geophysical geological transect and tectonic evolution of the swiss italian alps a complete alpine cross section integrates numerous seismic reflection and refraction profiles across and along strike with published and new field data the deepest parts of the profile are constrained by geophysical data only while structural features at intermediate levels are largely depicted according to the results of three dimensional models making use of seismic and field geological data the geometry of the highest structural levels is constrained by classical along strike projections of field data parallel to the pronounced easterly axial dip of all tectonic units because the transect is placed close to the western erosional margin of the austroalpine nappes of the eastern alps it contains all the major tectonic units of the alps a model for the tectonic evolution along the transect is proposed in the form of scaled and area balanced profile sketches shortening within the austroalpine nappes is testimony of a separate cretaceous age orogenic event west directed thrusting in these units is related to westward propagation of a thrust wedge resulting from continental collision along the meliata hallstatt ocean further to the east considerable amounts of oceanic and continental crustal material were subducted during tertiary orogeny which involved some 500 km of n s convergence between europe and apulia consequently only a very small percentage of this crustal material is preserved within the nappes depicted in the transect postcollisional shortening is characterized by the simultaneous activity of gently dipping north directed detachments and steeply inclined south directed detachments both detachments nucleating at the interface between lower and upper crust large scale wedging of the adriatic or apulian lower crust into a gap opening between the subduced european lower crust and the pile of thin upper crustal flakes alpine nappes indicates a relatively strong lower crust and detachment between upper and lower crust

palinspastic reconstruction and topographic evolution of the eastern alps during late tertiary tectonic extrusion this paper presents a new palinspastic restoration of the eastern alps for neogene time and an attempt to reconstruct the neogene palaeogeology palaeotopography and palaeohydrography in connection with the structural evolution the eastern alps underwent radical horizontal displacement during the neogene due to large strike slip systems and formation of structural windows our palinspastic reconstruction considers a the rearrangement of tectonic units dismembered during tectonic extrusion b the tectonic denudation driven by displacement of the crystalline blocks c geochronological arguments and d the sedimentary record of the syn extrusion basins the rearrangement of tectonic blocks results in a remarkably good fit of highly dismembered zones both in crystalline and sedimentary areas and shows the pre miocene unstretched pattern of the eastern alps reduced to 65 of its present day e w elongation using this structural frame and considering the sedimentary record a set of palaeogeologic and palaeotopographic sketch maps with the palaeo river systems is presented for three time slices pre syn and post extension situation in late oligocene and early miocene times the western eastern alps were already mountainous whereas the eastern part of the orogen formed lowlands or hilly areas enhanced block movement in the course of the extrusion process around the early middle miocene boundary led to the formation of intramontane sedimentary basins and a fault induced reorientation of the drainage pattern which forms the basis of the modern river system in the area east of the tauern window this region where pre miocene land surfaces are preserved probably became a mountainous area not before late miocene time and never reached the elevations of the areas further west

formation subduction and exhumation of penninic oceanic crust in the eastern alps time constraints from 40ar 39ar geochronology abstract new 40ar 39ar geochronology places time constraints on several stages of the evolution of the penninic realm in the eastern alps a 186 2 ma age for seafloor hydrothermal metamorphic biotite from the reckner ophiolite complex of the pennine austroalpine transition suggests that penninic ocean spreading occurred in the eastern alps as early as the toarcian late early jurassic a 57 3 ma amphibole from the penninic subduction accretion rechnitz complex dates high pressure metamorphism and records a snapshot in the evolution of the penninic accretionary wedge high pressure amphibole phengite and phengite paragonite mixtures from the penninic eclogite zone of the tauern window document exhumation through 15 kbar and 500 c at 42 ma to 10 kbar and 400 c at 39 ma the tauern eclogite zone pressure temperature path shows isothermal decompression at mantle depths and rapid cooling in the crust suggesting rapid exhumation assuming exhumation rates slower or equal to high pressure ultrahigh pressure terrains in the western alps tauern eclogite zone peak pressures were reached not long before our high pressure amphibole age probably at 45 ma in accordance with dates from the western alps a late stage thermal overprint common to the entire penninic thrust system occurred within the tauern eclogite zone rocks at 35 ma the high pressure peak and switch from burial to exhumation of the tauern eclogite zone is likely to date slab breakoff in the alpine orogen this is in contrast to the long lasting and foreland propagating franciscan style subduction accretion processes that are recorded in the rechnitz complex

the arcs of the western alps and the northern apennines an updated view abstract the arcs of the western alps and the northern apennines and the link between them are in the process of being investigated using the european geotraverse and they have historically been interpreted in many different ways new information particularly geophysical further constrains possible models both arcs have evolved in several stages sometimes complexly interrelated and sometimes independent of each other compressional belts produced in these stages have either been of the push arc type indentation into a deformable mass or the pull arc type backward migration of hinge of a subduction zone leading to small extensional basins known as back arc basins and pores with an arcuate mountain range on the subduction side extensional periods with the possible formation of pull arcs in the alps comprise the gosau period between the eo and meso alpine push arc phases and the oligocene lull period between the meso and the neo alpine push arc phases in the northern apennines remainders of the meso alpine nappes were involved in oligocene early miocene pull arc formation associated with spreading in the balearic sea followed by push arc formation particularly in the middle miocene and by renewed pull arc formation from the latest late miocene to the present during all of these developments the moho was modified by such processes as lithospheric stretching asthenospheric intrusions subhorizontal shearing and isostatic uplift the present moho configuration is consequently a collage of moho patches formed at different intervals both push and pull arcs are laterally bounded by complementary strike slip or transform zones these too were modified in the course of history and their final geometry is consequently of a very complex nature in the alps for instance the insubric fault zone appears to have been the main dextral transform fault of the neogene push arc until it was sinistrally kinked by the giudicarie fault zone and probably deactivated dextral transpression being briefly transferred to the en echelon brachyanticlines of the late alpine windows in the case of the oligocene apennines the sinistral rotations of corsica and sardinia otherwise hard to understand may be attributed in part to sinistral transform motions along the eastern border zone of the oligocene early miocene balearic extension

subsidence analysis and quantitative basin modelling in the styrian basin pannonian basin system austria abstract we present the results of subsidence analysis and of quantitative basin modelling using isostatical and flexural models for basin evolution along four cross sections in the styrian basin the westernmost subbasin of the pannonian basin system subsidence analysis reveals a first ottnangian karpatian synrift phase our local isostatic models predict crustal stretching values up to 1 3 and subcrustal stretching values of 1 6 for this event stretching factors of a minor sarmatian extension phase are below 1 04 the termination of subsidence during the pannonian and a rapid quaternary uplift phase can be explained by major changes in the regional stress field a w e cross section through the northern furstenfeld subbasin provides a key for the understanding of the dynamics of basin formation it crosses a narrow karpatian rift basin the metamorphic core complex of the penninic eisenberg window and shows an eastward tilting of the easternmost part of the basin during pannonian times uplift of the penninic window can only be modelled with an extremely weak lithosphere equivalent elastic thickness eet 2 km whereas a best fit between observed and modelled tilting is obtained with an eet value of 5 km these results suggest that the lithosphere was extremely weak during the onset of basin evolution in ottnangian karpatian times probably caused by high extension rates and high heat flows associated with karpatian to early badenian magmatic activity subsequent cooling led to a pronounced increase in flexural rigidity an eet of 5 km fits well with estimations in other parts of the pannonian realm depth dependent rheology models based on palaeo heat flow estimates indicate a similar increase in lithospheric strength with time the impact of plio pleistocene volcanism on rheology appears to be relatively modest which can be explained by a deep position of the magma chamber for this event

lateral extrusion in the eastern alps part 1 boundary conditions and experiments scaled for gravity lateral extrusion encompasses extensional collapse gravitational spreading away from a topographic high in an orogenic belt and tectonic escape plane strain horizontal motion of wedges driven by forces applied to their boundaries in the eastern alps it resulted from 1 an overall northerly compression apulia against eurasia 2 a strong foreland bohemian massif 3 lack of constraint along a lateral boundary carpathian region and 4 a previously thickened gravitationally unstable thermally weakened crust eastern alpine orogenic belt six indentation experiments reproduce lateral extrusion at lithospheric scale the models have two to four lithospheric layers with a mohr coulomb rheology for the upper and a viscous rheology for the lower crust the lithosphere rests upon a low viscosity asthenosphere a broad indenter a narrow deformable area and a weakly constrained eastern margin fullfill as closely as possible conditions in the eastern alps indentation produces both thickening in front of the indenter and escape of triangular wedges lateral variations in crustal thickness become attenuated by gravitational spreading the overall fault pattern includes domains of reverse strike slip oblique normal and pure normal faults strike slip faults in conjugate sets develop serially the narrow width of the deformable area and the strength of the foreland determine the angles between the sets gravitational spreading produces a rhombohedral pattern of oblique and pure normal faults along the unconstrained margin opposite the unconstrained margin the indenter front shows thrusts and folds intersecting with the conjugate strike slip sets a triangular indenter favors spreading high velocity of indentation favors escape high confinement limits lateral motion inhibits spreading and favors thickening lateral extrusion in the eastern alps is best modeled by 1 a weak lateral confinement 2 a broad and straight indenter 3 a narrow width of the deformable area and 4 a rigid foreland crustal thickening lateral escape and gravitational spreading all contribute to the overall deformation

dating of fault zone activity by apatite fission track and apatite u th he thermochronometry a case study from the lavanttal fault system eastern alps introductionfaulting in the upper crust may leadto thermal anomalies caused by fric tional heating e g maddock 1983 dalessio et al 2003 and or in ltra tion of hydrothermal uids yamadaet al 2007 heating e ects are ex pected to be localised along faultzones and restricted to zones a fewcentimetres adjacent to the main faultsurface dalessio et al 2003 in this study we attempted to datethermal anomalies within fault zonesby comparison of cooling ages at thetransition from fault related rocks tothe undeformed host rocks for thispurpose we chose the lavanttal faultsystem due to underground excava tion and cored drillings related togeological site investigations for amajor railway project in austria it isone of the best exposed fault zones inthe eastern alps we used a combi nation of ssion track aft and u th he analysis on apatites thesensitivity intervals of these thermo chronometers are often referred to aspartial annealing and retention zones apaz heprz and range from 120to 60 c and 80 to 40 c respectively green et al 1986 wolf et al 1996 assuming holding times over geo logical time scales wagner 1979 ketcham et al 1999 the low temperature sensitivity of these ther mochronometers allows thermalanomalies along surfaces of fault slipor uid pathways to be detected forsuch applications however annealingand retention depend not only onheating temperature but also on heat ing duration laslett et al 1987 murakami et al 2006 a combina tion of forward and inverse modellingon apatite age track length and hedata allows quantitative analysis ofthe cooling behaviour of the hostrocks our new results underline theimportance of using multiple low temperature thermochronometersin elucidating details of the thermalhistory of a fault zone geological outlinethe nnw trending lavanttal faultsystem one of the major strike slipfaults in the eastern alps fig 1 separates the basement complexes ofthe kor and saualm by dextral o setof approximately 10 km reinecker 2000 it is assumed to have beenactive since early miocene times withpeaks in activity between 18 16 and14 12 ma reinecker 2000 as indi cated by the evolution of adjacentsedimentary basins and the regionalstructural framework e g pischingeret al 2008 near its southern termi nation the lavanttal fault o sets theperiadriatic fault by about 20 km despite some models at the scale ofthe eastern alps describing the gen eral evolution of con ning fault zonesduring miocene times e g peressonand decker 1997 frisch et al 1998 2000 neubauer et al 2000 littleremains known about the evolutionof the lavanttal fault system how ever these models include a relation ship between the lavanttal faultsystem and the uplift of the koralmcomplex neubauer and genser 1990 previous thermochronologicalstudies documented that the koralmcomplex was already near the surfaceduring the whole cenozoic period hejl 1997 the timing of its naluplift however is less constrained sample descriptionparts of the lavanttal fault system arecharacterised by cataclasites and faultgouges up to several tens of metresthick thermochronological analyseswere carried out on drill core samples diameter 10 cm taken during thegeological investigations for thekoralm railway tunnel drillingabstract

extension in compressional orogenic belts the eastern alps extension in the eastern alps encompasses the following 1 extension accompanying simple shear crustal stacking subhorizontal stretching occurs along flat lying foliations and regionally consistent stretching lineations with associated high strains on a local scale stretching results from extrusion of ductile sediments squeezed between rigid basement blocks basement blocks during thrust sheet imbrication the overall geometric effect is crustal thickening 2 classical extensional tectonics extension first occurs as a consequence of accretion and underthrusting of continental and oceanic material and represents gravitational adjustment of an unstable orogenic wedge extension then occurs as a consequence of terminal continental collision and is accommodated by lateral extrusion of crustal of crustal blocks the overall geometric effect is crustal thinning extension is generally oriented subparallel to the strike of the orogen

tectonics and sedimentation in the fohnsdorf seckau basin miocene austria from a pull apart basin to a half graben the miocene intramontane fohnsdorf seckau basin is situated at the junction of the sinistral mur murz fault system and the dextral pols lavanttal fault system the basin comprises a 2 400 m thick coal bearing fluviodeltaic lacustrine succession lower to middle miocene upper karpatian lower badenian which is overlain by a 1 000 m thick alluvio deltaic conglomeratic succession apfelberg formation middle upper badenian in the south a three stage model for the basin evolution has been reconstructed from structural analysis and basin fill geometries during a first pull apart phase subsidence occurred along ene trending sinistral strike slip faults of the mur murz fault system and ne sw to n s trending normal faults forming a composite pull apart basin between overstepping en echelon strike slip faults the seckau and fohnsdorf sub basins are considered as two adjacent pull aparts which merged into one basin during the second phase n s to nnw sse extension and normal faulting along the southern basin margin fault formed a half graben filled by wedge shaped alluvial strata apfelberg formation during the third phase after the end of basin sedimentation the dextral pols lavanttal fault system reshaped the western basin margin into a positive flower structure

contemporaneous plutonism and strike slip faulting a case study from the tonale fault zone north of the adamello pluton italian alps 1 a field microstructural and geochronological study of contemporaneous plutonism and strike slip faulting along the eastern tonale fault zone provides new insights into the interrelationships between magmatic emplacement contact metamorphism and shearing and it places new time constraints for the periadriatic fault system although pluton emplacement and shearing were not caused by each other they mutually interacted during contact metamorphism the character of the composite tonale fault zone varies considerably with its proximity to the northern margin of the adamello pluton from a paired greenschist facies mylonite belt northern mylonite zone and cataclastic fault zone in the west to a fault zone consisting of northern mylonite zone cataclastic fault zone and a second mylonite belt southern mylonite zone formed by contemporaneous shearing and contact metamorphism in the east ongoing strike slip motion led to telescoping and advective cooling of the deforming contact aureole new u pb zircon ages for the northernmost adamello intrusions the avio at 34 6 1 0 ma and the presanella at 32 0 2 3 ma date the onset of contact metamorphism rb sr and k ar cooling ages and new zircon fission track ages provide evidence that postintrusive cooling to below 300 c was achieved rapidly i e approximately 30 myr ago being consistent with a shallow crustal emplacement at ambient temperatures of approximately 250 c cataclastic dextral strike slip faulting continued until about 20 ma when the tonale fault zone became offset by a number of minor sinistral shears and by the giudicarie fault hence dextral strike slip motion along the periadriatic fault system east of the bergell pluton lasted from approximately 35 20 myr ago

exhumation in a convergent orogen the western tauern window unroofing of the western tauern window involved both low angle detachment faulting brenner fault and enhanced footwall erosion contemporaneous with upright antiformal folding this combination reflects orogen parallel e w extension during continued n s alpine convergence new fission track ages establish the relative chronology of folding and faulting and demonstrate that displacement was not always accommodated on the same surface during exhumation some units migrated from the footwall to the hanging wall of the main detachment fault due to the interplay between folding and faulting the region can effectively be divided into 3 distinct domains 1 the penninic units of the western tauern window were always in the footwall to the fault with maximum exhumation in the core of the dome due to folding and erosion 2 the lower austroalpine unit north of the tauern window was first part of the hanging wall to the brenner fault at a later stage this unit was exhumed by a further 4 5 km as part of the footwall to a more discrete through going fault the silltal fault 3 the middle and upper austroalpine units west of the tauern window were always within the hanging wall exhumation of the footwall from an initial depth of 25 km led to a transition in mechanical behaviour the curviplanar folded ductile shear zone marking the boundary to the tauern window was eventually transected by a more planar discrete brittle fault silltal fault with unit 2 now in the footwall along which the pre existing mylonites were passively exhumed to the surface

estimating displacement along the brenner fault and orogen parallel extension in the eastern alps the major structure accommodating orogen parallel extension in the eastern alps is inferred to be the brenner fault which forms the western boundary of the tauern window the estimated amount of extension along this fault varies from a minimum of 10 20 km to a maximum of 70 km all investigations that have attempted to constrain this amount of extension have calculated the fault plane parallel displacement required to restore the difference in structural level between footwall and hanging wall as constrained by geobarometry however these calculations neglected the component of exhumation of the footwall resulting from folding and erosion therefore the total amount of extensional displacement was systematically overestimated in the present study we project a tectonic marker surface from the footwall and hanging wall of the brenner fault onto a n s striking cross section this marker surface which is the base of the patscherkofel unit in the footwall and the base of the otztal basement in the hanging wall is inferred to have occupied the same structural level in the hanging wall and footwall of the brenner fault before its activity therefore the difference in height between the marker projected from the footwall and from the hanging wall is a measure of the vertical offset across the brenner fault this construction shows that the vertical offset of the marker horizon on both sides of the brenner fault varies strongly and continuously along strike of the brenner fault attaining a maximum value of 15 km at the hinge of the folded footwall tauern dome the along strike change of vertical offset is explained by large scale upright folding of the footwall that did not affect the hanging wall of the brenner fault therefore the difference in vertical offset of 10 km between the area of the brenner pass and the area immediately south of innsbruck corresponds to the shortening upright folding component of exhumation of the footwall the remaining 5 km of vertical offset must be attributed to extensional deformation the brenner fault itself is barely folded its dip varies between 20 and 70 and it crosscuts the upright folds of the western tauern window given the offset of 5 km the dip of the fault constrains the extensional displacement to be between 2 and 14 km we conclude that the tauern window was exhumed primarily by folding and erosion not by extensional unroofing

eoalpine and mesoalpine tectonics in the southern alps according to structural and stratigraphic data eoalpine and mesoalpine tectonics can be clearly recognized in the southern alps and distinguished from the better known neoalpine deformation

towards a mechanical model for the formation of the pannonian basin abstract new maps showing crustal and lithospheric thickness variations in the pannonian basin and the surrounding east alpine carpathian and dinaric mountains have been prepared on the basis of recent seismic seismologic and electromagnetic data a map presenting miocene faults of regional significance has been also constructed for the same region by using a wealth of recently available national and or more local studies it is suggested that observed crustal and lithospheric structural contrasts have been controlled primarily by neogene kinematic history of the region kinematic history is characterized by the following main patterns 1 1 indentation by adria and large scale backthrusting in the southern alps 2 2 eastward escape and extension of the eastern alps 3 3 extensional collapse in the pannonian basin area 4 4 formation of broad wrench fault systems along strike in the dinarides and southern carpathians and the western carpathians with dextral and sinistral shear respectively 5 5 compression and accretion of the external thrust and fold belt in the eastern carpathians these kinematic patterns are thought to be interrelated and all are manifestations of the late stage evolution of an overthickened orogenic wedge in order to arrive at a better understanding of the mechanism of extension which formed the pannonian basin deep crustal seismic profiles hydrocarbon exploration reflection lines and borehole data have been analyzed in the little hungarian plain this plain represents the transition zone between the alps and the pannonian lowlands and the results are illustrated by eight interpreted cross sections one result of regional importance is the clear recognition that the transdanubian central range at the southeastern flank of the little hungarian plain is composed of alpine pre senonian thrust sheets this finding marks the end of a century of debate the allochthony of the substrata of the pannonian basin can be now considered proven another result of more general interest is that these cross sections document the mode of lithospheric extension preexisting compressional detachment planes reactivate as low angle normal faults and lead to tectonic unroofing of deeply buried metamorphic terranes characterized by ductile flow along subhorizontal lineation

neogene quaternary structures in the border zone between alps dinarides and pannonian basin hrvatsko zagorje and karlovac basins croatia analysis of neogene quaternary structures from seismic lines surface measurements and geological mapping is presented from the border zone between the alps dinarides and pannonian basin first early miocene extension was possibly characterised by ene directed extension it was partly synchronous with nw se shortening second middle miocene extension was possibly characterised by nw se to wnw ese directed extension again this event was followed by a new generation of thrusts related to end sarmatian shortening the last late miocene e w to wnw ese directed extension was followed by a final shortening that created major map scale folds basement pop ups and inverted former basins geometry onlap and thickness patterns of the youngest syn tectonic basin fill indicate that this last n s to nw se directed shortening started in late pontian and continued up to the present time when taking into account the wider surrounding area it seems that the structures related to this latest shortening are arranged in often perpendicular directions centred at the eastern end of the periadriatic lineament to explain this fan like pattern of synchronous shortenings a kinematic model is proposed combining counter clockwise rotation with north or northwestward shift of the dinaridic block with respect to the more stable alpine buttress

fault and fracture control of fluid and diagenesis around the iberia salt dome iberia parish louisiana abstract recognition of the pathways that channel kilometer scale vertical fluid movements around salt domes is important to the understanding of petroleum migration and injection well disposal it is hypothesized that the vertical component of flow is accommodated by fractures faults porosity developed in the margin of the salt and through complexly interconnected sands by means of geochemical and petrographic techniques specific fluid migration pathways have been identified on the southwest flank of the iberia salt dome iberia parish louisiana brine samples from the iberia oil field have been analyzed by icp aes for dissolved na k mg ca sr ba mn fe cu pb zn al si and b the concentration data were contoured on a cross section developed from well logs to identify spatial correspondence between structures or sand bodies and compositional gradients of solutes within the pore fluids contour lines for ba b ca fe and sr deflect from sub parallel with formation dip to sub parallel with high angle faults this suggests that the faults either directly accommodate vertical fluid movement or serve to juxtapose permeable sands in sand mudstone successions thus forming vertical pathways of complexly interconnected sands sem eds inspection of well cuttings reveals the presence of diagenetic calcite pyrite vermiform kaolinite barite and sphalerite in pore spaces in some samples mineralization in dilated micro fractures reveals that fracture porosity also contributes to pore fluid movement in the iberia flank sediments thus faults and fractures contribute to vertical fluid flow and solute transport over a wide range of dimensional scales at the iberia salt dome

present day stress field and deformation in eastern austria we analysed fault plane solutions and borehole breakouts in the eastern part of the eastern alps and found a heterogeneous stress field which we interpret as a transition zone of three different stress provinces the western european stress province with nw to nnw sh orientation and mainly strike slip faulting regime the adriatic stress province with a radial stress pattern and thrust faulting to strike slip faulting regime and the dinaric pannonian stress province with ne sh orientation and strike slip faulting regime the western pannonian basin seems to be a part of the transition zone with wnw to nw sh orientation a stress regime stimulating strike slip faulting prevails in the eastern alps the south bohemian basement spur as a major tectonic structure with a high rheological contrast to surrounding units has a strong influence on the stress field and exhibits the highest seismicity at its tip due to stress concentration from a constructed vertical stress orientation profile we found stress decoupling of the northern calcareous alps from the underlying european foreland both the molasse and the flysch helvetic zone are considered as candidates for decoupling horizons due to stress orientation observations and due to their rheological behaviour from seismological and rheological data we suggest a horizontal stress decoupling across the eastern alps caused by a weakened central alpine lithosphere

post collisional orogen parallel large scale extension in the eastern alps abstract large scale extension affected the eastern alps during post collisional lateral tectonic extrusion in early and middle miocene times the tauern window was mainly tectonically exhumed by the 160 km pullapart of the rigidly behaving austroalpine basement blocks forming the tectonic lid of the penninic contents of the window an evaluation of the syn extrusion fault pattern reveals displacements of several tens of kilometers along the low angle extensional shear zones at the western and eastern margins of the window and along the important strike slip fault zones north and south of the window large scale shear is reflected by discontinuities in mineral cooling patterns across important shear zones the cooling histories of the tectonic blocks show that the window boundaries during exhumation coincide only partly with the classical boundaries of the window defined by thrust units reconstruction of the exhumation history shows an asymmetric evolution of the tauern window we argue that the eastern and western low angle extensional shear zones formed in sequence which is reflected by different evolutions of the fragmentation and uplift history of the austraolpine tectonic blocks to the east and west of the window in the central and eastern alps three structural domes the lepontin dome in the central alps and the tauern and rechnitz domes in the eastern alps were formed by large scale extension in miocene times total e w stretch amounts to more than 300 km and results in 70 extension we propose that the central and eastern alps are part of an extensional province that also includes the pannonian basin and has a counterpart separated by the moesian indenter in the rhodope mountains the aegean sea and the menderes massif in asia minor in these regions a number of mainly tectonically exhumed domes or deep sedimentary basins formed by miocene large scale extension

the neogene fohnsdorf basin basin formation and basin inversion during lateral extrusion in the eastern alps austria the evolution of the early middle miocene fohnsdorf basin has been studied using borehole data reflection seismic lines and vitrinite reflectance the basin is located along the sinistral mur murz fault system and probably formed as an asymmetric pull apart basin which was subsequently modified by halfgraben tectonics as a consequence of eastward lateral extrusion sedimentation started with the deposition of fluvio deltaic sediments thick coal accumulated in the northwestern basin thereafter subsidence rates increased dramatically with the formation of a lake several hundred meters deep the lake was filled mainly from the north with more than 1500 m of sediments showing a coarsening upward trend due to southward prograding deltaic lobes a sequence of more than 1000 m of boulder gravels blockschotter in the southeastern part of the basin are interpreted as the upper part of a coarse grained fan delta succession which accumulated along a normal fault along the southern basin margin fan deltas reached the central basin only during the early stages of sedimentation and during the late stages of basin formation miocene heat flow was approximately 65 70 mw m2 which is significantly lower than in other basins along the mur murz fault system the present day southwestern basin margin is a recent feature which is related to transpression along the dextral pols lavanttal fault system it is formed by reverse faults constituting the northeastern part of a flower structure miocene sediments in the feeberg valley are preserved along its southwestern part uplift of the central part of the flower structure was at least 2 4 km north south compression resulted in the deformation of the basin fill uplift of the e w trending basement ridge separating the fohnsdorf and seckau basins and in the erosion of 1750 m of sediments along the northern basin margin

are systematic variations in thrust belt style related to plate boundary processes the western alps versus the carpathians within the mediterranean region cenozoic deformation of the western alps and the west to east carpathians has resulted in two different styles of foreland fold and thrust belt the most prominent difference between the two belts is the presence carpathians or absence western alps of contemporaneous back arc extension but other important differences in structure topography and metamorphism also exist these differences in thrust belt style developed mainly during the final stages of thrust belt evolution and appear to reflect fundamental differences in the tectonic settings of the western alps and the carpathians in middle and late cenozoic time in particular they appear to be the result of convergence that is in the first case driven primarily by major plate motions and in the second case only by local motions of small lithospheric flakes or fragments we suggest that the structural styles developed in these two mountain belts may be useful in identifying mountain belts that have evolved in similar tectonic settings elsewhere in the world in this respect the western alps and the carpathians can be regarded as typical examples of two different styles of foreland fold and thrust belt or more properly as end member examples within a broad spectrum of foreland fold and thrust belt styles we propose that continental subduction zones and orogenic belts can be loosely divided into segments that show no major back arc extensional deformation adjacent to the belt the western alps and segments that exhibit back arc extension contemporaneously with thrusting the carpathians the former are found in areas where the rate of overall plate convergence exceeds the rate of subduction and are commonly typified by extensive involvement of crystalline basement in thrusting exposure of high grade metamorphic rocks at the surface high topographic elevation and large amounts of erosion tens of kilometers the latter are found in areas where the rate of subduction exceeds the rate of overall plate convergence and are commonly typified by thrust belts with little to no involvement of crystalline basement in thrusting low grade to no metamorphism low topographic elevation little erosion and in some instances an anomalously deep foredeep basin system

shape and origin of the east alpine slab constrained by the alpass teleseismic model abstract during the last two decades teleseismic studies yielded valuable information on the structure of the upper mantle below the alpine mediterranean area subducted oceanic lithosphere forms a broad anomaly resting on but not penetrating the 670 km discontinuity more shallow slabs imaged below the alpine arc are interpreted as subducted continental lower lithosphere substantial advances in our understanding of past and active tectonic processes have been achieved due to these results however important issues like the polarity of subduction under the eastern alps and the slab geometry at the transition to the pannonian realm are still under debate the alpass teleseismic experiment was designed to address these open questions teleseismic waveforms from 80 earthquakes recorded at 75 temporary and 79 permanent stations were collected during 2005 and 2006 from these data a tomographic image of the upper mantle was generated between 60 km and 500 km depth crustal corrections additional station terms and ray bending caused by the velocity perturbations were considered a steeply to vertically dipping shallow slab below the eastern alps is clearly resolved down to a depth of 250 km it is interpreted as european lower lithosphere detached from the crust and subducted during post collision convergence between adria and europe below the pannonian realm low velocities or high mantle temperatures prevail down to 300 km depth consistent with the concept of a pannonian lithospheric fragment which underwent strike slip deformation relative to the european plate and extension during the post collision phase of the alpine orogeny between 350 km and 400 km depth a deep slab extends from below the central eastern alps to under the pannonian realm it is interpreted as subducted lithosphere of the alpine tethys at greater depth there is a continuous transition to the high velocity anomaly above the 670 km discontinuity

coeval high pressure metamorphism thrusting strike slip and extensional shearing in the tauern window eastern alps 1 recent findings for a young 31 5 0 7 ma age of high pressure metamorphism at 90 km depths in the eclogite zone of the tauern window eastern alps prompt the question about the timing of the structural development of the tauern window and its relation to high pressure metamorphism we show that all major structures in the tauern window resulting from strong n s lithospheric shortening and simultaneous minor e w extension began developing coevally with high pressure metamorphism in the eclogite zone large scale strike slip shear zones started to form at 32 30 ma and facilitated the spatial accommodation of simultaneous shortening and extension at least some of the strike slip and extensional shear zones operated into the middle miocene either continuously or intermittently with pronounced activity at 21 15 ma the considerable exhumation of the eclogite zone from 90 km depths into the middle crust and the tectonic development of its framework occurred within only 1 2 ma after eclogitization this is evidenced by almost identical ages for eclogite facies metamorphism and for the development of the major structures that bound the eclogite zone under blueschist and greenschist facies metamorphic conditions we discuss a tectonic model in which considerable transpressional shortening and thickening took place in the present central southern part of the tauern window we propose that the tauern window nucleated here and that most of the regional deformation at 32 30 ma is today found at the periphery of the window and in the adjacent austroalpine units afterward transpression continued the window grew to the e w and n and deformation progressed to those parts of the window ductile deformation in the present day surface level ceased at 15 ma

balancing cross sections with kinematic constraints the dolomites northern italy balancing of structural cross sections is often hindered by a limited database or tectonic complications in such cases kinematic constraints may help to better constrain the construction of a cross section and its extrapolation to depth the kinematic implications of a known structure generally at the surface have to be considered for the unknown structure and for the internal consistency of a cross section a key point is the quantification of shortening of the known structure the extrapolation of this parameter allows balancing in an approximate way emphasizing major structures while minor structures are either neglected or treated in a simplified way with this approach a quick overview can be achieved on how much leeway for interpretation exists critical points for testing various working hypotheses become more evident and the trial and error effort during the construction of a balanced section is considerably shortened still the implications the observed structures have on the deeper crustal levels can be assessed this concept is applied to a section across the italian dolomites a brittle fold and thrust belt lacking reflection seismic data so far and thus with a poorly known deep structure still active south vergent alpine thrusting is oriented approximately perpendicular to previous dinaric thrusting the ramp flat style is dominant due to rheological constrasts within the stratigraphic sequence thanks to kinematic balancing based on surface data three alpine thrust systems could be identified each defining a thrust sheet with its particular basement unit and its sedimentary part superposition of the two more external basement units led to the presently observed high elevation of the triassic sequence in the dolomites shortening since late miocene times amounts to more than 50 km retrodeformation of alpine thrusting is a key for better understanding the previous dinaric structures and kinematics

footwall uplift in an orogenic wedge the tauern window in the eastern alps of europe abstract in the tauern window tw the deepest structural units of the eastern alps are exposed in a 30 160 km antiform european basement and cover occur under nappes of oceanic penninic units and continental origin austroalpine nappes the tertiary structural history of the tw is related to a rapid uplift of 20 30 km since oligocene times structural mapping revealed 1 detachment and folding of the cover units and stacking of orthogneiss sheets 2 constrictional folding of the entire duplex with amplitudes and half wavelengths of several kilometres 3 backthrusting and backfolding along the northern margin of the tw and 4 displacement along steep dip divergent strike slip faults the strain history is complex and related to all these deformation phases the most uniform structural element is a stretching parallel to the long axis of the tw and its major fold axes strain did not contribute to tw uplift because ductile n s shortening was compensated by e w extension restoration of the tw shows that the exposed structures are not sufficient to explain the tw uplift by analogy with the engadine window and the western alps where seismic data are available a deep seated duplex is suspected the tw uplift is best explained in a dextral transpressive regime

magnetotelluric and seismological determination of the lithosphere asthenosphere transition in central europe abstract we assembled all available magnetotelluric mt sounding curves that cover characteristic provinces of europe the depths of layers with increased electrical conductivities estimated from mt sounding curves by the respective authors were compared with a model of the lithosphere thickness derived from seismic p residuals regions of a relatively thin and thick lithosphere are characterized by positive and negative p residuals respectively we have found a good correspondence with both sets of results in the central part of the pannonian basin the depth of the lithosphere asthenosphere transition is estimated at 60 80 km and 100 120 km at the flanks the results for the bohemian massif show deeper levels of this transition between 100 and 200 km these depths seem to be typical of the lithosphere base beneath the variscan domain of central europe

modes of orogen parallel stretching and extensional exhumation in response to microplate indentation and roll back subduction tauern window eastern alps the tauern window exposes a paleogene nappe stack consisting of highly metamorphosed oceanic alpine tethys and continental distal european margin thrust sheets in the eastern part of this window this nappe stack eastern tauern subdome etd is bounded by a neogene system of shear the katschberg shear zone system kszs that accommodated orogen parallel stretching orogen normal shortening and exhumation with respect to the structurally overlying austroalpine units adriatic margin the kszs comprises a 5 km thick belt of retrograde mylonite the central segment of which is a southeast dipping low angle extensional shear zone with a brittle overprint katschberg normal fault knf at the northern and southern ends of this central segment the kszs loses its brittle overprint and swings around both corners of the etd to become subvertical dextral and sinistral strike slip faults the latter represent stretching faults whose displacements decrease westward to near zero the kinematic continuity of top east to top southeast ductile shearing along the central low angle extensional part of the kszs with strike slip shearing along its steep ends combined with maximum tectonic omission of nappes of the etd in the footwall of the knf indicates that north south shortening orogen parallel stretching and normal faulting were coeval stratigraphic and radiometric ages constrain exhumation of the folded nappe complex in the footwall of the kszs to have begun at 23 21 ma leading to rapid cooling between 21 and 16 ma this exhumation involved a combination of tectonic unroofing by extensional shearing upright folding and erosional denudation the contribution of tectonic unroofing is greatest along the central segment of the kszs and decreases westward to the central part of the tauern window the kszs formed in response to the indentation of wedge shaped blocks of semi rigid austroalpine basement located in front of the south alpine indenter that was part of the adriatic microplate northward motion of this indenter along the sinistral giudicarie belt offsets the periadriatic fault and triggered rapid exhumation of orogenic crust within the entire tauern window exhumation involved strike slip and normal faulting that accommodated about 100 km of orogen parallel extension and was contemporaneous with about 30 km of orogen perpendicular north south shortening of the etd extension of the pannonian basin related to roll back subduction in the carpathians began at 20 ma but did not affect the eastern alps before about 17 ma the effect of this extension was to reduce the lateral resistance to eastward crustal flow away from the zone of greatest thickening in the tauern window area therefore we propose that roll back subduction temporarily enhanced rather than triggered exhumation and orogen parallel motion in the eastern alps lateral extrusion and orogen parallel extension in the eastern alps have continued from 12 to 10 ma to the present and are driven by northward push of adria

multistage accretion and exhumation of the continental crust ivrea crustal section italy and switzerland the ivrea crustal section exposes in map view all levels of the southern alpine continental crust from ultramafic mafic and felsic granulite facies rocks of the deep crust ivrea verbano zone through medium grade basement rocks strona ceneri zone and val colla zone to unmetamorphosed permo mesozoic sediments the oldest part of the crustal section is preserved in the medium grade basement units which are interpreted to be the overprinted remains of an ordovician 440 480 ma magmatic arc or forearc complex during variscan subduction this arc was technically underplated by a carboniferous accretion subduction complex 320 355 ma containing metasediments and slivers of rheic oceanic crust presently found in the ivrea verbano zone during the late stages of variscan convergence 290 320 ma lithospheric delamination triggered magmatic underplating and lead to polyphase deformation under amphibolite to granulite facies conditions this was broadly coeval with extensional exhumation and erosion of the variscan overprinted ordovician crust presently exposed in the strona ceneri and val colla zones post variscan transtensional tectonics 270 290 ma were associated with renewed magmatic underplating mylonitic shearing and incipient exhumation of the lower crust in the ivrea verbano zone this coincided with the formation of elongate basins filled with volcanoclastic sediments in the upper crust early mesozoic tethyan rifting of the southern alpine crust 180 230 ma reduced crustal thickness to 10 km or less in the lower crust most of this thinning was accommodated by granulite to retrograde greenschist facies mylonitic shearing the lower crust was exhumed along a large noncoaxial mylonitic shear zone that was linked to asymmetrical rift basins in the upper crust the composite structure resulting from this complex evolution is probably typical of thinned late variscan continental crust on the passive margins of western europe alpine faulting and folding 20 50 ma fragmented the crustal section the originally deepest levels of the crustal section in the ivrea verbano zone as well as some segments of the basement cover contact were steepened whereas other parts of the crustal section particularly the strona ceneri zone underwent only minor to moderate alpine rotation

time calibration of a pt path from the western tauern window eastern alps the problem of closure temperatures new hornblende k ar and 39ar 40ar and mica rb sr and k ar ages are used to place specific timemarks on a well constrained pressure temperature path for the late alpine metamorphism in the western tauern window after identification of excess 40ar the closure behavior of ar in hornblende is compared with that of sr and ar in phengite and biotite samples were collected in three locations whose maximum temperatures were 570 c zemmgrund 550 c pfitscher joch and 500 540 c landshuter hutte

transform faulting extension and subduction in the carpathian pannonian region the carpathian arc formed during the cretaceous to miocene continental collision of europe with a smaller continental fragment following southward and westward subduction of an oceanic terrane during and after the last stages of thrusting in the outer carpathians a set of discrete basins opened up inside the carpathian loop these basins are regions of local extension which appear to be associated with strike slip faults in general northeast and northwest trending sets of conjugate shears reflect east west extension of the intra carpathian region during the middle and late miocene palinspastic reconstruction of the basins indicates approximately 75 to 100 km of extension comparable to the magnitude of synchronous crustal shortening in the east carpathians extension may have occurred to accommodate continued westward a type subduction after plate convergence was prohibited by geometrical constraints and suggests that in this region miocene subduction is driven by forces acting on the downgoing plate

neotectonic extrusion of the eastern alps constraints from u th dating of tectonically damaged speleothems we suggest that the salzachtal ennstal mariazell puchberg semp fault a major strike slip system in the european alps is active it has accommodated lateral extrusion of the central part of the eastern alps toward the pannonian basin the main tectonic activity of this fault dates back to oligocene and miocene time but until now it was largely unknown whether the fault was still active we present here the first field evidence of neotectonic activity from a cave in the hochschwab karst massif styria austria that intersects a segment of the semp fault zone damaged speleothems in this cave include scratched flowstone a hitherto undescribed feature massive flowstone disrupted by a fault and ruptured flowstone the superposition of younger flowstone layers allows constraining the time frame of the tectonic events using u th dating the youngest flowstone of the pre damage generation is ca 118 ka end of the last interglacial and the oldest post event layer is ca 9 ka early holocene the tectonic event bracketed by these layers coincided with a growth hiatus during the last glacial period consistent with the high alpine setting of the cave geologic evidence precludes deformation mechanisms other than tectonic these new data are consistent with vectors of continuous global positioning system measurements as well as instrumental seismicity data and collectively suggest that the semp is an active fault and that lateral extrusion of the eastern alps is ongoing

dating the longevity of ductile shear zones insight from 40ar 39ar in situ analyses we attempt to improve temporal constraints on the longevity and the termination of ductile shear zones by performing texturally controlled in situ 40ar 39ar analyses of pre kinematic muscovite biotite and k feldspars of syn kinematic phengite and k feldspar and of post kinematic phengite within the same samples of sinistral shear zones from the western tauern window eastern alps additionally two samples were dated by the rb sr method microsampling relative sequences of mineral formation based on microstructural cross cutting relationships were confirmed by in situ 40ar 39ar analyses showing that syn kinematic minerals are in general younger than pre kinematic minerals and older or of equal age than the post kinematic minerals of the same sample from the rim to the core of the western tauern window syn kinematic phengite and k feldspar reveal a set of formation ages varying between 33 and 15 ma for the northernmost and peripheral shear zone ahorn shear zone between 24 and 12 ma for the intermediate shear zone network tuxer shear zones and between 20 and 7 ma for the southernmost and central shear zone greiner shear zone the age variation of syn kinematic phengite and k feldspar analyses is larger than the analytical error of each age obtained in addition isochron calculations of the syn kinematic minerals reveal atmospheric like 40ar 36ar intercepts therefore the obtained age values of the syn kinematic minerals are interpreted as formation ages which date increments of a long lasting deformation period the time range of deformation of each shear zone system is bracketed by the oldest and youngest formation ages of syn kinematic phengite and k feldspar post kinematic phengite laths show the youngest formation ages and overlap with the youngest syn kinematic formation ages this relationship indicates that post kinematic growth occurred immediately after syn kinematic mineral formation at the end of ductile sinistral shear hence the termination of deformation is dated by the ages of these post kinematic phengite blasts pre kinematic minerals are characterized by break down and exsolution reactions and their age values are heterogeneous and often affected by the presence of extraneous ar these age values are usually older than but sometimes overlapping with ages of the syn kinematic minerals using the temporal constraints obtained by the ages of pre syn and post kinematic minerals we could assess partly overlapping time intervals of syn kinematic mineral formation of 19 myr 33 15 ma in the ahorn shear zone 13 myr 24 12 ma in the tuxer shear zones and 14 myr 20 7 ma in the greiner shear zone this indicates successive localization and propagation of ductile shear zones in the western tauern window from lower metamorphic sites at the rim towards higher metamorphic sites in the center

late stage differential exhumation of crustal blocks in the central eastern alps evidence from fission track and u th he thermochronology thermal history modelling based on zircon and apatite fission track and apatite u th he data constrain and refine the near surface exhumation of the south eastern tauern window penninic units and neighbouring austroalpine basement units in the eastern alps fast exhumation on both sides of the penninic austroalpine boundary coincides with a period of lateral extrusion and tectonic denudation of the penninic units in miocene time 22 12 ma the jump to older ages occurs within the austroalpine unit along the polinik fault which therefore defines the boundary between the tectonically denuded units and the hangingwall at that time according to the different u th he ages between the penninic hochalm and sonnblick domes we demonstrate a differential cooling history of these two domes in the latest miocene and early pliocene

lower miocene structural evolution of the central vienna basin austria abstract the tectonic evolution of the vienna basin overlying the alpine carpathian fold and thrust belt includes two stages of distinct basin subsidence and deformation the earlier phase contemporaneous with thrusting of the alpine carpathian floor thrust is related to the formation of a wedge top basin piggy back which was connected to the evolving foreland basin lower miocene c 18 5 16 ma this stage is followed by the formation of a pull apart basin middle to upper miocene c 16 8 ma sediments of the latter unconformably overly wedge top basin strata and protected them against erosion analyses of subcrop data from the central part of the basin focus on the complex stratal geometries and tectonics of the lower miocene wedge top basin during that period the overriding allochthon is characterised by syntectonic subsidence and sedimentation out of sequence fold thrusting normal faulting and sinistral wrenching all types of faults are dated as lower miocene by the occurrence of growth strata and the age of overlying post tectonic sediments related to the pull apart basin stage faults mapped in 3d seismic are compared to faults along the sw margin of the vienna basin they prove that complex lower miocene deformation occurred in large parts of the austroalpine overriding nappes concurrent with thrusting at the alpine floor thrust and in the molasse unit the structural analysis of 3d seismic data shows that lower miocene sediments of the ottnangian and karpatian stage unconformable overly the alpine carpathian thrust nappes with a thickness of up to 1500 m geometries include onlaps to the basin floor internal unconformities and toplaps to the overlying middle miocene sediments these toplaps are the results of tilting and subsequent erosion of the sediment pile by out of sequence thrusting in the central part at the karpatian badenian transition c 16 3 ma prior to the onset of pull apart deformation

comment on rosenberg and garcia estimating displacement along the brenner fault and orogen parallel extension in the eastern alps int j earth sci geol rundsch 2011 100 1129 1145 the western end of the tauern window is marked by what we refer to as the brenner normal fault zone the brenner fault since the late eighties is known as a textbook example of a normal fault already in 1934 dunner proposed west directed normal faulting related to updoming of the footwall i e the tauern window these earlier publications e g schmidegg 1953 mainly focussed on a brittle normal fault known as silltal fault that represents a northern segment of the brenner normal fault zone behrmann 1988 and selverstone 1988 were the first to also describe ductile components of normal faulting in an area further south referred to as sterzing steinach mylonite zone behrmann or brenner line selverstone in 1997 fugenschuh et al presented a two stage model for the evolution of the brenner normal fault zone thereby ductile normal faulting was restricted to an area between sterzing and matrei during stage 1 referred to as brenner normal fault s str in this contribution while brittle faulting during stage 2 not only overprinted the earlier mylonites of the brenner line s str but extended further north into the entirely brittle silltal fault this model involved coeval n s compression and e w extension during stage 1 the published calculated total amounts of related e w extension derived from metamorphic data and distinct exhumation histories in footwall and hanging wall and from the estimated dip of the overall fault zone varied significantly between 10 and 20 km e g behrmann 1988 and up to 70 km e g fugenschuh et al 1997 the contribution of exhumation by erosion as a consequence of coeval n s compression has never been explicitly considered and calculated so far

tectonic implications of the gps velocity field in the northern adriatic region 1 continuous and episodic gps observations between 1991 and 2004 show that adria moves independently of both stable eurasia and nubia adria moves nne at 3 4 5 mm yr increasing from n to s relative to eurasia and may be fragmenting along the gargano dubrovnik seismic zone the observed 2 3 mm yr of n s adria eurasia convergence is taken up by contraction across a narrow 70 km zone in the eastern alps and concomitant extrusion of the alpine north pannonian unit the adria central dinarides boundary is a broader collisional zone with intense 1 1 5 mm yr shortening near shore and 2 mm yr spread across the dinarides the remaining 1 2 mm yr motion e of the alps and ne of the dinarides is absorbed by the inverted contracting pannonian basin leaving no significant deformation above 0 5 mm yr in the western and northern carpathians and european platform

indentation model of the eastern alps and the origin of the tauern window a lithospheric model scaled for density and viscosity was shortened obliquely in front of an indenter whose shape and orientation match those of the south alpine indenter deformation was initially localized into subparallel sets of conjugate transpressive thrusts these structures evolved into folds which were strongly amplified and converged closer together during ongoing shortening finally forming a series of tight antiforms at the same time this tightly folded structure locally accommodated significant orogen parallel extension attaining 100 in front of the leading edge of the indenter but only 15 on the scale of the entire model the internal architecture and fault pattern of the model in map view are very similar to those of the tauern window in the eastern alps emphasizing the importance of localization of folding and shortening rather than orogen parallel extension for its formation

deformation partitioning during polyphase oblique convergence in the karawanken mountains southeastern alps abstract the karawanken mountains of southeastern austria straddle the insubric line a major fault zone that corresponds to the austroalpine south alpine border of the eastern alps they display polyphase structural patterns that resulted from deformation partitioning at shallow crustal levels following a poorly constrained late cretaceous deformation history paleogene contraction produced nw se trending fold thrust structures and possibly related sinistral cross faults miocene deformation produced both nw and se directed thrust faults and nw striking high angle dextral cross faults which merged with or displaced the w striking insubric line distributed dextral strike slip displacements of the order of 30 40 km and thrust displacement of 4 5 km along the northern karawanken front initiated subsidence of a small foreland basin north of the karawanken mountains recent regional deformation seems to be concentrated along cross cutting nnw striking dextral faults within a shifting system of seismogenic transfer faults that probably merge with the convergent south alpine thrust front to the west there are conspicuous parallels in the style of deformation along the karawanken mountains with that found along other seismogenic convergent strike slip faults such as those of southern california new zealand and anatolia

are the alps collapsing abstract orogenic collapse is a process that transfers gravitational potential energy from regions of high potential energy to regions of lower potential energy this transfer is classically considered to be accomplished by extension in the orogenic core and by synchronous shortening in foreland regions of the orogen not all extensional features in collisional mountain belts need however reflect orogenic collapse normal faulting thrust faulting and strike slip faulting are all active in different parts of the alps today and reflect complex local responses to ongoing europe adria convergence the western alps is the only area today where extension and shortening radial to orogen trend occur synchronously and where orogenic collapse may be an important process elsewhere in the alps normal faults are oriented at a high angle to orogen trend and were primarily active in oligocene and miocene time most present day activity in the central and eastern alps is on strike slip faults that are accommodati

deformation partitioning during updoming of the sonnblick area in the tauern window eastern alps austria the sonnblick dome forms a ne vergent dome structure cored by basement gneisses within the southeastern tauern window of the eastern alps austria a succession of ductile and brittle deformation stages documents doming and exhumation subsequent to the thermal peak of metamorphism contrasting deformation geometries within internal parts and along the margins of the dome are explained in terms of deformation partitioning subhorizontal shortening is documented by subvertical en echelon extensional gashes within central parts of the dome subhorizontal as well as subvertical flattening is also documented by fold structures during dextral transpression strike slip is accommodated along the ne margin sonnblick lamella moll valley fault and the southern margin moser fault of the sonnblick dome while vertical thickening occurred within the interior of the dome crustal thickening triggered unroofing and extension parallel to the dome axis which is documented by ductile low angle normal faults in the uppermost structural sections of the dome this normal fault system contributed to footwall uplift and exhumation of the dome structure the sonnblick lamella associated with the dextral moll valley fault forms a stretching fault where deformation is concentrated along a potential zone of weakness this fault is interpreted to represent the transition from vertical thickening within the dome to vertical thinning at the dome margins during upbending the dome structure passed the isotropic stress surface that is characterized by equality of 1 and 2 this is documented in a perturbation of the orientations of principal stress axes 1 and 2 while 3 remains constant in orientation transpression contributed substantially to updoming and to rapid nearly isothermal exhumation subsequent to the thermal peak of metamorphism

upper mantle structure beneath the alpine orogen from high resolution teleseismic tomography 1 to understand the evolution of the alpine orogen knowledge of the actual structure of the lithosphere asthenosphere system is important we perform high resolution teleseismic tomography with manually picked p wave arrival times from seismograms recorded in the greater alpine region the resulting data set consists of 4199 relative p wave arrivals and 499 absolute p wave arrivals from 76 teleseismic events corrected for the contribution of the alpine crust to the travel times the three dimensional 3 d crustal model established from controlled source seismology data for that purpose represents the large scale alpine crustal structure absolute p wave arrival times are used to compute an initial reference model for the inversion tests with synthetic data document that the combination of nonlinear inversion high quality teleseismic data and usage of an a priori 3 d crustal model allows a reliable resolution of cells at 50 km 50 km 30 km hence structures as small as two cells can be resolved in the upper mantle our tomographic images illuminate the structure of the uppermost mantle to depth of 400 km along strike of the alps the inversion reveals a high velocity structure that dips toward the se beneath the adriatic microplate in the western and central alps in the eastern alps we observe a northeastward dipping feature subducting beneath the european plate we interpret this feature in the western and central alps as subducted mainly continental european lower lithosphere for the east we propose that parts of the vardar oceanic basin were subducted toward the ne forcing continental adriatic lower lithosphere to subduct northeastward beneath the european plate

young alpine dykes south of the tauern window austria a k ar and sr isotope study fortyfive new k ar ages and sr isotope data on amphiboles biotites clinopyroxenes and whole rock samples from subvolcanic dykes south of the tauern window establish that alkalibasaltic dykes were intruded 30 m y ago and shoshonitic volcanism occured between 30 and 24 m y ago two calc alkaline rocks of high potassium composition yielded ages of 40 and 26 m y resp a spread which may or may not be real calc alkaline dykes with medium and low potassium contain excess argon and are hence undatable alkalibasaltic dykes have 87sr 86sr ratios of 0 7056 0 7070 shoshonitic rocks 0 7075 0 7133 potassium rich calc alkaline dykes 0 7077 0 7100 87sr 86sr of all other calc alkaline rocks scatter between 0 7074 and 0 7150 sr data indicate that dykes studied do not represent closed sr systems but that sr characteristics result from selective strontium assimilation en route to surface primary sr isotopic ratios of alkalibasaltic dykes point to an origin of these rocks in enriched sub continental upper mantle the source region of shoshonitic and high potassium calcalkaline rocks could have 87sr 86sr around 0 707 which is assigned to the input of a component rich in alkalies lree and lil elements genetic relationships with other tertiary magmatites of similar geotectonic position are explained in terms of plate tectonic models of the eastern alps

alpine metamorphism in the south east tauern window austria 1 p t variations in space and time the pennine rocks exposed in the south east tauern window austria contain mineral assemblages which crystallized in the mid tertiary late alpine regional metamorphism the pressure and temperature conditions at the thermal peak of this event have been estimated for rocks at four different structural levels using a variety of published and thermochemically derived geobarometers and geothermometers the results are a in the garnet chlorite zone 2 5 km structurally above the staurolite biotite isograd t 490 50 c p 7 1 kbar b within 0 5 km of the staurolite biotite isograd t 560 300c p 7 1 kbar c in the staurolite biotite zone c 2 5 km structurally below the staurolite biotite isograd t 610 30 c p 7 6 1 2 kbar d in the staurolite biotite zone 3 4 km structurally below the staurolite biotite isograd t 630 40 c p 6 6 1 2 kbar the pressure estimates imply that the total thickness of overburden above the basement cover interface in the mid tertiary was c 26 4 km this overburden can only be accounted for by the austro alpine units currently exposed in the vicinity of the tauern window if the altkristallin the middle austro alpine nappe was itself buried beneath an upper austro alpine nappe or nappe pile which was 7 4 km thick at that time the occurrence of epidote margarite quartz pseudomorphs after lawsonite in garnet indicates that part of the mesozoic pennine cover sequence in the south east tauern experienced blueschist facies conditions t 450 c p 12 kbar in early alpine times evidence from the central tauern is used to argue that the blueschist facies imprint post dated the main phase of tectonic thickening d1a and was thus a direct consequence of continental collision combined oxygen isotope and fluid inclusion studies on late stage veins thought to have been at lithostatic pressure and in thermal equilibrium with their host rocks during formation suggest that they crystallized from aqueous fluids at 1 1 0 4 kbar and 420 20 c early alpine late alpine and vein formation p t constraints have been used to construct a p t path for the base of the mesozoic cover sequence in the south east tauern window the prograde part of the p t path between early and late alpine metamorphic imprints is unlikely to have been a smooth curve and may well have had a low dp dt overall the decompression presumably due to erosion which occurred immediately before the thermal peak and possibly also earlier in the tertiary was probably partly or completely cancelled by the effects of early to mid tertiary d2a tectonic thickening the thermal peak of metamorphism was followed by a phase of almost isothermal decompression which implies a period of rapid uplift in the middle tertiary the peak metamorphic p t estimates are compared with the solutions of england s 1978 one dimensional conductive thermal model of the eastern alps and are shown to be consistent with the idea that the late alpine metamorphism was caused by tectonic burial of the pennine zone beneath the austro alpine nappes in the absence of extraneous heat sources such as large intrusions at depth

zur geologie des thurntaler quarzphyllits und des altkristallins sudlich des tauernfensters ostalpen sudtirol geologische und petrographische untersuchungen im thurntaler quarzphyllit und im angrenzenden altkristallin sudlich des tauernfensters lassen einen mehrfachen wechsel von deformation und kristallisation erkennen im gesamten untersuchungsbereich waren vor allem deformationen gefugepragend fur die gesteine

the monte orfano conglomerate revisited stratigraphic constraints on cenozoic tectonic uplift of the southern alps lombardy northern italy the monte orfano conglomerate moc exposed in the foothills of the southern alps northern italy is one of the few outcrops of sediments documenting the cenozoic tectonic evolution of the alpine retrowedge calcareous nannofossil biostratigraphy allowed us to constrain the upper part of the moc formerly attributed to the early middle miocene in the type locality to the earliest miocene neogene part of the nn1 nannofossil zone a likely latest oligocene age is therefore suggested for the bulk of the underlying conglomerates whose base is not exposed deposition of the moc can be placed within the post collisional tectonic uplift of the alps documented in the lake como area by the como conglomerate cc at the base of the gonfolite lombarda group and supports the correlation with upper oligocene clastic sediments cropping out further to the east in the lake garda and in the veneto friuli areas molassa the remarkable difference in petrographic composition between the western cc and eastern moc clastics deposited in the alpine retro foreland basin highlights the synchronous tectonic activity of two structural domains involving different crustal levels whilst the bulk of the cc that straddles the oligocene miocene boundary records largely the tectonic exhumation of the alpine axial chain crystalline complexes the coeval moc consists of detritus derived from the superficial crustal section triassic to paleogene sedimentary rocks of the alpine retrowedge and constrains the onset of the post collisional deformation phase of the southern alps as not younger than the late oligocene

balancing lateral orogenic float of the eastern alps abstract oligocene to miocene post collisional shortening between the adriatic and european plates was compensated by frontal thrusting onto the molasse foreland basin and by contemporaneous lateral wedging of the austroalpine upper plate balancing of the upper plate shortening by horizontal retrodeformation of lateral escaping and extruding wedges of the austroalpine lid enables an evaluation of the total post collisional deformation of the hangingwall plate quantification of the north south shortening and east west extension of the upper plate is derived from displacement data of major faults that dissect the austroalpine wedges indentation of the south alpine unit corresponds to 64 km north south shortening and a minimum of 120 km of east west extension lateral wedging affected the eastern alps east of the giudicarie fault west of the giudicarie fault north south shortening was compensated by 50 to 80 km of backthrusting in the lombardian thrust system of the southern alps the main structures that bound the escaping wedges to the north are the inntal fault system ca 50 km sinistral offset the konigsee lammertal traunsee klt fault 10 km and the salzach ennstal mariazell puchberg semp fault system 60 km these faults as well as a number of minor faults with displacements less than 10 km root in the basal detachment of the alps the thin skinned nature of lateral escape related structures north of the semp line is documented by industry reflection seismic lines crossing the northern calcareous alps nca and the frontal thrust of the eastern alps complex triangle zones with passive roof backthrusts of middle miocene molasse sediments formed in front of the laterally escaping wedges of the northern eastern alps the aim of this paper is a semiquantitative reconstruction of the upper plate of the eastern alps most of the data is published elsewhere

a 300 kyr record of aridity and wind strength in southwestern africa inferences from grain size distributions of sediments on walvis ridge se atlantic abstract the terrigenous fraction of sediments recovered from walvis ridge se atlantic ocean reveals a history of southwestern african climate of the last 300 kyr end member modelling of a data set of grain size distributions n 428 results in three end members the two coarsest end members are interpreted as eolian dust the third end member as hemipelagic mud the ratio of the two eolian end members reflects the eolian grain size and is attributed to the intensity of the se trade winds trade winds were intensified during glacials compared to interglacials changes in the ratio of the two eolian end members over the hemipelagic one are interpreted as variations in southwestern african aridity late quaternary southwestern african climate was relatively arid during the interglacial stages and relatively humid during the glacial stages owing to meridional shifts in the atmospheric circulation system during glacials the polar front shifted equatorward resulting in a northward displacement of the zone of westerlies causing increased rainfall in southwestern africa the equatorward shift of the polar front is coupled with an increase of the meridional pressure gradient leading to enhanced atmospheric circulation and increased trade wind intensity

alpine orogenic evolution from subduction to collisional thermal overprint the 40ar 39ar age constraints from the valaisan ocean central alps 1 the investigated hp lt metasedimentary units of the valaisan and adjacent european domains occupy a key position in the alpine belt for understanding the transition from early subduction related hp lt metamorphism to collision related barrovian overprint and the evolution of mountain belts in general the timing of high pressure metamorphism subsequent retrogression and following barrow type overprint was studied by 40ar 39ar dating of biotite and several white mica generations that are well characterized in terms of mineral chemistry texture and associated mineral assemblages four distinct age populations of white mica record peak pressure conditions 42 40 ma and several stages of subsequent retrograde metamorphic evolution 36 25 ma biotite isotopic analyses yield consistent apparent ages that cluster around 18 16 ma for the barrow type thermal overprint the recorded isotopic data reveal a significant time gap in the order of some 20 ma between subduction related hp lt metamorphism and collision related barrovian overprint supporting the notion of a polymetamorphic evolution associated with a bimodal p t path

alpine geodynamic evolution of passive and active continental margin sequences in the tauern window eastern alps austria italy a review the penninic oceanic sequence of the glockner nappe and the foot wall penninic continental margin sequences exposed within the tauern window eastern alps have been investigated in detail field data as well as structural and petrological data have been combined with data from the literature in order to constrain the geodynamic evolution of these units volcanic and sedimentary sequences document the evolution from a stable continent that was formed subsequent to the variscan orogeny to its disintegration associated with subsidence and rifting in the triassic and jurassic the formation of the glockner oceanic basin and its consumption during the upper cretaceous and the paleogene these units are incorporated into a nappe stack that was formed during the collision between a penninic zentralgneis block in the north and a southern austroalpine block the venediger nappe and the storz nappe are characterized by metamorphic jurassic shelf deposits hochstegen group and cretaceous flysch sediments kaserer and murtorl groups the eclogite zone and the rote wand modereck nappe comprise permian to triassic clastic sequences wustkogel quartzite and remnants of platform carbonates seidlwinkl group as well as jurassic volcanoclastic material and rift sediments brennkogel facies covered by cretaceous flyschoid sequences nappe stacking was contemporaneous to and postdated subduction related high pressure eclogite and blueschist facies metamorphism emplacement of the eclogite bearing units of the eclogite zone and the glockner nappe onto penninic continental units zentralgneis block occurred subsequent to eclogite facies metamorphism the eclogite zone a former extended continental margin was subsequently overridden by a pile of basement cover nappes rote wand modereck nappe along a ductile out of sequence thrust low angle normal faults that have developed during the jurassic extensional phase might have been inverted during nappe emplacement