inversion of fluvial channels for paleorock uplift rates in taiwan the transient response of erosion to changes in rock uplift rate leads to the preservation of rock uplift history in the long profiles of rivers however extracting this information is nontrivial as changes in channel steepness are the result of both spatial and temporal changes in rock uplift rate as well as other factors such as climate and rock type we exploit an analytical linear solution for river channel profile evolution in response to erosion and tectonic uplift to investigate the rock uplift history of taiwan the analytical approach allows us to solve the linear inverse problem efficiently extracting rock uplift as a function of space and time from digital elevation data we assess the potential of fluvial topography to resolve rock uplift rates using three approaches 1 a synthetic resolution test 2 analysis of the forward model to demonstrate where in space and time the fluvial topography constrains rock uplift rate and 3 interpretation of the model resolution matrix furthermore the potential to analyze large data sets reduces the influence of stochastic processes such as landslides small scale river network reorganization and also local lithological variability in taiwan our analysis suggests that current rock uplift rates exceed erosion rates across much of the island and that there has been an increase in rock uplift rates since 0 5 ma across the central range

structural development of the fennoscandian border zone offshore denmark abstract the hans 1 saeby 1 and terne 1 wells are located within the danish part of the fennoscandian border zone and provide significant new data pertaining to the evolution of this important tectonic belt all three wells encountered palaeozoic and mesozoic rocks the cambrian to lower silurian deposits can be closely correlated to sections known from bornholm and scania and tectonic activity within the fennoscandian border zone cannot be verified during this time interval the thick upper silurian shales were probably deposited in a rapidly subsiding foreland basin marginal to the speculative caledonian deformation front which lies south of the ringkobing fyn high a major hiatus comprises the devonian and early carboniferous upper carboniferous sediments were deposited before a phase of rifting upper carboniferous intrusive and extrusive volcanic rocks suggest tectonic activities heralding the rifting phase extensive block faulting occurred in the border zone during the rotliegende and more than 650 m of reworked volcanic rocks were deposited in an alluvial fan environment syndepositional erosion created a major unconformity before the deposition of post rift zechstein sediments during the mesozoic the fennoscandian border zone was divided into two zones the sorgenfrei tornquist zone to the west and the skagerrak kattegat platform to the east the sorgenfrei tornquist zone continued to experience tectonic activity in triassic and middle jurassic times the zone has experienced an uplift of 1700 2000 m during late cretaceous to early tertiary inversion tectonics and the late tertiary uplift of fennoscandia

evolution of paleostress fields and brittle deformation of the tornquist zone in scania sweden during permo mesozoic and cenozoic times abstract the nw se oriented sorgenfrei tornquist zone stz has been thoroughly studied during the last 25 years especially by means of well data and seismic profiles we present the results of a first brittle tectonic analysis based on about 850 dykes veins and minor fault slip data measured in the field in scania including paleostress reconstruction we discuss the relationships between normal and strike slip faulting in scania since the permian extension to the late cretaceous tertiary structural inversions our paleostress determinations reveal six successive or coeval main stress states in the evolution of scania since the permian two stress states correspond to normal faulting with ne sw and nw se extensions one stress state is mainly of reverse type with ne sw compression and three stress states are strike slip in type with nnw sse wnw ese and nne ssw directions of compression the ne sw extension partly corresponds to the late carboniferous permian important extensional period dated by dykes and fault mineralisations however extension existed along a similar direction during the mesozoic it has been locally observed until within the danian a perpendicular nw se extension reveals the occurrence of stress permutations the nnw sse strike slip episode is also expected to belong to the late carboniferous permian episode and is interpreted in terms of right lateral wrench faulting along stz oriented faults the inversion process has been characterised by reverse and strike slip faulting related to the ne sw compressional stress state this study highlights the importance of extensional tectonics in northwest europe since the end of the palaeozoic until the end of the cretaceous the importance and role of wrench faulting in the tectonic evolution of the sorgenfrei tornquist zone are discussed

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

new insights into the india asia collision process from cretaceous paleomagnetic and geochronologic results in the lhasa terrane abstract to further constrain the india asia collisional process a combined paleomagnetic and geochronologic study has been carried out on the upper cretaceous jingzhushan formation redbeds and the lower cretaceous dianzhong formation volcanic rocks dated at 121 117 ma from the cuoqin area in the central lhasa terrane stepwise thermal demagnetization successfully isolated reliable characteristic remanent magnetization chrm directions that include dual polarity and pass positive fold tests at 95 and 99 confidence levels indicating prefolding primary magnetizations the tilt corrected site mean direction for 33 redbed sites is d 316 8 i 30 2 with 95 5 4 corresponding to a paleopole at 49 0 n 344 3 e with a 95 5 3 and the other for 12 volcanic sites is d 350 5 i 25 5 with 95 7 7 corresponding to a paleopole at 70 5 n 292 9 e with a 95 7 4 our new paleomagnetic results together with reliable cretaceous paleomagnetic data obtained from the lhasa terrane demonstrate that the southern margin of asia was located at 15 1 n during the cretaceous comparison with the apparent polar wander paths apwp of india and the cretaceous paleocene paleopoles of the himalayan terrane suggests that the india asia collision was likely a complex process which consists of the collision of the lhasa and himalayan terranes at 54 0 2 1 ma the longtime subduction of an intra oceanic basin between the himalayan terrane and the indian craton from 54 0 to 40 4 ma and the collision of the himalayan terrane and the indian craton at 40 4 4 1 ma comparing with the late cretaceous average pole of the east asia apwp reveals that a latitudinal convergence of 780 240 km has taken place between the lhasa terrane and east asia the hexi corridor since the india asia collision the amount of latitudinal shortening deduced from paleomagnetic data is very consistent with the 600 1000 km accommodated by the cenozoic fold and thrust belts between the lhasa terrane and hexi corridor

paleostress field reconstruction in the oslo region abstract the geodynamic history of a region is archived in its geologic record which in turn may reflect deformation patterns that causally can be related to certain configurations of paleostresses in the oslo region the exposed geological record ranges from precambrian high grade metamorphic rocks through cambro silurian sedimentary rocks to permo carboniferous sedimentary and magmatic rocks the latter being related to the development of the oslo rift system we investigate the kinematics of outcrop scale faults to derive the diversity of paleostress states responsible for the observed strain for this purpose we combine different graphical and numerical approaches to separate heterogeneous fault slip data sets and estimate the associated reduced stress tensors a reduced stress tensor consists of the directions of the three principal stress axes with 1 2 3 and the ratio of principal stress differences r 2 3 1 3 the present study gives evidence for three major regional paleostress fields that affected the oslo region a compressional stress field with a nw se directed maximum compression 1 has been identified as a caledonian imprint the most prominent regional stress field however is tensional characterised by a wnw ese directed minimum compression 3 and related to the permo carboniferous rifting later the area was affected by a wrench regime with a roughly n s directed 1 and a maximum age of permian whereas the absolute timing of this stress field is unclear due to the lack of exposed rocks younger than permian for a large number of estimated stress states none of the principal axes are sub vertical these oblique paleostresses cannot be integrated into a common regional stress field but rather correspond to local effects of intense magmatic activity during the permo carboniferous phase of rifting the present study tends to show that the oslo region remained unaffected by major tectonic activity for much of the mesozoic and cenozoic which is when the central european basin system to the south experienced several phases of intense deformation

the tectonic evolution of the fennoscandian border zone in denmark abstract the fennoscandian border zone is a complex tectonic zone defining the border between the stable fennoscandian baltic shield and the metastable danish basin and polish trough it forms the northwestern part of the tornquist teisseyre lineament one of the major european tectonic sutures intricate tectonic movements took place within the fennoscandian border zone from early paleozoic to recent time it is postulated that its evolution was dominated during the early palaeozoic by tensional tectonics and during the late paleozoic by dextral wrench movements the latter led to the development of curvilinear faults and the subsidence of pull apart basins transtensional stresses governing the triassic to early cretaceous evolution of the fennoscandian border zone induced the differential subsidence of rift basins during the late cretaceous and early cenozoic dextral transpressional stresses induced the partial inversion of mesozoic basins associated with the fennoscandian border zone this is reflected by the uplift of a major anticlinorium over which cretaceous strata became progressively truncated whilst adjacent areas developed into late cretaceous early tertiary depocentres basin inversion diminishes to the northwest along the fennoscandian border zone and disappears in the skagerrak area

paleo depth of fossil faults estimated from paleostress state applications from the alps and the apennines italy abstract estimating the paleo depth of a fossil fault usually requires the application of complex and highly specialized techniques we propose a new method that is based mainly on field data and simplifies the process calculation of the reduced stress tensor with four variables through inversion of fault slip data calculation of the complete stress tensor i e the two remaining unknowns using the friction and the rupture laws estimation of the paleo depth the friction law is defined by the lower boundary of the cloud of points in the mohr space represented by inherited faults this operation fixes the abscissa origin of the mohr diagram to calculate the rupture law we estimate both intact rock and outcrop quality parameters and need pairs of conjugate faults their dihedral angle fixes a point on the mohr circle where the rupture law has to be tangent thus defining the scale of the axes and the values of the principal stresses to define the paleo depth we estimate the average density of overlying rocks and the hydraulic conditions i e the pore pressure testing of this workflow in three well constrained geological case studies proved its promising reliability showing a good agreement with independent stratigraphic and structural evidence

seismostratigraphy and structural framework of the sw baltic sea the sw part of the baltic sea between scania rugen bornholm and mon constitutes a complex crustal transition between the baltic shield and the accreted phanerozoic provinces of the west european platform an integrated interpretation of marine reflection seismic data sets from the babel ac line and two commercial surveys offshore ne germany and s sweden have resulted in a complete view of the structural framework in the area the general seismic picture can best be detected by two characteristic sets of reflection phases the lower set is dominated by slightly dipping and vertically displaced prominent reflectors corresponding to downfaulted lower palaeozoic strata on top of the precambrian basement the upper set represents mesozoic and cenozoic coherent reflection phases including a thick upper cretaceous unit the caledonian deformation front is identified in the southern part of the investigated area as the border against which basement rocks have been affected by caledonian metamorphism and deformation major structural elements also include the n s trending agricola svedala fault and north rugen skurup fault several nw se trending faults are also identified including the nordadler kamien fault jutland mon fault carlsberg fault romeleasen fault zone and the fyledalen fault zone the sedimentary record from ne german offshore wells and scanian boreholes is compared with the seismic data the cambro silurian strata are composed mainly of quartzitic sandstones shales and biomicritic limestones the silurian is dominated by grey micaceous shale and micaceous siltstone deposited in a marginal basin upper palaeozoic strata are merely encountered in the southernmost part of the investigated area these include zechstein strata the mesozoic deposits are dominated by a thick cretaceous sequence of mainly limestones with interbedded sandstones

the sorgenfrei tornquist zone as the mantle edge of baltica lithosphere new evidence from three dimensional seismic anisotropy joint analysis of shear wave splitting parameters and directional dependence of teleseismic p residuals based on data from the seismic experiment tor across the trans european suture zone suggest that the sorgenfrei tornquist zone stz in northern denmark forms the south western margin of baltica in the upper mantle different lithosphere thickness and different orientation of seismic anisotropy in the mantle lithosphere identify three domains separated by the stz between denmark and southern sweden and the thor suture between northern germany and denmark we suggest that the anisotropy reflects frozen in olivine fabrics most probably created during early stages of the evolution of the european continent the middle danish block might represent a microplate caught in between avalonia and baltica before the caledonian orogeny

the post triassic evolution of the sorgenfrei tornquist zone results from thermo mechanical modelling abstract the sorgenfrei tornquist zone stz is part of the fennoscandian border zone separating the danish basin from the fennoscandian shield the stz as a structural element is of palaeozoic origin and represents the north westerly segment of the tornquist teisseyre zone which separates the younger west european crust from the older east european platform and extends from the black sea to the eastern north sea area the stz was reactivated in triassic jurassic extension and late cretaceous and paleogene compression this paper investigates the regional geological consequences of the reactivations by quantitative modelling along a profile across the stz in the danish area the numerical model invokes elastic viscous and plastic deformations of the lithosphere as well as surface processes governed by erosion sedimentation and lateral transport under the influence of eustatic sea level variations and regional isostatic compensation surface processes and lithospheric mechanics are coupled through thermal blanketing effects and loading the results in general address the regional geological consequences of the existence of intracontinental zones of structural weakness more specifically the results show that the late cretaceous and paleogene chalk depocentres in the danish basin are a direct consequence of the inversion of the stz and that the stz inversion together with falling sea level in cenozoic time are amongst the principal controlling factors in the geological evolution in the eastern north sea area

analysis of fault slip inversions do they constrain stress or strain rate fault slip data commonly are used to infer the orientations and relative magnitudes of either the principal stresses or the principal strain rates which are not necessarily parallel or equal at the local scale of an individual fault the shear plane and slip direction define the orientations of the local principal strain rate axes but not in general the local principal stress axes at a large scale the orientations of p and t axes maxima for sets of fault slip data do not provide accurate inversion solutions for either strain rate or stress the quantitative inversion of such fault slip data however provides direct constraints on the orientations and relative magnitudes of the global principal strain rates to interpret the inversion solution as constraining the global principal stresses requires that 1 the fault slip pattern must have a characteristic symmetry no lower than orthorhombic 2 the material must be mechanically isotropic and 3 there must be a linear constitutive relationship between the global stress and the global strain rate isotropic linear elastic constitutive equations are appropriate to describe the local deformation surrounding an individual slip discontinuity fault slip inversions however constrain the characteristics of a large scale cataclastic flow which is described by constitutive equations that are probably but to an unknown degree anisotropic and nonlinear such material behavior would not strictly satisfy the requirements for the stress interpretation thus at the present state of knowledge fault slip inversion solutions are most reliably interpreted as constraining the principal strain rates

andean flat slab subduction through time the analysis of magmatic distribution basin formation tectonic evolution and structural styles of different segments of the andes shows that most of the andes have experienced a stage of flat subduction evidence is presented here for a wide range of regions throughout the andes including the three present flat slab segments pampean peruvian bucaramanga three incipient flat slab segments carnegie guanacos tehuantepec three older and no longer active cenozoic flat slab segments altiplano puna payenia and an inferred palaeozoic flatslab segment early permian san rafael based on the present characteristics of the pampean flat slab combined with the peruvian and bucaramanga segments a pattern of geological processes can be attributed to slab shallowing and steepening this pattern permits recognition of other older cenozoic subhorizontal subduction zones throughout the andes based on crustal thickness two different settings of slab steepening are proposed slab steepening under thick crust leads to delamination basaltic underplating lower crustal melting extension and widespread rhyolitic volcanism as seen in the caldera formation and huge ignimbritic fields of the altiplano and puna segments on the other hand when steepening affects thin crust extension and extensive within plate basaltic flows reach the surface forming large volcanic provinces such as payenia in the southern andes this last case has very limited crustal melt along the axial part of the andean roots which shows incipient delamination based on these cases a palaeozoic flat slab is proposed with its subsequent steepening and widespread rhyolitic volcanism the geological evolution of the andes indicates that shallowing and steepening of the subduction zone are thus frequent processes which can be recognized throughout the entire system

mesozoic mafic alkaline magmatism of southern scandinavia more than 100 volcanic necks in central scania southern sweden are the product of jurassic continental rift related mafic alkaline magmatism at the southwest margin of the baltic shield they are mainly basanites with rarer melanephelinites both rock groups display overlapping primitive mg numbers cr and ni contents steep chondrite normalized rare earth element patterns lan ybn 17 27 and an overall enrichment in incompatible elements however the melanephelinites are more alkaline and have stronger high field strength element enrichment than the basanites the existence of distinct primary magmas is also indicated by heterogeneity in highly incompatible element ratios e g zr nb la nb trace element modelling indicates that the magmas were generated by comparably low degrees of melting of a heterogeneous mantle source such a source can best be explained by a metasomatic overprint of the mantle lithosphere by percolating evolved melts the former existence of such alkaline trace element enriched melts can be demonstrated by inversion of the trace element content of green core clinopyroxenes and anorthoclase which occur as xenocrysts in the melanephelinites and are interpreted as being derived from crystallization of evolved mantle melts jurassic magmatic activity in scania was coeval with the generation of nephelinites in the nearby egersund basin norwegian north sea both scanian and north sea alkaline magmas share similar trace element characteristics mantle enrichment processes at the southwest margin of the baltic shield and the north sea basin generated trace element signatures similar to those of ocean island basalts e g low zr nb and la nb but there are no indications of plume activity during the mesozoic in this area on the contrary the short duration of rifting absence of extensive lithospheric thinning and low magma volumes argue against a mesozoic mantle plume it seems likely that the metasomatic imprint resulted from the earlier permo carboniferous rifting episode which affected the entire study area and clearly was accompanied by plume activity ernst and buchan in american geophysical union pp 297 337 1997 renewed rifting in jurassic times triggered decompression melting in the volatile enriched lithospheric mantle and the alkaline melts generated inherited the earlier stored plume signature

variscan to alpine heterogeneous palaeo stress field above a major palaeozoic suture in the carpathian foreland southeastern poland abstract the tectonic evolution of the region adjacent to the sw border of the east european craton is crucial for understanding the palaeozoic amalgamation of europe and its later evolution we present a structural analysis of the brittle deformation fault slip data inversion and folding carried out in the cambrian to cenozoic rocks of the european platform in se poland to characterize the late palaeozoic maastrichtian palaeocene and miocene tectonics of this region the variscan late carboniferous palaeo stress pattern was characterized by n s to nne ssw oriented compression as inferred from the folding of the palaeozoic mainly devonian rocks the compression was associated with the northwesterly present day coordinates motion of gondwana towards the northerly situated laurussia subsequently the mid polish trough mpt developed in an extensional regime the stress regime changed to compressional at the maastrichtian palaeocene transition in response to the africa europe plate kinematics the compressional regime induced the tectonic inversion of the mid polish trough the stress pattern was characterized by ne sw oriented compression in the holy cross mts hcm area and in the radomsko high folds and faults in the mesozoic cover revealed a sinistral reactivation of the holy cross fault hcf and of nw se trending faults the alpine stress patterns were related to the subduction of the european platform beneath the carpathian orogen the flexural bending of the subducted lithosphere induced a homogeneous middle miocene n s extension in the carpathian foreland subsequently the northward propagation of the carpathian front resulted in late middle miocene n s compression restricted to the proximal area of the frontal thrusts implied by a strain partitioning at a low friction contact between the carpathian nappes and the european platform since the palaeozoic the teisseyre tornquist zone ttz behaved as lithospheric weak zone which has been reactivated during the maastrichtian palaeocene change in stress regime it resulted in the tectonic inversion of the polish trough inherited faults conditioned superficial stress perturbations and focused the deformation

unravelling polyphase brittle tectonics through multi software fault slip analysis the case of the voltri unit western alps italy abstract we have analyzed the brittle structures in a key area of the alps apennines transition zone nw italy here two orogens have interfered with each other since oligocene times producing a complex structural evolution and a heterogeneous fault population only relative chronologies can be reconstructed as stratigraphic constraints are lacking we have performed the inversion of fault slip data with two softwares for paleostress calculations combined with field observations at selected structural stations and photo interpretation the resulting incompatible stress tensors can be grouped in this sequence i a strike slip tensor with nnw sse trending 1 event a ii a strike slip tensor with ne sw trending 1 event b and iii an extensional transtensional tensor with nw se or ne sw trending 3 event c we correlated our results with structures of known age from adjacent areas event a is possibly rupelian early chattian linked to far field incipient rifting in the future ligurian provencal basin event b fits oligo miocene shortening the faults may belong to a sinistral strike slip zone that accommodated the oblique component of deformation during the rotation of the corsica sardinia block event c is attributed to a pliocene quaternary neotectonic event therefore combining different inversion procedures with a detailed structural analysis has successfully unravelled the polyphase brittle tectonics

illite and hydrocarbon exploration illite is a general term for the dioctahedral mica like clay mineral common in sedimentary rocks especially shales illite is of interest to the petroleum industry because it can provide a k ar isotope date that constrains the timing of basin heating events it is critical to establish that hydrocarbon formation and migration occurred after the formation of the trap anticline etc that is to hold the oil illite also may precipitate in the pores of sandstone reservoirs impeding fluid flow illite in shales is a mixture of detrital mica and its weathering products with diagenetic illite formed by reaction with pore fluids during burial k ar ages are apparent ages of mixtures of detrital and diagenetic end members and what we need are the ages of the end members themselves this paper describes a methodology based on mineralogy and crystallography for interpreting the k ar ages from illites in sedimentary rocks and for estimating the ages of the end members

the famatina complex nw argentina back docking of an island arc or terrane accretion early palaeozoic geodynamics at the western gondwana margin

comparative k ar and rb sr age determinations of retrograde processes on rocks from the ktb deep drilling project conventional k ar and rb sr age determinations were carried out on fine mineral fractions of the ktb rocks and of rocks from the surrounding area in order to get an idea of the timing of retrograde processes which the rocks had suffered in the late variscan and afterwards coarse grained mica minerals were used as reference minerals it can be demonstrated that conventional k ar dating on fine mineral fractions is a useful tool to date retrograde processes in crystalline rocks for methodical reasons the rb sr method is less suitable a complex age pattern was found which could be divided into different age groups representing different periods of either penetrative retrograde overprint or formation and reactivation of distinct cataclastic fault zones whereas the rocks of the ktb have undergone a penetrative retrograde overprint during the permo triassic without any visible deformation the jurassic brought a first reactivation of cataclastic fault zones in cretaceous time an overprint led to a pronounced second reactivation of cataclastic fault zones this latter process turned out to be the important one for the stacking and a repetition of the drilled profile in the ktb the data and interpretations obtained on the fine mineral fractions coincide excellently with fission track data on sphene from the drill site with sedimentological records concerning a larger regional scale and with hydrothermal alterations and ore forming events in mid europe

brittle tectonic evolution and paleostress field reconstruction in the southwestern part of the fennoscandian shield forsmark sweden 1 six hundred fault slip data have provided robust paleostress fields within an approximately 35 km3 volume of paleoproterozoic 1 9 ga rocks in the southwestern fennoscandian shield forsmark sweden these rocks were affected by penetrative ductile strain from 1 87 to 1 86 ga folding ductile strain along discrete zones around 1 8 ga and semibrittle or brittle deformation around and after 1 8 ga compatible paleostress fields have been identified using site by site and merged data sets from outcrops and oriented drill cores transpressive deformation with a regional nnw sse 1 axis associated with clockwise stress deviation inside a tectonic lens resulted in dextral slip along regionally significant steep wnw ese and nw se deformation zones the semibrittle and most of the brittle structures including specifically the epidote bearing fractures were established during this oldest regime around 1 8 ga latest svecokarelian a younger paleostress field with a ne sw 1 axis which was also transpressive in character is inferred to have been active at 1 7 1 6 ga the best defined paleostress field is transpressive in character with a wnw ese 1 axis that resulted in sinistral reactivation along the wnw ese and nw se zones the main set of laumontite stepped faults developed at this stage at 1 1 0 9 ga sveconorwegian it is impossible to exclude fully the influence of reactivation during even younger phanerozoic tectonic events subordinate extensional paleostress fields were related either to the latest svecokarelian and sveconorwegian transpressive regimes due to 1 and 2 stress permutations or to regional extensional tectonic regimes during the meso or neoproterozoic or later during the permo carboniferous and or mesozoic

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

the paleocene stratigraphic records in the central netherlands and close surrounding basins highlighting the different responses to a late danian change in stress regime within the central european basin system despite their similar structural style of inversion under late cretaceous compressional stress basins in the central european basin system showed different kinematic responses to a late danian change in the european intra plate stress field the late cretaceous phase was recognized throughout the central european basin system by compressional inversion of the mesozoic rifts and the simultaneous formation of marginal troughs the late danian change in stress regime resulted in a middle paleocene phase which excited longer wavelength of vertical surface movements in several basins in central europe this middle paleocene phase was characterized by domal uplift of the late cretaceous inversion zones and their proximal areas which was interpreted to result from a sudden relaxation of the in plane tectonic stress a so called relaxation inversion based on the paleocene stratigraphic records this study shows that some basins in the south western part of the central european basin system experienced subsidence of the late cretaceous inversion zones during the middle paleocene phase or the complete opposite vertical surface movements of a relaxation inversion two possible mechanisms superposition of relaxation inversions and lithospheric folding during compression are discussed that could provide an explanation for the opposite late danian and selandian vertical surface movements of nearby basins in the central european basin system

pre break up palaeostress state along the east greenland margin this paper describes intraplate deformation and the palaeostress state along the east greenland margin during the paleocene between 65 and 55 myr ago prior to the onset of the ne atlantic spreading it is shown that the pre break up deformation is the result of dip oblique strike slip tectonics in the se and compressive tectonics in the north the reduced palaeostress tensors derived from inversion of the fault slip data show that the maximum horizontal stress 1 is compressive and the orientations of 1 change from ene wsw in the south to nne ssw in the north the reconstructed palaeostress trajectory map demonstrates that the 1 orientations reflect the plate motion path and define small circles whereas the trends of the minimum horizontal stress 3 converge and cluster around an area in the arctic that is interpreted as the rotation pole of greenland the intraplate deformation folding and uplift that affected the greenland and european margins the barents sea and the north sea during the paleocene can be explained by the counter clockwise rotation of greenland the present paper calculates the pole of rotation of greenland using the kinematics of brittle faults along the plate margin and the palaeostress derived from inversion of fault slip data analysis as an indicator of motion path

palaeozoic terranes and their lithospheric boundaries within the trans european suture zone tesz a review the trans european suture zone tesz is a broad and complex zone of terrane accretion separating ancient lithosphere of the baltic shield and east european craton eec from the younger lithosphere of western and southern europe there is debate about the number of terranes involved and their origins the most significant terrane boundaries originally oceanic sutures are poorly exposed and are defined using faunal provinciality prominent geophysical lineaments may represent sub terrane boundaries within composite terranes the avalonia composite terrane was amalgamated to baltica in latest ician time the provenance of the malopolska and moravo silesian terranes whose neoproterozoic basement is suspect with respect to baltica but with which they nonetheless share faunal affinities is still debated the extent of the variscide rhenohercynian zone defines the southern limit of the early palaeozoic accreted terranes terranes within the bohemian massif exhibit hp metamorphism recording subduction driven collision prior to incorporation in the tesz collage itself associated with a hp event in romania the saxothuringian zone and rheic suture are directly juxtaposed with the eec and the crustal structure of the tesz has been much modified by post palaeozoic tectonism deep seismic reflection data where available show that the oceanic sutures are frequently associated with inclined reflectivity zones irz in the lithospheric mantle here inferred to mark relict subduction zones interpreting the age of subduction is complicated by offset of originally coplanar mantle and crustal segments of the irz resulting from early orogenic lithospheric delamination at the moho interface and or post orogenic reordering processes the mantle irz appear to indicate a n directed polarity for early palaeozoic subduction apparently incompatible with the geological evidence which indicates subduction of the tornquist sea beneath avalonia and a large amount of underthrusting of avalonia by baltica possible explanations for these apparently incompatible observations are evaluated

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

upper plate deformation measured by gps in the coquimbo gap chile abstract since the mw 7 3 punitaqui earthquake in 1997 the area between 30 s and 32 s coquimbo illapel section of the chilean subduction has been the locus of a decennial seismic swarm a dense network of 30 benchmarks have been installed in this area and surveyed six times with high precision gps over the last 3 years surface deformation here is compatible with elastic loading due to partial locking on the subduction interface at depth here we show that in this area only 40 45 of the total convergence rate between nazca and south america plates gives way to accumulation of elastic deformation in the upper plate the remaining 60 55 being dissipated by free or aseismic slip the cumulative slip due to the seismic swarm explaining no more than 1 3rd to 1 4th of it we also find that the accumulation decreases northward to reach almost zero around 30 s la serena tongoy whether this is a steady state or only a transient pattern a steady decrease of coupling is not clear since our measurements span only 3 years and since early measurements 10 years ago were sparse and differ only marginally from ours

heterogeneous tectonic inversion of the mid polish trough related to crustal architecture sedimentary patterns and structural inheritance abstract using a 3 d structural model we performed a basin scale analysis of the tectonically inverted mid polish swell which developed above the nw se oriented teisseyre tornquist zone the later separates the paleozoic west european platform from the precambrian east european craton the model permits a comparison between the present depths and sedimentary thicknesses of five layers within the permian mesozoic and cenozoic successions the inversion of the nw se trending mid polish trough during the late cretaceous paleogene resulted in uplift of a central horst the mid polish swell bounded by two lateral troughs these structural features are induced by squeezing of a weak crust along the teisseyre tornquist zone the swell is characterized by an inherited segmentation which is due to ne sw transversal faults having crustal roots from nw to se we distinguish the pomeranian kujavian and malopolska segments that are separated by two transversal faults during the inversion the zechstein salt occurring in the pomeranian and kujavian segments in the nw acted as decoupling level between the basement and the post salt cover leading to disharmonic deformation conversely because no salt occurs in the se both basement and cover were jointly deformed the vertical tectonic uplift at the surface is estimated to amount to 3 km in the malopolska segment the structural inheritance of the basement is expressed by the heterogeneous geometry of the swell and tectonic instability during mesozoic sedimentation the reasons for the inheritance are seen in the mosaic type paleozoic basement sw of the teisseyre tornquist zone contrasting the precambrian east european craton which acted as a stable buttress in the ne the horst and trough geometry of cenozoic sediments blanketing the mid polish swell reveals the ongoing intracontinental compressional stress in poland

unraveling 1 5 ga of brittle deformation history in the laxemar simpevarp area southeast sweden a contribution to the swedish site investigation study for the disposal of highly radioactive nuclear waste 1 5 ga of brittle deformation in sweden

interpretation of k ar dates of illitic clays from sedimentary rocks aided by modeling k ar dates of illitic clays from sedimentary rocks may contain mixed ages i e may have ages that are intermediate between the ages of end member events two phenomena that may cause mixed ages are 1 long lasting reaction during the burial illitization of smectite and 2 physical mixing of detrital and diagenetic components the first phenomenon was investigated by simulation of illitization reactions using a nucleation and growth mechanism these calculations indicate that values for mixed ages are related to burial history for an equivalent length of reaction time fast burial followed by slow burial produces much older mixed ages than slow burial followed by fast the type of reaction that occurred in a rock can be determined from the distribution of ages with respect to the thickness of illite crystals dating of artificial mixtures confirms a non linear relation between mixed ages and the proportions of the components vertical variation of k ar age dates from gulf coast shales can be modeled by assuming diagenetic illitization that overprints a subtle vertical trend presumably of sedimentary origin in detrital mineral content

the crystal chemical basis for ar retention in micas inferences from interlayer partitioning and implications for geochronology cation partitioning data for coexisting muscovite and biotite are shown to be useful indicators of relative interlayer bond length strength in these minerals these data therefore provide a useful crystal chemical perspective on relative mass transfer kinetics of radiogenic isotopes and account for the observation that biotite is generally less retentive of 40ar and 87sr than coexisting muscovite partitioning behavior of trace elements underscores three reasons why overall interlayer bonding in biotite is weaker than in muscovite first the preferences of large rb cs in biotite and of small la3 and na in muscovite indicate a relatively spacious interlayer volume in biotite suggesting a longer mean k o bond second the preference of interlayer vacancies in biotite with some all possibly h2o h3o filled suggests that its adjacent 2 1 sheets are connected by fewer interlayer bonds per unit cell than those of muscovite third the relative exclusion of large ba2 from biotite despite its large interlayer sites is attributed to o h bonds pointing into the interlayer cavity sub normal to 001 k ba2 h repulsion thereby induced by the bare proton both destabilizes ba2 and weakens k o bonds in contrast muscovite offers a more favorable electrostatic environment for ba2 substitution since its o h bonds are directed into the vacant m1 octahedral site sub parallel to 001 this hypothesis is supported by the observation that progressive f oh 1 exchange enhances ba2 partitioning into biotite phlogopite relative to coexisting muscovite these crystal chemical differences between biotite and muscovite are mirrored in calculated values of ionic porosity z i defined here as the percentage of their interlayer unit cell volume not occupied by ions a monitor of ionic packing density and geometry z i is inversely correlated with k o bond strength which appears to be the rate determining kinetic common denominator for a variety of processes affecting micas including those responsible for loss of radiogenic isotopes in biotite and muscovite accordingly the relatively longer weaker k o bonds of biotite are envisioned as being more easily stretched during volume diffusion or broken during recrystallization or retrograde alteration this in turn accounts for common observations of enhanced radiogenic ar sr loss and younger 40ar 39ar and rb sr ages in natural biotite high z i relative to coexisting muscovite lower z i significantly this pattern may arise irrespective of isotopic loss mechanism diffusion or recrystallization etc and it follows that any age discordance observed between muscovite and biotite cannot be ascribed uniquely to one mechanism or the other without appropriate field petrographic and petrologic constraints extension of this partitioning porosity based synthesis leads to prediction of corollary age retentivity composition effects among chemically diverse trioctahedral and dioctahedral micas which are best field tested in terranes that cooled slowly under dry static conditions pressure effects on argon retention are also inferred from the porosity model

triassic and jurassic structural development along the tornquist zone denmark abstract in the danish area the old crustal weakness zone the tornquist zone was repeatedly reactivated during the triassic and jurassic early cretaceous causing minor dextral movements along the major boundary faults these tectonic events were minor as compared to the tectonic events of the late carboniferous early permian and the late cretaceous early tertiary although a dynamic structural and stratigraphical analysis indicate that the zone was highly active compared to the surrounding areas during the middle to late permian the area was exposed to erosion and became a peneplane a regional triassic subsidence produces seismic onlap towards the northeast where the youngest triassic sediment is found supercropping the precambrian basement during mainly the early triassic several of the major early permian faults became reactivated probably with dextral strike slip along the borglum fault the jurassic early cretaceous subsidence became restricted primarily to the area between the two main faults in the tornquist zone the grena helsingborg fault and the borglum fault this restricted basin development indicates a change in the regional stress field that seems to have come into existence during the transition between the triassic and the jurassic the subsidence in the middle jurassic and the late jurassic early cretaceous follows the early jurassic pattern with local subsidence in the tornquist zone but even more restricted to the zone the subsidence seems to have decreased in the middle jurassic hereafter subsidence increased again during late jurassic early cretaceous times a set of small faults were generated during the mesozoic internally in the tornquist zone this fault pattern indicates a broad transfer of strike slip oblique slip motion from the grena helsingborg fault to the borglum fault

fault gouge analyses k ar illite dating clay mineralogy and tectonic significance a study from the sierras pampeanas argentina we introduce a method for the detailed interpretation of k ar illite fine fraction ages of fault gouges from non sedimentary host rocks ages are cross evaluated with several independent parameters e g illite crystallinity illite polytype quantification grain size mineralogical observations k ar muscovite and biotite host rock cooling ages as well as low temperature thermochronological data aft ahe zhe this interpretation approach is applied to a regional study in order to constrain the deformation path of the eastern sierras pampeanas in nw argentina in the course of this study a large number of gouge bearing fault zones were systematically sampled and analysed obtained k ar illite fine fraction ages range from devonian to cretaceous times documenting a long lasting brittle fault activity in this region ages 320 ma are synchronous with a period of intra carboniferous compressional tectonism whereas permo triassic ages are contemporaneous to a flat slab subduction episode of the farallon plate beneath the south american plate middle to late permian and early triassic ages as well as early jurassic to middle cretaceous ages correlate with extensional tectonics in this region additionally k ar illite ages reveal a propagation of brittle deformation from north to south in the sierras de cordoba and san luis data integrity and consistency with other chronometers and geological evidence show that the here suggested interpretation is valid and can provide a powerful tool to evaluate cooling and deformation histories despite of that we could show that the reliability of fault gouge data strongly depends on the regional cooling

linking changes in tectonic style with magmatism in northern europe during the late carboniferous to latest permian abstract early carboniferous to permian magmatism associated with rifting within the northern foreland of the variscan orogen was widespread across europe during the long period of magmatic activity the regional tectonic setting changed across the region from early carboniferous extension and basin formation to a rifting wrenching style of deformation in the late carboniferous stephanian to early permian wrenching and faulting were accompanied by widespread voluminous and episodic magmatic extrusion intrusion and underplating this was followed by thermal relaxation and the development of the northern and southern permian basins in later permian times thermal relaxation was punctuated by a permo triassic phase of extension and graben formation 40ar 39ar ar step heating dating for mineral separates and whole rock samples of magmatic rocks from southern scandinavia oslo graben and south sweden and rugen north germany provides further radiometric evidence for three of the proposed periods of magmatic activity in the region latest carboniferous to earliest permian ages c 300 310 ma were obtained for volcanic rocks in the oslo graben and dolerite sills and dykes in south sweden and north germany this phase can be time correlated with magmatic activity that occurred throughout europe during large scale dextral wrenching that followed the variscan orogeny a second phase of alkaline intrusions is confined to the oslo graben and related to caldera collapse around c 275 ma the third permo triassic phase c 250 ma is considered to be related to a new tectonic cycle involving extension that triggered minor melting of enriched fertile mantle

deep seismic survey images crustal structure of tornquist zone beneath southern baltic sea the tornquist zone is europe s longest tectonic lineament and bisects the continent in a nw se direction from the north sea off nw denmark to the black sea new deep seismic reflection and coinci

seismic anisotropy of the lithosphere around the trans european suture zone tesz based on teleseismic body wave data of the tor experiment abstract a passive teleseismic experiment tor traversing the northern part of the trans european suture zone tesz in germany denmark and sweden recorded data for tomography of the upper mantle with a lateral resolution of few tens of kilometers as well as for a detailed study of seismic anisotropy a joint inversion of teleseismic p residual spheres and shear wave splitting parameters allows us to retrieve the 3d orientation of dipping anisotropic structures in different domains of the sub crustal lithosphere we distinguish three major domains of different large scale fabric divided by first order sutures cutting the whole lithosphere thickness the baltic shield north of the sorgenfrei tornquist zone stz is characterised by lithosphere thickness around 175 km and the anisotropy is modelled by olivine aggregate of hexagonal symmetry with the high velocity ac foliation plane striking nw se and dipping to ne southward of the stz beneath the norwegian danish basin the lithosphere thins abruptly to about 75 km in this domain between the stz and the so called caledonian deformation front cdf the anisotropic structures strike ne sw and the high velocity ac foliation dips to nw to the south of the cdf beneath northern germany we observe a heterogeneous lithosphere with variable thickness and anisotropic structures with high velocity dipping predominantly to sw most of the anisotropy observed at tor stations can be explained by a preferred olivine orientation frozen in the sub crustal lithosphere beneath northern germany a part of the shear wave splitting is probably caused by a present day flow in the asthenosphere

crustal structure along the egt profile across the tornquist fan interpreted from seismic gravity and magnetic data abstract the tornquist fan is a northwestward widening splay of late carboniferous to early permian fault zones in the danish area which emanates from the teisseyre tornquist zone in the baltic sea it is located over an area of deep sedimentary basins around denmark in the southwestern corner of the former baltica plate this paper presents an integrated model of seismic velocity density and magnetic properties along the egt profile across the tornquist fan between southern sweden and northern germany the model shows distinct features that may be related to the main tectonic events in the area the caledonian crustal suture between baltica and eastern avalonia is interpreted from changes in physical parameters at all crustal levels most noticeable as an abrupt lateral change in seismic velocity in the lowest crust at moho level from 6 9 km s in baltica to only 6 4 km s in eastern avalonia thick sedimentary successions beneath the mesozoic sequence are interpreted as palaeozoic sedimentary rocks which may have been deposited on the southern margin of the baltica plate in a deep caledonian foreland basin and in late carboniferous early permian rifts and extensional basins rift related magmatism is indicated by the presence of zones of high velocity density and magnetic susceptibility as well as strong remanent magnetization thermal subsidence following the emplacement of these bodies may be the origin of regional subsidence of the danish and north german basins of late paleozoic and mesozoic age late cretaceous to early cenozoic inversion of basin structures is detected at the sorgenfrei tornquist zone stz in the transition between shield and basin areas the stz coincides with a pronounced change in crustal thickness and the southwestern edge of a major magmatic intra crustal body significant abrupt changes in moho depth exist along the profile 26 30 km beneath the deep basins ca 35 km beneath the ringkobing fyn basement high and 48 km beneath the baltic shield around the sorgenfrei tornquist inversion zone the basement in the tornquist fan area is of proterozoic age the moho topography indicates strong thinning of the crust during its phanerozoic evolution the model supports the hypothesis that existing tectonic structures and weakness zones are continuously being reactivated during subsequent tectonic activity

paleostress reconstruction from kinematic indicators in the oslo graben southern norway new constraints on the mode of rifting abstract the oslo graben southern norway is a n s trending carboniferous permian rift system characterized by major mafic to silicic magmatism n s trending faults reactivation of preexisting precambrian faults and formation of half grabens magmatism is expressed by the presence of lavas dyke injections cauldron formation and the intrusion of batholiths paleostress analyses mainly based on slickensides have been performed in the area both within and outside the rift structure combined with the current tectono magmatic model of the oslo graben area the analyses show the following stress evolution from the caledonian orogeny with its compressional tectonics in the silurian to the late stages of the carboniferous permian rifting nw se compression occurred in silurian times due to the continental collision of the caledonian orogeny after a long period of a missing geological record the area was affected by n s compression during the late carboniferous a shallow sedimentary basin developed indicative for the pre and proto rift phases the transition from the proto rift phase to the initial rift phase is marked by a transition from a transpressional regime into a transtensional regime during the early permian the stress regime changed from pure extension to radial extension we suggest that the oslo graben can not simply be explained in terms of or passive or active rifting but that a combination of both evolving through time is more suitable to explain the observations we propose a model in which the oslo graben is initially triggered by far field stresses in the latest carboniferous and earliest permian which infers opening due to passive rifting these far field stresses are suggested to be linked to the hercynian orogeny active to the south in central europe in carboniferous times and the reorganisation of the pangea supercontinent in early permian times the stress regime caused radial extension indicative for uplift and a change to an active mode of rifting simultaneously with the radial extension large volumes of magma are emplaced at near surface levels despite all alternative models an anomalous thermal gradient is necessary to create these large volumes of magmatic material we propose therefore that shortly after the onset of rifting the dominant rifting mode becomes active plume related although far field stresses might still be present

variscan tectonics in the holy cross mountains poland and the role of structural inheritance during alpine tectonics abstract the present study was carried out in the holy cross mountains hcm of south central poland and includes computation of palaeostresses following angelier s method and field structural analysis the palaeozoic basement of the hcm comprises two tectonic units separated by the major wnw ese striking holy cross fault hcf fold analysis indicates a n s to nne ssw direction of variscan shortening micro structures and fold analysis from upper devonian rocks further reveal 1 a brittle tectonic event due to a nw se compression preceding folding that could be related to pre late carboniferous tectonics due to block transport within the tornquist teisseyre zone ttz and 2 polyphase variscan folding comprising a an early stage of n s shortening marked by north verging ramps b a main folding event and axial cleavage formation involving n s to nne ssw shortening and c a late stage of shortening deforming older folds and cleavage a mainly extensional tectonic regime dominated from the permian until the cretaceous during which time the hcf was reactivated as a normal fault large nw se faults bordering the mid polish trough mpt developed subsequent tectonic inversion of the mpt resulted in basin uplift mid polish swell mps palaeostress computations from mesozoic strata suggest a ne sw direction for the main maastrichtian paleocene shortening phase in addition to two minor brittle events resulting from n s and e w compression analysis of local folds in the mesozoic cover indicates a causal relationship with the maastrichtian paleocene reactivation of older faults in particular en echelon folds in the radomsko elevation suggest a sinistral reactivation of the palaeozoic hcf folds in the southwestern part of the hcm argue for reactivation in the reverse mode of a nw se trending fault bordering the mps that originated in the mesozoic in palaeozoic strata post variscan brittle deformation and micro fault reactivation are attributed to the tectonic events of maastrichtian paleocene age reactivation of n s fractures is demonstrated in the rzepka quarry where fractures in devonian dolomites are filled by calcite probably formed during a late variscan event and by younger late permian early triassic sediments they were subsequently reactivated as dextral strike slip faults during the ne sw maastrichtian paleocene compression

geodynamics of dobrogea romania new constraints on the evolution of the tornquist teisseyre line the black sea and the carpathians abstract dobrogea is the only place south of poland where the tornquist teisseyre line europe s longest lineament outcrops to characterize and date the tectonic activity of this line and to understand its relations with the neighboring structures e g the carpathians and the black sea basin the fracturing of late jurassic to neogene rocks in north central and south dobrogea is analyzed these paleostress reconstructions indicate that the dobrogea orogen was built under a n s compression with strain partitioning between thrusting at its front and dextral reverse slip along the peceneaga camena and capidava ovidiu faults during the late jurassic barremian from aptian to coniacian the dobrogea platform was characterized by se directed extension compatible with the aptian cenomanian rifting of the western black sea followed by the se directed drifting of a part of the moesian block i e the istanbul block on its southern extremity the tornquist teisseyre line does not show evidence for any large scale alpine strike slip movements postulated by many the peceneaga camena fault being reactivated in latest cretaceous paleogene as a pure reverse fault during the late tertiary the carpathian compression was poorly transmitted to dobrogea extension dominated the neogene deformation which indicates a weak coupling between the carpathians and its foreland

continental rift development in precambrian and phanerozoic europe europrobe and the dnieper donets rift and polish trough basins abstract upper crustal structure and lower crustal and mantle character of the european continental lithosphere differ significantly from west to east the processes of rifting of phanerozoic western europe s hotter thinner crust compared with the more stable thicker 45 vs 30 km proterozoic crust of the east european craton is being investigated by europrobe case studies of western and eastern european sedimentary basins the dnieper donets basin transects the southwestern part of the east european platform in a nw se direction lying between the ukrainian shield and the voronezh massif rifting took place from early frasnian until perhaps the late visean and was accompanied by major volcanic activity the distribution of both was affected by pre existing basement fault systems the syn and post rift sedimentary succession may be as thick as 20 km in the donets trough basin evolution and the present crustal geometry have been much affected by inversion during the permian in association with uralian orogenesis tectonic events of bathonian oxfordian 168 154 ma and turonian santonian 91 84 ma age are also recorded in the basin stratigraphy the polish trough lies along the boundary between the phanerozoic and proterozoic european crustal domains coincident with the trans european suture zone the presence of this rheological boundary may be paramount in structurally controlling the position of the trough tectonic subsidence analysis indicates an initial late rotliegendes early triassic syn rift phase of development subsequently episodes of increased tectonic subsidence rate occurred during the oxfordian tithonian 157 146 ma and beginning in the cenomanian 95 90 ma the oxfordian tithonian episode is likely the signature of a second extensional event correlated with intensification of rifting within the arctic north atlantic rift system while the cenomanian and later is a precursor to mild compressional intraplate orogenic movements present day crustal structure reflects the docking of phanerozoic crust against the proterozoic during palaeozoic orogenies permo carboniferous wrenching and transtensional modifications leading to formation of the polish trough as well as modifications during the late cretaceous early tertiary inversion process

palaeozoic structural development along the tornquist zone kattegat area denmark abstract the interpretation of newly released commercial 2d reflection seismic data in the kattegat area denmark has provided us with a better understanding of the palaeozoic tectonic processes along the tornquist fault zone a base palaeozoic time structure map a lower palaeozoic twt isopach map a true lower palaeozoic twt isopach map an upper carboniferous lower permian syn rift twt isopach map a top pre zechstein time structure map and a zechstein combined twt isopach and palaeogeography map have been generated the uniform lower palaeozoic sequence thickness in the kattegat both inside and outside the tornquist zone indicates only minor lateral movements if any whereas the extensive upper silurian sequence increasing in thickness to the north indicates a relatively fast regional subsidence the base palaeozoic time structure map and the late palaeozoic syn rift isopach map show a clear late palaeozoic extension in the area the syn rift isopach map in combination with the time equivalent opening of the skagerrak graben at right angles to the tornquist zone in the kattegat indicates that this extensional tectonic event had a dextral slip component measurements on internal extensional faults in the tornquist zone give a minimum right lateral displacement of 10 4 km the footwall blocks were deeply eroded during the early permian rifting and at zechstein times the area became a peneplane the tornquist zone was later exposed to several tectonic phases where dextral slip played a role indicated by the push up and pull down structures caused by restraining and releasing bends of the borglum fault the dextral displacement along the borglum fault since the beginning of the permian is in the order of 5 7 km based on the displacement of a lower palaeozoic local depocentre early permian depocentres and faults which gives a total amount of right lateral displacement since the early palaeozoic in the order of 15 20 km the continuously repeated tectonic episodes along the tornquist zone throughout most of the phanerozoic show that the zone was easily reactivated implying deep seated basement faults the tornquist zone can be seen as a buffer zone between continental blocks whenever changes in the regional stress field are induced

mesozoic and cenozoic tectonic evolution of scania southern sweden abstract triassic to early cretaceous transtensional sinistral tectonics induced the subsidence of fault bounded basins in scania late cretaceous dextral transpressional deformations induced the inversion of these basins and the uplift of major basement blocks the resulting structural relief is of the order of 2000 m

crustal motion in the southern andes 26 36 s do the andes behave like a microplate 1 a new global positioning system gps derived velocity field for the andes mountains 26 36 s allows analysis of instantaneous partitioning between elastic and anelastic deformation at the orogen s opposing sides adding an andes microplate to the traditional description of nazca south america plate convergence provides the kinematic framework for nearly complete explanation of the observed velocity field the results suggest the oceanic nazca boundary is fully locked while the continental backarc boundary creeps continuously at 4 5 mm yr the excellent fit of model to data 1 7 mm yr rms velocity misfit and the relative aseismicity of the upper crust in the interior andean region in comparison with its boundaries supports the notion that the mountains are not currently accruing significant permanent strains additionally the model implies permanent deformation is not accumulating throughout the backarc contractional wedge but rather that the deformation is accommodated only within a narrow deformational zone in the backarc

late holocene faulting in the southeast sierras pampeanas of argentina the seismic history of extra andean south america is poorly documented between lat 26 s and 33 s about 375 km east of the fold and thrust belt that marks the present orogenic front the block faulted crystalline basement uplifts of the sierras pampeanas in argentina reveal extensive quaternary reverse faulting 14c dates of 1080 70 and 1310 40 yr b p have been determined on organic material from colluvium on the footwall of the east dipping los molinos branch of the comechingones fault they indicate at least 2 1 m of slip probably coseismic during the past 1300 yr in an area for which no significant deformation has been reported in association with historical earthquakes

neogene inversion of the central graben and ringkobing fyn high denmark abstract inversion in the north sea area and onshore denmark is a well known phenomenon and the main phase is interpreted to have occurred in the cretaceous and early cenozoic this study demonstrates an important early neogene inversion phase that resulted in the most distinct flexuring of the southern danish central graben during the cenozoic reactivation of structures on the ringkobing fyn high also took place during this inversion phase apatite fission track data confirm marked uplift of the marginal areas of the fennoscandian shield the recognition of the inversion of the ringkobing fyn high is based on new high resolution seismic data and has not been reported previously minor inversion pulses continued throughout the early and middle miocene and ceased in the early late miocene the early neogene inversion was the last major influence of the alpine orogeny in the danish area as a consequence of the early neogene inversion clastic sediments were flushed into the norwegian danish basin due to increased relief in the hinterland the high sediment supply continued throughout the early miocene despite changing climatic conditions from an overall cold temperate climate to a subtropical climate at the transition from the early miocene to the middle miocene the high sediment yield however ceased due to marked subsidence in the middle late miocene following the last inversion pulse in the middle miocene

contemporary stress field distortion in the polish part of the western outer carpathians and their basement abstract the western carpathians seem to be the crucial place to understand the nature of the regional turn of the present day maximum horizontal stress shmax direction from the northwest which is characteristic for the west european stress province towards the north specific for the western edge of the east european platform shmax orientations have been investigated in fourteen deep wells located in the western part of the polish outer carpathians by borehole breakout analyses from six arm dipmeter data this tool proved to be useful to determine breakout orientation and to discriminate stress induced breakouts from mechanical failures of the borehole wall the analysed dipmeter data come from wells most of them deeper than 3000 m which penetrate cretaceous tertiary sequences of the carpathian flysch nappes 4 wells the palaeozoic tertiary autochthonous sedimentary cover of the upper silesian and the malopolska massifs 13 wells and their precambrian metamorphic basement 4 wells in the investigated part of the upper silesian massif shmax for separate depth sections shows a general counterclockwise rotation with increasing depth for the carpathian nappes breakout data of moderate quality indicate nne oriented shmax while for the autochthonous basement sequence good quality data point to a nnw mean direction of shmax in the deepest well sections which penetrate the crystalline basement of the upper silesian massif the tendency to further stress rotation towards the northwest was observed the range of the angular shmax rotation with depth for the utmost structural levels exceeds 60 in the central part and decreases to 40 for the eastern edge of the upper silesian massif no stress rotation is evident in the westernmost part of this massif numerous second and third order stress deviations give evidence for recent fault reactivation and rotational stresses in horizontal planes for the autochthonous sedimentary cover of the malopolska massif n to nne oriented compression was determined hitherto acquired data suggest insignificant stress rotation from the north in unfolded sequences of the miocene molasse beneath the nappes to the north northeast in deeper palaeozoic mesozoic complexes in one well ne trending shmax was determined in folded miocene molasse beneath the main decollement surface this stress orientation is similar to stress directions in the nappes covering the upper silesian massif shmax directions in the autochthonous complex beneath the nappes of the western outer carpathians generally are subperpendicular to the overall trend of the orogen creating a fan like pattern of stress trajectories nne oriented compression within the nappes covering the upper silesian massive within the autochthonous complex of the malopolska massif and in the carpathian foreland probably is exerted by the carpatho pannonian plate advancing towards the north northeast relative to the european plate active movement occurs along the mur muerz ilina fault zone on the western boundary of this plate and probably along the eastern carpathians suture on its eastern margin nw directed compression in the basement of the upper silesian massif is in agreement with shmax orientation within the bohemian massif and the west european stress province thus plate forces are thought to contribute to its origin

the atlas east variscan elbe shear system and its role in the formation of the pull apart late palaeozoic basins the variscan orogeny occurred as a result of the late devonian to late carboniferous collision and accretion of gondwana derived microcontinents and continental masses with those of laurussia the irregular boundaries of the colliding continents caused isochronous transpressional and transtensional tectonics accompanied by a complex pattern of intracontinental shear zones at the scale of the southern european variscides these shear zones and their configuration controlled the subsequent evolution of permian to middle triassic paleogeography the geographic distribution from morocco to the eastern alps of the late carboniferous permian up to triassic basins most of which are considered as pull apart basins was related with the development of the late palaeozoic intracontinental shear network our analysis of the stratigraphic tectonic and volcanic features of the late carboniferous permian continental basins across the laurussia gondwana boundary reveals the role of the east variscan shear zone during this time as a precursory lineament for the development of the permian to triassic rifting of pangaea and the following opening of oceanic basins e g the neothetyan ocean

late cretaceous early tertiary tectonic evolution of the central european basin system cebs constraints from numerical modelling abstract the results obtained from a suite of spherical thin sheet finite element model calculations on the late cretaceous early tertiary tectonic evolution of the area of the central european basin system cebs are presented and discussed the calculations incorporate the effects of variations in lithospheric structures and compositions and changes in the imposed boundary conditions the impact of lateral contrasts such as pre existing weak domains is quantified through a thermo mechanical model for the entire cebs the obtained predictions have been constrained by comparisons with more recent observed field data and resemble the present day dynamics and kinematics a trial and error reconstruction of the development through time of the dynamic of the alpine orogeny as well as of the early atlantic extension have been considered in order to investigate the role of boundary forces in the late cretaceous early tertiary tectonic evolution of the cebs the observed evolution of subsidence depocentres and areas of uplift for the cebs during this time span has been reconstructed the results are in agreement with previous studies which have related the large scale late cretaceous early tertiary inversion within the cebs to long wavelength intra plate compressive stresses exerted mainly by the alpine thrust the models show that lateral heterogeneities have to be considered in order to model more local features such as the observed differential response of adjacent areas to the large scale stress regime this indicates that both intra plate tectonic forces and rheological structural contrasts must be taken into account to reconcile the style of intra plate deformation and to model the evolution through time of complex basin systems

tectonic evolution of the mid polish trough modelling implications and significance for central european geology abstract the polish basin forms the easternmost part of the permian mesozoic northwest european basin the depocentral axis of the polish basin the mid polish trough mpt is superimposed on the boundary between the west european phanerozoic and east european proterozoic crustal domains within the trans european suture zone the presence of this fundamental crustal boundary may be paramount in structurally controlling the position of the mpt concentrating stresses during post variscan wrench and extensional tectonics in central europe tectonic subsidence analysis of the preserved and reconstructed stratigraphic record of the polish basin indicates the occurrence of an initial late permian early triassic 255 241 ma rifting phase that was followed by subsequent episodes of increased tectonic subsidence during the oxfordian kimmeridgian 157 152 ma and beginning in the cenomanian 97 ma the oxfordian kimmeridgian episode is interpreted as corresponding to a second extensional event which correlated with intersified rifting and wrench activity within the arctic north atlantic rift system and along the northern tethyan margin while the cenomanian may be considered a precursor of compressional deformations in the basin which culminated in basin inversion in the latest cretaceous and paleocene forward modelling results in view of existing geophysical interpretations which show the presence of a deep moho and a very velocity lower crustal layer beneath thempt suggest that permo mesozoic basic development may be related at least in part to the intrusion of mantle material into and densification of the lower crust rather than exclusively to crustal extension and thinning

the late rhaetian transgression in southern sweden regional and global recognition and relation to the triassic jurassic boundary palynological investigations of rhaetian outcrops and drillcores in combination with subsurface data from wells in scania southern sweden have revealed the presence of marine dinoflagellate cysts in sedimentary strata that were previously considered to have been deposited in a mainly terrestrial environment two distinct dinocyst events are identified one older event where persistent rare to common occurrences of rhaetogonyaulax rhaetica and lunnomidinium scaniense indicates deposition in shallow marine and marginal marine environments this lunnomidinium interval is preceded and succeeded by assemblages with rare to common r rhaetica and can be correlated with the mid to late rhaetian r rhaetica zone it is associated with spore pollen assemblages of the mid rhaetian rhaetipollis limbosporites zone the younger event the r rhaetica maximum interval is characterised by mass occurrence of r rhaetica with less common or absent dapcodinium priscum in association with a dark grey to black mudstone shale the introduction of d priscum in association with the over whelming abundance of r rhaetica allows correlation with the transition between the r rhaetica zone and the succeeding d priscum zone and signals fully marine conditions the r rhaetica maximum interval is associated with spore pollen assemblages of the late rhaetian ricciisporites polypodiisporites zone and is in sweden succeeded both lithostratigraphically and palynostratigraphically by the t j transition the r rhaetica maximum interval corresponds to a late rhaetian maximum flooding event that took place in a shallow gently sloping embayment that covered the danish basin area during the late triassic early jurassic this maximum flooding event can be recognised in late rhaetian strata from different parts of the northern hemisphere it is an important temporal constraint on the t j boundary as it is associated with the disappearance of triassic marine faunas appears to coincide with the onset of the main pulse of camp volcanism immediately precedes the initial carbon isotope excursion and the global sea level drop that characterises the t j transition

a new late cretaceous to present apwp for asia and its implications for paleomagnetic shallow inclinations in central asia and cenozoic eurasian plate deformation based on a compilation of 533 cretaceous to present day palaeomagnetic poles obtained from both sedimentary and igneous rocks we present a new analysis of the so called asian inclination anomaly and demonstrated the anomaly to be twofold a 2nd order anomaly characterized by high palaeolatitudes in indochina and low palaeolatitudes over tibet and central asia is superimposed on a 1st order anomaly characterized by cenozoic low palaeolatitudes found all over northeastern asian stable blocks the analysis herein convincingly shows that the europe apparent polar wandering path apwp can no longer be used to interpret palaeomagnetic data east of the urals including interpretation of asian tertiary deformation related to the india asia collision we thus construct a new apwp for east asia based on palaeopoles from blocks assumed to be stable this new apwp is consistent with and reinforces previous analyses of asian tectonics such as the age 55 ma and locus 5 10 n of the indo asian collision the lateral extrusion of se asian continental blocks and the intracontinental shortening in central asia possible origins of the 1st order palaeolatitude anomaly are 1 a geomagnetic origin due to long lasting non dipolar contribution to the magnetic field and 2 a tectonic hypothesis in which a newly defined east asia plate was located 10 farther south than expected from the current europe apwp based on a set of six new reconstructions from 90 ma to present we show that our tectonic model reconciles geophysical geological and tectonic observations throughout eurasia from siberia to europe including kinematics in the arctic ocean up to northwestern arctic alaska beyond possible occurrences of non dipolar field contribution and or local inclination flattening in the sedimentary data our model leads us to conclude that cenozoic tectonics is the dominant contributor to the observed 1st order 10 low palaeolatitude anomaly over asia during the tertiary

structural analysis clay mineralogy and k ar dating of fault gouges from centovalli line central alps for reconstruction of their recent activity abstract between the cities of domodossola and locarno the complex centovalli line tectonic zone of the central alps outlines deformation phases over a long period of time probably starting 30 ma ago and under variable p t conditions the last deformation phases developed gouge bearing faults with a general e w trend that crosscuts the roots of the alpine canavese zone and the finero ultramafic body kinematic indicators show that the general motion was mainly dextral associated with back thrusting towards the s the on the basis of the k ar ages and with a thermal gradient of 25 30 c km the studied fault zones were located at a depth of 4 7 km if they were active until now as observed in field the exhumation was approximately 2 5 3 0 km for the last 12 ma with a mean velocity of 0 4 mm y comparison with available models on the recent alpine evolution shows that the tectonic activity in the area relates to a continuum of the back thrusting movements of the canavese line and or to several late extensional phases of the rhone simplon line the centovalli val vigezzo zone therefore represents a major tectonic zone of the central western alps resulting from different interacting tectonic events

magnetic anomaly interpretation across the southern central andes 32 34 s the role of the juan fernandez ridge in the late tertiary evolution of the margin marine and terrestrial magnetic surveys have been integrated to study the tectonic structure of the convergent margin of chile between 32 34 s three magnetic domains have been identified oceanic continental margin and subaerial the oceanic domain has seafloor spreading anomalies 16 37 ma to 18 39 5 ma disturbed by anomalies of the juan fernandez hot spot chain in the continental margin the most prominent fabric are e w anomalies in the upper slope corresponding to onshore e w anomalies of large intrusive bodies onshore a n s lineament of short wavelength anomalies defines the roots of a cretaceous volcanic arc a resembling lineament offshore indicates a submerged older volcanic arc and that continental basement extends to 50 km landward of the trench absolute cenozoic plate motion for nazca and south american plates and dating of the juan fernandez chain provide a kinematic model of ridge continent collision the reconstruction indicates rapid southward migration of the collision point along 1400 km of the margin from 20 to 11 ma 20 cm yr 1 from 11 ma to present the collison point has migrated at a slower rate along 375 km of the margin 3 5 cm yr 1 the predicted location of the subducted portion of the juan fernandez chain coincides with the south edge of the southward migrating flat slab segment of the subducted lithosphere and with a cluster of deep earthquakes indicating a causal relationship in the last 10 myr the ridge has separated a sediment starved trench to the north where subduction erosion may dominate from a sediment filled trench to the south where recent sediment accretion dominates these observations indicate that subduction of the juan fernandez chain plays a major role in arc forearc tectonics

unraveling 1 5 ga of brittle deformation history in the laxemar simpevarp area southeast sweden a contribution to the swedish site investigation study for the disposal of highly radioactive nuclear waste 1 the swedish nuclear fuel and waste management company skb is undertaking site investigation at two locations in sweden forsmark and laxemar simpevarp with the aim of identifying a suitable area for the construction of a deep repository for the disposal of highly radioactive nuclear waste fault slip data from outcrops and oriented drill cores were used to compute paleostress states and to unravel the sites brittle deformation history results from the laxemar simpevarp area show that its suggested brittle history results from multiple reactivation of fracture and fault sets caused by the many orogenic episodes that affected the region during at least 1 5 ga of geological evolution in the brittle deformational regime two compressional approximately nw nnw se sse and nne ssw oriented shortening events generated sets of conjugate steep strike slip fractures these sets formed during the late stages of the svecokarelian and possibly also of the gothian orogeny soon after the region entered the brittle deformation domain the mesoproterozoic sveconorwegian orogeny generated fractures and faults that are assigned to a third set of conjugate strike slip faults which constrain an approximately e w 1 the caledonian shortening oriented approximately nw se to e w reactivated the latter but also formed a new similarly oriented set of subvertical strike slip fractures permian transtension was oriented nw sw and caused a prominent set of moderately dipping nw se trending normal faults in the precambrian basement of the study area two other approximately nw sw and nw se oriented shortening events are recorded in ordovician limestones and can be tentatively linked to the far field effects of the laramide and alpine orogenies

tectonic analysis and paleo stress determination of the upper lava section at odp iodp site 1256 east pacific ocean abstract research on the deep sea is of great importance for a better understanding of the mechanism of magma emplacement and the tectonic evolution of oceanic crust however details of the internal structure in the upper levels of the oceanic crust are much less complete than that of the more fully studied sub aerial areas for the first time this study proposes a dynamic analysis using the inversion method on core data derived from the drilled basement of the present day intact oceanic crust at odp iodp site 1256 in the cocos plate the research is based on an innovative core reorientation process and combines different stress hypothesis approaches for the analysis of heterogeneous failure slip data via exploitation of two distinct techniques from the analysis of the failure slip data both techniques produce 5 distinct subsystem datasets all calculated subsystems are mechanically and geometrically admissible interpretation of the results allows the researchers to note a complex local and regional tectonic evolution deriving from the interplay of 1 the ridge push and rotation of both the east pacific rise and the cocos nazca spreading center 2 the effect of the slab pull of the middle america trench 3 the influence of lava emplacement mechanisms and 4 intra plate deformation

the jurassic cretaceous transition of the fararp 1 core southern sweden sedimentological and phytological indications of climate change the 116m deep fararp 1 core drilled in the vomb trough in southernmost sweden is dated by integrated terrestrial and marine palynostratigraphy the lower part of the succession ca 84 m encompasses uppermost jurassic to lowermost cretaceous uppermost tithonian to valanginian strata an unconformity separates the valanginian strata from an overlying ca 1 m thick interval of upper albian to cenomanian arnager greensand formation the uppermost part of the core is a repetitive succession of lowermost cretaceous sediments during the jurassic cretaceous u k transition nw europe was located in mid latitudes and comprised an archipelago of large and small islands separated by deeper grabens and epicontinental seaways that connected the boreal sea to the north with the warmer tethys ocean to the south boundary strata in england france the netherlands and germany are characterised by relatively prominent climatic change from arid semi arid to subhumid humid conditions southernmost sweden was located on the margin of a large landmass comprising most of the fennoscandian shield bordering a large epicontinental sea to the west by combining sedimentology clay mineralogy and palynofacies the tithonian to valanginian cored succession of the fararp 1 core provides complementary information on how marginal deposits from the eastern part of the epicontinental sea reflect the climatological and environmental changes observed in other parts of nw europe the fararp 1 core shows that during the tithonian to earliest berriasian deposition took place in a terrestrial but near marine depositional setting in coastal lakes or lagoons with little marine influence a dry climatic regime favoured stagnant water conditions with common algal blooms of primarily bonyococcus and zygnemataceae palynofacies and sedimentology indicate limited transport of freshwater and material to the basin the stagnant depositional environment was terminated by a marine flooding in the early berriasian during the remaining berriasian and the early valanginian conditions shifted between near marine and marine settings in a dynamic coastal environment similar to contemporaneous assemblages reported from the danish island of bornholm a shift in clay mineralogy from a dominance of 10 a minerals to increasing amounts of mixed layer and kaolinite indicates a change to more humid conditions in the latest tithonian cheirolepidacean pollen classopollis are present but never common in the cored succession and a similar conspicuous decrease of these pollen as previously reported from england germany and france is not evident in the fararp 1 core instead a subsequent shift in both palynofacies and palynoflora marked by an increase in abundance of heavy terrigenous material i e wood and coal particles upland pollen grains and reworked palynomorphs is also observed in the uppermost tithonian lowermost berriasian interval at the same level spores and pollen classified as warmer drier elements decrease in abundance this is interpreted as representing a shift to more humid climatic conditions with increased runoff from the hinterland thus the combined sedimentological and palynological data from the fararp 1 core suggest that climatic conditions in the area changed from more seasonally dry semi arid to more humid semi humid across the j k boundary latest tithonian to earliest berriasian and hence earlier than the mid berriasian climatic shift recorded from e g england and the netherlands c 2011 elsevier b v all rights reserved less

plate margin paleostress variations and intracontinental deformations in the evolution of the cuddapah basin through proterozoic abstract the sedimentary basins are often influenced by adjoining mobile belts as is the case of the proterozoic cuddapah basin in southern india lying in proximity of the eastern ghats granulite belt egb and the southern granulite terrain sgt two major faults gani kalva and kona faults in the western part of the cuddapah basin have been examined in this work to comment on the changes in paleostress conditions affecting the basin evolution punctuated by several stages of extensional and compressional regimes in the time interval 1 9 0 5 ga the tensor solutions were obtained for the mesoscale faults and fault striae using the improved right dihedron method followed by the rotational optimization method tensor delvaux and sperner 2003 combining the paleostress field reconstruction and other structural stratigraphic attributes we propose a possible scenario of punctuated evolution of the cuddapah basin and its inversion the stress regimes are tentatively correlated with multiple stages of basin opening and deformation of basin in fill representing the pre grenvillian through the pan african orogeny the paleostress conditions derived from various stratigraphic horizons provide an opportunity to comment on the changes in tectonic stresses including several stages of extensional and compressive regimes in the cuddapah basin the tensor solutions were obtained for the mesoscale faults and fault striae in the neighborhood of above two fault lines using the improved right dihedron method followed by the rotational optimization method tensor delvaux and sperner 2003 the most prominent stress states recorded around the two fault lines can be classified into those affecting 1 the paleoproterozoic lower cuddapah successions 2 the younger kurnool group and 3 both the groups integrating the stress states of the fault slip analysis obtained from different unconformity bounded rock groups of lower cuddapah and other geologic data we suggest extensional to transtensive pure strike slip regime to be active during the first phase of basin opening and c 1 89 ga mafic igneous activity late compressional to transpressive pure strike slip regimes are well recorded from the younger kurnool group representing late neoproterozoic deformations the tensor solutions from different unconformity bound stratigraphic horizons constrain different states of deformation we relate the extensional to transtensive pure strike slip regimes from lower cuddapah successions to the ongoing basin opening events and the associated palaeoproterozoic igneous activities the late neoproterozoic to early paleozoic compressional to transpressive strike slip regime present the possible effects of compressional activities happening around the cratonic margin the present analysis lends further support to the idea that estimation of paleostress states from fault slip data even in regions of relatively weak deformation in continental interior are important while assessing influence of plate margin stresses on the continental interior

implications for mechanical properties of brittle faults from observations of the punchbowl fault zone california field observations of the punchbowl fault zone an inactive trace of the san andreas are integrated with results from experimental deformation of naturally deformed punchbowl fault rocks for a qualitative description of the mechanical properties of the fault and additional information for conceptual models of crustal faulting the punchbowl fault zone consists of a single continuous gouge layer bounded by zones of extensively damaged host rock fault displacements were not only localized to the gouge layer but also to discrete shear surfaces within the gouge deformation in the exposure studied probably occurred at depths of 2 to 4 km and was dominated by cataclastic mechanisms textural data also suggest that significant amounts of pore fluids were present during faulting and that fluid assisted mechanisms such as dissolution diffusion and precipitation were operative the experimental data on specimens collected from the fault zone suggest that there is a gradual decrease in strength and elastic modulus and an increase in relative ductility and permeability toward the main gouge zone the gouge layer has fairly uniform mechanical properites and it has significantly lower strength elastic modulus and permeability than both the damaged and the undeformed host rock for the punchbowl fault and possibly other brittle faults the variations in loading of the gouge zone with time are primarily governed by the morphology of the fault and the mechanical properties of the damaged host rock in addition the damaged zone acts as the permeable unit of the fault zone and surrounding rock it appears that the gouge primarily governs whether displacements are localized and it therefore may have a significant influence on the mode of slip

thermochronological constraints on the multiphase exhumation history of the ivrea verbano zone of the southern alps abstract the ivrea verbano zone of the western southern alps nw italy exposes a well preserved tilted section across the lower continental crust making it a key region for studying deep crustal and exhumation processes this paper refines the cooling and exhumation history of the ivrea verbano zone using k ar dating of mica and illite rich fault gouges as well as zircon fission track and u th he thermochronology the adjacent strona ceneri zone sesia lanzo zone and lower penninic nappes are included in the study to derive a broader picture of the low temperature history of the area in the strona profile of the ivrea verbano unit the biotite k ar zircon fission track and u th he geochronometers show well preserved but unusually wide partial retention zones the youngest ages representing the formerly deepest position are situated along the insubric line the main foliation of the ivrea verbano zone is vertical the exhumation of the ivrea verbano zone which section has a horizontal position on the surface now took place in three steps during jurassic time the ivrea verbano zone was exhumed to a shallow to mid crustal position by continental scale extension in this displacement the pogallo line probably played a dominant role the studied section occupied an oblique position with a calculated angle of ca 15 to 23 in the jurassic later the ivrea verbano zone experienced a minor cooling event in the late eocene 38 ma zircon fission track ages that was probably related to thrusting and erosion the final exhumation towards the surface took place in the mid miocene as documented by the ca 14 ma zircon u th he ages and a 12 8 ma k ar fault gouge age the magnitude and the high rate of final exhumation suggest orogen parallel extension as a driving force which is widespread in the alps in the lower to middle miocene and is most probably connected to orogenic collapse

paleomagnetism and u pb zircon geochronology of lower cretaceous lava flows from the western lhasa terrane new constraints on the india asia collision process and intracontinental deformation within asia to better understand the india asia collisional process and intracontinental deformation within asia a paleomagnetic study has been conducted on the qushenla formation lava flows dated at 132 120 ma from the yanhu area in the western lhasa terrane stepwise thermal demagnetization isolates stable characteristic remanent magnetizations which include dual polarity and pass fold tests at a 99 confidence level indicating primary magnetizations the tilt corrected site mean direction for 51 sites is d 28 2 i 34 5 and k 74 3 with 95 2 3 corresponding to a paleopole at 61 4 n 192 9 e a95 2 1 our new paleomagnetic data combined with previous cretaceous volcanic paleomagnetic data from the lhasa terrane show that the precollisional southern margin of asia was at 16 8 n with a relatively e w alignment and that the lhasa terrane did not experience significantly discrepant north south movement although local vertical axis rotations did take place after the cretaceous comparison with the apparent polar wander paths apwps of india and the cretaceous paleocene paleopoles of the tethyan himalaya shows that the india asia collision was at 54 3 ma and the greater india during the paleocene had a large northern extent of 2000 km 18 1 beyond its present northern margin comparison with the cretaceous eurasian apwp indicates that a latitudinal convergence of 1000 km has taken place between the lhasa terrane and eurasia since the india asia collision the amount of north south shortening deduced from cretaceous paleomagnetic data is consistent with that accommodated by the cenozoic fold and thrust belts between the lhasa terrane and the hexi corridor

structure and tectonic evolution of the tornquist zone and adjacent sedimentary basins in scania and the southern baltic sea area abstract southernmost sweden bornholm and the surrounding baltic sea region are located on a large scale releasing bend in the dextral strike slip system of the tornquist zone with its resulting pull apart basins the well constrained geology of scania and bornholm has been combined with detailed on and offshore borehole data and three proprietary marine seismic surveys this in conjunction with supplementary babel deep seismic reflection findings allows a combined 3d interpretation of sediment structure interactions as a result a regional interpretation has emerged which gives a new understanding of the interplay between structural movement on a complex strike slip fault system tornquist zone and its intrazonal depressions vomb trough and colonus shale trough as well as the sedimentation history of associated areas of sediment accumulation ronne and arnager grabens hollviken halfgraben hano bay basin and skurup platform detailed sequential litho and seismo stratigraphic descriptions have been possible by combination of the various data sets this resulted in the clarification or recognition of previously unknown structural limits to sub basins and highs in the study area a 3d chronological 4d model for the development of the region is proposed this model takes into account the long lived structural history combining elements of strike slip extension and inversion tectonics the deep seated faulting controlling these structures is integrated with the deep structure as revealed by the babel line in this area

the las chacras potrerillos batholith pampean ranges argentina structural evidences emplacement and timing of the intrusion within the southern part of the sierra pampeanas the sierra de san luis argentina a series of extensive intrusive bodies are regarded to post date the famatinian cycle but were emplaced during the achalian a period of heterogeneous deformation along crustal scale fault zones the largest of those is the las chacras potrerillos batholith that is situated at the northern end of the transpressive sinistral guzman shear zone this composite pluton exhibits three sub domains that comprise two granitoid sub units each the southern potrerillos stock muscovite bearing red granite and biotite bearing red granite and the central biotite porphyritic granite and giant porphyritic granite and northern domain equigranular granite and porphyritic granite of the las chacras stock the crystallisation ages of the biotite porphyritic granite is around 381 ma u pb on zircons and pb pb on sphene while the host rock was already cooled below 350 c at 420 ma thermal modelling approaches favour a pulsed intrusion with a duration of 1 5 ma the emplacement was followed by rapid cooling below the muscovite cooling temperature biotite cooling ages in different sub units reflect either a long lasting cooling history of approximately 30 ma which is supported by the modelling or a reheating effect at around 350 ma devonian age determinations on the fault rocks and granitoids point to a syn tectonic emplacement of the batholith the pluton is interpreted to be positioned at the crossover of sinistral shear zones the origin of this nne directed extensional setting in a transpressive regime seems to be related to the transfer of displacement along a secondary set of nnw trending sinistral faults the final emplacement is due to a subsequent ballooning of the batholith following the direction of space creation this model is based on the relative timing of the emplacement sequence and macroscopically visible planar fabrics in the field as well as magnetic fabric data our results indicate that the emplacement is syn kinematic with respect to the achalian deformation event

the tectonic significance of k ar illite fine fraction ages from the san luis formation eastern sierras pampeanas argentina the sierra de san luis forms the southern tip of the eastern sierras pampeanas in central argentina two narrow belts of low grade phyllites and quartz arenites i e the san luis formation have accommodated part of the strain related differential exhumation of the medium to high grade metamorphic domains that constitute to the basement complex of the sierra eleven phyllite samples were subjected to the k ar fine fraction dating technique results are interpreted in relation to the kubler index of the illites which indicate epimetamorphic conditions for the majority of the samples obtained ages between 330 and 290 ma cover a period of compressional tectonics in the late mississippian visean serpukhovian boundary followed by the subsidence during the formation of the paganzo basin in the provinces of la rioja and san luis these tectonic movements are coincident with the toco orogeny in northern chile and southern bolivia this suggests that the older k ar ages document the compressional stage and that younger ages record the cooling of the basement during the subsequent extensional uplift of the basement

keys and pitfalls in mesoscale fault analysis and paleostress reconstructions the use of angelier s methods whereas most of the stress inversion methods using fault slip data only minimize the angle between the measured striation and a computed shear stress to find the best fitting reduced stress tensor angelier 1990 proposed an alternative method named invd that also takes into account the relative shear stress magnitude which allows the fault to move using artificial datasets and particular fault geometries we compare this method with one of the classical methods based on the minimization of the shear slip angles r4dt angelier 1984 and we show that in most cases the new method has improved the quality of the results furthermore as proposed by angelier we point out that the quality of the stress inversion primarily depends on the quality of the field data we give advice and warn about some pitfalls concerning determination of sense of slip on fault planes recognition of successive faulting events and their chronology drawer or wedge faults stress permutations faults in vertical bedding we also argue that in case of tilted sequences fault diagrams should not be presented without bedding planes but we show that stress inversions when realized with caution and with the correct method can havemuch more applications than reconstructing stress fields like for determining the paleo horizontal the nature and the sense of motion of large faults the chronology and age of large structures

deep structure of the earth s crust in the contact zone of the palaeozoic and precambrian platforms in poland tornquist teisseyre zone abstract one of the major tectonic problems in europe concerns the southwest margin of the east european platform in the region of the so called polish danish trough in general this margin is assumed to be the tornquist teisseyre t t line running approximately from northwest to southeast in this part of europe determination of deep crustal structure of the contact zone between the precambrian platform and the palaeozoic platform was the main aim of the deep seismic sounding dss programme in poland in 1965 1982 deep seismic soundings of the earth s crust have been made in the t t line zone along nine profiles with a total length of about 2600 km the results of deep seismic soundings have shown that the crust in the marginal zone of the east european platform has highly anomalous properties the width of this zone ranges from 50 km in northwest poland to about 90 km in southeast poland the crustal thickness of the palaeozoic platform in poland is 30 35 km and of the precambrian platform 42 47 km while in the t t tectonic zone it varies from 50 to 55 km above the moho boundary in the t t zone at a depth of 40 45 km there is a seismic discontinuity with p wave velocities of 7 5 7 7 km s boundary velocities mean velocities and stratification of the earth s crust vary distinctly along the t t zone there are also observed high gravimetric and magnetic anomalies in the t t zone the t t tectonic zone determined in this manner is a deep tectonic trough with rift properties the deep fractures delineating the t t tectonic zone are of fundamental importance for the localization of the plate edge of the precambrian platform of eastern europe in the light of dss results the northeastern margin of the t t tectonic zone is a former plate boundary of the east european platform