paleogeographic and sedimentary evolution of the south pyrenean foreland basin abstract during the paleogene and neogene the ne iberian plate underwent significant paleogeographic changes driven by the iberian and european plate collision and the resulting formation of the pyrenean orogen and its corresponding foreland basin shortening resulted in the advance of the orogenic wedge emplacement of allochthonous units and progressive basin partitioning sediment transfer systems reacted to the evolving paleogeographic scenario shifting from forebulge to foredeep and wedge top settings critical reorganizations included successive shifts from open to close drainage conditions which had an strong impact on accommodation and the stratigraphic architecture of the basin infill overfill and later erosion the aim of this work is to synthesize the paleogeographic and sedimentary evolution of the south pyrenean foreland with emphasis on the reconstruction of sediment routing the evaluation of sedimentation rate trends the timing of sedimentary shifts and the analysis of their causes stratigraphic data are compiled in a comprehensive magnetostratigraphy based chronostratigraphic framework besides sedimentary and structural data are put together to produce a series of palinspastically restored paleogeographic maps which reflect five key stages in the evolution of the region these stages include 1 the late cretaceous tectonic inversion of the extended iberian margin 2 the early eocene formation of the southern pyrenean foredeep 3 the middle eocene widening and overfilling 4 the late eocene shift into an internal drainage and 5 the late miocene drainage opening and erosion in the light of these results the variable role of tectonics climate and eustacy at different time scales are discussed

sone megafan a non himalayan megafan of craton origin on the southern margin of the middle ganga basin india abstract researchers in the last few decades have focused on the fluvial megafans at the base of himalayan foothills in the ganga basin no major effort has so far been made to delineate any such large depositional environment at the base of the northern indian peninsular craton at the distal parts of the basin in this work for the first time we document a megafan unusually created by the cratonic sone river in the marginal plains south of the ganga the geomorphology of the megafan surface distribution of palaeochannels sedimentology and areal extent of the megafan are described the study also reconstructs the tectonic and palaeoclimatic conditions which might have helped in sediment supply from the cratonic catchment areas of the sone we suggest tectonic control over the sone river channel dynamics and development of the megafan the oval and fan shaped craton derived sediment body covers an area of around 12 000 km2 in the marginal plains and about 9000 km2 in the central alluvium north of the ganga river the megafan is around 190 km long and 240 km wide the mean slope of the megafan surface is 0 03 an onlap of himalayan sediments has occurred over the megafan at its toe parts caused by southward encroachment of the ganga during the holocene the megafan sediments comprise brownish yellow fine to coarse sand and gravels with an admixture of carbonaceous nodules kankars the thickness of the megafan sediment which directly overlies the precambrian basement varies from only a few meters in the south near the peninsular craton to 1000 m at the north in the central alluvial plain the granular zones form prolific aquifer systems in an otherwise poor hydrogeological setting of the marginal plains

tectonic classification of cenozoic iberian foreland basins abstract the iberian microcontinent stands out because of its intense alpine intraplate deformation this is reflected in a large number of cenozoic basins of very different sizes most of the contacts between topographic highs and basins are thrust or strike slip faults all these basins seem to have undergone a common sedimentary evolution comprising four stages initiation of sedimentation intense syn tectonic infilling change from endorheic to exorheic drainage and accelerated erosion related to fluvial incision this simple evolutionary model shows a migration from east to west in which basins are still tectonically active at the atlantic margin of iberia this common evolution is also found in a series of geometrical characteristics such as the ratio r of length of strike slip fault and length of thrust fault that are very similar in both types of basin border settings thrust related basins are mainly associated with segmented pop downs whereas the main basins have the characteristics of open ramp basins strike slip related basins are mostly transpressive structures although small pull apart basins are usual along the vilarica and messejana faults for basin areas larger than 100 1000 km 2 a constant r value of 0 6 is found including the ebro duero madrid lower tagus and badajoz basins within the iberian microcontinent the total amount of cenozoic contractional deformation was distributed between strike slip and thrust faults with an r ratio close to 0 6 however for small basins this parameter seems to depend on the type of fault range or deformation belt pure strike slip transtension transpression and pop up independently of its local tectonic development

modelling facies belt distribution in fan deltas coupling sequence stratigraphy and geostatistics the eocene sant llorenc del munt example ebro foreland basin ne spain abstract the eocene sant llorenc del munt fan delta complex developed in the ebro foreland basin the stratigraphy of this succession about 1000 m thick has been described as made up of several transgressive regressive composite sequences each composed of a stack of fundamental sequences in turn made up of a transgressive systems tract and an overlying regressive systems tract systems tracts are composed of several facies belts proximal alluvial fan distal alluvial fan fan delta front carbonate platform and fan delta slope and prodelta a 3d facies model of a 130 m thick stratigraphic succession was built using outcrop data from one of the composite sequences the modelling followed a hierarchical approach a deterministic method was used to reconstruct the surfaces bounding fundamental sequences and their constituent systems tracts data input was outcrop traces digitized on photorealistic terrain models the stacking trend and interfingering of adjacent facies belts within each systems tract was added by means of a geostatistical algorithm and was conditioned to measured stratigraphic logs the analysis of the resultant 3d facies distributions allows revising the architectural interpretation of the studied interval leading to the conclusion that the observed arrangements are accommodation not supply driven furthermore the 3d models were flow simulated in two injector producer scenarios up depositional and down depositional dip waterflooding flow simulation results show that the depositional architecture of the studied succession controls potential recovery efficiencies in that a considerable proportion of moveable oil is trapped at the dead ends in depositional pinch outs of the main potential reservoir fan delta front deposits also that up dip waterflooding predicts better recovery efficiencies than down dip the dataset methods and results herein make the sant llorenc del munt complex a ready for application analogue for marine transitional reservoirs

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

milankovitch forcing of bioturbation intensity in deep marine thin bedded siliciclastic turbidites abstract trace fossils have been used to infer a milankovitch type control on pelagic and hemipelagic sediments but there have been no comparable studies in deep marine siliciclastic turbidite successions here we present the results of a quantitative analysis of trace fossil abundance and intensity in an essentially continuous middle eocene 230 m long well a6 core comprising very thin and thin bedded siliciclastic turbidites in the deep marine ainsa basin spanish pyrenees after removing the sediment slides and debris flow deposits as these represent geologically instantaneous events approximately two orders of magnitude thicker than the typical laminated turbiditic sediments in the core spectral analysis was conducted on the bioturbation intensity data spectral analysis of bioturbation intensity in the a6 core suggests for the first time from a siliciclastic turbidite succession at a tectonically active plate margin thrust top basin in a foreland basin a cyclicity that is interpreted to reflect the 41 kyr and an 112 kyr possibly an average of the 95 and 125 kyr milankovitch frequencies we propose that this drove environmental changes in bottom water conditions in the ainsa basin most likely leading to critically varying levels of oxygenation stratification of bottom waters our age model for the ainsa basin 4 km of deep marine sediments in 10 myr yields an average sediment accumulation rate of 40 cm kyr 1 that is consistent with that inferred from the spectral analysis 30 cm kyr 1 for fine grained sedimentation an implication of these results is that global environmental change probably glacio eustasy acted as a driver on deep marine siliciclastic sedimentation patterns during the middle eocene

ten million year history of a thrust sheet the final deformed state of a fold and thrust belt may be reached by an infinite number of kinematic paths two end member kinematic paths are due to continuous or discontinuous rates of deformation we have used a new magnetostratigraphic section from the spanish pyrenees to calibrate the emplacement history over 10 m y of a major thrust sheet the sierras marginales thrust sheet and the deformation of both its hanging wall and footwall six time windows from before 36 5 ma until after 24 7 ma were recognized on the basis of structural and stratigraphic relationships between syntectonic strata and major structures footwall deformation of the sierras marginales thrust sheet occurred continuously on a detachment within the foreland basin sequence 4 5 km net shortening shortening rates steadily increased from 0 14 to 1 5 mm yr with time although the detachments at the base of the foreland and the detachment at the base of the sierras marginales thrust sheet were active coevally the rate of displacement on the sierras marginales detachment decayed with time and shows considerable variability emplacement of the thrust sheet may be divided into three distinct periods a rapid 13 8 km translation from 37 0 to 36 5 ma 27 6 mm yr a gradual climb of the toe of the thrust sheet up a 4 3 km long ramp across the foreland basin succession from 36 5 to 32 0 ma 0 95 mm yr and a final 8 9 km translation from 32 0 to 29 5 ma 3 56 mm yr internal deformation of the thrust sheet occurred only after it reached its present position at some time before 29 5 ma shortening rates steadily decreased from 0 6 mm yr between 29 5 and 27 8 ma to 0 26 mm yr from 27 8 until after 24 7 ma only 1 km of shortening accumulated during each of the two periods the last shortening localized on the most northerly thrust in the study area folding and subsequent faulting above the detachment beneath the foreland suggest that slip was transmitted to its tip point continuously throughout the deformation in contrast translation followed by internal deformation on the hinterland side of the toe of the sierras marginales thrust sheet indicates a successive deactivation of the southern parts of the detachment with time rate of deformation on both detachments was discontinuous and shows substantial variability about the mean in general the spatial and temporal pattern of deformation was distributed and continuous in detail however shortening was spatially and temporally discontinuous above each detachment and structures related to each one display distinctly different deformational patterns rates and styles

coeval hindward and forward imbricating thrusting in the south central pyrenees spain timing and rates of shortening and deposition clear demonstrations of detailed sequences of thrust development are rare particularly with respect to hindward imbricating successions similarly well constrained chronologies of the timing of multiple thrust motions and associated rates of shortening are also uncommon along the eastern oblique ramp of the south central unit scu of the pyrenees well exposed structural geometries and crosscutting stratigraphic packages unambiguously illustrate a sequence of break back thrusts that developed synchronously with the growth of an adjacent duplex the break back sequence includes both the sierras marginales and montsec thrusts structures defining two of the major east west partitions within the scu balanced sequentially restored structural cross sections indicate that a minimum of 7 5 km of shortening occurred within the imbricate stack an additional 9 km of contraction was accommodated by the duplex prior to translation of the duplex and imbricate stack to the south along a detachment within upper eocene evaporites magnetic polarity stratigraphies have been used to calibrate these late eocene to oligocene episodes of deformation these temporal data indicate that sierras marginales thrusting began in the study area 39 8 ma and that the montsec thrust ceased movement 36 2 ma yielding a mean rate of shortening of 2 1 mm yr coeval shortening within the duplex was 2 5 mm yr and subsequent translation across the footwall ramp occurred at 2 5 4 mm yr despite the partitioning of shortening into distinctively different styles of deformation the mean rate of contraction remained steady over 4 m y these new chronologies indicate that the locus of large scale thrusting did not progress systematically toward the foreland but shifted episodically within the scu such that during the late eocene shortening the sierras marginales thrust was active both prior to and south of the montsec thrust

consequences of foreland basin development on thinned continental lithosphere application to the aquitaine basin sw france abstract we present an analysis of the consequences of foreland basin development on thinned continental lithosphere inherited from pre orogenic phases of extension bathymetry at the transition from pre orogenic extensional basin to foreland basin and compaction of pre orogenic sediments contribute to the accommodation space for foreland basin sediments and thrust loads in addition the extension induced transient thermal state of the lithosphere results in ongoing thermal subsidence and a flexural rigidity which changes through time quantitative modelling of the phase of extension and the foreland basin stage of the aquitaine basin southern france shows that the inherited transient thermal state of the lithosphere contributes significantly to 1 the total foreland basin depth and width 2 the post compressional subsidence history and 3 the cratonward onlap pattern accounting for the thermo mechanical effects of pre orogenic extension significantly reduces the estimates of both the flexural rigidity 30 43 for the aquitaine basin and the required topographic or thrust load 40 for the aquitaine basin at foreland basins emplacement of thrust loads below sea level as expected in a pre orogenic extensional basin setting further reduces the required topographic load this sheds light on the wide range of flexural rigidity values reported for continental lithosphere from foreland basin modelling studies and explains in many instances the inferred hidden load or subsurface load in flexural modelling studies at foreland basins the present study has shown that pre orogenic extension phases significantly affect the record of vertical motion and the stratigraphy of the aquitaine basin and is probably important for foreland basin evolution in general

fluid history related to the alpine compression at the margin of the south pyrenean foreland basin the el guix anticline the el guix anticline is the southernmost structure of the south pyrenean fold and thrust belt ne spain compressional activity in the area represents the latest stages of alpine compressional tectonics and avects the upper eocene oligocene fluvio lacustrine deposits overlying an evaporite sequence the evolution pattern of the fractures containing calcite cement consists of three stages of microfractures which reflect the evolution of the structure and the relationships between fluids and thrust development in each fracture deformation started with a network of discontinuous microfractures which acted as traps for local meteoric fluids stage 1 during the second stage dilatant thrust faults serving as the conduit for both evolved meteoric ascending and local meteoric fluids were developed migration of fluids through the thrusts was multiepisodic after the precipitation of cements in microfracture stage 2 the thrusts were practically occluded by calcite cements acting as fluid barriers and dividing the structure into diverent hydrological compartments the last stage of microfracture stage 3 is attributed to a younger phase where the circulation of fluids concerned only meteoric fluids and the previously formed fractures acted as barriers to fluid circulation meteoric fluids with high fe mn and fe mg ratios without na and sr enriched with 13c and with low 87sr 86sr with respect to their host rock were widely distributed in the structure throughout all its evolution within a relatively open palaeohydrological system evolved meteoric fluids with lower fe mn and fe mg ratios with na and sr depleted in 13c and with high 87sr 86sr with respect to their host rock were only present during thrust faults development stage 2 within a relatively closed palaeohydrological system the underlying evaporites acted as the lower boundary of the aquifer comparison with older thrust fronts of the same system reveals that the pyrenean fold and thrust belt and its deformed southern foreland basin were compartmentalised hydrologically in time and space during the early eocene when the thrust front avected soft sediment in the ainsa basin the thrust faults were dominated by a medium scale fluid flow the fluids in the basin were basically formation fluids derived from eocene marine waters trapped in the underlying eocene marls although influences of meteoric waters were also present during the middle eocene coeval with the gavarnie thrust emplacement the thrust fault was dominated by a medium scale fluid flow the fluid was basically a hypersaline sr rich brine stored within triassic redbeds no evidence of a significant input of either surface or metamorphic fluids during thrusting was found during the same period in the crystalline basement of the central pyrenees the thrust faults were dominated by a large scale fluid flow mainly derived from the underlying silicate rocks

source rock potential of an eocene carbonate slope the armancies formation of the south pyrenean basin northeast spain abstract the armancies formation is an eocene carbonate slope succession in the catalonian south pyrenean basin it ranges from 500 to 700 m in thickness the first 200 m are made of a thin bedded facies of wackestones alternating with dark pelagic fauna of miliolid ostracods bryozoans and planktonic foraminifers and show significant bioturbation they also show a low organic content 0 5 toc the lime mudstone beds show a massive structure or planar millimeter laminations they may contain sparse pelagic fossils of planktonic foraminifers ostracods and dinoflagellates they do not show any bioturbation and have high toc values which can reach individual scores of about 14 they qualify therefore as a typical oil shale rock eval pyrolysis analysis affords a mean s sub 2 value of 25 mg hc g mean s sub 1 value is around 1 0 mg hc g as is typical of an initial oil window t sub max maturity parameter ranges from 432 to 440 degree c mean 434 degree c this degree of evolution is in accordance with the very low value of carbonyl and carboxyl groups as determined by ir spectrometry and nmr on fischer assay extract the proton nmr shows an aromatic aliphatic hydrocarbon ratio of 1 4 as expected in earlier stages of catagenesis n alkanemore gas chromatography profiles show n c sub 15 to n c sub 19 prevalence and that neither even nor odd carbon numbers prevail this distribution perfectly matches that of typical sediments of marine origin and also agrees with obtained hydrogen index values mean hi 500 mg hc g toc sedimentological and geochemical results indicate an autochthonous marine organic matter and the potential of these slope shales is good oil prone source beds less

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

a complete terrestrial oligocene magnetobiostratigraphy from the ebro basin spain abstract the integrated litho bio and magnetostratigraphic cross correlation of 11 continuous and correlatable sections in the southeastern ebro basin ne spain produced a complete oligocene magnetic polarity stratigraphy ranging from latest eocene to earliest miocene the magnetic polarity zonation of the different alluvial and shallow lacustrine sections has been correlated to the gpts using fossil mammals and the distinct sequence and pattern of polarity reversals the composite magnetic polarity sequence defines a continuous sequence from chron c15n to chron 6cn 2n from 34 8 to 23 7 ma late eocene early miocene in addition a few short normal and reverse polarity events that correlate to cryptochrons in the gpts are found i e in c11n 1r and c8n 1r the resulting regional magneto biostratigraphic framework based on fossil mammals is proposed to refine the dating of the european oligocene biochronological mammal paleogene units and correlate them with the standard oligocene marine stages and the north american land mammal ages the magnetochronology now established enables more precise dating of the late eocene and oligocene paleofloristic and paleofaunistic changes in southwestern europe which were coeval to ongoing global paleoclimatic and paleoceanographic changes on earth caused by high latitude cooling and ice sheet development in eastern antarctica

from hydroplastic to brittle deformation controls on fluid flow in fold and thrust belts insights from the lower pedraforca thrust sheet se pyrenees abstract we present a multidisciplinary study to decipher the controls of deformation on fluid flow regime in fold and thrust belts using the lower pedraforca thrust sheet in the se pyrenees as an example we integrate field based and petrographic observations and geochemical and geochronological data to differentiate seven types of fractures eight types of calcite cement cc1 to cc8 and two sets of stylolites during the deformation stretching the studied thrust sheet during syn sedimentary hydroplastic normal faulting affecting poorly consolidated upper cretaceous and eocene syn orogenic sediments calcite cement did not precipitate during burial bed parallel stylolites formed and cc1 and cc2 precipitated from formation waters in a closed palaeohydrological system during the layer parallel shortening cc3 precipitated from formation waters 5 4 vsmow with 87sr 86sr ratios of 0 707922 and at 70 c cc4 precipitated from formation waters recording different burial conditions as the up to 4 dispersion in 18o of this cement suggests contrarily during folding and thrusting cc5 to cc7 precipitated in an open palaeohydrological system cc6 precipitated from formation waters 5 vsmow with 87sr 86sr ratios of 0 707817 and at 75 c these fluids carried hydrocarbons and probably interacted with upper triassic evaporites an 87sr 86sr ratio of 0 708230 for cc5 indicates that formation waters also interacted with clays within continental deposits during this period stylolites formed in relation to faulting and previous hydroplastic normal faults reactivated as reverse and strike slip faults allowing fluid flow cc7 precipitated after cc6 also from fluids in isotopic disequilibrium with their adjacent host rock the fluid system continued open during the oligocene when cc8 precipitated in normal faults affecting syn orogenic conglomerates deposited during the reactivation of the lower pedraforca thrust sheet the influence of deformation on fluid flow observed in the lower pedraforca thrust sheet is similar to that observed in other fractured areas worldwide

platform sedimentation and collapse in a carbonate dominated margin of a foreland basin jaca basin eocene southern pyrenees the eocene jaca basin is a foreland basin with well exposed carbonate platforms in the distal margin this margin underwent alternating periods of stable platform growth and platform drowning periods of drowning were accompanied by large scale collapses with generation of shelf edge truncations and resedimentation of carbonate megabreccias into a terrigenous turbiditic trough these features caused a stepped retreat of the platforms and are related to episodic variations of tectonic loading in the hinterland and correlative flexural bending of the distal basin

origin of a thick redeposited carbonate bed in eocene turbidites of the hecho group south central pyrenees spain large scale carbonate beds interbedded in basin plain turbidites of the eocene hecho group northern spain are interpreted as giant turbidity current deposits because of their internal organization and lateral extent one such bed the roncal unit has been traced down the axis of the basin for 75 km and commonly reaches thicknesses in excess of 100 m internally the roncal unit displays an overall upward decrease in grain size from a basal megabreccia with large slabs of carbonate platform debris to a calcareous mudstone the roncal unit was probably deposited from a highly mobile and competent sediment gravity flow generated by an earthquake shock which led to the catastrophic collapse and subsequent transport of the upper part of a carbonate platform flanking the basin

kinematic retro modelling of a cross section through a thrust and fold belt the western irish namurian basin the western irish namurian basin winb developed into a fold and thrust belt at the front of the northward propagating variscan orogenic wedge part of this basin is well exposed along the coast of county clare ireland from a detailed study that used an integrated gps mapping approach we produced a c 50 km long balanced cross section parallel to the tectonic transport vector we sequentially decompacted and retro deformed the namurian strata in 7 stages to evaluate the palinspastic situation of the basin and the amount of shortening by using passive markers in the model and a highly detailed timescale we were able to determine that shortening of the winb from the onset of central clare group sedimentation was 7 44 or 4 07 km of which shortening due to folding accounts for c 2 64 c 1 37 km and therefore c 4 80 c 2 69 km was solely because of thrusting the rate of horizontal shortening ranges from 1 34 mm a 1 this is within typical orogenic values

constraining the onset of flexural subsidence and peripheral bulge extension in the miocene foreland of the southern apennines italy by sr isotope stratigraphy abstract in fold and thrust belts developing at convergent margins the migration of the advancing wedge is accompanied by bulging of the downgoing plate followed by the development of a foredeep basin filled by a thick succession of syn orogenic sediments the transition from forebulge to foredeep marks a key moment in the evolution of the orogenic system in deep water environments the record of this transition is typically complete and progressive conversely in the shallow water continental environment of many collisional systems the uplift of the forebulge area can imply emersion and erosion obliterating the stratigraphic record of key steps of the evolution of the orogenic system the southern apennines constitute one of these collisional fold and thrust belts where the development of the forebulge has implied emersion and erosion with the development of a miocene forebulge erosional unconformity accompanied by extensional deformation associated with the bending of the lithosphere during the forebulge stage in this paper we use strontium isotope stratigraphy to constrain with unprecedented time resolution the age of the forebulge unconformity in areas presently incorporated in the northern sector of the southern apennines fold and thrust belt integration of our results and those of previous studies indicates at the regional scale a younging toward the foreland of the forebulge unconformity across the belt our high resolution ages also reveal a diachronous onset of the flexural subsidence over short distances associated with the occurrence of horst and graben structures possibly resulting from inherited paleotopography along with forebulge extension this work highlights how high resolution dating is critical to unravel the evolution of foreland basin systems at different scales

evolution of a turbiditic foreland basin and analogy with an accretionary prism example of the eocene south pyrenean basin the south pyrenean tertiary basin was an east west trending foreland trough which developed from early eocene to miocene times in a north south trending compressive regime a turbiditic series of lower and middle eocene age hecho group enables us to define the typical features of the tectono sedimentary evolution of the basin 1 slope and shelf derived carbonate turbidites and megaturbidites bear witness to the seismic activity of the basin borders 2 the southern basin border evidenced by the onlap of the turbidites onto slope and shelf deposits migrated progressively southwards in time and 3 the deformation pattern is characterized in the meso cenozoic sediments by a complex thrust fold system of thin skinned tectonics style its specific geometry and kinematics were influenced by the pre deformation geometry onlap this thrust fold system is related to south directed basement nappes and its front advanced progressively southwards in time from this data we infer an evolutionary model for this highly mobile basin it was a flexural basin linked to the northward bending of the lithosphere in the foreland of a south directed crustal accretionary prism as the nappes advanced the basin migrated progressively southwards in the foreland direction as for the actual basin evolution many analogies with accretionary prism trench systems of active margins exist

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

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

cenozoic vertical motions of the catalan coastal ranges ne spain the role of tectonics isostasy and surface transport 1 we analyze the cenozoic topographic evolution of the catalan coastal ranges ne spain and the role of fault activity erosion sedimentation and isostasy in controlling uplift and subsidence a forward numerical model constrained by an extensive geological and geophysical data set is used to examine the temporal and spatial record of cenozoic vertical motions we show that the effect of isostasy erosion and sedimentation is as important as the contribution of fault deformation to the topography of the catalan coastal ranges the model predicts that paleogene topography generation by thrusting was compensated by erosion up to 1 3 km and isostatic subsidence up to 1 2 km resulting in a 1 2 1 9 km high mountain range by the end of compression 29 ma during the neogene strong tectonic subsidence related to normal faulting and the consequent flexural uplift of 0 7 1 2 km surface erosion as much as 1 6 2 3 km and sedimentation up to 4 5 km led to the present landscape configuration extension rates along the barcelona fault controlled flexural uplift and in combination with erosion and sedimentation processes led to the migration of the topographic maximum of the prelitoral range toward the easternmost ebro basin

megabreccia shedding from modern low relief carbonate platforms nicaraguan rise single channel seismic reflection data from the margins of lowrelief 150 250 m measured from edge of bank to basin carbonate platforms on the northern nicaraguan rise reveal complex seismic intervals consisting of mounded chaotic seismic facies interspersed with discontinuous parallel laminated seismic facies we interpret that these intervals contain megabreccias chaotic facies and sandy turbidites parallel laminated facies one megabreccia is exposed on the sea floor displaying an overall fan shape having individual blocks measuring nearly 300 m across and 110 m high the source area consists of a scalloped embayment with a headwall scarp 180 m high reflections within the platform are sharply truncated by this escarpment this single megabreccia is 120 m thick and extends 27 km along slope and 16 km out into the basin other megabreccias within the basin have individual blocks measuring 400 m across rocks from dredge hauls are a mixture of shallow and deep water facies shallow water facies consist of mixed skeletal grain stones and halimeda packstones deep water facies are massive chalks chalks with shallow water skeletal grains and chalk block breccias this indicates that the megabreccias formed as a result of bank margin collapse during which the ensuing debris flow eroded into slope and basin facies mixing rock types together we speculate that bank margin collapse events resulting in megabreccia formation may have been seismically triggered and we emphasize that these large scale mass wasting events occurred along margins of low relief carbonate platforms

foreland basin subsidence driven by topographic growth versus plate subduction the subsidence of foreland basins is classically thought to accelerate with time however a synthesis of data from numerous foreland basins recognizes a wide range of signals and rates our analysis investigates the influence of two broadly ubiquitous controlling factors 1 the upward and outward growth of mountain topography and 2 the subduction velocity of the underthrust lithosphere these two factors have contrasting subsidence signals the former tends to be slow and decelerates while the latter is more rapid and accelerates the geodynamic setting of a foreland basin determines the degrees to which these components dominate the final signal of tectonically induced subsidence in small collisional mountain ranges the common asymmetry of subduction defines a pro and a retro foreland basin based on model experiments and the synthesized data we demonstrate that pro foreland basins exhibit short lived usually 0 05 km m y 1 accelerating subsidence histories recording only a portion of the orogenic history of the mountain range type examples are the carpathian foredeep and the north alpine foreland basin in contrast retro foreland basins are characterized by relatively slow 0 05 km m y 1 protracted usually 40 m y subsidence that records the majority of the orogenic history a good example is the aquitaine foreland basin retro arc foreland basins such as the alberta basin appear comparable to collisional retro foreland basins examples where there is more protracted subsidence appear to record greater evidence of episodic loading and unloading as the topography of the range grows or shrinks in response to the balance between crustal thickening and erosion rates

growth strata in foreland settings abstract the accurate analysis of growth strata has revealed their significance to unravel both fold kinematics and timing of deformation in both compressive and extensive settings the increasing acquisition of 3 d multichannel seismic lines with few tens of meters of resolution in complex tectonic areas reveals complex interplay between growing structures and deposition either in marine or continental environments interestingly growth strata reveal similar relationships in both compressive folds linked to thrusts at depth and folds related to propagating normal faults in extensive regimes to completely document the complete kinematic history of an individual fault or a group of faults it is necessary to combine studies at different scales to integrate the findings revealed by field work meters of resolution and multichannel seismic lines results the margins of the ebro basin to the south of the pyrenees have been the focus of abundant studies of syntectonic deposits this is because of its special long term evolution from a foreland to an intermontane basin and a final open basin to the mediterranean sea in neogene times the complete comprehension of growth strata in these natural laboratories is essential for our present needs in both petroleum exploration and earthquake prediction

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

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

the chronology of the eocene tectonic and stratigraphic development of the eastern pyrenean foreland basin northeast spain abundant and clearly exposed relationships between structures and syntectonic sedimentary rocks in the southern pyrenees make this area particularly suitable for detailed studies of the sequential development of a collisional orogenic belt during the pyrenean orogeny major shortening occurred in the eastern pyrenees in eocene and early oligocene times until now individual tectonic and depositional events have been only loosely defined temporally by biostratigraphic data in order to provide a more precise chronological framework four new magnetostratigraphic sections spanning 8 km of eocene strata and encompassing 18 m y have been developed in the eastern pyrenees of northern spain the ages of nine major depositional sequences in the eastern pyrenean foreland have been specified within the context of these chronologic data beginning with the early eocene transgression that commenced at 58 ma the timing of numerous tectonic events that occurred during the subsequent 16 m y can also be delineated including the initial emplacement of the pedraforca thrust sheet 58 54 ma the development of the pedraforca breakback thrusts 47 5 40 ma at a mean shortening rate of 2 4 mm yr rotation of the pedraforca footwall three intervals of motion along the vallfogona thrust 42 5 44 0 40 5 41 5 and

basin infill architecture and evolution from magnetostratigraphic cross basin correlations in the southeastern pyrenean foreland basin magnetostratigraphy numerical dating and facies mapping have been combined to provide the first cross basin correlation of the eocene southeastern pyrenean foreland basin in northeastern spain this has enabled 1 depositional systems on the northern and southern margins of the basin to be dated and correlated across the basin and 2 changes in the rates of sediment accumulation in time and space to be evaluated by sampling correlative intervals at several locations in a transect across the basin magnetozones were detected that otherwise may have been misinterpreted due to recent magnetic overprinting or missed by wide sampling intervals in previous magnetostratigraphic surveys results of this study indicate that marginal marine strata of the southeastern part of the foreland near the vic area of spain are 5 m y older than previously thought the base of the interval 46 ma being middle lutetian in age by proposing an age of at least 35 68 ma for the overlying cardona evaporite unit the age span of the marine interval in the studied part of the foreland is 10 m y contrary to earlier interpretations no major southward migration of the southeastern pyrenean foreland basin depocenter is recorded by the basin stratigraphy during the initial stages of middle eocene marine sedimentation in the southern margin of the basin however marked basin asymmetry is observed later in its evolution as the top of the marine deposits records northward increase in the thickness of chron c17n 1n 37 47 36 61 ma this asymmetry is also proved by the presence of a larger number of magnetozones within marine strata at the top of the marine interval in the northern sector these results imply that previous age calibrations and the estimated rates of tectonic processes and sedimentation within the foreland need to be reassessed the implications for basin infill architecture evolution through time and space subsidence analysis and depocenter evolution through time are addressed

the anso transect of the southern pyrenees basement and cover thrust geometries a balanced geological section through the western central pyrenees allows the alpine geometry of hercynian basement to be determined this shows marked differences with other transects of the southern part of the chain basement involved thrust sheets do not form an antiformal stack but are imbricated and define steps separated by frontal culmination limbs basement thrusts propagate upwards and have formed distinct thrust systems in the cover in this transect the north pyrenean zone is bounded to the south by gently dipping thrusts of large displacement and the axial zone massif at its western termination area is a flat topped culmination caused by a single thrust fault the gavarnie thrust this thrust emerges to the south in the interior of the syntectonic jaca basin the geometry of which is also controlled by underlying basement thrusts various generations of structures can be correlated with distinct episodes of syntectonic sedimentation a sequential restoration of the section illustrates how successive foreland sedimentary wedges were generated and progressively involved in deformation tectonic shortening is 48 km almost half of that estimated further to the east for the southern pyrenees the structure deduced at the ecors pyrenees seismic section cannot be translated to this transect

braided stream and flood plain architecture the rio vero formation spanish pyrenees early to middle miocene fluvial sandstones of the rio vero formation were studied in an area around the town of barbastro south central pyrenees spain the outstanding quality of outcrops in this area allows a three dimensional study of architectural elements six architectural elements are recognised described in detail and interpreted from three key localities seven main lithofacies were identified and sub divided into gravelly sandy and fine grained lithofacies the architectural elements and lithofacies have been combined with a hierarchy of depositional bounding surfaces to fully interpret the evolution of the depositional system at the meso and macro scale not only the different architectural elements and lithofacies of the complete braided fluvial system but also the lateral variation of the architectural elements were emphasised in this study differential tectonic movements seasonal climate change and their effect on vertical and lateral evolution of the area were the main control on basin sedimentation channel interconnection palaeocurrent patterns and consequently the fluvial architecture the presence of lateral ramp anticlines caused the fluvial system to be laterally restricted with the main channel belts being located in the areas of highest subsidence and lowest topography intervening topographic highs acted as both flood plains and lateral barriers between the main channel systems the proposed depositional model comprises broad low sinuosity perennial but seasonal moderate energy streams the sandstone architecture is dominated by channel fill and sheet sands and associated simple and more complex bars adjacent to the main channel belts fine grained sandstones siltstones and immature paleosols occur the along strike relationship between major fluvial systems and their outlets into a foreland basin has important implications for the infill of the basin and the modelling of fluvial systems along mountain belt fronts

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

thrust loads and foreland basin evolution cretaceous western united states two dimensional modeling of loading during the formation of the idaho wyoming thrust belt shows that regional isostatic compensation by flexure of an elastic lithosphere is sufficient to control the formation of a foreland basin the flexural rigidity of the lithosphere is inferred to have been approximately 1023 nm 1030 dyne cm on the basis of palinspastic comparison of predicted downwarping due to the thrust plate loads to the shape of the sedimentary wedge on the west side of the cretaceous western interior seaway erosion of part of the uplifted thrust plates redistributed the load depositing it farther to the east thereby causing subsidence over a much wider area than could have been accomplished only by the loading by thrust plates paleotopography after major cretaceous thrust events was calculated the resulting mountainous terrain gentle alluvial plain and flat sea floor correspond well with the topography of the modern foreland thrust belt and basin system in the andes of south america and to paleogeographic reconstructions in the western united states thrust belt topography is controlled by the subsurface geometry of the thrust faults particularly the positions of ramp zones and by isostatic subsidence

stratigraphic modeling of foreland basins interpreting thrust deformation and lithosphere rheology the authors incorporate the processes of erosion and deposition in a numerical model to predict the stratal geometries and facies patterns produced during episodic thrusting in a nonmarine foreland basin the resultant stratigraphic record is characterized by a stairstepped facies package in which each retrogradation of facies toward the thrust marks the onset of a thrusting event the retrogradation of facies coincides with the migration of the forebulge toward the thrust and the generation of an erosional unconformity in the past changes in basin wavelength during basin evolution have been interpreted to record viscoelastic relaxation of the lithosphere this model suggests that changes in basin wavelength are a natural consequence of the interplay between thrust and sediment loading on an elastic lithosphere

evaluation of groundwater potential in kabirwala area pakistan a case study by using geophysical geochemical and pump data knowledge of hydraulic parameters hydraulic conductivity and transmissivity is essential for the delineation of groundwater potential zones conventionally these parameters are measured using pumping tests carried out on boreholes however pumping tests are costly labour intensive and require a considerable amount of equipment the integration of geophysical methods with pumping tests provides efficient and cost effective alternative to calculate hydraulic parameters fifty electrical resistivity soundings were carried out in the study area using schlumberger interelectrode configuration to obtain hydraulic characteristics that are estimated through the pumping tests to apply this approach successfully sufficient number of boreholes are used part of the boreholes in which pumping tests were carried out is used for both to constrain resistivity inversions and to establish the empirical relationship between the interpreted geophysical and hydraulic parameters the rest of the boreholes without pumping tests are still used for constraining the inversions initially aquifer parameters were measured using pumping tests at 12 water wells afterwards transmissivity t and hydraulic conductivity k were correlated with transverse resistance tr and the bulk resistivity o of the aquifer at other sites where pumping tests had not been conducted in this way the entire study area was covered to assess the groundwater reserves the hydraulic properties obtained by the geophysical method fit pretty well to both the pumping and physicochemical data of the investigated area the integrated study reveals five layers i e topsoil clay clay sand sand and gravel sand and three potential zones i e high medium and low potential aquifer zones with specific ranges of t k tr and o the results suggest that in case of sparse well data the aquifer parameters can be estimated using the relations depending on the specifications of the area

two phase stratigraphic model of foreland basin sequences application of flexural models to nonmarine foreland basin evolution indicates that two different stratigraphic styles of basin fill may develop over time basin subsidence is most rapid during times of thrust load emplacement associated sedimentation is coarse grained immediately adjacent to the thrust front and grades rapidly into fine grained deposits that cover most of the basin the distal part of the basin may also contain deposits derived from streams that flow from beyond the basin toward the thrust belt subsequent removal of the thrust load by erosion and other processes results in flexural rebound of the thrust belt and adjacent foreland basin during this postorogenic phase of adjustment a regional unconformity develops in the proximal part of the foreland basin proximal deposits along with thrust derived sediment are redeposited in the distal foreland basin and beyond this two phase model of foreland sedimentation predicts that coarsening upward sequences in the proximal and distal parts of the basin have reciprocal significance the proximal sequence represents thrust belt advance whereas the distal sequence represents thrust belt cessation

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

large scale stratigraphic architecture eustatic variation and unsteady tectonism a theoretical evaluation we incorporate a process based depositional model with basin subsidence models to predict stratigraphic records this allows us to investigate the importance of subsidence geometry on coastal stratigraphy and thus to characterize and compare the stratigraphic architecture of two categories of tectonic basins the models demonstrate that the correlation of stratigraphic sequences to eustatic cycles is not the same in passive margin basins as in foreland basins and that in a foreland basin the record of episodic tectonism is distinct from that of eustatic sea level change in the model sediment transport is approximated by slope controlled diffusion nonmarine transport is treated as more efficient diffusion than marine transport three different subsidence and sediment supply models are examined a simple passive margin basin a simple foreland basin and then a foreland basin for which vertical motions are driven by thrust shortening that is compensated flexurally and for which sediment supply is related to relief predicted passive margin stratigraphies for cases of varying eustatic sea level are similar to those of natural basins and include progradational packages and subaerial unconformities which are used to define sequence boundaries that form during sea level fall we explore the timing relationships between stratigraphic features and a sinusoidal sea level history showing that the phase relationship depends on subsidence sediment flux efficiency of sediment transport and period and amplitude of sea level when the basic geometry of the basin is inverted placing the sediment supply on the side with maximum subsidence as is the case in foreland basins the sequence character changes markedly subaerial erosion does not generate unconformities in the models of a dynamic foreland basin sediment supply and subsidence are linked to the structure of the flanking thrust belt and are not necessarily constant for steady thrusting and variable sea level unconformities that define sequence boundaries form only on the distal or forebulge side of the basin and the ages of the sequence boundaries correlate to limes of rising sea level in cases of constant sea level but variable thrusting subaerial unconformities are cut locally on both the proximal margin of the basin and the distal margin of the basin yet the ages of the proximal margin and distal margin unconformities are out of phase in the tectonic cycle erosion is most pronounced during quiescence on the proximal side and during thrusting on the distal side

plate tectonics and basin subsidence history tectonic setting exerts fi rst order control on basin formation as refl ected in basin subsidence history while our approach ignores the effects of fl exural loading and eustatic sea level change consistency of backstripped subsidence histories i e with local loading effects of sediment removed suggests consistent tectonic driving mechanisms in each tectonic setting with the possible exception of forearc basins based on published subsidence curves and open fi le stratigraphic data we show the subsidence characteristics of passive margins strike slip basins intracontinental basins foreland basins and forearc basins passive margin subsidence is characterized by two stages rapid initial synrift subsidence and slow post rift thermal subsidence with increasing subsidence rates toward the adjacent ocean basin subsidence of intracontinental basins is similar in magnitude to that seen in passive margin settings but the former is generally slower longer lived and lacks initial subsidence long lived subsidence for many intracontinental basins is consistent with cooling following thermal perturbation of thick lithosphere found beneath old parts of continents basins associated with strike slip faults are usually short lived with very rapid subsidence changes in local stress regimes as strike slip faults evolve and migrate over time coupled with three dimensional heat loss in these small basins likely explain this subsidence pattern foreland basin subsidence rates refl ect the fl exural response to episodic thrust loading resultant subsidence curves are punctuated by convex up accelerating segments forearc basins have the least consistent subsidence patterns subsidence histories of these basins are complex and may refl ect multiple driving mechanisms of subsidence in forearc settings second order deviations in subsidence suggest reactivation or superimposed tectonic events in many basin settings the effects of eustatic sea level change may also explain some deviations in curves for many of these settings subsidence histories are suffi ciently distinctive to be used to help determine tectonic setting of ancient basin deposits

the late quaternary sedimentary record of stave lake southwestern british columbia the postglacial sedimentary record of 59 km2 stave lake was investigated using 3 5 khz subbottom profiles and cores from the sediment surface the acoustic data show a thin cover of acoustically transparent sediment unit 1 overlying bedrock or glacial sediment on the floor of the lake overlying acoustically stratified sediment is divided into unit 2 which thins from 28 m in the south of the lake to less than 12 m in the north and unit 3 which thins from 20 m in the north to about 12 m in the south unit 1 is interpreted as resulting from deposition in a relatively quiet lacustrine or marine environment following retreat of vashon glaciers about 13 ka ago unit 2 is ascribed to deposits of sediment in runoff to stave lake from the sumas ice sheet in the fraser valley and connecting valleys to the stave basin following the retreat of the sumas ice about 11 ka ago deposition of unit 3 resulted almost entirely from sediment input from stave river entering at the north end of the lake raising the lake

post collisional deposits in the zagros foreland basin implications for diachronous underthrusting detailed sedimentology of the neogene foreland basin deposits is investigated and classified into 11 lithofacies associations with respect to their paleo sedimentary environments the foreland deposits reveal a single coarsening upward mega sequence with continuous passage from back bulge to forebulge foredeep and wedge top sedimentary environments the gachsaran deposits form the base of the foreland strata and consist mainly of three different lithofacies associations including fluvial marine and sabkha deposits in the eastern zagros in fars and are typically dominated with evaporites toward the west in the dezful and kirkuk embayments the mishan formation has three different shallow marine lithofacies associations in a vertical succession representing foredeep deposits in the eastern zagros which tapers toward the dezful embayment and disappears in iraq the agha jari distal wedge top deposits also contain three different lithofacies associations including delta deposits mostly in the fars tidal flat deposits in dezful and mesopotamia basin and continental fluvial deposits across the entire zagros the uppermost synorogenic bakhtiari formation represents proximal wedge top deposits and consists mainly of two main lithofacies associations including shallow marine and fluvial deposits within which the fluvial succession is divided into three sub lithofacies associations with respect to distance from the mountain front and hydraulic power of the river networks synthetizing sedimentary facies association with age constraints of the old foreland deposits near the zagros suture in the high zagros area suggests that a considerable part of the arabian plate has been removed at the northern edge by underthrusting and erosion moreover preservation of the young distal foreland deposits near the suture in the western zagros implies that the magnitude and rate of removal of the proximal foreland deposits have been inconstant along strike the belt and decreases toward the east

charophyte palaeoecology in the upper eocene of the eastern ebro basin catalonia spain biostratigraphic implications abstract a micropalaeontological study of the non marine upper eocene of the north eastern ebro basin catalonia spain was carried out to clarify the palaeoecology of well known charophyte species that are widely recognised as significant in charophyte biostratigraphy autochthonous specimens of the biozone index species harrisichara vasiformis tuberculata were found in marlstones from the sant boi formation middle part of the priabonian which are associated with brackish water ponds laterally related to paralic marshes in contrast laterally equivalent assemblages found in white laminated marls from stable freshwater lakes were devoid of the index species and were dominated by harrisichara lineata three more charophyte assemblages are reported from the continental artes formation stephanochara vectensis biozone upper priabonian assemblages dominated by the species nodosochara jorbae reported only from iberia at that age occur in marlstones related to freshwater temporary and turbid lakes within flood plains in medial fluvial fan environments however lychnothamnus grambastii dominates locally in similar environments with higher organic matter content laterally equivalent assemblages from freshwater perennial lakes in distal alluvial fan facies were dominated by the biozone index species harrisichara tuberculata these results provide evidence that important charophyte index species of the european charophyte biozonation were controlled by palaeoenvironmental factors such as water salinity lake level changes or terrigenous input to the lakes in consequence these species should be used with caution in biostratigraphic studies taking into account that their presence or absence may be palaeoecologically driven

time place and mode of propagation of foreland basin systems as recorded by the sedimentary fill examples of the late cretaceous and eocene retro foreland basins of the north eastern pyrenees the relationship between tectonics and sedimentary fill has been studied in two syncontractional basins of the western corbieres eastern north pyrenean retro foreland basin the late cretaceous basin formed during c 10 12 ma as a result of left lateral transpressional deformation and is composed of forward younging sub basins characterized by reworking of the forelimbs of growing fold propagation folds thrust wedge advance and cratonward migration of the platform are recorded by a deepening upward stacking pattern indicating increased regional subsidence with a limited contribution of the submarine orogen tectonic quiescence and erosional unloading lasting 29 30 ma are recorded by a shallowingupward stacking pattern and fluvial sedimentation issued from widespread sources in the emerging inner orogen the early to middle eocene basin formed as a result of pure shortening normal to the range the marine early eocene basin developed during c 2 ma by widening of a single basin provoked by the two step propagation of a basement duplex this is recorded by growth stratal patterns and coarsening upward depositional sequences indicating the increasing contribution of the emerged orogen the middle eocene continental deposits infilled two sub basins working synchronously and were transported by alluvial fans with a provenance in the inner orogen during decreasing thrust wedge advance and increasing erosional unloading

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

basin architecture and growth folding of the nw zagros early foreland basin during the late cretaceous and early tertiary abstract we present and use the chronostratigraphy of 13 field logs and detailed mapping to constrain the evolution of the early zagros foreland basin in nw iran large foraminifera calcareous nannofossil palynological and 87 sr 86 sr analysis supplied ages indicating a campanian early eocene age of the basin infill which is characterizd by a diachronous southwestward migrating shallowing upwards mixed clastic carbonate succession growth synclines and local palaeoslope variations indicate syndepositional folding from maastrichtian to eocene time and suggest forelandward migration of the deformation front we also illustrate the basin architecture with a synthetic stratigraphic transect from internal to external areas time lines cross the formation boundaries from continental kashkan red beds to taleh zang mixed clastic carbonate platforms amiran slope deposits and basinal gurpi pabdeh shales and marls the foreland basin depocentres show a progressive migration from the campanian to eocene c 83 52 7 ma with rates of c 2 4 mm a 1 during the early middle palaeocene c 65 5 58 7 ma increasing to c 6 mm a 1 during the late palaeocene earliest eocene c 58 7 52 8 ma coeval subsidence remained at c 0 27 mm a 1 during the first 12 7 ma and decreased to c 0 16 mm a 1 during the last 4 2 ma of basin filling finally we integrate our results with published large scale maps and discuss their implications in the context of the zagros orogeny supplementary material tables with dating results are available at http www geolsoc org uk sup18439

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

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

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

glacioeustatic cyclicity of a pennsylvanian carbonate platform in a foreland basin setting an example from the bachende formation of the cantabrian zone nw spain abstract by analysis of outcrop data sequence stratigraphy was used to interpret the stratal architecture and evolution of a moscovian pennsylvanian carbonate platform bachende formation located in the variscan foreland basin of the cantabrian zone nw spain the bachende formation represents a delta top carbonate platform developed in highly subsiding average subsidence rate of 254 m my distal shelf areas of the basin it reached a thickness of 650 m and covered an area of 170 km 2 after conservative palinspastic restorations the platform interior succession is mostly composed of low relief mound shaped micritic boundstones alternating with bioclastic mudstones wackestones peloidal foraminiferal packstones grainstones calcareous algal bafflestones and skeletal and ooidal grainstones landwards to the w carbonate platform beds alternate and interfinger with deltaic sandstones and shallow marine shales the platform interior consists of three sequences s1 s2 and s3 ranging from 180 to 230 m in thickness and from 1 3 to 0 5 my in age these sequences are in turn subdivided into several meter scale 10 6 m average thickness high frequency 110 to 15 ky subtidal transgressive regressive cycles these cycles are bounded by subaerial exposure or marine flooding surfaces and are inferred to be laterally continuous across the platform top they vary from mixed carbonate siliciclastic to carbonate dominated cycles cyclicity on the bachende platform was strongly influenced by glacioeustatic sea level variations and changes in subsidence and sedimentation rates subaerial exposure surfaces capping high frequency cycles are better developed in the sequence 1 late kashirian early podolskian when subsidence was relatively low and glacioeustatic sea level fluctuations could have exposed subtidal deposits during base level falls on the basis of the conservative estimated duration of each cycle and spectral analysis of cycle thickness the precessional 20 ky and obliquity 40 ky cycles were detected in all the sequences the short eccentricity cycle 100 ky in the sequence 1 and the long eccentricity cycle 400 ky in the sequences 2 and 3 podolskian nevertheless precessional and obliquity frequencies seem to dominate during sequences 2 and 3 which were deposited under significant higher subsidence and sedimentation rates additionally spectral peaks at 60 80 ky are randomly present across the whole succession and they cannot be explained as a linear response of the climate system to the milankovitch forcing

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

petroleum tectonic comparison of fold and thrust belts the zagros of iraq and iran the pyrenees of spain the sevier of western usa and the beni sub andean of bolivia this work was partially supported by subtetis pie csic 201830e039 and alpimed pie csic 201530e082 projects

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

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