pre alpine variscan inheritance a key for the location of the future valaisan basin western alps the boundary between the helvetic and the penninic brianconnais zones has long been recognized as a major fault penninic front in the western alps a narrow oceanic domain has been postulated at least along part of this boundary the valaisan ocean however the information provided by the pre triassic basement has not been fully exploited and will be discussed here in detail the igneous and metamorphic history of the pre triassic basement shows significant differences between the external massifs from the helvetic zone with abundant late carboniferous granites and the basement of the brianconnais zone including the internal massifs dora maira gran paradiso monte rosa devoid of carboniferous granites a major coal bearing basin the zone houillere opened along this boundary this limnic intramontane basin has never been properly investigated the zone houillere is not comparable with the external paralic flexural basins on both sides of the variscan belt but shows similarities with the saar saale basin like the latter we interpret the zone houillere as a transtensional basin opened along a major crustal scale fault zone namely the east variscan shear zone the permian magmatism and sedimentation displays contrasting distributions being absent or very localized in the helvetic zone and widespread in the penninic zone the above data indicate that the structural inheritance from the variscan belt plays a major role in defining the future location of the valaisan basin i e the boundary between the european palaeomargin and the brianconnais microcontinent

evolution of the lithosphere in the area of the rhine rift system the rhine rift system rrs forms part of the european cenozoic rift system ecris and transects the variscan orogen permo carboniferous troughs and late permian to mesozoic thermal sag basins crustal and lithospheric thicknesses range in the rrs area between 24 36 km and 50 120 km respectively we discuss processes controlling the transformation of the orogenically destabilised variscan lithosphere into an end mesozoic stabilised cratonic lithosphere as well as its renewed destabilisation during the cenozoic development of ecris by end westphalian times the major sutures of the variscan orogen were associated with 45 60 km deep crustal roots during the stephanian early permian regional exhumation of the variscides was controlled by their wrench deformation detachment of subducted lithospheric slabs asthenospheric upwelling and thermal thinning of the mantle lithosphere by late early permian times when asthenospheric temperatures returned to ambient levels lithospheric thicknesses ranged between 40 km and 80 km whilst the thickness of the crust was reduced to 28 35 km in response to its regional erosional and local tectonic unroofing and the interaction of mantle derived melts with its basal parts re equilibration of the lithosphere asthenosphere system governed the subsidence of late permian mesozoic thermal sag basins that covered much of the rrs area by end cretaceous times lithospheric thicknesses had increased to 100 120 km paleocene mantle plumes caused renewed thermal weakening of the lithosphere starting in the late eocene ecris evolved in the pyrenean and alpine foreland by passive rifting under a collision related north directed compressional stress field following end oligocene consolidation of the pyrenees west and northwest directed stresses originating in the alps controlled further development of ecris the rrs remained active until the present whilst the southern branch of ecris aborted in the early miocene extensional strain across ecris amounts to some 7 km plume related thermal thinning of the lithosphere underlies uplift of the rhenish massif and massif central lithospheric folding controlled uplift of the vosges black forest arch

variscan tectonics of central europe postaccretionary intraplate deformation of weak continental lithosphere the area occupied by the variscan belt of central europe forms part of gondwana derived microplates essentially avalonia and armorica that according to paleomagnetic data juxtaposed baltica and laurentia from the upper ordovician to the lower devonian the actual structure of this area is a puzzle of rather small fault bounded crustal blocks different in p t t histories which was created by later tectonic processes at around 360 to 320 ma according to a common view and by contrast to paleomagnetic data the structural record of fault bounded blocks is interpreted in terms of mid devonian to lower carboniferous amalgamation of narrow continental plates represented by the fault bounded blocks themselves however this is not supported in this article instead it will be shown that fault systems and fault bounded blocks were created by intraplate deformation of a weak domain of gondwana derived continental lithosphere significantly after its accretion deformation was partitioned into newly formed deep seated strike slip and kinematically connected reverse or normal detachment systems large translation magnitudes caused juxtaposition of crustal areas of variable thickness until they were emplaced along the fault systems the various categories of fault bounded complexes record different tectonic events category 1 metamorphic complexes represent deep seated parts of thickened crust some time before unroofing on the detachment systems between about 340 360 and 320 ma however the record of subduction and extreme crustal thickening during earlier stages of the collision history was erased to a high degree and is only preserved by mineral and structural relics strike slip and detachment systems propagated across and dismembered tectonic boundaries formed during these early events category 2 metamorphic complexes and the barrandian basin recording predominant pre late devonian metamorphic or stratigraphic events represent the brittle upper crustal parts during continuing metamorphism in the category 1 complexes weakly or unmetamorphosed lower paleozoic category 3 basins represent areas of thinned continental crust and record subsidence before and to some degree during activity of detachment systems the complex overall kinematic pattern of block bounding strike slip and detachment systems indicates compression and extension acting simultaneously this probably reflects the effects of continuing oblique plate convergence rotation and wsw extrusion of fault bounded blocks in addition to heating and extensional flow of previously thickened crustal areas

plate and intraplate processes of hercynian europe during the late paleozoic abstract it is speculated that until late carboniferous time the region of hercynian europe was occupied by an elongated island arc system underlain by a segment of continental crust in the upper carboniferous two subduction zones are assumed to have extended from the north and south beneath hercynian europe an extensive zone of hot partially molten upper mantle lay above and between these and diapiric uprise of portions of this material led to separation of mafic magmas widespread partial melting in the lower and middle crust high temperature low pressure metamorphism in crustal rocks and regional uplift and extension of the crust as indicated by intermontane troughs and their associated volcanic rocks in visean to westphalian time hercynian europe collided with both the large neighbouring plates north america europe and africa during these diachronous collisions and owing to reduced rigidity of the relatively hot island arc crust the irregular continental margins of the larger and thicker continental plates induced oroclinal bending of hercynian europe after the collision processes had been terminated processes of upper mantle activity continued causing further crustal uplift and even enhanced crustal extension for several tens of million years into the lower permian decline of the upper mantle activity beneath hercynian europe is indicated by crustal subsidence and formation of a peneplain in permian time followed by the upper permian transgression of both the zechstein sea and the tethys sea which mark the end of the hercynian geodynamic cycle

the carbonates of the post variscan basins of sardinia the evolution from carboniferous permian humid persistent to permian arid ephemeral lakes in a morphotectonic frameworkcarbonates of the post variscan basins of sardinialg costamagna late to post variscan sedimentary basins of sardinia were influenced during pennsylvanian to permian times by two main tectono sedimentary cycles a pennsylvanian to cisuralian cycle represented mainly by dark limnic deposits overlain by a guadalupian to a possibly lopingian cycle mostly characterized by red bed deposits lacustrine waterbodies developed in some sedimentary basins that were filled with siliciclastic to frequently early silicified carbonate deposits depending on the climate and environmental conditions landscape morphology and tectonic regime the limnic successions of the lower tectono sedimentary cycle were deposited in permanent tens of metres deep lakes in deep narrow tectonic strike slip basins under a temperate to warm humid climate they started as lakes with terrigenous sedimentary input and developed minor carbonate deposits mainly at the end of their story conversely the red bed successions of the upper cycle were deposited in ephemeral shallow playa lakes related to wider basins in an extensive alluvial plain under a hot and arid climate here the siliciclastic sediments are intercalated with thin carbonate beds that are typical of a high evaporation rate the evolution of the lake type could be related not only to a major climatic shift but also to the changing morphotectonic conditions of the variscan chain influencing the local microclimate comparisons with coeval successions in the provence basin the massif central aumance basin france and the saar nahe basin germany show both similarities and differences between the basins

a deep reflection seismic line across the northern rhine graben abstract two reflection seismic lines across the tertiary rhine graben in central europe were recorded in 1988 as a joint venture of the french ecors and the german dekorp deep seismic reflection programs in this paper the line across the northern graben is presented the main results are the asymmetry of the graben as documented by the sedimentary fill is accompanied by asymmetric features throughout the entire deep crystalline crust a thin 3 7 s twt reflective lower crust in the east a thick 5 5 s twt relatively transparent lower crust in the west total crustal thicknesses of 8 7 s twt in the east vs 10 5 s twt in the west provided a laterally homogeneous crust existed prior to rifting significant differences in upper and lower crustal thinning must be postulated extension occurred along localized shear zones that are located in the upper crust and at the crust mantle boundary the entire lower crustal layer acts as a decoupling zone

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

development of the palaeogeography of pangaea from late carboniferous to early permian abstract old and new well and poorly known lithofacies data of moscovian and artinskian age in the area limited by the arctic sea and central africa the atlantic ocean and the ural mountains have been plotted on present day maps the facies mapped and related environments allow the recognition of a series of different palaeogeographic palaeotectonic units including the late carboniferous to early permian deep sea to palaeo tethyan ocean west siberia kazakhstan continent and uralian kazakhstan tienshan arc uralian foredeep up to the closing arms of the uralian ocean precaspian basin russian platform donets rift basin caucasian moesian dobrogean polish oslo basinal belt syn tectonic hercynian foreland basin intramontane post hercynian basins iran anatolian hellenic dinaric carnic basin branching into the hungarian seaway apennine basin branching into the cantabrian and south portuguese basins oman iraq levantine sicily deep basin and inferred oceanic sea way south peri tethyan platform basins east arabian cratonic basin and north african intracratonic basins the subsidence sedimentation trends of these units were correlated and compared through lithostratigraphic logs bathymetric curves and uncorrected cumulative stratigraphic curves the sets of original and processed data were used to test two different palaeodynamic models a pangaea a model static from late carboniferous to triassic and a mobile pangaea b model with different dextral displacements between laurussia and gondwanaland in the same time interval the best fit for our data requires a strike slip offset of about 800 km from moscovian to artinskian time this model implies a first quasi pangaea or pangaea b assembly at the carboniferous permian transition an ephemeral pangaea b break up driven by an early permian oblique rift across the mediterranean to caribbean areas and a final pangaea a assembly in the mid to late permian the two palinspastic maps describing the model have been cross checked by comparison with an independent set of biogeographic features of late carboniferous and early permian overall floral reptile and marine benthic organism distribution is consistent with the early permian trans pangaea seaway inferred from facies and palaeodynamic analyses

coalification pattern and thermal modelling of the permo carboniferous saar basin sw germany abstract palaeo heat flow values and thicknesses of eroded permo carboniferous sediments in the saar basin were evaluated using one dimensional thermal modelling techniques thermal burial and erosion histories for 16 wells were calibrated by comparing measured and calculated vitrinite reflectance using the kinetic easy r o algorithm and by comparing measured and calculated temperature data on the basis of 37 wells coalification maps were constructed revealing a syn kinematic coalification pattern thermal maturity of the sediments can only be explained by deep burial and moderate heat flows during time of maximum burial i e in the permo carboniferous calculated heat flow data range between 50 and 75 mw m 2 which implies a crustal thickness between 30 and 40 km during the time of maximum burial these values are in accordance with the geodynamic setting of the basin the influence of the permo carboniferous volcanism on the palaeo temperature distribution was overwhelmed by the subsequent deep burial during permian times between 1800 and 3000 m of permo carboniferous sediments were eroded different sedimentation and erosion histories are characteristic for anticlines and synclines respectively

strike slip orogens an explanation for the hercynides the nature of oblique plate interactions is not yet well understood the oblique interaction of pacific and n american plates has resulted in large scale migration rotation and accretion of microplates intervening basins are ephemeral individually filled and deformed oblique motion results in zones of both compression and extension the latter may be sufficient to generate new oceanic crust and the former to obduct it both subduction and collision are restricted in time and space the resulting orogen is extraordinarily complex in detail the far more complicated hercynides are the result of dextral interaction between continental plates europe and africa the lateral variability of the orogen the major and long lived strike slip faults the bimodal volcanism and related ore deposits of the european trough the lizard ophiolite and its melanges the nw spanish ophiolites and the iberian pyrite belt are all explained using an oblique collision model in particular the generation deformation and obduction of ophiolites in oblique slip mobile zones is discussed

subsidence of the paris basin we discuss the main results of a systematic quantitative analysis of the subsidence of the paris basin made on 100 wells backstripping techniques with decompaction as well as sea level and water depth corrections are used to derive tectonic subsidence curves in the absence of water and sediment loading assuming local as well as regional compensation a best fitting sea level variations curve is derived for the deepest central part on the basis of the resulting tectonic subsidence curve the adopted amplitude of the regression since upper cretaceous is 330 m the spatial and temporal distribution of tectonic subsidence is reconstructed and discussed it is shown that rigidity of the lithosphere with an adopted 50 km flexural parameter plays a significant role these results are then quantitatively interpreted in terms of the lithospheric stretching model this interpretation is reasonable provided it is made in terms of volumetric subsidence over the whole basin because of the thermal conduction and the rigidity low pass filtering effects the subsidence can be explained if the axial zone was thinned during permo triassic by a factor of about 1 3 with respect to the adjacent lithosphere it is shown that either the initial altitude was more than 500 m above sea level or the lower part of the lithosphere was lost at the beginning of the permo triassic phase of extension resulting in a rapid uplift of several hundreds of meters the similarity of the permo triassic initiating extensional phase with active continental rifting is shown

geological interpretation of dekorp deep seismic reflection profiles 1c and 9n across the variscan saar nahe basin southwest germany abstract deep seismic reflection results across the variscan saar nahe basin in southwest germany recorded as parts of dekorp lines 1c and 9n provide excellent images of the geometry of the basin and also of the structures in the underlying basement this basement consists of several discrete units some of which are highly reflective whereas others are essentially non reflective two of these units consist of well layered dipping reflectors that are interpreted as having been telescoped by thrusting adjacent to the south hunsruck fault the sedimentary pile within the saar nahe basin is over 8 km thick but it thins dramatically towards the southeast and east the position of continuous reflectors both in the basin and the basement indicate that the south hunsruck fault is subvertical and not a listric normal fault as proposed in several earlier interpretations this implies that the basin did not form by normal extension but that it is transtensional in character its geometry predominantly being controlled by strike slip movements on the south hunsruck fault

asymmetry and basin migration in the dead sea rift the dead sea depression sensu stricto forms the deepest continental part of the dead sea rift a transfer which separates the levanthine and arabian plates it is occupied by three distinct sedimentary bodies deposited in basins whose depocenters are displaced northward with time they are the continental red beds of the hazeva formation miocene the bira lido gesher marls and the exceptionally thick rocksalt of the sedom formation pliocene early pleistocene and the successive amora lisan and dead sea evaporites and clastics early pleistocene recent lengthwise and crosswise asymmetries of these sedimentary basins and their respective depocenters are due to leftlateral shear combined with anticlockwise rotation of the arabian eastern plate steeper faulting of the crustal eastern margin than of the western sedimentary margin and modification of depositional pattern by twice filling up of basins by hazeva red beds during late miocene pause of shear and by sedom rocksalt during pliocene marine ingression

modelling of the thermal history of the carboniferous lorraine coal basin consequences for coal bed methane this paper proposes a new scenario for the thermal history of the carboniferous lorraine coal basin following the tectonic model developed by averbuch et al 2012 and establishes some consequences for the coal bed methane cbm exploitation organic matter maturation data vitrinite reflectance determined on eleven boreholes in the eastern lorraine have been used to characterize the lorraine coal basin evolution paleozoic and mesozoic overburials have been calculated using a thermal modelling software petromod results show that 1 paleozoic erosion may be estimated at a maximum of 1200 m which represents a low amplitude event 2 a little erosion occurred between upper paleozoic and lower mesozoic paleotemperature offset is about 20 c and vr data range from 0 7 westphalian d to 0 5 lower triassic 3 cretaceous cover overburial reaches a maximum of 300 m and decreases eastwards and 4 the variation of heat flows is in agreement with the compressive and extensive phases of paleozoic and the extensive phase of mesozoic consequences on the petroleum system are the following organic matter is immature in the jurassic and triassic sedimentary rocks mature oil window in the permian stephanian and westphalian c d highly mature gas window in westphalian a b c and overmature in namurian westphalian a the high methane adsorption capacity of coal and the presence of natural fractures inside coal seams demonstrated by coal tomography allow a high cbm potential in this basin the lorraine coal basin is therefore a target for coal gas

polar wander and surface convergence of europa s ice shell evidence from a survey of strike slip displacement two global issues regarding europa are addressed by a survey of strike slip faults first a common type of terrain that appears to represent convergent sites of surface removal which may help compensate for substantial widespread dilation along tectonic bands elsewhere thus helping resolve the problem of conserving global surface area is identified second evidence for polar wander may provide the first confirmation of that theoretically predicted phenomenon these results among others come from an extensive survey of strike slip faults over the portion of the surface where galileo images at 200 m pixel resolution were obtained for regional mapping purposes the images cover two broad swaths that run from the far north to the far south one in the leading hemisphere and the other in the trailing hemisphere among the faults that have been mapped are a fault 170 km long with a strike slip offset of 83 km the greatest yet identified on europa and a quasi circular strike slip fault that surrounds a 500 km wide plate which has undergone rotation as a rigid unit reconstruction of specific examples of strike slip reveals sites of lateral convergence because europa is unique in many ways these sites are not similar to compression features on other bodies which may explain why they had previously been difficult to identify the distribution of strike slip in both hemispheres when compared with predictions of the theory of tidal walking provides evidence for polar wander the crust of europa appears to have slid as a single unit relative to the spin axis such that the site on the crust that was previously at the north rotational pole has wandered probably during the last few million years to a location currently in the leading hemisphere about 30 away from the spin axis such polar wander probably also explains symmetry patterns in the distribution of chaotic terrain pits and uplift features

continental collisions and seismic signature processes active during continental collisions and orogenic collapse create distinct structures which are imaged by reflection seismic profiling examples are shown and discussed

crack azimuths on europa sequencing of the northern leading hemisphere 1 nonsynchronous rotation of europa should result in a periodic change in stress azimuths at any given location which may result in a corresponding change in crack azimuths an early study seemed to provide evidence for such variation within a crack sequence in the northern trailing hemisphere however more recent work with higher resolution imagery resulted in a more complete sequence of cracks in the region and showed that the azimuth variation with time was not systematic similar results were found in the southern leading region here we investigate whether the northern leading region contains a crack record on the basis of crosscutting relationships that is adequate to indicate nonsynchronous rotation as in the previous studies of other regions we find no clear evidence of nonsynchronous rotation within crack azimuth patterns however there are other lines of evidence in support of nonsynchronous rotation therefore the lack of a continuous pattern of azimuth change with time is likely due to only a few cracks forming per cycle thus hiding any discernable signal from nonsynchronous rotation in those regions in that case the cracks would have formed over numerous cycles of nonsynchronous rotation the study also reveals a distinctive distribution of crack azimuths with gaps at certain values this distribution may reflect a combination of observation selection due to illumination and less favorable cracking orientations

late orogenic basin evolution in the variscan internides the saar nahe basin southwest germany abstract the late variscan evolution of the saar nahe basin in southwest germany is closely controlled by the kinematics of the hunsruck boundary fault which also separates two main tectonostratigraphic units of the variscides the saar nahe basin comprises a half graben structure which formed due to extensional reactivation of a variscan thrust between the early westphalian and late rotliegend about 8 5 km of alluvial fan fluvial and lacustrine sediments accumulated during the permo carboniferous w e oriented extension was accommodated by a system of nw se trending transfer faults and orthogonal normal faults balanced cross section construction and subsidence analyses suggest a 35 extension of the previously thickened crust in the late stage of the orogeny the subsidence analyses show discontinuous depth dependent extension with laterally varying extension factors in the crust and mantle the offset between syn and post rift depocentres is explained by a mantle stretching zone shifted laterally with respect to the area of maximum crustal extension finally a geodynamic model for the evolution of the saar nahe basin with special reference to the earlier variscan development and the general evolution of permo carboniferous basins in central europe is presented

aspects of the reconstruction of the stress history of a fold and thrust belt rhenish massif federal republic of germany abstract by use of faults and striations parts of the deviatoric stress tensors and thereby essential aspects of the paleostress history of the rhenish massif can be reconstructed the stress history is unexpectedly complex even on the local scale the region under investigation is subdivided into various areas each of which exhibits somewhat different sequences of stress states several mutual aspects are evident in lower devonian rocks in the north which show only very slight deformation a pre folding stress state is preserved with a preferentially n s trending extension attributed to the stage of basin development the stage of folding itself during the carboniferous shows strong regional and temporal heterogeneity under frequently altering stress states after an initial stage of a semi homogeneous stress field this development occurs simultaneously with partial stress uncoupling at larger thrust zones with diverging deformation histories of hangingwalls and footwalls movement patterns in the north evidence subsequent clockwise rotation of the stress field which is only weakly represented in the south on the other hand there is clear evidence of a still younger counterclockwise rotation of the stress field which only affects the southern massif this is probably due to the superpositioning of orthogonal relative movements on the southern rim of the fold belt by a dextral strike slip component during final deformation thus indicating late dextral transpression succeeded by dextral transtension the final extensional stage is related to late paleozoic uplift and crustal stretching perpendicular to the strike of the fold belt followed by a change of direction of extension this state of stress obviously extends into the present although complex the various stress conditions are clearly correlated with other fabric elements in particular with cleavage fold geometry and mineralization

results of the dekorp 1 belcorp dekorp deep seismic reflection studies in the western part of the rhenish massif summary within the dekorp project dekorp deutsches kontinentales reflexionsseismisches programm a joint deep seismic reflection venture with the belcorp belgian continental reflection seismic programme group of the belgian geological survey was carried out in 1987 across the rhenish massif a part of the mid european variscides this orogenic belt developed in the upper devonian carboniferous mostly devonian rocks crop out at the surface the rhenish massif is bordered by two sedimentary troughs the sub variscan foredeep in the north and the permo carboniferous saar nahe basin in the south in the east west direction it is subdivided by the axial depression of the eifel nord sud zone the aim of the survey which totals almost 220 km of seismic profiling was to investigate the crustal structure of the western part of the rhenish massif and to compare it with the line dekorp 2 n which crosses the eastern portion of the massif the results indicate the presence of nw vergent tectonics of various styles that can often be traced down to deep parts of the crust horizontal variscan compression plays a dominant role in the northern part while post variscan extension seems to dominate in the saar nahe basin although even there traces of variscan compression seem to be preserved in the middle crust common characteristics of the pre palaeozoic basement differences between the western and eastern parts of the rhenish massif and the deep extension of the aachen thrust faille du midi have been clearly observed this prominent thrust in the north with its characteristic ramp and flat structure has been followed over 100 km length down

facies architecture variations and seismogenic structures in the carboniferous permian saar nahe basin sw germany evidence for extension related transfer fault activity abstract sedimentary and volcanic strata in the late orogenic intermontane saar nahe basin preserve a record of sedimentary responses to motion on contemporaneously active faults studies of such deposits can constrain both concepts for lateral and vertical sedimentary facies development and geometric and kinematic models of intrabasinal extension during carboniferous permian syn rift development the saar nahe basin underwent a marked intrabasinal segmentation generated by the offsets of longitudinal normal faults and dextral oblique strike slip faults which were developed perpendicular to the sw ne basin elongation the latter are interpreted as transtensional transfer faults which compartmentalized the basin into segments of differing structural style bed thickness and facies development the fault zones themselves bound an assemblage of variously sized uplifted and downthrown blocks showing variable magnitudes and senses of displacement their activities are recorded by the contrasting depositional histories of tephrostratigraphically constrained sedimentary units occupying footwall and hanging wall block positions during basin filling the influence of faults on the depositional system is seen in their effect as topographic barriers thus restricting free dispersal and mixing of sediment particular sedimentary facies such as coals and biogenic limestones are confined to the immediate vicinity of the fault zones indicating the isolation of sediment starved areas near downthrown hanging walls other fault generated depressions acted as depositional traps favouring considerable accumulations of basaltic lavas volcaniclastic mass flows and fluvial channel deposits in contrast uplifted footwalls are characterized by the formation of unconformities and pedogenic features the abundance of syn tectonic deformation structures such as sediment filled fissures intraformational breccias series of micro faults clastic dykes and other water escape features within syn rift strata and their distinct spatial linkage to fault zones implies considerable seismically triggered processes associated with faulting the combined occurrence of abrupt variations in facies architecture across faults and seismotectonic structures suggests that the basin subsidence history involved a series of events rather than gradual change

the evolution of the south hunsruck and taunus borderzone abstract the main fabric development of the south hunsruck and taunus borderzone htb occurred during late variscan homoaxial backfolding of an early variscan stack of thrust sheets in a narrow wsw ene trending zone several hundred kilometres long rotation and uplift of the southern rhenohercynian zone was accompanied by the subsidence of the southward adjacent northernmost parts of the saxothuringian zone and the development of the saar nahe basin during the latest carboniferous changing stress conditions gave rise to the development of normal faults along the htb and an extensive tholeiitic and rhyolitic volcanism contemporaneous uplift of the hunsruck is reflected by coarse elastics in the saar nahe basin subsequently the htb became covered by latest carboniferous early permian and mesozoic sediments cretaceous uplift of the rhenish shield caused their erosion the faultzone separating the rhenohercynian hunsruck and taunus from the permo carboniferous saar nahe basin is characterised by reverse and normal faults conjugate shear indicated by slickensides on steep oblique fracture planes as well as slight folding and small scale thrusting in post variscan sediments may be attributed to compressional foreland deformation reactivating variscan joint fabrics and fault systems timing of these deformations is ambiguous and could partly be related to dextral shear during the cenozoic subsidence of the rhine graben cenozoic sediments of the upper rhine graben overstep the northeastern parts of the htb seismic investigations indicate that the htb is associated with a system of southeast hading listric planes extending beneath the moho occasional dip slip earthquakes occur along these fractures

subsidenz und tektonik des saar nahe beckens sw deutschland the saar nahe basin in sw germany is one of the largest permo carboniferous basins in the internal zone of the variscides its evolution is closely related to movements along the hunsruck boundary fault which separates the rhenohercynian and the saxothuringian zones recent deep seismic surveys indicate that the saar nahe basin formed in the hanging wall of a major detachment which soles out at lower crustal levels at about 16 km depth oblique extension along an inverted variscan thrust resulted in the formation of a half graben within more than 8 km of entirely continental strata accumulated the structural style within the basin is characterized by normal faults parallel to the basin axis and orthogonal transfer fault zones balanced cross section construction and subsidence analysis indicate extension of the orogenically thickened lithosphere by 35 subsidence modeling shows discontinuous depth dependent extension with laterally varying extension factors for crust and mantle lithosphere thus the offset between maximum rift and thermal subsidence can be explained by a zone of mantle extension shifted laterally with respect to the zone of maximum crustal extension

structural stratigraphic models for extensional basins of half graben type abstract the equations describing subsidence in isostatically compensated basins formed by lithospheric stretching can be modified to define a notional depth to decollement which relates subsidence to the stretching factor in much the same way as the depth to a physical sole fault relates subsidence to extension in uncompensated thin skinned basins for a constant density basin fill this notional depth to decollement corresponds to the level of no vertical motion within the lithosphere in general the physical sole to a system of detached normal faults will not lie at the notional depth to decollement and must move vertically during extension this vertical movement must be implicitly corrected for before area bed length balancing is used to determine the depth to a physical sole fault the notional depth to decollement has been calculated numerically for an extensional basin loaded by sediments which follow a north sea shaly sand compaction law and increases with from 5 to 9 km a set of model half grabens has been constructed by combining subsidence curves generated by this shaly sand model with geometric relationships inherent in the rotated planar domino mechanism of upper crustal faulting for comparison a similar set of half grabens was constructed for an uncompensated basin with a sole fault at 7 5 km depth in both cases large fault to fault spacings give rise to large basement relief and consequent footwall uplift and erosion small fault spacings give rise to simple listric growth faults intermediate values generate more complex uplift subsidence histories which are capable of giving rise to such commonly observed features as rounded eroded fault block shoulders local regression followed by onlap or exponentially increasing subsidence at the crest of the fault block

effects of finite rifting times on the development of sedimentary basins abstract most thermo mechanical models for the development of sedimentary basins have assumed that the rifting responsible for the formation of the basin occurred instantaneously and have examined the post rift development of the basin this assumption greatly simplifies the mathematical treatment but is not in accord with what is found in nature where 10 to 50 m y rifting events commonly accompany the formation of sedimentary basins and continental margins the effects of a finite rifting time on the development of sedimentary basins are examined using an analytic technique which allows an arbitrary rifting history in both time and space and which considers the effects of both vertical and horizontal heat transfer this technique allows the thermal structure of the lithosphere to be calculated throughout the rifting event and thus permits the subsidence history and surface heat flow of the developing basin to be traced the effect of a finite duration extension event is that heat is lost during rifting increasing the syn rift subsidence at the expense of the post rift lateral heat flow which was not included in previous studies of the effect of finite rifting times has a significant effect on the subsidence history distribution of sediments and thermal history in particular the post rift subsidence is decreased by more than 25 for a 20 m y rifting event and by more than 10 15 for a rifting event as short as 10 m y this will significantly decrease the subsidence rates in the post rift stage and implies that inferences concerning the structure development and thermal history of the basin derived from using curves to interpret backstripped subsidence can be greatly in error variations in syn rift sediment accumulation and lithospheric thermal structure at the end of rifting resulting from different rifting histories can interact with other factors such as the flexural response of the lithosphere to sediment loading to affect the final width of the basin the total amount of sediments that accumulate and the basin stratigraphy

late carboniferous vegetation change in lowland and intramontane basins in germany variations in species richness alpha species diversity have been determined for westphalian and earliest stephanian moscovian middle pennsylvanian macrofloras from the paralic ruhr basin and the intramontane saarland basin in germany in the ruhr species richness progressively increases through the langsettian substage remains high in the duckmantian and lower bolsovian substages and then undergoes a marked decline in the upper part of the bolsovian substage this decline in macrofloral species richness coincides with a reduction in the number of coal seams present and a change to upper delta and alluvial plain deposits in saarland there are only a relatively few impoverished macrofloras in the lower part of the succession where high energy braided fluvial deposits prevail species richness increases significantly in the very low bolsovian substage somewhat below the stratigraphic level where the first thick coals appear species richness remains relatively high through the remainder of the westphalian stage in saarland except for a slight fall in the upper bolsovian substage most observed changes in species richness in both basins can be correlated with changes in facies resulting from shifting drainage patterns which in turn were the result of variscan tectonic activity in the surrounding hinterlands the macrofloral species richness data provide no evidence of major change in the climate in late westphalian and earliest stephanian times and the marked contraction of the coal forests taking place at this time must have been due to other perhaps tectonic factors

structural development of the central kyrenia range north cyprus in its regional setting in the eastern mediterranean region a detailed structural analysis of the mesozoic cenozoic geological development of the central segment of the kyrenia range in its regional tectonic context is given here the structural evidence comes from five structural traverses outcrop observations small scale structures and related regional evidence the majority of the structures are fault planes of which a subordinate number exhibit slickenlines fault plane data n 2688 with kinematics n 537 additional kinematic data were obtained from c s fabrics and folds small scale structures in each stratigraphic unit were backstripped to reveal relative chronology synthesis of the structural information indicates three phases of convergence related deformation 1 late cretaceous associated with greenschist facies metamorphism followed by exhumation that was probably associated with wnw ese to ene wsw trending high angle faulting 2 mid eocene associated with southward thrusting coupled with n s strike slip transfer faulting and oblique faulting in an overall sinistral transpressive stress regime 3 late miocene earliest pliocene involving southward thrusting and folding localised back thrusting extensive fault reactivation and large scale segmentation of the range intense uplift of the kyrenia range took place during the plio pleistocene possibly related to the collision of the eratosthenes seamount with the cyprus trench to the south of the island the three main convergent phases relate to stages of northward subduction and diachronous continental collision affecting the northerly active continental margin of the southern neotethys

post variscan evolution of the lithosphere in the rhine graben area constraints from subsidence modelling in the area of the cenozoic rhine rift system crustal and lithospheric thicknesses range between 24 and 35 km and 60 and 120 km respectively this rift system transects the deeply truncated variscan orogen and superimposed permo carboniferous wrench induced troughs and late permian and mesozoic thermal sag basins at the time of its westphlian consolidation the variscan orogen was probably characterized by 45 60 km deep crustal roots that were associated with its rheno hercynian saxo thuringian saxo thuringian bohemian and bohemian moldanubian sutures all of which are transected by the cenozoic rhine rift system during the stephanian early permian wrench induced disruption of the variscan orogen subducted lithospheric slabs were detached causing upwelling of hot mantle material during the resulting thermal surge partial delamination and or thermal thinning of the continental mantle lithosphere induced regional uplift at the same time the variscan orogenic roots were destroyed and crustal thicknesses reduced to 28 35 km in response to the combined effects of mantle derived melts interacting with the lower crust regional erosional unroofing of the crust and on a more local scale by its mechanical stretching towards the end of the early permian the potential temperature of the asthenosphere returned to ambient levels with this regional long term thermal subsidence of the lithosphere commenced controlling the development of a new system of late permian and mesozoic thermal sag basins however the evolution of these basins was repeatedly overprinted by minor short term subsidence accelerations that reflect the build up of far field stresses related to rifting in the tethyan and atlantic domains comparison of observed and modelled subsidence curves suggests that in the area of the rhine rift system the lithosphere had equilibrated with the asthenosphere at the end of the cretaceous at depths of 100 120 km before it became thermally destabilized again by cenozoic rifting and plume related magmatism modelled subsidence curves indicate that by the end of early permian times the thermal thickness of the remnant mantle lithosphere ranged between 10 and 50 km in areas that were later incorporated into mesozoic thermal sag basins this corresponds to mid permian thermal lithosphere thicknesses of 40 80 km the geological society of london 2004

compression and right lateral strike slip movement at the southern hunsruck borderfault southwest germany abstract compressional tectonic structures have been known from the southern hunsruck borderzone since the end of the last century in the western part of the borderzone the saar nahe syncline is upthrown whereas in the eastern part the hunsruck is upthrown against the saar nahe syncline folds with axes parallel and oblique to the 60 trending fault zone have been described in the past in the area between idar oberstein and kirn permian lava sheets are displaced in such a way that their recent distribution can be explained by a right lateral strike slip movement of 5 8 km the block of the saar nahe basin between the southern hunsruck borderfault and the saarbrucken anticline has been tilted to the ene since the late palaeozoic the transcurrent movement can only be related to the opening of the upper rhine graben ne sw and nne ssw trending folds in the rotliegend sediments are considered to be transpression structures related to strike slip movement in early tertiary times recent seismicity along the southern hunsruck borderzone indicates that this zone is still active

sequence stratigraphy and correlation of late carboniferous and permian in the cis europe tethyan area north africa arabia china gondwanaland and the usa abstract sequence stratigraphy was used to correlate the depositional chronology during permo carboniferous time in various sedimentary basins of gondwanaland western europe eastern europe tethyan area north africa arabia china and north america during late carboniferous and permian eleven second order sequences sos were recognised throughout the whole area the sequence si is serpukhovian pp namurian a pp and chesterian the sequence sii is serpukhovian pp bashkirian pp namurian a pp b c westphalian a b pp and morrowan the sequence siii is late bashkirian moscovian westphalian b pp c d and atokan desmoinesian the sequence siv is kasimovian early stephanian and missourian the sequence sv is gzhelian orenburgian late stephanian and virgilian the sequence svi is asselian autunian and nealian the sequences svii ix are saxonian sakmarian artinskian kungurian and leonardian hessian cathedralian the sequences sx xi are guadalupian and lopingian depending on the regional setting different relationships exist between marine transgression and the respective effects of tectonics and of sea level changes in western europe effects of the glacial processes in gondwanaland are partly balanced by the late compression in the hercynian belt during moscovian eastern europe tethyan area north africa china and north america show a good correlation between glacial ice melting processes in gondwanaland and the intensity of the transgression which is increased by the westward progradation of the orogeny in urals and appalachians in arabia tunisia and tethyan area the impact of the neotethys opening is obvious from the artinskian and mainly during the late permian

the permo carboniferous saar nahe basin south west germany and north east france basin formation and deformation in a strike slip regime the permo carboniferous saar nahe basin in south west germany and north east france formed at the boundary between the rhenohercynian and saxothuringian zones within the variscan orogen where non marine sediments were deposited in a narrow structurally controlled basin the basin has an asymmetrical geometry perpendicular to the south hunsruck fault however there is a lack of growth of the sediment pile into the fault and isopach maps show the depocentre always located adjacent to the south hunsruck fault but migrating towards the north east with time this pattern is typical of a strike slip basin indicating that the south hunsruck fault was a dextral strike slip fault during sedimentation tectonic subsidence curves indicate that during the middle devonian to early carboniferous the basin subsided due to thermal relaxation of the lithosphere a change to very rapid subsidence at the start of the westphalian continued until late in the autunian this was due to mechanical subsidence associated with strike slip movement on the south hunsruck fault towards the end of subsidence in the saar nahe basin the grenzlager volcanics introduced a thermal pulse into the crust leading to thermal cooling and relaxation of the lithosphere

new 40ar 39ar ages and geochemistry of late carboniferous early permian lamprophyres and related volcanic rocks in the saxothuringian zone of the variscan orogen germany

subsidence of the paris basin and its bearing on the late variscan lithosphere evolution a comparison between plate and chablis models abstract in this study two different models for the lithospheric thermal evolution are used to predict the long term subsidence of the paris basin the plate or chablis models have a constant temperature or constant heat flow at the base of the lithosphere these boundary conditions yield a different thermal relaxation time for a given equilibrium lithospheric thickness the final thermal steady state does not depend on the boundary condition fixed at the base of the lithosphere the thermal evolution of the lithosphere is computed taking into account temperature and pressure dependent thermal characteristics metamorphism in the crust top crustal erosion and phase transition in the mantle spinel garnet the long term tectonic subsidence of the paris basin constrains the mesozoic thermal evolution of the lithosphere and the amplitude of the initial thermal anomaly the chablis model including the effects of spinel garnet phase transition predicts present day lithospheric thickness in better agreement with observation than the plate model the chablis model involves a basal heat transfer of 37 mw m2 similar to the value beneath oceanic plates the long term subsidence of the paris basin obviously results from the decay of a thermal anomaly initiated during late variscan times we first assume that at 300 ma the lithosphere was less than 150 km thick and the thickened crust started returning to its present thickness 35 km by uniform lithospheric extension the subsidence data can be explained by short stephano autunian as well as long stephano triassic lasting extension these hypotheses both implicitly refer to extensional collapse of the variscan belt however the evolution of the variscan belt from 350 to 300 ma may have involved almost no crustal thickening but an anomalously thin lithosphere ca 55 km the corresponding thermal evolution of the lithosphere is computed using the chablis model with an initially high heat transfer of 61 mw m2 at the base of the base of the lithosphere at 280 ma this heat transfer is tuned to 40 mw m2 leading to lithospheric cooling from 280 to 30 ma which can also explain the paris basin subsidence for the short lasting extension hypothesis the late variscan lithospheric evolution predicted with the chablis model yields paleogeography magmatism and retrograde p t t paths in good agreement with those reported from areas around the paris basin conversely the plate model does not allow mantle melting during the end of carboniferous and permian times the long lasting extension hypothesis does not explain the paleogeographic evolution the timing of magmatism and retrograde p t paths showing isothermal decompression the hypothesis with a strong lithospheric delamination cannot be ruled out however it is less plausible than the extensional collapse hypothesis

age of intrusion and rapid cooling of the frankenstein gabbro odenwald sw germany evidenced by40ar 39ar and single zircon207pb 206pb measurements the frankenstein gabbro complex in the northern odenwald fr germany is one of the hercynian plutonic bodies of the saxothuringian zone in the variscan belt 87sr 86sr isotopic investigations on pyroxene 40ar 39ar age determinations on hornblendes plagioclases biotites and pyroxenes and207pb 206pb dating on single zircon crystals have been carried out

variscan molasse in the saar nahe basin w germany upper carboniferous and lower permian the saar nahe basin is a permocarboniferous molasse basin within the variscan orogenic chains surface access is possible in an area of 100 40 km just south of the rheinisches schiefergebirge below a thick mesozoic cover the basin has a total extension of about 300 100 km 4 1 km upper carboniferous and 1 6 km lower rotliegend grey fluviolacustrine deposits and additional 1 8 km upper rotliegend red alluvial deposits were accumulated

the terrane concept and its manifestation by deep reflection studies in the variscides summary the terrane concept is understood as an important extension of plate tectonics and is based on the recognition of allochthonous mobile geological units the concept is successfully applied to the variscides with their wide range of collisional belts it is mainly supported by the dense deep seismic network of dekorp which reveals certain reflectivity patterns and succeeds in mapping old and new deep fault zones between the terranes variscan terranes are rooted in the ductile lower crust and seem to consist of continental crust only partly exclusively of rigid upper crust oceanic terranes on the other hand are always rooted in the asthenosphere the development of continental terranes and their boundaries depends strongly on their thermal and rheological history in the case of post orogenic collapse with heating and extension of the lower crust seismic lamellae develop and often truncate former thrust faults

crustal structure of the rhenish massif results of deep seismic reflection lines dekorp 2 north and 2 north q the reflection seismic line dekorp 2 n reveals an almost complete cross section through the rhenohercynian zone the most external part of the variscan orogen in europe

development of asymmetric basins along continental transform faults abstract many basins associated with wrench or transform faults are asymmetrical both longitudinally and laterally the sense of basin asymmetry changes along the strike of transform faults geophysical data from the dead sea rift and other transforms indicate that wrench induced asymmetric basins are bounded on only one side by a transform fault this implies that during the evolution of such basins maximum compression was parallel to the transform the direction of extension can change during the geologic evolution of a basin a possible explanation of this observation takes the strength of the fault into into consideration in the case of a weak fault in a strong crust the horizontal principal stresses would probably rotate to orientations parallel and perpendicular to the fault thus minimizing the shear stress on the main fault basins formed by regional extension such as in the east african rift system sometimes show similar features recent studies have shown that these basins often undergo oblique extension this suggests that the asymmetry in these basins may result from simultaneous strike slip motion and fault normal extension similar to the way asymmetry is produced in large transform basins periods of oblique extension can alternate with periods of orthogonal extension the asymmetry formed during periods of oblique extension is often preserved in the stratigraphic record

contraints on the evolution of the mid german crystalline rise a study of outcrops west of the river rhine several small outcrops along the western rhinegraben escarpment expose rocks which represent the western prolongation of the so called mid german crystalline rise this basement ridge separates the rhenohercynian and saxothuringian zones of the variscan belt of europe and thus marks the boundary between the external and the internal zones the variable rock association includes an orthogneissamphibolite complex weakly deformed low grade sediments devonian and visean and a number of different syn to post orogenic granodioritic to granitic intrusives all crosscut by late lower carboniferous undeformed lamprophyric dikes and unconformable overlain by permian sediments and volcanics