers

a structural interpretation of a section of the gavarnie nappe and its implications for pyrenean geology abstract the gavarnie nappe is a feature of the tertiary pyrenean orogen and is shown to consist of at least two thrust sheets of palaeozoic rocks which are overlain by a southward dipping sequence of cretaceous and eocene sediments showing folded thrust structures the gavarnie nappe covers a basement and mesozoic cover rock sequence which is exposed in the tectonic windows of la larri and the troumouse cirque here previously unrecognized thrusts involving basement were responsible for folding the overlying gavarnie nappe these basement involved thrusts climb up section westwards giving a westward lowering of the gavarnie thrust along strike the structural evolution of the gavarnie nappe in a region extending from heas in france to the valle de pineta in spain can be explained in terms of a piggy back thrusting sequence on a regional scale thrust tectonic models may be used to explain the double vergence of the pyrenean chain where early southward directed thrusting was responsible for structures in the south pyrenean zone a later northward directed back thrusting event or rotation of southward directed thrust sheets by the stacking of lower thrust horses can explain the steepness of structures in the axial zone and the northward verging north pyrenean thrust zone both models suggest that prior to the pyrenean orogeny some of the hercynian structures in the axial zone were flatter lying and have been rotated to their present steepness during the pyrenean orogeny

sea level fluctuations and the geometric variability of tide dominated sandbodies abstract this paper presents examples of various large tidal sandbodies from the eocene roda sandstone in the southern pyrenees and the late pleistocene and early holocene in the east china sea an attempt is made to summarize the geometric variability of these large tidal sandbodies in relation to the sediment supply and tidal discharge of the depositional system transverse sand bars were developed in low sinuosity high gradient channels with high influxes of coarse sediments and water from fluvial systems tidal point bars were formed in meandering low gradient estuarine channel where tidal influence was stronger and sediment was finer than those of the transverse sand bar a tidal delta complex was built up at the estuary mouth with an abundant sediment supply and an increased tidal discharge tidal sand ridges were formed when relict fluvial or deltaic sands were eroded and reworked by strong tidal currents during subsequent sea level rise since the sediment supply and the tidal discharge of the depositional system were closely related to the eustatic sea level change and basin subsidence i e the relative sea level change special attention will be given to the relationship between geometric variability of tidal sandbodies and the sequence stratigraphic framework in which various sandbodies occurred three orders of eustatic sea level fluctuations can be recognized the third order eustatic sea level cycle together with basin subsidence controlled the development of systems tracts and the occurrence of different tidal sandbodies such as estuary and tidal flat facies during the late stage of a lsw systems tract type 1 sequence or a sm systems tract type 2 sequence tidal point bar facies tidal delta facies or tidal sand ridge facies during a tr systems tract estuary facies during an early hs systems tract and fluvial sand bar facies in a late hs systems tract and the early stage of a sm or lsw systems tract there are also the fourth order and fifth order eustatic fluctuations which are superimposed on the third order eustatic changes and have important control on the build up abandonment and preservation of composite and single tidal sandbodies respectively since the deposition of tidal sandbodies is very sensitive to eustatic sea level changes recognition of various tidal sandbodies is important in sequence stratigraphy analyses of sedimentary basins and in the facies prediction of clastic sediments in basin modelling

3d structure and evolution of an oblique system of relaying folds the ainsa basin spanish pyrenees the structure of the eocene ainsa basin is dominated by kilometre scale thrusts and folds that have trends at c 70 to that of the main pyrenean structures late uplift and erosion provide excellent exposure of this fold and thrust system and its growth strata field observations integrated with 2d seismic and well data support the 3d reconstructions presented in this paper structural reconstructions of pre and syn growth geometries contribute substantial improvements to the understanding of the structure of the area and provide a unique insight into the timing of pyrenean structures this study demonstrates that oblique features in the ainsa basin can be grouped into two main systems the la fueba thrust system an oblique lateral ramp to one of the main pyrenean thrusts and the kilometre scale folds of the sobrabe system a set of anticlines that grew as part of a relaying system of folds in this study we propose a chronology of deformation based on the geometry of the basin fill which has been used to frame the general tectonosedimentary evolution of the ainsa basin the relative timing of structures indicates that the la fueba structures predate the sobrarbe structures which originated as orogen parallel structures and obliquity developed during the growth of these structures through clockwise vertical axis rotation

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

thrust tectonics in the north pyrenees abstract balanced and restored cross sections through the central and eastern pyrenees constructed using both surface and borehole data demonstrate the presence of c 18km of shortening above a flat lying n directed alpine decollement surface hangingwall diagrams show how the north pyrenean satellite massifs are culminations within this thrust system pre thrusting structures such as subhorizontal stretching lineations in the north pyrenean fault zone became rotated above these culminations as the north pyrenean fault was cut by alpine thrusts stratigraphic evidence demonstrates that n directed thrust movements occurred between mid eocene and oligocene time and this is similar to the age of major s directed thrust movements on the south side of the axial zone the n directed thrust system probably originated as a series of backthrusts to the dominant s directed structures

discussion on palaeostresses associated with thrust sheet emplacement and related folding in the southern central pyrenees huesca spain journal vol 152 1995 353 356 journal vol 152 1995 353 356 j p turner p l hancock write we congratulate martinez pena casas sainz and millan garrido 1995 on their palaeostress analysis of a complex suite of mesostructures contained in several south pyrenean thrust sheets we agree that in spite of the difficulty in interpreting the multi phase deformation of thrust belts analysis of structures from which palaeostress may be inferred yields useful information not apparent from a macro structural study like martinez pena et al 1995 we also found that the folded oligo miocene molassic sedimentary rocks of the jaca thrust top basin contain remarkably few faults indeed explaining how a near surface structural unit has travelled 30 km or more over such an irregular tectonic topography yet without being faulted is a challenging structural question however we are suprised that martinez pena et al 1995 found in their palaeostress results from the cretaceous and palaeocene carbonates to the north of the molasse basin that there are no great differences between stress tensors found in the hanging wall and the footwall of thrusts our experience turner hancock 1989 in that part of the jaca basin contiguous with and immediately to the west of their study area is that the assemblages of small scale brittle structures in the immediate within 1 3 km hanging walls and footwalls of thrusts are distinctively different recording locally contrasting stress regimes in particular our study showed that the immediate footwalls of thrusts experienced extension parallel to the strike of thrusts before they underwent extension normal to the strike of thrusts