paragonite hornblende assemblages and their petrological significance an example from the austroalpine schneeberg complex southern tyrol italy paragonite bearing amphibolites occur interbedded with a garbenschist micaschist sequence in the austroalpine schneeberg complex southern tyrol the mineral assemblage mainly comprises paragonite mg hornblende tschermakite quartz plagioclase biotite ankerite ti phase garnet muscovite equilibrium p t conditions for this assemblage are 550 600 c and 8 10 kbar estimated from garnet amphibole plagioclase ilmenite rutile and si contents of phengitic muscovites in the vicinity of amphibole paragonite is replaced by symplectitic chlorite plagioclase margarite biotite assemblages muscovite in the vicinity of amphibole reacts to form plagioclase biotite margarite symplectites the reaction of white mica hornblende is the result of decompression during uplift of the schneeberg complex the breakdown of paragonite hornblende is a water consuming reaction and therefore it is controlled by the availability of fluid on the retrogressive p t path paragonite hornblende is a high temperature equivalent of the common blueschist assemblage paragonite glaucophane in ca bearing systems and represents restricted p t conditions just below omphacite stability in a mafic bulk system while paragonite glaucophane breakdown to chlorite albite marks the blueschist greenschist transition the paragonite hornblende breakdown observed in schneeberg complex rocks is indicative of a transition from epidote amphibolite facies to greenschist facies conditions at a flatter p t gradient of the metamorphic path compared to subduction zone environments ar ar dating of paragonite yields an age of 84 5 1 ma corroborating an eoalpine high pressure metamorphic event within the austroalpine unit west of the tauern window eclogites that occur in the otztal crystalline basement south of the schneeberg complex are thought to be associated with this eoalpine metamorphic event

an evaluation of criteria to deduce the sense of movement in sheared rocks some of the most useful criteria for the deduction of the sense of shear are summarized for use in areas where unequivocal field evidence is lacking apparently conflicting evidence from rotated pressure shadow regions around porphyroclasts and porphyroblasts is clarified the use of quartz crystallographic fabric asymmetry to deduce the shear sense in the bulk rock should be treated with caution and used only together with detailed microstructural observations

the schneeberg normal fault zone normal faulting associated with cretaceous se directed extrusion in the eastern alps italy austria abstract the cretaceous eo alpine collisional event in the european eastern alps is generally accepted to induce w nw directed thrusting both in basement and in sedimentary cover units this study presents the first evidence of eo alpine w nw directed normal kinematics along the schneeberg normal fault zone which separates eo alpine high pressure rocks in a footwall position from pre alpine basement rocks in a hanging wall position new garnet sm nd data indicate that exhumation of the high pressure rocks along the normal fault zone started around 95 ma ago and continued up to low greenschist brittle conditions at 76 ma as indicated by a rb sr age from a low temperature mylonite the occurrence of pre alpine basement rocks both in the hanging wall and the footwall of eo alpine high pressure rocks suggests exhumation by extrusion processes despite the displacement or removal of parts of the lower portion of the high pressure unit by tertiary strike slip faults eo alpine top to ese thrusting as expected for the structurally lower part of an extruding wedge was found at and below the base of the eo alpine high pressure rocks a rb sr age of 77 ma from a greenschist facies mylonite in this thrust shear zone shows the contemporaneity of deformation at the base and the top of the wedge the tectonic transport direction within the extruding wedge was e se opposite to the w nw direction so far reported for the eo alpine event in the eastern alps the contemporaneity of opposite tectonic transport directions during continental subduction may be explained by a double vergent wedge model with a narrow zone of ductile flow where the high pressure rocks were exhumed

kinematics of the inntal shear zone sub tauern ramp fault system and the interpretation of the transalp seismic section eastern alps austria abstract a new interpretation of the inntal tauern sector of the transalp seismic section is presented one of the most prominent contrasts in reflectivity in the transalp seismic section is the contact between the bajuvaric unit in the footwall and the overlying tirolic unit and its basement across a moderately south dipping interface we trace this contact from the surface at the southern margin of the inn valley to a depth of 5 km there the contact is deformed or cut by the tauern window northern margin we define the contact between bajuvaric and tirolic units as brixlegg thrust which is older than miocene tauern window exhumation and has a paleogene age the sub tauern ramp connects with the inntal fault system at the surface and roots below the tauern window oblique thrust movements across this fault system in the miocene caused exhumation of the hanging wall where the fault has a ramp geometry which is in the area of the transalp cross section and west of it east of the transalp cross section the fault system merges with alpine basal thrust which is a flat no miocene exhumation occurred above the flat

astronomical tuning of the aptian stage from italian reference sections a high resolution grayscale series of the pelagic fucoid marls piobbico core central italy shows strong pervasive lithological rhythms throughout the aptian interval a hierarchy of centimeter to meter scale cycles characterizes the rhythms when calibrating 1 m cycles to earth s 405 k y orbital eccentricity cycle these rhythms correspond to the periods of the eccentricity obliquity and precession index tuning to orbital eccentricity cycles provides a high resolution time scale for the aptian correlation to the cismon core northern italy extends the tuning to the aptian barremian boundary the tuning indicates a minimum duration of 13 42 m y for the aptian stage where previous estimates range from 6 4 to 13 8 m y the combined aptian albian astronomical tuning of the entire 77 m long piobbico core and part of the cismon core provides a 25 85 m y long astronomically calibrated time scale for earth history

cretaceous to neogene cooling and exhumation history of the oetztal stubai basement complex eastern alps a structural and fission track study the central austroalpine oetztal stubai basement complex osk of the eastern alps together with its overlying sedimentary brenner mesozoic bmz and tectonic units upper austroalpine nappes underwent extension and exhumation during the cretaceous before its incorporation into the hanging wall of the neogene brenner normal fault during this late cretaceous to early tertiary deformation the brenner mesozoic and the immediately underlying uppermost part of the osk developed a strong stretching lineation within a near horizontal and often mylonitic foliation related to consistent top to ese directed transport quartz and calcite behaved ductilely throughout the area whereas dolomite shows a transition from brittle fracture in the north to plastic flow in the south consistent with the known cretaceous metamorphic temperature gradient the transition to crystal plastic flow of dolomite occurs at 480 c quartz textures indicate an increase in the contribution of prism glide together with a decrease in basal glide toward the south also consistent with the temperature gradient in the osk and bmz fission track analysis of both zircon and apatite along a n s profile in combination with existing data from the literature allows a continuous cooling path to be constructed for the osk cooling of the eastern osk started at 90 ma the thermal peak of metamorphism and ended some 30 myr later at near surface temperatures at 60 ma the northern region had already cooled below the upper limit of the apatite partial annealing zone whereas in the south cooling related to this exhumation phase stopped at temperatures between 100 and 200 c the ese directed shearing is interpreted as late cretaceous to early tertiary normal faulting that exhumed the osk and brought the upper austroalpine blaser and steinacher nappes into contact with the underlying brenner mesozoic the pattern of alpine metamorphic isograds established in the osk directly reflects the geometry and kinematics of this late cretaceous early tertiary exhumation due to low angle normal faulting

the western end of the eoalpine high pressure belt texel unit south tyrol italy eclogites in the texel unit eastern alps south tyrol italy represent the westernmost outcrops of the e w striking eoalpine high pressure belt ehb east of the tauern window the ehb forms part of a cretaceous intracontinental south dipping subduction collision zone however the same nappe stack displays a northwest dip at its western end this prominent change in dip direction gave rise to discussions on the general setting of the eoalpine collision based on our own observations and literature data we present a new tectonic model for the western end of the ehb due to the special situation of this area at the tip of the southalpine indenter originally south east dipping structures became overturned and former thrusts appear as normal faults e g schneeberg fault zone while former normal faults presently display thrust geometries e g jaufen fault thus we explain the current configuration with a coherent eoalpine subduction direction

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

thermal evolution of an extensional detachment as constrained by organic metamorphic data and thermal modeling graz paleozoic nappe complex eastern alps abstract following early cretaceous nappe stacking the eastern alps were affected by late orogenic extension during the late cretaceous in the eastern segment of this range a late cretaceous detachment separates a very low to low grade metamorphic cover graz paleozoic nappe complex gpnc above a low to high grade metamorphic basement synchronously the kainach gosau basin kgb collapsed and subsided on top of the section metamorphism of organic material within this section has been investigated using vitrinite reflectance data and raman spectra of extracted carbonaceous material in the southern part of the gpnc vitrinite reflectance indicates a decrease in organic maturity towards the stratigraphic youngest unit the remaining part of the gpnc is characterized by an aureole of elevated vitrinite reflectance values and raman r2 ratios that parallels the margins of the gpnc vitrinite reflectance in the kgb shows a steep coalification gradient and increases significantly towards the western basin margin the observed stratigraphic trend in the southern gpnc is a result of deep paleozoic to early cretaceous burial this maturity pattern was overprinted along the margins by advective heat and convective fluids during late cretaceous to paleogene exhumation of basement rocks during shearing the fault zone was heated up to ca 500 c this overprint is explained by a two dimensional thermal model with a ramp flat fault geometry and a slip rate of 1 to 1 5 cm year during 5 ma fault movement the collapse basin above the detachment subsided in a thermal regime which was characterized by relaxing isotherms

cooling and exhumation of the rieserferner pluton eastern alps italy austria the defereggen antholz vals dav line marks the southern border of alpine greenschist facies metamorphism within the austroalpine basement to the south of the western tauern window during the oligocene sinistral strike slip coeval with vertical displacement was accompanied by the syntectonic emplacement of the rieserferner pluton along the north side of the fault to the north of the dav line rb sr as well as k ar biotite cooling ages continuously increase from 16 ma at the rensen pluton in the west to 30 ma at the eastern end of the rieserferner pluton similar trends are apparent from zircon and apatite fission track data which increase eastward from 19 to 29 ma and 13 to 16 ma respectively low cooling rates allow a direct transformation into exhumation rates assuming an average geothermal gradient of 28 c km 1 the resulting exhumation rates of less than 1 mm year 1 do not affect the depth of isotherms in a geologically significant manner hence variable cooling rates within the basement north of the dav line are a result of differential exhumation of individual blocks high exhumation rates bracketed between the intrusion age of the rieserferner pluton at 31 3 ma and the apatite partial annealing zone paz range between 0 4 and 0 6 mm year 1 whereas final exposure takes place at reduced exhumation rates of 0 2 mm year 1 east side down tilting of the block north of the dav line as indicated by variations in exhumation rates strongly affects the western part of the area studied between the rensen and the central rieserferner pluton whereas further east block rotation becomes less important a total difference in exhumation of about 2 2 km corresponding to 5 tilting between the western and eastern rieserferner as indicated by k ar biotite and zircon fission track data occurred before going through the paz for apatite fission tracks furthermore the significance of the cooling ages especially for biotite is tested by calculating a finite element approximation different numerical models indicate fast cooling of the intrusive melts prior to approaching the closure temperature of the k ar system in biotite

late cretaceous synorogenic low angle normal faulting along the schlinig fault switzerland italy austria and its significance for the tectonics of the eastern alps abstract the schlinig fault at the western border of theotztal nappe eastern alps previously interpreted as a west directed thrust actually represents a late cretaceous top se to ese normal fault as indicated by sense of shear criteria found within cataclasites and greenschist facies mylonites normal faulting postdated and offset an earlier cretaceous age west directed thrust at the base of theotztal nappe shape fabric and crystallographic preferred orientation in completely recrystallized quartz layers in a mylonite from the schlinig fault record a combination of 1 top east southeast simple shear during late cretaceous normal faulting and 2 later north northeast directed shortening during the early tertiary also recorded by open folds on the outcrop and map scale offset of the basal thrust of theotztal nappe across the schlinig fault indicates a normal displacement of 17 km the fault was initiated with a dip angle of 10 to 15 low angle normal fault domino style extension of the competent late triassic hauptdolomit in the footwall was kinematically linked to normal faulting the schlinig fault belongs to a system of east to southeast dipping normal faults which accommodated severe stretching of the alpine orogen during the late cretaceous the slip direction of extensional faults often parallels the direction of earlier thrusting top w to top nw only the slip sense is reversed and the normal faults are slightly steeper than the thrusts in the western austroalpine nappes extension started at about 80 ma and was coeval with subduction of piemont ligurian oceanic lithosphere and continental fragments farther west the extensional episode led to the formation of austroalpine gosau basins with fluviatile to deep marine sediments west directed rollback of an east dipping piemont ligurian subduction zone is proposed to have caused this stretching in the upper plate

timing and deformation conditions of the tallulah falls dome ne georgia implications for the alleghanian orogeny structural domes composed of crystalline rocks metamorphosed to midcrustal conditions are present in every major orogen and record deformation of the deep interior of mountain ranges the tallulah falls dome in northeast georgia is a shear zone bounded body of metasedimentary rocks that is defined by a foliation pattern that crosscuts the regional fabric of the eastern blue ridge crystalline nappe in the southern appalachian mountains previously the tallulah falls dome was interpreted as the expression of duplexed underlying slices of laurentian margin sedimentary rocks imbricated during alleghanian emplacement of the allochthonous blue ridge thrust sheet under greenschist facies conditions we provide new observations of quartz and feldspar recrystallization fabrics and new 40 ar 39 ar dates from muscovite that complement existing thermochronometric ages to determine the timing and conditions of doming within the tallulah falls dome our microstructural observations are consistent with deformation mechanisms active dominantly at amphibolite facies conditions with some samples recording temperatures in excess of 650 c thermochronometric ages define a period of relatively rapid cooling from 550 c to 340 c within and around the tallulah falls dome between 321 and 317 ma with differential cooling across the northwestern dome bounding shear zone lasting until at least 313 ma our observations reveal a period of early alleghanian cooling from amphibolite to greenschist facies conditions associated with displacement along a shear zone bounding the tallulah falls dome across the blue ridge the alleghanian orogeny has long been characterized only by thrusting at greenschist facies conditions similarly dome formation has been interpreted as the result of duplexing within the thin skinned blue ridge crystalline thrust sheet as it was emplaced upon the laurentian margin both of these interpretations are inconsistent with the new data presented here which suggest more complex alleghanian deformation over a broader range in temperatures and perhaps a diverse suite of structural styles our results are best explained by doming of the footwall of a normal displacement shear zone at amphibolite facies conditions during the earliest alleghanian period

numerical analysis of x ray texture data an implementation in fortran allowing triclinic or axial specimen symmetry and most crystal symmetries abstract the use of complete descriptions of preferred orientation for studies of experimentally and naturally deformed rocks is discussed diagrammatic representations of preferred orientations are defined and conventions for coordinate systems are given methods of extracting information from the orientation distribution function are described a system of fortran programs which enables the orientation distribution function to be calculated for most suitable minerals is described

spatial and temporal variability of trace element concentrations in an urban subtropical watershed honolulu hawaii trace metal concentrations in soils and in stream and estuarine sediments from a subtropical urban watershed in hawaii are presented the results are placed in the context of historical studies of environmental quality water soils and sediment in hawaii to elucidate sources of trace elements and the processes responsible for their distribution this work builds on earlier studies on sediments of ala wai canal of urban honolulu by examining spatial and temporal variations in the trace elements throughout the watershed natural processes and anthropogenic activity in urban honolulu contribute to spatial and temporal variations of trace element concentrations throughout the watershed enrichment of trace elements in watershed soils result in some cases from contributions attributed to the weathering of volcanic rocks as well as to a more variable anthropogenic input that reflects changes in land use in honolulu varying concentrations of as cd cu pb and zn in sediments reflect about 60 a of anthropogenic activity in honolulu land use has a strong impact on the spatial distribution and abundance of selected trace elements in soils and stream sediments as noted in continental us settings the phasing out of pb alkyl fuel additives has decreased pb inputs to recently deposited estuarine sediments yet a substantial historical anthropogenic pb inventory remains in soils of the watershed and erosion of surface soils continues to contribute to its enrichment in estuarine sediments concentrations of other elements e g cu zn cd however have not decreased with time suggesting continued active inputs concentrations of ba co cr ni v and u although elevated in some cases typically reflect greater proportions attributed to natural sources rather than anthropogenic input

use of neural network to predict flash flood and attendant water qualities of a mountainous stream on oahu hawaii summary frequent flash floods of hawaii streams pose continuous threats to the coastal environment because the streams respond rapidly to high runoff and huge transport quantities of sediments to which are sorbed nutrients heavy metals and persistent hydrophobic organic compounds high frequency stream flow and water quality estimation are essential to correctly assess water quality variations and pollutant loads during flash floods because stream flow and turbidity in hawaii can change by a factor of 60 and 30 respectively in 15 min this study shows the application of artificial neural networks anns to assess flash floods and their attendant water quality parameters using measured data of a hawaii stream the paper illustrates that anns predict stream flow with a correlation coefficient r greater than 0 99 and turbidity and specific conductance with r values greater than 0 80 although the r values for the estimation of dissolved oxygen ph and water temperature were somewhat low most of the estimated stream water quality values turbidity specific conductance dissolved oxygen ph and water temperature were within the limits of 30 deviations of the 1 1 line the r value for the estimation of stream water qualities could have been significantly improved if high resolution at 15 min or lower measurement frequency noise free and continuous data were available for a longer period of time the paper demonstrates that the upstream water quality parameters depend on weather forces and land use of the watershed and the downstream water quality parameters additionally influenced by oceanic tides stream stage is found to be an important input parameter for stream flow prediction using ann however the predictive performance of ann for the estimation of stream flow is improved if weather data rainfall and evapotranspiration are included in the input data set

sm nd dating of hydrothermal carbonate formation an example from the breitenau magnesite deposit styria austria abstract the geochemical evolution and chronology of the breitenau sparry magnesite deposit has been investigated by means of major and trace element abundances stable c o isotope and sm nd isotope analysis chemically separated magnesite fractions leachates show consistent light ree depleted rey patterns marine carbonate normalized and nearly constant normalized values for the middle and heavy ree without significant ce eu or y anomalies non carbonate residues composed of dark matrix material are high in al 2 o 3 and show variably light to middle ree enriched rey patterns similar to shales leachates of limestone from nearby country rocks have normalized rey patterns similar to marine carbonates only ce and y are slightly fractionated based on their trace element chemistry and normalized rey patterns leachates of dolomite from the margin of the deposit closely resemble either limestone type a or magnesite type b with one exception 18 o vpdb for both dolomite types is within the range of the respective magnesite values 18 o vpdb c 14 2 to 15 7 leachates of dolomite from druses within the deposit type c show low rey abundances with normalized patterns similar to those of magnesite sm nd isotope data for magnesite leachates yield a well defined isochron age of 222 5 9 8 ma mswd 3 1 isochron calculations for leachate s and residue s from individual magnesite samples internal isochrons yield ages between 236 16 ma and 193 5 8 6 ma with a low degree of scatter mswd 18 o vpdb c 15 2 37 9 5 4 ma 18 o vpdb c 12 5 and 3 1 7 6 8 ma 18 o vpdb c 11 type c dolomite data indicate that druses were formed by open system fluid flow throughout the deposit

late cretaceous intraplate thrusting in central europe effect of africa iberia europe convergence not alpine collision a well established event of intraplate basin inversion and basement thrusting affected central europe in late cretaceous time it is widely accepted to have resulted from the collision of the alpine orogen with europe s margin at that time an early alpine orogen located on the leading edge of the adria microplate still lay far southeast of its present day position and had entered a phase of extension after a first orogenic event characterized by w to nw directed thrusting this configuration is not likely to have induced ssw nne directed thrusting and folding in the future european foreland that was still separated from the alpine wedge by a strip of oceanic lithosphere by contrast the onset of intraplate contraction coincides with an important change in relative motion between the european and african plates at ca 90 ma africa s sse directed sinistral transform motion relative to europe changed to ne directed convergence this agrees well with the timing and kinematics of intraplate thrusting in central europe structures of similar age and kinematics occurring in southern france spain and north africa suggest that the late cretaceous pulse of contraction was caused by pinching west central europe s thin lithosphere between baltica and africa only since the onset of n directed thrusting in the alps in paleocene or eocene time are the kinematics of the alps and their european foreland compatible indicating that mechanical coupling between africa europe and the adria microplate had been achieved

late oligocene neogene evolution of europe adria collision new structural and geochronological evidence from the giudicarie fault system italian eastern alps the giudicarie fault system giudicarie sensu stricto meran mauls passeier thurnstein and jaufen faults represents a sharp break in the generally e w strike direction of the orogen scale periadriatic fault system and is a key element for understanding the late oligocene neogene evolution of the alpine chain the kinematics timing and magnitude of movements on the giudicarie fault system are presented here on the basis of a detailed structural study of the component fault segments combined with zircon and apatite fission track analysis from closely spaced samples two main tectonic phases are established 1 back thrusting of the austroalpine units over the southern alps around 32 ma recorded by basement and limestone mylonites along the giudicarie and meran mauls faults with transport directions toward 100 110 and 2 later sinistral transpressive displacement characterized by structures at the ductile brittle transition which overprinted the top to e ese thrust related mylonites but also partitioned into a major system of transcurrent faults in the southalpine domain it was during this later event that the periadriatic fault attained its present day geometry however the amount of sinistral displacement along the giudicarie system was only 15 20 km the magnitude is established here from the 15 km sinistral offset of the jaufen mylonites across the passeier brittle fault and the 20 km long gap in the otherwise continuous distribution of oligocene tonalitic lamellae along the giudicarie fault a direct structural connection is also established between the brenner and the jaufen faults this constrains the timing of the second phase since it must postdate the main exhumation phase of the tauern window at 20 18 ma the results of this study argue against an originally straight periadriatic fault the giudicarie fault formed a restraining bend in this part of the periadriatic fault system since at least the late miocene and probably since the late oligocene

deep structure and kinematics of the northern calcareous alps transalp profile the northern calcareous alps nca of southern bavaria and northern tyrol constitute a carbonate dominated polyphase fold thrust wedge together with its grauwacken zone basement it is the northernmost part of the far travelled upper austroalpine thrust complex of the eastern alps the present geometry developed in several kinematic stages jurassic extensional faults that affected large parts of the nca and their basement originated when the main part of the nca was still located southeast of the central alpine otztal silvretta complex these faults and related facies transitions influenced the later style of detachment of the nca thrust sheets mid to late cretaceous detachment thrust sheet stacking and motion over the central alpine complex are registered in clastic deposits of syntectonic basins the latest cretaceous to cenozoic nne to n directed motion of the nca towards europe in front of the central alpine complex created another set of significant contraction structures which at depth overprinted all previous structures during cretaceous to cenozoic deformation the nca experienced about 80 km of shortening i e about 73 along the transalp profile the european basement and autochthonous mesozoic cover beneath the allochthonous nca thrust sheets and flysch complexes seem to have remained relatively undeformed

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

transition from near surface thrusting to intrabasement decollement schlinig thrust eastern alps west directed thrusting along the schlinig thrust amounts to a minimum displacement of 45 km a discrete plane of brittle thrusting is observed in the frontal part where the otztal unit overrides the sediments of the engadine dolomites both shortening of the more ductile lower and middle triassic and very substantial stretching by domino type normal faults in the brittle upper triassic dolomites are contemporaneous with and caused by thrusting extension is related to extrusion of parts of the sediments in the footwall of the schlinig thrust a relatively rapid transition into an intrabasement shear zone which is as much as 2 km thick occurs farther to the east in a region where a paleotemperature of 300 c is indicated for cretaceous metamorphism still farther to the east localized shearing is transformed into a wider area affected by large scale folding this second transition corresponds to estimated temperatures in excess of 550 c since the changes in structural style and deformation mechanisms toward the hinterland go hand in hand with increasing metamorphic grade we regard thrusting as contemporaneous with metamorphism this view is supported by geochronological data the age of thrusting and metamorphism 90 ma indicates very rapid heating after the deposition of the youngest sediments cenomanian involved in cretaceous deformation our data suggest that localized detachment along a discrete thrust plane and within broader mylonite zones cannot always be traced indefinitely to greater depth the transformation of localized shearing into large scale folding indicates a fundamentally different deformational style for lower crustal levels

the tectonic evolution of a critical segment of the dinarides alps connection kinematic and geochronological inferences from the medvednica mountains ne croatia the transition zone between the alps and dinarides is a key area to investigate kinematic interactions of neighboring orogens with different subduction polarities a study combining field kinematic and sedimentary data microstructural observations thermochronological data rb sr and fission track and regional structures in the area of medvednica mountains has revealed a complex polyphase tectonic evolution we document two novel stages of extensional exhumation the first stage of extension took place along a late cretaceous detachment following the late early cretaceous nappe stacking burial and greenschist facies metamorphism two other shortening events that occurred during the latest cretaceous oligocene were followed by a second event of extensional exhumation characterized by asymmetric top ne extension during the miocene top nw thrusting took place subsequently during the pliocene inversion of the pannonian basin the cretaceous nappe burial late cretaceous extension and the oligocene earliest miocene contraction are events driven by the alps evolution in contrast the latest cretaceous eocene deformation reflects phases of dinaridic contraction furthermore the miocene extension and subsequent inversion display kinematics similar with observations elsewhere in the dinarides and eastern alps all these processes demonstrate that the medvednica mountains were affected by alpine phases of deformations to a much higher degree than previously thought similarly with what has been observed in other areas of contractional polarity changes such as the mediterranean black sea or new guinea systems the respective tectonic events are triggered by rheological weak zones which are critical for localizing the deformation created by both orogens

misoriented faults in exhumed metamorphic complexes rule or exception abstract low angle normal faults and other weak faults are common in the metamorphic core of collisional orogens they frequently show a phyllosilicate rich mylonitic foliation that was reactivated under brittle conditions experimental and theoretical works indicate that mechanical anisotropies exert a substantial influence on shear failure and frictional sliding eventually inhibiting the nucleation and propagation of new andersonian shear fractures and favoring the localization of brittle failure along the pre existing foliations metamorphic phyllosilicate rich rocks may show a friction coefficient varying from 0 6 at high angles to the foliation to 0 2 0 4 for shear along the inherited foliation to test the influence of mechanical anisotropies on the development of non andersonian faults we have applied a modified slip tendency analysis to three misoriented phyllosilicate rich faults of the european alps the analysis accounts for anisotropy in friction coefficients and has been named anisotropic slip tendency analysis here we show that brittle deformation along misoriented phyllosilicate rich foliations is more probable than the development of new andersonian faults the presence of a well developed network of weak phyllosilicate rich faults may influence the overall structural style and mechanical properties of the brittle lithosphere in collisional orogens

constraining long term fault activity in the brittle domain through in situ dating of hydrothermal monazite sims th pb dating of hydrothermal fissure vein monazite ce has the unique potential to date multiple tectonic events under low grade metamorphic brittle ductile conditions over large time frames monazites ce from brittle fault systems in the eastern alps allow us to constrain their cretaceous activity over 20 ma within single crystals recording all major tectonic events eo alpine formation of the fluid filled fissure veins occurred 90 ma ago at 352 19 c and 342 42 mpa this corresponds to peak conditions during regional metamorphism of the cretaceous collisional nappe stacking several stages of dissolution reprecipitation recrystallization record fault activity between 84 and 70 ma corresponding fluid inclusions indicate conditions of 229 10 c and 143 20 mpa this correlates with the formation of sedimentary basins during post orogenic extension associated with strike slip movements the results strengthen the hypothesis that many large fault systems in the eastern alps developed during the cretaceous orogeny and became reactivated during neogene alpine tectonics

late cretaceous extension overprinting a steep belt in the northern calcareous alps schesaplana ratikon switzerland and austria the triassic to cretaceous sediment succession of the lechtal nappe in the western part of the northern calcareous alps nca has been deformed into large scale folds and crosscut by thrust and extensional faults during late cretaceous eoalpine and tertiary orogenic processes the following sequence of deformation is developed from overprinting relations in the field d1 nw vergent folds related to thrusting d2 n s shortening leading to east west trending folds and to the formation of a steep belt arlberg steep zone along the southern border of the nca d3 e w to ne sw extension and vertical shortening leading to low angle normal faulting and recumbent collapse folds like the wildberg syncline d1 and d2 are cretaceous in age and predate the eocene emplacement of the austroalpine on the penninic nappes along the austroalpine basal thrust the same is probably true for d3 finally the basal thrust was deformed by folds related to out of sequence thrusting these results suggest that the nca were at least partly in a state of extension during the sedimentation of the gosau group in the late cretaceous

tertiary cooling and exhumation history in the maramures area internal eastern carpathians northern romania thermochronology and structural data the tertiary kinematic history of the maramures area is constrained by integrating thermochronological fission track and uth he analysis data with field based structural investigations this study focuses on the tectonic evolution of the northern rim of the tisza dacia block during collision with the european margin cretaceous nappe stacking related metamorphism as well as late cretaceous exhumation are evidenced by zircon fission track data subsequent palaeogene to early miocene sedimentation led to burial heating and annealing of fission tracks in apatite final tectonic uplift was initiated during the convergence of tisza dacia with the european margin associated with transpressional deformation 16 to 12 ma this led to mid miocene exhumation recorded by apatite fission track cooling ages in the western part of the study area transtension between 12 and 10 ma caused brittle deformation along ew trending strike slip faults and swne trending normal faults delimiting blocks that were tilted towards the sw this fragmentation of the crust led to enhanced exhumation at rates of 1 mm a in the central part of the study area as is documented by middle to late miocene cooling ages 13 to 7 ma the outside estimate for the total amount of exhumation since middle miocene times is 7 km

controls on the δ13cdic and alkalinity budget of a flashy subtropical stream manoa river hawaii abstract hawaiian streams are flashy in nature because watersheds are small and steep and receive intense and unevenly distributed rainfall as a result stream chemistry is characterized by considerable spatiotemporal variability to examine how rainfall and streamflow affect the solute content of the manoa river in hawaii time series geochemical data collected during 17 sampling campaigns in spring fall of 2010 were evaluated in a coupled 13 c dic major ion inversion model spatially the stream is characterized by a distinct shift from a low hco 3 43 mg l low pco 2 3760 ppmv and heavy 13 c dic 6 5 fingerprint in the upper reaches to a high hco 3 91 mg l high pco 2 8961 ppmv and light 13 c dic 11 7 signature in the lowlands these trends are attributed to 1 progressive weathering of exposed aluminosilicates and 2 downstream enrichment in co 2 from organic matter decay in the soil zone solute i e nitrate yields from nitric acid weathering are generally low 13 c dic and rainfall rates in the mid stream section of the river which is consistent with an atmospheric co 2 dilution effect during high rainfall events this dilution effect needs to be accounted for to reliably describe the role of volcanic island river systems in global assessments of silicate weathering and co 2 degassing

dating fault generated pseudotachylytes comparison of 40ar 39ar stepwise heating laser ablation and rb sr microsampling analyses three different geochronological techniques stepwise heating laser ablation 40ar 39ar rb sr microsampling have been evaluated for dating fault generated pseudotachylytes sampled along the periadriatic fault system paf of the alps because pseudotachylytes are whole rock systems composed of melt clast and alteration phases chemical control from both ar isotopes cl k ca k ratios and empa analyses is crucial for their discrimination when applied to stepwise heating 40ar 39ar analyses this approach yields accurate melt related ages even for complex age spectra the spatial resolution of laser ablation 40ar 39ar analyses is capable of contrasting melt clast and alteration phases in situ provided the clasts are not too fine grained the latter of which results in integrated mixed ages without geological information elevated cl k and ca k ratios were found to be an invaluable indicator for the presence of clast admixture or inherited 40ar due to incomplete isotopic resetting during frictional melting rb sr microsampling dating did not furnish geologically meaningful ages on the basis of isotopic disequilibria among pseudotachylyte matrix phases and independent rb sr microsampling dating of cogenetic ultra mylonites the concordant 40ar 39ar pseudotachylyte ages are interpreted as formation ages the investigated pseudotachylytes altogether reveal a cretaceous to miocene history for the entire paf consistent with independent geological evidence individual faults however consistently reveal narrower intervals of enhanced activity lasting a few million years electronic supplementary material to this paper can be obtained by using the springer link server at http dx doi org 10 1008 s00410 002 0381 6

an illustration of the advantages of a complete texture analysis described by the orientation distribution function odf using quartz pole figure data abstract the preferred orientation of eight crystal directions of quartz was measured with an x ray texture goniometer for selected quartz bearing tectonites with a clear pattern of c axis preferred orientation the advantages of data analysis by means of calculations of the orientation distribution function and other forms of data presentation derived from the odf are demonstrated

inverse modeling of annealing of fission tracks in apatite 2 application to the thermal history of the peace river arch region western canada sedimentary basin

inner gorge slot canyon system produced by repeated stream incision eastern alps significance for development of bedrock canyons abstract many inner bedrock gorges of the alps show abrupt downstream changes in gorge width as well as channel type and gradient as a result of epigenetic incision of slot canyons many slot canyons also are associated with older gorge reaches filled with quaternary deposits the age of slot canyons and inner bedrock gorges however commonly is difficult to constrain for the inner bedrock gorge system of the steinberger ache catchment eastern alps active slot canyons as well as older abandoned gorge reaches filled with upper wurmian proglacial deposits record three phases of gorge development and slot canyon incision a 234u 230th age of cement of 29 7 1 8 ka in fluvial conglomerates onlapping the flank of an inner gorge fits with late wurmian valley bottom aggradation shortly before pleniglacial conditions in addition the age indicates that at least the corresponding canyon reach must be older during advance of ice streams in the buildup of the last glacial maximum lgm the catchment was blocked and a proglacial lake formed bedrock gorges submerged in that lake were filled with fluviolacustrine deposits during the lgm the entire catchment was overridden by ice during post glacial reincision streams largely found again their preexisting inner bedrock canyons in some areas however the former stream course was missed and a slot canyon formed the distribution of pleistocene deposits the patterns of canyon incision and the mentioned u th cementation age however together record a further discrete phase of base level rise and stream incision well before the lgm the present course of steinberger ache and its tributaries is a patchwork of 1 slot canyons incised during post glacial incision 2 vestiges of slot canyons cut upon an earlier middle to late wurmian cycle of base level rise and fall 3 reactivated reaches up to 200 m in width of inner bedrock gorge that are watershed at present and more than at least 30 ka in age and 4 abandoned sediment filled reaches of bedrock canyons that also must be older than 30 ka and that are exposed alongside the active streams multi cyclic bedrock canyon systems composed of reaches of markedly different ages may be common in mountain ranges subject to glaciations and or mass wasting

early holocene 8 6 ka rock avalanche deposits obernberg valley eastern alps landform interpretation and kinematics of rapid mass movement in the obernberg valley the eastern alps landforms recently interpreted as moraines are re interpreted as rock avalanche deposits the catastrophic slope failure involved an initial rock volume of about 45 million m with a runout of 7 2 km over a total vertical distance of 1330 m fahrboschung 10 36cl surface exposure dating of boulders of the avalanche mass indicates an event age of 8 6 0 6 ka a 14c age of 7785 190 cal yr bp of a palaeosoil within an alluvial fan downlapping the rock avalanche is consistent with the event age the distal 2 km of the rock avalanche deposit is characterized by a highly regular array of transverse ridges that were previously interpreted as terminal moraines of late glacial jigsaw puzzle structure of gravel to boulder size clasts in the ridges and a matrix of cataclastic gouge indicate a rock avalanche origin for a wide altitude range the avalanche deposit is preserved and the event age of mass wasting precludes both runout over glacial ice and subsequent glacial overprint the regularly arrayed transverse ridges thus were formed during freezing of the rock avalanche deposits

structural evolution of an antiformal window the scheiblingkirchen window eastern alps austria abstract the scheiblingkirchen window a lower austroalpine tectonic window at the eastern margin of the eastern alps austria was formed during late cretaceous continent continent collision structural investigations including structural mapping microstructural studies and texture analysis revealed a decompression related three stage tectonic history of lower austroalpine units during the formation of the scheiblingkirchen window 1 intra lower austroalpine nappe stacking was by top to the n out of sequence thrusting of the kirchberg fold nappe over the wechsel nappe under lower greenschist facies metamorphic conditions the structural expression of the stacking event d1 comprises a penetrative foliation containing a n s trending stretching lineation isoclinal recumbent folds trending subparallel to the stretching lineation and ultramylonites quartz and calcite microstructures indicate that dynamic recrystallization processes accompanied deformation their commonly moderately developed lattice preferred orientation record dominant slip on the prism and rhomb planes parallel to a 2 subsequent exhumation of previously stacked rocks is related to the formation of foliation parallel mylonitic shear zones within an e w extensional regime d2 microstructures and textures suggest similar deformation temperatures during thrusting and extension 3 a superimposed phase of nw se oriented horizontal shortening d3 was accommodated by large and small scale upright folding of the area around ne sw trending axes and by backthrusting leading to the antiformal doming of the scheiblingkirchen window subsequent subvertical flattening resulting from the shortening phase led to the formation of ne sw trending outcrop scale open recumbent folds low temperature deformation conditions as inferred from the low degree of recrystallization of quartz and calcite aggregates and the dominance of glide on the basal planes point to a cooling related deformation event

evidence for east west crustal extension in the eastern alps implications for the unroofing history of the tauern window the contact between the western border of the tauern window and the overlying austroalpine nappes austria and italy is marked by a structural petrologic and geochronologic discontinuity that developed in the early stages of unroofing of the window within the window pressure temperature time paths j selverstone 1985 indicate that significant ductile thinning occurred shortly after the cessation of thrusting paleocene eocene sense of shear indicators rotated porphyroblasts asymmetric augen and pressure shadows s c fabrics associated with a west plunging stretching lineation indicate that this thinning occurred in response to top to the west low angle normal shear during metamorphism the same sense of normal shear is present in the mesozoic members of the austroalpine sequence west of the window in these rocks however west directed shear occurred at low temperatures 300 c after the thermal peak of metamorphism structural data and the regional geometry imply that the western end of the tauern window is a low angle normal fault brenner line that juxtaposed brittlely deformed rocks of the austroalpine nappes against more ductilely deformed rocks from the window biotite k ar and rb sr data suggest a miocene age for final movement on the brenner line these data indicate a prolonged history of east west extension in the eastern alps that affected all crustal levels early ductile thinning of lower crust followed by mid to upper crustal low angle normal faulting a model is presented that relates the young east west extension to displacement transfer from dextral movement on the periadriatic lineament in this model the brenner line and by analogy the simplon line can be thought of as detachment faults that tectonically unroofed the tauern window and lepontine thermal highs respectively