dating the quaternary progress in luminescence dating of sediments abstract luminescence dating comprises a collection of numerical age techniques that are among the most significant chronological tools currently used in quaternary research this paper briefly reviews the key historical developments in luminescence dating from its roots in thermoluminescence dating of heated minerals to the development of optical dating methods for sunlight exposed sediments we describe the principles and practicalities of the various techniques commonly used in luminescence dating including multiple aliquot single aliquot and single grain procedures and we discuss some of the latest approaches to recognising and minimising potential errors in age estimation e g by means of component analysis and dose distribution methods in optical dating the overview also introduces the other papers in this special issue of quaternary science reviews which address a selection of important issues in basic research technique development and application of luminescence dating to critical questions in the geological and archaeological sciences illustrated with examples from around the world and the last million years of earth history

tectono metamorphic evolution of a nappe stack a case study of the swiss alps fold and thrust belts are prominent structures that occur at the front of compressional orogens to unravel the tectonic and metamorphic evolution of such complexes kinematic investigations quantitative microstructural analysis and geothermometry calcite graphite calcite dolomite were performed on carbonate mylonites from thrust faults of the helvetic nappe stack in central switzerland paleo isotherms of peak temperature conditions and cooling stages fission track of the nappe pile were reconstructed in a vertical section and linked with the microstructural and kinematic evolution mylonitic microstructures suggest that under metamorphic conditions close to peak temperature strain was highly localized within thrust faults where deformation temperatures spatially continuously increased in both directions from n to s within each nappe and from top down in the nappe stack covering a temperature range of 180 380 c due to the higher metamorphic conditions thrusting of the lowermost nappe the doldenhorn nappe was accompanied by a much more pronounced nappe internal ductile deformation of carbonaceous rock types than was the case for the overlying wildhorn and gellihorn nappes ongoing thrusting brought the doldenhorn nappe closer to the surface the associated cooling resulted in a freezing in of the paleo isotherms of peak metamorphic conditions contemporaneous shearing localized in the basal thrust initially still in the ductile deformation regime and finally as brittle faulting and cataclasis inducing ultimately an inverse metamorphic zonation with ongoing exhumation and the formation of the helvetic antiformal nappe stack a bending of large scale tectonic structures thrusts folds peak temperature isotherms and cooling isotherms occurred while this local bending can directly be attributed to active deformation underneath the section investigated up to times of 2 3 ma a more homogeneous uplift of the entire region is suggested for the very late and still active exhumation stage

igneous and metamorphic petrology of the eclogitic seljeneset meta anorthosite and related jotunites western gneiss region norway abstract the seljeneset meta anorthosite consists of deformed and metamorphosed anorthosite and mafic rocks is situated in the high grade western gneiss region wgr of norway and is adjacent to the 1 52 ga flatraket quartz monzonite mangerite the wgr was metamorphosed to eclogite fades during caledonian tectonism 414 16 ma ago the meta anorthosite contains 46 57 wt sio 2 and displays chondrite normalized ree patterns typical of anorthosite indicating that metamorphism did not significantly affect ree abundances norms indicate that igneous anorthosite consisted of 90 modal plagioclase minor mafic silicates and 1 fe ti oxide mafic rocks 43 48 wt sio 2 are rich in total fe 2 o 3 13 20 tio 2 3 4 and p 2 o 5 1 3 poor in cr jotunites which are characteristic of proterozoic anorthosite mangerite complexes jotunite originally consisted of 50 modal andesine 25 mafic silicates 10 fe ti oxide and up to 7 apatite ree patterns of jotunite are highly variable which reflects variable igneous abundances and modification by metasomatism filter pressing of residual liquid trapped between cumulus plagioclase may have been important in the evolution of anorthosite and jotunite anorthosite contains ultramafic xenoliths high mgo cr and ni and depleted in lree which suggests that some mantle derived peridotite was present in the baltic crust by mid proterozoic time this may extend the crustal history of norwegian garnet peridotites by over one billion years seljeneset rocks display evidence of retrogression from eclogite through amphibolite facies meta anorthosite consists of ovoidal clots of margarite quartz plagioclase and relict kyanite set in a matrix of zoisite clinozoisite plagioclase quartz hornblende and biotite phase equilibria analysis of sequential assemblages shows that meta anorthosite records a retrograde p t path from 15 17 kbar to 4 3 8 2 kbar at 450 600 c mafic rocks vary from moderately well preserved eclogite through varieties containing symplectite to dynamically recrystallized amphibolite in one sample the rare na ca amphibole magnesio alumino taramite appears to be part of the eclogite assemblage calculations indicate eclogite formation at p 16 18 kbar at 750 c some mafic rocks contain veins and segregations of biotite muscovite pyrite allanite and zircon that considered together with geochemical data indicate metasomatic introduction of k rb ba ga s and rare earth and other high field strength elements by channelized fluids during retrogression the seljeneset meta anorthosite associated jotunites and adjacent flatraket quartz monzonite likely constitute a single complex here named the nordpollen plutonic complex this complex was emplaced 1 52 ga ago metamorphosed to eclogite facies during silurian continent continent collision largely retrograded to amphibolite facies during uplift of the orogen and locally metasomatised during retrogression

a geothermobarometric investigation of garnet peridotites in the western gneiss region of norway in the western gneiss region of norway are found numerous peridotite lenses which have been extensively recrystallized under amphibolite fades conditions during the caledonian orogeny however evidence for an earlier caledonian high pressure metamorphism has been recorded by abundant eclogite and granulite relicts within gneiss and by the presence of at least ten garnet perioditite bodies preserved within chlorite peridotites two garnet bearing ultramafic assemblages have been recognized olivine orthopyroxene clinopyroxene garnet and olivine ortho pyroxene pargasitic amphibole garnet

petrological constraints and pt path of devonian collapse tectonics within the scandian mountain belt western gneiss region norway in norway post caledonian extension controlled the formation and sedimentation of middle devonian sedimentary basins these collapse basins were deposited along a low angle extensional detachment fault on top of caledonian high grade metamorphic rocks of the western gneiss region this paper concerns the petrological analysis of eclogite and high pressure micaschist collected within the extensional shear zone study of gneisses and micaschists surrounding these high pressure rocks allows description of the complete pt path which characterized this area application of appropriate geothermometers and geobarometers confirms that the retrograde evolution following high pressure conditions ll 15kbar at 500 600 c was characterized by nearly isothermal decompression followed by amphibolite facies metamorphism the shape of the pt path is compared with theoretical models of thermal evolution of continental orogenic crust during uplift we can observe an increase in temperature during the first stages of decompression smaller than predicted by the models considering the evidence for extensional tectonic in the study area we propose to explain such a small increase in temperature during the decompression by the intervention of extension which accelerates the collapse process and reduces the late orogenic heating of the caledonian thickened crust

the equatorial response to higher latitude forcing abstract the classic view following charney and webster and holton is that significant midlatitude forcing of the tropics can be expected only in regions with westerly winds in the upper troposphere because it is only in these regions that stationary rossby waves will be able to propagate toward the equator here it is shown that higher latitude forcing can project directly onto equatorial waves and give a significant tropical response in both easterly and westerly tropical flow the equatorial response to higher latitude forcing is considered in the context of a dry atmosphere and a localized higher latitude forcing with eastward or westward phase speed previous ideas of the doppler shifting of equatorial waves by zonal flows are extended to include consideration of a forcing involving a range of zonal wavenumbers a gill type model suggests that there can be significant forcing of equatorial waves by either vorticity forcing or heating in higher latitudes in agreement with the theory the kelvin wav

recent crustal movements in switzerland and their geophysical interpretation abstract in this paper a review is presented on the most recent results of geodetically determined recent crustal movements in switzerland these data are compared with the new bouguer gravity map of switzerland and an attempt is made to discuss the geodetic and gravity results in connection with the crustal structure of the swiss alps in terms of seismic compressional wave velocities and depths to the crust mantle boundary

pre caledonian granulite and gabbro enclaves in the western gneiss region norway indications of incomplete transition at high pressure the western gneiss region of norway is a continental terrane that experienced caledonian high pressure and ultrahigh pressure metamorphism most rocks in this terrane show either peak caledonian eclogite facies assemblages or are highly strained and equilibrated under late caledonian amphibolite facies conditions however three kilometre size rock bodies flatraket ulvesund and krakenes in outer nordfjord preserve pre caledonian igneous and granulite facies assemblages and structures where these assemblages are preserved the rocks are consistently unaffected by caledonian deformation the three bodies experienced high pressure conditions 20 23 kbar but show only very localized about 5 eclogitization in felsic and mafic rocks commonly related to shear zones the preservation of pre caledonian felsic and mafic igneous and granulite facies assemblages in these bodies therefore indicates widespread 95 metastability at pressures higher than other metastable domains in norway late caledonian amphibolite facies retrogression was limited the degree of reaction is related to the protolith composition and the interaction of fluid and deformation during the orogenic cycle whereby metastability is associated with a lack of deformation and lack of fluids either as a catalyst or as a component in hydration reactions the three bodies appear to have been far less reactive than the external gneisses in this region even though they followed a similar pressure temperature evolution the extent of metastable behaviour has implications for the protolith of the western gneiss region for the density evolution of high pressure terranes and hence for the geodynamic evolution of mountain belts

the swiss alps and their peripheral foreland basin stratigraphic response to deep crustal processes 1 this paper gives a synoptic view of the cenozoic evolution of the swiss alps and their northern foreland basin in this orogen deep crustal processes subduction nappe stacking underplating and exhumation are intimately linked with surface processes surface uplift erosion basin formation and basin axis migration within the foreland basin the spatial pattern of subsidence and alluvial fan construction suggests that an increase in flexure of the foreland plate and the creation of relief in the orogen migrated from east to west in the course of collision in the orogen itself crustal thickening involved lower crust of the adriatic margin in the east and the european margin in the west exhumation of upper crustal units occurred earlier in the east as compared with the west an adriatic mantle wedge the ivrea body and its associated wedge of lower crustal material are identified as an extra lithospheric load which contributed to downward flexure of the european plate as a result of enhanced subsidence of the foreland plate relief was generated presumably in order to adjust to critical taper geometry it appears therefore that the westward motion of the adriatic wedge ultimately caused the contemporaneous westward propagation of the location of enhanced rates of alluvial fan construction coeval strike slip and n s convergence juxtaposed the adriatic wedge sequentially to different european upper crustal units which resulted in different styles of crustal structure and evolution along strike within the orogen

calcite twins their geometry appearance and significance as stress strain markers and indicators of tectonic regime a review twin lamellae are a widespread feature in calcites of any type and origin twinning in calcite is an important intracrystalline deformation mechanism with low critical resolved shear stress and virtually no temperature dependence in contrast to most slip systems in rock forming minerals twinning therefore permits intracrystalline deformation at very low temperature and very little confining pressure twinning alone however cannot lead to large strains because only one independent slip system is effectively available twins lead to discontinuous shearing on the grain scale which gives rise to considerable strain incompatibilities at grain boundaries twinning consequently leads to strain hardening detailed observations of the geometry of twin lamellae show that incompatibilities at grain boundaries are eliminated by pressure solution on the grain scale at low temperature and dynamic recovery processes at higher temperatures twins are found in various tectonic environments and record very small strains in rocks deformed under very little cover different twinning strain and twinning stress methods and palaeopiezometers are critically reviewed all methods are limited to strains of less than 15 shortening or extension by twinning twinning nevertheless is an important although not directly measurable contribution to the total strain in highly strained calcite rocks at least up to middle greenschist facies under which conditions it is the most effective contributor to the formation of strong lattice preferred orientations in calcite tectonites the appearance of calcite twin lamellae changes systematically as a function of deformation temperature micro twins and straight narrow 1 5 m but fewer twins are developed above approximately 200 c curved twins twinned twins and completely twinned grains indicate the progressive importance of other slip systems and larger intracrystalline strains are possible at ca 250 c and above ancient straight twin lamellae are modified into irregular geometries by recrystallization and grain boundary migration the appearance of calcite twins is proposed as an approximate but rapid and easy to use geothermometer in low temperature environments

trying to understand alpine sediments before 1950 abstract most alpine geologists before and after the 1893 1902 breakthrough of the nappe theory paid surprisingly little attention to sedimentological phenomena they were preoccupied with stratigraphic and especially tectonic problems the alpine concept of geosyncline differed in several ways from the original one in 1894 marcel bertrand suggested a fourfold division of complexes informal lithostratigraphic assemblages among the sediments of the alps and of older mountain chains for the alps his classification may be expanded to comprise i late variscan detritals ii pre rift platform sediments iii syn rift deposits iv post rift platform and basin sediments v starved deep sea formations on oceanic or thinned continental crust vi bundnerschiefer or schistes lustres vii flysch and viii molasse the last named is not discussed here on the european helvetic margin the processes giving rise to shallowing upward sequences of condensed glauconite beds shales and limestones complex iv were discussed for a long time the work of arnold heim is particularly instructive gustav steinmann was one of the first to recognize the deep sea origin of certain rocks especially radiolarian cherts the controversy on the bathymetry of the alpine seas during the oceanic and post oceanic stages complexes v vii went on until about 1950 since 1916 the seas and islands around eastern indonesia were proposed as analogues to the late mesozoic paleogeographic pattern of the alps two 18th century scientists deserve a special mention moritz anton kappeler m a cappellerius 1767 provided an actualistic interpretation of ripple marks on steep standing sandstones and johann jacob scheuchzer 1718 understood the importance of graded bedding which he attributed to the action of the deluge

some remarks about a new last glacial record from the western salzach foreland glacier basin southern germany the amount of glacial advances into the alpine foreland during the pleistocene is still a matter of discussion the big four glaciations of the classical approach were originally derived from outwash sequences from glacial basins only very few long records and studies are known in the context of a geological mapping programme of the bavarian environment agency a research drilling through the salzach foreland glacier area was undertaken continuous coring reached the base of the glacial basin sequence 117 m below surface geological and geophysical logging pollen sampling and dating attempts of core material were conducted while age constraints for the lower part of the sequence are still uncertain the upper part can be ascribed to the last glacial cycle the interpretation of diamictons from the early part of the last glacial cycle is discussed a validation compared to other stratigraphic observations and interpretations from northern alpine quaternary records is presented

combining natural microstructures with composite flow laws an improved approach for the extrapolation of lab data to nature so far rheological predictions that are based on experimentally derived flow laws appear inconsistent with microstructural observations in natural calcite mylonites because grain size sensitive gss diffusion creep is predicted while microstructural criteria suggest grain size insensitive gsi dislocation creep as the dominant deformation mechanism a way out of this discrepancy between experiment and nature can be found by combining full grain size distributions with composite gsscgsi flow laws we applied this approach to natural carbonate mylonites from the helvetic alps switzerland for steady state microstructures our calculations indicate an increasing gss component with increasing temperature at geologically constrained strain rates of 10 k10 10 k11 s k1 the modeling results are consistent with microstructural observations of the natural mylonites in these rocks dynamically steady state microfabrics show a systematic change in grain size grain size distribution and grain aspect ratio with temperature while crystallographic preferred orientations remain of similar strength when single value mean grain sizes are used rather than grain size distributions rheological modeling fails to give reasonable results further paleostresses estimated from conventional recrystallized grain size piezometers were found to be unrealistically high but were reduced to 80 100 mpa when results of the composite modeling were used hence combining composite flow laws with microstructural data from natural mylonites forms a promising approach for a better extrapolation of experimental data to nature and therefore provides new insight into changes in rheology during large scale geodynamic processes q 2005 elsevier ltd all rights reserved

combining amphibious geomorphology with subsurface geophysical and geological data a neotectonic study at the front of the alps bernese alps switzerland abstract in the vicinity of lake thun at the front of the bernese alps switzerland we performed a multidisciplinary neotectonic study combining onshore and offshore geological data and geophysical measurements in order to identify potentially active fault structures paleoseismic reconstructions on the northern margin of the alps have documented several strong earthquakes with moment magnitudes 6 during the late quaternary which have long recurrence intervals of 1 000 to 2 000 years such earthquakes are expected to produce surface ruptures in this light we investigated the study area located near lake thun primarily for on fault evidence to date still a shortcoming in switzerland we detected several features indicating potential fault activity such as aligned subaquatic morphological depressions offset horizons observed in reflection seismic profiles of lake sediments and in ground penetrating radar images all delineating a fault trace observations of fluvial deposits in a nearby gravel pit in the prolongation of the inferred structure supports these findings a narrow zone with rotated long axes of pebbles inclining at 60 is clearly distinguishable and crosscuts the original bedding with predominantly horizontal orientation of pebble axes this zone further shows an apparent 1 1 m offset of oxidized horizons and is therefore considered as a potential fault plane in a normal faulting regime a dated radiocarbon age of 11 000 years bp of the gravel deposits hence suggests a younger fault activity during the holocene the einigen fault zone efz proposed on the basis of these observations is considered as a complex fault system with a combination of dextral strike slip and normal faulting as suggested by gpr images observations in the gravel pit and radar data independently show that it includes at least two fault strands however while five earthquakes with epicentral intensities i 0 vi and numerous smaller seismic events are known within less than 30 km epicentral distance to lake thun over the past 400 years none of these seem to coincide with the location of the efz

the evolution of the hornelen basin detachment system western norway implications for the style of late orogenic extension in the southern scandinavian caledonides abstract the geology of the devonian hornelen basin and the surrounding western gneiss region wgr western norway has been examined in detail structural clast provenance and geothermobarometric data have been combined to reconstruct the motion history of part of a major late orogenic extensional shear zone in the southern scandinavian caledonides the nordfjord sogn detachment nsd the nsd in the hornelen basin area is a zone of mylonites 4 6 km thick tectonostratigraphically constrained within the lower and middle allochthons lma and the uppermost part of the wgr it separates eclogite bearing gneisses of the wgr from greenschist and amphibolite facies rocks of the middle and upper allochthons marking a profound metamorphic break and indicating major excision of crustal section kinematic indicators give a consistent top to the west shear sense indicating a reversal of the movement sense of the scandian nappes with the ductile strain being distributed through the entire lma section the wgr was exhumed from depths of up to 100 km in the footwall of the shear zone partly aided by pure shear vertical flattening below the nsd and extension and erosion of the hanging wall the majority of the movements on the nsd in the hornelen basin area occurred under amphibolite facies conditions prior to 410 ma subsequent shear caused limited greenschist retrogression along extensional crenulation cleavages depending on interpretation of mica 40 ar 39 ar ages this lower grade shearing may be due to a continuation of movements or renewal of motion associated with opening of the hornelen basin at about 385 ma the lack of clear evidence of penetrative greenschist facies mylonites in the hornelen area may be due to the faulted omission of tectonites of this grade following scandian a subduction and eclogite facies metamorphism at 425 ma the p t t path of the wgr shows very rapid decompression associated with early slip on the extensional detachment horizons unroofing was initially near isothermal followed by a phase of rapid near isobaric cooling after 410 ma decompression and cooling slowed as slip on the nsd slowed or even ceased by the middle devonian the wgr lay at about 10 15 km depth and the crust had almost returned to isostatic equilibrium at this time a brittle fault splaying from the nsd ramped upwards through the upper allochthon opening a scoop shaped west facing half graben the hornelen basin a further 50 km of heave on the nsd occurred during alluvial infilling of the basin subsequently the basin fill was folded by late devonian n s compression and the basin margins were modified by mesozoic faulting these features are consistent with an orogenic collapse model for southern scandinavia that involves large scale backsliding of the scandinavian caledonides within tectonostratigraphic units by this mechanism the baltic shield could have been efficiently unloaded with tectonic translations producing significant metamorphic breaks within a seemingly preserved tectonostratigraphic sequence the model favours orogenic collapse driven by an external pull rather than internal body forces

metamorphic evolution of kyanite staurolite bearing epidote amphibolite from the early palaeozoic oeyama belt sw japan early palaeozoic kyanite staurolite bearing epidote amphibolites including foliated epidote amphi bolite fea and nonfoliated leucocratic or melanocratic metagabbros lmg mmg occur in the fuko pass metacumulate unit fpm of the oeyama belt sw japan microtextural relationships and mineral chemistry define three metamorphic stages relict granulite facies metamorphism m1 high p hp epidote amphibolite facies metamorphism m2 and retrogression m3 m1 is preserved as relict al rich diopside up to 8 5 wt al2o3 and pseudomorphs after spinel and plagioclase in the mmg suggesting a medium p granulite facies condition 0 8 1 3 gpa at 850 c an unusually low variance m2 assemblage hbl czo ky st pg rt ab crn occurs in the matrix of all rock types the presence of relict plagioclase inclusions in m2 kyanite associated with clinozoisite indicates a hydration reaction to form the kyanite bearing m2 assemblage during cooling the corundum bearing phase equilibria constrain a qualitative metamorphic p t condition of 1 1 1 9 gpa at 550 800 c for m2 the m2 minerals were locally replaced by m3 margarite paragonite plagioclase and or chlorite the breakdown of m2 kyanite to produce the m3 assemblage at 0 5 gpa and 450 500 c suggests a greenschist facies overprint during decompression the p t evolution of the fpmmay represent subduction of an oceanic plateau with a granulite facies lower crust and subsequent exhumation in a pacific type orogen

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

circumglobal teleconnections the jet stream waveguide and the north atlantic oscillation abstract monthly and seasonally averaged upper tropospheric northern hemisphere winter fields are examined to determine whether the waveguiding effect of the time averaged tropospheric jets on low frequency disturbances that is predicted by theory does affect the behavior of these disturbances it is found that indeed disturbances in the vicinity of the mean jets particularly the jet that stretches across south asia are fundamentally different from those that reside in regions where the mean winds have weaker meridional gradients like the mid pacific patterns of variability in the jets tend to be smaller scale and to consist of zonally oriented chains of anomalies while variability in the mid pacific is composed of patterns with distinct meridional orientation because they are meridionally trapped and zonally elongated patterns associated with the jet stream waveguide connect activity at points that are much farther apart than do patterns in other regions of the globe within the south asian waveg

two early holocene rock avalanches in the bernese alps rinderhorn switzerland abstract large rock avalanches constitute a critical process modulating the evolution of alpine landscapes however the relatively infrequent occurrence of these high magnitude events makes identifying underlying process controls challenging here we describe two rock avalanches in the rinderhorn area of the bernese alps switzerland providing new mapping of rock avalanche source areas and deposits refined volume estimates for each event runout modeling back analyses and absolute age constraint from cosmogenic 36 cl surface exposure dating results reveal that the daubensee rock avalanche released 4 million m 3 of limestone sliding from the western crest of the rinderhorn debris ran out across a lateglacial moraine before reaching the valley bottom and spreading leaving thin on average 7 m deposits across a broad area the runout resulted in a fahrboschung angle of 21 part of the deposit now lies beneath lake daubensee the klein rinderhorn rock avalanche released 37 million m 3 of limestone along a dip slope sliding plane with a maximum runout distance of 4 3 km and estimated fahrboschung angle of 14 deposits bulked to 47 million m 3 running up the opposing slope with distinct hummocky morphology in the proximal area and a distal longitudinal flow ridge these deposits were later modified and partly obscured by ice avalanches from the nearby altels peak cosmogenic 36 cl surface exposure dating revealed nearly coincident ages for both rock avalanches of 9 8 0 5 ka the large lag time between local deglaciation and failure suggests that the events were not directly triggered by deglaciation rather the concurrent exposure ages also coinciding with the nearby kander valley rock avalanche as well as paleoseismic records from nearby lakes strongly suggest seismic triggering

semiautomated georadar data acquisition in three dimensions under favorable conditions georadar techniques can provide vivid images of the shallow subsurface 10 50 m although the significant advantages of 3 d georadar surveying strategies are well documented they generally require much greater expenditures than traditional 2 d approaches we introduce an efficient semiautomated 3 d georadar acquisition and processing scheme that does not jeopardize data quality a standard georadar acquisition unit is integrated with an innovative self tracking laser theodolite with automatic target recognition capabilities georadar and coordinate data are recorded simultaneously as the georadar antennae are transported steadily across a survey area while tracking a target prism mounted between the antennae the theodolite provides real time coordinate information with high accuracy in all directions at 1 m s moderate walking speed the coordinates are determined to better than 0 04 m and at 3 m s they are better than 0 07 m subsequent to acquisition semiautomati

the metamorphic evolution of the high pressure mafic granulites of the bacariza formation cabo ortegal complex hercynian belt nw spain abstract the high pressure mafic granulites of the bacariza formation outcrop in the two uppermost structural units of the cabo ortegal complex la capelada unit and cedeira unit were separated by a variscan thrust in both cases they appear as heterogeneous metabasites in normal contact between ultramafic rocks and other more homogeneous and less differentiated metabasic rocks also affected by catazonal metamorphism the main difference between the mafic granulites in the two units is the degree of deformation which is higher in the underlying cedeira unit petrologie and mineralogical data indicate that the high pressure hp granulites gt cpx amp pl qtz scp rt ilm czo are already retrograde m2 stage post dating an earlier eclogite facies metamorphism ml stage characterised by the mineral associations gt cpx amp ky qtz rt and gt cpx amp qtz zo rt the main structure relatted to the exhumation processes is the development of a general mylonitic foliation that although initiated in granulite facies conditions was mainly equilibrated in amphibolite facies m3 stage this foliation was affected by isoclinal folds which led to the formation of the variscan thrusts responsible for the present stacking position thrust conditions were transitional between amphibolite and greenschist facies m4 stage thermobarometric data point to different p t exhumation paths in the two units estimated p t conditions were higher in la capelada unit during ml p 13 kbar 860 c and m2 15 kbar 800 c than in the cedeira unit ml p 11 kbar 770 c m2 12 kbar 750 c temperatures for the m3 stage were comparable 720 c in both units but rocks from the cedeira unit show a much bigger drop in pressure this resulted in an isothermal decompression type path for the cedeira unit while both p and t decreased more steadily in la capelada rocks these were always located at deeper level than the cedeira rocks before the variscan stacking the difference in the two paths is related to different exhumation rates higher in rocks from the cedeira unit than in those from la capelada exhumation processes coeval with underthrusting and a different location of the rocks with respect to the main shear zone responsible for the exhumation would account for the distinct paths

neogene to ongoing normal faulting in the inner western alps a major evolution of the late alpine tectonics 1 widespread brittle extension occurs in the internal zones of the southwestern alps forming a dense fault network which overprints the compressional structures the extension has been followed by transcurrent motions in terms of paleostress this extension is radial to the belt close to the crustal penninic front and multidirectional in the eastern part of the internal zones the paleostress field of the strike slip phase is coherent with the extensional one and compatible with dextral shear along longitudinal faults globally we propose that the internal zones of the southwestern alps underwent a single neogene transtensive tectonic regime to strengthen our structural results the current tectonics has been analyzed using seismotectonic tools this approach allowed the recognition of several active faults moreover the ongoing tectonics is coherent with the observed brittle deformation the fault network controls the present day seismicity the combined seismotectonic and structural approaches give coherency and continuity from the neogene to ongoing extensional tectonics in the southwestern alps in the framework of the whole western alps a synthesis of our results with neotectonic related data allowed us to provide an accurate map of the neogene to present kinematics of the belt extension which appears as a major feature of the internal zones has been coeval with the propagation of thrusts in the outer zones during neogene times the geodynamic processes which rule this major tectonic evolution of the belt remain a matter of debate

the effect of thermal transfer on the zeroing of the luminescence of quartz from recent glaciofluvial sediments abstract the natural optically stimulated luminescence osl response of quartz grains extracted from a range of recent glaciofluvial and other glaciogenic sediments from western greenland is presented all samples were deposited within the last 10 years many only days or hours before collection consequently we would expect to measure zero or very small d e values had optical resetting of the osl signal been complete in the case of most samples d e values in the range 0 5 10 gy are observed while higher values are observed for a handful of samples however the regenerated osl growth curves constructed after daylight exposure of at least several hours also show large apparent d e values negative x axis intercepts corresponding samples from four different locations in the indian himalaya display similar osl characteristics the measurement of several regenerated osl growth curves omitting the preheat procedure which normally precedes osl measurement confirms that a significant degree of thermal transfer is occurring during the preheating it is this thermal transfer of charge during the preheat which is responsible for a significant contribution to the large apparent d e values observed for the regenerated osl growth in this paper we describe combined osl and tl measurements which have been used to monitor the charge transfer in detail for one sample an attempt is made to describe the charge transfer behaviour and we discuss methods appropriate to eliminating the unwanted effects of this phenomenon during osl dating preliminary results from the application of these techniques are presented and the implications of these observations for the osl dating of glaciogenic sediments are discussed

mineralogical kar stable and sr isotope systematics of k white micas during very low grade metamorphism of limestones helvetic nappes western switzerland abstract mineralogical k ar rb sr and stable isotope analyses have been carried out on k white micas from helvetic malm limestones in order to examine their evolution during very low to low grade alpine metamorphism associated with intense ductile deformation metamorphic temperatures were estimated at 300 c from stable isotopes quartz calcite thermometry occurrence of chloritoid and epizonal illite crystallinity index k white micas consist of variable mixtures of 2m 1 phengite and muscovite as revealed by detailed x ray diffraction analyses using peak decomposition of the 060 331 spectra k ar apparent ages display a strong grain size dependence in which mainly fine grained size fractions m record alpine ages 37 15 ma however these ages provide a relative rather than an absolute chronology of the diachronous alpine metamorphic evolution of the helvetic nappes the resetting of the k ar isotopic system of k white micas to alpine metamorphic conditions reflects an apparent combination of crystallization recrystallization and radiogenic 40 ar diffusion loss the oxygen isotope compositions of micas 15 to 22 are intermediate between detrital and 18 o enriched values expected for micas neoformed within an abundant marine carbonate matrix no isotopic equilibrium has been reached between calcite and micas the variable depletion of hydrogen isotope compositions 126 to 82 is influenced by the interaction with organic matter under closed system conditions organic matter if not removed may also represent a serious source of error in k ar age determination by introducing radiogenic 40 ar contamination 87 sr 86 sr isotope ratios of micas range from 0 70879 to 0 70902 with one outlier at 0 71794 the low values reflect sr exchange with calcite occurring during crystallization recrystallization of micas under closed system conditions

40ar39ar whole rock dating and the age of cleavage in the finnmark autochthon northernmost scandinavian caledonides abstract four variably cleaved samples of red shale slate were collected from the nyborg formation vestertana group exposed in the finnmark autochthon northernmost scandinavian caledonides quartz normalized illite crystallinity values suggest metamorphism varied between upper diagenesis lower anchizone east and lower anchizone middle anchizone west the samples display similarly discordant 40 ar 39 ar whole rock age and k ca spectra with total gas ages ranging between 606 and 661 ma spectra complexity is a result of evolution of gas from relatively non retentive chlorite white mica and relatively refractory detrital plagioclase apparent ages defined by intermediate temperature increments are relatively constant within each sample but show marked intersample variations 550 575 to 635 650 ma three size fractions 1 2 2 4 and 4 8 m were separated from the sample containing the least chlorite the two coarser fractions contain numerous rock fragments and display 40 ar 39 ar age and k ca spectra similar to the whole rock the 1 2 m fraction is largely comprised of individual mineral grains gas increments evolved between 375 and 495 c record similar k ca ratios but systematically increasing apparent ages between 637 and 783 ma these results suggest that the 1 2 m fraction is composed of detrital white mica grains which were affected by a diagenetically related geologic disturbance at 635 ma although the affects of a late cambrian early ordovician orogenic event finnmarkian orogeny have been locally described from portions of the overlying caledonian allochthons no clear record of correlative tectonothermal activity has been documented within samples from the finnmark autochthon

monsoons and the dynamics of deserts the existence of subtropical deserts such as the sahara has often been attributed to the annual mean zonal mean hadley circulation which shows strong descent in the subtropics however the zonal mean hadley circulation shows considerable evolution over the course of the year with very strong subtropical descent during winter but practically no zonal mean subtropical descent during summer when rainfall over the eastern sahara and the mediterranean is least charney 1975 proposed a biosphere albedo feedback mechanism whereby local anthropogenic effects related to over grazing could affect the radiative balance enhancing summertime diabatic descent and leading to desertification of the subtropics in general the present study which uses an idealized model suggests a monsoon desert mechanism for desertification whereby remote diabatic heating in the asian monsoon region can induce a rossby wave pattern to the west integral with the rossby wave solution is a warm thermal structure that interacts with air on the southern flank of the mid latitude westerlies causing it to descend this adiabatic descent is localized over the eastern sahara and mediterranean and over the kyzylkum desert to the south east of the aral sea by the mountains of north africa and south west asia trajectories indicate that the monsoon desert mechanism does not represent a simple walker type overturning cell instead the descending air is seen to be mainly of mid latitude origin it is speculated that the monsoon forced adiabatic descent may result in clear air and therefore a local diabatic enhancement which effectively doubles the strength of descent with this mechanism desertification can be forced by remote changes in monsoon strength rather than by local effects this conclusion is supported by the observed dramatic strengthening of descent over the mediterranean and east sahara during the onset of the asian monsoon and on the longer timescale by relating prehistoric lake levels to milankovitch monsoon forcing the latter may help to explain the perceived discrepancies between the palaeoclimate of the eastern sahara and the strength of a tropic wide monsoon the monsoon desert mechanism may not be confined to the asian monsoon alone and the existence of other monsoon climate regions over the globe may in a similar way explain the observed summertime strengthening of the oceanic sub tropical anticyclones and the existence of western continental deserts and mediterranean type climate regions

a tectonic model for the metamorphic evolution of the basal gneiss complex western south norway a review of currently available information relevant to the basal gneiss complex bgc of western south norway combined with the authors own observations leads to the following conclusions 1 most of the bgc consists of proterozoic crystalline rocks and probably subordinate lower palaeozoic cover 2 the last major deformation of these rocks was during the caledonian orogeny and involved large scale thrusting recumbent folding and doming the structural development of the bgc is closely tied in with that of the caledonian allochthon 3 the whole eclogite bearing part of the bgc has suffered a high pressure metamorphism with conditions of between 550 c 12 5 kbar sunnfjord and about 750 c 20 kbar more og romsdal at the metamorphic climax 4 this metamorphism was of caledonian age probably rather early in the caledonian tectonic history of the bgc and is considered to have been a rather transient event by setting these conclusions in a framework provided by geophysical evidence for the deep structure of the crust in southern norway we have constructed a geotectonic model to explain the recorded metamorphic history of the bgc it is suggested that considerable crustal thickening was caused by imbrication of the baltic plate margin during continental collision with the greenland plate this resulted in high pressure metamorphism in the resulting nappe stack progradation of the suture caused underthrusting of the baltic foreland below the eclogite bearing terrain causing it to emerge at the earth s surface aided by tectonic stripping and erosion application of isostacy equations to the model shows that eclogites can be formed by in situ metamorphism in crustal rocks and reappear at the land surface above a normal thickness of crust in a single orogenic episode of approximately 65 70 ma duration

active tectonism in the central alps contrasting stress regimes north and south of the rhone valley an integrated interpretation of seismicity fault plane solutions and deep seismic reflection data suggests that the ne sw to nw se trending rhone simplon fault zone and the gently s dipping basal penninic thrust separate fundamentally different stress regimes in the western swiss alps north of the rhone simplon fault zone strike slip earthquakes on steep dipping faults within the helvetic nappes are a consequence of regional nw se compression and ne sw extension to the south vertical maximum stress and n s extension are responsible for normal mechanism earthquakes that occur entirely within the penninic nappes above the basal penninic thrust such normal faulting likely results from extension associated with southward movements collapse of the penninic nappes and or continued uplift and relative northward displacements of the underlying alpine massifs geological mapping and fission track dating suggest that the two distinct stress regimes have controlled tectonism in the western swiss alps since at least the neogene

tectonics of the scandian orogeny and the western gneiss region in southern norway two crust forming events dominate the precambrian history of the western gneiss region wgr at about 1800 1600 ma and 1550 1400 ma the influence of the sveconorwegian orogeny 1200 900 ma is restricted to the region south of moldefjord romsdalen a series of anorthosites and related intrusives are present possibly derived from the now lost western margin of the baltic craton that may have been emplaced in the wgr as an allochthonous unit before the ordovician

structure and dynamics of the summertime pacific japan teleconnection pattern convective activity over the tropical western pacific is known to influence the extratropical circulation over east asia in the boreal summer in the form of teleconnection called the pacific japan pj pattern but its structure and dynamics have not yet been studied in depth in this study a composite analysis is performed for 32 monthly events of enhanced convection observed to the east of the philippines the composited monthly mean vorticity anomalies associated with the pj pattern are elongated zonally with a distinct poleward tilt with height this structure differs fundamentally from a combination of the first baroclinic mode in the tropics and the barotropic structure in midlatitudes as has widely been accepted as a conceptual model of the pj pattern a wave activity flux points polewards only in the lower troposphere indicating that rossby wave teleconnection occurs primarily through a low level south westerly jet those tilted anomalies over the western pacific can effectively gain kinetic energy in the exits of the mean jet streams in the upper and lower troposphere and available potential energy ape in the presence of the vertically sheared jets the enhanced convection can generate ape effectively and the associated low level anomalous circulation acts to increase moisture supply into the convective region while enhancing evaporation from the pre warmed ocean surface it is thus hypothesized that the pj pattern may be regarded as a dynamical mode that can be effectively excited in the zonally asymmetric baroclinic mean flow associated with the asian summer monsoon with an efficient self sustaining mechanism through moist processes copyright 2006 royal meteorological society

origin of calcite in syntectonic veins as determined from carbon isotope ratios a particular feature of many alpine tectonic thrust sheets composed of carbonates is the development of distinct generations of calcite filled veins in the doldenhorn nappe one of the helvetic nappes of switzerland we were able to distinguish five different generations of calcite filled veins determination of carbon isotope ratios in these calcite veins and their adjacent limestone matrix indicates that the earlier vein systems contain carbonate material not in isotopic equilibrium with the adjacent matrix in the case of the later vein systems the carbon 13 content approaches that of the nearby matrix the isotope data indicate a transition from a chemically open system to a closed system this trend is related to an overall modification of the deformation mechanism of the nappe resulting in the increasing importance of pressure solution with time

the structure of the helvetic nappes and its relation to the mechanical stratigraphy abstract this paper discusses structure and variations in structural style due to changes in mechanical stratigraphy of the helvetic nappes based on five cross sections the ratio n of the thickness of mechanically weak to the thickness of adjacent mechanically strong layers is of particular importance a low value of n favours imbricate thrusting and harmonic folding a high value favours detachment and disharmonic folding the transition at around n 0 5 is characterized by polyharmonic folding stratigraphic thickness variations due to local basin subsidence resulted in arcuate fold hinges and important plunges upon basin inversion lateral variations in the overall structure of the helvetic nappes is largely controlled by the initial irregular arrangements of the various small basins one more or less coherent thrust sheet the cretaceous stockwerk of the wildhorn drusberg santis nappe can be traced along the entire fold and thrust belt

the nonlinear transient atmospheric response to tropical forcing abstract ensemble integrations using a primitive equation dry atmospheric model were performed to investigate the atmospheric transient response to tropical thermal forcings that resemble el nino and la nina the response develops in the north pacific within 1 week after the integration the signal in the north atlantic and europe is established by the end of the second week significant asymmetry was found between the responses in el nino and la nina that is similar to the observations that is one feature is that the 550 hpa positive height response in the north pacific of the la nina run is located about 30 west of the negative response of the el nino run another feature is that the responses in the north atlantic and europe for the la nina and el nino cases have similar patterns with the same polarity the first feature is established within 2 weeks of the integration while the second feature develops starting from the end of the second week several factors contribute to this nonlinearity of the

global teleconnections in the 250 mb streamfunction field during the northern hemisphere winter abstract teleconnections of the streamfunction in the global domain based on ecmwf 250 mb winds for the 11 northern winters from 1978 79 through 1988 89 are documented in this study a zonal structure with a node near the equator indicating an out of phase relationship between the streamfunctions in the northern and southern hemisphere appears to mask the fluctuations of the asymmetric components of streamfunction after removing zonal means a global pattern emerges as the dominant structure in the low frequency band this pattern consists of several dipoles straddling either the exit region of midlatitude jets or the equator indicating the existence of teleconnections not only between the midlatitudes and the tropics but also between the northern and southern hemispheres teleconnection patterns in the intermediate frequency band are predominantly wavelike seven waveguides are identified based on the one point lag correlation maps for base points near the maximum teleconnectivity among them are thr

upper tropospheric equatorial waves in ecmwf analyses tropical wind fields from the european centre for medium range weather forecasts operational analyses are analysed to search for equatorially trapped waves in the upper troposphere data are studied for 1980 87 zonal wind spectra show a predominance of power at low zonal wave numbers and low frequencies these data do not show distinct spectral peaks corresponding to eastward propagating kelvin waves or westward propagating equatorially trapped rossby waves the zonal wind spectra do show episodic evidence for westward propagating 5 day zonal wave 1 features with maxima over the equator these are likely related to rossby normal mode oscillations previously reported meridional wind spectra show a predominance of westward propagating power in the 6 to 10 day period range primarily concentrated in zonal waves 4 7 enhanced meridional wind activity at the equator occurs episodically in time with events persisting for one to several months duration wave packets are longitudinally localized with preferred occurrence over the eastern pacific ocean most cases show evidence of meridional wind maxima in the tropics suggesting a degree of equatorial trapping the horizontal structure of these oscillations is that of mixed rossby gravity waves although they are not necessarily centred directly over the equator these waves have largest amplitudes in the upper troposphere showing weak coherence with the surface they appear to be fundamentally distinct from fast 4 to 5 day rossby gravity waves observed in the western pacific a detailed study of a group of intense rossby gravity waves observed over the eastern pacific during august september 1985 is presented the reality of these features is confirmed in direct rawinsonde observations correlations are found between bursts of equatorial wave activity and enhanced meridional momentum fluxes from the subtropics suggesting extratropical forcing as at least one mechanism for their generation the waves are also strongly coupled to the upper tropospheric zonal wind field which likely accounts for their longitudinal and temporal confinement

holocene itcz and indian monsoon dynamics recorded in stalagmites from oman and yemen socotra abstract high resolution oxygen isotope 18o profiles of holocene stalagmites from four caves in northern and southern oman and yemen socotra provide detailed information on fluctuations in precipitation along a latitudinal transect from 12 n to 23 n 18o values reflect the amount of precipitation which is primarily controlled by the mean latitudinal position of the itcz and dynamics of the indian summer monsoon ism during the early holocene rapidly decreasing 18o values indicate a rapid northward displacement in the mean latitudinal position of the summer itcz and the associated ism rainfall belt with decadal to centennial scale changes in monsoon precipitation correlating well with high latitude temperature variations recorded in greenland ice cores during the middle to late holocene the summer itcz continuously migrated southward and monsoon precipitation decreased gradually in response to decreasing solar insolation a trend which is also recorded in other monsoon records from the indian and east asian monsoon domains importantly there is no evidence for an abrupt middle holocene weakening in monsoon precipitation although abrupt monsoon events are apparent in all monsoon records they are short lived and clearly superimposed on the long term trend of decreasing monsoon precipitation for the late holocene there is an anti correlation between ism precipitation in oman and inter monsoon spring autumn precipitation on socotra revealing a possible long term change in the duration of the summer monsoon season since at least 4 5 ka bp together with the progressive shortening of the ism season gradual southward retreat of the mean summer itcz and weakening of the ism the total amount of precipitation decreased in those areas located at the northern fringe of the indian and asian monsoon domains but increased in areas closer to the equator

global extratropical response to diabatic heating variability of the asian summer monsoon abstract global teleconnections associated with the asian summer monsoon convective activities are investigated based on monthly data of 29 northern hemisphere summers defined as june september jjas two distinct teleconnection patterns are identified that are associated respectively with variabilities of the indian summer monsoon and the western north pacific summer monsoon the indian summer monsoon convective activity is associated with a global pattern that has a far reaching connection in both hemispheres whereas the western north pacific summer monsoon convective activity is connected to a southern hemisphere wave train that influences the high latitude south pacific and south america a global primitive equation model is utilized to assess the cause of the global circulation anomalies the model responses to anomalous heatings of both monsoon systems match the general features of the observed circulation anomalies well and they are mainly controlled by linear processes the response patterns ar

relation between rock uplift and denudation from cosmogenic nuclides in river sediment in the central alps of switzerland 1 a north south traverse through the swiss central alps reveals that denudation rates correlate with recent rock uplift rates in both magnitude and spatial distribution this result emerges from a study of in situ produced cosmogenic 10be in riverborne quartz in central alpine catchments as a prerequisite we took care to investigate the potential influence of shielding from cosmic rays due to snow glaciers and topographic obstructions to calculate a possible memory from last glacial maximum lgm glaciation and to identify a watershed size that is appropriate for systematic sampling mean denudation rates are 0 27 0 14 mm a for the alpine foreland and 0 9 0 3 mm a for the crystalline central alps the measured cosmogenic nuclide derived denudation rates are in good agreement with post lgm lake infill rates and are about twice as high as denudation rates from apatite fission track ages that record denudation from 9 to 5 ma in general denudation rates are high in areas of high topography and high crustal thickness the similarity in the spatial distribution and magnitude of denudation rates and those of rock uplift rates can be interpreted in several ways 1 postglacial rebound or climate change has introduced a transient change in which both uplift and denudation follow each other with a short lag time 2 the amplitude of glacial to interglacial changes in both is small and is contained in the scatter of the data 3 both are driven by ongoing convergence where their similarity might hint at some form of long term quasi steady state or 4 enhanced continuous quaternary erosion and isostatic compensation of the mass removed accounts for the distribution of present day rock uplift

microearthquake cluster detection based on waveform similarities with an application to the western swiss alps summary highly similar waveforms of different earthquakes are due to similar focal mechanisms and common propagation paths the relative hypocentral locations of events in clusters of similar earthquakes can provide useful insights into geometry and style of faulting at depth within the crust the detection of such earthquake clusters within large data sets can only be accomplished efficiently by means of an automatic procedure therefore we developed an algorithm based on correlation analysis that detects and associates events with similar waveforms the algorithm has been applied to a data set recorded in the western swiss alps 619 out of a total of 1497 events exhibit similarities with other events based on a more detailed investigation of two selected clusters with known focal mechanisms it could be shown that the active fault planes correspond to neotectonic structures mapped in the study area due to their oblique orientation relative to the larger scale epicentral alignment these faults have been interpreted as riedel shears

metastability of granulites and processes of eclogitisation in the uhp region of western norway the flatraket complex a granulite facies low strain enclave within the western gneiss region provides an excellent example of metastability of plagioclase bearing assemblages under eclogite facies conditions coesite eclogites are found 28 kbar unprecedented metastability of plagioclase and quartz is implied alternatively a tectonic break exists between the flatraket complex and uhp eclogites supporting the concept of a tectonic boundary to the uhp zone of the western gneiss region the distribution of eclogite and amphibolite facies metamorphic overprints demonstrates that the reactivity of the crust during deep burial and exhumation is strongly controlled by fluid availability and is a function of the protolith

40ar 39ar mineral dates related to devonian extension in the southwestern scandinavian caledonides abstract middle devonian sedimentary basins exposed in west central norway formed during post caledonian extension they developed along west dipping low angle normal faults which effected ductile shearing of pre caledonian basement units of the western gneiss region wgr kinematic indicators suggest that the west vergent ductile deformation overprinted older east vergent caledonian fabric elements ductile extensional deformation led to development of a 2 km thick shear zone beneath the devonian basins five amphibole and nine muscovite concentrates from rocks within the shear zone and from unaffected gneisses of the western gneiss region have been analyzed with 40ar 39ar incremental release dating techniques in an attempt to calibrate the timing of extensional events well defined plateau ages are recorded by muscovite concentrates within the shear zone amphiboles display disturbed plateau ages clearly related to extraneous argon outside the shear zone muscovite records caledonian ages results suggest that a late tectonometamorphic event affected the rocks within the shear zone this event which not exceed ca 500 c completely rejuvenated muscovite argon systems and perturbed argon distribution within amphiboles this metamorphism is correlated with the extensional deformation which effected exhumation of the caledonian high pressure rocks and controlled formation of devonian basins

discrimination of annealed and dynamic fabrics consequences for strain localization and deformation episodes of large scale shear zones abstract large scale shear zones are often characterized by long lasting deformation with complex strain localization behavior based on a drill core across polymineralic carbonate mylonites of the doldenhorn nappe helvetic alps switzerland the present study uses spatially resolved microstructural variations to discriminate unambiguously deformation microstructures from annealed ones to infer the deformation mechanisms and to reconstruct the strain localization history these goals require quantitative microstructural and textural analyses of sample suites in sections across the shear zone particularly the occurrence of two distinct zener trends i e the relationship between grain size and volume fraction of matrix and second phase grains allows for the identification of annealed from dynamic microstructures the data presented here indicate that continued shearing after peak metamorphic conditions and during exhumation induced cooling resulted in progressive strain localization at the base of the shear zone while the inactive parts of the formerly high temperature shear zone were progressively overprinted by annealing

active deformation in the eastern swiss alps post glacial faults seismicity and surface uplift abstract post glacial tectonic faults in the eastern swiss alps occur as single lineaments clusters of faults or extensive fault zones consisting of several individual faults aligned along the same trend the orientation of the faults reflects the underlying lithology and the pre existing structures joints pervasive foliations within these lithologies most post glacially formed faults in the area around chur which undergoes active surface uplift of 1 6 mm year trend e w and cut across alpine and glacial features such as active screes and moraines additionally there are nnw and ene striking faults reactivating pervasive alpine foliations and shear zones based on a comparison with the nodal planes of recent earthquakes e w striking faults are interpreted as active faults because of very short rupture lengths and mismatches of fault location with earthquake distribution magnitude and abundance the faults are considered to be secondary faults due to earthquake shaking cumulative deformation in post or interseismic periods or creep and not primary earthquake related faults the maximum of recent surface uplift rates coincides with the youngest cooling of the rocks according to apatite fission track data and is therefore a long lived feature that extends well into pre glacial times isostatic rebound owing to overthickened crust or to melting of glacial overburden cannot explain the observed surface uplift pattern rather the faults earthquakes and surface uplift patterns suggest that the alps are deforming under active compression and that the aar massif basement uplift is still active in response to ongoing collision

laterally forced equatorial perturbations in a linear model part ii mobile forcing abstract impacts of atmospheric mean zonal flows on equatorial perturbations laterally forced by extratropical mobile sources in a linear model are examined an analytical solution of the model with a constant mean zonal flow reveals that amplitudes of forced waves can be significantly modulated by the mean zonal flow through its doppler shift effect on the forcing frequency in general amplitudes of westward propagating waves such as the rossby and mixed rossby gravity waves tend to be larger in mean westerlies than in mean easterlies for low frequency forcing but smaller in mean westerlies for high frequency forcing the opposite dependence on the mean zonal flow applies to eastward propagating waves such as the kelvin wave the model numerical solutions show that the spatial structure of the laterally forced equatorial perturbation as a whole is sensitive to the mean zonal flow particularly a substantial zonal variation in the equatorial perturbation occurs when the mean zonal flow varies in long

extratropical forcing of convectively coupled kelvin waves during austral winter abstract observations are presented that link extratropical rossby wave disturbances excited in the southern hemisphere subtropical jet to the initiation of convectively coupled kelvin waves in the pacific intertropical convergence zone itcz during austral winter a baroclinic zonal wavenumber 6 eastward propagating rossby wave train in the subtropical jet turns northeastward in the vicinity of australia inducing upper tropospheric divergence and vertical motion fields that spread equatorward and induce cloudiness anomalies in the tropics lower tropospheric pressure surges excited from the extratropics also induce kelvin wave like geopotential height and temperature anomalies at the surface providing additional lower tropospheric convergence and vertical motion forcing the tropical outgoing longwave radiation olr and circulation fields propagate eastward in tandem with the extratropical rossby wave train at approximately 17 m s 1 kelvin wave activity in the central pacific itcz thus appears to

luminescence dating applications in geomorphological research abstract chronological control remains critical to the interpretation of environmental change and to establishing long term rates of geomorphological processes radiocarbon dating will continue to be the central technique for age assessment of carbon bearing sediments deposited in the last ca 40 ka but alternative absolute dating strategies are required for older or non carbon bearing sediments they include uranium series dating of precipitated sediments k ar and ar ar dating of primary volcanic materials and cosmogenic isotopic dating of surface exposure ages an additional family of methods collectively termed luminescence techniques is increasingly providing a basis for the age assessment of detrital sedimentary deposits these methods directly date the deposition of detrital mineral grains typically quartz and feldspar and have been demonstrated to provide accurate deposition chronologies for up to 800 ka although 150 ka is more typical in the past decade a subset of luminescence techniques which employ optical sample stimulation methods called optical dating has made it possible to date samples from a much wider range of depositional systems given that the methods directly date sedimentation they allow direct assessment of depositional dynamism in numerous terrestrial and subaqueous including marine sedimentary systems and have demonstrated particular potential in the elucidation of chronologies from aeolian dune and loess fluvial colluvial coastal and volcaniclastic environments this paper provides a summary of the principles of the luminescence especially optical dating methods and shows how recent developments specifically single aliquot dating procedures have dramatically enhanced the scope and potential of the method the luminescence techniques are increasingly being incorporated into a wide range of geomorphological studies which seek to establish the nature of landscape changes over the past interglacial glacial cycle and beyond

a thermal tectonic model for high pressure rocks in the basal gneiss complex of western norway abstract the basal gneiss complex bgc of western norway is a segment of continental crust that was subjected to eclogite facies metamorphism during the caledonian orogeny and then was overprinted by amphibolite facies conditions numerical methods have been used to construct a model for thermal evolution of the bgc the calculated temperature depth time tzt paths for the bgc are in good agreement with the sequence of mineral assemblages that occur in metamorphosed mafic and ultramafic rocks however the thermal model indicates that retrograde zoning of minerals in the garnet bearing assemblages of eclogite and ultramafite may have developed metastably at pressures below 10 kbar numerical modeling of iron diffusion in garnet grains adjacent to olivine inclusions was used to calculate zoning profiles based upon the thermal model the calculated zoning profiles have shorter decay distances than the observed zoning profiles which may be due to uncertainties in the diffusion coefficients also discrepancies occur between the tzt paths and specific pt values calculated for eclogite and garnet ultramafite due either to the preservation of pre caledonian mineral assemblages or to utilization of geobarometers and thermometers which are based on different elements in different phases such as a1 in orthopyroxene and fe mg in olivine and garnet

stress field variations in the swiss alps and the northern alpine foreland derived from inversion of fault plane solutions 1 this study is devoted to a systematic analysis of the state of stress of the central european alps and northern alpine foreland in switzerland based on focal mechanisms of 138 earthquakes with magnitudes between 1 and 5 the most robust feature of the results is that the azimuth of the minimum compressive stress s3 is generally well constrained for all data subsets and always lies in the ne quadrant however within this quadrant the orientation of s3 changes systematically both along the structural strike of the alpine chain and across it the variation in stress along the mountain belt from ne to sw involves a progressive counterclockwise rotation of s3 and is most clear in the foreland where it amounts to 45 50 this pattern of rotation is compatible with the disturbance to the stress field expected from the indentation of the adriatic block into the central european plate possibly together with buoyancy forces arising from the strongly arcuate structure of the moho to the immediate west of our study area across the alps the variation in azimuth of s3 is defined by a progressive counterclockwise rotation of about 45 from the foreland in the north across the helvetic domain to the penninic nappes in the south and is accompanied by a change from a slight predominance of strike slip mechanisms in the foreland to a strong predominance of normal faulting in the high parts of the alps the observed rotation can be explained by the perturbation of the large scale regional stress by a local uniaxial deviatoric tension with a magnitude similar to that of the regional differential stress and with an orientation perpendicular to the strike of the alpine belt the tensile nature and orientation of this stress is consistent with the spreading stress expected from lateral density changes due to a crustal root beneath the alps

surface uplift uplift of rocks and exhumation of rocks uplift of the surface of mountain belts requires forces that are comparable in magnitude to those associated with plate motion and therefore determination of rates of surface uplift could provide important information on the dynamics of mountain ranges rates of uplift of the surfaces of mountain ranges have not however been quantified sufficiently well that they provide useful constraints on those processes many reports off surface uplift in mountain ranges are based on mistaking exhumation of rocks or uplift of rocks for surface uplift and provide no information whatsoever on the rates of surface uplift

current strain regime in the western alps from continuous global positioning system measurements 1996 2001 four to six years of continuous measurements at 10 permanent global positioning system sites in the western alps show horizontal residual velocities of 2 mm yr with respect to stable europe uncertainties range from 0 3 to 1 4 mm yr these velocities and the associated strain rate field indicate that the central part of the range is currently dominated by east west extension whereas the southern part shows north south to northwest southeast compression the geodetic and seismotectonic data are consistent with a model where strain is essentially controlled by the counterclockwise rotation of the adriatic microplate with respect to eurasia this rotation together with the arcuate shape of the contact between the adriatic microplate and the alps induces dextral shear kinematic boundary conditions across the western alps with an additional divergence component in their central part and in switzerland and a convergence component in their southern part

cosmogenic nuclide based investigation of spatial erosion and hillslope channel coupling in the transient foreland of the swiss alps abstract transient landscape disequilibrium is a common response to climatic fluctuations between glacial and interglacial conditions such landscapes are best suited to the investigation of catchment wide response to changes in incision the geomorphology of the trub and grosse fontanne adjacent stream systems in the napf region of the swiss molasse was analyzed using a 2 m lidar dem the two catchments were impacted by the last glacial maximum lgm even though the glaciers never overrode this region they did however cause base levels to drop by as much as 80 m despite their similar tectonic lithologic and climatic settings these two basins show very different responses to the changing boundary conditions stream profiles in the trub tend to be smooth while in the fontanne numerous knickzones are visible similarly cut and fill terraces are abundant in the trub watershed but absent in the fontanne where deep valleys have been incised the trub appears to be a coupled hillslope channel system because the morphometrics throughout the basin are uniform the morphology of hillslopes upstream of the knickzones in the fontanne is identical to that of the trub basin but different downstream of the knickzones suggesting that the lower reaches of the fontanne have been decoupled from the hillslopes however the rapid incision of the fontanne is having little effect on the adjacent upper hillslopes we tested this interpretation using cosmogenic 10 be derived basin averaged denudation rates and terrace dating the coupled nature of the trub basin is supported by the similarity of denudation rates 350 50 mm ky 1 at a variety of spatial scales upstream of the knickzones rates in the fontanne 380 50 mm ky 1 match those of the trub downstream of the knickzones denudation rates increase to 540 100 mm ky 1 the elevated rates in the downstream areas of the fontanne are due to rapid incision causing a decoupling of the hillslope from the channel basin response time and the magnitude of base level drop exert the principal control over the difference in geomorphic response between the two basins the timing of the filling of the trub valley 17 2 ka and the initial incision of the fontanne 16 3 ka were calculated verifying that these are responses to late glacial perturbations unique lithologic controls allow for one of the fastest regolith production rates yet to be reported 380 mm ky 1

topographic migration of georadar data implications for acquisition and processing application of conventional elevation static corrections and migration to wavefield data recorded on irregular surfaces may result in poor reconstructions of complex subsurface features particulary poor images may be obtained at locations where the depths to target structures are comparable to undulations in the surface topography for example topographic relief of only 1 2 m may be important for the processing of georadar data we describe an algorithm that allows georadar data to be migrated directly from gently to highly irregular acquisition surfaces when applied to a variety of complicated synthetic data sets topographically migrated images are observed to be markedly superior to those produced by two standard processing schemes extensive tests demonstrate that topographic migration should be considered in regions characterized by surface gradients 10 i e dips 6 for effective topographic migration lateral and vertical coordinates of the georadar antennas should be determined to better

the generation of global rotational flow by steady idealized tropical divergence abstract tropical convective heating is balanced on the large scale by the adiabatic cooling of ascent the horizontal divergence of the wind above this heating may be viewed as driving the upper tropospheric rotational wind field a vorticity equation model is used to diagnose this relationship it is shown that because of the advection of vorticity by the divergent component of the flow the rossby wave source can be very different from the simple fd source often used in particular an equatorial region of divergence situated in easterly winds can lead to a rossby wave source in the subtropical westerlies where it is extremely effective this part of the source can be relatively insensitive to the longitudinal position of the equatorial divergence a divergence field which is asymmetric about the equator can lead to a quite symmetric rossby wave source for a steady frictionless flow the rossby wave source averaged over regions within closed streamfunction or absolute vorticity contours is under cert

influence of the basic state zonal flow on convectively coupled equatorial waves observational data are used to test the hypothesis that the basic state modulates the dispersion properties of convectively coupled equatorial waves ccews this hypothesis is based on shallow water theory which predicts that the zonal speed of propagation of such tropospheric equatorial modes is altered by the equivalent depth and the basic zonal flow localized space time spectra are calculated to investigate how ccew spectral peaks vary across the tropics and how they are affected by the variations in zonal wind observed geographically and by season doppler shifting by the basic state barotropic zonal flow is readily identified once this doppler shifting is taken into account the equivalent depths of ccews inferred from global power spectra are surprisingly uniform both geographically and temporally however there are also detectable modulations that appear consistent with changes in vertical shear of the zonal flow along with other shifts that are not as easily explained

unravelling the evolution of an alpine to post glacially active fault in the swiss alps abstract the gemmi fault is a prominent nw se striking lineament that crosses the gemmi pass in the central swiss alps a multidisciplinary investigation of this structure that included geological mapping joint profiling cathodoluminescence and scanning electron microscopy stable isotope measurements luminescence and u th dating 3d ground penetrating radar gpr surveying and trenching reveals a history of fault movements from the miocene to the holocene the main fault zone comprises a 0 5 3 m thick calcite cataclasite formed during several cycles of veining and brittle deformation displaced cretaceous rock layers show an apparent dextral slip of 10 m along the fault a detailed study of a small sediment filled depression that crosses the fault provides evidence for a post glacial reactivation of the fault a trench excavated across the fault exposed a late glacial age loess layer and late holocene colluvial like slope wash deposits that showed evidence for fault displacement of a few centimeters indicating a recent strike slip reactivation of the fault focal mechanisms of recent instrumentally recorded earthquakes are consistent with our findings that show that the fault at the gemmi pass together with other parallel faults in this area may be reactivated in today s stress field taking together all the observations of its ancient and recent activity the gemmi fault can be viewed as a window through geological space and time

enso related variation of equatorial mrg and rossby waves and forcing from higher latitudes the contrasting behaviour of westward moving mixed rossby gravity wmrg and the first rossby r1 waves in el nino en and la nina ln seasons is documented with a focus on the northern hemisphere winter the eastward moving variance in the upper troposphere is dominated by wmrg and r1 structures that appear to be doppler shifted by the flow and are referred to as wmrg e and r1 e in the east pacific and atlantic the years with stronger equatorial westerly winds have the stronger wmrg and wmrg e in the east pacific r1 is also a maximum in ln however r1 e exhibits an eastward shift between ln and en the changes with enso phase provide a test bed for the understanding of these waves in the east pacific and atlantic the stronger wmrg e and wmrg with stronger westerlies are in accord with the dispersion relation with simple doppler shifting by the zonal flow the possible existence of free waves can also explain stronger r1 in en in the eastern hemisphere 1 d free wave propagation theory based on wave activity conservation is also important for r1 however this theory is unable to explain the amplitude maxima for other waves observed in the strong equatorial westerly regions in the western hemisphere and certainly not their enso related variation the forcing of equatorial waves by higher latitude wave activity and its variation with enso phase is therefore examined propagation of extratropical eastward moving rossby wave activity through the westerly ducts into the equatorial region where it triggers wmrg e is favoured in the stronger westerlies in ln in the east pacific and en in the atlantic it is also found that wmrg is forced by southern hemisphere westward moving wavetrains arching into the equatorial region where they are reflected the most significant mechanism for both r1 and r1 e appear to be lateral forcing by subtropical wavetrains

petrology of a margarite bearing meta anorthosite from seljeneset nordfjord western norway implications for the p t history of the western gneiss region during caledonian uplift abstract the western gneiss region of norway contains relics of eclogite and high pressure granulite that have been extensively overprinted by amphibolite facies assemblages a meta anorthosite from seljeneset nordfjord contains fine grained margarite quartz plagioclase muscovite clots set in a zoisite quartz plagioclase clinozoisite matrix in some clots relict kyanite is preserved equilibria modeled in the cash system indicate a retrograde p t path that begins in the kyanite zoisite field p 8 2 kbar passes through reaction 1 kyanite zoisite quartz anorthite h2o between 610 c and about 800 c and finally through reaction 2 kyanite anorthite h2o margarite quartz the sodic composition of plagioclase in reaction 1 suggests that pressures in excess of 15 17 kbar at 750 800 c may have been experienced during silurian eclogite facies metamorphism the simplified cash reaction 2 occurs between invariant points at 4 3 kbar 520 c and 8 2 kbar 610 c but polyvariance due to variable na solid solution broadens the reaction into a band about 150 c wide cooling through 500 c occurred about 410 ma ago this study provides the first well defined p t path for caledonian retrograde metamorphism at amphibolite facies conditions

intraseasonal variability in a dry atmospheric model abstract a long integration of a primitive equation dry atmospheric model with time independent forcing under boreal winter conditions is analyzed a variety of techniques such as time filtering space time spectral analysis and lag regressions are used to identify tropical waves it is evident that oscillations with intraseasonal time scales and a kelvin wave structure exist in the model tropical atmosphere coherent eastward propagations in the 250 hpa velocity potential and zonal wind are found with a speed of about 15 m s 1 the oscillation is stronger in the eastern hemisphere than in the western hemisphere interactions between the tropical and extratropical flows are found to be responsible for the simulated intraseasonal variability wave activity flux analysis reveals that a tropical influence occurs in the north pacific region where a northeastward wave activity flux is found associated with the tropical divergent flow in the western and central pacific in the north atlantic sector on the ot