fault activity in the epicentral area of the 1580 dover strait pas de calais earthquake northwestern europe on 1580 april 6 one of the most destructive earthquakes of northwestern europe took place in the dover strait pas de calais the epicentre of this seismic event the magnitude of which is estimated to have been about 6 0 has been located in the offshore continuation of the north artois shear zone a major variscan tectonic structure that traverses the dover strait the location of this and two other moderate magnitude historical earthquakes in the dover strait suggests that the north artois shear zone or some of its fault segments may be presently active in order to investigate the possible fault activity in the epicentral area of the ad 1580 earthquake we have gathered a large set of bathymetric and seismic reflection data covering the almost entire width of the dover strait these data have revealed a broad structural zone comprising several subparallel wnw ese trending faults and folds some of them significantly offsetting the cretaceous bedrock the geophysical investigation has also shown some indication of possible quaternary fault activity however this activity only appears to have affected the lowermost layers of the sediment infilling middle pleistocene palaeobasins this indicates that if these faults have been active since middle pleistocene their slip rates must have been very low hence the ad 1580 earthquake appears to be a very infrequent event in the dover strait representing a good example of the moderate magnitude earthquakes that sometimes occur in plate interiors on faults with unknown historical seismicity

static bay beach concept for scientists and engineers a review abstract headland bay beach hbb is one of the most prominent physiographic features on the oceanic margin of many countries in the world under the influence of a predominant swell its curved periphery in natural environment may reach static equilibrium and remains stable without sediment supply from updrift and or a riverain source within its own embayment coastal scientists and engineers have attempted to develop mathematical expressions to quantify this ideal bay shape since the 1940s as the scenario with depleting sediment supply has become a common reality on many parts of the world coastline in more recent time some coastal engineers have advocated a rational approach to mimicking the static bay shape found in nature in order to mitigate beach erosion as well as for coastal management nowadays many useful applications have emerged since the publication of the parabolic bay shape equation pbse developed for static equilibrium planform sep in late 1980s the advance in modern computer technologies and international collaboration has further facilitated the exchange of knowledge and applications of this static bay beach concept sbbc this paper reviews the progress on the research in hbb made by geographers and geologists since the 1940s together with the involvement of coastal engineers working on shore protection and management from the 1960s aided by software mepbay developed in 2003 for the pbse several practical examples are demonstrated in this paper for the stability verification of natural and man made bay beaches shore protection mitigating downdrift erosion of a harbour design of recreational bay beach as well as for environmental impact assessment limitations on and clarifications for engineering applications based on the sbbc are also discussed in this paper

discussion of wave energy distribution and morphological development in and around the shadow zone of an embayed beach by c j daly k r bryan c winter coastal engineering vol 93 p 40 54 abstract the computational results presented by daly et al 2014 regarding the rotation of a pocket beach in response to varying wave directionality are discussed in the context of analytical results of a stochastic parabolic bay formula

wave energy distribution and morphological development in and around the shadow zone of an embayed beach abstract background the curved shoreline shape of embayed beaches is one of its most notable characteristics and can be described using the parabolic bay shape equation pbse wave diffraction in and around the shadow zone is often regarded as the primary forcing mechanism leading to the prominent curvature of the shoreline however wave climate variables wave direction directional spreading and wave height are shown to be influential in redistributing wave energy throughout the bay and in the shadow zone methods in this study a process based morphological model delft3d is used for hydrodynamic and morphodynamic simulations of a schematic embayed beach wave forcing conditions are systematically varied between a mixture of time invariant and time varying cases results the role of diffraction is shown to be dominant only when the wave conditions are both narrow banded 30 otherwise as little as 6 variation in wave direction within a 90 range can account for the shoreline curvature in and around the shadow zone conclusion the degree to which wave direction and directional spreading vary through time therefore has a large effect on the equilibrium orientation and shoreline planform of the bay

genesis of tectonic inversion structures seismic evidence for the development of key structures along the purbeck isle of wight disturbance the interpretation of a densely spaced and well calibrated seismic grid sheds new light on the development and evolution of key regional and local structures in the wessex basin the results help to resolve long standing controversies concerning the tectonic significance of apparently anomalous outcrop patterns and the role of important local ancillary structures with respect to the major monoclinal folds with which they are associated although the structures are entirely consistent with the effects of contractional reactivation tectonic inversion of normal faults the subsurface data demonstrate the role that original extensional fault segmentation and associated relay ramps had on original depositional patterns subsequent inversion geometries and resultant outcrop patterns as well as illustrating regional controls on the formation of structures the new seismic based interpretations enable a reassessment of the lulworth crumple and the ballard down fault the lulworth crumple is interpreted as a parasitic fold complex generated by internal folding of the inverted incompetent syn rift fill in the immediate hanging wall to the purbeck fault a reactivated major normal fault the ballard down fault s origin is interpreted to result from the formation of a local late stage out of the syncline reverse fault which propagated southwards and upwards through a chalk succession as the chalk had already been rotated to form the northward dipping steep limb of the purbeck monocline at ballard down the structure cuts down stratigraphically the results stress the importance of understanding the nature of original extensional fault geometries and the competence of the sedimentary units incorporated in folds in gaining a full understanding of the genesis and evolution of structural styles in inverted basins

morphometric classification of swell dominated embayed beaches abstract globally embayed beaches are common to hilly and mountainous coastlines they are typically characterised by two headlands that are a primary control on incident wave exposure and beach morphodynamics embayed beaches exist under a range of headland morphologies and degree of embaymentisation here we present a generalised embayment morphometric parameter e which classifies the geomorphological setting of embayed beaches based on the embayment indentation and area we apply this to 168 swell dominated embayed beaches from 6 regions using open access imagery the embayment morphometric parameter e was subjected to k means cluster analysis to identify 4 classes of embayed beaches with increasing e indicating greater headland influence and impact on incident wave exposure the classes range from 1 to 4 with increasing degree of embayment the most common is class 2 43 n 73 which represents embayed beaches that have moderate embayment indentation and headland influence there are clear trends in embayment geometry regardless of location wave climate or tidal regimes within the embayments there were 6 possible headland orientations types h1 h6 the most common 58 n 97 is when both headlands are orientated outwards from the beach h6 and may result in greater morphological beach response from less headland shadowing compared with headlands orientated inwards onto the beach h1 in summary we have developed a simple classification scheme for embayed beaches based on degree of indentation and headland orientation that can be applied to any embayed beach globally

a new look at belgian aeromagnetic and gravity data through image based display and integrated modelling techniques digital processing and image based display techniques have been used to generate contour and shaded relief maps of belgian aeromagnetic data at a scale of 1 300000 for the whole of belgium these highlight the important anomalies and structural trends particularly over the brabant massif north and vertically illuminated shaded relief plots enhanced structural belts trending west east to northwest southeast in the brabant massif and west east to southwest northeast in the core of the ardennes the principal magnetic lineaments have been identified from the shaded relief plots and tentatively correlated to basement structures most short lineaments are correlated with individual folds while the more extensive lineaments are correlated with large scale fault structures magnetic highs within the brabant massif are attributed to folded sediments of the tubize group the magnetic basement in the east of belgium is sinistrally displaced to the north by an inferred deep nnw sse crustal fracture the bouguer anomaly map of belgium identifies the ardennes as a negative area and the brabant massif as a positive area with the exception of a wnw trending gravity low in its western part the southern margin of the brabant massif is defined by a steep gravity gradient coincident with the faille bordiere border fault trial modelling of the gravity and magnetic data carried out along profiles across the brabant and stavelot massifs has identified probable acid igneous intrusions in the western part of the brabant massif and a deep magnetic lower density body underlying the whole ardennes region which is thought to be a distinctive precambrian crustal block

eocene inversion history of the sandown pericline isle of wight southern england study of the composition and distribution of derived lithoclast and fossil suites collected from the selsey barton and becton formations in whitecliff bay isle of wight has enabled a detailed reconstruction of mid late eocene uplift of 500 m on the northern limb of the sandown pericline the stratigraphical distribution of clasts and fossils derived from older formations demonstrates the erosion of progressively older eocene palaeocene and cretaceous sediments during growth of the structure the presence of delicate reworked fossils and clasts together with limited palaeocurrent data support very local derivation from the south the preservational state of the derived materials is used to identify the diverse processes of erosion and transport two phases of uplift lutetian bartonian separated by a period of quiescence and peneplanation have been identified rates of eocene uplift of about 100 m ma 1 are postulated to have taken place

inversion of field data in fault tectonics to obtain the regional stress iii a new rapid direct inversion method by analytical means summary a new method for determining the reduced stress tensor with four degrees of freedom the orientations of the three principal stress axes as well as the ratio of principal stress differences using fault slip data or focal mechanisms of earthquakes is presented from a computational point of view the inversion of fault slip data is made in a direct way by purely analytical means as a result the determination process is extremely fast and adaptable on small microcomputers from a physical point of view the method aims at simultaneously i minimizing the angles between theoretical shear stress and actual slip vector and ii having relative magnitudes of shear stress large enough to induce slip despite rock cohesion and friction examples of application to actual fault slip data sets with good or poor variety of fault slip orientations are shown the double significance of the basic criterion adopted results in a more realistic solution of the inverse problem than the single minimization of the shear stria angle

geological and mechanical study of argillaceous north sea chalk implications for the characterisation of fractured reservoirs abstract argillaceous chalk intervals from the north sea are characterised by matrix permeabilities lower than 0 2 md and therefore they are defined as tight chalks hence fracture networks within these chalks are of major importance to predict fluid flow and reservoir or seal behaviour this study aims to understand the geological parameters controlling the chalk petrophysical and mechanical properties using the outcrop analogue of the cenomanian chalk at cap blanc nez northern france sedimentological petrographic and petrophysical analyses were performed and show that the combination of the depositional environment and diagenetic imprint control the microtexture non carbonate content is ranging from 5 to 40 within the studied samples and is critical for the diagenetic imprint the fracture behaviour of the chalk was studied using a mechanical stratigraphy approach throughout the 70 m thick succession where a transition between lower cenomanian argillaceous chalk and middle upper cenomanian pure chalk is exposed twenty two mechanical units are distinguished and the amount of fractures crosscutting initiating and terminating on mechanical interfaces quantified manual scanlines show that fracture spacing ranges from 17 to 232 cm mechanical interfaces are associated with lithological heterogeneities with strong microtextural contrasts related to the non carbonate content and or degree of cementation the mechanical units are thus defined either by deposition or diagenesis the fracturing behaviour of about 10 m homogeneous pure chalk interval units defined as dfz densely fractured zones differs significantly from the rest of the succession large sigmoidal shaped fractures are confined to those intervals and a dense fracture network developed because of their plastic behaviour clay layers are able to accommodate part of the stress whereas homogeneous pure chalk show a more brittle behaviour

is there a remnant variscan subducted slab in the mantle beneath the paris basin implications for the late variscan lithospheric delamination process and the paris basin formation abstract the paris basin northern france is a late paleozoic mesozoic intracratonic basin that settled upon the collapsed variscan collisional belt the lithospheric roots of the variscan orogenic system below the paris basin have been investigated using a european scale p wave velocity tomographic model tomography points out the existence of a significant high velocity anomaly in the upper mantle below the western part of the basin at 150 200 km depth the anomaly extends with a nw se trend along the buried northern france trace of the northern variscan suture zone i e the bray segment of the upper carboniferous lizard rhenohercynian lrh suture moreover the high velocity anomaly is spatially correlated with the prominent paris basin magnetic anomaly its downdip extent reaches depths greater than 200 km below the southern margin of the paris basin as suggested in previous tomographic studies below ancient suture zones these data argue for such anomaly being the remnant of a variscan subducted slab that escaped the extensive late orogenic delamination process affecting the lithospheric roots by late carboniferous early permian times and that was preserved stable over 300 ma at the base of the lithosphere on a general geodynamical perspective these results provide a new insight into the long term evolution of subducted lithosphere into the mantle in the case of the western european variscan orogenic belt they suggest that the subduction of the lrh slab below the previously thickened variscan crust and its final detachment from the orogenic root have played an important role in the collapse of the belt inducing thermal erosion and extension of the overriding lithosphere the spatial evolution of late orogenic extension across the belt and of subsequent thermal subsidence in the paris basin is suggested to result from the heterogeneous delamination of the lithospheric roots along strike and from the resultant pattern of asthenospheric rise

slope failure of chalk channel margins implications of an upper cretaceous mass transport complex southern england the importance of mass transport and bottom currents is now widely recognized in the upper cretaceous chalk group of northern europe the detailed dynamics and interaction of the two phenomena are difficult to study as most evidence is based on seismic data and drill core here field observations provide evidence for recurring margin collapse of a long lived campanian channel compressionally deformed and thrust chalk hardgrounds are correlated to thicker non cemented chalk beds that form a broad gentle anticline these chalks represent a slump complex with a roll over anticline of expanded non cemented chalk in the head region and a culmination of condensed hardgrounds in the toe region observations strongly suggest that the slumping represents collapse of a channel margin farther northwards the contemporaneous succession shows evidence of small scale penecontemporaneous normal faulting towards the south here interpreted as gravitational settling of the chalk immediately adjacent to the channel margin detailed biostratigraphic studies and sedimentological observations provide evidence for at least two discrete collapse events and suggest the slumping to be the result of channel margin oversteepening rather than evidence for a regional tectonic phase the described example thus serves as an analogue for processes commonly only inferred from subsurface data

uncertainty in the application of the parabolic bay shape equation part 1 abstract this paper aims to quantify the uncertainty in the application of the parabolic bay shape equation pbse for a bay in static equilibrium by means of expert elicitation a database was generated consisting of the position of the control points that determine the static equilibrium planform sep the elicitation consisted of two parts in part 1 22 expert volunteers were asked to place the three control points that determine the sep on a vertical aerial photograph of taquaras taquarinhas bay a morphologically stable bay in the south of brazil approximately 1800 m in width and with an indentation of 750 m the distribution of the location of the sep along four evenly spaced 200 m profiles in the southern part of the bay was determined the overall bias of the location of the sep calculated over the four profiles was in the order of 41 m landward and the average standard deviation was 116 m these parameters increased when moving alongshore toward the curved section of the bay this means that the uncertainty in the application of the pbse is dependent on the particular point of interest along the bay in part 2 of the elicitation 30 volunteers participated this time the consequence of the placement of the control points the corresponding sep was visible comparing the results from parts 1 and 2 it was observed that when volunteers were directly confronted with the result of the placement of the control points a plotted sep a much smaller variation in the position of the sep occurred this implies that when feedback on the result is provided the pbse is a more robust method

recess drawn by the internal zone outer boundary and oblique structures in the paleomargin derived units subbetic domain central betics an analogue modelling approach abstract the subbetic domain comprising the south iberian paleomargin derived units is a fold and thrust belt developed over a ductile substrate showing a complex structural pattern in the central betics a main trend can be defined with respect to which frequent oblique structures are observed these oblique structures often subperpendicular to the main trend are not located along transfer zones but rather are present everywhere in the fold and thrust belt moreover they are coetaneous with those drawing the main trend this complex pattern is situated in front of a recess marked by the outer boundary of the internal zones the alboran domain which acted as backstop analogue models were designed to study the influence of such a recess on a ductile brittle multilayer one of the models in which the backstop recess is symmetric with respect to its direction of movement shows a high variation in the orientation of the resulting structures being not only qualitatively but also quantitatively similar to the studied natural case

brittle tectonic structures and palaeostress analysis in the isle of wight wessex basin southern u k abstract brittle tectonic analysis of cretaceous paleogene sediments at a total of 17 sites located in the isle of wight u k enables four main tectonic events that occurred prior to and after the folding to be identified and successive palaeostress tensors to be determined using the inversion method three of the events can be shown to have occurred prior to the folding 1 a syn sedimentary extension of upper cretaceous age 2 a strike slip faulting regime with an ese wnw direction of compression 3 a compressional regime marked by strike slip faulting with an nne ssw to n s direction of compression the fourth and last compressional event took place after the folding and is characterised both by reverse and strike slip faulting with a dominant n s direction of compression syn folding faults also developed between the third and fourth events all four events can be connected to the extensional tectonics and different steps of structural inversion both of which were integral to the development and evolution of the wessex basin

a late cenozoic regional mesofracture system in southern england and northern france the upper cretaceous and palaeogene rocks of s england and n france are cut by a nw trending system of fractures characterized by swarms of vertical extension joints accompanied by conjugate sets of hybrid and shear joints and normal mesofaults many major photolineaments exhibit the same nw trend as the fractures and are particularly conspicuous in n france where they are coincident with rectilinear drainage channels suggesting a relationship between fracture orientation and physiography in s england this relationship is absent possibly because of the influence of additional fracture systems related to major flexures trending obliquely to the nw se direction these major e w trending flexures and associated fracture systems were formed during the oligocene to early miocene 9helvetic9 phase of deformation and are cross cut obliquely by fractures in the nw trending system the nw trending fractures and lineaments are parallel to neotectonic normal faults in the lower rhine embayment and become less well developed to the west with increasing distance from these major structures the lower rhine faults were reactivated and propagated into the quaternary cover as a consequence of ne sw regional tension generated during the late neogene to recent 9jura9 phase of nw se alpine convergence the nw trending extensional structures in s england and n france are considered to be of about the same age and related to the same stress regime as the neotectonic normal faults of the lower rhine embayment however because fractures of the nw system cutting palaeogene sediments in se england are truncated by the erosion surface beneath the plio pleistocene red crag deposits it is possible that in england fracture initiation did not continue into quaternary times

uncertainty in the application of the parabolic bay shape equation part 2 abstract this paper attempts to highlight issues that are relevant in the application of the parabolic bay shape equation pbse to a non equilibrium bay for this case the bay of imbituba in southern brazil was chosen the construction of a breakwater to shelter the port of imbituba in the south of the bay was accompanied by an increase in sedimentation to the port area from an eroding downdrift beach superimposed plots of the coastline of the bay of imbituba from different years confirm a general trend of accretion of the southern part of the bay accompanied with a retreat of the coastline in the northern part after the application of the pbse it became clear that the breakwater caused a change in the equilibrium state of the bay between 1947 and 2001 the bay of imbituba has changed from a dynamic equilibrium to a natural beach reshaping or self reshaping the tendency of the sedimentation of the southern part of the bay can be explained by the sep associated with the new updrift diffraction point tip of the breakwater the seaward position of the sep predicts a need for additional sediment in order to achieve a stable plan form

crustal structure beneath southern england from deep seismic reflection profiles seismic reflection events from recently acquired profiles in southern england are interpreted in terms of stratigraphic and structural interfaces between rock units in particular evidence is brought forward that a series of reflection events dipping between 22 and 27 with azimuth averaging 160 represents 2 major thrust zones occurring in the variscan floor beneath mesozoic cover a geological model based upon borehole information and regional geological considerations is presented the tentative recognition of crystalline basement overlain and overstepped by late proterozoic rocks of variable thickness suggests that basement in this area was unstable from late precambrian times the mesozoic structural evolution can be related to tectonic re activation of major concealed thrust zones in the palaeozoic 9basement9

insect evidence for environmental and climate changes from younger dryas to sub boreal in a river floodplain at st momelin st omer basin northern france coleoptera and trichoptera the st omer area is a rapidly subsiding basin in which long sequences of weichselian and holocene sediments are preserved a core 21 m long extracted from near st momelin about ten km north of st omer has been analysed for insect fossils four faunal units smi 1 to smi 4 are described based on changes in both coleopteran and trichopteran assemblages the basal faunal unit smi 1 includes many cold adapted species and is attributed to the younger dryas chronozone the transition to holocene sedimentation was abrupt faunal units smi 2 to smi 4 are attributable to the holocene they lack all the cold adapted species found in the basal sediments and in their place are insect assemblages very similar to the present day fauna in this region this sequence spans the period from the pre boreal to the sub boreal faunal unit smi 2 includes insects from the pre boreal the boreal and most of the atlantic periods this fauna was fairly sparse and made up largely of species living in freshwater habitats the faunal unit smi 3 includes the insect assemblages from the late atlantic to sub boreal periods this fauna was much more diverse and indicated a river meandering across its floodplain and bordered by a mature forest at a time when the climate was warmer than that of the present day this chronostratigraphical sequence of events is supported by 14c dates and by lithological data thermal climatic conditions have been quantified using the mutual climatic range method during the younger dryas period smi 1 tmax the mean july temperature was in the region of 10 c and tmin the mean temperature of january february was close to 11 12 c after the sudden climatic amelioration at the start of the holocene smi 2 to smi 4 tmax probably fluctuated throughout the early holocene between 16 c to 19 c and tmin between 0 c to 5 c figures that are close to those of the present day this climatic history is compared with others in northern europe

the variscan belt of northern france southern belgium geodynamic implications of new palaeomagnetic data abstract palaeomagnetic investigations were carried out in devonian early carboniferous rocks of the variscan foreland chain of northern france southern belgium in order to reveal the origin of its arcuate shape the brabant parautochthon was sampled in the boulonnais near calais and near tournai while the ardenne allochthon was sampled near maubeuge and in the givet area all the sampled localities yielded characteristic remanent magnetization as a result of stepwise demagnetization and component analysis fold or tilt tests were possible for three localities with negative results indicating pervasive remagnetization the tectonic position was sub horizontal at two localities while the tilt was monoclinal for the rest therefore the acquisition time of the magnetic signals was estimated by comparing the palaeolatitude computed from each magnetic component to the palaeolatitudes of variscan europe calculated after van der voo 1993 three components showing a a southern b a near equatorial and c a northern palaeolatitude are recognized from our data since a pre variscan age of component a observed only in boulonnais at 10 sites is not supported by data it is assigned to an early phase of deformation component b 16 sites was acquired during the peak of the variscan tectonics late westphalian while component c five sites originated during permian times regardless of the palaeolatitudes declinations fall between 190 and 210 thus being conformable with the declinations expected for variscan europe the declinations show no correlation with the arcuate shape of the belt neither are they different in the paraauthochthon and in the allochthon nor in the different components arc formation by moulding of the allochthon on the brabant parautochthon is therefore not supported by these data since this mechanism requires substantial opposed rotations on both wings of the arc the available palaeomagnetic data are conformable with a pre formed arc simply docking to the brabant obstacle of similar shape variable offsets along a main thrust make possible a third model which slightly unfolds the former passive arc

superimposed folding and oblique structures in the palaeomargin derived units of the central betics sw spain the subbetic units consist of a deformed wedge of sedimentary rocks deriving from the south iberian palaeomargin in the westernmost segment of the alpine mediterranean orogenic belt in the central betics shortening produced folding thrusting and nappe stacking the structural trend is ne sw to ene wsw and the internal structure of the thrust sheets which shows no preferred vergence is strongly controlled by the rheology of the decollement level a viscous layer of triassic evaporites and of the overlying carbonate rock sequence the relationships of piggyback basin miocene sediments with the main structures show that the latter developed during the aquitanian burdigalian transition superimposed folding is described for the first time in the study area the origin of the interference cannot be determined at present but may be related to initially oblique structures refolded during progressive deformation a revision of previously published palaeomagnetic data in the light of the data presented in this paper in conjunction with a model of the structural evolution of the subbetic units of the western betics permits us to establish milestones of the tectonic evolution of the external zones in the northern branch of the gibraltar arc

early diagenetic formation of carbonates in a clastic dominated ramp environment impacted by synsedimentary faulting induced fluid seepage evidence from the late jurassic boulonnais basin n france the late jurassic deposits of the boulonnais area n france represents the proximal lateral equivalent of the kimmeridge clay formation they accumulated on a clastic dominated ramp subject to synsedimentary faulting in relation with the northward propagation of the atlantic rifting within the terrigenous accumulations some carbonate objects are visible at various conspicuous levels oyster patch reefs and fine grained carbonate beds either continuous or more or less nodular preliminary studies demonstrated that the carbonate beds of the bancs jumeaux formation as well as the carbonate matrix of the oyster patch reefs are of diagenetic origin in this paper we extend the study to many other limestone beds of the boulonnais with mud or wackestone texture examining facies and microfacies through various techniques as well as geochemical data o c and s stable isotopes major and trace elements we conclude that all examined carbonate bodies are of early diagenetic origin and that they precipitated at or close to the sea bed from seawater mixing with ascending fluids containing isotopically light carbon of organic origin fluid circulation was probably induced by the extensional block faulting segmentation of the northern margin of the boulonnais basin in late jurassic times fluid seepages were either channelized along fault planes or more diffuse as illustrated by the model we propose

fracture corridors and fault reactivation example from the chalk isle of thanet kent england abstract fracture corridors elongated zones of narrowly spaced highly connected fractures can generate the main fluid flow pathways in natural reservoirs and can be responsible for an early water break through in hydrocarbon reservoirs understanding this fracturing is necessary for reservoir behaviour prediction an outcrop analogue of a chalk fractured reservoir from the isle of thanet in se england is used to understand the development of fracture corridors and to characterize their relationship with faulting and folding we show that fracture corridors are associated with strike slip reactivation on sub seismic faults in a context of polyphase deformation they nucleate on slip patch tips or on areas of stress concentration due to fault plane dip strike irregularities steps or fault intersections fracture corridors generated are oblique to the fault which they initiate on with increasing deformation fractures composing the corridor are sheared and a fault can develop within the fracture corridor the relationship between folding and fracture corridor development in this area is indirect both are localized by a pre existing basement fault that allows stress concentration and reorientation and promotes fault reactivation in the chalk cover this work emphases the importance of the distribution of sub seismic faults in fractured reservoirs as they can control the development of fracture corridors

on the influence of wave directional spreading on the equilibrium planform of embayed beaches abstract equilibrium beach formulations are engineering tools for estimating a response of beaches in the long term they aim at defining the final orientation of a beach on a scale of years and thus they are used for evaluating the shoreline response due to human interference ports breakwaters protection works etc several equations can be found in the literature for obtaining the static equilibrium planform sep of headland bay beaches hbbs one such being the parabolic bay shape equation pbse the sep is strongly dependent on the location of the down coast control point po which is the downdrift limit from which the pbse is applicable the literature recommends the determination of the po point by means of the direction of the mean wave energy flux at the diffraction point however when this is applied to equilibrium embayed beaches in zones with a wide variability of wave climate directionality and or in cases where the diffraction point is located far from the equilibrium shoreline this approach is no longer valid and thus the resulting planform shape does not properly fit the sep for such conditions this paper investigates the methodology for locating the po point of the sep for such cases exploring the role of wave climate directional spreading employing 44 hbbs in spain and latin america it correlates the planform shape in the long term with the directional variability of the wave climate at the diffraction point additionally an extensive series of numerical simulations using a spectral wave model was carried out to model the combined effects of refraction diffraction in the lee of a breakwater defining the part affected by the coastal structure under different wave conditions the results clarify the importance of wave directional spreading in locating the po indicating that the wider the directional spreading the farther the po point on the shoreline moreover the farther the diffraction point from the coast the smaller the part of the beach affected by the coastal barrier a new formula has been derived to locate the down coast control point po of the parabolic part of the shoreline corresponding to the pbse as a function of the directional variance of the wave climate and the location of the diffraction point the model produced good results with r2 0 9117 and a rmse 1 8297 in estimating the location of the po point in various natural and man made beaches with different degrees of wave directionality

vulnerability of the dover strait to coseismic tsunami hazards insights from numerical modelling summary on 1580 april 6 a large earthquake shook the eastern english channel and its shores with numerous casualties and significant destruction documented some reports suggest that it was followed by a tsunami meanwhile earthquake magnitudes of mw 7 have been deemed possible on intraplate fault systems in neighbouring benelux this study aims to determine the possibilityofamw 5 5magnitudeearthquakegeneratingatsunamiinthedoverstrait oneof the world s busiest seaways in a series of numerical models focusing on sensitivity analysis earthquake source parameters for the dover strait are constrained by palaeoseismological evidence and historical accounts producing maps of wave heights and analysis of frequencies based on six strategically located virtual tide gauges of potential concern to engineering geologists a maximum credible scenario is also tested for mw 6 9 for earthquakes with mw of 5 5 none of the fault models we tested produced a tsunami on neighbouring shores however forearthquakeswithmw 6 9 bothextensionalandthrustingeventsproducedtsunami waves with open water amplitudes of up to 1 5 m and higher amplitudes might be expected in regions where waves are amplified by regional nearshore bathymetry sensitivity to parameter choice is emphasized but a pattern of densely inhabited coastal hotspots liable to tsunamirelated damage because of bathymetric forcing factors is consistently obtained

early diagenetic carbonate bed formation at the sediment water interface triggered by synsedimentary faults abstract the latest jurassic of the boulonnais cliffs n france strait of dover corresponds to a homoclinal ramp type depositional environment where sedimentation was clastic dominated marlstones sandstones the tithonian marlstone formations exhibit two or three carbonate beds in the vicinity of wimereux city 3 beds at wimereux north and 2 beds at wimereux south the beds are made up with quite pure fine grained microspar carbonate in sharp contrast with the background sedimentation this paper presents a sedimentological and geochemical study of these limestone beds aiming to determine whether they are of diagenetic origin and hence whether they could have acted as permeability migration barriers during hydrocarbon maturation migration mineralogical chemical and c and o stable isotope data allow us to infer that the beds formed during synsedimentary early diagenesis at the sediment water interface or close to it as the result of a rise of alkalinity induced by bacterial sulfate reduction the rise of alkalinity was not counter balanced by the accumulation of h2s released by sulfate reduction and carbonate ion supersaturation was rapidly reached causing the formation of laterally continuous limestone beds conditions prone to bacterial sulfate reduction developed episodically at the sediment water interface as the result of spills of anoxic pore waters onto the seafloor these spills were probably released by synsedimentary fault movements such continuous limestone beds being formed under rather common conditions during the earliest stage of diagenesis of shale deposits must be more frequent in the geological record than hitherto identified

modelling of embayed beach equilibrium planform and rotation signal abstract embayed beaches are highly attractive sandy beaches bounded laterally by rigid boundaries which deeply affect equilibrium beach planform and shoreline dynamics we use lx shore a state of the art shoreline change model coupled with a spectral wave model to address embayed beach shoreline dynamics driven by longshore sediment transport processes the model is applied to different idealized embayed beach configurations including variations in headland lengths the model simulates a large range of equilibrium embayed beach planforms and associated spatial and temporal modes of shoreline variability for short headlands enabling occasional headland sand bypassing both embayed beach curvature and maximum erosion at the upwave side of the embayment increases with increasing headland length beach curvature also increases with increasing headland length for headlands long enough to prevent any headland sand bypassing in contrast at the same time embayed beach becomes increasingly curved and symmetric with maximum localised erosion within the embayment decreasing in intensity when there is no headland sand bypassing rotation signal decreases in amplitude and becomes increasingly symmetric with increasing headland length the modal time invariant directional spreading of incident waves is critical to embayed beach behaviour with the envelope and variance of cross shore shoreline change and time averaged shoreline curvature all increasing with decreasing modal directional spreading embayed beach rotation characteristic timescale increases with increasing embayed beach length while the narrower the embayment the smaller the cross shore amplitude of shoreline variability our simulations provide new insight into the influence of embayment characteristics and incident wave conditions on equilibrium planform and shoreline dynamics of embayed beaches this work also implies that the degree of potential headland sand bypassing should be taken into account for modelling of beach rotational dynamics and embayed beach dynamic planform configuration

the origin of the basse normandie duplex boulonnais france abstract two hercynian duplexes are developed in visean limestones in the basse normandie quarry the lower duplex is completely exposed in a subvertical quarry wall the partially exposed upper duplex lies immediately above the lower duplex the duplexes are both located in the footwall of the hydrequent thrust which emplaced devonian clastic sediments above the visean limestones the lower duplex exposes all the internal thrusts a reference bed of chalky limestone the roof and floor thrusts and the duplex tip the duplex has been graphically restored to its pre deformation geometry by line length and area balancing and its resultant geometry is close to the model of boyer elliott the lower duplex shortened by two different mechanisms an initial phase of layer parallel shortening which produced no cleavage followed by thrust imbrication the average contraction of the front portion of the duplex was 49 natural strain of which 27 is layer parallel shortening and 22 is thrust imbrication however locally the bulk shortening increases from zero at the duplex tip to over 120 in a down dip direction the area balancing provides the most accurate estimates of bulk shortening line length balance calculations give minimum estimates only an area balance on the whole of the lower duplex gives a bulk shortening of 84 an area balance of the upper duplex yields an average contraction of 75 and the total contraction produced by both duplexes is 92

a buried granite batholith beneath the east midland shelf of the southern north sea basin published bgs gravity data of the uk southern north sea basin show the presence of a gravity low trending to the ese across the northern half of quadrant 47 two simplified geological cross sections have been constructed across this feature with sedimentary structure based upon well information and reflection seismic data gravity modelling of these sections demonstrates that the gravity anomaly is unlikely to be produced by the presence of thick low density sediments consequently the presence of a large buried granite batholith is postulated the buoyant influence of such a granite may have exerted considerable tectonic control during the development of the southern north sea basin in particular its presence may help to explain the development of the east midland shelf the associated complex fault movements along the flamborough head and dowsing fault zones and the areal distribution and thickness of the rotliegendes sand

clay mineralogical and geochemical expressions of the late campanian event in the aquitaine and paris basins france palaeoenvironmental implications campanian sediments from two french sedimentary basins were studied using clay mineralogy and stable isotope 13c and 18o geochemistry in order to investigate the late campanian event the clay fraction of the campanian sediments from the tercis les bains section aquitaine basin and from the poigny borehole paris basin is mainly composed of smectite this background sedimentation was however interrupted during the upper campanian in the two basins by a substantial increase in detrital inputs including illite kaolinite and chlorite at tercis les bains and illite at poigny this detrital event resulting from the enhanced erosion of nearby continental areas triggered by increasing runoff has also been recognized in the tethys and south atlantic oceans it coincided with a global negative carbon isotope excursion the late campanian event lce carbon isotope stratigraphy was used to correlate the two basins with previously studied sections from distant areas spectral analysis of the bulk 13c from tercis les bains suggests a duration of ca 400 kyr for a pre lce negative excursion and ca 800 900 kyr for the lce sensu stricto the detrital event as characterized by clay mineralogy spans the interval that comprises the pre lce and the lce with a duration of 1 3 myr intensification of continental erosion during the lce may have resulted either from the late campanian polyplocum regression and or from a regional tectonic pulse that triggered the emersion of previous submerged shelf areas and the increase of silicate erosion as the lce seems to be recorded at a large geographic scale it is proposed here that enhanced chemical weathering and an associated decrease in atmospheric pco2 levels could have contributed to the long term late cretaceous cooling trend

structural analysis of the adjacent acadian and variscan fold belts in belgium and northern france from geophysical and geological evidence abstract two palaeozoic fold belts are juxtaposed in belgium and northern france the northern belt of the brabant massif traditionally considered a part of the european caledonides was folded during the acadian orogeny in the early devonian although it is largely concealed gravity and magnetic maps give a general picture of the existing structures a curved gravity trend is interpreted as an arc shaped succession of granitic batholiths structures north and south of this arc are completely different the northern subdomain containing magnetic lower cambrian metasediments shows multiple thrust faults towards the south over the granites whereas the southern subdomain without magnetic rocks is moulded around the granitic core the southern variscan belt is characterized in general by thrusting with a north nw and ne vergence during the variscan orogeny the brabant massif acted as an obstacle to the general transport of the ardennes massif to the n nw the oblique convergence with the brabant massif caused differential displacement towards the northwest the western areas having travelled farther as seen from a pattern of wnw oriented strike slip faults

tertiary structures and hydrocarbon entrapment in the weald basin of southern england abstract the weald basin of southeast england was formed by rapid subsidence associated with thermal relaxation following early mesozoic extensional block faulting the basin appears initially to have taken the form of an easterly extension of the wessex basin but became the major depocentre during the upper jurassic and lower cretaceous with associated active faulting these movements appear to have ceased prior to albian times and a full upper cretaceous cover is believed to have been deposited in a gentle downwarp which extended far beyond the confines of the weald and wessex basins major inversion of the weald basin took place in the tertiary with both gentle regional uplift which in the eastern part of the basin is estimated to have exceeded 5000 feet 1525 metres and intense local uplift along pre existing zones of weakness which led to the formation of compressional features such as tight folds and reverse faults zones of tertiary deformation appear to have been strongly influenced by underlying particularly hercynian structural trends lower jurassic source rocks reached maturity in the early cretaceous and initial migration occurred at this time often over long distances into traps closed by pre aptian faults tertiary tilting and uplift led to the breaching of many of these pre existing traps and the formation of large folded closures a second phase of hydrocarbon migration particularly of gas took place at this time with significant vertical migration along fault zones major reservoirs located to date occur in middle jurassic carbonates and upper jurassic sandstones but deep burial in the basin has caused considerable destruction of primary reservoir characteristics changes in the temperature and pressure regimes and the mobilization of fluids within the basin resulting from the tertiary uplift caused further diagenetic changes particularly in the carbonate reservoirs exploration of the weald basin remains at a very early stage with a low drilling density to date the more recent drilling has focussed on earlier structures but traps formed or modified during the tertiary movements represent important exploration objectives although general deterioration in reservoir quality towards the centre and east of the basin makes large fold closures in these areas less attractive

how plate tectonics is recorded in chalk deposits along the eastern english channel in normandy france and sussex uk abstract intra plate stresses that occurred in the anglo paris basin and english channel during upper cretaceous and cenozoic times are a consequence of the convergence between eurasia and africa and the opening of the north atlantic area this geodynamic re organisation is recorded on each side of the english channel with the emergence of regional structures such as the the weald artois anticline and the reactivation of large scale strike slip faults we analyse the anglo paris basin chalk fracture system on each side of the eastern english channel using a set of 1600 meso scale fractures data collected on coastal chalk cliffs in normandy nw france and sussex uk meso scale fracture system is precisely dated using chalk lithostratigraphy correlations within the basin moreover an inversion method is used on fault slip data to evidence a paleostress chronology in the anglo paris basin three main upper cretaceous extensive events characterized by normal faults and jointing are recorded in normandy and two cenozoic compressive and extensive events with strike slip and normal faults appear in sussex paleostress records vary on each part of the eastern english channel the meso scale fracture system is thus used to better define the type of relationship between meso scale and large scale brittle deformation in the chalk during meso cenozoic a first ne sw extension is recorded in normandy in relation with local anticlines structures and related to the lower rhine graben opening a second event is a wnw ese extension of local origin in relation with the subsidence axis of the paris basin the third event is a nne ssw extension well marked in normandy and related to the activation of e w normal faults in the western approaches of the english channel this event is also recorded in sussex and reactivates locally older fractures in strike slip the oligocene n s compression e w extension related to the pyrenean tectonics and the last e w extension relative to the north sea graben opening are well recorded in sussex but not in normandy recent far field stresses developed in the nw european platform are focused on deep crustal structures like the artois hills and the cotentin areas in france these structures act as a stress barrier by protecting the normandy chalk from recent far field stresses on the contrary recent far field stresses are easily recorded by meso scale brittle deformation on the folded chalk in sussex

high resolution downscaled ocean waves dow reanalysis in coastal areas abstract large scale wave reanalysis databases 0 1 1 spatial resolution provide valuable information for wave climate research and ocean applications which require long term time series 20 years of hourly sea state parameters however coastal studies need a more detailed spatial resolution 50 500 m including wave transformation processes in shallow waters this specific problem called downscaling is usually solved applying a dynamical approach by means of numerical wave propagation models requiring a high computational time effort besides the use of atmospheric reanalysis and wave generation and propagation numerical models introduce some uncertainties and errors that must be dealt with in this work we present a global framework to downscale wave reanalysis to coastal areas taking into account the correction of open sea significant wave height directional calibration and drastically reducing the cpu time effort about 1000 by using a hybrid methodology which combines numerical models dynamical downscaling and mathematical tools statistical downscaling the spatial wave variability along the boundaries of the propagation domain and the simultaneous wind fields are taking into account in the numerical propagations to performance similarly to the dynamical downscaling approach the principal component analysis is applied to the model forcings to reduce the data dimension simplifying the selection of a subset of numerical simulations and the definition of the wave transfer function which incorporates the dependency of the wave spatial variability and the non uniform wind forcings the methodology has been tested in a case study on the northern coast of spain and validated using shallow water buoys confirming a good reproduction of the hourly time series structure and the different statistical parameters

dynamics and inversion of the mesozoic basin of the weald boulonnais area role of basement reactivation abstract the geometry and dynamics of the mesozoic basins of the weald boulonnais area have been controlled by the distribution of preexisting variscan structures the emergent variscan frontal thrust faults are predominantly e w oriented in southern england while in northern france they have a largely nw se orientation extension related to tethyan and atlantic opening has reactivated these faults and generated new faults that together have conditioned the resultant mesozoic basin geometries jurassic to cretaceous n s extension gave the weald boulonnais basin an asymmetric geometry with the greatest subsidence located along its nw margin late cretaceous palaeogene n s oriented alpine s l compression inverted the basin and produced an e w symmetrical anticline associated with many subsidiary anticlines or monoclines and reverse faults in the boulonnais extensional and contractional faults that controlled sedimentation and inversion of the mesozoic basin are examined in the light of new field and reprocessed gravity data to establish possible controls exerted by preexisting variscan structures

three dimensional structural model of composite dolomite bodies in folded area upper jurassic of the etoile massif southeastern france the three dimensional 3 d geometry of fractures and fault related dolomite is difficult to access with classical subsurface prospection tools therefore we have investigated an outcrop to improve the subsurface prediction for complex dolomite bodies this outcrop is located in the etoile massif southeastern france within a fault bend anticline the sedimentary units are of upper triassic to lower barremian age the fold results from the pyreneo provencal shortening during the late cretaceous to the eocene the anticline hosts three types of dolomite bodies 1a massive dolomite of middle to late oxfordian age 1b syndepositional stratabound dolomite of tithonian age and 2 isolated dolomite bodies associated with fractures and faults large scale geometries of fault related dolomite bodies have been modeled in 3 d the 3 d geometries of these bodies show diapir finger and wall like structures these bodies are located close to the main thrusts in strata of middle oxfordian to early barremian age and are linked to the compressive fold bending phase during the late cretaceous fault related dolomitization occurred because of magnesium removal from the hydraulic brecciation and the pressure solution of type 1 dolomite with overpressured fluids these fluids flushed upward along the main thrust and laterally by following the reservoir property contrasts in the host rocks fault related dolomite bodies are either spread far apart from faults in grainy limestones with good initial reservoir properties or are restricted to fault vicinity in muddy limestones with poor initial reservoir properties the study of the structural and stratigraphic framework was essential in the understanding of the dolomitization process

modelling cover deformation and decoupling during inversion using the mid polish trough as a case study abstract seismic sections across the nw part of the polish basin show that thrust faults developed in the sedimentary units above the zechstein evaporite layer during basin inversion these cover thrust faults have formed above the basement footwall based on the evolution of the basin a series of scaled analogue models was carried out to study interaction between a basement fault and cover sediments during basin extension and inversion during model extension a set of normal faults originated in the sand cover above the basement fault area the distribution and geometry of these faults were dependent on the thickness of a ductile layer and pre extension sand layer synkinematic deposition the amount of model extension as well as on the presence of a ductile layer between the cover and basement footwall cover was faulted away from the basement only in cases where a large amount of model extension and hanging wall subsidence were not balanced by synkinematic deposition model inversion reactivated major cover faults located above the basement fault tip as reverse faults whereas other extensional faults were either rotated or activated only in their upper segments evolving into sub horizontal thrusts new normal or reverse faults originated in the footwall cover in models which contained a very thin pre extension sand layer above the ductile layer this was also the case in the highly extended and shortened model in which synkinematic hanging wall subsidence was not balanced by sand deposition during model extension model results show that inversion along the basement fault results in shortening of the cover units and formation of thrust faults this scenario happens only when the cover units are decoupled from the basement by a ductile layer given this we argue that the thrusts in the sedimentary infill of the polish basin which are decoupled from the basement tectonics by zechstein evaporites developed due to the inversion of the basement faults during the late cretaceous early tertiary

on the application of static equilibrium bay formulations to natural and man made beaches crenulate shaped bays are common features found all around the world the most widely used formulation for representing this kind of bay is the parabolic approach proposed by hsu and evans institution of civil engineers proc london england 87 1989 556 who suggested a methodology to test and predict the stability of static equilibrium shapes in natural and man made bays based on an analytical model of null drift current and using an empirical approach a modified methodology is proposed the new procedure is able to locate the downcoast starting point of the static equilibrium beach from which the parabolic plan form of hsu and evans is valid this methodology is applied with good results to different natural and man made beaches along the atlantic and mediterranean coasts of spain including tombolo shaped beaches

late quaternary faulting on the manas and hutubi reverse faults in the northern foreland basin of tian shan china abstract the tian shan range lies in the actively deforming part of the india asia collision zone in the northern foreland basin of tian shan the strata were intensively deformed by cenozoic folding and faulting slip rate studies along these faults are important for understanding the dynamics of crustal deformation and evaluating the seismic hazards in the region two reverse faults the manas and hutubi faults in the northern foreland basin were investigated due to past faulting events along these faults the terrace treads along the manas river were ruptured forming fault scarps several meters in height loess deposits were trapped and preserved at the surface ruptures along these scarps the thickness of the trapped loess is dependent on the size of the ruptures the minimum and maximum ages of these scarps are constrained by dating the loess preserved at the surface ruptures and the terrace treads respectively using the quartz optically stimulated luminescence osl dating technique our dating results suggest that the loess trapped at the ruptures was deposited from the early to mid holocene at the hutubi fault and from the mid to late holocene at the manas fault the vertical displacements of the faults were evaluated by measuring the topographic profiles across the investigated fault scarps using the differential global position system dgps our results suggest that during the late quaternary in the studied region the vertical slip rates of the manas fault were between 0 74 mm yr and 1 6 mm yr while the hutubi fault had a much lower vertical slip rate between 0 34 mm yr and 0 40 mm yr the tectonic implications of our results are discussed

late pleistocene shortening rate on the northern margin of the yanqi basin southeastern tian shan nw china abstract how strain is distributed and partitioned on individual faults and folds on the margins of intermontane basins remains poorly understood the haermodun ha anticline located along the northern margin of the intermontane yanqi basin on the southeastern flank of the tian shan preserves flights of passively deformed alluvial terraces these terraces cross the active anticline and can be used to constrain local crustal shortening and uplift rates geologic and geomorphic mapping in conjunction with high resolution dgps topographic surveys reveal that the terrace surfaces are perpendicular to the fold s strike and display increased rotation with age implying that the anticline has grown by progressive limb rotation combined with the open sinusoidal curve model and excess area method we calculated uplift and shortening values for each terrace since abandonment using the published exposure ages of each terrace we found the vertical uplift rate gradually decreased from 0 43 to 0 11 mm a whereas the shortening rate remained constant at 0 3 mm a since the anticline began to grow a fresh fault scarp 0 4 0 1 m high is visible along the southern portion of the ha anticline and is interpreted to be the most recent evidence of seismic activity using an estimated rupture area and the length of the fresh offset created by this earthquake we estimate that the main thrust underlying the ha anticline has generated moderate m

chironomid responses insect diptera to younger dryas and holocene environmental changes in a river floodplain from northern france st momelin st omer basin lateglacial to holocene subfossil chironomids from the st omer basin at st momelin northern france were analysed at the end of the lateglacial stratigraphic and chironomid sequences indicate a shallow oligotrophic and slow flowing freshwater stream with abundant aquatic macrophytic vegetation cold water adapted taxa indicate a cold climate during the early holocene from about 9500 to 7700 conventional radiocarbon yr bp climate improvement is marked by an increase in warm water adapted taxa and a decrease in cold water fauna however the cold water fauna persist probably because of both the instability and continentality of the climate during the mid holocene from about 7700 to 6000 bp the marine transgression strongly influenced the river s hydrological regime and consequently the chironomid assemblages at that time eutrophic warm and shallow stagnant water conditions occured throughout the basin from 6000 to 3200 bp the st momelin basin was subjected to a marine regression chironomids indicate a hydrological regime marked by an alternance of phases with either a dominance of rheophilous or limnophilous fauna during this period equivalent percentages of warm and cold adapted taxa may be explained by cold water input in context of a temperate climate

spatiotemporal patterns of the late quaternary deformation across the northern chinese tian shan foreland abstract the investigations of active deformation across a mountain foreland can provide important insights into the pattern and dynamics of deformation of an active orogenic belt here we focus on the spatiotemporal patterns of the late quaternary deformation along the north piedmont of the chinese tian shan a mountain range formed by the ongoing india asia collision by using a terrace as the reference and applying the area conservation method the holocene shortening rate of the halaande anticline a fold of the distal structure belt iii in the foreland is estimated to 2 14 0 24 mm yr for the first time similarly we re calculate the holocene shortening rates of the other anticlines of belt ii iii using the magnitude of shortening documented by river terraces and the terrace formation ages published previously the summed holocene 103 year timescale shortening rates of individual anticlines along n s transects are 2 4 mm yr consistent with the late pleistocene 104 year timescale shortening rate but about 2 6 times higher than the long term 106 year timescale average shortening rate of 1 mm yr during the past several million years together with the shortening rates of individual anticlines at the 103 year 104 year and 106 year scales these observations imply that the deformation across the northern chinese tian shan foreland has accelerated since at least late pleistocene by summing the late quaternary rates of shortening in the southern chinese tian shan foreland 4 5 mm yr and the intermontane basins in the hinterland of the tian shan 2 mm yr the late quaternary rate of shortening across the tian shan range between longitude 83 e and 87 e amounts to 9 0 1 0 mm yr approximately matching the modern shortening rate of 8 mm yr derived from the gps measurements these results imply i that the deformation across the tian shan range and its foreland basins between longitude 83 e and 87 e could have not been changed significantly since at least late pleistocene ii that in the northern chinese tian shan foreland the recurrence interval of paleoseismic events during the past tens of thousands of years may be determined by a linear extrapolation of the holocene or even geodetic rate of deformation

oyster patch reefs as indicators of fossil hydrocarbon seeps induced by synsedimentary faults abstract the late jurassic deposits of the boulonnais area n france represent the proximal lateral equivalent of the kimmeridge clay formation they accumulated on a clastic dominated ramp subject to synsedimentary faulting as a result of the atlantic ocean rifting in the gris nez cape area i e close to the northern border fault zone of the jurassic basin the late jurassic sequence contains small dimensioned oyster patch reefs nanogyra nana embedded in a microsparitic calcite matrix 13 c measurements carried out within both the matrix and the shells display significantly lower values in the matrix compared to the oyster shells which suggests that the carbonate matrix precipitation was involving a carbon source different from marine dissolved inorganic carbon most probably related to sulfate reduction which is evidenced by light 34 s in pyrites similarities but also differences with lucinid rich bioconstructions namely the late jurassic pseudo bioherms of beauvoisin se france suggest that the patch reefs developed at hydrocarbon seeps are related to synsedimentary faults the extensional block faulting segmentation of the northern margin of the boulonnais basin in late jurassic times is thus believed to have induced a sort of small dimension hydrocarbon seepage field recorded by the patch reef distribution

middle pleistocene seismically induced clay diapirism in an intraplate zone western brittany france the brittany region of france is located in a low seismicity intraplate zone most of the instrumented earthquakes are limited to a shallow crustal depth without surface rupture a paleoseismological analysis was performed on deposits on the crozon peninsula and in the elorn estuary we highlight hydroplastic deformations induced by liquefaction leading to clay diapirism which were likely triggered by past earthquakes this diapirism seems to be frequent in continental nonconsolidated sediments and to develop on the inherited tectonic structures when a shallow water table and confining layers exist timing of deformation is dated using paleoenvironmental data and electron spin resonance and infrared stimulated luminescence dating methods two seismic periods were identified in western europe during early marine oxygen isotope stage mis 10 380 ka and early mis 8 280 265 ka the lack of similar deformations affecting the holocene tidal deposits in the bay of brest suggests that the magnitude of the triggering paleoearthquakes is probably higher m w 6 than the recent events m w 5 4 these unusual intraplate major paleoearthquakes need specific factors affecting the far field crustal stress loading to be triggered such as a brief acceleration of the africa eurasia lithospheric plate convergence glacio isostatic stress perturbations associated with the onset of major glaciations in northern europe or other processes induced by orbital forcing

middle paleocene uplift of the brabant massif from central belgium up to the southeast coast of england during the middle paleocene laramide phase several basins in europe experienced subsidence while others experienced uplift previous studies have shown that during the laramide phase some basins surrounding the brabant massif experienced subsidence into shallow depocentres this study discusses how the brabant massif simultaneously experienced uplift along its wnw ese caledonian structural axis from central belgium in the east up to the southeast coast of england ipswich in the west uplift resulted in erosion of the formerly deposited chalk group on top of the axis of the brabant massif the erosion products of the chalk group were reworked in the latest danian to earliest thanetian deposits that filled the surrounding depocentres early to middle thanetian pulsed marine transgressions caused flooding and deposition across the entire region including the previously uplifted axis of the brabant massif the depositional thicknesses however indicate that the axis of the brabant massif remained a relative high up to the middle thanetian both the geometry and timing of the middle paleocene vertical surface movements of the brabant massif and surrounding areas are very similar to those described for other structural entities in central and northern europe despite their often strongly differing mesozoic tectonic evolutions we discuss several mechanisms that might have triggered these vertical surface movements of which lithospheric folding seems the most likely

a hybrid efficient method to downscale wave climate to coastal areas long term time series of sea state parameters are required in different coastal engineering applications in order to obtain wave data at shallow water and due to the scarcity of instrumental data ocean wave reanalysis databases ought to be downscaled to increase the spatial resolution and simulate the wave transformation process in this paper a hybrid downscaling methodology to transfer wave climate to coastal areas has been developed combining a numerical wave model dynamical downscaling with mathematical tools statistical downscaling a maximum dissimilarity selection algorithm mda is applied in order to obtain a representative subset of sea states in deep water areas the reduced number of selected cases spans the marine climate variability guaranteeing that all possible sea states are represented and capturing even the extreme events these sea states are propagated using a state of the art wave propagation model the time series of the propagated sea state parameters at a particular location are reconstructed using a non linear interpolation technique based on radial basis functions rbfs providing excellent results in a high dimensional space with scattered data as occurs in the cases selected with mda the numerical validation of the results confirms the ability of the developed methodology to reconstruct sea state time series in shallow water at a particular location and to estimate different spatial wave climate parameters with a considerable reduction in the computational effort

the basse normandie duplex boulonnais n france evidence for an out of sequence thrusting overprint abstract the thrust sheets outcropping in the basse normandie quarry near the hydrequent village boulonnais n france represents an exceptionally well exposed section of the nw european variscan thrust front these structures developed in the footwall of the main hydrequent thrust have been often described as a classic example of a duplex structure only the lower part of the structure satisfies however the geometric and kinematic criteria defining a duplex and more precisely an intraformational hinterland dipping duplex the upper thrust sheets of the imbricate stack exhibit a much more complex pattern of deformation than a simple piggy back duplication of the same rock sequence restoration of these thrust sheets based upon the definition of two marker beds as well as the analyses of fold thrust relationships and strain markers argues for a late ne verging thrust event that progressed within the thrust system from the tip of the upper thrust sheets towards the hydrequent thrust in a local break back style of thrust propagation this out of sequence thrusting event induced refolding and cross cutting of the forelimb of a hangingwall anticline developed previously above the footwall ramp of the nne verging basal thrust of the structure within the whole thrust system the lower duplex represents only a minor structure developed during the initial phase of thrusting in the foreland of the major anticline as a frontal second order duplex the structural data presented in this paper illustrate the tectonic processes acting within the deformed zones lying in the footwall of major thrusts and emphasize the out of sequence style of thrust migration that arises from the sequential blocking of thrust propagation towards the foreland

book reviewgeothermal energy the potential in the united kingdom r a downing and d a gray editors h m s o norwich 1986 xiii 187 pp stg 20 00 paperback