silica diagenesis in eocene shallow water platform carbonates southern pyrenees spectacularly developed lower eocene chert in the corones platform carbonates of the spanish pyrenees is concentrated within a restricted brackish water laminated ostracod rich facies which also contains abundant sponge spicules the chert occurs as nodular bedded and mottled varieties and four petrographic types of quartz are developed microquartz length fast lf chalcedony megaquartz and microspheres 18o values of chert range from 29 6 to 30 9 smow which correspond to a broad isotope rank common for biogenic and diagenetic replacement cherts calcian dolomite crystals with high fe and na are disseminated within the microquartz and lf chalcedony but are absent from the megaquartz and host carbonate the chert is closely associated with desiccation cracks and with interstratal dewatering structures load casts are silicified and laminae rich in sponge spicules are convoluted early cracks related to dewatering are filled by microquartz and quartz cements ostracod shells within chert are locally fractured those in the host carbonate are commonly flattened late fractures are filled by lf chalcedony and megaquartz there is much evidence for the dissolution of sponge spicules and their calcitization in the carbonate host rock silica for the corones cherts was derived from sponges during early diagenesis and shallow burial early mechanical compaction and sediment dewatering played a major role in sponge spicule dissolution migration of silica rich fluids and the consequent precipitation of chert quartz cements continued to be precipitated into the burial environment

the dominant intraseasonal mode of intraseasonal south asian summer monsoon from june through september the intraseasonal variability of the asian summer monsoon is dominated by the so called monsoon intraseasonal oscillation miso this paper provides a comprehensive description of the miso based on outgoing longwave radiation olr data the miso is characterized by alternating active periods in which the primary rain area of the asian summer monsoon that stretches from the northern arabian sea east southeastward almost all the way to the northwest pacific intertropical convergence zone is relatively intense and break periods in which the heaviest rainfall shifts from south asia to the central and eastern equatorial indian ocean the miso is attended by well defined but weak sea surface temperature sst perturbations whose phase is indicative of a negative feedback upon the atmospheric perturbations meridional profile of variables on the various regression maps shown in this paper averaged along a set of tilted axes parallel to the west northwest to east southeast wnw ese sloping lines in empirical orthogonal function 1 of olr have been made and it is found that the strongest westerly 850 hpa wind anomalies are located two grid points 5 of latitude to the south of the reference latitude at the 150 hpa level the meridional profile of divergence is closely aligned with the olr profile sst profile is lowest at approximately 2 5 of latitude to the south of the minimum olr and 2 5 to the north of the strongest westerly 850 hpa wind anomalies the sea level pressure profiles and the midlower tropospheric geopotential height profiles are almost in phase it is observed that in most years there are two three bands of intensified and suppressed rainfall that cross the reference line from south to north northward propagating at the interval of 30 60 days over south asia the degree of correspondence between the miso and active and break spells of the indian summer monsoon rainfall is also documented

integrated gravity and seismic interpretation of duplex structures and imbricate thrust systems in the southeastern pyrenees ne spain abstract combined surface subsurface and gravity data were used to determine the deep structure of the thrust belt in the southeastern pyrenees the ripolles and la garrotxa areas are part of the cardona oil exploration permit hydrocarbons pervade the concession with numerous oil seeps abandoned oil wells and gas or condensate are in these two wells associated with the overthrust belt the source rocks the armancies formation upper cuisian lower lutetian consist of alternating layers of organic rich shales and thin limestones this formation outcrops in the cadi thrust sheet in the ripolles area the cadi unit overlies the serrat unit with a hanging wall ramp geometry as deduced from the serrat 1 well the structure of the garrotxa area is more complex it consists of a duplex structure folded by antiformal stack structures with basement rocks in their cores the northern boundary of these antiformal stacks represents an inversion of pre existent extensional faults the basement rocks involved in the structure represent shortcuts formed in the footwall of the extensional faults a negative anomaly is shown in these antiformal stacks these anomalies are interpreted as a combination of salt accumulation evaporites and sedimentary rocks under the antiformal stacks in the serrat 1 well the serrat unit is made up of a thick middle eocene evaporitic sequence but the gravity and seismic data evidence the presence of non evaporitic sedimentary rocks in the northern part of the serrat unit these sediments correspond to the footwall of the cadi series so the probable existence of the armancies formation in the serrat unit is a very good target for oil prospecting the existence of the previous extensional faults only in the garrotxa area determines the difference in the deep structure between the ripolles and garrotxa areas

synchronous detachment folds and coeval sedimentation in the prepyrenean external sierras spain a case study for a tectonic origin of sequences and systems tracts this paper reports on the structural and sedimentary evolution of the middle to late eocene of the prepyrenean external sierras southern pyrenees spain the initiation duration and kinematics of a set of growth structures that developed in a shallow marine depositional setting is documented the detailed analysis of the syntectonic marine sediments not only confirms the already known east to west progression of deformation but also reveals the continued growth of the early formed structures as later ones propagate towards the foreland the sedimentary units coevally deposited with these growth structures are arranged in four depositional sequences their boundaries correspond to flooding surfaces which grade basinwards into correlative conformities they are also indicated by the presence of both angular unconformities and onlap geometries each depositional sequence generally consists of two systems tracts the lower one or transgressive systems tract is formed by up to 400 m of azoic marls deposited in outer ramp areas the upper one or highstand systems tract mainly consists of shallow siliciclastic and carbonate facies up to 200 m thick deposited in middle to inner ramp areas these depositional sequences are interpreted to be controlled by regional tectonic pulses an increase of tectonic activity resulted in the flooding of the basin and in the subsequent deposition of a thick succession of nearly azoic blue marls i e transgressive systems tract the overlying highstand systems tract developed following periods of diminished tectonism with the consequent growth and progradation of shallow carbonate platform facies

formation of fold and thrust belts on venus by thick skinned deformation on venus fold and thrust belts which accommodate large scale horizontal crustal convergence are often located at the margins of kilometre high plateaux1 5 such mountain belts typically hundreds of kilometres long and tens to hundreds of kilometres wide surround the lakshmi planum plateau in the ishtar terra highland fig 1 in explaining the origin of fold and thrust belts it is important to understand the relative importance of thick skinned deformation of the whole lithosphere and thin skinned large scale overthrusting of near surface layers previous quantitative analyses of mountain belts on venus have been restricted to thin skinned models6 8 but this style of deformation does not account for the pronounced topographic highs at the plateau edge we propose that the long wavelength topography of these venusian fold and thrust belts is more readily explained by horizontal shortening of a laterally heterogeneous lithosphere in this thick skinned model deformation within the mechanically strong outer layer of venus controls mountain building our results suggest that lateral variations in either the thermal or mechanical structure of the interior provide a mechanism for focusing deformation due to convergent global scale forces on venus

reconstructing recent landslide activity in relation to rainfall in the llobregat river basin eastern pyrenees spain abstract a chronology of recent landslides in the upper basin of the llobregat river eastern pyrenees has been reconstructed from technical reports field reconnaissance and dendrogeomorphological analysis the precipitation conditions responsible for triggering and reactivating landslides have been deduced by analysis of rainfall records from two rain gauges located in the area two different rainfall patterns relate to landslide occurrence i without antecedent rainfall high intensity and short duration rains trigger mostly debris flows and shallow slides developed in colluvium and weathered rocks a rainfall threshold of around 190 mm in 24 h initiates failures whereas more than 300 mm in 24 48 h are needed to cause widespread shallow landsliding ii with antecedent rain moderate intensity precipitation of at least 40 mm in 24 h reactivates mudslides and both rotational and translational slides affecting clayey and silty clayey formations in this case several weeks and 200 mm of precipitation are needed to cause landslide reactivation dendrochronological analysis shows that landslide activity in the eastern pyrenees was relatively low between 1926 and 1959 but has since increased significantly with reactivation now occurring about every 3 years

extensional inheritance and surface processes as controlling factors of mountain belt structure surface processes and inherited structures are widely regarded as factors that strongly influence the evolution of mountain belts the first order effects of these parameters have been studied extensively throughout the last decades but their relative importance remains notoriously difficult to assess and document we use lithospheric scale plane strain thermomechanical model experiments to study the effects of surface processes and extensional inheritance on the internal structure of contractional orogens and their foreland basins extensional inheritance is modeled explicitly by forward modeling the formation of a rift basin before reversing the velocity boundary conditions to model its inversion surface processes are modeled through the combination of a simple sedimentation algorithm where all negative topography is filled up to a prescribed reference level and an elevation dependent erosion model our results show that 1 extensional inheritance facilitates the propagation of basement deformation in the retro wedge and 2 increases the width of the orogen 3 sedimentation increases the length scale of both thin skinned and thick skinned thrust sheets and 4 results in a wider orogen 5 erosion helps to localize deformation resulting in a narrower orogen and a less well developed retro wedge a comparison of the modeled behaviors to the high atlas the pyrenees and the central alps three extensively studied natural examples characterized by different degrees of inversion is presented and confirms the predicted controls of surface processes and extensional inheritance on orogenic structure

geomaterials in cultural heritage this volume gives a broad view of the application of geoscience techniques to the study of monuments and objects from excavations and museums including their origin technique of manufacture age and conservation it reaffirms the important contribution of geosciences in the interdisciplinary approach to the study of complex materials such as minerals rocks glass metals mortar plaster slags and pottery the papers in this book cover three topics the study of pottery glass stone and mortar the application of raman spectroscopy to a wide variety of objects and the future of archaeometry interdisciplinary studies including field geology geophysics microscopy textural analysis physical methods and geochemistry are used to unlock information from the ancient materials such as the provenance of the raw materials the firing technology the ancient recipes and the alteration pathways

heterogeneous deformation recorded by magnetic fabrics in the pyrenean axial zone abstract magnetic fabrics studies ams are a useful tool in order to describe the distribution of deformation in orogenic areas where conventional techniques are difficult to apply especially due to the lack of proper strain markers in the present study ams and structural analysis are used to define the distribution of deformation in the central axial and nogueres zones an area of strong structural changes i in the geometry of the antiformal stack defining the pyrenean axial zone and ii the distribution of alpine cleavage the studied rocks are lower middle triassic red beds that crop out in three different stacked thrust units bielsa nogueres and orri primary sedimentary fabrics are preserved in the uppermost thrust units nogueres zone but a high percentage of the sampling sites shows an overprint of alpine compression on magnetic fabrics with the magnetic lineation mostly parallel to the tectonic grain defined by compressional structures and the magnetic foliation showing different orientations between the poles to cleavage and bedding the development of compressional fabrics strongly depends on the structural position of the sites and two deformation gradients can be inferred the southern margin of the axial zone orri and bielsa units shows strong internal deformation increasing towards the north farther north in the restored cross section deformation is in general terms lower but increases towards the basal thrust of the nogueres zone the heterogeneous distribution of alpine internal deformation indicates a preferred development of cleavage in the variscan basement and overlying units of the southern margin of the axial zone mainly in the orri unit that could be partly controlled by the tectonic load resulting from the stacking of thrust sheets

electrical resistivity model of the crust and upper mantle from a magnetotelluric survey through the central pyrenees summary an mt profile which roughly coincides with the south side of the ecors pyrenees deep reflection seismic profile was made from the north pyrenean zone through the central pyrenees and ebro basin the periods recorded ranged from 0 0128s to 2000 s analysis of mt data shows a 2 d conductive structure the strike direction of the structure is e w parallel to the pyrenean chain interpretation of the data includes geomagnetic transfer functions and is constrained by some relevant geometric crustal features observed in seismic data accordingly a 2 d resistivity cross section has been obtained the most striking results are 1 detection of subvertical conductors in the upper crust coinciding with major fault zones 2 detection of a deep high conductivity zohe at the contact between the iberian and the european plates 3 the fact that the european plate is thicker and more resistive than the iberian one interpretation of the deep high conductivities suggests the existence of partial melting in the pyrenees related to the subduction of the iberian plate beneath europe

facies architecture and geometry of a prograding carbonate ramp during the early stages of foreland basin evolution lower eocene sequences sierra del cadi se pyrenees spain this paper describes the early eocene sedimentological evolution of the sierra del cadi carbonate platform during the early development of the southeastern pyrenean foreland basin spain the platform developed as a south facing ramp system located either across the southern margin of a growth anticline within the newly formed basin or along the axial margin of the basin sequences i and ii both comprise basal transgressive systems tracts tsts dominated by a thick succession of outer ramp lime mudstones shallowing upwards into a highstand systems tract hst of mid and inner ramp bioclastic shoals sand banks and lagoonal deposits in sequence iii the tst comprises a thick wedge shaped unit of east to west backstepping inner and mid ramp nummulites shoals and lagoonal deposits progressively overlain by a thick succession of outer ramp lime mudstones and marls of the hst no lowstand systems tracts are recognized sequence boundaries correspond to flooding surfaces which grade basinwards into correlative conformities interpreted to represent the onset of high tectonic activity in the orogenic wedge and resulting high flexural subsidence across the foreland and drowning of inner ramp regions tsts represent continued high flexural subsidence creating accommodation space infilled by high rates of outer ramp sediment accumulation in sequences ii and iii tsts show a pronounced west to east thickening interpreted to represent the effect of variable subsidence across the margins of an uplifting growth anticline within the otherwise flexurally subsiding foreland prograda tional successions that characterize hsts developed during periods of reduced tectonic subsidence both within the foreland and in the orogenic belt allowing the growth and expansion of carbonate ramp facies belts

geological significance of seismic reflections in collision belts geological problems raised by the interpretation of deep seismic reflections in collision belts result from the structural complexity of the crust and the lack of surface control and well documeted references some of these problems are illustrated by examples coming from various tectonic settings in france and adjacent areas and tentative interpretations are proposed

tethys atlantic interaction along the iberia africa plate boundary the betic rif orogenic system abstract initial se dipping slow subduction of the ligurian tethys lithosphere beneath africa from late cretaceous to middle oligocene twisting to a later faster e dipping subduction of the subcrustal lithosphere is proposed as an efficient geodynamic mechanism to structure the arcuate betic rif orogenic system this new subduction related geodynamic scenario is supported by a kinematic model constrained by well dated plate reconstructions tectonic sedimentary and metamorphic data sets the slow initial se dipping subduction of the ligurian tethys realm beneath the malaguide upper plate unit is sufficient to subduct alpujarride and nevado filabride rocks to few tens of kilometers of depth in middle eocene times the shift from se to e dipping subduction during latest oligocene early miocene was possibly caused by both the inherited geometry of the highly segmented ligurian tethys domain and by the fast roll back of the subducted lithospheric slab the early miocene rather synchronous multiple crustal and subcrustal processes comprising the collision along the betic front the exhumation of the hp lt metamorphic complexes the opening of the alboran basin its flooring by hp alpujarride rocks and subsequent ht imprint can be explained by the fast nw and w directed roll back of the ligurian tethys subcrustal lithospheric slab the w retreat of the ligurian tethys lithosphere in middle late miocene times could partly explain the initiation of its lateral tear and consequent subcrustal processes from latest miocene onward the betic rif system evolved under both the northerly push of africa resulting in tightening at crustal and subcrustal levels and by the distinct current dynamics of the steep lithospheric slab the sw directed scape of the rif fold belt is one of the most striking evidences linked to the recent evolution of the squeezed betic rif system between africa and iberia

assessment of shallow landslide susceptibility by means of multivariate statistical techniques several multivariate statistical analyses have been performed to identify the most influential geological and geomorphological parameters on shallow landsliding and to quantify their relative contribution a data set was first prepared including more than 30 attributes of 230 failed and unfailed slopes the performance of principal component analysis t test and one way test allowed a preliminary selection of the most significant variables which were used as input variables for the discriminant analysis the function obtained has classified successfully 88 5 per cent of the overall slope population and 95 6 per cent of the failed slopes slope gradient watershed area and land use appeared as the most powerful discriminant factors a landslide susceptibility map based on the scores of the discriminant function has been prepared for ensija range in the eastern pyrenees an index of relative landslide density shows that the results of the map are consistent copyright 2001 john wiley sons ltd language en

structural significance of an evaporite formation with lateral stratigraphic heterogeneities southeastern pyrenean basin ne spain we run a series of analogue models to study the effect of stratigraphic heterogeneities of an evaporite formation on thin skinned deformation of the southeastern pyrenean basin spb ne spain thi

palaeomagnetic evidence for post thrusting tectonic rotation in the southeast pyrenees spain abstract the structural framework of the southeast pyrenees led to two conflicting interpretations thrust tectonics vs wrench tectonics to explain the geometry of this mountain range in the present study palaeomagnetic data are presented in an attempt to resolve this conflict the data reveal different magnetisation directions that indicate tectonic rotations about vertical axes by means of a regionally homogeneous pattern of rotation three tectonic units could be distinguished in the southeast pyrenees the internal unit in the north reveals no rotation since the permian the external unit to the south shows anticlockwise rotation of 25 younger than the early oligocene the pedraforca unit placed on the external unit shows 57 clockwise rotation which can be assigned to the neogene the anticlockwise rotation of the external unit can be explained by differential compression during the last phase of pyrenean thrusting whereas the clockwise rotation of the pedraforca unit can be interpreted by post thrusting tectonics the rotation pattern of the southeast pyrenees provides evidence for both cretaceous to paleogene n s compression and neogene right lateral wrench tectonics

different weathering stages indicated by the magnetization of limestones an example from the southeast pyrenees spain abstract paleomagnetic and structural data from the pedraforca thrust sheet in the southeast pyrenees show that the chemical weathering of the late cretaceous limestones is a multistage process the first weathering stage of latest eocene to early oligocene age is indicated by a chemical remanent magnetization carried by hematite the formation of hematite as the dominant weathering product suggests a subtropical climate in northeast spain during this period the second weathering stage is indicated by the presence of goethite which carries a chemical remanent magnetization parallel to the present earth field this suggests formation of the goethite since the late pleistocene under cooler climatic conditions similar to the present day climate in the pyrenees

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

glass production in late antiquity and the early islamic period a geochemical perspective first millennium ad glass production was divided between a relatively small number of workshops that made raw glass and a large number of secondary workshops that fabricated vessels glass compositions reflect the primary glassmaking source for most of the period egyptian mineral soda was fused with lime bearing siliceous sand to produce soda lime silica glass the location of the belus glassmaking sand which is known from the classical literature is located on that part of the levantine coast where iron contents are lowest sr 87 sr 86 of primary glass from workshops in the levantine region is close to that of modern seawater and confirms the use of beach sand which contained shell heavy mineral assemblages of levantine beach sands are dominated by hornblende hence the primary glasses are characterized by very similar trace element signatures glasses believed on archaeological grounds to have been made in other regions for example in inland egypt may have higher sr 87 sr 86 reflecting terrigenous sources of lime and have different trace element signatures compositional data for glasses from as far away as britain suggest origins of the glass material in the eastern mediterranean recycling of old glass may be recognized by the presence of elevated transition metals the use of plant ash as a flux became dominant practice in the ninth century and preliminary data for plant ash glasses from the early islamic world indicate that primary production centres may be separated using strontium and oxygen isotopes as well as by major and trace elements

neodymium isotopes as tracers in marine sediments and aerosols north atlantic nd and sm concentrations and nd isotopic compositions were measured on the detrital fraction of deep sea surface sediments and on aerosols sampled over the north atlantic and mediterranean sea the data expressed asend 0 and as model ages ranged from 14 5 end 0 4 9 and from 0 01 to 2 21 ga respectively two areas where the sediments contain relatively less radiogenic nd are to the west off north africa and eastward of the canadian shield this distribution is consistent with other tracers in suggesting that a significant fraction of the sediments are derived from aeolian material transported by major wind systems saharan dust transported in the equatorial trade winds belt and north american soil material transported in the latitudes of the westerlies between these aeolian dominated belts along an axis from the azores to gibraltar and the mediterranean lies a zone of more radiogenicend 0 values in sediments and aerosols influenced by the recent volcanism of this region previously reported distributions of nd isotopes in bottom formed iron manganese crusts and coatings are similar to distributions of nd isotope values in detrital sediments and aerosols this suggests that the detrital fraction has undergone partial dissolution and desorption in the water column and or in the pore waters of near surface sediments and that a significant proportion of nd in the authigenic ferromanganese phases is derived from this source and may therefore not represent strictly dissolved seawater nd isotope ratios useful as watermass tracers

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

a transtensional basin model for the organya basin central southern pyrenees based on magnetic fabric and brittle structures summary the purpose of this paper is to explain the kinematics of the inverted extensional organy basin centralsouthernpyrenees duringitsextensionalevolution thestudyoftheanisotropy of magnetic susceptibility ams and the study of brittle mesostructures are the instruments used to decipher the extensional kinematics separation of magnetic subfabrics analyses of ams at low temperature and anisotropy of the anhysteretic remanence aarm has been also done to properly interpret the obtained magnetic fabric data the combination of all magnetic fabric and brittle mesostructures analyses has provided new information to clarify thestructuralevolutionofthebasin whichsupportanewtectonicmodelfortheaptian albian basinal stage 20 sites for the magnetic fabric analysis were sampled in aptian lower albian marls the ams ellipsoids obtained at room temperature show their kmin axes perpendicular to bedding and kmax axes oriented nw se in 70 per cent of the samples n s in 15 per cent and ne sw in 15 per cent analyses of ams at low temperature show a better clustering of the axes of the magnetic ellipsoid pointing out that phyllosilicates constitute the carriers of the ams whereas the analyses of the aarm confirm the scattering of the ferromagnetic grains these results suggest that the obtained ams in the organy a basin was acquired during or shortly after deposition of the aptian lower albian marls without any subsequent overprint the direction of the magnetic lineation obtained from the ams at room and low temperatures agrees with the orientation of the stress axes obtained from the analysis of brittle mesostructures mainly faults and calcite filled tension gashes indicating its tectonic origin we interpret the orientation of the magnetic ellipsoids related to the transtensional movements linked to the formation of the organy a basin during the aptian albian interval which are consistent with the eastward displacement and rotation of iberia with respect to europe analysis oftensiongashesalsoindicatesamainnw seextensiondirection whereaspalaeostressanalysis of striated faults shows a more n s trending 3 the transtensional model proposed from magnetic fabric and brittle mesostructures for the organy a basin during the aptian albian is consistent with the creation of a strongly subsiding area south of the axial zone during the cretaceous and implies that rotation and separation of iberia respect to europe took place simultaneously

did the late paleocene thermal maximum affect the evolution of larger foraminifers evidence from calcareous plankton of the campo section pyrenees spain the larger foraminifer turnover lft which marks the base of the ilerdian stage may be related to the late paleocene thermal maximum lptm or be at least nearly coeval with that climatic event thus the impact of the lptm may have been greater than hitherto realised having also affected mid latitude shallow marine biota this conclusion has been reached after a re study of the calcareous plankton of the uppermost paleocene and lowermost eocene interval of the campo section in the central southern pyrenees campo is an important reference section because it contains larger foraminifers planktic foraminifers and calcareous nannofossils and their co occurrence was used to intercalibrate their respective zonal schemes previous studies at campo placed the onset of planktic foraminiferal zone p5 near the base of the ilerdian and the calcareous nannofossil np9 np10 chronal boundary sensu bybell l m self trail j m 1995 evolutionary biostratigraphic and taxonomic study of calcareous nannofossils from a continuous paleocene eocene boundary section in new jersey us geol surv prof pap 1554 pp 1 36 not less than 150 m above the ilerdian lower limit by these estimates the lptm known to have occurred in the middle part of zone p5 and just before the np9 np10 boundary would be an event much younger than the lft however our reexamination of planktic foraminifers suggests that the base of the ilerdian is probably situated at the middle of zone p5 a possibility proposed by hillebrandt in 1965 but denied by later authors for instance morozovella occlusa has been found for the first time in the campo section its last appearance datum lad which in the pyrenees was approximately coeval with that of morozovella velascoensis event used to place the top of zone p5 has been identified in beds situated less than 70 m above the base of the ilerdian such thickness represents a time span of a similar magnitude as the one which separated the lptm and the lad of m occlusa in the deep water hemipelagic succession of the basque basin in the western pyrenees autochthonous calcareous nannofossils are neither abundant nor well preserved in most of the studied interval with rhomboaster bramlettei the marker of the base of zone np10 being extremely rare in lower and middle ilerdian beds a fact that makes it very difficult to fix the position of the np9 np10 boundary in the campo section however the bases of zones np9 and np11 have been located and they support the zonation with planktic foraminifers these new data suggest that the lft and the lptm may have been coeval or nearly so a possibility reinforced by correlation with sections of the basque basin specialists of larger benthic foraminifers can easily delineate the lft in shallow water carbonate successions of the tethys domain and they propose to place the paleocene eocene boundary at the base of the ilerdian stage on the other hand the deep

multiepisodic evaporite sedimentation as an indicator of palaeogeographical evolution in foreland basins south eastern pyrenean basin early middle eocene extensive deposition of marine evaporites occurred during the early middle eocene in the south eastern pyrenean basin north east spain this study integrates stratigraphic and geochemical analyses of subsurface data oil wells seismic profiles and gravity data together with field surveys to characterize this sedimentation in the foredeep and adjacent platform four major evaporite units were identified the oldest was the serrat evaporites unit with a platform slope basin configuration thick salina and sabkha sulphates accumulated on the platform whereas resedimented and gravity derived sulphates were deposited on the slope and salt and sulphates were deposited in the deep basin in the subsequent unit vallfogona evaporites thin sulphates formed on the platform whereas very thick siliciclastic turbidites accumulated in the foredeep however some clastic gypsum coming from the platform gypsarenites and gypsum olistoliths was intercalated in these turbidites the following unit the beuda gypsum formation developed in a sulphate platform basin configuration where the topography of the depositional surface had become smooth the youngest unit the besalu gypsum formed in a shallow setting this small unit provides the last evidence of marine influence in a residual basin sulphur and oxygen isotope compositions are consistent with a marine origin for all evaporites however 34s and 18o values also suggest that except for the oldest unit serrat evaporites there was some sulphate recycling from the older into the younger units the south eastern pyrenean basin constitutes a fine example of a foreland basin that underwent multiepisodic evaporitic sedimentation in the basin depositional factors evolved with time under a structural control decreasing complexity is observed in the lithofacies as well as in the depositional models together with a diminishing thickness of the evaporite units

the geological significance of the western termination of the merens fault at port vell central pyrenees abstract a detailed local structural map of the merens fault zone at port vell vall ferrera reveals that the main fault related mylonite band splits westwards into a network of mylonite zones these consist of bands of highly strained rocks exhibiting tightened folds transposed foliations and extensive obliteration of pre existing structures evidence of continuity of marble layers across the port vell mylonite zone and structural and metamorphic similarities on both sides of the port vell mylonite band indicate that there is no significant throw across it the mylonite foliation forms parallel to the axial planes of tight folds in or near the mylonite zone which can be related to more open folds in adjacent areas the port vell mylonite band corresponds to a pinched w e axial trending late fold in order to estimate the importance of these results a review of the controversial geological significance of mylonite belts in the pyrenees with special emphasis on the merens fault introduces the paper

main results of the ecors pyrenees profile abstract the 250 km long deep seismic reflection survey across the pyrenees from one foreland ebro basin to the other aquitaine basin was designed to study the structure of the deformed mesozoic boundary between the iberian and european plates the results are 1 1 the entire crust shows well defined reflectors with a general fan shape geometry 2 2 a deep layered domain is evident above the moho discontinuity 3 3 near the surface in the external domains reflectors accurately define the geometry of major thrusts and structures affecting the mesozoic and cenozoic cover of the pyrenees 4 4 the middle crust shows two major sets of seismic events interpreted as hercynian structures using these results a balanced structural section of the pyrenean belt is proposed the mode of thickening of the crust during the alpine orogeny is briefly discussed only the iberian crust was significantly thickened by a southward stacking of slabs

sinkholes and caves related to evaporite dissolution in a stratigraphically and structurally complex setting fluvia valley eastern spanish pyrenees geological geomorphological and environmental implications abstract evaporite karst and sinkhole development is analysed in a geologically complex area of ne spain including four evaporite units with different characteristics and affected by compressional and extensional tectonic structures the exposed paleosinkholes including remarkable early pleistocene paleontological sites provide valuable information on the subsidence mechanisms and reveal the significant role played by interstratal karstification in the area these gravitational deformation structures including hectometre scale bending folds and oversteepened normal faults strongly suggest that the present day compressional regime inferred in previous studies may be largely based on the analysis of non tectonic structures two gypsum caves ca 1 km long show that passages with restricted cross sectional area may produce large breccia pipes and sinkholes thanks to the removal of breakdown boulders by high competence episodic floods moreover the upward progression of cave ceilings by paragenesis and condensation dissolution contributes to increase the probability of sinkhole occurrence an inventory of 135 sinkholes together with their geological and geomorphological context has been developed this data base has been used to infer several properties of the sinkholes with practical implications a magnitude and frequency scaling relationship spatial distribution patterns dominant controlling factors and risk implications

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

exhumation of the southern pyrenean fold thrust belt spain from orogenic growth to decay 1 the deformation and exhumation history of an orogen reflects the interactions between tectonic and surface processes we investigate orogenic wedge deformation erosion and sedimentation in the pyrenees by a quantifying the spatiotemporal patterns of exhumation across the southern fold thrust belt ftb with bedrock apatite fission track aft thermochronology and b comparing the results with existing deformation exhumation and sedimentation chronologies eighteen new samples record exhumation during and after orogenesis between 90 and 10 ma rocks from the range core axial zone record rapid exhumation that progresses east to west and north to south consistent with patterns of tectonically driven uplift synorogenic sediments shed into piggyback basins on the southern fold thrust belt during mountain building retain a detrital exhumation signal from the axial zone in contrast samples from other structural positions record exhumation of the thin skinned pyrenean thrust sheets suggesting sediment burial and heating of sufficient magnitudes to reset the aft system 3 km in some locations exhumation of these fold thrust structures is likely an erosional response to thrust driven rock uplift we identify an exhumation phase 25 20 ma that occurs along the central and eastern spanish pyrenees at the boundary between thick and thin skinned portions of the wedge we suggest that this distributed exhumation event records a a taper response in the southern orogenic wedge to sediment loading and or b a shift to wetter stormier climate conditions following convergence driven uplift and full topographic development a final exhumation phase between 20 and 10 ma may record the excavation of the southern fold thrust system following base level lowering in the ebro basin

sequences of mesostructures related to the development of alpine thrusts in the eastern pyrenees abstract the mesostructures formed during the development of an antiformal stack in the eastern pyrenees are studied the following structural evolution is proposed a pressure solution cleavage develops by layer parallel shortening at initial stages of the thrusting the cleavage is present in all units but mainly in the marls and marly limestones in the siliceous layers a weak cleavage and small scale thrust structures develop the cleavage and the bedding are deformed during the thrusting different structures form in various places of the antiformal stack where the bedding is flat lying southward directed layer parallel shears predominate in the hangingwall ramps kink bands disjunctive stylolitic cleavage and layer parallel shear opposite to the sense of thrust movement develop the described structures constitute a kinematical model for mesostructures developed during the evolution and ramping of thrusts

unusual features of sediment supply dominated transgressive regressive sequences paleogene clastic wedges se pyrenean foreland basin spain abstract the paleogene marine to nonmarine succession in the southeastern pyrenean foreland basin consists of a series of 3rd order 3 5 m y transgressive to regressive sequences that can be related directly to the stacking and southward displacement of successive basement cover thrust sheets the regressive limbs of the 3rd order clastic wedges are coeval with thrust movement with maximum subsidence developing towards peak regression this relationship between sedimentation and tectonics is sediment supply driven one of these 3rd order wedges which was produced by the montserrat and sant llorenc del munt fan delta systems demonstrates how such steep sloped coarse grained high sediment supply systems generate a hierarchy of transgressive regressive architectures striking features of this rapidly subsiding supply dominated basin margin in addition to the tectonics wedge architecture relationship include the nonperiodic character of the contained high frequency sequences the unusual thickness and landward thickening geometry of transgressive systems tracts a tendency for misfit between alluvial fan and shorezone sectors of sequences a lack of marked incision associated with the tops of coarse grained regressive phases of sequences most of the features are symptomatic of high subsidence rates and very high sediment supply the last feature suggestive of few major relative falls of sea level is also consistent with continuous rapid subsidence however it should be remembered that lack of incision may be a poor indicator for lack of base level fall in a setting where the steepness of alluvial slopes exceeds the slope of the coeval shelf

morphology and sediment dynamics of the northern catalan continental shelf northwestern mediterranean sea abstract the northern catalan continental shelf in the northwestern mediterranean sea extends along 200 km from the cap de creus submarine canyon to the llobregat delta in the vicinity of the city of barcelona in this paper we present the results of a systematic investigation of this area by means of very high resolution multibeam bathymetry to fully assess its morphological variability the causative factors and processes determining such variability are subsequently interpreted the shelf is divided in three segments by two prominent submarine canyons the northernmost roses shelf is separated from the intermediate la planassa shelf by the la fonera canyon while the boundary between the la planassa shelf and the southernmost barcelona shelf is marked by the blanes canyon these two canyons are deeply incised in the continental margin with their heads located at only 0 8 and 5 km from the shore respectively the seafloor character reflects the influence of external controlling factors on the geomorphology and sediment dynamics of the northern continental shelf of catalonia these factors are the geological setting the volume and nature of sediment input and the type and characteristics of processes leading to sediment redistribution such as dense shelf water cascading dswc and eastern storms the interaction of all these factors determines sediment dynamics and allows subdividing the northern catalan continental shelf into three segments the erosional depositional roses shelf to the north the non depositional la planassa shelf in the middle and the depositional barcelona shelf to the south erosional features off the cap de creus peninsula and an along shelf subdued channel in the outer shelf illustrate prevailing sediment dynamics in the roses segment which is dominated by erosional processes local sediment accumulations and the southward bypass of sediment the rocky character of the seafloor immediately north of the blanes canyon head demonstrates that neither significant sediment inputs from the tordera river nor from the northern sources reach the southern part of the la planassa shelf palaeo shorelines depict a number of paleodeltas with steep delta fronts on the drowned barcelona shelf

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

milankovitch cyclicity within the middle eocene deep marine guaso system ainsa basin spanish pyrenees abstract the guaso system is the youngest deep marine stratigraphic component in the middle eocene deep marine ainsa basin in common with the older systems in the ainsa basin it was mainly fed from the east southeast by a range of sediment gravity flow processes including turbidity currents debris flows and suspended sediment river derived plumes e g hyperpycnal flows a study of the guaso system interfan sediments provides a 44 m long geochemical stratigraphic series constructed from spectral gamma ray k u and th content and bulk sediment geochemical data caco 3 toc 18 o and 13 c spectral and average spectral misfit analyses of these data identify obliquity and precession orbital modes as present with respective periods of approximately 10 and 6 m these cycles are interpreted as reflecting carbonate dilution cycles linked to variation in siliciclastic sediment input into the ainsa basin the presence of such orbitally induced carbonate dilution cycles is consistent with the identification of orbitally forced waxing and waning of coarse grained sediment supply within the coeval up system sediment supply system in the fluvio deltaic montanyana group of the tremp graus basin the presence of orbitally controlled sediment input to basin during interfan marlstone accumulation supplements to the growing body of evidence for the orbital control of sedimentation within the ainsa basin

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

the functioning of sediment routing systems using a mass balance approach example from the eocene of the southern pyrenees abstractsediment routing systems link source regions undergoing erosion with depositional sinks and involve a volumetric or mass budget understanding how these source to sink systems function is key to stratigraphic prediction but estimation of their surface sediment discharges and depositional fluxes on geological time scales is a challenging problem we recognize a paleosediment routing system from the geological record in the mid late eocene escanilla formation and time equivalents of the tectonically active wedge top region of the southern pyrenees by mapping the 200 km long fairway of the escanilla sediment routing system we obtain the sediment budget and grain size fractionation of three time intervals each of 2 5 2 6 m yr duration over the time period 41 6 33 9 ma four thousand cubic kilometers of sediment sourced principally from two feeder systems in the high pyrenees was deposited in a period of 7 7 m yr the positions of moving boundaries characterized by rapid reduction in the perc

oligocene miocene alluvial sedimentation in the northern ebro basin ne spain tectonic control and palaeogeographical evolution abstract the oligocene early miocene rocks cropping out in the northern ebro basin central sector comprise conglomerates at the margin of the basin gradually passing into sandstones and mudstones towards more central areas these rocks belong to the peraltilla and sarinena formations and originated in both small monogenic conglomerate alluvial fans that fed from the south pyrenean sierras directly and large polygenic conglomerate fans which drained more internal areas of the pyrenees their lithological textural and geometrical features in combination with sedimentary structures reveal the existence of several lithofacies associations whose lateral and vertical relationships and distribution throughout time have been used to establish the main features for each type of depositional system near the margin of the basin the tertiary series is folded and thrusted and several unconformities can be identified three tecto sedimentary units t3 to t5 have been characterised for the whole area at the margin they are bounded by angular or syntectonic unconformities in more central areas their correlative conformities can be registered as changes from coarsening to fining upward general trends or as sudden shifts in the vertical trend fining upward trends are related to onlaps and record the retrogradational stages of the alluvial fans in contrast coarsening upward trends record the progradation of the fans stratigraphic and sedimentological studies permit to establish the palaeogeographical evolution of the area during oligocene and early miocene times also it can be demonstrated that during periods of tectonic activity in the pyrenees the alluvial fans prograded whereas during the stages of relative tectonic inactivity the fans retrograded

radiogenic isotopes systematics and applications to earth surface processes and chemical stratigraphy radiogenic isotopes have wide application to chemical stratigraphy geochronology provenance studies and studies of temporal changes in earth surface processes this paper briefly reviews the principles of radiogenic isotope geochemistry and the distribution of a number of elements of interest in the environment and then uses this information to explore the range of applications to chemical stratigraphy and other fundamental subjects of sedimentary geology many of these applications center on the reconstruction of secular variations in paleoseawater isotope signals these seawater isotope curves can be used for stratigraphic correlation and to assess changes through earth history in processes such as tectonic uplift climate change biogeochemical cycling ocean circulation crustal growth and surface water evolution understanding the modern biogeochemical cycle of the element isotope system of interest is essential for gaining the maximum information regarding the operation of ancient cycles the main sources of uncertainty for reconstructing seawater isotope curves involve diagenetic alteration sample impurities and errors in age assignments rigorous sample selection criteria and pretreatment methods are keys to reconstructing the most accurate seawater isotope curves applications are discussed for the rb sr sm nd la ce lu hf re os u th pb k ar and cosmogenic isotope systems d 2003 elsevier b v all rights reserved

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

palaeostresses associated with thrust sheet emplacement and related folding in the southern central pyrenees huesca spain brittle mesostructures have been studied in the detached mesozoic and lower tertiary cover rocks of the south central pyrenees huesca province spain in order to reconstruct the state of stress within the thrust sheets during tertiary compression the structure of the area studied consists of nw se to e w striking south verging thrust sheets located west of the south pyrenean central unit the palaeostresses obtained show dominant n s to ene wsw compression directions for stress tensors with horizontal 1 axes and e w to nw se extension directions for stress tensors with vertical l axes the values of the stress ellipsoid ratios for stress tensors with horizontal 1 are predominantly between 0 and 0 5 indicating uniaxial compression to wrench regime regarding their relationship with macro structures the palaeostresses show transport parallel compression in most sites although thrust parallel compression is also found there are no differences between palaeostresses found in the hanging walls and the footwalls of thrusts stress tensors with vertical 1 do not show systematic relations with macro structures but transport parallel extension and thrust parallel extension are found in some sites the analysis of palaeostresses in areas of fold and thrust belts shows a high degree of complexity and the results are not easy to interpret the continuous variation from n s to ene wsw in the orientation of the compression axes is here interpreted in two ways 1 as the result of the clockwise rotation of the mesozoic and tertiary cover which was pushed in the east by the south pyrenean central unit with a constant n to nne regional compression and 2 due to ne sw compression resulting from a sw directed local transport of minor thrusts palaeostress analysis can therefore reveal important information about thrust kinematics at high structural levels where ductile deformation is absent

syntectonic burial and post tectonic exhumation of the southern pyrenees foreland fold thrust belt in the oligocene to earliest miocene the entire southern pyrenean foreland fold and thrust belt was backfilled and buried in up to 3 km of syntectonic continental conglomerates from the range9s own erosional debris then starting in the mid to late miocene the pyrenees were exhumed by erosional excavation to their present relief a model is proposed for this unusual development whereby late eocene oligocene tectonic uplift of the margins of the ebro basin raised local base level and blocked normal dispersal of erosional debris to adjacent oceans thus causing the basin to fill then backfill northwards across the entire southern flank of the pyrenees subsequent miocene rifting of the catalan mediterranean margin and the messinian salinity crisis lowered base level allowing the ebro river to cut headward capture the ebro basin and re excavate the pyrenees

tectonic and sediment provenance evolution of the south eastern pyrenean foreland basins during rift margin inversion and orogenic uplift abstract the cretaceous to oligocene detrital record in the southern eastern pyrenees is utilized to address the degree to which precursor basin architecture and hyper extensional rift structures impacted subsequent sedimentary provenance and dispersal systems and foreland basin evolution this study presents new isotopic provenance analysis of detrital zircon u pb and u th he double dating and detrital rutile u pb and trace element geochemistry to track sediment provenance evolution late cretaceous paleocene sediments show zircon with dominantly variscan u pb and jurassic early cretaceous zhe cooling ages that are derived from southeastern catalan coastal ranges and eastern corsica sardinia regions and localized structural inversion along inherited mesozoic extensional faults and erosional recycling of syn rift sediments eocene deposits have multimodal u pb ages that stratigraphically upsection change to unimodal variscan ages with the appearance and upsection increase in pyrenean zhe ages and increase in variscan aged detrital rutile that record a significant shift in sediment source area to northern sources recording exhumation and unroofing of the axial zone paleozoic basement sources and development of new ramp flat style structures in the southern pyrenean zone fold thrust belt during the oligocene incipient foreland basin deposits were cannibalized and recycled into the foreland basin as thrusting advanced toward the foreland the eastern pyrenean foreland basin records a different provenance history from central pyrenean tremp basin suggesting the basins were segmented throughout the late cretaceous to oligocene while the ripoll and ager basins appear to have shared similar source areas the sediment provenance evolution coupled with pyrenean fault activity and shortening rates hinterland exhumation foreland basin subsidence and climate proxies presents a detailed dataset to understand these relationships within the eastern pyrenean orogenic system and highlight the dominant control precursor basins and structural inheritance has on the subsequent fold thrust belts and foreland basin evolution

provenance of oligocene miocene alluvial and fluvial fans of the northern ebro basin ne spain an xrd petrographic and sem study abstract this paper combines stratigraphic and sedimentological data with xrd petrographic and sem techniques in order to investigate the fluvial and alluvial fans that were developed during the oligocene and the lower miocene in the central area of the northern ebro basin spain and their respective source areas the proximal sectors of the coeval depositional systems can be separated on the basis of lithofacies criteria conglomerate features reveal that the source areas for the alluvial fans were limited to the south pyrenean sierras whereas those of the fluvial fans included more northern pyrenean areas such as the axial zone or the clastic tremp graus basin far from the basin margin the distal alluvial facies interdigitate with the middle distal fluvial deposits in these areas only detailed mineralogical and petrographic analysis of the rocks can determine their origin thus the methods used have allowed us to differentiate between authigenic and detrital phases on the basis of these observations three different types of coarse sandstone petrofacies have been distinguished 1 carbonate rich sandstone 2 high quartz sandstone and 3 high lithic fragment sandstone rich in shale and feldspars grains the first corresponds to the alluvial samples and corroborates the south pyrenean sierras as alluvial fans source area the high quartz and the high lithic fragment sandstone correspond to the fluvial samples and evidence that the drainage basin of the fluvial fans included the clastic tremp graus basin and the axial zone the high lithic fragment petrofacies is representative of the most ancient fluvial rocks whereas the high quartz sandstone corresponds to the recent and nonconforming fluvial rocks this change in the fluvial petrofacies allows us to recognise the changing importance of each region as a source area of the fluvial fans over time which can be correlated with pyrenean tectonic activity during the oligocene

large sediment waves over the gulf of roses upper continental slope nw mediterranean recently acquired swath bathymetry and seismic datasets on the gulf of roses continental slope revealed the presence of large sediment waves that have developed between 200 and 400 m water depth geometric parameters were computed from the multibeam dataset and the obtained results showed mean sediment wave lengths of 2000 m and maximum heights of 60 m the analysis of seismic profiles showed the general architecture of the late quaternary deposits over the gulf of roses outer shelf and slope the outer continental shelf is characterized by morphological erosional features affecting the upper part of the most recent seismic unit over the continental slope five main unconformity bounded seismic units are differentiated with sediment waves developed in all of them the sediment waves observed over the continental slope are presumably generated by bottom currents intensified during major dense shelf water cascading events flowing downslope at an oblique angle with respect to the main bathymetry

duplexes as slip transfer zones application to the himalayan fold thrust belt abstract duplex fault zones and imbricate fans originally termed schuppen schuppenstruktur or imbricate structure were first described in the late 1800s from the alps nw highlands scotland and montana rockies lewis thrust sheet as originally defined duplexes contained shingled imbricate slices bounded above and below by through going thrusts these duplex fault zones commonly occur along the base of major regional thrust sheets or within the body of such sheets accommodating regional bed parallel shortening and transferring slip from a lower stratigraphic horizon to a higher one thereby providing a mechanical advantage to the emplacement of large thrust sheets however faulting is not the only means of layer parallel shortening lps and displacement transfer within duplexes lps cleavage and detachment folds are also common and can play the same role as imbricate faults based on some selected examples we recognize three types of duplexes 1 fault duplex 2 cleavage duplex and 3 fold duplex the style of duplex that forms is likely a function of mechanical stratigraphy and deformation conditions the relationships among the three basic duplex styles can be plotted on a ternary diagram each duplex type constituting an apex given the complexities of most sedimentary sequences hybrid duplexes with a mix of fault fold and cleavage shortening can also form hybrid duplexes plot along the side of the triangle as fault fold fold cleavage and fault cleavage duplexes while those combining all three mechanisms plot in the middle if the partitioning of shortening by the different mechanisms can be quantified the ternary diagram provides a means of representing the contributions of the three mechanisms in shortening and slip transfer along much of the himalayan fold thrust belt a significant portion of the lesser himalayan shortening is taken up by the lesser himalayan duplex a first order fault duplex with subsidiary cleavage and fold development the geometry of and shortening within the duplex varies significantly along the length of the himalaya

thrust sequences in the eastern spanish pyrenees detailed mapping of the south pyrenean zone in the eastern spanish pyrenees shows that a great number of alpine thrusts affect the basement and the cover the geometry of the thrust structures and their propagation sequence can be interpreted from balanced sections the folding dies out downwards from the higher thrust sheets to the lower ones and demonstrates a piggy back thrusting sequence these thrusts form a duplex the sole thrust of this duplex is the vallfogona thrust the roof thrust is rooted somewhere within the axial zone the thrusts climb southwards from the axial zone basement up into tertiary cover sediments these thrusts have been folded so that they now dip to the south and form the southern side of the axial zone antiformal stack locally smaller antiformal stacks developed and produced strong folds in the higher thrust sheets the south pyrenean zone studied is equivalent to the gavarnie nappe and the connection between them below the detached south pyrenean central unit may be the nogueres zone

coal deposition in carbonate rich shallow lacustrine systems the calaf and mequinenza sequences oligocene eastern ebro basin ne spain two main coal bearing sequences developed during the oligocene in the tertiary ebro basin the calaf early oligocene and mequinenza late oligocene coal basins coal deposition took place in shallow marsh swamp lake complexes which sometimes became closed and evolved under warm climatic conditions with fluctuating humidity these shallow lacustrine systems are closely interrelated with the terminal parts of the distributive fluvial systems which spread from the tectonically active ebro basin margins laterally extensive lignite bearing sequences including rather thin lenticular autochthonous and or hypautochthonous coal seams with high ash and sulphur contents characterized coal deposition in the shallow lacustrine systems coal seam geometry which makes them nearly subeconomic resulted from the tectonic instability during basin margin evolution and the sometimes closed arid conditions under which the lacustrine systems evolved high ash and sulphur contents resulted from the inadequate isolation of peat forming environments from clastic influx and from the very low acidity and sometimes high sulphate contents of the lacustrine waters coal exploration in shallow lacustrine sequences similar to those described here must take into account that the spread of coal forming environments and maxima of coal deposition are usually coincident with lake expansions and retraction or shifting of the terminal fluvial zones interrelated with the lacustrine areas

karst subsidence as a control on the accumulation and preservation of aeolian deposits a pleistocene example from a proglacial outwash setting ebro basin spain meltwater flows emanating from the pyrenees during the pleistocene constructed a braided outwash plain in the ebro basin and led to the karstification of the neogene gypsum bedrock synsedimentary evaporite dissolution locally increased subsidence rates and generated dolines and collapses that enabled the accumulation and preservation of outwash gravels and associated windblown deposits that were protected from erosion by later meltwater flows in these localized depocentres maximum rates of wind deceleration resulted from airflow expansion enabling the accumulation of cross stratified sets of aeolian strata climbing at steep angles and thereby preserving up to 5 m thick sets the outwash plain was characterized by longitudinal and transverse fluvial gravel bars channels and windblown facies organized into aeolian sand sheets transverse and complex aeolian dunes and loess accumulations flat lying aeolian deposits merge laterally to partly deformed aeolian deposits encased in dolines and collapses synsedimentary evaporite dissolution caused gravels and aeolian sand deposits to subside such that formerly near horizontal strata became inclined and generated multiple internal angular unconformities during episodes when the wind was undersaturated with respect to its potential sand transporting capacity deflation occurred over the outwash plain and coarse grained lags with ventifacts developed subsequent high energy flows episodically reached the aeolian dune field leading to dune destruction and the generation of hyperconcentrated flow deposits composed in part of reworked aeolian sands lacustrine deposits in the distal part of the outwash plain preserve rhythmically laminated lutites and associated gilbert type gravel deltas which developed when fluvial streams reached proglacial lakes this study documents the first evidence of an extensive pleistocene proglacial aeolian dune field located in the ebro basin 41 50 n south of what has hitherto been considered to be the southern boundary of pleistocene aeolian deposits in europe a non conventional mechanism evaporite karst related subsidence for the preservation of aeolian sands in the stratigraphic record is proposed

evaluating magnetic lineations ams in deformed rocks magnetic lineation in rocks is given by a cluster of the principal axes of maximum susceptibility kmax of the anisotropy of magnetic susceptibility ams tensor in deformed rocks magnetic lineations are generally considered to be the result of either bedding and cleavage intersection or they parallel the tectonic extension direction in high strain zones our ams determinations based on a variety of samples that were taken from mudstones slates and schists from the pyrenees and appalachians show that strain is not the only factor controlling the development of magnetic lineation we find that the development and extent to which the magnetic lineation parallels the tectonic extension direction depends on both the original ams tensor which in turn depends on the lithology and the deformation intensity rocks having a weak pre deformational fabric will develop magnetic lineations that more readily will track the tectonic extension

on the consistency of proposed models for the pyrenees with the structure of the eastern parts of the belt abstract the structure of the eastern pyrenees consists mainly of south directed thrusts involving basement and cover rocks an antiformal stack developed by the piling up of basement thrust sheets which outcrop in the axial zone these structures account for a thin skinned thrust model rather than a vertical fault model in which the axial zone would be essentially autochthonous and the north pyrenean fault the axial plane of a fan thrust system new data from the eastern pyrenees and the thin skinned model suggest that 1 the structure east of the pedraforca nappe is similar to that of the central pyrenees 2 the cover rocks of the south pyrenean units and of the axial zone after restoration built up a northwards thickening prism consistent with the existence of a unique pyrenean sedimentary basin during mesozoic time 3 the axial zone is only a complex antiformal stack developed as a part of south pyrenean system related to the paleogene thrusting tectonics the axial zone palaeogeographic area had no special meaning during mesozoic time

measurement of landslide displacements using a wire extensometer a continuous recording of landslide displacements is often required in order to better understand the complex relationship between the triggering factors and the dynamics of the movement in this paper we discuss the performance of the borehole wire extensometer and the interpretation of its results the analysis for the case of a translational slide shows that the displacements measured with the wire extensometer are systematically smaller than the movements observed at the ground surface a relationship between the wire readings and the horizontal component of the landslide movement has been established by means of three equations representing different stages of the wire displacement within the borehole the applicability of these equations and the interpretation of the wire extensometer readings have been successfully checked at two landslide sites vallcebre in the eastern pyrenees and alvera in the dolomites

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

evaluating balanced section restoration with thermochronology data a case study from the central pyrenees we present a new method that can be used to quantitatively evaluate the consistency between balanced section restorations and thermochronological data sets from orogenic belts we have applied our method to a crustal scale area balanced cross section restoration along a profile in the central pyrenees this restoration is well constrained and supported by a wide variety of geological and geophysical data moreover an extensive thermochronological data set has been collected independently in the area we use the structural kinematic software 2d move to constrain a set of velocity fields that describes the kinematics of the central pyrenees using these velocity fields as input for the thermokinematic code pecube we derive predictions of the thermal history and a range of thermochronometric ages for the modeled area we find that the kinematic history of the belt as inferred from section balancing is in good agreement with the published thermochronological data high temperature zircon fission track and k feldspar ar ar data constrain the thermal structure of the belt as well as the timing of underplating low temperature apatite fission track and u th he data require late synorogenic sedimentary burial of the southern flank of the pyrenees between late eocene 40 ma to late miocene 9 ma times consistent with previous studies and imply that no such burial occurred on the northern flank

pliny the elder and sr nd isotopes tracing the provenance of raw materials for roman glass production in roman and byzantine times natron glass was traded throughout the known world in the form of chunks production centers of such raw glass active from the 4th to 8th century ad were identified in egypt and syro palestine however early roman primary glass units remain unknown from excavation or scientific analysis the ancient author pliny described in 70 ad that besides egyptian and levantine resources also raw materials from italy and the gallic and spanish provinces were used in glass making in this study the primary provenance of 1st 3rd century ad natron vessel glass is investigated the use of combined sr and nd isotopic analysis allows the distinguishing and characterizing of different sand raw materials used for primary glass production the isotope data obtained from the glass samples are compared to the signatures of primary glass from known production centers in the eastern mediterranean and a number of sand samples from the regions described by pliny the elder as possible sources of primary glass eastern mediterranean primary glass has a nile dominated mediterranean nd signature higher than 6 0 nd while glass with a primary production location in the western mediterranean or north western europe should have a different nd signature lower than 7 0 nd most roman glass has a homogeneous 87sr 86sr signature close to the modern sea water composition likely caused by the intentional use of shell as glass raw material in this way strontium and neodymium isotopes now prove that pliny s writings were correct primary glass production was not exclusive to the levant or egypt in early roman days and factories of raw glass in the western roman empire will have been at play

provenance of lithogenic surface sediments and pathways of riverine suspended matter in the eastern mediterranean sea evidence from 143nd 144nd and 87sr 86sr ratios in order to characterize the provenance of lithogenic surface sediments from the eastern mediterranean sea ems residual leached fraction of 34 surface samples have been analysed for their 143 nd 144 nd and 87 sr 86 sr isotope ratios the sample locations bracket all important entrances of riverine suspended matter into the ems as well as all sub basins of the ems the combined analyses of these two isotope ratios provide a precise characterization of the lithogenic fraction of surface sediments and record their dilution towards the central sub basins we reconstruct provenance and possible pathways of riverine dispersal and current redistribution assuming more or less homogenous isotopic signatures and flux rates of the eolian fraction over the ems lithogenic sediments entering the ionian sea from the calabrian arc and the adriatic sea are characterized by high 87 sr 86 sr isotope ratios and low end 0 values average 87 sr 86 sr 0 718005 and end 0 11 06 n 5 aegean sea terrigenous sediments show an average ratio of 87 sr 86 sr 0 713089 n 5 and values of end 0 7 89 n 5 the aegean isotopic signature is traceable up to the southwest south and southeast of crete the sediment loads entering the ems via the aegean sea are low and spread out mainly through the strait of casos east of crete surface sediments from the eastern levantine basin are marked by the highest end 0 values 3 3 n 6 and lowest 87 sr 86 sr isotope ratios average 0 709541 n 6 reflecting the predominant input of the nile sediment the influence of the nile sediment is traceable up to the ne trending eastern flank of the mediterranean ridge the characterization of the modern riverine dispersal and eolian flux based on isotope data may serve as a tool to reconstruct climate coupled variations of lithogenic sediment input into the ems d 2002 elsevier science b v all rights reserved

kinematics and strain distribution in an orogen scale shear zone insights from structural analyses and magnetic fabrics in the gavarnie thrust pyrenees abstract this work aims to characterize the gavarnie thrust one of the large scale thrusts that define the alpine structure of the west central sector of the pyrenees a detailed comparison of structural analysis and magnetic fabrics is carried out for the paleozoic phyllonites of the gavarnie thrust in order to decipher strain distribution and transport direction the ams at room rt ams and low lt ams temperature and the airm can be correlated with the structural patterns kmin axes are mainly parallel to the pole of the s c or c planes and kmax axes are parallel to the transport direction and related to ductile s c structures furthermore the pj t changes across the shear zone characterize strain variations larger pj and t are found in the basal most deformed part of the shear zone and lower values are found where the interaction between alpine and variscan related petrofabrics is stronger we also interpret the reactivation of variscan inherited fabrics within the alpine shear zone in spite of the heterogeneous strain markers indicate a common top to the south n190e alpine transport direction which contrasts with the strong obliquity of the genetically related structures developed in the southern mesozoic sedimentary cover in this sense our data suggest a complete decoupling between basement and cover units during the alpine compression

large scale facies change in the middle eocene south pyrenean foreland basin the role of tectonics and prelude to cenozoic ice ages abstract the present study reports a sedimentological analysis of the guara limestone formation deposited during the lutetian in the sierras exteriores in the south pyrenean foreland basin we provide a detailed facies analysis of the carbonates to precise the paleoenvironmental context during their deposition we show that those limestones are mainly composed of shallow water foraminifers and were deposited in relative shallow water environments

asymmetric growth of the pyrenees revealed through measurement and modeling of orogenic fluxes orogenic asymmetry is ubiquitous in terms of topography structure and metamorphism but the relative influences of climate and tectonics in determining such asymmetry remain contentious this study demonstrates that for the case of the european pyrenees orogenic asymmetry is not defined by inherited structural asymmetry nor by orographic asymmetry of precipitation but is the simple consequence of the inherent tectonic growth of a doubly vergent orogen the pyrenees record approximately 60 myr of upper crustal accretion erosion and sedimentation that developed from late cretaceous to early miocene times approximately 165 km of plate convergence was accommodated by four phases of orogenic growth that can be summarized in terms of their generic orogenic development as follows 1 early inversion of passive margin extensional faults initiating the pro wedge 2 growth by a combination of frontal accretion and underplating to the pro wedge symmetrical and steady record of erosion and foreland basin sedimentation 3 cessation of pro wedge frontal accretion with propagation of the retro wedge deformation front 4 accelerated growth of pro wedge antiformal stack induced by underplating accelerated erosion over antiformal stack and increase in sediment discharge to pro foreland basin stabilization of outer pro wedge by sediment blanketing discrete element model experiments are used to explore the natural tendency of the system towards asymmetry model output demonstrates that during active frontal accretion to the pro wedge of an orogen the maxima in erosional denudation is offset towards the pro wedge relative to the maximum depths of exhumation this asymmetry is fundamentally driven by the progressive reduction in advection velocities of material within the orogen from the pro wedge into the retro wedge hence for an efficient erosional regime a dynamic coupling between erosion and structural uplift of the pro wedge will reduce activity of the retro wedge and hence drive asymmetry in terms of low temperature thermochronometry erosion and sedimentation the models also demonstrate the tendency for pro wedge growth through frontal accretion to slow however the cessation of frontal accretion as recorded by the south pyrenean thrust belt phases 3 and 4 requires additional forcing it is proposed that the thick wedge top sedimentation recorded at this time increased taper angles and hence stabilized the wedge accretionary influx into the orogen at this time was accomplished through underplating these processes governing asymmetry do not require a spatially variable climate or a laterally heterogeneous underthrust plate

mass balance for nd in the mediterranean sea abstract the mass balance for nd in the mediterranean sea has been assessed through the measurement of nd isotope ratios in particulates from rivers entering the mediterranean sea floor clays and ferromanganese crusts and samples of atmospheric dusts nd values for the po and rhone rivers respectively are 10 8 and 9 7 whereas the nile seyhan and tarsus have 3 3 6 2 and 6 3 sea floor clays and ferromanganese crusts range from 2 0 to 10 1 and dust samples vary from 8 2 to 11 0 the relatively radiogenic nd isotope composition of the mediterranean seawater ed 6 to 7 compared to the atlantic nd 12 reflects partial equilibration of the particulate input into the basin rather than merely the dissolved input

interplay between longitudinal fluvial and transverse alluvial fan systems and growing thrusts in a piggyback basin se pyrenees abstract the integration of sedimentological and structural data in the western end of the ripoll syncline allows a clearer understanding of the palaeogeography of the area between the oblique termination of the pedraforca thrust sheet and the frontal vallfogona thrust during middle eocene times in this region a 2 5 km thick clastic succession corresponding to the bellmunt and milany sequences infilled the ripoll syncline this succession evolved from fluvio deltaic to alluvial the long lived and west prograding longitudinal fluvio deltaic system was parallel to the axis of the syncline the fluvio deltaic deposits are found interfingered with others which correspond to transverse alluvial fans of northern provenance which are increasingly important towards the top of the section the persistent and uniform wsw palaeoflow direction of the fluvio deltaic system together with the position of open marine conditions to the south indicate that the southern boundary of the system was constrained by a tectonic barrier which is attributed to the emergence of the vallfogona thrust the ramp of this thrust above the foreland basin strata formed the ripoll piggyback basin from middle lutetian times on several millions years earlier than previously proposed the western end of the ripoll syncline is thus an example of a complex partitioning of a foreland basin over time and space by structures of differing growth duration and different trend the interaction of the oblique system of thrusts corresponding to the eastern termination of the pedraforca thrust sheet and the vilada anticline and the frontal system of the vallfogona thrust controlled the position of the bellmunt river dominated delta which acted as the outlet of the ripoll piggyback basin

seismic stratigraphy and deformational styles of the offshore cyrenaica libya and bordering mediterranean ridge off northwest libya the cyrenaica foreland basin domain and its pan african continental crust which constitute the african promontory are overthrusted by the mediterranean ridge complex the thrust belt contact and its seismic stratigraphy have been analysed using pre stack depth migrated multichannel seismic mcs lines recorded during the medisis survey 2002 the geometry and sedimentary distribution analysis through the wedge top depocentres allow reconstruction of schematic cross sections of the tectono sedimentary wedge that includes two major thrust sequences separated by an apparently poorly deformed transition zone based on time space variation of several piggyback basins we propose that these thrust sequences relate to distinct phases of shortening 1 a first event which probably occurred just prior to the messinian crisis in latest miocene tortonian times and 2 a second event that has finally led to the present day overthrusting of the mediterranean ridge over the libyan continental slope

episodic discrete and distributed deformation consequences and controls in a thrust culmination from the central pyrenees abstract the pic de port vieux culmination is a 0 5 km long thrust culmination in the footwall of the gavarnie thrust in the central pyrenees the culmination comprises a set of blind thrusts that imbricate a 50 m thick mesozoic cover sequence comprising triassic red beds and upper cretaceous limestone sandwiched between underlying hercynian basement and the overlying palaeozoic strata of the gavarnie thrust sheet an intense cleavage developed within the culmination associated with the oblique tip lines of the thrusts as they climbed from the basement into the cover strata detailed mapping shows that the distributed strain associated with the fault tips locally re activated earlier folded thrusts creating upper detachments to the system and produced a set of new overstepping isolated faults the main detachment occurred along the roof of the culmination using the back limbs of folds in the roof thrust the movement on these detachments can be demonstrated to have been episodic with periods of fault slip producing splays that were then folded during periods when distributed deformation was dominant the main control on this episodic deformation is modelled as the result of feedback between increase in fluid pressure associated with inelastic porosity reduction during cleavage development and fluid pressure bleed off associated with fault zone dilatancy in the culmination

crustal structure and orogenic material budget in the west central pyrenees surface and subsurface data are combined to construct a crustal scale cross section of the western central pyrenees france and spain at the boundary between the european and iberian plates the position of moho reflections in the ecors arzacq reflection profile suggests a tectonic wedge of european crust and upper mantle had indented the iberian plate at lower crustal levels the european wedge is overlain by an upper iberian wedge thus constituting a double stacked wedge geometry the upper wedge was delaminated and deformed giving rise to the pyrenean orogenic prism manifested as a bivergent fan in upper crustal levels the underthrust lower iberian plate has been imaged to depths of 55 60 km but crustal budget considerations based on a palinspastic reconstruction require that this continental root subducted to depths up to 90 km total orogenic contraction calculated from surface structures is about 75 80 km which was accomplished between the latest cretaceous and the early miocene at an averaged rate of 1 2 mm yr consistent with these moderate values exhumation of the orogen is much less than in the more shortened eastern parts of the range paleozoic basement and preorogenic mesozoic rocks are little eroded and much of the exhumation involved cannibalization of early foreland basins which once covered the entire poorly emergent orogen at this transect this resulted in a continuous process of sediment recycling and coupled with a considerable lateral arrival of material a bulk negative erosion sedimentation budget

pyrenean orogeny and plate kinematics 1 the evolution of the pyrenees a mountain range between iberia and eurasia has remained the subject of many debates between geologists and geophysicists for a long time by combining the identification of seafloor spreading anomalies a33o to m0 in the bay of biscay with those in the north atlantic we have derived a position of a mean pole of rotation for the entire opening of the bay of biscay four hundred kilometers of shortening took place between the iberian and eurasian plates in the pyrenean domain during the opening of the bay of biscay from chrons m0 to a33o time 118 to 80 ma the deep seismic etude continentale et oceanique par reflexion et refraction sismique ecors profile shot across the pyrenees and teleseismic data show the presence of two distinct slabs which dip to the north the southern slab is linked to the subduction of the neo tethys ocean which was created from late jurassic to early aptian simultaneously elongated back arc basins formed along the future pyrenean domain this slab was active from at least 118 ma early aptian to 100 ma late albian the northern slab active since 85 ma is linked to the subduction of the lower continental crust located south of the pyrenean domain in the upper crust normal faults as well as the north pyrenean fault became reverse faults and former back arc basins were inverted giving rise to the uplift of the pyrenees as a double asymmetrical wedge