geochemical and geochronological evidence for early triassic calc alkaline magmatism in the menderes massif western turkey pan african basement rocks and a paleozoic cover series which were intruded by the protoliths of leucocratic orthogneisses have been recognized in the menderes massif located in the western part of the alpine orogenic belt of turkey this geochemical and geochronological study focuses on the evolution of the menderes massif at the end of paleozoic time geochemical data suggest that the crustally derived leucocratic orthogneisses have chemical composition typical of calc alkaline and s type granite zircon grains which are euhedral with typical igneous morphologies were dated by the 207pb 206pb evaporation method single zircon dating of three samples yielded mean 207pb 206pb ages of 246 5 241 5 and 235 6 ma these ages are interpreted as the time of protolith emplacement in triassic geological and geochronological data suggest that leucocratic granites were emplaced in a period following a metamorphic event related to the closure of the paleo tethys the leucocratic granites were metamorphosed during the alpine orogenesis and transformed into orthogneisses the similar triassic magmatic event at 233 2 ma was also occurred using single zircon evaporation method from granitic gneisses which rest upon the migmatites with tectonic contacts in naxos cycladic complex this indicates that the menderes massif and cycladic complex had a common pre early triassic magmatic evolution

variations in alaska tidewater glacier frontal ablation 1985 2013 our incomplete knowledge of the proportion of mass loss due to frontal ablation the sum of ice loss through calving and submarine melt from tidewater glaciers outside of the greenland and antarctic ice sheets has been cited as a major hindrance to accurate predictions of global sea level rise we present a 28 year record 1985 2013 of frontal ablation for 27 alaska tidewater glaciers representing 96 of the total tidewater glacier area in the region calculated from satellite derived ice velocities and modeled estimates of glacier ice thickness we account for cross sectional ice thickness variation long term thickness changes mass lost between an upstream fluxgate and the terminus and mass change due to changes in terminus position the total mean rate of frontal ablation for these 27 glaciers over the period 1985 2013 is 15 11 3 63gta 1 two glaciers hubbard and columbia account for approximately 50 of these losses the regional total ablation has decreased at a rate of 0 14gta 1 over this time period likely due to the slowing and thinning of many of the glaciers in the study area frontal ablation constitutes only 4 of the total annual regional ablation but roughly 20 of net mass loss comparing several commonly used approximations in the calculation of frontal ablation we find that neglecting cross sectional thickness variations severely underestimates frontal ablation

iceberg calving flux and mass balance of the austfonna ice cap on nordaustlandet svalbard 1 satellite radar interferometry 60 mhz airborne ice penetrating radar data and visible band satellite imagery were used to calculate the velocity structure ice thickness and the changing ice marginal extent of austfonna 8000 km2 and 2500 km3 the largest ice cap in the eurasian arctic ice cap motion is generally less than about 10 m a 1 except where faster flowing curvilinear features with velocities of several tens to over 200 m a 1 are present most drainage basins of austfonna have undergone ice marginal retreat over the past few decades at an average of a few tens of meters per year integrating margin change around the whole ice cap gives a total area loss of about 10 km2 a 1 iceberg flux from the marine margins of austfonna is about 2 5 0 5 km3 a 1 water equivalent about 45 of the total calving flux from the whole svalbard archipelago when mass loss by iceberg production is taken into account the total mass balance of austfonna is negative by between about 2 5 and 4 5 km3 a 1 this iceberg flux represents about 33 5 of total annual mass loss from austfonna with the remainder lost through surface ablation iceberg flux should be included in calculations of the total mass balance of the many large arctic ice caps including those located in the russian and canadian arctic that end in tidewater the neglect of this term has led to underestimates of mass loss from these ice caps and thus to underestimates of the contribution of arctic ice caps to global sea level rise

the evolution of the southern menderes massif in sw turkey as revealed by zircon dating this geochronological study concentrates on the evolution of the southern part of the menderes massif a metamorphic core complex in w turkey by dating single zircons with the pb pb evaporation and the u pb methods we have analysed zircons from granitic augen gneisses of the core as well as from quartzites of the metasedimentary envelope zircons from the granitic core gneisses are euhedral with typical igneous morphologies the single zircon ages of these gneisses indicate a time span for magmatic activity from 520 to 570 ma with a major event at about 550 ma some gneisses contain older zircons of c 660 ma which are interpreted as inherited grains zircons from the quartzites are detrital as indicated by their rounded shapes and pitted surfaces their ages vary from 526 to 2094 ma these data partially coincide with the ages of the gneisses but also indicate an older source region for the sediments neither a tertiary origin nor metamorphic overgrowth is documented in the pb ages of the zircons the results suggest that the southern part of the menderes massif developed during a major magmatic episode in latest proterozoic times thus suggesting a relation with other pan african regions in n africa

the structural state of the former lower continental crust in calabria s italy in the northern serre s italy a continuous section through a former lower continental crust is exposed schenk 1984 1985 these granulite facies rocks have not been penetratively deformed during their uplift to higher crustal levels therefore they allow to study the structural state of the lower continental crust most rockforming minerals among them ortho and clinopyroxene and cordierite show recrystallization structures quarz basal subgrain boundaries are developed in lower levels of the lower crust and disappear toward higher levels in addition to dimensional orientations of the rockforming minerals the preferred crystallographic orientations of plagioclases cordierite amphibole pyroxenes and rarely quartz reflect the strain orientation of the prograde high t deformation during this deformation the stretching direction was constant nne ssw throughout the exposed lower crustal section shear indicators are rare this points to the fact that deformation has been homogeneous and coaxial flattening there is only a small variation in orientation and strength of textures throughout the exposed lower crust therefore neighbouring layers of different composition rather than different deformation might serve as seismic reflectors in the former lower crust

glacier velocities and dynamic ice discharge from the queen elizabeth islands nunavut canada recent studies indicate an increase in glacier mass loss from the canadian arctic archipelago as a result of warmer summer air temperatures however no complete assessment of dynamic ice discharge from this region exists we present the first complete surface velocity mapping of all ice masses in the queen elizabeth islands and show that these ice masses discharged 2 6 0 8 gt a 1 of ice to the oceans in winter 2012 approximately 50 of the dynamic discharge was channeled through non surge type trinity and wykeham glaciers alone dynamic discharge of the surge type mittie glacier varied from 0 90 0 09 gt a 1 during its 2003 surge to 0 02 0 02 gt a 1 during quiescence in 2012 highlighting the importance of surge type glaciers for interannual variability in regional mass loss queen elizabeth islands glaciers currently account for 7 5 of reported dynamic discharge from arctic ice masses outside greenland

geochemistry and petrogenesis of intrusive and extrusive ophiolitic plagiogranites central anatolian crystalline complex turkey plagiogranites associated with the sarikaraman ophiolite of the central anatolian crystalline complex turkey closely resemble other plagiogranites from supra subduction zone type ophiolites of neotethys the ophiolite is remarkable in displaying a higher proportion of the plagiogranite suite ca 10 by volume than is usually associated with such bodies the sarikaraman plagiogranites are represented by intrusive sheets and netvein trondhjemites largely developed at the top of the upper gabbros and as multiphase dykes within the sheeted dyke complex the plagiogranite dykes are considered to feed extrusive silicified rhyolites associated with the basaltic lavas in the volcanic section of the ophiolite field relations suggest that the trondhjemites were probably generated from the roof section of a dynamic and evolving gabbroic magma chamber both the deep seated trondhjemites and the volcanic rhyolites constitute the sarikaraman plagiogranite suite geochemically there is complete overlap between the intrusive trondhjemites and extrusive rhyolites which are characterised by morb normalized low hfs element contents with small negative nb ta anomalies and variably enhanced lil element abundances unlike other plagiogranites however the sarikaraman suite is not characterized by consistently low k2o contents a feature that reflects the variable mobilization of the lil elements under lower greenschist facies conditions the ree are uniformly enriched relative to the basic components of the complex but have similar normalized patterns exhibiting mild light ree depletion in terms of their origin the initial or most primitive plagiogranite melts could have been generated by either fractional crystallization 70 85 of clinopyroxene feldspar amphibole or partial melting 5 15 batch melting of a gabbroic source material although only the first process can produce most of the range of the plagiogranite compositions as a group the plagiogranites exhibit some degree of internal variation which can be generated by further fractionation largely dominated by feldspar with minor apatite and amphibole

thermal evolution and exhumation in obliquely convergent transpressive orogens most p t t path models to date have considered a linear erosion rate for exhumation from burial depth related to isostatic readjustment of crustal thickness a few have discussed extension enhanced exhumation erosional exhumation can only restore lower crustal rocks from the thickened mountain root to their previous original depth in the pre collisional crust one major assumption of all models to date is that the compressive forces responsible for crustal thickening cease before elevation and erosion begins however compression is often still active even if the crustal thickening has stopped further compression of the thickened and strongly deformed orogenic root is responsible for forceful exhumation extrusion of softened rocks upwards hence the rate of exhumation is related to the rate of convergence of colliding plates extrusional exhumation can elevate buried rocks to any depth depending on the action of fault shear systems in the extrusional exhumation models examined here the ascending rocks cool faster because they approach the zero temperature surface conditions more rapidly than by isostatic erosion the exhumation rate is also governed by the angle between the plate boundary and the displacement vector implying that the convergent plate boundaries are regarded as complex transpressive systems in which the degree of obliquity can be expressed by the ratio of pure to simple shear components a low ratio of pure simple shear typical for wrench dominated plate boundaries implies long distance horizontal transport from the buried position in the original orogen and longer periods during which metamorphic heating occurs a high ratio of pure simple shear characteristic for frontal like convergence implies a rapid exhumation without significant heating thus granulites barrovian type and blueschist facies metamorphism are characterised by increasing angle of obliquity 10 30 90 respectively the high temperature limit at low ratio of pure simple shear is the geotherm t and lies at temperatures that would commonly be taken to indicate that addition of mantle heat was required to generate hot geotherms and p t t paths wrench faulting over 100 s of kilometres at reasonable slow convergence rates could lead to extensive dehydration melting and granulite formation in large scale collisional orogens

characterizing interannual variability of glacier dynamics and dynamic discharge 1999 2015 for the ice masses of ellesmere and axel heiberg islands nunavut canada landsat 7 and radarsat 1 radarsat 2 satellite images are used to produce the most comprehensive record of glacier motion in the canadian high arctic to date and to characterize spatial and temporal variability in ice flow over the past 15 years this allows us to assess whether dynamically driven glacier change can be attributed to surging or pulsing or whether other mechanisms are involved radar velocity mapping allows annual regional dynamic discharge iceberg calving to be calculated for 2000 and the period 2011 2015 yielding a mean regional discharge of 2 21 0 68 gt a 1 and velocities derived from feature tracking of optical imagery allow for annual dynamic discharge to be calculated for select glaciers from 1999 to 2010 since 2011 several of the major tidewater terminating glaciers within the region have decelerated and their dynamic discharge has decreased trinity and wykeham glaciers prince of wales icefield represent a notable departure from this pattern as they have generally accelerated over the study period the resulting increase in dynamic discharge from these glaciers entirely compensates within error limits for the decrease in discharge from the other tidewater glaciers across the study region these two glaciers accounted for 62 of total regional dynamic discharge in winter 2015 compared to 22 in 2000 demonstrating that total ice discharge from the canadian high arctic can be sensitive to variations in flow of just a few tidewater glaciers

mass balance of the greenland ice sheet at high elevations comparison of ice discharge from higher elevation areas of the entire greenland ice sheet with total snow accumulation gives estimates of ice thickening rates over the past few decades on average the region has been in balance but with thickening of 21 centimeters per year in the southwest and thinning of 30 centimeters per year in the southeast the north of the ice sheet shows less variability with average thickening of 2 centimeters per year in the northeast and thinning of about 5 centimeters per year in the northwest these results agree well with those from repeated altimeter surveys except in the extreme south where we find substantially higher rates of both thickening and thinning

basin scale partitioning of greenland ice sheet mass balance components 2007 2011 a r t i c l e i n f o a b s t r a c t the current deficit in greenland ice sheet mass balance is due to both a decrease in surface mass balance smb input and an increase in ice discharge d output while smb processes are beginning to be well captured by observationally constrained climate modeling insight into d is relatively limited we use insar derived velocities in combination with ice thickness observations to quantify the mass flux f across a flux perimeter around the ice sheet at 1700 m elevation to quantify d we correct f for smb as well as changes in volume due to ice dynamics in the area downstream of the gate using a 1961 1990 reference climatology smb field from the mar regional climate model we quantify ice sheet mass balance within eighteen basins we find a 2007 2011 mean d of 515 57 gt yr 1 we find a 2007 2011 mean total mass balance of 262 21 gt yr 1

stretching lineations in transpressional shear zones an example from the sierra nevada batholith california abstract ductile shear zones and associated stretching lineations are generally considered to be the result of two dimensional simple shear deformations with stretching lineations interpreted to rotate into parallelism with the direction of tectonic transport with increasing deformation however stretching lineations perpendicular to the inferred tectonic transport direction are displayed by some shear zones field studies in the sierra nevada batholith have revealed a single shear zone the rosy finch gem lake shear zone that contains both steeply plunging stretching lineations in older metamorphosed sedimentary and granitic rocks and shallowly plunging stretching lineations in syntectonic granitoids dextral sense of shear indicators are found in all these units and deformation occurred simultaneously along the length of the shear zone theoretical strain modeling indicates that stretching lineations can be either horizontal or vertical within transpressional shear zones to investigate the kinematics of three dimensional deformation we examine the role of stretching lineations which form as a result of finite strain including the possibility of partitioning a component of the strike slip movement onto shear bands comparing the field data with the strain modeling we interpret the along strike variation in lineation behavior within the rosy finch gem lake shear zone to be a result of the differences in finite strain recorded by different units the older units showing steeply plunging lineation have recorded more finite strain across a narrower shear zone than the syntectonic granites which record shallowly plunging lineations we conclude that the orientation of the lineation within transpressional shear zones does not necessarily correlate with the transport direction but may reflect along strike variations in finite strain and or strain partitioning

geology of the bozdag area central menderes massif sw turkey pan african basement and alpine deformation the menderes massif consists of a precambrian core series that preserves evidence for a polymetamorphic history and a paleozoic mesozoic cover series that experienced only the alpine tectonometamorphic evolution structural petrographic and geochronologic investigations in the central menderes massif demonstrate that a part of the metamorphic and structural evolution of the precambrian basement is older than the undeformed 551 1 4 ma old birgi metagranite and b inferred alpine fabrics overprinting the cover series largely have the same attitudes as the old structures in the much older core series the inferred alpine fabrics include both contractional and extensional structures contraction under greenschist to amphibolite facies conditions resulted in the imbrication of the core and cover series and generated an inverted metamorphic sequence by north directed thrusting during alpine extension most of the south dipping thrust faults were reactivated as extensional shear zones under decreasing greenschist facies conditions

the distribution and flow characteristics of surge type glaciers in the canadian high arctic a systematic review of 1959 60 aerial photography and 1999 2000 landsat 7 imagery has identified 51 surge type polythermal glaciers in the canadian high arctic these were identified from the presence of features such as looped medial moraines intense folding visible at the surface rapid terminus advance heavy surface crevassing and high surface velocities these observations suggest that surging glaciers are much more common than previously believed in the canadian high arctic where only six surge type glaciers have previously been described of the 51 surge type glaciers identified in this study 15 were observed in the active phase in the 1959 60 and or 1999 2000 imagery the most dramatic advances have occurred on western axel heiberg island where iceberg good friday bay and airdrop glaciers have all advanced by 4 7 km between1959 and 1999 for glaciers with repeat landsat 7 coverage from 1999 and 2000 image correlation software was used to determine the magnitude and spatial distribution of surge velocities for example mittie glacier on manson icefield was moving at a rate of up to 1 kma over a distance of at least 25 km back from its terminus the terminus of this glacier has advanced by at least 4 km since 1959 and the glacier was observed to be heavily crevassed during overflights in april 2000 with clear signs of surface lowering of 10 25 m indicated by a strandline

southern menderes massif an incipient metamorphic core complex in western anatolia turkey in the southern sector of the menderes massif north of selimiye milas augen gneisses interpreted as a deformed peraluminous granite have been dynamothermally metamorphosed and are surrounded by and intrude a regionally metamorphosed palaeozoic envelope the granitic rocks exhibit a moderately dipping mylonitic foliation and nne ssw trending mineral elongation lineation the progressive deformation of the granitic rocks produces a structural sequence typical of an extensional shear zone marked from bottom to top by a very thick extensive zone of mylonites followed in turn by brecciated mylonite and cataclasite the kinematic indicators exhibit a top to the south down dip sense of shear these structures are attributed to exhumation of the granitic rocks of the massif along a major south dipping normal sense shear zone that accommodated crustal extension during late oligocene collapse of the orogen in western turkey thus the southern menderes massif may be interpreted as the exhumed footwall of a major extensional shear zone and possibly as an incipient core complex

form and flow of the devon island ice cap canadian arctic 1 in this study 3370 km of 100 mhz ice penetrating radar data were acquired from devon ice cap arctic canada bed returns were obtained from 90 of flight tracks mean crossing point errors in ice surface elevation and ice thickness were 7 8 m digital elevation models of ice cap surface and bed elevation and ice thickness were produced and can be used as boundary conditions in numerical modeling devon ice cap including 1960 km2 of contiguous stagnant ice to its west is 14 010 km2 the ice cap proper is 12 050 km2 its largest drainage basin is 2630 km2 the ice cap crest has a maximum measured elevation of 1921 m maximum recorded ice thickness is 880 m ice cap volume is 3980 km3 about 10 mm sea level equivalent the bed 8 of which lies below sea level is an upland plateau dissected by steep sided valleys that control the locations of the major outlet glaciers which dominate ice cap drainage about 73 km 4 of the ice cap margin ends in tidewater the margin is not floating icebergs of 100 m were observed offshore only a single outlet glacier showed signs of past surge activity all major outlet glaciers along the eastern ice cap margin have retreated 1 3 km since 1960 synthetic aperture radar interferometic velocity structure shows slow undifferentiated flow predominating in the west and center with fast flowing outlet glaciers and intervening slow flowing ridges typical elsewhere outlet glacier velocities are 7 10 times higher than in areas of undifferentiated flow this velocity structure of fast flowing units within slower flowing ice appears typical of many large 103 km2 arctic ice caps

intra and inter annual variability in dynamic discharge from the academy of sciences ice cap severnaya zemlya russian arctic and its role in modulating mass balance

regional and global volumes of glaciers derived from statistical upscaling of glacier inventory data 1 very few global scale ice volume estimates are available for mountain glaciers and ice caps although such estimates are crucial for any attempts to project their contribution to sea level rise in the future we present a statistical method for deriving regional and global ice volumes from regional glacier area distributions and volume area scaling using glacier area data from 123 000 glaciers from a recently extended world glacier inventory we compute glacier volumes and their sea level equivalent sle for 19 glacierized regions containing all mountain glaciers and ice caps on earth on the basis of total glacierized area of 741 103 68 103 km2 we estimate a total ice volume of 241 103 29 103 km3 corresponding to 0 60 0 07 m sle of which 32 is due to glaciers in greenland and antarctica apart from the ice sheets however our estimate is sensitive to assumptions on volume area scaling coefficients and glacier area distributions in the regions that are poorly inventoried i e antarctica north america greenland and patagonia this emphasizes the need for more volume observations especially of large glaciers and a more complete world glacier inventory in order to reduce uncertainties and to arrive at firmer volume estimates for all mountain glaciers and ice caps

fabric stability in oblique convergence and divergence forward modeling of transpression transtension assuming homogeneous strain and a direct relationship between finite strain axes and foliation lineation in tectonites investigates fields of stability of foliation and lineation orientations in oblique convergence and divergence vertical foliation horizontal lineation vf hl develop for angles of convergence divergence between 0 and 20 with increasing finite strain this narrow window of stability is further reduced lineation switches to vertical in transpression and foliation switches to horizontal in transtension if a shear zone contains vf hl it either developed as a zone very close to pure wrenching or recorded low finite strain the stability of vf hl at high strain and higher angles of convergence is enhanced by lateral extrusion of material along transpression zones vf hl may be stabilized in magmatic bodies that progressively intrude transtension zones if the wrench component of deformation partitions within them alternatively if these bodies are dike like cool fast and do not record large deformation they take up the extension component of transtension through anisotropic volume addition leaving a larger component of wrench deformation in the country rocks this effect stabilizes vf hl effectively at low strain but only marginally so at high strain

a revised stratigraphic framework for later cenozoic sequences in the northeastern mediterranean region this study describes the lithostratigraphic character of mid cenozoic oligocene pliocene sequences in different parts of the northeastern mediterranean area and offers a detailed stratigraphic correlation for this region the sequences concerned are drawn from the camardi area south central anatolia the adana basin the misis mountains and the kyrenia range northern cyprus and the submerged florence rise west of cyprus the stratigraphic relationships identified here indicate the following a following the middle eocene lutetian regression there was uplift throughout the entire region b episodes of fluvial and lacustrine deposition in intramontane settings ensued in most of this region during the late eocene early miocene interval c following a regionally extensive phase of tectonic compression major marine transgression commenced in the late oligocene in northern cyprus and in the early miocene in adjacent southern turkey with the exception of the ecemi fault zone where continental deposition continued d these oligo miocene transgressive sequences comprise a broadly diachronous complex of both shallow and deeper marine facies including reefal carbonates littoral clastics basinal shales and fan turbidites e deeper marine miocene facies persisted longer in the misis area and in northern cyprus f a regional regression occurred throughout most of the area during the late serravallian to tortonian interval and is marked by the abrupt locally discordant appearance of extensive shallow marine deltaic and fluvial deposits g continued regression in the messinian led to the formation of significant evaporite deposits in the western and southern parts of the region but localized uplift of the misis area is attested by the initial deformation of the neogene rocks there and the absence of messinian sediments from this area h in the pliocene there was extensive emergence of the northern parts of the region interrupted by brief marine incursions the present day drainage pattern was established at this time i marine conditions persisted longer in northern cyprus where emergence occurred only in the latest pliocene

a new intracontinental transcurrent structure the central anatolian fault zone turkey abstract recent neotectonic studies including remote sensing aerial photographs geological field mapping on various scales and measured stratigraphic section substantiate the existence of a large sinistral intracontinental transcurrent structure which we call the central anatolian fault zone cafz this is an approximately 730 km long 2 km to 80 km wide ne trending active sinistral strike slip fault zone that cuts across the anatolian plateau between duzyayla in the northeast and anamur county in the southwest it continues onward beneath the eastern mediterranean sea and determines the boundary of the antalya and adana basins as far as to the west of cyprus the cafz is a very young neotectonic structure it resulted from the reactivation and propagation of an older paleotectonic structure the so called ecemi s corridor in both nne and sw directions across the inner tauride suture in the plio quaternary times based on geometric discontinuities the cafz is divided into 24 segments each of them is characterized by a number of strike slip morphotectonic features reflecting recent motions the easternmost part of the anatolian platelet is being deformed internally by several dextral to sinistral intraplate strike slip faults these are the lake salt fault zone lsfz the salanda fault sf the cafz the goksu yazyurdu fault zone gyfz and the malatya ovacik fault zone mofz they take up lesser motion and are younger than boundary faults of the anatolian platelet the gyfz and mofz splay from the natf cut across the anatolian platelet and then meet to the eatf whereas other faults are confined into the anatolian platelet and seem to be independent structures however present day structural pattern of all these intraplate faults and boundary faults of the anatolian platelet indicates a regional strain pattern of nnw sse directed shortening and ene wsw directed extension and they seem to have developed to accommodate northward motion of the arabian plate since late early pliocene times

glacier velocities and dynamic discharge from the ice masses of baffin island and bylot island nunavut canada speckle tracking of alos palsar fine beam data from 2007 2011 are used to determine the surface motion of major ice masses on baffin island and bylot island in the southern canadian arctic archipelago glacier velocities are low overall with peaks of 100 m a 1 and means of 20 60 m a 1 common along the main trunk of many outlet glaciers peak velocities on penny and bylot island ice caps tend to occur near the mid sections of their primary outlet glaciers while the fastest velocities on all other glaciers usually occur near their termini due to relatively large accumulation areas draining through narrow outlets estimates of ice thickness at the fronts of tidewater terminating glaciers are combined with the velocity measurements to determine a regional dynamic discharge rate of between 17 mt a 1 and 108 mt a 1 with a mid point estimate of 55 mt a 1 revising downward previous approximations these velocities can be used as inputs for glacier flow models and provide a baseline dataset against which

core complex development in central anatolia turkey tectonic models for the central anatolian segment of the alpine himalayan orogen have not considered this region as part of the aegean extensional province we have found evidence however for oligocene miocene extension and exhumation of midcrustal rocks in a metamorphic dome nigde massif that is structurally and petrologically similar to miocene core complexes 500 km to the west strong correspondence in the timing and kinematic development of the menderes western turkey and nigde core complexes suggests that extensional tectonics and exhumation of mid to lower crustal rocks affected much of the eastern mediterranean region in the nigde massif supracrustal rocks were buried to depths of 16 20 km at high temperatures 700 c during contraction associated with closure of neo tethyan seaways in late mesozoic early cenozoic time following cooling and decompression to 600 c and 10 km metasedimentary rocks underwent a second heating event at low pressures during miocene magmatism that postdated much of the unroofing of the massif development of the nigde core complex was related to exhumation of thickened and thermally weakened continental crust in the upper plate of a north dipping subduction zone the partial subduction of the tauride carbonate platform in the eocene resulted in choking of the subduction zone followed by isostatic rebound and exhumation of the buoyant platform this in turn caused a rapid emergence of the upper plate resulting in erosion of upper crustal rocks and exhumation of midcrustal rocks along the northern edge of the inner tauride suture zone although northern regions of central anatolia contain the same protoliths as the nigde massif and underwent extensive tertiary magmatism they did not undergo similar extension suggesting that core complex development in south central turkey was controlled by the location of thickened and thermally weakened crust adjacent to a suture zone

timing of tectonic events in the menderes massif western turkey implications for tectonic evolution and evidence for pan african basement in turkey the menderes massif forms the western of the two large metamorphic culminations within the turkish alpide orogen it has three major lithologic units with a gneissic core at the base and a schist and a marble envelope overlying it successively although relations between them have been largely obscured by the polymetamorphic and structurally complex history of the massif we present a review of the available stratigraphic evidence and combine it with new isotopic ages from the central and southern parts of the massif to constrain the timing of major tectonic events that shaped the massif since the late proterozoic pt3 in the southern part of the massif sensu stricto three episodes of deformation and metamorphism are distinguished whereas in its northern part there are four the first episode occurred at 500 10 ma with intense deformation and metamorphism at high grade amphibolite facies with local anatexis in the central part of the massif the 470 9 ma old now highly deformed tonalitic and granitic intrusions mark the end of this episode on a cambrian reconstruction of continents around the eastern mediterranean the menderes massif forms the southern end of the pan african orogenic collage of northeastern africa and arabia the area of earliest palaeozoic deformation in the menderes may connect with the northwest african orogenic collage along the strike via the bozburun and saricicek diabases arkoses and schists in the center of the karacahisar dome interpreted herein as fragments of a pan african suture the earliest palaeozoic deformations to affect the rocks were probably related to the last pan african collisions and associated postcollisional convergence the southern part of the massif was undeformed from early ordovician to the early later eocene whereas the northern part was deformed metamorphosed and intruded possibly during the late triassic related to the closure of the karakaya marginal basin of palaeo tethys the next major event affecting the whole of the massif was the intense deformation and widespread metamorphism that reached high amphibolite grade in the structurally lower parts and only greenschist grade in the outermost envelope this metamorphism here called the main menderes metamorphism mmm is biostratigraphically constrained between early eocene and early oligocene time rb sr isotopic data show a spread of ages between 60 ma and 25 ma with the greatest number of determinations around 35 5 ma this number is in excellent agreement with the stratigraphic evidence and shows that mmm took place during latest eocene time or at the transition from eocene to oligocene time along the northern border of the massif deformation and metamorphism had already taken place during the late cretaceous in a high pressure low temperature hp lt metamorphic belt northernmost part of menderes massif sensu lato which was then covered by palaeocene molasse the evolution of the hp lt belt was probably related to the obduction of the bozkir ophiolites from the izmir ankara branch of the neo tethys ocean and preceded terminal collision in the evolution of the massif the mmm was a product of the latest palaeocene collision across neo tethys and the consequent internal imbrication of the menderes taurus block that resulted in the burial of the menderes massif area beneath the lycian nappe complex a low grade metamorphic event dated at 10 to 5 ma is interpreted to be related to the extensional deformation in the aegean and western turkey which has been dated stratigraphically to have begun during the tortonian 11 5 ma

structural interpretation of gabbroic rocks in agacoren granitoid central turkey field observations and aeromagnetic data gabbroic rocks crop out commonly in different localities of the central anatolian crystalline complex and are interpreted by many researchers as the remnants of a neotethyan ophiolitic suite now observed as roof pendants in the granitoids of the complex in this study the structural position of the gabbroic rocks within one of the granitoids of the central anatolian crystalline complex namely the agacoren granitoid is determined by geological and aeromagnetic data from the central part of the pluton the gabbroic rocks have sinuous contacts with the agacoren granitoid and they display a gradual change in composition and texture from gabbro at the top of the hills to diorite at the foot of the hills towards the contact with granitoid power spectra high and low pass filtered aeromagnetic and pseudogravimetric anomalies were produced using geophysical methods a two dimensional model constructed from the high pass filtered anomalies with the control of the in situ susceptibility data and the low pass filtered anomaly suggests existence of a shallow conical shaped and deeply buried gabbroic body the deep body extends down to deeper levels of the upper crust and given the textural and compositional features which suggest magma mixing is interpreted as an intrusion coeval with the agacoren granitoid

intrusion age of pan african augen gneisses in the southern menderes massif and the age of cooling after alpine ductile extensional deformation

flow dynamics and iceberg calving rates of devon ice cap nunavut canada the surface velocity field of devon ice cap nunavut canada was mapped using interferometric synthetic aperture radar insar ascending european remote sensing satellite 1 and 2 ers 1 2 tandem mode data were used for the western and southeast sectors and 3 day repeat pass ers 1 imagery for the northeast sector speckle tracking procedures were used with radarsat 1 imagery to obtain surface velocities over the terminus of belcher glacier a major calving front where decorrelation between ers data occurred the insar data highlight a significant contrast in ice flow dynamics between the east and west sides of the ice cap ice movement west of the main north south divide is dominated by relatively uniform sheet flow but three fast flowing outlet glaciers that extend 14 23 km beyond the ice cap margin also drain this region several outlet glaciers that extend up to 60km inland from the eastern margin drain the eastern side of the ice cap the dominant ice flow regimes were classified based on the relationship between the driving stress averaged over a length scale often ice thicknesses and the ratio of surface velocity to ice thickness the mapped distribution of flow regimes appears to depict the spatial extent of basal sliding across the ice cap this is supported by a close relationship between the occurrence of flow stripes on the ice surface and flow regimes where basal sliding was found to be an important component of the glacier motion iceberg calving rates were computed using measured surface velocities and ice thicknesses derived from airborne radio echo sounding the volume of ice calved between 1960 and 1999 was estimated to be 20 5 4 7 km 3 or 0 57km 3 a 1 approximately 89 of this loss occurred along the eastern margin the largest single source is belcher glacier which accounts for 50 of the total amount of ice calved

metamorphism of the central anatolian crystalline complex turkey influence of orogen normal collision vs wrench dominated tectonics on p t t paths the central anatolian crystalline complex cacc is a microcontinent in the alpine himalayan belt it has previously been considered as a coherent structural entity but although the entire cacc is comprised of similar rocks primarily metasedimentary rocks and granitoids it consists of at least four tectonic blocks characterized by different p t t paths these blocks are the kirsehir north west akdag north east nigde south and aksaray west massifs the northern massifs experienced thrusting and folding during collision and were slowly exhumed by erosion metamorphic rocks are characterized by clockwise p t paths at moderate p t and local low p high t lp ht overprinting in the highest grade rocks apatite fission track ages are eocene to oligocene 47 32 ma the aksaray block represents the hot shallow mid crust of a late cretaceous early tertiary arc it is dominated by intrusions rare metapelitic rocks record low p 4 kbar regional metamorphism overprinted by lp ht contact metamorphism apatite fission track ages are 50 45 ma the nigde massif is different from the other cacc blocks because it evolved as a core complex in a wrench dominated setting it is characterized by clockwise p t paths at moderate p t followed by widespread lp ht metamorphism apatite fission track ages are miocene 12 9 ma significantly younger than those in the northern massifs nigde rocks resided in the mid crust at a time when the rest of the cacc was at or near the earth s surface variations in p t t and tectonic histories especially timing of exhumation between the northern and southern cacc reflect the difference between head on collision vs mid crustal wrenching

glacier motion estimation using sar offset tracking procedures two image to image patch offset techniques for estimating feature motion between satellite synthetic aperture radar sar images are discussed intensity tracking based on patch intensity cross correlation optimization and coherence tracking based on patch coherence optimization are used to estimate the movement of glacier surfaces between two sar images in both slant range and azimuth direction the accuracy and application range of the two methods are examined in the case of the surge of monacobreen in northern svalbard between 1992 and 1996 offset tracking procedures of sar images are an alternative to differential sar interferometry for the estimation of glacier motion when differential sar interferometry is limited by loss of coherence i e in the case of rapid and incoherent flow and of large acquisition time intervals between the two sar images in addition an offset tracking procedure in the azimuth direction may be combined with differential sar interferometry in the slant range direction in order to retrieve a two dimensional displacement map when sar data of only one orbit configuration are available

the deformation matrix for simultaneous simple shearing pure shearing and volume change and its application to transpression transtension tectonics simultaneous simple shearing and pure shearing with or without additional volume change can be combined into a single upper triangular deformation matrix the off diagonal term is named the effective shear strain and is a simple function of the pure shearing and simple shearing components a three dimensional deformation matrix for the simultaneous combination of coaxial deformation with or without additional volume change and up to three simple shearing systems with mutually orthogonal shear planes is also presented by using this matrix one can easily extract the various properties of incremental as well as finite strain and the progressive as well as finite rotation of passive markers during deformation the case of transpression transtension is revised using the unified deformation matrix the orientation of the major axis of the strain ellipsoid 1 is always horizontal if the deformation is transtensional switches from horizontal to vertical during transpressional wrenching 1 wk 0 81 for constant vorticity deformations and is always vertical for highly transpressional deformations wk 0 81 for transpression material lines initially rotate towards the horizontal shearing direction but generally turn to rotate towards the vertical axis after a certain strain for transtension all material lines rotate towards a direction in the horizontal plane which is oblique to the shearing direction

comment on a new intracontinental transcurrent structure the central anatolian fault zone turkey by a kocyigit and a beyhan abstract kocyigit and beyhan have described the central anatolian fault zone cafz as a 700 km long active strike slip fault zone in turkey if their interpretation is correct then several major turkish cities are vulnerable to a significant earthquake hazard which was previously unsuspected and the existing close agreement between observed slip rates on major strike slip faults in turkey and predictions from global plate motion models is spurious whether the cafz is real or based on mistaken interpretations of diverse evidence is thus a matter of some importance the aim of this comment is to describe difficulties which arise over the published interpretation of the cafz with the aim of encouraging either a retraction or a more thorough presentation of the available evidence in support of the existence of a major active fault zone in the required position three main difficulties are discussed in detail first strands of the cafz have been interpreted in many localities where previous detailed studies have either found no evidence of faulting or have reported ancient faults which have been described as no longer active second many other features which previous studies have explained satisfactorily are reinterpreted as consequences of active strike slip faulting finally no observational evidence is presented for the slip rate or the timing of the start of the alleged present phase of slip on the cafz the suggestion that it has slipped by 24 km during this present phase of activity is inadequately documented and conflicts with other evidence

ice discharge error estimates using different cross sectional area approaches a case study for the canadian high arctic 2016 17 we analyse the various error sources in the estimation of ice discharge through flux gates distinguishing the cases with ice thickness data available for glacier cross sections or only along the centreline for the latter we analyse the performance of three u shaped cross sectional approaches we apply this methodology to glaciers of the canadian high arctic the velocity field is the main error source for small and medium size glaciers discharge 100 mt a 1 with high velocities 100 m a 1 the error in crosssectional area dominates thinning thickening between ice thickness and velocity measurements should be considered as it implies systematic errors up to 8 in our study the u shaped parabolic approach which allows for an adjusted estimation when the ice thickness measurement point is displaced from the glacier centreline performs best with small bias and admissible standard error we observe an increase of ice discharge from the main glaciers trinity and wykeham of the prince of wales icefield from 2015 to 2016 by 5 and 20 respectively followed by a decrease in 2017 by 10 and 15 respectively belcher glacier of the devon ice cap maintains similar discharges during 2015 17

structural and metamorphic evolution of the northern part of the menderes massif new data from the derbent area and their implication for the tectonics of the massif the menderes massif represents the western part of the metamorphic axis of the alpide orogen of anatolia asia minor a restricted area in its poorly known northern part around the village of derbent was studied to shed some light on its geological evolution and to compare it with that of the southern part of the massif in the derbent area three lithologic groups are recognized on the basis of their lithology and structural position namely the gneiss and the schist complexes and the marbles petrographic mineralogic and structural data indicate that the schist complex and the overlying marbles have undergone at least three phases of deformation and metamorphism the first phase probably reflects the closure of the karakaya marginal basin located to the north of the present menderes massif during the late triassic the traces of the first phase have been largely obliterated by the second phase which led to amphibolite facies metamorphism a pronounced flat lying foliation and a nne ssw trending

the randolph glacier inventory a globally complete inventory of glaciers the randolph glacier inventory rgi is a globally complete collection of digital outlines of glaciers excluding the ice sheets developed to meet the needs of the fifth assessment of the intergovernmental panel on climate change for estimates of past and future mass balance the rgi was created with limited resources in a short period priority was given to completeness of coverage but a limited uniform set of attributes is attached to each of the 198 000 glaciers in its latest version 3 2 satellite imagery from 1999 2010 provided most of the outlines their total extent is estimated as 726 800 34 000 km 2 the uncertainty about 5 is derived from careful single glacier and basin scale uncertainty estimates and comparisons with inventories that were not sources for the rgi the main contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover these errors appear not to be normally distributed and quantifying them reliably is an unsolved problem combined with digital elevation models the rgi glacier outlines yield hypsometries that can be com bined with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers the rgi has already proved its value in the generation of significantly improved aggregate estimates of glacier mass changes and total volume and thus actual and potential contributions to sea level rise

sharply increased mass loss from glaciers and ice caps in the canadian arctic archipelago the canadian arctic archipelago contains one third of the global volume of land ice outside the ice sheets but its contribution to sea level change is largely unknown gardner et al use three independent techniques to reveal that mass loss from the archipelago was 92 12 gigatonnes per year in 2007 09 about three times greater than in 2004 06 and coincident with warmer summer temperatures the record is too short to allow a firm conclusion on longer term trends but it is clear that the canadian arctic archipelago is a significant contributor to sea level rise mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond1 2 3 4 5 the canadian arctic archipelago located off the northwestern shore of greenland contains one third of the global volume of land ice outside the ice sheets6 but its contribution to sea level change remains largely unknown here we show that the canadian arctic archipelago has recently lost 61 7 gigatonnes per year gt yr 1 of ice contributing 0 17 0 02 mm yr 1 to sea level rise our estimates are of regional mass changes for the ice caps and glaciers of the canadian arctic archipelago referring to the years 2004 to 2009 and are based on three independent approaches surface mass budget modelling plus an estimate of ice discharge smb d repeat satellite laser altimetry icesat and repeat satellite gravimetry grace all three approaches show consistent and large mass loss estimates between the periods 2004 2006 and 2007 2009 the rate of mass loss sharply increased from 31 8 gt yr 1 to 92 12 gt yr 1 in direct response to warmer summer temperatures to which rates of ice loss are highly sensitive 64 14 gt yr 1 per 1 k increase the duration of the study is too short to establish a long term trend but for 2007 2009 the increase in the rate of mass loss makes the canadian arctic archipelago the single largest contributor to eustatic sea level rise outside greenland and antarctica

a method to estimate the ice volume and ice thickness distribution of alpine glaciers sound knowledge of the ice volume and ice thickness distribution of a glacier is essential for many glaciological applications however direct measurements of ice thickness are laborious not feasible everywhere and necessarily restricted to a small number of glaciers in this paper we present a method to estimate the ice thickness distribution and the total ice volume of alpine glaciers this method is based on glacier mass turnover and principles of ice flow mechanics the required input data are the glacier surface topography the glacier outline and a set of borders delineating different ice flow catchments three parameters describe the distribution of the apparent mass balance which is defined as the difference between the glacier surface mass balance and the rate of ice thickness change and two parameters define the ice flow dynamics the method was developed and validated on four alpine glaciers located in switzerland for which the bedrock topography is partially known from radio echo soundings the ice thickness along 82 cross profiles can be reproduced with an average deviation of about 25 between the calculated and the measured ice thickness the cross sectional areas differ by less than 20 on average this shows the potential of the method for estimating the ice thickness distribution of alpine glaciers without the use of direct measurements

form and flow of the academy of sciences ice cap severnaya zemlya russian high arctic 1 the 5 575 km2 academy of sciences ice cap is the largest in the russian arctic a 100 mhz airborne radar digital landsat imagery and satellite synthetic aperture radar sar interferometry are used to investigate its form and flow including the proportion of mass lost through iceberg calving the ice cap was covered by a 10 km spaced grid of radar flight paths and the central portion was covered by a grid at 5 km intervals a total of 1 657 km of radar data digital elevation models dems of ice surface elevation ice thickness and bed elevation data sets were produced cell size 500 m the dems were used in the selection of a deep ice core drill site total ice cap volume is 2 184 km3 5 5 mm sea level equivalent the ice cap has a single dome reaching 749 m maximum ice thickness is 819 m about 200 km or 42 of the ice margin is marine about 50 of the ice cap bed is below sea level the central divide of the ice cap and several major drainage basins in the south and east of the ice cap and of up to 975 km2 are delimited from satellite imagery there is no evidence of past surge activity on the ice cap sar interferometric fringes and phase unwrapped velocities for the whole ice cap indicate slow flow in the interior and much of the margin punctuated by four fast flowing features with lateral shear zones and maximum velocity of 140 m yr 1 these ice streams extend back into the slower moving ice to within 5 10 km of the ice cap crest they have lengths of 17 37 km and widths of 4 8 km mass flux from these ice streams is 0 54 km3 yr 1 tabular icebergs up to 1 7 km long are produced total iceberg flux from the ice cap is 0 65 km3 yr 1 and probably represents 40 of the overall mass loss with the remainder coming from surface melting driving stresses are generally lowest 40 kpa close to the ice cap divides and in several of the ice streams ice stream motion is likely to include a significant basal component and may involve deformable marine sediments

prism and basal plane parallel subgrain boundaries in quartz a microstructural geothermobarometer empirical data on quartz subgrain patterns from various metamorphic rocks show that at least up to 10 kbar in the stability field of low quartz prismatic subgrain boundaries are dominant whereas basal subgrain boundaries are not developed in the high quartz stability field both prismatic and basal subgrain boundaries occur and form typical rectangular chessboard patterns the likely reason behind the different occurrence of these subgrain patterns is that in high quartz prismatic glide becomes as easy as or probably even easier than basal glide the two types of subgrain patterns can be clearly distinguished by optical microscopy consequently the occurrence of chessboard subgrain patterns in quartz represents a practicable geothermobarometer the possibilities of its application are far reaching and include the specification of deformation conditions at high grade metamorphism the recognition of syntectonic intrusions and the distinction between pluton emplacement at lower and at higher crustal levels

mass balance of the greenland ice sheet from 1958 to 2007 we combine estimates of the surface mass balance smb of the greenland ice sheet for years 1958 to 2007 with measurements of the temporal variability in ice discharge d to deduce the total ice sheet mass balance during that time period we find a robust correlation r2 0 83 between anomalies in smb and in d which we use to reconstruct a continuous series of total ice sheet mass balance we find that the ice sheet was losing 110 70 gt yr in the 1960s 30 50 gt yr or near balance in the 1970s 1980s and 97 47 gt yr in 1996 increasing rapidly to 267 38 gt yr in 2007 multi year variations in ice discharge themselves related to variations in smb cause 60 20 more variation in total mass balance smb and therefore dominate the ice sheet mass budget copyright 2008 by the american geophysical union

plagioclase relations in pelites central menderes massif turkey i the peristerite gap with coexisting kyanite in pelites of the central menderes massif albite and oligoclase with only slight chemical zoning coexist in apparent textural equilibrium in the garnet zone staurolite zone and staurolite kyanite transition zone the metamorphic temperature range is estimated as approximately 440 550 c from the hodges spear calibration of the garnet biotite geo thermometer or 440 500 c ganguly saxena calibration while oligoclase composition at the peristerite gap changes from an22 to an14 albite also becomes more sodic an1 5 an0 6 the slope of the albite limb is thus the reverse of that reported in other areas and may not be a true equilibrium feature occurrence of kyanite at temperatures below the crest of the gap is due to low water activity in the presence of graphite ah2o is estimated at approximately 0 1 0 2 from the na content of muscovite coexisting with albite kyanite quartz

the origin and evolution of the menderes massif w turkey a rubidium strontium and oxygen isotope study the menderes massif located in the alpine orogen of western turkey has three litho structural units a basal gneiss core a schist mantle covering the gneiss core and an overlying marble mantle this study reports isotopic data from samples of metasediments and migmatites from the southern type a and of tonalitic to granitic metaigneous rocks from the northern menderes massif type b type a rocks define a rb sr whole rock isochron age of 502 10 ma and an initial87sr 86sr ratio of 0 71174 73 this is interpreted as the age of migmatization type b rocks give a rb sr whole rock isochron age of 471 9 ma with an initial87sr 86sr ratio of 0 70684 25 which we interpret as the intrusion age k white micas from rock type a give an average rb sr mineral age of 56 1 ma which can be interpreted as the formation age of the alpine mineral paragenesis k white micas from rock type b give rb sr mixed ages of 120 230 ma between alpine and pan african orogenies biotites from both rock types yield an average rb sr age of 37 1 ma which is interpreted as an alpine cooling age the oxygen isotope ratios of type a rocks range from 10 4 to 14 6 and of type b from 8 9 to 11 8 the oxygen and strontium isotopic compositions together clearly distinguish rocks of types a and b compositions of type a rocks suggest a crustal origin type b rocks have compositions transitional between those of crustal and mantle derived materials

surface velocity and ice discharge of the ice cap on king george island antarctica glaciers on king george island antarctica have shown retreat and surface lowering in recent decades concurrent with increasing air temperatures a large portion of the glacier perimeter is ocean terminating suggesting possible large mass losses due to calving and submarine melting here we estimate the ice discharge into the ocean for the king george island ice cap l band synthetic aperture radar images covering the time span january 2008 to january 2011 over king george island are processed using an intensity tracking algorithm to obtain surface velocity measurements pixel offsets from 40 pairs of radar images are analysed and inverted to estimate a weighted average surface velocity field ice thicknesses are derived from simple principles of ice flow mechanics using the computed surface velocity fields and in situ thickness data the maximum ice surface speeds reach 225 m a 1 and the total ice discharge for the analysed flux gates of king george island is estimated to be 0 720 0 428 gt a 1 corresponding to a specific mass loss of 0 64 0 38 m w e a 1 over the area of the entire ice cap 1127 km 2

iceberg calving rates from northern ellesmere island ice caps canadian arctic 1999 2003 optical satellite imagery was used to estimate glacier surface velocities and iceberg calving rates from agassiz and western grant ice caps nunavut canada between 1999 and 2003 the largest mean annual surface velocities ranged from 400 to 700 m a 1 but velocities in the 100 200 m a 1 range were common summer velocities were up to an order of magnitude larger than annually averaged velocities the highest velocity 1530 m a 1 was measured on the floating tongue of lake tuborg glacier between 19 july and 19 august 2001 calving rates from individual glaciers varied by up to a factor of two between successive years summer calving rates were 2 8 times larger than annual average rates the average ratio of the calving flux due to terminus volume change to that due to ice flow through the glacier terminus was 0 81 for the annual rates and 1 71 for summer rates the estimated mean annual calving rate from agassiz ice cap in the period 1999 2002 was 0 67 0 15 km 3 a 1 o f which 54 emanated from eugenie glacier alone this total rate is similar to a previously estimated calving rate from devon ice cap

numerical modeling of the development of u shaped valleys by glacial erosion the steep sided valleys and overdeepened basins of alpine landscapes are well known products of glaciation yet relatively little is known about how the dynamics of ice flow and glacial erosion interact to give rise to such landforms by linking a finite element model for ice flow through a glacier cross section with an erosion model it is possible to investigate the development of one of the most striking glacial landforms the u shaped valley in addition to providing a detailed understanding of landform development such modeling provides a way to test current understanding of the controls on glacial sliding and erosion to simulate valley development i first model flow through an initial glacier cross section and calculate the glaciological parameters that govern erosion i then numerically simulate erosion to produce a modified transverse profile for which a new flow field and erosion pattern are computed a number of iterations permits examination of the progressive transformation of cross section form which can be compared with field data model predictions of the cross section flow field are in close accord with data from the athabasca glacier and include marked lateral variations in sliding velocity with an erosion law dependent on basal velocity the model predicts the rapid transformation of a v shaped cross section into a recognizably glacial form over a time period on the order of 10 4 yr and the eventual development of a steady state quasi parabolic glacier cross section better agreement with empirical data from glaciated valleys is obtained by including temporal variations in ice discharge in order to mimic the characteristics of 100 000 yr glacial cycles the high discharge phase dominates form development and at low discharges cross section form is essentially inherited from the central part of the form that developed during the preceding high discharge phase