thermochronological investigation of fault zones abstract the timing of faulting episodes can be constrained by radiometric dating of fault zone rocks fault zone material suitable for dating is produced by tectonic processes such as 1 fragmentation of host rocks followed by grain size reduction and recrystallization to form mica and clay minerals 2 secondary heating melting of host rocks by frictional fault motions and 3 mineral vein formation as a result of fluid advection associated with the fault motions the thermal regime of fault zones consists primarily of the following three factors a regional geothermal structure across the fault zone and background thermal history of studied province bounded by fault systems b frictional heating of wall rocks by fault motions and c heating of host rocks by hot fluid advection in and around the fault zone thermochronological methods widely applied in fault zones are k ar 40ar 39ar fission track and u th methods for which methodological principles as well as analytical procedures are briefly described the thermal sensitivities of individual thermochronological systems are then reviewed which critically control the response of each method against the thermal processes based on the knowledge above representative examples as well as key issues are highlighted to date fault gouges pseudotachylytes mylonites and carbonate veins placing new constraints upon geological geomorphological and seismological frames finally the nojima fault is presented as an example for multiple applications of thermochronological methods in a complex fault zone

impacts of recent paraglacial dynamics on plant colonization a case study on midtre lovenbreen foreland spitsbergen 79 n climatic changes since the end of the little ice age have considerably disturbed environmental balances of plant colonization in high latitudes within one century on spitsbergen valley glaciers have retreated up to one kilometre from their original terminus as of 1918 affecting several hundred hectares of two types of landscape processes plant colonization and paraglacial morphogenesis since these processes are limited to the chronological position of the old ice front it is possible to know the rate of plant colonization by both qualitative and quantitative means as well as speculate on the processes involved such as the effects of runoff the present study is limited to the midtre lovenbreen forefield latitude 79 n longitude 12 e where geomorphologic and floristic samples were collected in 2003 on stable deposits in this area the settlement and the evolution of floristic groups have been documented during this time period of colonization the plain areas are reworked by runoff at a kilometric scale and are characterized as similar to their surrounding biogeographic landscapes thus a relationship can be observed between the paraglacial process occurring in the proglacial forelands and surrounding stable surfaces on till deposits these features that occur as spatial discontinuities across the landscape are perceptible through either plant colonization or disturbance to vegetation caused by hydrological processes ultimately however runoff dynamics maintain pioneer vegetation groups which are superimposed on plant colonization that are driven by temporal periods of deglaciation differences in the rates and the nature of plant colonization are biomarkers of paraglacial dynamics

lateglacial and holocene talus slope development and rockwall retreat on mynydd du uk modification of lateglacial and holocene talus sheets by debris flows and gully incision on mynydd du wales has resulted in a convergence of upper slope form characterised by an upper rectilinear slope gradient of 36 3 and a range of concavities of c 0 1 0 2 in most cases gully incision and accumulation of debris cones have led to an increase in slope concavity evidence for talus erosion reworking and redeposition on the upper slope emphasises secondary reworking processes as well as primary talus accumulation on the upper slope and permits construction of a model of talus development at mynydd du on the basis of talus volume calculation of the first rockwall retreat data set for southern britain suggests that c 7 1 m 84 of overall rockwall retreat 8 5 m took place during the lateglacial and only c 1 4 m 16 occurred during the holocene these figures imply that lateglacial retreat rates ranged from 1 01 to 2 44 m ka 1 with an overall mean rate of 1 23 m ka 1 in contrast holocene rockwall retreat rates range from 0 10 to 0 17 m ka 1 with a mean rate of 0 12 m ka 1 approximately 27 of cliff retreat is attributed to microgelivation while similar to holocene and present day alpine environments these lateglacial retreat rates are one order of magnitude higher than most equivalent values for arctic sites this reflects both alpine style diurnal freeze thaw activity on mynydd du during the younger dryas and paraglacial rock mass instability following deglaciation assuming an exponential decline in rockwall sediment release it is estimated that approximately half the talus had accumulated within c 1 ka of deglaciation at one site paraglacial talus accumulation appears to have contributed significantly to the glacial sediment transport system of a subsequent ice advance present day rates of rockwall retreat and talus accumulation by rockfall are estimated to be 0 014 and 0 022 mm yr 1 m ka 1 respectively similar to values for other british sites and markedly lower than holocene rates of cliff recession due to microgelivation by implication the geomorphic significance of microgelivation may have been greatly underestimated in studies of inland rock slope evolution in temperate mid latitude environments

water driven processes and landforms evolution rates in mountain geomorphosites examples from swiss alps abstract geomorphic processes driven by water are particularly active in mountain environments especially under the current climate conditions erosion and dissolution processes shape meaningful landforms in different kinds of deposits and rocks and in some cases they are classified as geomorphosites such landforms especially earth pyramids and rock pillars are usually characterized by a high scientific value e g representativeness ecologic support role and by additional values e g cultural and aesthetic value contributing to the local geoheritage mountain geomorphosites are growing in importance within scientific community and their morphological evolution can affect the global value of the site itself e g integrity in this paper after a first review on the terminology used for classifying landforms modelled by water runoff and on their meaning within the mountain environment the results of a detailed research performed at two sample sites included in the swiss national inventory of geosites are presented the two study sites are representative respectively of i water runoff on glacial deposits shaping earth pyramids pyramides d euseigne ii water dissolution on gypsum rocks modelling articulate karst landscapes pyramides de gypse du col de la croix for each site landforms evolution was investigated and denudation rates were estimated by means of different methods iconographic material analysis quantitative geomorphology and dendrogeomorphology on exposed roots despite the long term average rates obtained by means of roots exposure for both water runoff on glacial deposits e g 5 8 mm y and dissolution on gypsum rocks 5 6 mm y are comparable moreover a strict relation between the activity degree of processes the integrity of the site and the assignment of geomorphosites to a specific category i e active passive or evolving passive emerged from the results

paleomagnetic and magnetic fabric data from lower triassic redbeds of the central western carpathians new constraints on the paleogeographic and tectonic evolution of the carpathian region in the central western carpathians cwc most published paleomagnetic results from permo mesozoic rocks document extensive remagnetizations and come from thin skinned thrust units that have undergone multistage deformation we present results from lower triassic redbeds from the autochthonous cover overlying the basement that carry a primary magnetization petromagnetic results indicate that the dominant ferromagnetic carrier is hematite while magnetic susceptibility and its anisotropy are controlled by both ferromagnetic and paramagnetic minerals magnetic fabrics document weak deformation related to late cretaceous shortening the directions of the high unblocking temperature remanence components pass both reversal and fold tests attesting to their primary nature paleomagnetic inclinations are flatter than expected from reference datasets suggesting small latitudinal separation between the cwc and stable europe paleomagnetic declinations are mostly clustered within individual mountain massifs implying their tectonic coherence they show only minor differences between the massifs indicating a lack of significant vertical axis tectonic rotations within the studied central parts of the cwc the paleomagnetic declinations are therefore representative of the whole of the cwc in terms of regional paleogeographic interpretations and imply moderate counterclockwise rotations c 26 of the region with respect to stable europe since the early triassic

paraglacial adjustment of sediment slopes during and immediately after glacial debuttressing abstract daily time lapse imagery and pixel tracking was used to monitor and track spatial and temporal changes in sediment mantled hillslopes during and immediately after glacier retreat in the fox glacier te moeka o tuawe valley new zealand observations from 2014 to 2018 of the fox glacier and surrounding hillslopes show hillslope failure is primarily coincident with and triggered by glacier retreat with rainfall accelerating movement of the hillslope during glacier retreat failure of the hillslope primarily occurred through sediment sliding internal deformation of the sediment and occasional surficial debris falls flows and avalanches delivering approximately 9 2 m m3 of sediment directly to the underside of the glacier over the study period with a maximum daily averaged movement of 0 4 m per day of the main sediment mass following debuttressing hillslope failure became dominated by localised rainfall induced debris flows which initiated gullying of the sediment mantled slope ongoing instability of the slope and associated movement is maintained by toe erosion from the fox river and melting dead ice while continued rapid failure is facilitated through localised debris flows the tracking of temporal and spatial changes of sediment mantled hillslopes during glacier retreat has shown broad scale hillslope response to occur quickly within days of rainfall or accelerated glacier retreat particularly during summer debris flows commonly thought to be a dominant erosion process within paraglacial environments only occur following complete debuttressing and are supply limited only occurring after sediment sliding has occurred unlike many other case studies sediment connectivity immediately following glacier retreat is high due to a lack of storage space and high rainfall inducing mass movements efficiently delivering hillslope sediments to the proglacial stream channel attempts to quantify displaced volumes of sediment from paraglacial systems are likely underestimated due to a a lack of focus on the early and latter stages of debuttressing b a reliance on debris flows being a primary transport mechanism and c sediment being delivered sub glacially rather than supra glacially further enhancing connectivity

stratigraphic architecture and infill history of a deglaciated bedrock valley based on georadar seismic profiling and drilling the sediment fill of a silled bedrock valley in western norway has been investigated with respect to stratigraphy and infill history using a combination of mapping georadar seismic profiling and drilling a small outlet glacier occupies the head of the valley that displays a stepwise down valley profile and terminates in a lake at 29 m above sea level the valley is surrounded by high steep bedrock slopes and is characterized by a series of filled basins each limited by sills of bedrock or moraine accumulations till glacial outwash and or rockslide deposits fill in the lower half of the two larger basins fan delta deposits fringed by the deposits of alluvial fans and colluvial cones dominate the upper fill of most basins fan delta deposits interfinger downstream with lake sediments in the larger basins and fluvial deposits comprise the top fill the overall infill pattern was controlled by deglaciation as well as basin size and shape an overall decreasing sediment supply following deglaciation is shown in the fill of a larger basin down valley whereas a recently increasing sediment supply during glacier growth is reflected primarily in an upstream basin only the lowermost basin was exposed to a sea level drop from 75 m above sea level to the present lake level associated with incision and river migration this observation is in contrast to the basins above marine influence where incision has been limited due to fixed downstream sills resulting in insignificant erosion except for some fan head entrenchment it follows that the fills of these small valley basins display progradational and aggradational trends of deposition and paraglacial reworking has been limited additionally the study demonstrates that georadar profiling combined with other methods is very useful for comprehensive investigation of valley basins

re evaluating the age of the haughton impact event we have re evaluated the published age information for the haughton impact structure which was believed to have formed 23 ma ago during the miocene age and report new ar ar laser probe data from shocked basement clasts this reveals an eocene age which is at odds with the published miocene stratigraphic apatite fission track and ar ar data we discuss our new data within this context we have found that the age of the haughton impact structure is 39 ma which has implications for both crater recolonization models and post impact hydrothermal activity future work on the relationship between flora and fauna within the crater and others at high latitude may resolve this paradox

quantitative particle size microtextural and outline shape analyses of glacigenic sediment reworked by paraglacial debris flows particle size analysis and scanning electron microscopy have been used with some success to differentiate sediments sampled from varying geomorphological environments in the paraglacial environment however discrimination of paraglacially reworked deposits from in situ glacigenic deposits has proven to be problematic we consider till sediments that have been reworked by paraglacial debris flows and in situ unreworked parent material and apply a series of quantitative techniques in an attempt to discriminate samples from each environment initial analysis of particle size suggests some eluviation of fines from the debris flow reworked deposits but is of insufficient significance to allow reliable differentiation of geomorphological environment similarly although slight differences are identified in terms of quartz grain surface microtextures and quartz grain outline shape subsequent pca cluster and fourier analyses fail to reliably differentiate quartz grains from each geomorphological environment owing to high levels of intra sample heterogeneity this lack of apparent difference may arise from a lack of paraglacial process operation of significant magnitude or duration for a characteristic process imprint to emerge at this scale of observation accordingly further assessment of particle size and microtextural characteristics of glacial and paraglacial sediments may be most fruitful where sediments have been reworked over long distances moreover differentiating glacial from paraglacial deposits is likely to yield the most reliable results where rigorous statistical analyses are combined with a wide range of sedimentological and geomorphological techniques copyright 2008 john wiley and sons ltd

paraglacial gullying of sediment mantled slopes a case study of colletthogda kongsfjorden area west spitsbergen svalbard this paper evaluates the paraglacial evolution of a sediment mantled slope in a polar maritime environment the intensity of paraglacial processes is estimated through quantifi cation of erosion and dating of fi eld sectors with the help of photographic archives gully erosion has been estimated using morphometric parameters and by surveys of vegetation cover the rapid melting of dead ice cores controls gully formation this leads to slope form modifi cation gully profi le gradients are reduced from a mean of 35 to a mean ranging between 10 and 15 profi le evolution results from the collapse of glacier lateral moraine all data mean slope angle of individual gullies frequency distribution of slope angles fractional distance to the apex gullying index volume of debris mobilized vertical erosion rate tend to increase with increasing deglaciation age and the duration of paraglacial activity vegetation colonization is a response to stabilization of the ground surface and the drying up of the ground surface due to dead ice melting the full sequence of paraglacial slope adjustment gully incision stabilization may occur rapidly at the study site i e within two decades finally a lateral morphogenic sequence is proposed showing the importance of paraglacial processes at the onset of the deglaciation

the evidence for paraglacial sedimentation and its temporal scale in the deglacierizing basin of small river glacier canada abstract spatially sampled suspended sediment data from extra channel surfaces of different ages during rainfall events were used to infer the timescale of landscape adjustment to little ice age lia deglacierization at small river glacier canada surface ages were determined by aerial photograph interpretation turbidimeters were installed in three ephemeral channels on young mature and old surfaces and their response to rainfall events of different magnitudes recorded results showed young ice proximal surfaces exposed since 1977 were increasingly vulnerable to mobilization during rainfall events a suspended sediment response from old surfaces exposed since 1910 was recorded for only three events with 5 and 30 year return periods the intensity and duration of rainfall events therefore had to increase in magnitude to mobilize sediment on surfaces of increasing maturity hysteresis in the channel suspended sediment response further confirmed the dependence of surface response on rainfall event magnitude the rapid temporal decline in surface response indicated that surface armoring or sediment exhaustion is stabilizing surfaces within decades of exposure from the lia maximum ca 1910 at small river glacier however further perturbation for example by glacial advance or extreme climatic events would likely modify the pattern of suspended sediment yields by changing terrain surface mobilization thresholds and reconfiguring channel sediment stores we therefore suggest that it is difficult to determine when paraglacial sedimentation ceases to influence suspended sediment yields and therefore significantly limiting the usefulness of the term to describe the period of suspended sediment yield adjustment following deglacierization

inversion of combined gravity and bathymetry data for crustal structure a prescription for downward continuation abstract we propose a new and improved recipe for inverting for crustal thickness variations from combined gravity and bathymetry data the new ingredients with respect to previous studies are the posing of this problem as an inverse problem and the use of a downward continuation filter which can be tailored to find the crustal thickness solution which satisfies a minimum slope or maximal smoothness criteria or a weighted combination of these desired solution features we explore several suggestions for determining the optimum smoothing parameters for a given crustal thickness inversion then we compare this new method to that used previously in marine gravity studies we find it to be an improved recipe for dealing with gravity data with observation errors of 3 5 mgal but not by much this recipe will be most useful in extracting more geological information from marine gravity data where apparent observation errors are 1 mgal e g from future global positioning satellite navigated studies

quantifying sediment storage in a high alpine valley turtmanntal switzerland the determination of sediment storage is a critical parameter in sediment budget analyses but in many sediment budget studies the quantification of magnitude and time scale of sediment storage is still the weakest part and often relies on crude estimations only especially in large drainage basins 100 km2 we present a new approach to storage quantification in a meso scale alpine catchment of the swiss alps turtmann valley 110 km2 the quantification of depositional volumes was performed by combining geophysical surveys and geographic information system gis modelling techniques mean thickness values of each landform type calculated from these data was used to estimate the sediment volume in the hanging valleys and the trough slopes sediment volume of the remaining subsystems was determined by modelling an assumed parabolic bedrock surface using digital elevation model dem data a total sediment volume of 781 3 106 1005 7 106 m3 is deposited in the turtmann valley over 60 of this volume is stored in the 13 hanging valleys moraine landforms contain over 60 of the deposits in the hanging valleys followed by sediment stored on slopes 20 and rock glaciers 15 for the first time a detailed quantification of different storage types was achieved in a catchment of this size sediment volumes have been used to calculate mean denudation rates for the different processes ranging from 0 1 to 2 6 mm a based on a time span of 10 ka as the quantification approach includes a number of assumptions and various sources of error the values given represent the order of magnitude of sediment storage that has to be expected in a catchment of this size copyright 2009 john wiley sons ltd

multiple low temperature thermochronology constraints on exhumation of the tatra mountains new implication for the complex evolution of the western carpathians in the cenozoic the tectonothermal evolution of the highest mountain range in the carpathian arc the tatra mountains is investigated by zircon and apatite fission track and zircon u th he zhe dating methods in order to unravel the disputed exhumation and geodynamic processes in the western carpathians our data in combination with geological evidences reveal a complex cenozoic history with four major tectonothermal events i a very low grade metamorphism of the crystalline basement at temperatures 240 c due to tectonic burial during the eo alpine collision in the late cretaceous 80 ma ii exhumation and cooling of the basement to temperatures 150 c after burial to 5 9 km depths by the paleogene fore arc basin iv final exhumation of the segmented basement blocks during oligocene miocene 32 11 ma owing to lateral extrusion of the north pannonian plate and its collision with the european foreland the spatial pattern of thermochronological data suggests asymmetric exhumation of the tatra mountains beginning in the northwest at 30 20 ma with low cooling rates 1 5 c ma and propagating toward the major fault bounding the range in the south where the youngest cooling ages 16 9 ma and fastest cooling rates 10 20 c ma are found our data prove that the tatra mountains shared cenozoic evolution of other crystalline core mountains in the western carpathians however the miocene zhe ages suggest that the tatra mountains were buried to the greatest depths in the paleogene early miocene and experienced the greatest amount of miocene exhumation

changes in sediment connectivity following glacial debuttressing in an alpine valley system abstract increasing air temperature and declining winter snowfalls are resulting in rapid glacier recession and the expansion of proglacial margins in alpine regions such margins include substantial debris accumulations e g frontal lateral moraine ridges till covered and steep valley sidewalls which may be unstable due to glacial debuttressing rainfall snowmelt and ice melt out may then cause mass movements here we quantify the decadal scale erosion and deposition patterns and changes in connectivity for two valley sidewall geomorphological systems following retreat of the glacier d otemma switzerland we apply archival digital photogrammetric methods to the period 1964 to 2009 to determine high resolution digital elevation models these were differenced to calculate patterns of erosion and deposition and to quantify the evolution of sediment connectivity we found that gully headward erosion rates between ca 10 6 mm year and 1002 1 mm year was the main geomorphological process during glacier thinning but increasing depositional rates downslope of the gullies ca 21 3 to 298 5 mm year were recorded in the following years associated with significant alluvial fan growth at the slope base while gullying enhanced connectivity by removing glacially conditioned sediment transfer buffers so connecting side slopes to upstream sediment sinks the upslope contributing area between 1964 and 2009 increased by 73 8 and 195 1 in each subsystem alluvial fans reduced the rates of sediment transfer to the rapidly enlarging glacial forefields the detail of these responses is conditioned by three generic processes 1 the wider geomorphic setting here the presence of a moraine bastion as a primary part of the sediment cascade strongly influenced gully morphology evolution and the likely length of the paraglacial period length 2 the thickness of sediment left by the retreating glacier which controlled the influence of bedrock topographic buffers on connectivity and 3 the extent to which diffusive drainage systems develop in response to the deposition at the hillslope base which tend to disconnect sediment flux post glacially gully development has a self limiting effect on sediment connectivity in that while gullying increases sediment connectivity the eroded sediment leads to deposition on the alluvial plain that reduces sediment connectivity

the constitution and structure of the lunar interior the current state of understanding of the lunar interior is the sum of nearly four decades of work and a range of exploration programs spanning that same time period missions of the 1960s including the rangers surveyors and lunar orbiters as well as earth based telescopic studies laid the groundwork for the apollo program and provided a basic understanding of the surface its stratigraphy and chronology through a combination of remote sensing surface exploration and sample return the apollo missions provided a general picture of the lunar interior and spawned the concept of the lunar magma ocean in particular the discovery of anorthite clasts in the returned samples led to the view that a large portion of the moon was initially molten and that crystallization of this magma ocean gave rise to mafic cumulates that make up the mantle and plagioclase flotation cumulates that make up the crust smith et al 1970 wood et al 1970 this model is now generally accepted and is the framework that unifies our knowledge of the structure and composition of the moon the intention of this chapter is to review the major advances that have been made over the past decade regarding the constitution of the moon s interior much of this new knowledge is a direct result of data acquired from the successful clementine and lunar prospector missions as well as the analysis of new lunar meteorites as will be seen results from these studies have led to many fundamental amendments to the magma ocean model much of what we know from sample analyses has been previously summarized elsewhere and only their most important aspects will be discussed in this chapter the reader is referred to the relevant chapters in the books basaltic volcanism on the terrestrial planets basaltic volcanism study project 1981 the

paraglacial response of steep sediment mantled slopes to post little ice age glacier recession in the central swiss alps this research assesses the morphological consequences of recent post little ice age paraglacial reworking of valley side sediment mantles in the european alps it aims to identify the extent and conditioning factors of slope adjustment at sites in the swiss alps model the temporal pattern and assess the rates of sediment reworking involved gully systems have cut into steep high level lateral moraines and debris cones have accumulated downslope debris flow is the dominant agent of sediment transfer factors controlling the extent of this activity include moraine slope gradient relief and moisture availability gullies appear to have reached their maximum dimensions within ca 50 yr of deglaciation after which gully relief is reduced by removal of inter gully slopes and gully infilling within 80 140 yr on the most recently deglaciated terrain minimum erosion rates average ca 95 mm yr 1 since gully initiation greatly exceeding normal erosion rates in other environments mean annual accumulation of a single debris cone since ice retreat was calculated to be ca 30 mm yr 1 implications of these findings are applied to patterns of paraglacial sediment mantled slope adjustment conceptualising paraglacial landscape response in terms of a sediment release exhaustion model and paraglacial landform succession copyright 2005 john wiley sons ltd

kreep cumulates in the western lunar highlands ion and electron microprobe study of alkali suite anorthosites and norites from apollo 12 and 14 alkali suite anorthosites and norites are the second most common plutonic rock association in the western lunar highlands after the magnesian suite but their origin poses an enigma for most petrologic models of lunar crustal evolution some models suggest that the alkali and magnesian suites formed from distinct unrelated parental magmas whereas other models propose that both suites formed from the same parental magma the contrast in major element chemistry of the cumulus phases in each suite is difficult to reconcile with their similar incompatible element chemistry we present herein a detailed ion microprobe sims and electron microprobe study of seven alkali suite rocks our data show that most alkali suite anorthosites preserve major and trace element characteristics acquired during their formation as igneous cumulate rocks and that these characteristics can be used to reconstruct the parental magma composition the data indicate that cumulates of the alkali suite crystallized from magmas with rare earth element ree contents approximately 0 6 2 0xhigh k kreep and small but consistently positive eu anomalies eu eu super approximately 2 relative to kreep snyder and others 1995a have proposed that the alkali suite parental magma is similar to apollo 15 pristine kreep basalt our model suggests that the major element composition of cumulus plagioclase in most alkali suite rocks is too sodic for the calculated crystal line of descent of pristine kreep basalt and that assimilation of pre existing calcic anorthosite is required this conclusion is supported by the ree patterns of the alkali suite parental magma determined here we propose that alkali suite anorthosites formed as flotation cumulates in kreepy plutons that may have formed norites as complementary bottom cumulates the alkali flotation cumulates reflect fractional crystallization of their parental pluton local equilibrium crystallization assimilation of plagioclase rich roof rock and episodic magma mixing during convective overturn of the crystallizing magma bodies texturally pristine alkali anorthosites exhibit petrographic characteristics that are consistent with their origin as cumulates in a kreepy pluton including abundant modal plagioclase post cumulus pyroxenes both augite and pigeonite that generally lack exsolution lamellae and that have equilibration temperatures of 950 1100 degrees c relict igneous textures and in some cases igneous lamination the lack of cumulus mafic phases in rocks that should be pyroxene saturated suggests separation of the plagioclase by flotation not sinking assimilation of plagioclase from older anorthositic highlands crust is indicated by the high eu contents of the cumulates and by the positive eu anomalies in their calculated parental melts relative to high k kreep mixing of the evolved alkali suite parental magma with primitive melt occurred episodically as shown by reverse zoning profiles in some cumulus plagioclase injection of this primitive hot magma into the crystallizing pluton may have induced convective overturn of the magma chamber

the isotopic record of lunar volcanism abstract the timing and extent of lunar volcanism was determined primarily by the internal thermal evolution of the moon a late heavy bombardment produced most of the observable lunar basins easily recognized stratigraphic markers and also may have influenced lunar volcanism most of the nearside basins seem to have been produced 3 8 4 0 ga ago during a period often referred to as the lunar cataclysm the pre cataclysm period was characterized by formation of the lunar crust plutonic rocks within the crust and pre mare volcanism isotopic analysis of breccia clasts pre dating the cataclysm has yielded an outline of this period the isotopic record of post cataclysm mare volcanism is clear but incomplete because samples from the youngest mare areas are lacking specifically the isotopic data show that some lunar anorthosites formed 4 45 ga ago consistent with early formation of an anorthositic lunar crust some mg suite norites troctolites and dunites also formed approximately contemporaneously with the oldest anorthosites but others are up to 200 300 ma younger more evolved rocks granites and quartz monzodiorites also formed between 4 4 and 4 0 ga ago the earliest known pre mare volcanism at 4 25 ga ago included aluminous mare like basalts and an olivine gabbronorite similar to apollo 12 basalts kreep basalt volcanism began at least 4 1 ga ago approximately contemporaneously with that of the ancient mare like basalts and continued during the cataclysm recorded instances of high ti mare basalt volcanism began during or immediately after the cataclysm low ti mare basalt volcanism is the most recent for which samples are available the isotopic data record an early primary lunar differentiation during which mare basalt sources formed probably by crystallization of cumulus minerals from a lunar magma ocean the isotopic record of post cataclysm basalts indicates a heterogeneous lunar mantle and can be explained by partial melting of cumulate sources but more complex petrogenesis also has been suggested more complex petrogenetic processes including assimilation and assimilation fractional crystallization afc seem to be required for pre mare volcanics the isotopic data contain a hint that petrogenesis of the oldest pre mare volcanics may be linked to formation of the so called procellarum basin possibly the oldest and largest lunar basin such a basin would provide a geologic context for the pre mare volcanics and its formation may have been a defining moment in lunar history

evolution of high arctic glacial landforms during deglaciation abstract glacial landsystems in the high arctic have been reported to undergo geomorphological transformation during deglaciation this research evaluates moraine evolution over a decadal timescale at midtre lovenbreen svalbard this work is of interest because glacial landforms developed in svalbard have been used as an analogue for landforms developed during pleistocene mid latitude glaciation ground penetrating radar was used to investigate the subsurface characteristics of moraines to determine surface change a lidar topographic data set obtained 2003 and a uav derived obtained 2014 digital surface model processed using structure from motion sfm are also compared evaluation of these data sets together enables subsurface character and landform response to climatic amelioration to be linked ground penetrating radar evidence shows that the moraine substrate at midtre lovenbreen includes ice rich radar velocities of 0 17 m ns 1 and debris rich radar velocities of 0 1 0 13 m ns 1 zones the ice rich zones are demonstrated to exhibit relatively high rates of surface change mean thresholded rate of 4 39 m over the 11 year observation period however the debris rich zones show a relatively low rate of surface change mean thresholded rate of 0 98 m over the 11 year observation period and the morphology of the debris rich landforms appear stable over the observation period a complex response of proglacial landforms to climatic warming is shown to occur within and between glacier forelands as indicated by spatially variable surface lowering rates landform response is controlled by the ice debris balance of the moraine substrate along with the topographic context such as the influence of meltwater site specific characteristics such as surface debris thickness and glaciofluvial drainage are therefore argued to be a highly important control on surface evolution in ice cored terrain resulting in a diverse response of high arctic glacial landsystems to climatic amelioration these results highlight that care is needed when assessing the long term preservation potential of contemporary landforms at high arctic glaciers a better understanding of ice cored terrain facilitates the development of appropriate age and climatic interpretations that can be obtained from palaeo ice marginal landsystems

exhumation history of the tatry mountains western carpathians constrained by low temperature thermochronology this study tests alternative models for the growth of the tatry mountains central western carpathians by the application of low temperature thermochronology zircon u th he ages from the north of the range are mostly between 48 to 37 ma and indicate cooling prior to the onset of forearc sedimentation in the region 42 39 ma in contrast zircon u th he ages in the south of the range are around 22 ma apatite fission track ages across the sampled sites range from 20 to 15 ma apatite u th he ages range from 18 to 14 ma with little variation with elevation or horizontal location based on thermal modelling and tectonic reconstructions these miocene ages are interpreted as cooling in the hanging wall of a northward dipping thrust ramp in the current location of the sub tatric fault with cooling rates of 20 c myr at 22 14 ma modeled cooling histories require an abrupt deceleration in cooling after 14 ma to 5 c myr this is associated with termination of deformation in the outer carpathians and is synchronous with the transition of the pannonian basin from a syn rift to a post rift stage and with termination of n s compression in the northern part of the central western carpathians overall the timing of shortening and exhumation is synchronous with the formation of the outer carpathian orogen and so the miocene exhumation of the tatry record retro vergent thrusting at the northern margin of the alcapa microplate

the titanium contents of lunar mare basalts lunar mare basalt sample data suggest that there is a bimodal distribution of tio2 concentrations using a refined technique for remote determination of tio2 we find that the maria actually vary continuously from low to high values the reason for the discrepancy is that the nine lunar sample return missions were not situated near intermediate basalt regions moreover maria with 2 4 wt tio2 are most abundant and abundance decreases with increasing tio2 maria surfaces with tio2 5 wt constitute only 20 of the maria although impact mixing of basalts with differing ti concentrations may smear out the distribution and decrease the abundance of high ti basalts the distribution of basalt ti contents probably reflects both the relative abundances of ilmenite free and ilmenite bearing mantle sources this distribution is consistent with models of the formation of mare source regions as cumulates from the lunar magma ocean

paraglacial redistribution of glacial sediments in the vestfold hills east antarctica abstract the vestfold hills landscape is dominated by bare rock slopes and unconsolidated deposits form a minor component of the surficial geology the principal objectives of the study were to explain the distribution of unconsolidated deposits determine the nature and timing of sedimentary processes during and after deglaciation and the impact of these processes on landscape development observations of late quaternary glaciation and deglaciation of the area and contemporary depositional processes are reported and a conceptual model of geomorphological change since deglaciation is presented the model attempts to reconcile the types and rates of contemporary depositional processes with the distribution of deposits and landforms and to explain why unconsolidated deposits cover less than 20 of the hills despite the effects of recent glaciation the lack of unconsolidated deposit in the landscape can be attributed to the combined effects of low debris volumes in the ice and the redistribution of debris during and after deglaciation redistribution of debris can be explained by paraglacial processes which are non glacial sedimentary processes that are directly conditioned by glaciation paraglacial sedimentation is a response to rapid adjustment of the debris system after the dominance of glacial conditions and is characterized by disequilibrium between sediment supply and transportation of sediment by nonglacial processes evidence from the vestfold hills suggests paraglacial sedimentary processes are dominated by mass movement of glacial debris from slopes and the formation of stable valley fills and that the main sediment transfers occur within a few thousand years of deglaciation

landforms and landscape evolution in the skardu shigar and braldu valleys central karakoram abstract the central karakoram which includes k2 in pakistan is one of the most rapidly rising areas on earth and exhibits complex topography and extreme relief impressive valley fills and glacial landforms are present throughout the valleys the dynamics of landscape evolution of the region are currently not well understood consequently the landforms were mapped and assessed in the skardu shigar and braldu valleys to elucidate the spatio temporal scale dependencies of surface processes active in the region these valleys were examined using geomorphic field methods remote sensing geomorphometry and terrestrial cosmogenic nuclides tcns surface exposure dating the glaciers in this region have oscillated considerably throughout the late quaternary and four glacial stages have been recognized including at least six glacial advances surface processes readjusted after glacier retreat and ubiquitous mass movements and catastrophic landsliding transported material from steep slopes to valley bottoms while glaciofluvial meltwater and glacier outburst floods redistributed sediment down valley glacier geochronology and late holocene ages of the outburst flood deposits indicate that landscape evolution has been dominated by glaciation and paraglaciation during the late quaternary

building and exhumation of the western carpathians new constraints from sequentially restored balanced cross sections integrated with low temperature thermochronometry western carpathian orogeny has been the subject of intense scientific debate due to the occurrence of enigmatic features leading several authors to provide contrasting geological models in this paper a new interpretation for the tectonic evolution of the western carpathians is provided based on i an analysis of the stratigraphy of the mesozoic tertiary successions across the thrust belt domains ii a reappraisal of the stratigraphy and sedimentology of the tectonic melange i e the so called pieniny klippen belt marking the suture between the inner and outer carpathians and iii the construction of a series of balanced and restored cross sections validated by 2d forward modeling our analysis provides a robust correlation of the stratigraphy from the outer to the inner carpathians independently of the occurrence of oceanic lithosphere in the area and allows for the reinterpretation of the tectonic relationships among the inner carpathians the outer carpathians and the pieniny klippen belt and the exhumation mechanisms affecting this orogenic belt in order to constrain the evolution during the last 20 ma our model also integrates previously published and new apatite fission track and apatite u th sm he data these latter indicate a middle late miocene exhumation of the pieniny klippen belt in this study the recent regional uplift of the pieniny klippen belt is described for the first time using a 2d kinematic model for the tectonic evolution of the western carpathians

glacier dynamics during a phase of late quaternary warming in patagonia reconstructed from sediment landform associations abstract the geomorphological record in glaciated landscapes can provide important information for the study of the response of glaciers to rapid climate change this study presents a new reconstruction of the glacial history of the northern monte san lorenzo ice cap southern south america during a period of accelerated warming and deglaciation following the antarctic cold reversal 14 5 12 8 ka we present a detailed geomorphological map of the valleys to the north of monte san lorenzo sediment landform assemblages identified include lateral and terminal moraine ridges flutes deltas ice contact fans palaeoshorelines kame terraces and outwash plains we map 14 primary ice limits 7 of which are newly identified and 7 of which are from previous studies mapped here in greater detail we devise landsystem models to formalise and document spatial and temporal changes in glacial processes and environments our new geomorphological mapping and landsystem reconstructions provide an important insight into the response of temperate patagonian glaciers to rapidly warming climate

heterogeneous extrusion and exhumation of deep crustal variscan assembly geochronology of the western tatra mountains northern slovakia abstract the nature and style of mid crustal assembly and exhumation during continental collision has been investigated in the tatra mountains of the western carpathians the pre alpine basement of the western carpathians represents the easternmost exposure of the variscan orogen in europe which marks the collision of laurasia with gondwanian affiliated terranes during the palaeozoic the tatric crystalline unit of the western tatra in northern slovakia displays an inverted metamorphic sequence where a high grade unit comprising migmatites with relicts of eclogite has been thrust over a lower grade mica schist unit new geochronological and thermochronological data together with published thermobarometry illuminate the metamorphic history of the western tatra the upper unit eclogites with occasionally preserved omphacite record near isothermal decompression from 1 6 gpa to 1 0 1 2 gpa at 750 800 c which lead to intensive re equilibration at high pressure granulite facies conditions comparable to the peak metamorphic conditions of the host migmatite both eclogite and migmatite shared a retrograde p t path following the insertion of the eclogite assemblage into the migmatites the metamorphic evolution of the lower unit mica schist is constrained to peak p t conditions of 0 6 0 8 gpa and 640 and 660 c followed by retrogression this suggests that different rock types of the western tatra metamorphic core shared only their exhumation path from mid crustal levels id tims sm nd dating of garnet from eclogite yields a whole rock garnet isochron age of 337 10 ma with an initial e nd isotopic composition of 8 3 in situ u pb dating of monazite from a migmatite surrounding the eclogite shows one age population of c 380 ma whereas monazite from a migmatite away from the eclogite preserves a robust 340 11 ma age which is indistinguishable from sm nd garnet age and u pb age of zircons in the anatectic leucosome of the migmatite 347 7 ma a younger monazite age population from the migmatite of 300 16 ma is consistent with 40 ar 39 ar mica ages of c 310 ma this argues for a contemporaneous and likely shared exhumation path of the assemblage pair in situ monazite total pb analyses from the lower unit mica schists yields xenocrystic and c 370 ma ages but no geochronologic evidence for peak variscan tectonism exhumation of the deep crustal root occurred most probably in a two stage process the timing of the high pressure eclogite facies metamorphism before the onset of exhumation into the mid crust was likely between c 380 ma and 360 ma subsequent exhumation into the middle crust was coeval with migmatite generation at c 340 ma and garnet diffusion modeling suggest 30 c ma cooling rates the exhumation was likely tectonically forced by the action of a rigid indentor which prompted the weak lower crust to be heterogeneously extruded to mid crustal levels at a time coeval with anatexis and subsequently extruded with mid crustal material to the upper crust

dating fault reactivation by ar ar laserprobe an alternative view of apparently cogenetic mylonite pseudotachylite assemblages apparently cogenetic mylonite pseudotachylite assemblages are commonly reported in major fault zones they represent two very incompatible modes of deformation and complex formation mechanisms have been proposed to explain this paradox we report here one such assemblage from central norway in which apparently synchronous mylonite and pseudotachylite formation is separated by 100 ma mean muscovite ar ar laserprobe spot ages from mylonite and pseudotachylite matrix are 406 11 ma and 290 10 ma respectively in preference to a complex cogenetic model we invoke fault reactivation as a viable alternative and suggest that assumed contemporaneity in such assemblages may be invalid in many cases

geotechnical controls on a steep lateral moraine undergoing paraglacial slope adjustment original article can be found at http sp lyellcollection org copyright geological society

slow and fast deformation in the dora maira massif italian alps pseudotachylytes and inferences on exhumation history abstract the dora maira massif dm western alps is a type example of an ultra high pressure uhp metamorphic terrain the occurrence of pseudotachylytes within the val gilba area of dm led to speculation regarding the role of seismic slip in the exhumation of the massif in this study new field microstructural and geochemical data on the pseudotachylyte veins and their mylonitic gneiss host are presented the formation of pseudotachylyte veins occurred late in the exhumation history at 20 1 0 5 ma and at shallow depths

high spatial resolution 40ar 39ar dating of pseudotachylites geochronological evidence for multiple phases of faulting within basement gneisses of the outer hebrides uk abstract pseudotachylites within the neoarchaean to palaeoproterozoic basement of the lewisian gneiss complex have been analysed using the high spatial resolution 40 ar 39 ar uv laserprobe technique it has been possible to measure 40 ar 39 ar age and apparent9 age variations that would be beyond resolution by lower spatial resolution or bulk 40 ar 39 ar dating methods we report a range of complexities including significantly younger narrow 40 ar 39 ar ages for pseudotachylite forming events in lewis the c 1900 ma event may relate to early stages of laxfordian reworking in barra and south uist a 1300 1200 ma event is recorded whereas in barra south and north uist a second event is recorded at c 700 ma which is likely to be associated with nw and west directed thrusting and could represent far field effects of tectonic events recorded at this time east of the moine thrust in nw scotland supplementary material 40 ar 39 ar data are available at http www geolsoc org uk sup18372

orthopyroxene as a recorder of lunar crust evolution an ion microprobe investigation of mg suite norites the lunar mg suite which includes dunites troctolites and norites could make up 20 30 of the moon s crust down to a depth of 60 km the remainder is largely anorthositic this report focuses on norites because we have found that the chemical characteristics of orthopyroxene are effective recorders of their parental melt compositions many of the samples representing the mg suite are small and unrepresentative in addition they are cumulates and thus are difficult to study by whole rock techniques therefore we decided to study these rocks by sims techniques to analyze a suite of trace elements in orthopyroxene the 12 norite samples were selected from a recent compilation by warren who attempted to select the best candidate samples from the standpoint of their pristine character our present database includes greater than 300 superior electromagnetic pulse emp analyses and greater than 50 scanning ion mass spectroscopy sims analyses for 8 rare earth elements ree zr y and sr the mg s for the parental melts calculated from mg s in orthopyroxene show that most melts have mg s in the range of 0 36 0 60 this compares with a range of mg s for lunar volcanic picritic glass beads of 0 4 0 68 therefore although the cumulate whole rock compositions of the mg suite can be extremely magnesian the calculated parental melts are not anomalously high in mg a chemical characteristic of the mg suite norites that is more difficult to explain is the high kreep content of the calculated parental melts the ree contents for the calculated norite parental melts have ree that match or exceed the high k kreep component of warren therefore mixing of a kreep component and a picritic melt cannot by itself explain the high estimated ree contents of the melts parental to norites advanced crystallization following kreep incorporation especially of plagiclase may also be required

paraglacial debris cone formation on recently deglaciated terrain western norway five debris cones have formed on terrain deglaciated since ad 1750 75 in bergsetdalen western norway three were surveyed and studied in detail two accumulated over 108 215 years and the third over 57 108 years accumulation on all three appears to have effectively ceased around or slightly before ad 1965 through exhaustion of readily entrainable sediment in source areas upslope the volumes of the three cones range from c 9500 m3 to 403 600 m3 and imply average sediment accumulation rates of 8 44 mm yr 1 sediment erosion at one site was calculated to be 37 93 mm yr 1 averaged over the entire sediment source area paraglacial reworking of glacial drift by debris flows appears to have been the main agent of cone development at two sites but snow avalanches are thought to represent the main process of sediment transport at the largest cone these findings indicate that substantial debris cones may form and become inactive within 100 200 years of deglaciation implying that many late pleistocene parag

age and nature of paraglacial debris cones along the margins of the san rafael glacier chilean patagonia this study employs sedimentological indices and lichenometric dating on the lichen species plac opsis patagonica to investigate the nature and age of debris cones which have accumulated at the margins of the downwasting san rafael glacier in chilean patagonia these cones appear to have accumulated by the resedimentation of glacigenic deposits by debris flows with debris movement starting in the early 1980s cone activity follows a pattern of intense initial activity and sediment mobilisation followed by increased stability and colonization by vegetation three of the four cones had stabilized within 15 years of sediment movement initiation these features may be seen as being conditioned by glacial activity with second order controls provided by the local climate and sediment supply the cones have accumulated in a paraglacial environment

towards successful osl sampling strategies in glacial environments deciphering the influence of depositional processes on bleaching of modern glacial sediments from jostedalen southern norway the optically stimulated luminescence osl signals of quartz and k feldspar are known to bleach poorly within some glacial settings and can present a major challenge to dating applications however because the osl signal is extremely sensitive to sunlight exposure history the residual luminescence signals of modern glacial sediments also encode information about transport and depositional processes through examination of the residual luminescence properties equivalent dose de and overdispersion values of a suite of modern glacial sediments from different depositional settings sandar proglacial delta and main meltwater channel this study provides insights not only into which sediments are likely to be fully bleached within glacial settings but also into how osl can be used to trace different depositional processes across sedimentary landforms improved understanding of the processes of sediment bleaching will enable better sample selection and may improve the accuracy and precision of osl dating of glacial sediments the luminescence signals of both coarse grained quartz and k feldspar with similar sediment sources are found to be sensitive to both depositional process and specific depositional setting whereas modern braid bar head deposits from the nigardsdalen ice proximal proglacial delta typically have ages of 3 ka similar depositional features from the fabergstolsgrandane sandur have residual ages of 26 ka exploration of changing residual luminescence signals across individual sandur and proglacial delta braid bar features shows that braid bar head deposits can retain large residual d e values while the partner braid bar tail deposits are almost completely bleached the quartz osl signal and k feldspar irsl50 and post ir irsl250 signals are shown to bleach at the same rate across the same bar feature and the irsl50 k feldspar signal is also shown to be completely bleached for bar tail deposits in nigardsdalen therefore the irsl50 k feldspar signal is suitable for dating some glacial deposits circumventing the challenges associated with dim quartz signals 2014 the authors published by elsevier ltd this is an open access article under the cc by license

lunar multiring basins and the cratering process abstract numerous studies of the lunar gravity field have concluded that the lunar moho is substantially uplifted beneath the young multiring basins this uplift is presumably due to the excavation of large quantities of crustal material during the cratering process and subsequent rebound of the impact basin floor using a new dual layered crustal thickness model of the moon the excavation cavities of some nearside multiring basins grimaldi and larger and younger than tranquillitatis were reconstructed by restoring the uplifted moho to its preimpact location the farside south pole aitken spa basin was also considered due to its importance in deciphering lunar evolution restoring the moho to its preimpact position beneath these basins resulted in a roughly parabolic depression from which the depth and diameter of the excavation cavity could be determined using these reconstructed excavation cavities the basin forming process was investigated excavation cavity diameters were generally found to be on the small side of most previous estimates for orientale the modeled excavation cavity lies within the inner rook ring additionally with the exception of the three largest basins serenitatis imbrium and south pole aitken the depth diameter ratios of the excavation cavities were found to be 0 115 0 005 a value consistent with theoretical and experimental results for impact craters orders of magnitude smaller in size the three largest basins however appear to have significantly shallower depths of excavation compared to this trend it is possible that this may reflect a different physical process of crater formation e g nonproportional scaling special impact conditions or postimpact modification processes the crustal thickness model also shows that each basin is surrounded by an annulus of thickened crust we interpret this thickened crust as representing thick basin ejecta deposits and we show that the radial variation in the thickness of these deposits is consistent with scaling laws obtained from small scale experimental studies if multiring basins ever possessed a terraced main crater rim this terraced zone may be presently unrecognizable at the surface due to the emplacement of ejecta deposits that exceed a few kilometers in thickness exterior to the excavation cavity rim we also show that the interiors of many basins were superisostatic before mare volcanism commenced those basins that were closest to approaching a premare isostatic state lie close to or within an anomalous geochemical province rich in heat producing elements

age constraints on faulting and fault reactivation a multi chronological approach movement within the earth s upper crust is commonly accommodated by faults or shear zones ranging in scale from micro displacements to regional tectonic lineaments since faults are active on different time scales and can be repeatedly reactivated their displacement chronology is difficult to reconstruct this study represents a multi geochronological approach to unravel the evolution of an intracontinental fault zone locality along the danube fault central europe at the investigated fault locality ancient motion has produced a cataclastic deformation zone in which the cataclastic material was subjected to hydrothermal alteration and k feldspar was almost completely replaced by illite and other phyllosilicates five different geochronological techniques zircon pb evaporation k ar and rb sr illite apatite fission track and fluorite u th he have been applied to explore the temporal fault activity the upper time limit for initiation of faulting is constrained by the crystallization age of the primary rock type known as kristallgranit at 325 7 ma whereas the k ar and rb sr ages of two illite fractions 2 m 266 255 ma are interpreted to date fluid infiltration events during the final stage of the cataclastic deformation period during this time the kristallgranit was already at or near the earth s surface as indicated by the sedimentary record and thermal modelling results of apatite fission track data u th he thermochronology of two single fluorite grains from a fluorite quartz vein within the fault zone yield cretaceous ages that clearly postdate their late variscan mineralization age we propose that later reactivation of the fault caused loss of helium in the fluorites this assertion is supported by geological evidence i e offsets of jurassic and cretaceous sediments along the fault and apatite fission track thermal modelling results are consistent with the prevalence of elevated temperatures 50 80 c in the fault zone during the cretaceous

a general model of paraglacial landscape response a unifying attribute of all forms of paraglacial response is that deglaciation results in the exposure of unstable or metastable sediment sources that are subsequently tapped by a wide variety of processes over a wide range of timescales the paraglacial period in different geomorphological contexts is therefore con ditioned by two variables glacially conditioned sediment release and rate of sediment reworking under steady state conditions the latter may be approximated by an exhaustion model in which sediment yield is related to the amount of remaining available sediment by a negative exponential function this model offers an approximation for the behaviour of primary paraglacial systems in which glacigenic sediment sources are not replenished the long term behaviour of secondary primarily uvial paraglacial systems in which sediment inputs include both in situ and reworked glacigenic sediment appears intrinsically more complex but consistent with an exhaustion model if initial sediment avai

structural contraints of neotectonic activity in the eastern part of the western carpathians orogenic wedge abstract the eastern part of the western carpathians orogenic wedge covering the territory eastward from the 20 meridian could serve as an example for close relation between basement rock structural anisotropy and the neotectonic morphostructural pattern the neotectonic evolution of the region has been guided by crustal deformations of the entire main western carpathian fault systems defined by steeply dipping faults of ne sw nw se s n and e w directions the fault sets bound morphostructural units and form the base for the quaternary neotectonic activity and landscape development of the region closely linked to western carpathian lineaments they reflect both the moho topography and directional orientation of adjoining platform margins the fault sets represent inherited poly stage structures genetically correlating to cretaceous fold pattern of the western carpathians being repeatedly reactivated during cenozoic times summarising vertical movement ratios among neotectonic units particularly between the highest uplifted subsiding blocks we have found the maximal quaternary movements rate of the region reaching ca 1315 m and neotectonic movements rate of 1710 m

the age and depth of exhumed friction melts along the alpine fault new zealand laser ablation 40 ar 39 ar step heating analyses of 20 pseudotachylyte veins from a single location along the exhumed central portion of the active alpine fault of new zealand yield total gas age values between 1 and 19 ma evidence shows that they are genetically related and were formed during coeval episodes of seismogenic melting at shallow crustal depth contrasting with a spread in formation ages the total gas ages show an exponential decrease with increasing proportion of melt matrix and k content refl ecting incomplete degassing and mixtures of radiogenic ar sources calculation of intercepts for all melted matrix and all clast end member components indicate ca 570 ka quaternary friction melting ages of ca 332 ma lower carboniferous source rock assuming an average exhumation rate of 6 9 mm yr for uplift and erosion these results imply that friction melts were generated during major slip episodes at 3 5 5 km crustal depth we conclude that reliable dating of young pseudotachylyte can be accomplished by combining chronologic study with clast matrix quantifi cation of genetically related vein assemblages

a concise compilation of petrologic information on possibly pristine nonmare moon rocks ansrn q cr to facilitate systematic study of the surviving compositionally pristine endogenously igneous rocks of the ancient lunar crust a compilation has been generated of all likely samples along with key information on the petrologic characteristics and chemistry of each sample the compilation includes 260 samples besides information related to the likelihood of each sample being truly pristine i e mainly its texture and siderophile element abundances information is compiled on mineral content listing major phases present as well as basic information on mineral compositions on size expressed as mass and on whether a reasonably comprehensive chemical analysis has been published the compilation also classifies the samples into seven categories of confidence in the pristine composition of the samples reflecting an estimation of the relative likelihood that each arguably pristine sample is in fact pristine for many purposes it is crucial to avoid inclusion of polymict rocks in a data base on petrologic diagrams such as a plot of average mg mg 100 x molar mg mg fe in a low ca mafic silicate vs average an content in plagioclase rocks in the top three categories of the confidence in pristine character appear distinctly bimodal in composition with roughly half belonging to a ferroan suite characterized by high an despite relatively low mg when samples of low to moderate pristine character are included the bimodality appears less distinct sample mass can also be important with a data base restricted to samples more massive than i g there is a clear distinction in feldspar content and bulk density between ferroan and nonferroan mgsuite rocks such that only the ferroan suite rocks are likely to have formed as flotation cumulates with a data base including smaller samples the same basic pattern is seen but only in a blurred form as the two rock types show considerable overlap in their modal feldspar contents

controls of host rock mineralogy and h2o content on the nature of pseudotachylyte melts evidence from pan african faulting in the foreland of the gariep belt south africa abstract late orogenic pan african tectonics formed an 8 km long fault fracture zone in the shallow foreland crust of the gariep orogen in mesoproterozoic granitoid basement pseudotachylyte was locally formed during a single seismic event that caused brittle failure in cohesive quartz diorite granodiorite and granitic gneiss 40ar 39ar laser spot analysis provides an age of 512 5 7 5 ma for this seismic event the depth of the hypocentre between 1700 and 5300 m is inferred from the likely thickness of the overlying rock at that time abundant quartz melting in conjunction with low host rock temperature indicates a minimum seismic temperature rise exceeding 1030 c but in some samples dry quartz melting at temperatures exceeding 1700 c might have been possible the abundance of hydrous phases in the host rock controlled the volume of melt produced in a given host rock type different types of primary melt were formed by the fusion of batches of host rock with different relative proportions of plagioclase alkali feldspar quartz biotite and where present amphibole or garnet the chemical and physical interaction between these melts depended on contrasting melt mobility and viscosity in quartz diorite glasses of variable composition are well preserved and show the distribution of primary melt species at the time of quenching these different melt species had limited tendency of mixing unless mixing was assisted by syn seismic shearing in granodiorite which has a low proportion of hydrous phases low viscosity melt was formed at high temperatures eliminating most host rock fragments and leading to extensive melting of quartz the low melt viscosity probably further decreased by the dissolution of free h2o permitted effective melt homogenisation in such veins still in the liquid state these melts segregated effectively separating secondary melts of sodic calcic and of k mg fe rich composition after quenching the solid state diffusion of cations in glass was comparatively insignificant

do periglacial landscapes evolve under periglacial conditions polar and alpine periglacial areas are traditionally regarded as necessarily submitted to very efficient frost driven processes that control the holocene and ongoing geomorphic activity during the last decade the validity of this academic view has been increasingly questioned among the international scientific community the search for the real past and present processes responsible for landform evolution in cold nonglaciated areas is based mainly on more and more refined monitoring protocols relying upon sophisticated equipment to assess the representativeness and significance of monitoring data collected in restricted sites it appears necessary however to widen the perspective by adopting a twofold multiscale approach as proposed in the present paper 1 in space by integrating various scales from the general slope system to the bioclimatic nanoenvironment and 2 in time by taking into account the landscape history from tertiary inherited features to recent process changes induced by the contemporary warming reintegrating the historical approach should help both to place the ongoing processes within a succession and or combination of interoperating processes and to avoid misinterpretations of features considered wrongly as emblematic of frost action overall both the historical and monitoring approaches tend to reduce the geomorphic efficiency of frost derived processes instead the role of noncold related processes such as chemical thermal biogenic and rainfall induced ones is being emphasized of special interest would be an interdisciplinary discussion between geomorphologists and various disciplines of biological sciences including biochemistry and ecology studying processes of primary successions

reactivation of temporarily stabilized ice cored moraines in front of polythermal glaciers gravitational mass movements as the most important geomorphological agents for the redistribution of sediments a case study from ebbabreen and ragnarbreen svalbard abstract ice cored moraine complexes are prominent landforms characteristic of many polythermal glacial landsystems on svalbard usually marking their maximum little ice age extent despite being often stable over a period ranging from several years to 50 60 years the abundance of dead ice makes them potentially unstable in the future this study aims to 1 recognize the different processes that contribute to ice cored moraine degradation 2 document the spatial distribution of mass wasting sites within ice cored moraine complexes of ebbabreen and ragnarbreen svalbard 3 investigate the relationship between the distribution of mass movement sites and the topographic properties of the landscape 4 develop a model of mass wasting mechanism in a proglacial area we performed field based geomorphological mapping combined with the interpretation of aerial photographs 1960 1990 2009 high resolution satellite imagery 2013 uav based images 2014 terrestrial photographs 2011 2014 hillshade models and digital elevation models in 2013 frontal and lateral ice cored landforms occupied 3 33 km2 of the forelands of ebbabreen and ragnarbreen the total area with an unstable ice cored moraine condition was 0 57 km2 127 sites debris falls slides rolls and flows were the most important processes contributing to the reworking of glacigenic sediments and altering of their properties four different morphological site types were identified 1 near vertical ice cliffs covered with debris transformed mainly by dead ice backwasting as well as debris falls and slides 2 steep debris slopes with exposed ice cores dominated by debris slides 3 gentle sediment mantled slopes transformed by debris flows and 4 non active debris mantled areas transformed by dead ice downwasting alone the spatial and temporal activation of moraines reworking was for the most part related to local geomorphic conditions e g slope gradient occurrence of streams and meltwater channels gravitational mass movements were responsible for the redistribution of debris within the moraine complex whereas fluvial transport by meltwater exported sediments outside the little ice age moraines

paraglacial modification of slope form the morphological consequences of paraglacial modification of valley side drift slopes are investigated at six sites in norway here paraglacial slope adjustment operates primarily through the development of gully systems whereby glacigenic sediment is stripped from the upper drift slope and redeposited in debris cones downslope this results in an overall lowering of average gradient by up to 4 5 along gully axes in general slope profile adjustment appears to be characterized by a convergence of slope profiles towards an equilibrium form with an upper rectilinear slope gradient at 29 4 and a range of concavities of approximately 0 0 to 0 4 after initial rapid incision further gully deepening is limited but gullies become progressively wider as sidewall gradients decline to c 25 after which parallel retreat appears to predominate the final form of mature paraglacial gully systems consists of an upper bedrock floored source area a mid slope area of broad gullies whose sidewalls rest at stable moderate gradients and a lower slope zone where gullies discharge onto the surfaces of debris cones and fans some gullies appear to have attained this final form and have stabilized following exhaustion of readily entrainable sediment within decades of gully initiation at most sites paraglacial activity has transformed steep drift mantled valley sides into gullied slopes where an average of c 2 3 m of surface lowering has taken place at the most active sites these average amounts imply minimum erosion rates averaging c 90 mm a 1 since gully initiation which highlights the extreme rapidity of paraglacial erosion of deglaciated drift mantled slopes copyright 1999 john wiley sons ltd

from climatic to global change geomorphology contemporary shifts in periglacial geomorphology periglacial geomorphology developed in the 1940s 1960s as a branch of climatic geomorphology focusing first on quaternary studies and palaeoenvironmental reconstructions then on current geomorphi

episodic construction of the tatra granitoid intrusion central western carpathians poland slovakia consequences for the geodynamics of variscan collision and rheic ocean closure the tatra granitoid pluton central western carpathians poland slovakia is an example of composite polygenetic intrusion comprising many magmatic pulses varying compositionally from diorite to granite the u pb la mc icp ms zircon dating of successive magma batches indicates the presence of magmatic episodes at 370 368 365 360 355 and 350 340 ma all together covering a time span of 30 ma of magmatic activity the partial resorption and recycling of former granitoid material petrological cannibalism was a result of the incremental growth of the pluton and temperature in the range of 750 850 c the long lasting granitoid magmatism was connected to the prolonged subduction of oceanic crust and collision of the proto carpathian terrane with a volcanic arc and finally with laurussia closing the rheic ocean the differences in granitoid composition are the results of different depths of crustal melting more felsic magmas were generated in the outer zone of the volcanic arc whilst more mafic magmas were formed in the inner part of the supra subduction zone the source rocks of the granitoid magmas covered the compositional range of metapelite amphibolite and were from both lower and upper crust the presence of the inherited zircon cores suggests that the collision and granitoid magmatism involved crust of cadomian consolidation age c 530 and 518 ma forming the proto carpathian terrane crust of avalonian affinity 462 426 ma and melted metasedimentary rocks of volcanic arc provenance

rates of surface processes on slopes slope retreat and denudation results taken from 270 publications on rates are summarized and collated with those from 149 publications reviewed previously young 1969 1974 the data are classified by major climatic zone normal or steep relief and consolidated or unconsolidated rocks representative rates and their ranges are given for soil creep solifluction surface wash solution chemical denudation rock weathering slope retreat cliff free face retreat marine cliff retreat and denudation the last being compared with representative rates of uplift solifluction is of the order of 10 times faster than soil creep but both cause only very slow ground loss solution is an important cause of ground loss for siliceous rocks on which it may be half as rapid as on limestones total denudation brought about mainly by surface wash reaches a maximum in the semi arid and probably also the tropical savanna zones acceleration of natural erosion rates by human activities ranges from 2 3 times with moderately intense land use to about 10 times with intensive land use and considerably higher still where there is recognized accelerated soil erosion where there is active uplift typical rates are of the order of 10 times faster than denudation although in some high steep mountain ranges these may approach equality

lunar iron and titanium abundance algorithms based on final processing of clementine ultraviolet visible images the clementine mission to the moon returned global imaging data collected by the ultraviolet visible uvvis camera this data set is now in a final state of calibration and a five band multispectral digital image model dim of the lunar surface will soon be available to the science community we have used observations of the lunar sample return sites and stations extracted from the final dim in conjunction with compositional information for returned lunar soils to revise our previously published algorithms for the spectral determination of the feo and tio2 content of the lunar surface the algorithms successfully normalize the effects of space weathering so that composition may be determined without regard to a surface s state of maturity these algorithms permit anyone with access to the standard archived dim to construct high spatial resolution maps of feo and tio2 abundance such maps will be of great utility in a variety of lunar geologic studies

alpine gullies system evolution erosion drivers and control factors two examples from the western italian alps abstract denudation processes affecting mountain slopes may vary according to different factors e g lithology and structural setting of bedrock climate relief features which may be very diverse at the local scale gully complex systems characterised by morphological features similar to those developing in other climate contexts i e pseudo badlands are also becoming common at higher altitudes and latitudes the selected study cases of gran gorgia susa valley and saint nicolas aosta valley in the western italian alps are sites of geomorphological interest as they are specifically relevant for their scientific features the aims of this work are i reconstructing the morphometric evolution of gully systems and vegetation colonisation time by means of multitemporal spatial analysis on surface morphological changes under water erosion ii reconstructing in detail through dendrogeomorphological analysis the progressive spatial surface denudation and changes in erosion rates by analysing trees and exposed roots and using different indicators i e compression wood traumatic resin ducts iii obtaining data on successive aggradation degradation episodes along slopes surrounding such hotspots through geopedological investigations and iv identifying which control factors exert a predominant role on denudation patterns in such contexts multidisciplinary analyses regarding the study sites allowed for detailing of erosional history of the studied slopes detecting the prevailing drivers of their evolution according to the results and considering the common climate and bedrock conditions the structural background seems to have more influence on slope evolution at the saint nicolas site while superficial geomorphic processes seem to be more relevant at the gran gorgia site because the sites have already been recognised as part of geoheritage by local authorities the data obtained in the present research on their genesis evolution and local drivers affecting the rates of denudation i e scientific relevance of the site suggests that description of the sites for dissemination purposes should include links to the entire slope history

grenville age pseudotachylite in the lewisian laserprobe 40ar 39ar ages from the gairloch region of scotland uk infrared laserprobe 40 ar 39 ar dating has been used to date pseudotachylite and host rock minerals from a crush belt in the lewisian basement of scotland it has revealed complexity in the pseudotachylite data that is attributable to the presence of refractory host rock clasts and mineral fragments in the pseudotachylite in conjunction with the host rock mineral laserprobe 40 ar 39 ar data it has been possible to simplify the pseudotachylite data for the samples and the preferred ages for these are 980 39 ma 999 31 ma and 1024 30 ma 2 these ages are the first record of grenville aged brittle deformation in the lewisian further this study serves to illustrate the complexity of dating pseudotachylites and the advantages and limitations of the ir laserprobe applied to such materials

post lgm faulting in central europe lidar detection of the 50 km long sub tatra fault western carpathians abstract the increasing availability of high resolution lidar data reveals surprisingly strong topographic evidence of late quaternary faulting in some intraplate regions characterized by weak recent tectonic activity for the first time we present evidence of a 50 km long post last glacial maximum lgm tectonic rupture along the southern margin of the tatra mountains slovakia in the highest part of the carpathian mountains using a high resolution 1 1 m lidar dem we recognize that the normal range bounding sub tatra fault stf and its eastward branch the ru bachy fault rbf offset late quaternary glacial moraines alluvial fans and colluvial slopes the fault zone morphology is dominated by a nearly continuous southward facing up to 18 m high main scarp locally accompanied by antithetic fault scarps and hanging wall grabens similar offsets of pre lgm and lgm deposits and the absence of fault scarps within holocene alluvium suggest that the stf and rbf were active for a relatively short time interval between 18 ka and the holocene using the vertical separation of dated lgm moraine crests we estimate that the minimum average postglacial slip rates along the stf and rbf varied from 0 1 0 3 mm year i e rates one order of magnitude higher than those reported for other faults in central europe additionally deep seated landslides and the presence of large rock avalanches along the fault suggest possible postglacial high magnitude earthquake s producing coseismic rupture of the stf and rbf we conclude that 1 southern range bounding faults of the tatra mountains are the longest 50 km and only documented post lgm ruptures revealing extensive offset of late quaternary deposits in the western carpathians and 2 relatively small along strike variations in postglacial offset mimic the long term exhumation trends and imply en block uplift of the southern margin of the tatra mountains with the highest displacement along the east stf

little ice age variations of outlet glaciers from the jostedalsbreen ice cap southern norway a regional lichenometric dating study of ice marginal moraine sequences and their climatic significance complex moraine ridge sequences in front of seven outlet glaciers of the jostedalsbreen ice cap austerdalsbreen bergsetbreen fabergstolsbreen lodalsbreen stegaholbreen tuftebreen bodalsbreen are dated using families of lichenometric dating curves established previously at an eighth outlet nigardsbreen applicability of the nigardsbreen curves at the regional level is tested using independent historical evidence moraines deposited during the present century are dated to an accuracy of 9 4 yr 16 0 and most of them are dated to an accuracy of 5 5 yr 9 4 results from the moraine sequences are combined to form a composite jostedalsbreen record median predicted dates for moraine ridges cluster around ad 1939 2 yr 1929 3 1908 3 1886 5 1875 2 1867 4 1855 3 1842 5 1822 5 1807 4 and 1785 5 at least four glaciers reached their little ice age maxima prior to ad 1780 two nigardsbreen and bodalsbreen at ca 1750 one fabergstolsbreen at ca 1705 stegaholbreen attained its maximum ca 1863 since the little ice age maximum and despite large differences in glacier size frontal variations of the various outlets have exhibited a high degree of synchroneity which suggests that the moraine sequences contain a sensitive record of high frequency climatic variations over the last ca 250 yr during the early twentieth century measured readvances of the order of 5 150 m over 1 10 yr led to moraine formation dendroclimatic evidence indicates that since the late eighteenth century moraine ridges formed about 5 yr after summer temperature minima and correlate with runs of cool summers temperature depression of 0 5 1 0 c below the ad 1700 1950 average almost simultaneous glacier advances appear to have been caused by reduced ablation this near immediate response to climatic variation by glacier tongues that descend to relative low altitudes is superimposed upon the longer term dynamic response of the ice cap to climate

process interactions temporal scales and the development of hillslope gully systems howgill fells northwest england abstract hillslope gully development is often controlled by interactions between multiple processes rather than by individual processes such interactions may have both spatial and temporal characteristics a twenty year monitoring program of hillslope gullying in the howgill fells northwest england has identified the roles of both on slope interactions and slope stream coupling interactions which can be related to several temporal scales on slope interactions are primarily seasonal whereas those related to coupling produce a cyclicity over timescales of up to several years over the longer term decades or more progressive changes in gully morphology modify the nature of both sets of interactions and through negative feedback mechanisms may ultimately lead to gully stabilisation gully development is controlled by the rates of headwall recession and the basal incision stabilisation behaviour after basal stabilisation vegetation encroachment onto the eroding slopes takes place faster than headwall retreat resulting in a finite age and limiting size for gully development a simple model based on the current rates of development adequately describes the morphology of modern gullies but is inappropriate when applied to an older generation of stabilised gullies this suggests that there have been changes in sediment generation and removal rates during the late holocene

the southernmost quaternary niche glacier system in great britain until recently the scientific consensus has been that the uplands of south west britain remained unglaciated throughout the quaternary with glacial ice sheet limits lying to the north of the south west peninsula however recent work has shown that small glaciers and ice caps existed in the uplands of exmoor and dartmoor during the late quaternary demonstrating that the consensus of an unglaciated south west britain requires considerable revision here we report geomorphological and sedimentary evidence supported by glacier climate modelling for a quaternary niche glacier from west cornwall south west england this niche glacier represents the southernmost such system from mainland great britain and provides evidence for the presence of extra glacial niche glaciers probably during the last glacial maximum of the devensian glaciation and well outside the limits of the main british irish ice sheet

topographic lithologic and glaciation style influences on paraglacial processes in the upper sil and luna catchments cantabrian mountains nw spain abstract deglaciated mountainous areas are usually affected by a great range of paraglacial processes that involve progressively denudation of glacial imprints this study focuses on paraglacial processes and glacial landform preservation in six zones located in two catchments of the cantabrian mountains nw spain these zones are adjacent but display important topographic lithologic and glaciation style differences an analysis of how these variables conditioned the intensity and diversity of paraglacial processes in these zones was investigated through a detailed study of their relief lithology and paleo glacier surface using gis a comprehensive cartography of paraglacial landforms was also accomplished considering landslides alluvial fans and rock glaciers that show signs of having been conditioned by glaciation moraines and debris mantled slopes were also included in the analysis to examine their grade of preservation depending on the studied variables data comparison show that differences in glaciation style influenced paraglacial processes in the ancient icefield area relief modification by glacial action was limited and scarce paraglacial processes occur by contrast in the upper areas located in the southern ranges where an alpine style of glaciation was installed paraglacial processes were very active generating many rock glaciers lithology explains some paraglacial landforms distribution 1 landslides are associated with incohesive sandy and shale rocks 2 rock glaciers mainly occur in quartzite areas 3 in limestone areas subterranean drainage contributes to glacial landscape preservation but suffosion dolines affect some glacial deposits topography is also a key factor in paraglacial processes 1 moraines are well preserved in gently sloping valleys but rare in the steeper where they are usually transformed into moraine or debris mantled slopes 2 alluvial fans are more frequent in the steeper valleys but more dissected by postglacial river action 3 elevation and orientation show little influence on paraglacial landforms except in the generation of some periglacial features such as rock glaciers

laser microprobe 40ar 39ar analysis of pseudotachylyte and host rocks from the tatra mountains slovakia evidence for late palaeogene seismic tectonic activity laserprobe 40ar 39ar data from fault related pseudotachylytes and granitic host rocks from the tatra mountains central western carpathians resolve the controversy over the age of propagation of the sub tatra detachment fault this major structure has resulted in exhumation of crystalline basement to the north west and subsidence and sediment deposition in the palaeogene central carpathians basin to the south east host rock biotite ages range from 331 ma to 322 ma and pseudotachylyte spot ages range from 164 ma to 28 ma of these the youngest group identify the maximum timing of the early stages of tatra mountains uplift which continued in the miocene 20 10 ma and culminated during the quaternary the wide ranging older ages are an artefact of an unsupported 40ar component that is most likely a combination of both inherited and excess argon

disequilibrium of holocene sediment yield in glaciated british columbia it is generally supposed that specific sediment yield the quantity of sediment passing a monitored river cross section per unit area drained upstream of that section declines as the area drained increases1 3 part of the sediment mobilized from the land surface is supposed to go back into storage at field edges and on footslopes and floodplains in contrast we show here that data from british columbian rivers reveal a pattern of increasing specific sediment yield at all spatial scales up to 3 104 km2 this results from the dominance of secondary remobilization of quaternary sediments along river valleys over primary denudation of the land surface the result controverts the conventional model which has been derived from studies of small highly disturbed agricultural catch ments the rivers are still responding to the last glaciation giving a landscape relaxation time greater than 10 kyr this holds pro found implications for geomorphological theory and for studies of erosion

paraglacial slope adjustment since the end of the last glacial maximum and its long lasting effects on secondary mass wasting processes hauser kaibling austria abstract this study indicates the possible long lasting impacts of deep seated gravitational slope deformation dgsd on erosional and mass movement processes dgsd features are common large scale landforms in the crystalline basement rocks of the central alps of austria inactive forms are related to paraglacial nonglacial processes directly conditioned by former glaciation and deglaciation rock slope adjustment processes acting after glacier retreat towards the end of the late glacial period the near surface metamorphic bedrock of dgsd features is generally disintegrated such rock type favours erosion and the formation of small landslides field data laboratory analyses aerial photographs and gis based terrain analyses are used to describe the different geomorphic effects of an extremely disintegrated rock slope the studied dgsd hauser kaibling 13 6 km2 is located in central austria during the last glacial maximum the adjacent valley glacier reached an altitude of approximately 1900 m a s l glacier retreat in combination with the unfavourable tectono metamorphic setting caused gravity induced stresses to act subsequent sediment build up in the main valley restabilised the slope linear erosion cut a number of gullies into the lower part of the dgsd calculated mean erosional denudation rates at incised valley sections range from 0 5 to 2 6 mm a 1 since deglaciation smaller active landslides on the sides of the steep gullies draining the dgsd contribute to high denudation rates active landsliding is favoured by i fragmented rock ii steep slopes iii supply of surface and subsurface water by rain and snowmelt and iv human impact debris flows and debris charged flood events occurred frequently in the past during such events material was transported from the unstable slopes to the populated alluvial fans thus knowledge about the spatial distribution and the stage of development of dgsds active and currently inactive provides an important basis for risk management measures