evolution of el nino precipitation relationships from satellites and gauges 1 this study uses a 23 year 1979 2001 satellite gauge merged community data set to further describe the relationship between el nino southern oscillation enso and precipitation the globally complete precipitation fields reveal coherent bands of anomalies that extend from the tropics to the polar regions el nino precipitation relationships were analyzed during the six strongest events from 1979 to 2001 el ninos were defined based on the zonal contrast in rainfall in the equatorial pacific and seasons of precipitation evolution pre onset onset peak decay and postdecay were identified areas with a consistent el nino precipitation relationship were determined based on this unique definition of el nino and season of year the latter analysis confirms previous studies and suggests other areas of significant signal over the oceans gulf of alaska the former analysis reveals subtle shifts in tropical rainfall from onset to decay namely negative anomalies moving from the maritime continent and south pacific to the north tropical pacific and positive anomalies from the central equatorial pacific southeastward these distributions of tropical convection appear to be connected to extratropical precipitation anomalies through meridional atmospheric circulations concentrated in the eastern indian ocean sector during onset and in the pacific sector during decay the yangtze river basin which is known to flood during el nino is affected during the entire evolution

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

shear zone patterns and strain distribution at the scale of a penninic nappe the suretta nappe eastern swiss alps abstract shear zone patterns within the suretta nappe of the swiss alps are studied in order to understand finite strain and bulk tectonic displacements the suretta nappe is chosen for two main reasons the availability of late variscan granites deformed during alpine tectonics only and because of continuous outcrop from bottom to top of the nappe this alpine nappe recorded two major ductile deformation phases which developed under low grade metamorphic conditions the analysis of shear zone patterns in the roffna granite reveals that the first deformation is well developed in the entire nappe the second deformation however is more localized in the lower and upper parts the bulk asymmetry of the shear zone patterns confirms the kinematics recorded by other penninic nappes in this area first a stacking of the nappe towards the nw followed by the top to the e shearing during post thickening extensional tectonics the shear zone patterns and strain distribution allow us to deduce kinematics at the nappe scale

the relationship of highly reflective clouds to tropical climate anomalies abstract the interannual variability of tropical convection related to the southern oscillation so and regional climate anomalies is studied from satellite derived estimates of highly reflective clouds hrc during 1971 87 the novel hrc data bank provides a particularly useful measure of tropical convection for the purposes of climate diagnostics because of its length and continuity of record for the first time maps are presented of the patterns of correlation between the so as well as regional rainfall anomalies and convection over the global tropics throughout the year the so high so phase defined by anomalously high low pressure at tahiti darwin exhibits a highly significant negative correlation with hrc in the equatorial pacific but a much weaker positive correlation with indonesia the so is correlated positively with hrc in the amazon basin in boreal winter but negatively with hrc over central africa throughout most of the year the three equatorial convection centers tend to vary in uni

calculated temperatures in overthrust terrains and possible combinations of heat sources responsible for the tertiary granites in the greater himalaya there are three obvious sources of heat that affect the temperature in a region of thrust faulting heat supplied from below the lower thrust plate radiogenic heating within the crusts of both the upper and especially the lower plates and frictional heating along the fault we assume that heat is conducted primarily in the vertical direction and that solutions to the one dimensional time dependent heat conduction equation can be used to describe the temperature field in overthrust zones the effects of these three sources of heating can be isolated from one another treated separately and then combined in ratios proportional to various assumed rates of heating provided by each we then use calculations for a range of possible combinations of heat sources that may have caused two media granites of late tertiary age in the greater himalaya because of the uncertainties in the age of the granites in the depth at which they formed in the amounts of heat flux supplied to the base of the lithosphere and of radiogenic heat production in the crust inb the value of the coefficient of thermal conductivity and in other parameters a broad range of possible combinations of parameters is possible temperature can reach themore solidus for granite melts with various plausible combinations of parameters both that include no shear heating and that require frictional stresses of 100 s of mpa on the main central thrust for instance if the initial steady state geotherm in the crust now comprising the himalaya were that of a typical shield then frictional heating with a stress in excess of 100 mpa 1 kbar would be necessary to raise the temperature of material near a thrust fault at 20 or 30 km depth to 650 sup 0 c less

a model for the deep structure of the moine thrust zone seismic refraction and electrical conductivity profiles across northern scotland together with geological and other geophysical data are interpreted in terms of the deep structure of this part of the orthotectonic caledonides our preferred interpretation is that the moine thrust zone extends to the base of the crust and the caledonian front is steep this contrasts with recently proposed ultra thin skinned solutions the results of the recently completed moist deep seismic reflection experiment should inter alia test our hypothesis in order to test the geometrical feasibility of our interpretation balanced sections have been constructed to illustrate the crustal evolution of the region during the caledonian orogeny these sections permit estimates to be made of crustal shortening thickening and erosion our model requires that the n highlands were once overlain by major exotic nappes which by analogy with nw newfoundland may have been ophiolitic the proposed regional structural pattern comprises a duplex of crustal dimensions we suggest that crustal duplex development is an important mechanism in the orogenic deformation of previously thinned and extended passive continental margins

thermal effects of thrust faulting abstract calculations based on simple models of overthrust sheets in crystalline basement rocks show that significant thermal effects may result from their movements if rates are sufficiently high e g plate tectonic rates the thrust sheets sufficiently thick 5 10 and 15 km are modelled here the distances moved sufficiently large and for reasonable values of the coefficient of friction along the thrust plane overthrusting can cause metamorphic mineral zonations and heat flow anomalies observable in the field regions where large scale overthrusting has occurred should be characterized by a decrease with depth of grade of metamorphic mineral assemblages and anomalously low heat flow the theoretical effects are presented as a series of maximum temperature vs depth and heat flow vs time plots

on the relationship between the qbo and tropical deep convection abstract the height and amount of tropical deep convection are examined for a correlation with the stratospheric quasi biennial oscillation qbo a new 23 yr record of outgoing longwave radiation olr and a corrected 17 yr record of the highly reflective cloud hrc index are used as measures of convection when binned by phase of the qbo zonal means and maps of olr and hrc carry a qbo signal the spatial patterns of the maps highlight the qbo signal of olr and hrc in typically convective regions spectral analysis of zonal mean olr and hrc near the equator reveals significant peaks at qbo frequencies rotated empirical orthogonal function reof analysis is used to determine if enso variations of convection are aliased into the observed qbo signals some analyses are repeated using the olr record after enso reof modes have been removed yielding very similar results compared to the original analyses it appears that the qbo signal is distinct from the enso signal although the relative brevity of the

petrologic constraints on imbrication metamorphism and uplift in the sw tauern window eastern alps the pressure temperature time deformation pttd history of two tectonic units in the southwest tauern window austria italy is evaluated from p t paths of metamorphism and uplift geochronologic data and observations on fabric development petrologic data indicate burial of the lower schieferhulle lsh to depths of 35 km and the adjacent upper schieferhulle ush to only 24 28 km the units are now separated by only 2 km of section metamorphism was postkinematic in the lsh and synkinematic in the ush correlation of p t path reversals calculated from zoned garnets in the two units however indicates that juxtaposition of the lsh and ush occurred prior to metamorphism temperature time and depth time diagrams for both units show increasing cooling rates and decreasing uplift rates as the rocks approached the surface both the petrologic data and the depth time profiles for the lsh and ush point to a history of differential uplift in the early stages of decompression textural features indicate that the lsh behaved as an essentially rigid body during uplift whereas the ush experienced extensive ductile shearing the pttd data for the lsh and ush are incorporated into a model for continental collision in the eastern alps initial tectonic uplift of the lsh was accompanied by ductile thinning of the ush and overlying austroalpine units final uplift and erosion affected all of the units en masse

geological interpretation of dekorp 2 s a deep seismic reflection profile across the saxothuringian and possible implications for the late variscan structural evolution of central europe abstract a 250 km long deep seismic section the first of its kind in west germany s dekorp project is interpreted in terms of late variscan collisional tectonics the structural model used is based on the intracontinental thrust tectonics concept of modern collision orogens the crustal profile across the saxothuringian zone seems to indicate north facing ramps antiformal stacks and culminations within the crystalline basement of the internal mid european variscides that have been only partially overprinted by permo mesozoic crustal stretching

structural evolution of an a type subduction zone lofoten rombak area northern scandinavian caledonides the climactic phase of the caledonian orogeny in scandinavia involved collision of the baltic and greenland cratons in late ordovician to silurian time we infer that the collision resulted in large scale subduction of the leading edge of the baltic craton beneath an andean type greenland continental margin deep erosional levels in the lofoten rombak area norway sweden 69 n permit direct examination and evaluation of the structural evolution of a continental or a type subduction zone the early stages of collision involved en bloc underthrusting of the continental margin to depths of at least 30 km during this process deformational effects in the lower plate were restricted to its upper few hundred meters ultimately en bloc a type subduction should be limted by buoyancy effects as convergence continued the lower plate became involved in a series of imbricate thrusts with the same vergence as the intial subduction zone the temporal and spatial relationships between these basement involved thrusts are similar to those observed in foreland fold and thrust terrains field and geophysical data bearing on lower plate behavior elsewhere in the caledonldes and in other collisional orogens suggest that the structural features observed in the lofoten rombak area may be generally characteristic of a type subduction in continent continent collisional settings

the role of extension in the miocene denudation of the nevado filabride complex betic cordillera se spain the internal zone of the betic cordillera se spain consists of a nappe stack of three complexes the deepest of which is the nevado filabride complex the zone is separated from the overlying alpujarride complex by a crustal scale shear zone that has variously been interpreted as a thrust or an extensional detachment a suite of 74 new apatite and zircon fission track results have been obtained from the nevado filabride complex and these have been used to define regional cooling patterns for the complex rapid cooling 105 c 200 c ma 1 is spatially related to the tectonic contact with the overlying alpujarride complex cooling to near surface temperatures occurred first in the east sierra de los filabres during the mid serravallian 12 1 ma and was completed by the early tortonian 9 8 ma in the west sierra nevada there is no correlation between fission track age and sample elevation these results are consistent with tectonic unroofing of this complex a finding that favors extension as the mechanism by which the two complexes were brought into contact extension spans the middle and earliest upper miocene 12 8 ma in the study area and therefore lasted much longer than previously documented a hypothesis is advanced which links oblique convergence between the iberian plate and the betic internal zones resulting in crustal contraction at depth with orogen parallel extension in the middle and upper crust

the lepontine alps as an evolving metamorphic core complex during a type subduction evidence from heat flow mineral cooling ages and tectonic modeling new surface heat flow data are presented for the valle maggia region within the high grade metamorphic core of the lepontine alps the steady state values range from 44 4 to 55 2 mw m2 and are anomalously low compared with those measured around the periphery of the lepontine these differences are considered to reflect the combined effects of differential uplift and erosion superimposed on a transient low heat flow regime which has existed since the miocene the uplift denudation history of the lepontine is modeled by using various mineral geochronometers two major pulses of accelerated uplift are recognized at circa 22 m y b p and circa 10 m y b p respectively these events directly coincide with times of dominant crustal convergence in the helvetic and jura stages of a subduction from known pmax tmax conditions of oligocene metamorphism estimates of low mantle heat flow and experimentally determined values of crustal heat production best fit thermal models are presented to explain surface heat flow and mineral cooling age data for the metamorphic core a two stage underplating model is shown to be consistent with the excavation history of the lepontine and with geological and geophysical data from more external parts of the central alps this information is integrated to explain the establishment of a crustal scale duplex in the metamorphic core complex contemporaneous with thin skinned tectonics in the foreland

the recovery of true particle motion from three component ocean bottom seismometer data the principal motivation for the development of multicomponent ocean bottom seismometers obs s was the hope that measurement of vector particle velocities would permit sharper interpretation of seismic data since wave types p and s could be better indentified with this knowledge the practical results of obs use have not entirely borne out this expectation instead the obs seafloor coupling system characteristically shows strong resonances resulting in a ringy appearance of almost all obs data previous attempts to deal with this problem have used seriously oversimplified one dimensional analyses in the present work we first consider an ideal model of an obs as a hamiltonian system with three spatial degrees of freedom this is generalized to a linear system having n degrees of freedom with three inputs and three outputs and we find that the obs site system is an all pole minimum delay multichannel filter whose properties may be estimated from in situ seismic data we apply the inverse of this filter to noise series obtained with a three component obs used in the rivera ocean seismic experiment resonance peaks in the noise power spectra are almost completely removed but at the cost of the gain obtained through resonant detection the most significant implication of this work is that accurate ground motion can be recovered from almost any three component obs nevertheless poor performance of obs s will lead to degraded recovery of ground motion so that design considerations which reduce the resonances in obs seafloor coupling remain important

global patterns of enso induced precipitation although there have been many analyses of el nino southern oscillation enso induced precipitation anomalies global patterns from these analyses remain incomplete here we combine recent satellite estimates of oceanic precipitation and historical rain gauge records to derive a global climatology of enso induced precipitation anomalies using empirical orthogonal function eof analyses the patterns suggest that the re arrangement of convection centers of the walker circulation during enso events induces large precipitation anomalies in the tropics while associated changes in the monsoon systems through the hadley cell over the pacific indian and atlantic oceans and their interactions with midlatitude westerlies generate coherent anomaly patterns over the extratropics our results can be used to evaluate climate models and forecast enso induced precipitation anomalies

basement cover relationships in the tambo nappe central alps switzerland geometry structure and kinematics in the pennine zone of the central alps the tambo nappe forms a thin crystalline sliver embedded in the mesozoic cover four tertiary alpine deformations are observed the d1 ductile deformation is linked to the progressive eocene stacking of the nappes towards the northwest during d1 basement deformation is governed by imbricate tectonics whereas cover is thin skinned and intensively folded these different structures reflect the original strong rheological contrast between basement and cover during the heterogeneous and ductile d2 deformation the behaviour of the basement and cover became similar the strong vertical d2 shortening associated with a top to the east shear led to the folding of the prior se dipping structures developing se vergent folds with axes close to the e w l2 stretching lineation d2 corresponds to post collisional crustal thinning following d2 crustal thickening the d3 and d4 deformations occurred under retrograde conditions and can be correlated with uplift and late dextral movement on the insubric line respectively

the building of the central swiss alps an experimental approach abstract a kinematic model explaining the building of the central swiss alps is proposed from a review of various kind of data including structural geophysical petrological and geochronological data the eo alpine event is taken into account in order to determine the thermo mechanical evolution from the cretaceous to the late tertiary the stacking process of crustal wedges which took place during cretaceous time has led to the formation of a thickened crust with a very low geothermal gradient high pressure low temperature metamorphism this period was followed by a lull in tectonic activity during which thermal relaxation took place the major tertiary deformation is thought to result from horizontal compression of a thickened crust having a geothermal gradient higher than the average horizontal surface forces are due to the adriatic sub plate acting as a rigid indenter the model explaining the present day structure of the swiss alps emphasizes vertical extrusion and horizontal intrusion of the deepest highly ductile basement units several scale model experiments have been carried out in order to test this basic kinematic idea they display quite similar structures to those identified for the swiss alps striking features of the swiss alps such as their metamorphic and uplift history are discussed and compared with the timing of the tectonic evolution we conclude that the general process of vertical extrusion and horizontal intrusion can possibly explain the overall structure of the central swiss alps external crystalline massifs and the penninic zone

constraints on unroofing rates in the high himalaya eastern nepal thermobarometric data for samples across the main central thrust zone in eastern nepal show an inversion in temperature but not in pressure these data have been interpreted to represent a portion of the paleogeotherm at the time of main central thrust deformation a 40ar 39ar age on hornblende closure temperature tc 500 50 c constrains the timing of this deformation to be 21 0 2 ma the 40ar 39ar ages of other minerals muscovite tc 350 c age t 12 0 0 2 ma k feldspar tc 220 c t 8 0 0 2 ma from the same location further constrain the cooling history of this region together the geochronologic and thermobarometric data yield an average unroofing rate of 1 2 0 6 mm yr for the high himalaya of eastern nepal simple thermal models show that these geochronologic and thermobarometric data are consistent with a wide range of different initial geotherms applied boundary conditions and magnitude of radiogenic heat production the variation through time of the unroofing rates can only be poorly constrained however the unroofing histories were found to be largely insensitive to the details of the assumed initial geotherm fairly sensitive to the magnitude of radiogenic heat production and extremely sensitive to the nature of the boundary conditions applied below the fault zone this study underscores the difficulty in constraining uplift histories on the basis of cooling rates even when thermobarometric data are available to supplement geochronologic constraints on the cooling history of the region

mechanisms for folding of high grade rocks in extensional tectonic settings abstract this review of structures developed in extensional high grade terrains combined with results of centrifuge analogue modelling illustrates the range of fold styles and mechanisms for folding of amphibolite to granulite facies rocks during rifting or the collapse of a thrust thickened orogen several extensional fold mechanisms such as folding within detachment shear zones are similar to those in contractional settings the metamorphic p t t path and not fold style or mode of formation is therefore required to determine the tectonic setting in which some folds developed other mechanisms such as rollover above and folding between listric normal shear zones and folding due to isostatic adjustments during crustal thinning are unique to extensional tectonic settings several mechanisms for folding during crustal extension produce structures that could easily be misinterpreted as implying regional contraction and hence lead to errors in their tectonic interpretation it is shown that isoclinal recumbent folds refolded by open upright folds may develop during regional extension in the deep crust folds with a thrust sense of asymmetry can develop due to high shear strains within an extensional detachment or from enhanced back rotation of layers between normal shear zones during back rotation folding layers rotated into the shortening field undergo further buckle folding and all may rotate towards orthogonality to the maximum shortening direction this mechanism explains the presence of many transposed folds folds with axial planar pegmatites and folds with opposite vergence in extensional terrains examples of folds in high grade rocks interpreted as forming during regional extension included in this paper are from the grenville province of canada norwegian caledonides albany mobile belt and leeuwin complex of western australia ruby mountains in the basin and range province of nevada the at sund area of greenland the napier complex of enderby land in east antarctica and the kigluaik mountains in western alaska

quantifying tectonic versus erosive denudation by the sediment budget the miocene core complexes of the alps abstract the denudation budget of the alps is quantified for the main period of lateral extrusion between 22 and 12 ma the relative importance of tectonic denudation increases from w to e from 70 in the lepontine window in the swiss alps to 80 in the tauern window and to more than 95 in the rechnitz window the driving mechanism of tectonic denudation was eastward extrusion due to an unconstrained orogenic margin in the pannonian basin tectonic denudation in the alps was responsible for about 30 of the total exhumation between 22 and 12 ma

tectonic denudation of a late cretaceous tertiary collisional belt regionally symmetric cooling patterns and their relation to extensional faults in the anatolide belt of western turkey t hermochronological data reveal that the late cretaceous tertiary nappe pile of the anatolide belt of western turkey displays a two stage cooling history three crustal segments differing in structure and cooling history have been identified the central menderes metamorphic core complex represents an inner axial segment of the anatolide belt and exposes the lowest structural levels of the nappe pile whereas the two outer submassifs the g ordes submassif to the north and the ci ne submassif to the south represent higher levels of the nappe pile a regionally significant phase of cooling in the late oligocene and early miocene affected the outer two submassifs and the upper structural levels of the central menderes metamorphic core complex in the northern part of the g ordes submassif cooling was related to top to the nne movement on the simav detachment as the apatite fission track ages show a northward younging trend in the direction of movement on this detachment in the ci ne submassif relatively rapid cooling in late oligocene and early miocene times may have been related to top to the s extensional reactivation of the basal thrust of the overlying lycian nappes the second phase of cooling in the anatolide belt is related to pliocene to recent extension resulting in the formation of the central menderes metamorphic core complex in the inner part of the anatolide belt core complex development caused the formation of supra detachment graben which document the ongoing separation of the central menderes metamorphic core complex from the outer submassifs

el nino and la nina in highly reflective cloud abstract over the last two decades several scientists have used garcia s record of highly reflective cloud hrc to study the el nino southern oscillation enso recently waliser and zhou removed a satellite bias this note describes a test for the presence of the enso signal in the corrected record the test treats anomaly values of corrected hrc in a grid that covers the equatorial western pacific ocean for each box in the grid the hrc anomaly was averaged over el nino events in the record from the averages a map of the el nino hrc anomaly was made similarly a map of the la nina hrc anomaly was made each map shows a strong east southeast west northwest trending dipole the el nino dipole dips toward the west northwest implying excess cloud in the east southeast the la nina dipole dips toward the east southeast implying excess cloud in the west northwest in respect to these dipoles the pair of hrc anomaly maps closely resembles published enso rain anomaly maps the mapping was repeated fo

a geothermic method for the reconstruction of the uplift history of a mountain range applied to the central alps vertical movements of a crustal block in connection with denudation sedimentation or overthrusting respectively lead to a change in the temperature field this process can be used to correlate the uplift and temperature history of a rock sample in a quantitative way the uplift rate may change over a period of time the effect of the radiogenic heat sources has been taken into account in the calculations

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

moist and the continuity of crustal reflector geometry along the caledonian appalachian orogen new aspects of the deep structure of the scottish caledonides are revealed by the moine and outer isles deep seismic reflection traverse moist the caledonian foreland is underlain by an easterly dipping strongly reflecting surface cutting through the moho and traceable to more than 45 km depth thrusts within the foreland basement and caledonian orogen have been reactivated as normal faults bounding half grabens filled with sediments of late palaeozoic to mesozoic age the moine thrust which carries rocks of the orogen over lewisian foreland dips at 20 25 to the e on moist and is either a the westernmost of a series of easterly dipping reflections thrusts which flatten or terminate at 17 20 km depth or b a thrust lying further e which structurally overlies these easterly dipping reflectors by comparison with easterly dipping reflections on cocorp lines in the northern and southern appalachians the latter interpretation is preferred implying that many of the easterly dipping reflections on moist correspond to off shelf metasedimentary rocks with slivers of basement stacked and imbricated against the lewisian basement edge regional seismic refraction and conductivity data from northern scotland suggest that regions of the caledonian orogen have lower mid crustal velocity gradients and higher conductivities than the foreland which might be explained by this interpretation of the easterly dipping reflections despite similarities in crustal reflector geometries there are important differences between the moist and cocorp lines including 1 a remarkably continuous relatively horizontal moho seen on moist data at about 25 km depth and 2 the sedimentary basins offshore from northern scotland which have formed by reactivation under crustal extension of the easterly dipping thrusts furthermore it is probable that the easterly dipping reflectors in these areas of the moist and cocorp lines were formed at different times in the early palaeozoic

three dimensional geometry and tectonostratigraphy of the pennine zone central alps switzerland and northern italy abstract continental collision during alpine orogenesis entailed a polyphase deformation history d1 d5 in the pennine zone of the central alps the regional tectonostratigraphy was basically developed during d1 and d2 characterised by isoclinal typically north closing recumbent anticlines separated by pinched in synclines on the scale of tens of kilometres later deformation phases d3 and d4 warped the stack into wavy to open folds exhumation of this zone resulted locally in later vertical shortening and folding of already steep fabrics d5 three dimensional models of the nappe pile were constructed based on geostatistical assessment of the regional foliation field and considering the abundant structural field data these models indicate the existence of five principal tectonostratigraphic levels developed during d1 and thus equivalent to nappe units s str the gotthard the leventina antigorio the maggia simano and probably the monte leone as well as the composite lepontine series lebendun soja and adula cima lunga levels all these tectonic units formed part of the passive continental margin of europe prior to the onset of the alpine orogenesis individual isoclinal post nappe folds reflect relative displacements on the order of 40 km or more the most prominent d2 post nappe structure is the wandfluhhorn fold structurally equivalent to the northern closure of the leventina lucomagno antiform the lebendun and monte leone folds are of similar magnitudes and also affect the whole nappe pile whereas the smaller mogno and molare synforms only refold the maggia simano nappe internally principal d3 and d4 structures are the tight mergoscia synform directly north of the insubric fault between bellinzona and locarno southern steep belt the maggia steep zone forming the steep western limb of the campo tencia synform and subdividing the lepontine dome into the simplon and ticino subdomes the chiera synform steepening the dominant foliation in the north northern steep belt and the vanzone and claro antiforms steepening the dominant foliation in the south southern steep belt the current geometry of the northern and southern steep belts reflects an interplay between d4 and d3 involving both fold interference and reactivation tightening

paleoatmospheric consequences of co2 released during early cenozoic regional metamorphism in the tethyan orogen the eocene was the warmest epoch of the cenozoic with published estimates of eocene atmospheric co2 content ranging from two to six times the current value calculations of co2 consumption by silicate weathering show that co2 fluxes to the atmosphere of ca 1018 myr could account for inferred paleocene eocene atmospheric co2 contents and the resulting greenhouse effect would have contributed to eocene warmth extensive portions of the tethyan orogen underwent regional metamorphism culminating in the eocene prograde metamorphism may have been contemporaneous with the late paleocene global warming we calculated the amount of metamorphic co2 produced at depth in the himalayan orogen with data on the timing of the india asia collison duration of prograde regional metamorphism and proportions and bulk compositions of metamorphic co2 source rocks if co2 was generated at a constant rate over a 10 myr period of prograde metamorphism in the himalayan orogen we estimate that ca 1018 1019 moles myr of metamorphic co2 were produced at depth significant expulsion of metamorphic co2 to the atmosphere may have occurred by focused fluid flow along shear zones such as the extensive main central thrust in the himalayan orogen an additional ca 1018 myr could have been contributed by eocene regional metamorphism in the mediterranean tethys i e from the alps to turkey the extensive metamorphism associated with the india asia collision and the closing of tethys may have contributed to co2 greenhouse warming in the early to mid cenozoic

metamorphic pressure estimates and sediment volumes for the alpine orogeny an independent control on geobarometers theories which regard the deep erosion 20 30 km of orogenic belts as an important factor in the thermal development of the continents rely on pressure estimates from metamorphic geobarometers to give an estimate of the depth scale for this process the imprecision of geobarometers and the apparent lack of sediments that would result from this amount of erosion are frequently made arguments for much smaller erosion depths the alps are a well studied young mountain belt and afford the opportunity to compare overburden masses inferred from geobarometry with sediment masses in the surrounding sedimentary basins this comparison suggests that metamorphic geobarometry has not significantly overestimated burial depths and that the average erosion to date has been over 15 km with a maximum of 25 km or more it is probable that the total erosion in the belt will eventually average 20 25 km with a maximum of around 40 km a significant feature of the sediment distribution is that over 50 of the volume is outside the neighbouring along strike sedimentary basins this fact which accounts for previous low estimates of alpine sediment volumes follows from the response of the lithosphere to loading by continental thickening and may be a common feature of post orogenic sedimentation

the caledonian metamorphic core an alpine model the neogene evolution of the central swiss alps is outlined and used as an analogue for the grampian orogeny of scotland a direct comparison is made between the three tectonothermal stages which characterize the alps and similar events in the scottish highlands geometric similarities are emphasised using geological cross sections kinematic and mechanistic similarities are inferred a net convergence model which links the metamorphic and uplift denudation history of the alps to its tectonic development in a crustal scale duplex is argued to describe appropriately the history of the dalradian and northern scottish highlands