fault reactivation in brittle viscous wrench systems dynamically scaled analogue models and application to the rhine bresse transfer zone abstract analogue experiments on oblique rifting and subsequent transpressional reactivation were performed with two layer slabs of sand and silicone in this brittle viscous system transtensional and transpressional wrench faulting was induced by movements of a basal rigid plate the dynamically scaled analogue models are confronted with the structural evolution of the rhine bresse transfer zone rbtz that linked palaeogene rifting in the upper rhine and bresse grabens and that appears to have been transpressively reactivated in neogene to recent times fault patterns produced in the sand layer above the basal silicone layer are compared with structural elements in the sedimentary cover separated from the basement by an evaporitic decollement layer in order to investigate strain rate dependence of fault reactivation and graben inversion transpressional shortening was performed under different displacement rates experimental results suggest that the reactivation of pre existing structures in a brittle cover above a viscous decollement is strongly dependent on the strain rate within the viscous layer under low to intermediate displacement rates 2 6 cm h 1 deformation concentrates within the basal viscous layer and former normal faults within the cover are not reactivated the reactivation at higher displacement rates 5 cm h 1 results in a complete inversion of graben structures within the cover ongoing shortening produces lobed thrust fronts which crosscut pre existing normal faults late pliocene to recent en echelon aligned folds and isolated thrust faults in the cover of the rbtz are attributed to thick skinned reactivation of basement faults a comparison of natural and experimentally obtained structures suggests that fault reactivation occurred under low displacement rates

controls on the geometry of transfer zones in the suez rift and northwest red sea implications for the structural geometry of rift systems two main types of transfer zones are mapped in the suez rift and the northwestern red sea these are transfer zones between indi vidual faults fault to fault transfer zones f f tz and transfer zones between half grabens with different fault domains half graben to half graben transfer zones h h tz relay ramps and linking transfer faults are two main recognized types of f f tz different varieties of these f f tz have the form of en echelon fault belts with single or mixed polarity tilted fault blocks at rift offsets and zigzag fault arrays at major fault or rift jumps relay ramps transfer throw between overlapping normal faults of the same polarity linking transfer faults join normal faults that have the same polarity with no overlapping segments leading to a characteristic zigzag pattern if the linked faults are listric local anticlines and synclines develop at the corners of the zigzag fault array three h h tz in the suez rift and northwest red sea show the effect of prerift structures both faults and major folds on the location orientation and style of deformation of the transfer zones of continental rifts the widest one of these three h h tz 40 60 km has a broad antiformal structure lying between the overlapping ends of the listric faults bounding the two linked half grabens and is deformed by dip slip normal faults of opposite polarity the other two h h tz reactivate prerift faults by strike slip faulting due to the angular relationship between these faults and the direction of extension in the rift

petrologic and zircon u pb geochronological characteristics of the pelitic granulites from the badu complex of the cathaysia block south china abstract the recognition of the indosinian orogeny in the south china block has been controversial and difficult because of strong weathering and thick cover high temperature ht and high pressure hp metamorphic rocks related to this orogeny were considered to be absent from this orogenic belt until the recent discovery of eclogite and granulite facies meta igneous rocks occurring as lenses within the meta sedimentary rocks of the badu complex however metamorphic state of these meta sedimentary rocks is still not clear besides there have been no geochronological data of ht pelitic granulites previously reported from the badu complex this paper presents petrographic characteristics and zircon geochronological results on the newly discovered kyanite garnet gneiss pyroxene garnet gneiss and the ht pelitic granulites sillimanite garnet gneiss mineral assemblages are garnet sillimanite ternary feldspar plagioclase quartz biotite for the ht pelitic granulite kyanite ternary feldspar garnet sillimanite plagioclase quartz biotite for the kyanite garnet gneiss and garnet biotite pyroxene plagioclase ternary feldspar quartz for the pyroxene garnet gneiss respectively decompressional coronas around garnet grains can be observed in all these pelitic rocks typical granulite facies mineral assemblages and reaction textures suggest that these rocks experienced hp granulite facies metamorphism and overprinted decompression along a clockwise p t loop results from integrated u pb dating and ree analysis indicate the growth of metamorphic zircons from depleted heavy ree sources 100 50 chondrite compared with detrital zircons derived from granitic sources typically 1000 chondrite metamorphic zircons in hp granulite exhibit no or subdued negative eu anomalies which perhaps indicate zircon overgrowth under eclogite facies conditions the zircon overgrowth ages range from 250 to 235 ma suggesting that hp granulite eclogite to granulite facies metamorphism of these supracrustal rocks occurred in the early middle triassic based on the presence of hp granulite facies pelitic rocks it is inferred that significant underthrusting was involved during the indosinian orogeny which introduced these supracrustal rocks to lower crustal levels

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

tectonics and topography for a lithosphere containing density heterogeneities the purpose of this paper is to clarify the dynamic role of lithospheric density heterogeneities in particular with respect to mountain building and other processes of intraplate deformation density anomalies within or just beneath the lithosphere constitute major sources for tectonic stress fields the product of their magnitude by their depth is shown to characterize their ability to induce deformation this rule of the density moment directly yields the lithospheric thickening or thinning rate when applied to structures of large lateral extent for anomalies of lateral extent that is small in comparison with their depth the deformation is vertically inhomogeneous and has been computed with the help of simple physical models of a stratified viscous newtonian lithosphere the analytical treatment is based on fourier transform continent continent collision thickens not only the crust but the entire lithosphere the cold root underlying a mountain chain induces strong regional compressive stresses able to sustain the mountain bulding process without further help from forces transmitted from far away thus the continental lithosphere is in a somewhat metastable mechanical state adiabatic i e rapid thickening or thinning tends to grow further once initiated tectonic phases of strong compression correspond to the climax of such instabilities the response of models with cold lithospheric roots of various intensities has been computed both in two and three dimensions they yield velocity distributions and stress fields instructive comparisons are made with earthquake focal mechanisms and in situ stress measurements in the alpine and appalachian regions in the presence of lateral variations of the mechanical properties of the lithosphere the tectonic style is not only function of the local topography and of the nature of its compensation deformations in neighbouring provinces are coupled as shown by 3 dimensional models for example thickening sustained by a cold lithospheric root may generate extension in peripheral zones of weakness these last results illustrate the point that the computation of regional tectonic stresses requires the knowledge of the density anomalies within the lithosphere on the one hand and of geometrical constraints related to lateral mechanical heterogeneities on the other

comparative tertiary stratigraphy of the rhine graben bresse graben and molasse basin correlation of alpine foreland events abstract comparative tectonostratigraphic analysis of the tertiary middle eocene pliocene of the rhine bresse graben system and the western molasse basin demonstrates the occurrence of eleven correlative sequences crf i xi these show a close relationship between intra basinal tectonics and depositional history their punctuated sediment accumulation can be related to phases of extra alpine taphrogenesis and alpine orogenesis and to coeval eustatic changes in sea level apparent simultaneity in rift and foredeep sequence development structural deformation and global change in sea level suggests a common causal control in which the development of the alps played an important role

the jura mountains an active foreland fold and thrust belt abstract recently completed in situ stress measurements using the borehole slotter at 33 new test sites within the swiss and french jura mountains combined with previously published stress data allow a detailed description of the contemporary state of stress in this fold and thrust belt and the adjacent foreland five stress provinces can be recognized with two different general orientations of maximum horizontal stress sh 1 the central and southwest provinces with a nnw sse to nne ssw orientation 2 the east northwest and southeast provinces with an e w to nw se orientation stress magnitudes are in general higher in the southern than in the northern jura mountains characteristic of the northern jura is an e w trending zone of low stress magnitudes which can be traced from the bresse depression south of besancon to the eastern end of the jura northwest of zurich boundaries of stress provinces show poor agreement with boundaries of tectonic units in the jura in addition stress provinces extend beyond the boundaries of the jura mountains into their foreland furthermore palaeo stress orientations show large discrepancies with respect to the contemporary stress orientation these findings are considered to indicate a termination of jura thin skinned foreland tectonics which probably took place some time between 9 and 4 ma according to palaeontological and tectonic evidence it is suggested that a new style of tectonics has commenced in the jura mountains deforming both the basement directly below the jura fold and thrust belt and the cover rocks in a similar mode

evolution of the stress field pattern in the south of the rhine graben from the eocene to the present a stress field evolution from the eocene to the present is proposed for the southern part of the rhine graben stress tensor determinations are supported by striated microfaults and calcite twin lamellae analyses both methods lead to the determination of 1 a an e w extension contemporaneous with the opening of the graben and 2 b a n s compressive event which may be related with alpine tectonics it is shown that a n s compressive event occurred prior to the oligocene extension a permutation between the 1 and 2 axes is proposed to explain the transition between compression and extension a 1 2 inversion during the oligocene is compatible with compression in the southern part of the rhine graben infilling horizontal 1 and extension vertical 1 more to the north during the miocene the jura emplacement corresponds to a n s compression in this area there is no significant variation of the 1 direction south of the rhine graben from the eocene to the late miocene the 1 direction only turns to a n140 direction during the pliocene or the quaternary

quaternary transfer faulting in the taiwan foothills evidence from a multisource approach abstract the major structures of the western foothills of taiwan mainly consist of nne ssw trending folds and imbricated west vergent thrust systems the additional occurrence of n140 e striking oblique structures was revealed through a multisource approach involving a digital elevation model dem a study of drainage network anomalies aerial photographs side looking airborne radar slar images and spot p and landsat images these structures are described from north to south based on new field analyses including stratigraphy and tectonics studies they are also compared to seismic data and geodetic reconstruction in order to evaluate their present day activity these n140 e major morphostructures are interpreted as left lateral transfer fault zones either inherited from the eurasian passive margin and or newly formed in the cover in response to the presence of basement highs within the foreland basin peikang and kuanyin highs the sanyi and the chishan transfer fault zones display a high seismic activity the distribution of earthquakes and the related focal mechanisms confirm the left lateral movement along n140 e directions the chiayi chishan and fengshan fault zones act presently as transfer fault zones as indicated by gps data the associated n70 e to n100 e trending faults result from the reactivation of normal faults of the eurasian passive margin as right lateral strike slip faults in the foothills during the plio quaternary collision in taiwan we conclude that multisource and multiscale geomorphic studies combined with tectonic analysis in the field yield a significant contribution to the understanding of the structural and kinematic development of the western foothills at the front of the taiwan collision belt

geodynamic model for the palaeozoic crustal consolidation of western and central europe abstract the crystalline basement of western and central europe consists of a mosaic of crustal elements which were consolidated during pre grenvillian the grenvillian dalslandian morarian cadomian caledonian and hercynian orogenic cycles contemporaneous with the caledonian suturing of the precambrian laurentia greenland and fennosarmatian shields a number of gondwana derived cadomian micro cratons were accreted to the southern margin of laurasia following the late caledonian paroxysm the devonian and early carboniferous evolution of europe was dominated by continued northward subduction of the proto tethys plate at an arc trench system parallelling the southern margin of laurasia the accretion of additional gondwana derived continental fragments back arc rifting and a sinistral translation of major proportions between the laurentia greenland and the fennosarmatian sub plates the acadian and bretonian orogenies were of the pacific type the visean collision of gondwana with laurasia marked the onset of the himalayan type variscan orogeny during which collision related compressive stresses overpowered the devonian early carboniferous back arc rift systems and caused the development reactivation of a subduction zones the central armorican and saxothuringian successor basins became folded and destroyed during the latest visean whilst the variscan foredeep became scooped out in part by nappes involving the basement during the late westphalian major crustal shortening during the variscan diastrophism was accompanied by the anatectic remobilisation of subducted crustal and upper mantle material and a widespread syn and late orogenic magmatism the latest carboniferous early permian reorientation of the convergence direction between gondwana and laurasia induced the development of a complex wrench fault system transecting the variscan fold belt and an extensive post orogenic volcanism the hypotheses summarised here require confirmation by further palaeomagnetic and radiometric data and faunal analyses

strain displacement and rotation associated with the formation of curvature in fold belts the example of the jura arc abstract a new simplified genetic classification scheme for arcuate fold thrust belts is proposed based on total strain patterns and displacement vector fields we distinguish three extreme end member models 1 oroclines pure bending of an initially straight belt 2 piedmont glacier with divergent transport directions and 3 primary arcs a simple geometric model set up for the simulation of strain patterns in primary arcs with uniform transport direction demonstrates that divergent strain trajectories and rotations of passive marker lines do not require any divergence in displacement directions these often quoted arguments are insufficient for the identification of oroclinal bending or piedmont glacier type of arc formation only three dimensional restorations of an arc provide the critical information about displacement directions in their absence arc parallel stretches and rotations in comparison with total strains provide the most useful criteria for the distinction of arc formation modes as an example the jura fold thrust belt of the external alps is discussed a large set of strain data includes total shortening estimates based on balanced cross sections local strain axes orientations from the inversion of fault populations homberg c 1996 unpublished phd thesis universite de paris vi france tectonic stylolites and micro strains from twinning in sparry calcite strain trajectories maximum shortening direction computed from these data define a strongly divergent fan with a 90 opening a complete displacement vector field for the entire jura has been determined from balanced cross sections augmented with three dimensional block mosaic restorations philippe y 1995 unpublished phd thesis universite de chambery france displacement vectors diverge by about 40 markedly less than strain trajectories the non parallelism between strain trajectories and transport directions indicates that considerable wrenching deformation did occur in both limbs of the jura arc paleomagnetically determined clockwise rotations of 0 13 from ten sites kempf o et al terra nova 10 6 10 behind the right hand half of the jura arc and two sites with a combined 23 anticlockwise rotation behind the left hand half of the arc are and additional argument in favor of such a wrenching deformation we conclude that the jura arc formed as a primary arc with a minor component of piedmont glacier type divergence in transport directions

tectonics and plate tectonics model for the variscan belt of europe abstract a plate tectonics model is presented to explain the tectonometamorphic characteristics of the european variscides after the closing of two oceanic domains by two sided subduction 500 420 ma and obduction 420 380 ma collision of the european and african continental plates occurred we propose that the subsequent complex intracontinental deformation 380 290 ma is the result of a double subduction of the continental lithosphere accompanied by crust mantle decollement this mechanism explains the progressive crustal thickening and migration of the deformation through time from the sutures toward the external parts of the variscan belt accounting for this model and for the relationships between the european variscides and the other paleozoic peri atlantic belts caledonides appalachian mauritanides and morocco we infer the relative positions of africa america and europe between the silurian and the permian

from orientation to magnitudes in paleostress determinations using fault slip data abstract determinations of reduced stress tensors using fault slip data yield the orientation of principal stress axes and the ratio of the differences between principal stress magnitudes the use of rupture and friction laws allows determination of the two remaining unknowns that is the reconstruction of the complete stress tensor taking into account the depth of overburden brings an additional constraint the method is applied and discussed in the case of the hoover dam site western u s a where large data sets and rock mechanics information are available differences between intact sample and rock mass properties account for apparent disagreements between paleostress levels determined in similar tectonic environments pore pressure plays an important role where information about pore pressure is absent zero and hydrostatic pore pressure cases should be considered as limits

internal structure of the dead sea leaky transform rift in relation to plate kinematics abstract the structures along the dead sea transform rift are related to the motions of the sinai and arabia plates which border it and to the irregularities of their boundaries the total slip was 105 km left lateral but the present structures were formed mainly during the last 40 km of slip which probably occurred in the plio pleistocene along the southern half of the transform the strike slip motion takes place on en echelon faults this produces rhomb shaped grabens or pull aparts which are sometimes composite and in which there is local crustal separation thus much of the transform is leaky these structures occur in a morpho tectonic rift valley delimited by normal faults which express a small component of transverse extension along a few segments the shape of the transform is such that lateral motion produces local transverse compression the geometric relations of the structures along the transform define an eulerian pole of relative plate motions at 32 8 n 22 6 e 0 5 the older motion was somewhat different and is described by a pole located about 5 west of the above then the component of transverse extension and crustal separation was much smaller than now while local transverse compression was more important the northern half of the dead sea transform has an irregular shape and the bordering plates did not remain rigid as lateral motion continued here transverse compression is often important

intraplate deformation by block rotation and mesostructures along the dead sea transform northern israel combined analysis of mega and meso structures yield the strain inferred stress and tectonic history of the margin of the sinai sub plate in northern israel along the dead sea transform three major stress regimes were developed and have affected the region since the middle miocene one is regional and controlled the left lateral shear along the dead sea transform this one has been active since post early miocene is characterized by 1 trending c 345 and deformed the plate margin by horizontal shear and contemporaneous block rotation this style of deformation is similar to simple shear the second one was local and may be subdivided into distinct stress and strain domains it was characterized by 1 trending e w and 3 trending n s which produced a conjugate set of strike slip faults the region underwent n s elongation by horizontal shear and block rotation similar to the pure shear mechanism this stress regime was active in late miocene to early pliocene time the third and youngest stress regime is extentional with 1 vertical and 3 oriented n s this one has been active since post middle pliocene time producing e w normal faults and minor n s elongation the second and third stress regimes show local distribution and developed as a consequence of the bent geometry of the transform vis a vis the plate slip vector finite element and photoelastic models predict the development of local stress fields and elongation of the plate margin parallel and subparallel to the transform plate boundary the strain of the plate margin in northern israel and southern lebanon indicate remarkable elongation parallel to the dead sea transform by a factor of 1 5 2 1 since the miocene this process of intraplate deformation and the consequent strain is unique to the parts of the plate margin which are adjacent to the bent segment of the transform

structural inheritance and coastal geomorphology in sw brittany france an onshore offshore integrated approach abstract the variscan crystalline basement exposed along the sw brittany coast recorded extensive long term planation processes during mesozoic times detailed onshore offshore mapping 600 km2 in the penmarc h concarneau granitic coastal area reveals a km scale deeply fractured submarine rocky shelf high resolution offshore imagery bathymetry and seismic reflection dataset combined to structural field investigations on these surfaces allow us to identify a preserved network of both ductile and brittle structures the inherited fault pattern is dominated by the n160 e trending and long lived concarneau toulven fault zone ctfs that separates two distinct morphostructural blocks and strongly influences the seaward limit of the concarneau submarine rocky shelf as well as the linear coastline of the concarneau embayment the structural imprint of the ctfs decreases progressively westwards with respect to a composite network of large scale n50 e and n140 e oriented faults bounding the seaward edge of the penmarc h rocky shelf the latter in turn splits into three large scale blocks along n50 e la torche fault ltf n140 e saint guenole fault sgf and n160 e trending normal faults the morphostructural evolutionary model applied here to the penmarc h concarneau granitic coastal area resulted from the combined effects of structural variscan inheritance and post variscan tectonics paleo stress analysis of striated fault planes indicates three main cenozoic tectonic events inferred to have operated from eocene to post oligocene times the 3d architecture of the concarneau embayment as a rocky shelf partially sealed with quaternary sediments chiefly resulted from the reactivation of the ctfs during eocene and oligocene times further west the surface of the penmarc h rocky shelf was tilted southeastward by the brittle reactivation of the ltf and dissected by a horst graben network post oligocene in age the present day morphology of the penmarc h and concarneau domains depends on distinct driving processes the concarneau n160 e coastline is clearly controlled by tectonic processes via the ctfs while the penmarc h headland land sea contact appears to have been shaped by post cenozoic eustatism

multiple fault reactivations within the intra continental rhine bresse transfer zone la serre horst eastern france abstract thermochronological structural and kinematic analyses demonstrate the influence of late paleozoic basement structures on the localization and evolution of the rhine bresse transfer zone rbtz a central segment of the european cenozoic rift system zircon and apatite fission track data indicate that the paleozoic crystalline basement and its permo triassic cover exposed in the la serre horst experienced a middle jurassic to early cretaceous heating event which was followed by two distinct periods of cooling a first cooling event occurred in the early cretaceous and is probably related to thermal relaxation a second one started at around 38 ma is interpreted to reflect exhumation that was induced by fault reactivation along the late paleozoic burgundy trough system during eocene oligocene rifting and the formation of the rbtz this fault reactivation resulted in a complex fault pattern and local stress field perturbations in the surroundings of the pre existing horst structure substantial extension was achieved by ene wsw striking normal faults that trend highly oblique to the dominant strike of the rhine and bresse graben rifts seismic reflection data show that these major normal faults are typically associated with extensional flexures and oriented parallel to pre existing late paleozoic basement faults of the burgundy trough paleostress analyses yield overall nw se extension during the eo oligocene slightly oblique to the structural trend of the rbtz and additionally local stress field perturbations induced by the reactivation of pre existing faults reactivation of paleozoic structures in the rbtz is of extensional rather than of strike slip character indicating that the rbtz is forming a separate oblique graben segment within the european cenozoic rift system rather than a sinistral strike slip transform zone supposedly connecting rhine and bresse graben structures

an inverse problem in microtectonics for the determination of stress tensors from fault striation analysis abstract a method is proposed to compute some characteristics of a possible stress tensor related to striations measured in a given faulted area if several tectonic phases are responsible for the striations the method separates and determines the successive stress tensors the iterative algorithm consists of alternatively a sorting the data attributed to a tectonic phase and b computing the characteristics of the stress tensor of this phase the method is tested using an application to synthetic and actual data

stress fields about strike slip faults inferred from stylolites and tension gashes abstract in general the long axis of the tension gashes and stylolitic columns developed in limestones during a single phase of compressional deformation occur parallel to the direction of the maximum compressive stress 1 this is the case in the languedoc for structures developed in the jurassic limestones during the n s pyrenean compression exceptionnally however these microstructures turn in direction and become oblique even orthogonal one to the other probably as a consequence of a variation in intensity and direction of the stress field at the end of a microfault this mechanism also occurs in a larger scale structure involving segments of pre tectonic joints that act as en echelon microfaults in a brittle kink band equivalent to a peculiar type of potential wrench fault

feedback between erosion and active deformation geomorphic constraints from the frontal jura fold and thrust belt eastern france a regional tectono geomorphic analysis indicates a pliocene to recent rock uplift of the outermost segment of the jura fold and thrust belt which spatially coincides with the intra continental rhine bresse transfer zone elevated remnants of the partly eroded middle pliocene sundgau foret de chaux gravels identified by heavy mineral analyses allow for a paleo topographic reconstruction that yields minimum regional latest pliocene to recent rock uplift rates of 0 05 0 02 mm year this uplift also affected the pleistocene evolution of the ognon and doubs drainage basins and is interpreted as being tectonically controlled while the ognon river was deflected from the uplifted region the doubs deeply incised into it focused incision of the doubs possibly sustained ongoing deformation along anticlines which were initiated during the neogene evolution of the thin skinned jura fold and thrust belt at present this erosion related active deformation is taking place synchronously with thick skinned tectonics controlling the inversion of the rhine bresse transfer zone this suggests local decoupling between seismogenic basement faulting and erosion related deformation of the mesozoic cover sequences

favoured states of palaeostress in the earth s crust evidence from fault slip data abstract in a major survey of published palaeostress estimates obtained by the use of fault slip data over 2000 stress tensors from shallow crustal levels have been compiled the results are derived from regions where deformation is dominated by brittle processes and consist of incomplete stress tensors in which the orientations of the principal stresses 1 2 3 are known together with the stress ratio 2 3 1 3 the orientations of the stress axes display a preferred orientation with a tendency for one of the axes to be vertical this accords with anderson s assumed standard state stress configuration near to the earth s free surface although the tendency is strong there are frequent deviations from the arrangement in 25 of cases the steepest stress axis deviates by more than 25 from the vertical in undertaking studies of palaeostress it would be therefore unwise to use methods that assume a priori one vertical stress axis unless previous local results indicate this to be the case normal strike slip and thrust stress arrangements with 1 2 and 3 as the steepest stress respectively occur in the database with frequencies approximately in the ratio 2 2 1 in the compiled results the raw stress ratios which have a theoretical range from 0 to 1 show a lack of very high values and to a lesser extent very low values this suggests that triaxial stress states are more common than axial compression deviatoric stress and axial tension deviatoric stress however this relative abundance of triaxial stress states is considered to be a natural feature of a uniform distribution of stress tensors in addition there is a marked bias in the collated ratios towards values less than 0 5 and this is expressed by an overall mean of 0 39 several possible explanations for the distribution of stress ratios are discussed these explanations are related to the tendency for tectonic deformation to be of plane strain type coupled with volume change and to the fact that gravitational loading makes an important contribution to the state of stress in the crust

the central european graben system rifting imitated by clay modelling abstract central europe is traversed by an active graben belt between the north sea and the mediterranean along with a lateral rift rift offset between some segments along these offsets connecting the individual segments specific patterns have been observed which may be physiographically compared with transform faults a series of clay experiments were carried out to understand rhinegraben type graben formation especially the transform like features were modelled to learn more about the kinematics of transform faulting in the continental domain it has been attempted to approach natural structural and lithological boundary conditions of graben formation by varying the experimental conditions in such a manner that experimental and in situ conditions resemble in an optimal way the experiments are related to the paleogene extensional stage of the evolution of the rift system and do not consider the pliocene to recent kinematics of shear rifting

the auriga nunataks shear zone mesozoic transfer faulting and arc deformation in northwest palmer land antarctica the auriga nunataks shear zone places new tectonic and temporal constraints on the mesozoic evolution of west antarctica the shear zone is a long lived arc orthogonal ductile transfer fault that preserves a history of regional mesozoic compressional basement deformation and extensional arc pluton emplacement in the antarctic peninsula magmatic arc it forms an east west trending positive flower structure 2 4 km wide exposed along 5 km of strike marble graphite bearing pyroxene granulite granodiorite diorite amphibolite and gabbro are deformed to mylonite and marble hosted tectonic breccia the mesozoic history of the shear zone is interpreted as follows emplacement of granodiorite diorite at circa 206 ma during early jurassic dextral transtension and metamorphism that peaked at circa 188 ma d1 brecciation of marble and mylonitization of gneiss by late jurassic to early cretaceous sinistral shear during the peninsula wide palmer land orogeny d2 early cretaceous dextral transtension with emplacement of gabbro and garnet leucogranite between 140 and 135 ma d3 and mid cretaceous ocean vergent thrusting and sinistral transpression between 125 ma and 80 ma with a peak at circa 110 ma that folded mylonitized and brecciated preexisting plutonic and metamorphic rocks d4 this is responsible for the current geometry of the shear zone the auriga nunataks shear zone transferred motion between arc parallel compressional and extensional structural elements and by hosting plutons appears to have acted like a leaky transform fault during episodes of regional extension

etude des images landsat de la zone transformante rhin saone france l etude des images landsat de la zone transformante entre les fosses de la saone et du rhin donne un echantillonage significatif de la facturation reparti sur une grande surface et revele l existence de plusieurs lineaments ceux ci sont interpretes comme des accidents profonds delimitant au paleogene un couloir de cisaillement senestre transformant n 80 au dessus duquel la couverture se fracture selon un systeme de riedel on reconnait egalement en surface des failles hercyniennes de direction varisque et des failles rhenanes submeridiennes liees a l ouverture des fosses

tertiary tectonics of the dannemarie basin upper rhine graben and regional implications recently released seismic reflection data together with previous seismic and well data are used to describe the development of the dannemarie basin in the sw end of the upper rhine graben the dannemarie basin was formed during the main rifting phase of the upper rhine graben as an asymmetrical graben trending ne sw post rift tectonism shifted the depocenter southward and changed the overall shape of the basin miocene jura compression did not result in the formation of folds as in the adjacent mulhouse horst strike slip faulting was dominant in the post rift period and new faults were created most notably the north trending and transpressional belfort fault the boundary of the dannemarie basin with the vosges mountains is part of a restraining bend which may account for the uplift of the southernmost part of the vosges mountains

interaction between perpendicularly trending thrust wedges and its impact on foreland deformation insights from analogue modelling abstract in this work we used analogue models in order to better understand how two orthogonal fold and thrust belts may interact in the foreland and influence the geometry and kinematics of the resulting structures our experimental device has two vertical mobile backstops oriented perpendicular with respect to each other independent and moving coevally with variable or equal velocities there are strong contrasts between our models results and thrust wedges generated using a unique indenter and simple convergence thrust wedge deformation in front of two perpendicular indenters overlying a basal viscous decollement progressed following two major stages i independent growth of each tectonic wedges then ii formation of major oblique and continuous structures that nucleated in the foreland of both indenters in some models the two indenters moving at different velocities favoured the interference and superimposition of structures strain partitioning structure curvature and vertical axis rotation comparison with the friulian venetian basin southern alps and the altomira loranca thrust belt iberian chain central spain supports the hypothesis that foreland deformation can strongly vary if a basal viscous decollement is present during the interaction of two mutually indenters

spatio temporal behaviour of continental transform faults implications from the late quaternary slip history of the north anatolian fault turkey the slip history of the north anatolian fault naf is constrained by displacement and age data for the last 550 ka first i classified all available geological estimates as members of three group

using stress deflections to identify slip events in fault systems abstract a new approach for identifying past slip events in strike slip fault systems without geological markers is presented a 2 d distinct element modeling code is used to simulate the stress distribution around a strike slip fault zone after a major slip event mature and immature fault zones are investigated slip on the fault is responsible for stress rotations near the active fault strand series of experiments reveal that the stress deflections are qualitatively the same whatever the fault strike fault friction and far field differential stresses for a left lateral fault stresses are rotated clockwise in the two compressive quadrants near the fault tips and counterclockwise in the two extensive quadrants the stress field signature of a slip event thus highlights the extent of the active fault strand conversely the reconstruction of paleostress fields through inversion of minor striated faults that commonly follow slip on the master fault and the analysis of their deflections allow recognition of the fault strands that slipped in a close or remote past application to the left lateral pontarlier fault zone in the jura fold and thrust belt france late cenozoic in age shows that the fault activity has migrated northward in agreement with the in sequence development of the mountain belt

the upper rhenish shield basement vosges upper rhinegraben and schwarzwald main structural features deduced from magnetic gravimetric and geological data abstract interpretation of magnetic and gravimetric data and correlations with geological observations on outcrops and in boreholes have enabled the construction of a geological sketch map of the pre westphalian basement in the area of the upper rhenish shield the map demonstrates the contrast between the heavy and magnetic saxothuringian characterized by palaeozoic units metamorphosed to varying degrees and intruded by early carboniferous basites and the lighter moldanubian consisting mainly of gneisses and granites geological structures and tectonic features are recorded beneath the mesozoic and cenozoic cover the present picture of the basement is mainly the result of late visean early namurian structural features represented by a linear arrangement of magmatic bodies and the distribution of strike slip and thrust faults the major structural features are the e w vittel lalaye lubine baden baden fault that marks the border between saxothuringian and moldanubian the n35 left lateral wrench fault system running along the present rhinegraben the n60 grain of the northern vosges and the saar basin and the s verging crustal thrusts of moldanubian

bedding parallel stylolites as a tool to unravel maximum burial depth in sedimentary basins application to middle jurassic carbonate reservoirs in the paris basin france in recent years stylolites which are rough dissolution surfaces commonly found in carbonates have been used for paleopiezometry estimates the stylolite roughness inversion technique srit applied on sedimentary bedding parallel stylolites bps grants access to the maximum principal vertical stress experienced by the host carbonates and thus to their maximum burial paleo depth this study reports the results of srit applied to a bps population hosted in carbonate platform reservoirs of the paris basin sub surface france middle jurassic carbonates from two well cores from the depocenter and margin of the basin for which the burial and thermal history are known based on a thermally calibrated 3 d basin model were analyzed by defining a consistency criterion and using two signal treatment methods we propose a new approach to select which bps can be reliably used to reconstruct the maximum vertical stress undergone by the host carbonates which then can be converted into maximum burial depth the study of a bps population shows that there is a control operated by the host rock texture and the stylolite morphology on the burial depth recorded especially suture and sharp peak bps are better suited to estimate the real maximum depth whereas seismogram pinning bps record preferentially intermediate depths median values of maximum depth derived from our data set 1300 and 1650 m for the margin and depocenter cores respectively are in line with maximum burial estimates provided by conventional basin modeling 1450 and 1800 m respectively thus showing that srit is a standalone robust depth gauge in sedimentary basins provided sample selection and data treatment are carried out in a rigorous and thoughtful manner

eocene oligocene tectonics and kinematics of the rhine saone continental transform zone eastern france a tectonic analysis of brittle deformaton was performed in the rhine saone transform in order to decipher and understand the deformation processes in a typical continental hansfer zone cenozoic major and minor fault patterns are described and brittle structures are interpreted in terms of paleostress orientations the eocene n s compression related to africa eurasia convergence is marked mainly by strike slip faults it was followed by a major phase of crustal extension mainly oligocene in age related to the west european rifting this extensional phase is expressed by normal faults tension gashes and extensional strike slip faults which are especially abundant in the transform zone these two events are found to be quite different in terms of distribution of horizontal shess trajectories the trend of ol axes is very homogeneous for the n s compression whereas o3 orientations associated with the major extension vary from e w in most of the rift system to i v se within the transform zone finally the mio pliocene tectonic emplacement of the jura fold and thrust belt is marked in the field by strike slip faults associated with a well defined trend of ol oriented w iiw e se to nw se the preexisting basement fracture pattern between the grabens was also considered in order to estimate which faults were likely to have been reactivated during the oligocene transform kinematics and the theoretical shear motion on these inherited fault surfaces when submitted to e w extension was calculated left laterauextensional reactivation of a preexisting 60 n trending fault system in the brittle upper crust is likely to have accommodated the shear strain arising between the rift segments in response to crustal stretching two independent numerical modelings based on distinct element and finite element analyses respectively enabled us to verify and to refine the hypothesis of transform kinematics related to e w extension and inducing regional perturbations of extensional stress trajectories the overall mechanism and the transtensional kinematics of the rhine saone transform zone are thus tightly conshained the inherited crustal anisotropy the large scale perturbations of extensional stress trajectories and the development of distributed brittle deformation within the sedimentary cover are found to play a major role in the tectonic evolution of continental rift transform systems

successive post variscan stress fields in the french massif central and its borders western european plate comparison with geodynamic data abstract structural analysis and particularly microtectonic methods have made it possible to define the different stages of brittle deformation of the massif central basement and the surrounding sedimentary cover from the end of the hercynian orogeny to the end of the tertiary during the stephanian a compressional tectonic regime prevailed regional faults appeared or were react vated reactivation as a result of initial n s compression becoming nw then e w these regional strike slip faults caused local extension which led to the formation of small coal bearing basins this compressional regime which marked the end of the formation of pangea was followed by a series of extension episodes permian triassic extension oscillating around n s e w to nw se extension in the early and middle jurassic and finally n s to ne sw extension in the late jurassic to cretaceous the normal faults formed during these episodes strongly influenced the distribution of emerging continents and sedimentary basins from the campanian 75 ma to the present the convergence of africa and eurasia involved the distribut on of stresses in the west european plate several tectonic episodes are distinguished in the massif central during the eocene approximately n s compression predominated general e w extension in the late eocene oligocene resulted in grabens with general northerly strike mainly in the centre of the massif central and on its east and southeast borders lastly compression varying from nw se to e w in the north and south of the massif central prevailed during the alpine orogenic phase at the end of the miocene these successive stages of brittle deformation are interpreted in the context of the evolution of the west european plate and its displacement in relation to the african plate the correspondences between the major geodynamic periods and the distribution of stresses over the west european continent are noted as well as the problems which remair to be resolved

graben width controlling syn rift sedimentation the palaeogene southern upper rhine graben as an example eocene to early oligocene syn rift deposits of the southern upper rhine graben urg accumulated in restricted environments sedimentation was controlled by local clastic supply from the graben flanks as well as by strong intra basinal variations in accommodation space due to differential tectonic subsidence that in turn led to pronounced lateral variations in depositional environment three large scale cycles of intensified evaporite sedimentation were interrupted by temporary changes towards brackish or freshwater conditions they form three major base level cycles that can be traced throughout the basin each of them representing a stratigraphic sub unit a relatively constant amount of horizontal extension l in the range of 4 5 km has been estimated for the urg from numerous cross sections the width of the rift lf however varies between 35 and more than 60 km resulting in a variable crustal stretching factor between the bounding masterfaults apart from block tilting tectonic subsidence was therefore largely controlled by changes in the initial rift width l0 the along strike variations of the graben width are responsible for the development of a deep trough like evaporite basin potash basin in the narrowest part of the southern urg adjacent to shallow areas in the wider parts of the rift such as the colmar swell in the north and the rhine bresse transfer zone that delimits the urg to the south under a constant amount of extension the along strike variation in rift width is the principal factor controlling depo centre development in extensional basins

evolution and structure of the upper rhine graben insights from three dimensional thermomechanical modelling the evolution and geometry of the tertiary upper rhine graben were controlled by a continually changing stress field and the reactivation of pre existing crustal discontinuities a period of wnw ese extension in the late eocene and oligocene was followed by lateral translation from the early miocene onwards this study utilizes 3d finite element techniques to simulate extension and lateral translation on a lithospheric scale brittle and creep behaviour of lithospheric rocks are represented by elastoplasticity and thermally activated power law viscoplasticity respectively contact elements allocated with cohesion and frictional coefficients are used to describe pre existing zones of weakness in the elastic brittle field our results suggest that 1 extension is accommodated along listric border faults to midcrustal depth of 15 16 km beneath pure shear stretching occurs without a need for localized shear zones in lower crust and upper mantle 2 ductile flow at midcrustal depth across the graben accounts for the pronounced halfgraben morphology thereby the shape of the border faults their frictional coefficients and sedimentary loads have profound effects on the rate of ductile flow across the graben 3 horizontal extension of 8 8 5 km and sinistral displacement across the rift of 3 4 km are needed to accommodate the observed sediment thickness

upper rhine graben role of preexisting structures during rift evolution 1 the evolution of the cenozoic upper rhine graben was controlled by a repeatedly changing stress field and the reactivation of a complex set of crustal discontinuities that had come into evidence during permo carboniferous times a comparison of the spatial and temporal thickness distribution of synrift deposits with preexisting fault patterns permits to infer a sequence of distinct basin subsidence phases that can be related to changes in the ambient stress field reactivation of a system of late palaeozoic fault systems outlining troughs and highs controlled the nucleation of initially separated middle and late eocene basins the depocenters of which coincided with a preexisting wsw ene trend during oligocene crustal extension the individual basins coalesced resulting in the development of the ssw nne striking upper rhine graben during the late oligocene chattian change in stress field the upper rhine graben was probably reactivated as a dextral strike slip system with the central graben segment forming a releasing bend during the early miocene aquitanian a major reorientation of the regional stress field is held responsible for the main subsidence phase of the northern parts of the upper rhine graben this is reflected by a counterclockwise rotation and northeastward shift of the depocenter axis and later by the middle miocene uplift and erosion of the southern parts of the upper rhine graben during the plio quaternary the upper rhine graben was reactivated as a sinistral strike slip system with the central graben segment forming a restraining bend

characterization of stress perturbations near major fault zones insights from 2 d distinct element numerical modelling and field studies jura mountains abstract we consider and discuss the presence of discontinuities in the crust as a major source of stress perturbations based on 2 d distinct element modelling we reconstruct the local stress field around a vertical discontinuity in various geological contexts the resulting stress distribution reveals that major directional stress changes occur near the tips of the discontinuity so that stress deviations can reach values as large as 50 we establish simple relationships controlling stress changes around a pre existing fault zone as a function of 1 the remote differential stress magnitude 1 3 2 the friction coefficient on the discontinuity and 3 the strike of the discontinuity relative to the far field stress as a geological example we present the morez fault zone in the internal jura paleostress reconstruction in forty two sites indicates that the trends of the mio pliocene compression are n110 on average near the fault whereas they are n130 in the surrounding areas a comparison between the results of the tectonic study and those of theoretical modelling suggests that the 20 counterclockwise deviation is directly related to the reactivation of this large weak zone we thus evaluate the role of mechanical decoupling along pre existing zones of weakness especially with consideration to the accommodation of the alpine deformation in the jura belt

internal structure and deformation of an accommodation zone in the northern part of the suez rift abstract detailed structural study of the eastern onshore part of the gharandal accommodation zone that separates the northern sw dipping and central ne dipping half grabens of the suez rift helped decipher the internal structure and deformation of accommodation zones of continental rifts this 60 km wide zone is affected by pure normal faulting the ne dipping faults of the northern half graben extend southward into the accommodation zone where they interfinger with sw dipping faults extending from the central half graben these two sets of rift parallel faults form several horsts and grabens in the accommodation zone areas dipping parallel to the northern or southern half grabens form several intermixing dip domains in the accommodation zone smaller scale accommodation of dip between these dip domains proceeds by the development of rift parallel folds twist zones in contrast to the southern accommodation zone of the suez rift the internal structure of the gharandal accommodation zone is believed to be representative of accommodation zones in regions a unaffected by prerift structures lying at high angles to the rift and b experiencing relatively small extension accommodation zones in areas having pre rift structures lying at high angle to the rift have relatively narrow width and are characterized by transverse strike slip faults strike slip movement on these faults is related to the torsional strain resulting from the opposite tilt directions and transport of fault blocks of adjacent half grabens

depth dependency of stress ratios during the sedimentation of nw gyeongsang basin cretaceous southeast korea estimate of stress parameters and timing of tectonic episodes abstract the natural stress state in the lithosphere consists of the vertical load and poisson ratio and then additional horizontal compression and extension denoted by h and t respectively are assumed to be superimposed upon this gravitational stress field the resulting stress state is composed of the maximum medium and minimum stresses denoted by 1 2 and 3 respectively the stress ratio is given as 2 3 1 3 a linear relation is found between or 1 and the vertical load in wrench faulting and extensional stress regimes respectively the slope and intercept of the linear relation result in the additional horizontal stresses and level of average paleo surface respectively stress ratio is also determinable by the stress tensor inversion of fault slip data the earliest tectonic event t 1 event in the cretaceous gyeongsang basin consists of coexisting e w compression and n s extensional faulting episodes plots of or 1 against the burial depth or vertical load display several linear trends two clusters in extensional episodes and two or three clusters in wrench faulting episodes because h is assumed to be null or negligible in the extensional regime t is determinable from the slopes of two linear clusters as being 2 5 to 4 0 mpa in wrench faulting episodes the values of h are given to be 61 6 101 4 mpa by applying determined additional horizontal extensions determined levels of average paleo surfaces and those of syndepostional structures illustrate that more than five wrench faulting or extensional episodes have occurred during the t 1 event whose active age consequently ranges from the barremian to the coniacian this supports that the coexisting coaxial faulting episodes with the same extension may correspond to the alternation of wrench faulting and extensional episodes

european cenozoic rift system abstract the european cenozoic rift system extends from the coast of the north sea to the mediterranean over a distance of some 1100 km it finds its southern prolongation in the valencia trough and a plio pleistocene volcanic chain crossing the atlas ranges development of this mega rift was paralleled by orogenic activity in the alps and pyrenees major rift domes accompanied by subsidence reversal of their axial grabens developed 20 40 ma after beginning of rifting uplift of the rhenish shield is related to progressive thermal lithospheric thinning the vosges black forest and the massif central domes are probably underlain by asthenoliths emplaced at the crust mantle boundary evolution of this rift system is thought to be governed by the interaction of the eurasian and african plates and by early phases of a plate boundary reorganization that may lead to the break up of the present continent assembly

the cenozoic graben system of sardinia italy geodynamic evolution from new seismic and field data abstract a tectono sedimentary scenario for the southern sardinia italy cenozoic graben system is proposed using field observations and the interpretation of onshore and offshore seismic profiles the major structural events are tied to the general geodynamic evolution of the western central mediterranean thus the extensional late oligocene aquitanian event is a consequence of an apenninic westward subduction process associated with a volcanic arc 29 30 to 15 16 my which is particularly well exposed in sardinia deposition of sub aerial clastics was followed by transgression of the rift depression at the beginning of the aquitanian subduction terminated at the opening of the oceanic provencal basin and the rotation of sardinia corsica during burdigalian time 20 21 to 15 16 my the messinian compressional event ne sw oriented documented from microtectonic data strongly affected the oligo miocene basin the superimposed plio quaternary campidano graben which is probably related to the formation of the tyrrhenian basin contains more than 600 m of syntectonic deposits a change in polarity of the master faults bounding the oligo miocene rift created a central horst type twist zone separating two depocenters in the oristano and cagliari regions emplacement of large volcanic bodies and inversion of the basin during the messinian in cagliari area has reduced the areas with potential for hydrocarbon exploration the two remaining prospective zones are the oristano sub basin and the offshore south of cagliari where burial of lower miocene marine organic matter may have been sufficient to generate hydrocarbons potential reservoirs could be pre rift mesozoic or eocene strata but are mainly excellent miocene sands derived from erosion of the granitic basement in tilted blocks

architecture and kinematics of the constance frick trough northern switzerland implications for the formation of post variscan basins in the foreland of the alps and scenarios of their neogene reactivation post variscan basins are commonly inferred to represent important precursor structures of later extensional and contractional tectonic events in the foreland of the european alps nevertheless their structural characteristics are typically poorly constrained our investigation sheds new light on the architecture and kinematics of the constance frick trough cft in northern switzerland according to our analysis of an extensive and revised 2 d reflection seismic data set the ene wsw striking cft is divided into an eastern segment and a western segment characterized by opposing half graben geometries the transition between the two segments coincides with the prolongation of a preexisting wnw ese trending strike slip fault zone exposed in the adjacent black forest massif to the north field based analysis of outcrop scale faults in the latter area implies that the minimum horizontal stress during the formation of the cft was roughly oriented ne sw which is oblique to the trough axis while previously published analogue models imply that some characteristics of the cft could be explained by lateral linkage of graben segments under oblique extension the pronounced half graben geometry of the cft suggests that low angle normal faulting may also have contributed to trough formation the observed structural complexities of the cft and uncertainties regarding its deep structure must be taken into account for interpretations of similar late paleozoic basins inferred in the subsurface of the northern alpine foreland basin in particular concerning scenarios of their neogene reactivation during alpine orogeny

final stages of the variscan orogeny at the southern iberian massif lateral extrusion and rotation of continental blocks 1 the southern part of the iberian massif contains one of the sutures of the european variscan belt several systems of faults and dikes appear as a result of a period of brittle deformation during the late stages of the variscan tectonic evolution of this zone a detailed analysis of these structures has been carried out in this work four successive deformation phases have been identified a first strike slip normal faulting stage a transcurrent stage a second strike slip normal faulting stage and finally a thrusting stage the age of these phases vary between around 310 ma and less than 270 ma the computed trajectories of the deformation axes show a progressive anticlockwise rotation of around 90 these data together with the results of previous geological and geophysical studies of this zone and of the variscan belt as a whole lead us to propose a model of tectonic evolution for the last stages of the variscan collision comparison with modern examples of collisional belts and with the results of analog experiments suggests that a promontory of the continental lithosphere of the downgoing plate indented against the active continental margin of the upper plate the indenter suffered an intense deformation in accordance with the predictions of some recent analog models simulating the indentation of a four layer continental lithosphere the variscan and late variscan brittle deformation episodes represent the waning stages of the variscan collision and not an independent tectonic event

simultaneous normal faulting and extensional flexuring during rifting an example from the southernmost upper rhine graben the southern end of the upper rhine graben urg is formed by a major continental transfer zone which was localised by the reactivation of ene oriented basement faults of late palaeozoic origin a combination of subcrop data derived from exploration wells and reflection seismic lines and palaeostress analysis provided new constraints on the timing and kinematics of interacting basement faults rifting in the southern urg began in the upper priabonian under regional wnw ese directed extension oriented roughly perpendicular to the graben axis in the study area this led to the formation of nne trending half grabens simultaneously ene trending basement faults situated in the area of the future rhine bresse transfer zone rbtz were reactivated in a sinistrally transtensive mode in the sedimentary cover the strike slip component was accommodated by the development of en echelon aligned extensional flexures flexuring and interference between the differently oriented basement faults imposed additional but locally confined extension in the sedimentary cover which deviated by as much as 90 from the regional wnw ese extension the interference of regional and local stresses led to a regime approaching radial extension at the intersection between the urg and rbtz

crustal scale thrusting and extension in the hercynian schwarzwald and vosges central europe the hercynian outcrop areas in the schwarzwald of sw germany and vosges of easternmost france consist from north to south of three major lithotectonic complexes very low to medium grade metamorphics of the saxothuringian belt the polymetamorphic central gneiss complex and the tectonic melange of the southern complex juxtaposition of these three complexes occurred by oblique convergent motions in early carboniferous time the saxothuringian belt is part of a major se dipping accretionary wedge that consists of lower paleozoic meta sedimentary and metaigneous rocks and superimposed upper devonian to lower carboniferous synorogenic volcanics and elastics the central gneiss complex consists of polymetamorphic paragneisses orthogneisses metabasites and meta ultramafics dipping to the nw the southern complex consists of an imbricated melange of north to nw dipping synorogenic elastics volcanics and blocks of ultramafics and gneissic basement the central gneiss complex cgc experienced pervasive hercynian low pressure high temperature metamorphisrn before it was emplaced against and thrust over the sedimentary and volcanic fill of the adjacent synorogenic basins this convergence 340 330 ma produced mylonitic cataclastic shear zones in the cgc the most significant shear zones are the se verging todtnau fault zone between the cgc and the southern complex and the nw verging lubine fault zone between the central gneiss complex and the rocks of the saxothuringian belt these two fault zones enclose a bivergent pop up of the polymetamorphic basement the todtnau fault zone probably extends for more than 100 km along strike and can be traced to a depth of 10 km by deep seismic reflection studies detachment probably occurred along a mid crustal zone of anatexis expressed by a domain of low seismic reflectivity between about 10 and 15 km crustal thickening during early carboniferous convergence led to an extensional phase of crustal reordering between about 330 and 280 ma that was accompanied by the massive rise of posttectonic granitic plutons from middle to high crustal levels simultaneous creation of a structural lamination in the refractory lower crust neglected the main convergent tectonic boundaries it produced a basin and range type lower crust and mantle crust transition in early permian time and involved a major advective input of heat

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

how much does slip on a reactivated fault plane constrain the stress tensor given a fault plane and its slip vector the stress tensor which caused the displacement is sought two constraints are considered first a geometrical constraint that the shear stress applied to the fault plane is parallel to the slip wallace 1951 bott 1959 second a frictional constraint that the shear to normal stress ratio equals tan 0 coulomb 1776 in a first step the stress tensors that satisfy the geometrical constraint are sought for tensors belonging to the vectorial space of solutions shear and normal stress magnitudes become a function of the orientation of the principal stresses and are mapped extending a study by mckenzie 1969 in a second step it is investigated which of these tensors also satisfy the frictional constraint within this more restricted vectorial space there is a relationship between the magnitudes 1 2 1 3 and s 1 3 1 and the orientations of the principal stresses both the range of s and the spatial distribution of are more restricted than when the geometrical constraint alone is considered as when the geometrical constraint is solely considered mckenzie 1969 the orientations of the principal stresses may lie significantly away from and up to right angle to the p b t axes however this can happen only in two cases 1 either the effective stress difference s has reached a high value which is unlikely to happen if enough preexisting fractures are available to release the stress or 2 2 becomes close to either 1 or 3 and therefore barely distinguishable from it in that case the delocalization of the orientations of the principal stresses is best described by a tendency for to exchange role with either or when the stress difference remains small and 2 reasonably away from 1 and 3 approach positions that we define as the pf b tf axes and that are obtained from the p b t axes by a rotation of angle 0 2 around b and toward the slip vector this explains why the p b t axes gives reasonable estimates of the orientations of the principal stresses scheidegger 1964 despite objections mckenzie 1969 however whenever the fault plane can be distinguished from the auxiliary plane pf b tf should give a better estimate raleigh et al 1972 in an area where many fault planes are available and a uniform tensor is assumed the scatter in the plane orientations contains information about both the relative position of 2 represented by and the relative stress difference s the higher s or the closer to either 0 or 1 the more scatter this information could then be extracted by inverse methods because a friction law would constrain these inverse method more tightly it may show the necessity of nonuniform tensor to explain scattered fault plane

the role of precursory structures on tertiary deformation in the black forest hegau region structural inheritance of preexisting crustal discontinuities is widely accepted to have played a crucial role during the cenozoic tectonic evolution of the northern alpine foreland it is recognised as a process that can strongly influence local fault kinematics and strain patterns the case study presented herein is dedicated to the tectonic analysis of the freiburg bonndorf bodensee fault zone fbbfz located at the external margin of the northern alpine molasse basin and extending into the crystalline black forest massif the structure and kinematics of this crustal scale fault zone are investigated by means of a regional analysis of locally mapped faults kinematic analysis of outcrop scale fractures and slip vector modelling the exceptional possibility of analysing the fault zone exposed from basement to cover allowed for an evaluation of interaction between precursory structures and subsequent deformation features the results of this study show that the crystalline basement structures exposed along the fbbfz had a strong imprint on the map scale fault pattern observable in the mesozoic and tertiary sequences kinematic analysis of outcrop scale fracture systems in the latter units yields evidence for local multi directional extension and strike slip faulting during miocene to recent times while these observations may evoke the interpretation of a multistage palaeostress history along the fbbfz slip vector modelling of a very well exposed fbbfz segment suggests that the various strain records can alternatively be explained by one single regional stress tensor and be related to superordinate deep seated strike slip deformation

interactions between thin and thick skinned tectonics at the northwestern front of the jura fold and thrust belt eastern france 1 this study investigates spatial and temporal interactions of thin and thick skinned tectonics in a classical foreland setting located at the front of the jura fold and thrust belt in eastern france the working area coincides with the intracontinental rhine bresse transfer zone and represents the most external front of the deformed alpine foreland the investigation combines analyses of largely unpublished and newly available subsurface information with our own structural data including an exhaustive paleostress analysis and geomorphologic observations results are provided in the form of a new tectonic map and a series of regional cross sections through the study area the besancon zone forming the most external part of the thin skinned fold and thrust belt encroached onto the eo oligocene rhine bresse transfer fault system until early pliocene times thrust propagation was largely controlled by the late paleozoic to paleogene preexisting fault pattern that characterizes the rhine bresse transfer zone thick skinned deformation dominant throughout the avant monts zone located farther to the west was associated with compressional to transpressional reactivation of such faults overprinting and crosscutting criteria of fault slip data allow distinguishing between systematically fanning maximum horizontal stress axes that define the front of the thin skinned jura fold and thrust belt and consistently nw se directed maximum horizontal stress axes that characterize deformation of the autochthonous cover of the foreland which is affected by thick skinned tectonics tectonic and geomorphic analyses indicate that thick skinned tectonics started at a very late stage of foreland deformation post early pliocene geomorphic observations imply that deformation between mesozoic cover and basement is locally still decoupled however overprinting relationships and recent seismicity suggest that present day tectonic activity is thick skinned which probably reflects ongoing tectonic underplating in the alpine foreland

present day deformations of the jura arc inferred by gps surveying and earthquake focal mechanisms this study presents a compilation of more than 40 years of seismotectonic data including 54 computed focal mechanisms combined with 15 years of gps data coming from a dense network of 35 permanent gps stations within the jura arc and its vicinity these data are compared to previous available geomorphological geophysical and structural studies in order to discuss the 3d distribution of the deformation within the jura arc gps data show coherent schemes in terms of velocities and allowed to discriminate between two provinces ne of the belt and in its front foreland they also constrain a low but significant overall strain tensor with a nnw sse shortening of 2 16 nanostrain year associated with an ene wsw extension of 0 44 nanostrain year the seismotectonic approach is based on a data set of 2 400 events and 54 focal mechanisms inversions of the focal mechanisms both globally and in homogeneous sectors highlight a general strike slip deformation regime with sigma1 oriented nw se and sigma3 oriented ne sw we discriminate two different sectors in terms of basement cover un coupling 1 potentially decoupled deformation between the basement and the sedimentary cover in the ne part and 2 coupled deformation in the sedimentary cover and its basement in the jura foreland

climatic and tectonic controls on the development of the river ognon terrace system eastern france the river ognon in eastern france is the principal drainage of the southwestern vosges mountains its lowermost valley reach is oriented parallel to the northwestern front of the alpine collision zone and is characterized by a well developed terrace system geomorphological sedimentological and geochronological analyses were performed on this terrace system and associated deposits the results allow for reconstructing the pleistocene evolution of the river valley and for concluding on the processes that led to the formation of the terrace system the lithological characterization of the terrace deposits by means of heavy mineral analyses indicates pronounced modifications of the river s drainage area optically stimulated luminescence dating suggests that the last significant catchment modification and associated sediment accumulation correlates with the last glacial advance in the vosges mountains despite the apparently strong impact of climatic processes on the evolution of the river ognon our investigation also indicates a mild tectonic influence on presently observed terrace distribution

structural inheritance and cenozoic stress fields in the jura fold and thrust belt france abstract based on an analysis of 8000 minor fault slip data in the jura mountains france we discuss the influence of pre existing discontinuities on the development of fold and thrust belts we present palinspastic maps showing the stress fields and active faults during the cenozoic pre orogenic events in the jura belt prior to the main late miocene fold and thrust tectonics during the eocene a n s strike slip regime produced a few nne ssw sub vertical strike slip faults in the central external jura and a few e w reverse faults in the eastern jura near the future frontal thrust during the oligocene an average wnw ese extension with irregular stress trajectories resulted in normal faulting along n s to ne sw trends in the external part of the belt wnw ese trends along the future northern and northeastern frontal thrust and nw se trends in the internal jura the late miocene tectonics began with a strike slip regime with a fan shaped compressional trajectory it was followed by a stress field with similar stress direction but local 2 3 stress permutation resulted in strike slip regime domains contrasting with reverse regime domains stress deflections and permutations occurred near inherited cover and basement discontinuities major deformation zones like the jura frontal thrust onto the foreland the thrust of the internal central jura onto the external jura and the narrow deformation bands within the flat lying plateaus formed close to the inherited faults the structural style of the jura belt thus partly mimics the pre orogenic fault pattern stress deflections point to the pre orogenic faults express the indentation process of the jura by its hinterland and highlight successive slip events along major faults during the fold and thrust tectonics this case study illustrates the relevance of minor fault slip studies for characterizing both the pre orogenic tectonics and the kinematics of the deformation

sources of recent tectonic stress in the pannonian region inferences from finite element modelling summary we present the results of finite element modelling of the recent stress field in the pannonian basin and surrounding alpine orogenic belt our results show that the recent predominantly compressive stress regime in the alpine pannonian carpathian dinaric system is governed by distinct tectonic factors of great importance is the deformation of crustal blocks with diverent geometries and rigidities in an overall convergent setting associated with the africa europe collision the most important stress source appears to be the counterclockwise rotation of the adriatic microplate at the southwest boundary of the pannonian basin this plate tectonic unit has been interpreted as moving independently of both the european plate and the african plate additional boundary conditions active shortening and compression in the vrancea zone and the bohemian massif and the evect of the immobile moesian platform also significantly influence the modelling results the incorporation of additional stress sources such as crustal thickness variation and the presence of two main fault zones separating the primary tectonic units in the study area have only locally important evects but improve the fit between the calculated results and the observed stress pattern

joint analyses of calcite twins and fault slips as a key for deciphering polyphase tectonics burgundy as a case study abstract determination of regional paleostresses based on calcite twin analysis has been successfully applied for the first time in the burgundy platform france paleostress tensors obtained with this method are internally consistent along the profile studied moreover the same directions of paleostresses are independently inferred from fault striation analysis the results clearly show that the late mesozoic cenozoic evolution of the area has involved polyphase deformation including 1 1 nne ssw extension probably late mesozoic in age 2 2 n s compression related to a major orogenic event in the pyrenees and provence late eocene in age 3 3 e w extension related to the oligocene rifting event the rhine saone rift system 4 4 wnw ese compression related to the late miocene westward thrusting of jura calcite twin and striated fault analyses are two complementary tools for paleostress determination their combined application will allow accurate mapping of paleostress trajectories in intraplate tectonics setting moreover calcite twins can allow stress and paleostress determination when macroscopic features are not observable which is often the case in very weakly deformed areas and in drill holes

microseismic imaging of a geothermal reservoir stimulation exploitation of geothermal heat energy from rocks at depths of several km has been the goal of vari ous projects since the mid 1970s to exploit the energy in these deep rocks poses technical challenges in drilling well completion creation of the heat exchange reservoir at depth and control of seismicity in spite of the difficulties what are now known as enhanced engineered geothermal systems egs offer almost limitless clean energy so it is not surprising that this technology continues to attract investors however commercial energy production from the greatest potential resource hot rock at depths 5 km or temperatures 200 c remains elusive

tectonic stresses in the lithosphere various types of observables earthquake focal mechanisms in situ measurements and geological deformations give information about the large scale lithospheric stress field the latter has often been explained by postulating appropriate forces acting at the edges and beneath the plates this approach ignores the role of mass heterogeneities within the lithosphere here we analyze the effect of both boundary and internal forces on the stress pattern and show that both contributions are of comparable magnitude the presence of internal sources makes the problem three dimensional we show however that it can be reduced to a two dimensional plane stress formulation whereby the edge forces are expressed by the non hydrostatic stresses and the basal shear is increased by the addition of a term proportional to the gradient of the mean vertical stress for the oceanic lithosphere we derive a compression that increases with age the comparison with geophysical observables yields an upper bound of a few bars on the magniude of the basal drag for the continents we infer the existence of an underlying upper mantle somewhat denser than under oceans