schmidt hammer exposure age dating shd performed on periglacial and related landforms in opplendskedalen geirangerfjellet norway implications for mid and late holocene climate variability schmidt hammer exposure age dating shd was applied to a variety of boulder dominated periglacial landforms in an attempt to establish a local mid late holocene chronology for the geirangerfjelle

paraglacial rock slope stability glaciation and deglaciation along with their associated climatic and non climatic processes modify slope stresses and influence slope stability paraglacial slope failures are those that are a part of or influenced by the transition from glacial conditions to non glacial conditions gravitational failure of rock slopes is a primary and dominant process of slope evolution in mountainous terrain and is the subject of this paper which 1 reviews the approaches taken for researching paraglacial rock slope failure patterns and processes 2 summarises the spatial and temporal patterns of post glacial failures 3 assesses the factors influencing slope stability during glaciation and deglaciation 4 explores some of the applications of paraglacial research and 5 highlights some of the outstanding issues to be resolved and provides recommendations for terminology relating to paraglacial slope processes

rock weathering rates as functions of time the scarcity of documented numerical relations between rock weathering and time has led to a common assumption that rates of weathering are linear this assumption has been strengthened by studies that have calculated long term average rates however little theoretical or empirical evidence exists to support linear rates for most chemical weathering processes with the exception of congruent dissolution processes the few previous studies of rock weathering rates that contain quantitative documentation of the relation between chemical weathering and time suggest that the rates of most weathering processes decrease with time recent studies of weathering rinds on basaltic and andesitic stones in glacial deposits in the western united states also clearly demonstrate that rock weathering processes slow with time some weathering processes appear to conform to exponential functions of time such as the square root time function for hydration of volcanic glass which conforms to the theoretical predictions of diffusion kinetics however weathering of mineralogically heterogeneous rocks involves complex physical and chemical processes that generally can be expressed only empirically commonly by way of logarithmic time functions incongruent dissolution and other weathering processes produce residues which are commonly used as measures of weathering these residues appear to slow movement of water to unaltered material and impede chemical transport away from it if weathering residues impede weathering processes then rates of weathering and rates of residue production are inversely proportional to some function of the residue thickness this results in simple mathematical analogs for weathering that imply nonlinear time functions the rate of weathering becomes constant only when an equilibrium thickness of the residue is reached because weathering residues are relatively stable chemically and because physical removal of residues below the ground surface is slight many weathering features require considerable time to reach constant rates of change for weathering rinds on volcanic stones in the western united states this time is at least 0 5 my

improved schmidt hammer exposure ages for active and relict pronival ramparts in southern norway and their palaeoenvironmental implications abstract eight pronival protalus ramparts from alpine southern norway were dated using schmidt hammer exposure age dating shd based on local high precision linear calibration equations shd ages were 1355 1240 to 815 1000 years for three active ramparts and 8730 1050 to 14 635 1060 years for five relict ramparts different parts of the same rampart yielded ages that were in generally good agreement r value frequency distributions enabled the identification single age and mixed age boulder populations and the differentiation of active and relict rampart surfaces the relict ramparts are located outside younger dryas glacier limits and probably formed over a period of 6000 years between deglaciation following the last glacial maximum of the late weichselian 18 000 years ago and the end of the younger dryas 11 700 years ago at that time glacial debuttressing and permafrost degradation apparently enhanced the release of rock debris from rock faces to the ramparts the active ramparts which are located in areas deglaciated after the younger dryas are relatively uncommon in the study area due to diminished paraglacial effects and limited debris supply associated with seasonally frozen ground during the holocene thus the legacy of glaciers glacier permafrost interaction and the specific type of periglacial environment must all be considered when assessing the palaeoenvironmental and palaeoclimatic significance of pronival ramparts

glacier variations in breheimen southern norway relative age dating of holocene moraine complexes at six high altitude glaciers lichenometric evidence and schmidt hammer r values are used to date holocene moraine sequences in front of six high altitude 1500 m glaciers in breheimen central southern norway at three glacier forelands with southerly aspects hogsetbreen vestre hoybre and ostre hoybre relatively small 4 m high discrete boulder moraine ridges are shown to date from the little ice age the remaining three glaciers ostre tundradalskyrkjabre nordre tundradalskyrkjabre and hestdalshogdibreen with northerly or easterly aspects and large multiridged rampart like moraine complexes 15 30m thought to be ice cored and of the push deformation type lie above the local altitudinal limit of permafrost negatively skewed r value distributions from these moraine complexes provide critical evidence for pre little ice age glacier expansion as they indicate the survival of long weathered boulders on moraine surfaces where late lying snow may reduce or prevent lichen growth formation of the moraine complexes ap

neoglaciation and an early little ice age in western norway lichenometric evidence from the sandane area moraine sequences protalus ramparts rock glaciers and various slope deposits in seven separate glacier basins provide lichenometric ages for glacier retreat in an upland area of sogn og fjordane southern norway geomorphological mapping relative dating based on section rhizocarpon size frequency distributions observations on vegetation cover and numeric dating based on a regional lichen dating curve for section rhizocarpon place moraines into three groups stage 1 moraines of likely preboreal or younger dryas age stage 2 moraines of pre or early little ice age but post preboreal age thirteenth fourteenth centuries and stage 3 moraines of fifteenth century age and younger the occurrence of thirteenth sixteenth century pre or early little ice age moraines at low altitudes in the sandane area is thought to relate to greater availability of moisture and to the capture of wind drifted snow these moraines are some of the oldest little ice age moraines dated by lichenometry in southern n

erosion of sognefjord norway sognefjord is formed by a combination of exploitation of rock structure and subaerial and subglacial processes the fjord system follows zones of rock structural weakness above sea level the landforms are due mainly to subaerial processes and somewhat surprisingly not to glacial activity removal of erosive products and deepening of the fjord below sea level is due to glacial erosion

analyses of past and present rock slope instabilities in a fjord valley implications for hazard estimations abstract for quantitative hazard assessment it is necessary to define the magnitude frequency distribution and a temporal model of the landslide frequency this is often complicated for large rock slope failures due to the lack of significant numbers of large rock slope failures in inventories of a given homogeneous region or sparse information about the timing an inventory of 108 rock slope failure deposits within the fjords of the storfjord region including a relative rockslide chronostratigraphy was available for this study the temporal distribution of rock slope failures is characterized by a rapid response with a high frequency of failures directly after deglaciation followed by a lower constant frequency since 9 000 years bp for the entire storfjord region the largest recorded volumes failed directly after deglaciation volumes larger than 5 10 6 m 3 have not been recorded within the last 9 000 years in addition 17 rockslide scars and on the other hand 17 potential rock slope instabilities have been mapped at the northeastern flank of tafjord which is a branch of the storfjord volume frequency relations have been developed for the three inventories from tafjord comprising i fjord deposits ii rockslide scars and iii potential instabilities they result in very similar distributions over the entire volume range all three inventories are underlying the same processes that lead to destabilisation and finally failure additionally the compilation of the three inventories is independent and based on different methodologies the similarity of the volume frequency distributions is thus verifying the different inventories hence the obtained volume frequency relation can be used to assess the rockslide hazard for the study area present day annual expectable frequencies for different volume classes have been assessed based on the obtained volume frequency relation of the fjord deposits for example the average annual frequency for rock slope failures of v 1 10 6 m 3 originating from the northeastern flank of tafjord is 1 1670 based on a lognormal distribution this regional hazard can be used to improve previously existing qualitative susceptibility rankings for potential unstable rock slopes within the tafjord region the resulting probabilities are very low however the uncertainties of all hazard estimates are very high

schmidt hammer exposure age dating shd of snow avalanche impact ramparts in southern norway approaches results and implications for landform age dynamics and development schmidt hammer exposure age dating shd was applied to the problem of dating the diachronous surfaces of five distal river bank boulder ramparts deposited by snow avalanches plunging into the jostedola and sprongdola rivers in the jostedalsbreen region of southern norway approaches to local high precision linear age calibration which controlled in different ways for boulder roundness were developed the mean age shdmean and the maximum age shdmax of surface boulders were estimated for whole ramparts crests and distal fringes interpretation was further assisted by reference to r value distributions shdmean ages with 95 confidence intervals ranged from 520 270 years to 5375 965 years whereas shdmax ages expected to be exceeded by 5 of surface boulders ranged from 675 to 9065 years shd ages from the jostedola ramparts tended to be older than those associated with the sprongdola rampart crests were younger than the respective distal fringes and use of relatively rounded boulders yielded more consistent shd ages than angular boulders the shdmean ages indicate differences in recent levels of snow avalanche activity between ramparts and provide insights into rampart dynamics as boulders are deposited on rampart crests and in smaller numbers on the distal fringes shdmax ages provide minimum age estimates of rampart age i e the time elapsed since the ramparts began to form and suggest that at least some of the ramparts have been developing since the early holocene copyright 2015 john wiley sons ltd

the kapuskasing uplift a geological and geophysical synthesis over the past decade the kapuskasing uplift has been the subject of intense geological and geophysical investigation as lithoprobe s window on the deep crustal structure of the archean superior province enigmatic since its recognition as a positive gravity anomaly in 1950 the structure has been variably interpreted as a suture rift transcurrent shear zone or intracratonic thrust diverse studies including geochronology geothermobarometry and various geophysical probes provide a comprehensive three dimensional image of archean 2 75 2 50 ga crustal evolution and proterozoic 2 5 1 1 ga cooling and uplift the data favour an interpretation of the structure as an intracratonic uplift related to hudsonian collision eastward across the southern kapuskasing uplift erosion levels increase from 10 km in the michipicoten greenstone belt through the wawa gneiss domain 10 20 km into granulites 20 30 km of the kapuskasing structural zone juxtaposed against the low grade swayze greenstone belt al

archean continental assembly in the southeastern superior province of canada between 1988 and 1993 seismic reflection and refraction surveys were acquired across the medium to high grade opatica plutonic gneiss belt the low grade abitibi greenstone belt and the pontiac metasedimentary belt all of which form part of the late archean superior province shallowly north dipping reflections define a structural style consistent with the northward underthrusting and accretion over about 30 ma of various exotic terranes against a backstop provided by the opatica belt this rapid southward growth of the archean protocraton was driven by at least one north dipping subduction zone as revealed by north dipping reflections that extend to 65 km depth in the upper mantle below the opatica belt in contrast to the mainly orthogneissic opatica and pontiac belts the midcrust of the abitibi belt comprises metasedimentary and igneous rocks plus imbricated units of unknown affinity relict midcrustal accretionary complexes of substantial size whieh are indicative of primary suture zones are interpreted near the northern and southern limits of the abitibi belt an interpreted basal decollement and significantly older ages in the north suggest that the upper crustal greenstone rocks are allochthonous evidence of large scale extension appears to be confined to the southern volcanic zone of the abitibi which developed into a half graben as the original suture zone was reactivated in extension unusually high seismic p wave velocities 7 5 8 2 kms 1 are present in the lower 8 km of the abitibi crust and they correlate well with a downward reduction in seismic reflectivity attributable to late modification of the deepest part of the crust crustal xenolith studies suggest that this process may be linked to early proterozoic magmatism

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

investigation of late holocene moraines in the western southern alps new zealand applying schmidt hammer exposure age dating chronological studies applying schmidt hammer exposure age dating shd were performed on six glacier forelands in the western part of the southern alps new zealand although lithological heterogeneity prevented a regional age calibration curve to be established local age calibration curves for la perouse glacier and strauchon glacier could be derived they show similar linear equations and trends slopes and enabled a preliminary assessment of the representativeness of individual 10be terrestrial cosmogenic nuclide dating tcnd ages obtained from the other forelands no mid and early holocene advance periods were detected clusters of moraine ages date around 2800 1850 1450 and 1100 900 years ago followed by the little ice age commencing c 500 years ago there is no good agreement with earlier radiocarbon based studies and recently published tcnd chronologies as it will be outlined this partly could be the result of different approaches to the palaeoclimatic interpretation of the dated samples

intracrustal extension of an archean orogen revealed using single grain u pb zircon geochronology the metaplutonic wawa gneiss domain in the southern superior province is part of an uplifted block that was exhumed during the proterozoic exposing the lower crustal 30 km levels of the late archean 2720 to 2670 ma abitibi wawa orogen previous structural and geophysical studies of the midcrustal wawa gneiss domain reveal subhorizontal shear zones that formed during orogen parallel extension and correspond to gently dipping seismic reflectors present at depth elsewhere in the orogen in order to bracket the age of this extensional deformation the ages of metre scale igneous bodies that crystallized before and after extension have been determined in four outcrops using single grain u pb zircon dating techniques the results constrain the time of extension to the interval between 2660 and 2645 ma and show that deformation was coeval with pegmatite emplacement partial melting of tonalite gneisses as old as 2925 35 ma and regional circa 2660 ma granulite facies metamorphism of adjacent more deeply eroded crust this extension and associated high grade metamorphism in the wawa gneiss domain occurred 10 to 25 m y after the cessation of regional compression major transcurrent fault movement and sediment deposition in the upper structural levels of the orogen the middle and lower crust was therefore mechanically decoupled from the upper crust during this period of orogen parallel extension this intracrustal style of deformation is interpreted to be the consequence of gravitational forces working on a thermally softened middle crust the detachment of lithosphere from the orogen base is the favored mechanism for generating these forces and for introducing the heat that caused synextension metamorphism cyclic construction and delamination of orogen lithosphere could account for even younger metamorphic strain events evident in nearby exposures of lower crust

accretion of archean oceanic plateau fragments in the abitibi greenstone belt canada the arc arc collision model is often applied to the evolution of archean greenstone belts this model predicts concordant stratigraphic relations among the various lithologies evolving generally from komatiitic tholeiitic affinities toward calc alkalic affinities new geological data from the malartic composite block of the abitibi greenstone belt indicate that this volcanic pile rather than representing a conformable sequence is composed of four distinct mafic lithotectonic domains that are overlain by a calc alkalic sequence the mafic domains are thought to be examples of accreted archean oceanic plateau material that were deformed during their collage state the younger calc alkalic sequence represents extension related volcanism that erupted through the ac creted and deformed plateau material possibly as a consequence of ridge subduction in a regime of oblique convergence the relations described here may represent a common feature of archean terranes

rock control on microweathering of bedrock surfaces in a periglacial environment abstract microweathering of ice smoothed bedrock surfaces was investigated in the roldal area of hardanger plateau 60 southern norway postglacial rates of weathering were determined from surface lowering using quartz veins as reference surfaces weathering processes are inferred from assessment of weathering rind formation surface hardness and the preservation of small scale glacial erosional features surface lowering rates for a range of metamorphic rocks vary from 0 05 to 2 20 mm ka 1 and are broadly comparable with those obtained from crystalline rocks in other periglacial environments the mean rate of surface lowering at 0 55 mm ka 1 is low and demonstrates the relatively small impact of microweathering on postglacial landscape evolution variations in bedrock microweathering can be explained by lithological variation amphibolite and mica rich bedrock surfaces experience greater denudation and weakening least weathering rind formation and abundant preservation of glacial striae despite greater surface lowering conversely quartz rich bedrock surfaces are most resistant to denudation and weakening but have greater weathering rind formation and fewer preserved striae postglacial microweathering is achieved primarily through granular disintegration involving detachment and removal of mineral grains and weakening from increased porosity granular decomposition is manifest in the formation of weathering rinds analysis of interactions between weathering indices indicates that rind accumulation is limited by microerosion a conceptual model is proposed that illustrates the temporal interrelationships between in situ and erosional facets of microweathering in two contrasting mineral assemblages the model proposes that cyclic processes of in situ disintegration decomposition and erosion are at work the relative balance between these processes varies with lithology so that in more resistant quartz rich rocks the net effect is minimal surface lowering and accumulation of weathering rind in weaker amphibolitic and micaceous rocks the net effect is greater surface lowering and minimal accumulation of weathering rind the results of the research demonstrate the important influence of rock properties notably mineral composition in postglacial microweathering of crystalline bedrock in a periglacial environment

the greenland 8200 cal yr bp event detected in loss on ignition profiles in norwegian lacustrine sediment sequences high resolution loss on ignition analyses of lacustrine sediment cores from both proglacial and non glacial lakes in southern norway have revealed a specific pattern characterised by a significant two peaked reduction of the loss on ignition values in the basal half of the cores in non glacier fed lakes the loss on ignition variations are interpreted to reflect mainly lake productivity and hence variability in surface summer air temperature sediments deposited in proglacial lakes however reflect mainly the glacier activity in the lake catchment bulk ams radiocarbon dates from the core sequences and the loss on ignition curve pattern suggest that this event correlates with the 8200 cal yr bp event recorded in the grip and gisp2 greenland ice cores termed the finse event in southern norway copyright 2001 john wiley sons ltd

tectonic setting and terrane accretion of the archean zimbabwe craton the archean zimbabwe craton is made of a number of distinct tectonostratigraphic terranes assembled by plate tectonic processes the central tokwe terrane consists of 3 5 2 95 ga gneissic rocks and structurally complex inliers of possibly older greenstone belts these are overlain unconformably by a 2 9 2 8 ga assemblage of mafic and felsic volcanic rocks and conglomerates and a separate 3 0 2 7 ga southeastward thickening platform sequence of sandstone shale and limestone 2 7 ga greenstone belts form two distinctly different domains flanking the central terrane northwest of the ancient gneissic terrane ca 2 7 ga greenstone belts comprise a series of calc alkaline lavas and intercalated sedimentary rocks intruded by syn volcanic plutons southeast of the ancient gneissic complex 2 7 ga greenstone belts consist of thick piles of tholeiitic basalts overlying ultramafic lavas resting allochthonously over the shallow water platform sequence and older gneissic terrane this division of the zimbabwe craton is interpreted to show that the central tokwe terrane had a continental magmatic arc built on its northwestern edge as its southeastern margin rifted from another fragment forming the sea of umtali a passive margin sedimentary wedge formed on the rifted southeastern edge of this ancient continent and prograded onto the craton during sedimentary and tectonic loading of the craton margin the southeastern greenstone belts formed as thick oceanic crust oceanic plateau in this back arc basin and were later obducted on to the rift and passive margin sequence as the sea of umtali closed ca 2 7 ga this was followed by intrusion of granitic plutons of the chilimanzi suite ca 2 6 ga in a tectonic regime of intracontinental strike slip faulting representing a response to the zimbabwe kaapvaal continent continent collision crustal and lithospheric thickening during intrusion of these late granites may have played a role in stabilizing the zimbabwe craton and forming the lithospheric root

deep seated failure propagation in a fractured rock slope over 10 000 years the la clapiere slope the south eastern french alps abstract the la clapiere area tinee valley alpes maritimes france is a typical large complex unstable rock slope affected by deep seated gravitational slope deformations dgsd with tension cracks scarps and a 60 106 m3 rock slide at the slope foot that is currently active the slope surface displacements since 10 ka were estimated from 10be ages of slope gravitational features and from morpho structural analyses it appears that tensile cracks with a strike perpendicular to the main orientation of the slope were first triggered by the gravitational reactivation of pre existing tectonic faults in the slope a progressive shearing of the cracks then occurred until the failure of a large rock mass at the foot of the slope by comparing apertures variations and changes in direction between cracks of different ages three phases of slope surface displacement were identified 1 an initial slow slope deformation spreading from the foot to the top characterized by an average displacement rate of 4 mm yr 1 from 10 5 6 ka bp 2 an increase in the average displacement rate from 13 to 30 mm yr 1 from the foot to the middle of the slope until 3 6 ka bp and 3 development of a large failure at the foot of the slope with fast displacement rates exceeding 80 mm yr 1 for the last 50 years the main finding of this study is that such a large fractured slope destabilization had a very slow displacement rate for thousands of years but was followed by a recent acceleration the results obtained agree with several previous studies indicating that in situ monitoring of creep of a fractured rock slope may be useful for predicting the time and place of a rapid failure

archean terrane docking upper crust collision tectonics abitibi greenstone belt quebec canada abstract the northern nvz and southern volcanic zones svz of the abitibi greenstone belt are separated by the major e trending destor porcupine manneville fault zone dpmfz the dpmfz is interpreted to be the locus of archean terrane docking between the older diffuse volcanic arc of the nvz 2730 2710 ma and the younger arc segments of the svz 2705 2698 ma two distinct evolutionary phases can be documented along the dpmfz of the abitibi greenstone belt and include 1 arc arc collision occurring between 2697 and 2690 ma and 2 arc fragmentation between 2689 and 2680 ma identification of these two events along the dpmfz is based on detailed structural studies sedimentary basin analysis and precise u pb age determinations the thrusting event representative of the arc arc collision phase is characterized by shallow north dipping foliations 20 40 and dip parallel stretching lineations in the eastern manneville segment of the dpmfz local overturned mafic pillowed units suggest recumbent folding late strike slip or transcurrent movement displayed in the late orogenic sedimentary duparquet basin records the arc fragmentation phase basin geometry e trending en echelon folds shallow e plunging stretching lineations and a late ne striking cleavage cross cutting the folds support a dextral shear sense along the western destor porcupine segment of the dpmfz the sedimentary facies observed in the basin are consistent with those of modern strike slip basins located along the east anatolian fault turkey hazar lake and the hope fault new zealand hanmer basin precise u pb zircon age determinations from porphyry stocks located at the northern and southern limits of the duparquet basin yielded 2681 1 ma and 2689 3 2 2 9 ma respectively these ages constrain the rapid change from thrusting to transcurrent movement it is apparent that once thrusting ceased the response to oblique subduction continued in the form of strike slip displacement modern fold and thrust belts commonly show this evolution the deformation pattern is the result of oblique convergence the abitibi greenstone belt is considered to be an archean analogue of modern subducting oceanic plates such as those found in the western pacific

latest pleistocene and holocene alpine glacier fluctuations in scandinavia abstract during the early holocene abrupt decadal to centennial scale climate variations caused significant glacier variations in norway increased freshwater inflow to the north atlantic and arctic oceans has been suggested as one of the most likely mechanisms to explain the abrupt and significant lateglacial and early holocene climatic events in nw europe the largest early holocene glacier readvances occurred 11 200 10 500 10 100 9700 9200 and 8400 8000 cal yr bp the studied norwegian glaciers apparently melted away at least once during the early mid holocene the period with the most contracted glaciers in scandinavia was between 6600 and 6000 cal yr bp subsequent to 6000 cal yr bp the glaciers started to advance and the most extensive glaciers existed at about 5600 4400 3300 2300 1600 cal yr bp and during the little ice age times with overall less glacier activity were apparently around 5000 4000 3000 2000 and 1200 cal yr bp it has been proposed that several glacier advances occurred in scandinavia including northern sweden at 8500 7900 7400 7200 6300 6100 5900 5800 5600 5300 5100 4800 4600 4200 3400 3200 3000 2800 2700 2000 1900 1600 1200 1000 and 700 200 cal yr bp glaciers in northern sweden probably reached their greatest little ice age extent between the 17th and the beginning of the 18th centuries evidence for early holocene glacier advances in northern scandinavia however has been questioned by more recent multi disciplinary studies the early to mid holocene glacier episodes in northern sweden may therefore be questioned most norwegian glaciers attained their maximum little ice age extent during the mid 18th century cumulative glacier length variations in southern norway based on marginal moraines dated by lichenometry and historic evidence show an overall retreat from the mid 18th century until the 1930s 40s subsequently most norwegian glaciers retreated significantly maritime outlet glaciers with short frontal time lags 15 20 years continued their retreat to the 1970s and 1980s however maritime glaciers started to advance as a response to higher winter accumulation during the first part of the 1990s after 2000 several of the observed glaciers have retreated remarkably fast annual frontal retreat 100 m mainly due to high summer temperatures the general glacier retreat during the early holocene and the neoglacial advances after 6000 cal yr bp are in line with orbital forcing due to the decrease of northern hemisphere summer solar insolation and the increase in winter insolation in addition regional weather modes such as the north atlantic oscillation nao and the arctic oscillation ao play a significant role with respect to decadal and multi decadal climate variability

lateglacial rock slope failures in north west ireland age causes and implications nine postglacial quartzite rock slope failures rsfs in north west ireland were dated using cosmogenic 10be weighted mean rsf ages range from 17 7 0 9 to 12 5 0 7 ka or 16 6 0 7 to 11 7 0 5 ka depending on assumed 10be production rate all dated rsfs occurred within 5000 years following ice sheet deglaciation at 17 4ka 16 3 ka and all but two occurred within 2000 years after deglaciation the timing of rsfs rules out glacial debuttressing permafrost degradation and enhanced deglacial cleft water pressures as triggers of failure in most cases we infer that paraglacial stress release and associated fracture propagation were critical in reducing rock masses to critical stability although earthquakes caused by lateglacial glacio isostatic rebound and or release of stored tectonic stresses may have triggered failure in some or all cases in conjunction with data from related studies our results imply that most undated rsfs outside the limit of younger dryas glaciation in the british isles are of lateglacial age and that numerous lateglacial rsfs occurred inside these limits with subsequent removal of debris by glaciers they support the view that paraglacial rsf activity in tectonically stable intraplate terrains was concentrated within a few millennia following deglaciation

komatiite flooding of a rifted archean rhyolitic arc complex geochemical signature and tectonic significance of the stoughton roquemaure group abitibi greenstone belt canada the 0 2 2 km thick archean stoughton roquemaure group srg in the northern volcanic zone of the abitibi greenstone belt quebec canada is composed of tholeiitic basalt komatiitic basalt and komatiite the mafic and ultramafic rocks are pillowed brecciated and massive columnar jointed flows the srg conformably overlies the 2730 ma hunter mine group a volcanic complex dominated by calc alkaline felsic rocks the tholeiitic basalts of the srg resemble morb the komatiitic basalts and komatiites have positive nd values overlapping those of the tholeiitic basalts komatiitic basalts with low al2o3 tio2 ratios 10 and fractionated heavy ree patterns are similar to al depleted komatiites in contrast the komatiites have high al2o3 tio2 20 unfractionated heavy ree patterns and resemble al undepleted munro type komatiites the al depleted komatiitic basalts occur at the base of the srg whereas the al undepleted komatiites are prevalent higher up in the stratigraphy the association of calcalka

the schmidt hammer in rock material characterization the schmidt hammer provides a quick and inexpensive measure of surface hardness that is widely used for estimating the mechanical properties of rock material however a number of issues such as hammer type normalization of rebound values specimen dimensions surface smoothness weathering and moisture content and testing data reduction and analysis procedures continue to influence the consistency and reliability of the schmidt hammer test results this paper presents a a critical review of these basic issues and b the results of tests conducted on granitic rocks of various weathering grades in the light of the conclusions of this review it was found that a very good correlation exists between l and n hammer rebound values and that both hammers are fairly sensitive to the physical properties particularly to dry density though less so to effective and total porosities the n hammer producing a lesser scatter in the data proved to be more efficient than the l hammer in predicting uniaxial compressive strength and young s modulus the exponential form of the correlation curves was found to reflect microstructural changes during the course of weathering and the differences in the probing scales or mechanisms in the means of measuring these mechanical properties and could be generalized to other crystalline igneous rocks the possibility of predicting weathering grades from rebound values was also explored the changes in the rebound values during multiple impacts at a given point produced a better indication of the weathering grade than a single impact value it was concluded that increasing the impact energy and plunger tip diameter should significantly reduce the scatter in coarse grained weathered rocks and hence improve the reliability of the schmidt hammer as a rock material characterization tool

cosmogenic 10be and 26al ages of holocene moraines in southern norway i testing the method and confirmation of the date of the erdalen event c 10 ka at its type site abstract cosmogenic nuclide dating 10be and 26al is applied to boulders on two moraine ridges at the type site of the early holocene erdalen event southern norway dated previously using radiocarbon quartz rich rock samples yielded 10be age estimates between 9 8 1 2 and 10 1 1 1 ka external uncertainties 1 with an average of 9 95 ka these age estimates are statistically indistinguishable from the independent radiocarbon age estimate 26al age estimates which ranged from 9 4 1 1 to 11 2 1 3 ka and averaged 10 1 ka provided useful corroboration of the 10be results although current levels of precision and accuracy are insufficient to distinguish between the ages of younger inner and older outer moraines the results demonstrate the potential of the method at suitable sites where radiocarbon dating is not possible several environmental factors including effective glacial erosion stability of moraine slopes snow cover of sufficiently shallow depth and short duration and the absence

age assessment and implications of late quaternary periglacial and paraglacial landforms on muckish mountain northwest ireland based on schmidt hammer exposure age dating shd abstract schmidt hammer exposure age dating shd was applied to a variety of late quaternary periglacial and paraglacial landforms composed of coarse rock debris on muckish mountain northwest ireland landform ages were determined using a linear high precision age calibration curve derived from young and old control surfaces of known age on the same rock type the shd ages represent maximum estimates of the time elapsed since the boulders stabilised and the landforms became inactive most ages are also minimum estimates for the start of landform development because older boulders are buried beneath the sampled surface boulders ages and 95 confidence intervals obtained for blockfield boulder lobes and talus indicate these features were likely active during several of the early holocene cold events evidenced in greenland ice cores and north atlantic sediment records activity ceased at different times 9 7 ka bp these landforms are the first indication of a geomorphological response to early holocene cooling in the oceanic mountains of ireland late holocene ages obtained for rock slope failure run out debris and debris cone boulders overlap with shifts to cooler and or wetter conditions including the little ice age geomorphological impacts associated with these changes in climate have not previously been recorded in the irish uplands the shd results indicate that previously implied timings for the stabilisation of some accumulations of coarse rock debris on mountain slopes are in need of revision

correlation of late quaternary moraines impact of climate variability glacier response and chronological resolution abstract the last decade has seen a global surge in the number and resolution of well dated geomorphological reconstructions of mountain glacier fluctuations and former ice sheet extents this has been facilitated by the widespread deployment of large samples of terrestrial cosmogenic nuclide dating tcnd allowing more sophisticated probability analyses for reducing the statistical uncertainty of moraine ages and testing of correlations at local regional and hemispheric scales geochronological advances in the field laboratory and on model calibration have taken place in parallel with modelling of palaeoclimate based on glacier reconstructions and of glacier sensitivity to temperature and precipitation forcing in spite of these advances basic conceptual issues remain this review questions whether the technical leap forward in dating has encouraged us to over reach our interpretive limits particularly in terms of the concept and practice of correlation we propose that to enable reliable correlation glacier chronologies should first be examined for their climatic integrity spatial coherence and chronological robustness even with excellent dating interpretive complexity remains due to complex climate signals and glacier response characteristics and to erosion censoring of the landform record all are issues which must be addressed to avoid either spurious lumping correlation or splitting differentiation of glacier chronologies and thus misinterpretation of the climatic significance of reconstructed glacier advances we suggest that the reliability of correlation is no better than the weakest link in the chain of reasoning which connects climatic fluctuations with dated landforms and sediments improved dating means that poor chronological resolution is less likely to be the limiting factor for correlation but shifts the focus onto other less quantifiable sources of uncertainty these conceptual statements are exemplified with reference to holocene glacial chronologies of contrasting mid latitude environments in southern norway iceland and new zealand

precise 14c ages of the vedde and saksunarvatn ashes and the younger dryas boundaries from western norway and their comparison with the greenland ice core gicc05 chronology the greenland ice cores with the gicc05 chronology represent a standard for late quaternary climate events and their ages whereas many other palaeoclimatic archives are dependent on 14 c dates it is therefore critical to know if the ice core and the calibrated 14 c chronologies are identical and if not to quantify the offset between them we present bayesian age depth modelling of 118 accelerator mass spectrometry 14 c dates from kraukenes lake calibrated using intcal09 that provide high precision ages of 12 066 42 and 10 210 35 cal a bp for the vedde and saksunarvatn ashes respectively the lower and upper younger dryas boundaries have ages of 12 710 52 and 11 546 59 cal a bp respectively the four dated levels coincide with correlative levels in gicc05 within the dating uncertainties but are all consistently younger at kraukenes the ages of the tephra chronostratigraphic markers suggest a mean offset of 70 years to older ages in the gicc05 compared with the intcal09 time scale responses to small climate changes 30 years before the younger dryas boundaries at kraukenes are suggested to correspond to the defined greenland stadial 1 boundaries this suggested difference in timing 30 years and time scale offset 70 years mean that the greenland stadial 1 boundaries appear 100 years older than the younger dryas boundaries copyright 2013 john wiley sons ltd

the schmidt hammer as a relative age dating tool and its potential for calibrated age dating in holocene glaciated environments the schmidt hammer is a relatively cheap portable sturdy instrument with proven value over the last two decades or so in rapidly dating coarse inorganic deposits of diverse origins early views were that its dating role was limited to distinguishing recently exposed from much older typically either a few sites of possibly different ages or occasional older surfaces amongst many young sites were studied more recently calibration curves based on individual r value means from small numbers 2 4 of sites of known ages have been used to estimate the ages of undated sites we present schmidt hammer rebound r values from 28 little ice age and younger 23 preboreal and 7 younger dryas glaciated surfaces in southern norway in order first to test rigorously the robustness of the instrument as a relative age dating tool despite being obtained from different surfaces moraines glaciofluvial deposits and bedrock and varied metamorphic lithologies the r value overall means and 95 confidence intervals for the little ice age preboreal and younger dryas age categories respectively 60 0 1 6 41 6 1 4 and 34 2 2 0 are statistically significantly different only two outlying sites in the two younger age categories have overlapping confidence intervals demonstrating remarkable robustness in differentiating early and late holocene surfaces the distinction between preboreal and younger dryas sites with terminal dates 2000 years apart is less clear but still statistically significant though possibly partly because of enhanced weathering conditions at the predominantly well vegetated younger dryas sites second we examine the feasibility and desirability of controlling non age related factors including some previously considered critical instrument wear operator bias initial rock surface texture which emerge either as less important than previously argued or as relatively unimportant together with others previously unreported e g long term changes in lichen soil snow and vegetation covers third we investigate the potential for calibrated age dating by applying exploratory linear rates of r value decline to selected combinations of sites the results suggest that error limits of ca 700 to 1600 years should be achievable over the holocene timescale this improved dating capability however will require adequate numbers of site means not only for each age category used to define these curves but also for each set of test surfaces of the same ages recommendations are made for a suitable sampling protocol for developing further the schmidt hammer as a calibrated age dating tool

holocene glacier variation chronology of the smorstabbtindan massif jotunheimen southern norway and the recognition of century to millennial scale european neoglacial events new stratigraphic evidence for the holocene history of three glaciers in central jotunheimen southern norway is presented and the implications for century to millennial scale glacier and climatic variability are considered minerogenic layers in seven stream bank mires flooded episodically by glaciofluvial meltwater are dated by 79 new radiocarbon age estimates a revised chronology for glacier variations in smorstabbtindan suggests a three phase holocene 1 an early holocene deglaciation phase 11500 9500 cal bp characterized by readvances of ice sheet remnants 2 a mid holocene phase with relatively small or absent glaciers 9500 5000 cal bp and 3 a late holocene phase of enlarged and fluctuating glaciers the last 5000 years seven millennial scale neoglacial events smorstabbtindan i vii during which glaciers were larger than at present for most of the time are dated to 10 400 9600 erdalen event 8400 7650 finse event 4800 3900 3200 2550 2350 1700 1400 750 and 500 0 cal

cosmogenic 10be and 26al ages of holocene moraines in southern norway ii evidence for individualistic responses of high altitude glaciers to millennial scale climatic fluctuations abstract 10be and 26al exposure ages are reported for boulder moraine ridges in front of two high altitude cirque glaciers austanbotnbreen jotunheimen and ostre tundradalskyrkjabre breheimen in southern norway ages and 1 external uncertainties for austanbotnbreen moraines range from 7 4 0 75 ka to 8 7 0 9 ka when no adjustment for snow shielding is made with the maximum conceivable snow cover effect 2 m thick a density of 0 2 g cm3 6 months duration at the exposed site the resulting adjusted 7 7 0 8 to 10 9 1 3 ka as well as unadjusted ages suggest moraine formation possibly during both the 8 2 ka event finse event in southern norway and the erdalen event c 10 0 ka in contrast ages obtained for the outer ridges of the large moraine complex in front of ostre tundradalskyrkjabre range from 1 1 0 3 ka to 1 9 0 4 ka assuming no snow shielding assuming extreme snow lie conditions 4 m thick 0 2 g cm3 density 6 months duration at this more sheltered site the adjusted ages

rock slope failure following late pleistocene deglaciation on tectonically stable mountainous terrain the ages of 31 postglacial rock slope failures rsfs in scotland and nw ireland derived from 89 cosmogenic isotope exposure ages are employed to analyse the temporal pattern of failure and its relationship to the timing of deglaciation rates of glacio isostatic crustal uplift and periods of rapid climate change rsf ages span almost the whole period since ice sheet retreat from 18 2 1 2 ka to 1 7 0 2 ka or from 17 1 1 0 ka to 1 5 0 1 ka depending on the production rate used in 10 be age calculation but catastrophic failure of rock slopes was w4 6 times more frequent prior to w11 7 ka than during the holocene 95 of dated rsfs at sites deglaciated during retreat of the last ice sheet occurred within w5400 years after deglaciation with peak rsf activity 1600e1700 years after deglaciation this time lag is inferred to represent 1 stress release initiated by deglacial unloading leading to 2 time dependent rock mass strength degradation through progressive failure plane development and ultimately 3 to either spontaneous kinematic release or failure triggered by some extrinsic mechanism by contrast 11 dated rsfs at sites reoccupied by glacier ice during the younger dryas stade yds of w12 9e11 7 ka exhibit no clear temporal pattern suggesting that glacial reoccupance during the yds was ineffective in preconditioning a renewed cycle of enhanced rsf activity comparison of timing of individual rsfs with that of deglaciation and rapid warming events at w14 7 ka and w11 7 ka suggests that glacial debuttressing enhanced joint waterpressuresduringdeglaciationandthawofpermafrosticeinrockjointscouldhavetriggeredfailurein only a small number of cases conversely the timing of maximum rsf activity following ice sheet deglaciation corresponds broadly with maximum rates of glacio isostatic crustal uplift suggesting that the two are linked by enhanced seismic activity a seismic failure trigger is consistent with full slope failure at all sites where failure planes are clearly defined our results indicate that numerous rsfs must have occurred in areas that were reoccupied by glacier ice during the yds but have not been identified because runout debris was removed by yds glaciers more generally they provide the first reliably dated body of evidence to support the view that retreat of the last ice sheets in tectonically stable mountainous terrain initiated a period of enhanced rock slope failure due to deglacial unloading and probably lateglacial seismic activity implying that most undated rsfs in such areas are probably of lateglacial or veryearly holocene age they also demonstrate however that a low frequency of rsf activity extended throughout the holocene

impacts of post glacial rebound on landslide spatial distribution at a regional scale in northern iceland skagafjorður in de glaciated areas para glaciation i e the conditioning of landscapes by prior glaciation has often been considered a major predisposing factor in landslide occurrence its consequences have been particularly well identified at a fine scale especially on bedrock jointing hitherto the relative impacts of para glaciation on hillslope dynamics at a regional scale had nevertheless not been quantified statistically we examine skagafjor ur area northern iceland where landslides are widespread at least 108 were mapped in an area of c 3000km2 we compare the role of para glaciation debuttressing influence of post glacial rebound with that of classic factors topography lithology etc in landslide occurrence and location using a spatial analysis based on a chi square test on the one hand the results highlight that landslides are over represented in areas where post glacial rebound was at its maximum with a stronger concentration of landslides in the northern part of the fjord on the other hand the distribution of landslides did not show any clear relationship with the pattern of glacial debuttressing tschuprow coefficient highlights that the influence of post glacial rebound on landslide location is higher than the combined influence of slope gradient curvature or geological structure this result is supported by our initial evidence for the timing of landslides in the area most landslides occurred during the first half of the holocene and a period of hillslope instability was initiated when the post glacial uplift was at its maximum finally the mechanisms that link post glacial rebound and landsliding as well as the geomorphic impacts of landslides are discussed

deglaciation of fennoscandia abstract to provide a new reconstruction of the deglaciation of the fennoscandian ice sheet in the form of calendar year time slices which are particularly useful for ice sheet modelling we have compiled and synthesized published geomorphological data for eskers ice marginal formations lineations marginal meltwater channels striae ice dammed lakes and geochronological data from radiocarbon varve optically stimulated luminescence and cosmogenic nuclide dating this is summarized as a deglaciation map of the fennoscandian ice sheet with isochrons marking every 1000 years between 22 and 13 cal kyr bp and every hundred years between 11 6 and final ice decay after 9 7 cal kyr bp deglaciation patterns vary across the fennoscandian ice sheet domain reflecting differences in climatic and geomorphic settings as well as ice sheet basal thermal conditions and terrestrial versus marine margins for example the ice sheet margin in the high precipitation coastal setting of the western sector responded sensitively to climatic variations leaving a detailed record of prominent moraines and other ice marginal deposits in many fjords and coastal valleys retreat rates across the southern sector differed between slow retreat of the terrestrial margin in western and southern sweden and rapid retreat of the calving ice margin in the baltic basin our reconstruction is consistent with much of the published research however the synthesis of a large amount of existing and new data support refined reconstructions in some areas for example the lgm extent of the ice sheet in northwestern russia was located far east and it occurred at a later time than the rest of the ice sheet at around 17 15 cal kyr bp we also propose a slightly different chronology of moraine formation over southern sweden based on improved correlations of moraine segments using new lidar data and tying the timing of moraine formation to greenland ice core cold stages retreat rates vary by as much as an order of magnitude in different sectors of the ice sheet with the lowest rates on the high elevation and maritime norwegian margin retreat rates compared to the climatic information provided by the greenland ice core record show a general correspondence between retreat rate and climatic forcing although a close match between retreat rate and climate is unlikely because of other controls such as topography and marine versus terrestrial margins overall the time slice reconstructions of fennoscandian ice sheet deglaciation from 22 to 9 7 cal kyr bp provide an important dataset for understanding the contexts that underpin spatial and temporal patterns in retreat of the fennoscandian ice sheet and are an important resource for testing and refining ice sheet models

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

a special issue devoted to abitibi ore deposits in a modern context preface the abitibi greenstone belt which is part of the larger abitibi subprovince in the superior province of the canadian shield e g card and ciesielski 1986 is the largest known archcan greenstonegranite terrane 300 km n s x 400 450 km mineral production and reserves are significant particularly in relation to volcanogenic massive sulfide deposits and structurally controlled archcan goldbearing quartz vein systems the term au quartz vein being used in the sense of lindgren 1933 e g the gold quartz veins of ontario p 662669 volcanogenie massive sulfide production and reserves to 1989 1990 total 424 million metric tons

a new approach to calculating holocene winter precipitation by combining glacier equilibrium line altitudes and pine tree limits a case stud from hardangerjokulen central southern norway at hardangerjokulen central southern norway detailed knowledge of the number age and magnitude of holocene glacier fluctuations is used to reconstruct variations in equilibrium line altitude ela for the last 10 000 years present and past elas are based on an accumulation area ratio aar of 0 7 and are adjusted for land uplift a synchronous relationship between advanced glacier positions and the highest pine tree limits pinus sylvestris l is demonstrated for the early to mid holocene in southern scandinavia which indicates that warm summers were compensated for by high winter precipitation based on pine tree limit fluctuations as a measure of mean ablation season temperature holocene variations in winter precipitation at hardangerjokulen have been calculated by substitution in the close exponential relationship between mean ablation season temperature and winter precipitation at the ela of norwegian glaciers setting the winter precipitation during the period ad 1961 1990 at 100 mean values

application of schmidt hammer relative age dating to late pleistocene moraines and rock glaciers in the western tatra mountains slovakia abstract in order to evaluate the potential of the schmidt hammer for relative age dating of late pleistocene moraines and rock glaciers rebound r values were collected at 38 sites in two formerly glaciated valleys in the western tatras in northern slovakia a large statistical population of measurements obtained from moraine and rock glacier surfaces was used to analyze the variability of mean r values in the same lithology and overall southern valley exposition four separate sets of glacial periglacial morphosystems are present at different positions in the western tatras starting from valley outlets to the highest cirques which represent successive phases of deglaciation r value means and 95 confidence intervals for selected last glacial maximum lgm and late glacial lg 1 lg 2 and lg 3 stages respectively 40 1 1 1 46 0 5 53 5 1 0 and 60 5 0 3 are significantly statistically different and values for each age category are comparable for the two analyzed valleys the results of weathering indexes used in conjunction with geomorphological relationships were taken together to reconstruct the pattern of deglaciation on southern tatra slopes it is stated that the schmidt hammer technique may be successfully used as a relative age dating tool for late pleistocene glacial and periglacial deposits and with this method it is possible to differentiate between late glacial moraines and rock glacier systems of different age

assessing the age weathering correspondence of cosmogenic 21ne dated pleistocene surfaces by the schmidt hammer the schmidt hammer sh method is used to quantify the rock weathering degree and has been proposed as a relative dating tool terrestrial cosmogenic nuclide tcn methods provide absolute exposure ages for erosive surfaces few works combine both methods for surfaces older than the holocene we compare data obtained by both methods for c 150 ka bp glacial and fluvial erosive granite surfaces from northwest spain rebound values r have been firstly compared with the rock density to assess the correlation with the rock strength independently from influence of factors such as wetness and roughness in the r values for erosive glacial surfaces older than 100 ka r values are confined in a narrow range with no differences within errors stepped fluvial surfaces of 700 m to 70 m above present sea level show an inverse correspondence between tcn ages and r values although no age predictions can be done on the basis of the r values thus age inferences exclusively based on r values may not be realistic but sh studies could be a useful tool for selecting surfaces for tcn dating copyright 2009 john wiley sons ltd

reconstruction of former glacier equilibrium line altitudes based on proglacial sites an evaluation of approaches and selection of sites abstract various approaches are used to record variations in glacier activity and equilibrium line altitudes elas based on proglacial sites lacustrine and terrestrial these approaches are based on a conceptual model of glacier meltwater induced sedimentation in which the minerogenic nonorganic component of the sediments is related to the occurrence of a glacier in the catchment the principal coupling to former glacier activity and elas is common for these approaches however different methods and techniques may complement each other and both possibilities and limitations are demonstrated site selection for reconstructing variations in glacier activity elas is evaluated and critical factors are discussed rerouting of glacier meltwater streams across local watersheds in combination with proglacial sites gives a distinct on off signal for former glacier activity elas together with representative lateral moraines of known age local watersheds are important for calibrating reconstructed glacier activity elas based on a chain of proglacial lakes based on the modern analogue principle various proxies can record whenever glaciers existed in a catchment in a chain of proglacial lakes with different sensitivity to record variations in glacier activity elas these proxies can be calibrated against independent records for one site approaches however variations in glacier activity elas depend on the interpretation and sensitivity of the proxies used

holocene glacier chronologies are high resolution global and inter hemispheric comparisons possible in the context of reconstruction of holocene glacier chronologies there has been a clear tendency during the past few decades towards imprecise use of the term high resolution furthermore it seems to be increasingly assumed that recently developed terrestrial cosmogenic nuclide dating tcnd is replacing earlier dating methods although recent glaciological knowledge clearly reveals the futility of oversimplified global and inter hemispheric correlation on the basis of few key sites such comparisons are widely attempted stimulated by the example of a recently published article relating to the southern alps of new zealand schaefer et al 2009 science 324 622 625 we highlight some related potential problems with the interpretation of holocene glacier chronologies in particular we consider 1 that the term high resolution should be applied only to decadal scale resolution or better and therefore not to tcnd based chronologies 2 that discontinuous moraine chronologies should not be ter

the schmidt hammer as a holocene calibrated age dating technique testing the form of the r value age relationship and defining the predicted age errors most recent developments of schmidt hammer exposure age dating shd as a calibrated age dating tool have been limited by the use of locations at two age control points this has necessitated 1 making assumptions about a linear r value age relationship and 2 basing predictions of age errors only on r value variance at the two age control points this paper analyses 9900 r values obtained from multiple age control points on a sequence of glacio isostatically raised shorelines with well constrained ages skuleskogen high coast world heritage site and environs gulf of bothnia northern sweden ranging from modern to 10 5 ka in age the sampling design involved 30 measurements on granite beach boulders from 30 sites at 11 age control points the r value age relationship is best described by a linear function ordinary least squares ols with an r 2 of 0 89 p 0 0001 predicted age errors are calculated using two approaches 1 ols regression which takes account of the uncertainties associated with the regression line and the age control points and 2 weighted total least squares wtls regression which in addition takes account of possible shoreline age errors and the heteroscedasticity of r value residuals with increasing age with both approaches 95 predicted age errors are relatively modest 355 455 years and 300 515 years respectively with larger r value variance and hence uncertainty for older surfaces and the possibility of further improvement from a more selective field sampling scheme that differentiates between age related and non age related rock surface variability our results also indicate that for certain lithologies and weathering environments it is possible to construct reliable calibrated age curves from relatively few age control points

deglaciation of the eurasian ice sheet complex the eurasian ice sheet complex eisc was the third largest ice mass during the last glacial maximum with a span of over 4500 km and responsible for around 20 m of eustatic sea level lowering whilst recent terrestrial and marine empirical insights have improved understanding of the chronology pattern and rates of retreat of this vast ice sheet a concerted attempt to model the deglaciation of the eisc honouring these new constraints is conspicuously lacking here we apply a first order thermomechanical ice sheet model validated against a diverse suite of empirical data to investigate the retreat of the eisc after 23 ka bp directly extending the work of patton et al 2016 who modelled the build up to its maximum extent retreat of the ice sheet complex was highly asynchronous reflecting contrasting regional sensitivities to climate forcing oceanic influence and internal dynamics most rapid retreat was experienced across the barents sea sector after 17 8 ka bp when this marine based ice sheet disintegrated at a rate of 670 gigatonnes per year gt a 1 through enhanced calving and interior dynamic thinning driven by oceanic atmospheric warming and exacerbated by eustatic sea level rise from 14 9 to 12 9 ka bp the eisc lost on average 750 gt a 1 peaking at rates 3000 gt a 1 roughly equally partitioned between surface melt and dynamic losses and potentially contributing up to 2 5 m to global sea level rise during meltwater pulse 1a independent glacio isostatic modelling constrained by an extensive inventory of relative sea level change corroborates our ice sheet loading history of the barents sea sector subglacial conditions were predominately temperate during deglaciation with over 6000 subglacial lakes predicted along with an extensive subglacial drainage network moreover the maximum eisc and its isostatic footprint had a profound impact on the proglacial hydrological network forming the fleuve manche mega catchment which had an area of 2 5 106 km2 and drained the present day vistula elbe rhine and thames rivers through the seine estuary during the bolling allerod oscillation after c 14 6 ka bp two major proglacial lakes formed in the baltic and white seas buffering meltwater pulses from eastern fennoscandia through to the younger dryas when these massive proglacial freshwater lakes flooded into the north atlantic ocean deglaciation temporarily abated during the younger dryas stadial at 12 9 ka bp when remnant ice across svalbard franz josef land novaya zemlya fennoscandia and scotland experienced a short lived but dynamic re advance the final stage of deglaciation converged on present day ice cover around the scandes mountains and the barents sea by 8 7 ka bp although the phase lagged isostatic recovery still continues today

holocene glacier variations in central jotunheimen southern norway based on distal glaciolacustrine sediment cores abstract sediment cores from two glacier fed lakes are used to reconstruct a continuous record of glacier variations since about 10 000 cal bp in the smorstabbtinden massif of central jotunheimen southern norway particular attention is paid to the century to millennial scale pre little ice age glacial signal based on an estimated temporal resolution of 55 and 25 yr cm 1 for bovertunsvatnet and dalsvatnet respectively visible lithostratigraphic variations organic content loss on ignition calcium carbonate content magnetic susceptibility and grain size fractions especially the fine silt are used as proxy indicators of glacier presence and extent in the lake catchments following deglaciation the early holocene was characterized by generally small glaciers until a major advance the finse event peaking at approximately 8200 cal bp from 7900 to at least 5300 cal bp glaciers appear to have been absent from central jotunheimen there is evidence of glacier expansion between about 2400 and 1600 cal bp the bovertun i event and between about 1400 and 800 cal bp the bovertun ii event before reduced glacier extent during the mediaeval warm period finally the most extensive neoglacial maximum occurred during the little ice age after 500 cal bp in addition to providing a record of the broad pattern of climatically forced holocene glacier variations periodicities at 110 140 200 285 and about 500 yr have been identified uncertainties remain concerning the precise timing of events glacierization and deglacierization detection thresholds a possible mid to late holocene 5300 2500 cal bp neoglacial build up of small glaciers and shorter term decadal to century scale variations in glacier size for which more proximal sites are required

mid to late holocene climate change an overview the last 6000 years are of particular interest to the understanding of the earth system because the boundary conditions of the climate system did not change dramatically in comparison to larger glacial interglacial changes and because abundant detailed regional palaeoclimatic proxy records cover this period we use selected proxy based reconstructions of different climate variables together with state of the art time series of natural forcings orbital variations solar activity variations large tropical volcanic eruptions land cover and greenhouse gases underpinned by results from general circulation models gcms and earth system models of intermediate complexity emics to establish a comprehensive explanatory framework for climate changes from the mid holocene mh to pre industrial time the redistribution of solar energy due to orbital forcing on a millennial timescale was the cause of a progressive southward shift of the northern hemisphere nh summer position of the intertropical convergence zone itcz this was accompanied by a pronounced weakening of the monsoon systems in africa and asia and increasing dryness and desertification on both continents the associated summertime cooling of the nh combined with changing temperature gradients in the world oceans likely led to an increasing amplitude of the el nin o southern oscillation enso and possibly increasingly negative north atlantic oscillation nao indices up to the beginning of the last millennium on decadal to multi century timescales a worldwide coincidence between solar irradiance minima tropical volcanic eruptions and decadal to multi century scale cooling events was not found however reconstructions show that widespread decadal to multi century scale cooling events accompanied by advances of mountain glaciers occurred in the nh e g in scandinavia and the european alps this occurred namely during the little ice age lia between ad w1350 and 1850 when the lower summer insolation in the nh due to orbital forcing coincided with solar activity minima and several strong tropical volcanic eruptions the role of orbital forcing in the nh cooling the southward itcz shift and the desertifi cation of the sahara are supported by numerous model simulations other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics but there is also evidence that changes in the ocean heat transport took place during the lia at high northern latitudes with possible additional implications for climates of the southern hemisphere sh

timing and periodicity of paraglacial rock slope failures in the scottish highlands abstract many formerly glaciated mountains exhibit a high density of postglacial rock slope failures rsfs in the form of rockslides rock avalanches or deep seated gravitational slope deformations such rsfs are often termed paraglacial as they reflect pre conditioning by glaciation and deglaciation the temporal pattern of paraglacial rsfs is unknown we employ 47 cosmogenic isotope exposure ages obtained for 17 catastrophic rsfs in the scottish highlands to test models of changes in rsf frequency since deglaciation our results show that rsf activity spans almost the entire postglacial period from 17 ka until 1 5 ka and that the periodicity of sampled postglacial rsfs is statistically indistinguishable from a pattern of uniform periodicity 1 ka 1 our data do not conform to proposed models of declining rsf frequency with time elapsed since deglaciation but suggest that the temporal distribution of postglacial rsfs is best described by a combination of rapid response enhanced rsf frequency during or immediately after deglaciation followed by approximately constant periodicity our findings are consistent with near surface fracturing of rock when glacially induced confining stresses are removed causing some failures during or immediately after deglaciation and reducing other slopes to critical conditional stability so that failure is triggered by progressive rock mass weakening or by transient triggering mechanisms neither permafrost degradation thaw of ice in joints nor seismic activity offers a general explanation for triggering scottish rsfs but could be contributory in some cases the quasi constant periodicity inferred for holocene rsfs implies that the probability of rsfs in this seismically quiescent intraplate area has not changed in the past 10 ka and that further though infrequent catastrophic rsfs are likely to occur in the future

formation of archean continental lithospheric roots the role of mantle plumes deep lithospheric roots commonly extending to the diamond stability field are distinctive characteristics of archean cratons but their origin remains controversial the 2 7 ga abitibi greenstone belt initially developed in an intraoceanic setting and provides unique insights into the formation of archean continental lithospheric mantle data provided by seismic transects young u pb isotopic ages in the exposed deeper crust of the kapuskasing uplift and anomalous ar ar isotopic ages from lode gold deposits point to a late coupling of the diamondiferous abitibi lithospheric mantle to arc crust these constraints and a lack of archean crust forming events following ca 2650 ma indicate that the thick abitibi cratonic root formed by the diapiric ascent of buoyant residue from which mantle plume derived komatiitic liquids had been extracted although substantial variation may have existed in the development of archean cratonic roots worldwide the evidence from the abitibi belt indicates that all such roots were initiated with the coupling of plume melt residue to greenstone belt crust

enhanced boulder weathering under late lying snowpatches a schmidt test hammer was employed to assess the aggregate surface hardness of samples of boulders dug out from under late lying snowpatches at sites in switzerland scotland and norway the results were compared with an equivalent set of readings made on boulders at nearby snow free control sites the results in every case reveal that the aggregate surface hardness of boulders buried by late lying snow is significantly less at the 0 001 level than that of boulders at the corresponding control sites this result indicates that late lying snow significantly enhances rock weathering probably because boulder and rock surfaces are exposed to prolonged wetting by percolating meltwater under late lying snowbeds

a rock surface microweathering index from schmidt hammer r values and its preliminary application to some common rock types in southern norway an index of the degree of rock surface microweathering based on schmidt hammer r values is developed for use in the field without laboratory testing a series of indices i2 to in where n is the number of successive blows with the hammer is first proposed based on the assumption that the r values derived from successive impacts on the same spot on a weathered rock surface converge on the value characteristic of an unweathered surface of the same lithology of these indices the i5 index which measures the difference between the mean r value derived from first and fifth impacts as a proportion of the mean r value from the fifth impact is regarded as optimal use of fewer impacts e g in an i2 index underestimates the degree of weathering whereas use of more impacts e g in an i10 index makes little difference and is therefore inefficient and may also induce an artificial weakening of the rock field tests of these indices on weathered glacially scoured bedrock outcrops of nine common metamorphic and igneous rock types from southern norway show however that even after ten impacts successive r values fail to approach the values characteristic of unweathered rock surfaces e g bedrock from glacier forelands and road cuttings an improved i5 index is therefore preferred in which the estimated true r value of an unweathered rock surface is substituted weathered rock surfaces exposed to the atmosphere for 10 000 years in southern norway exhibit i5 indices of 36 57 values that reflect a similarly high degree of weathering irrespective of the rock type

reconstruction of holocene glacier history from distal sources glaciofluvial stream bank mires and a glaciolacustrine sediment core near sota saeter breheimen southern norway this study attempts to reconstruct the holocene glacier history of breheimen southern norway from four stream bank mire sites and a downstream lake sediment core near sota saeter based on lithostr

enhanced bedrock weathering in association with late lying snowpatches evidence from livingston island antarctica an indication of the extent of weathering on different aspects of rock outcrops on livingston island antarctica was obtained by means of a schmidt hammer a cone indenter and measurement of weathering rind thickness results show that weathering particularly chemical weathering is enhanced on the lee side of outcrops where snow accumulates as a result of prolonged wetting by the melting snow rock moisture and temperature data indicate that the south facing snow accumulation side of obstacles have high rock moisture levels and maintain relatively high temperatures whilst chemical weathering is greater on the leeward side of outcrops mechanical processes are greater on the windward side the presence of late lying snow thus appears to exert a strong influence on weathering

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

little ice age glacier variations in jotunheimen southern norwvay a study in regionally controlled lichenometric dating of recessional moraines with implications for climate and lichen growth rates a new approach to regional lichenometric dating is developed and applied to little ice age moraine ridge sequences on 16 glacier forelands in jotunheimen southern norway lichenometric dating curves based on the rhizocarpon subgenus are constructed independently for west central and east jotunheimen although there are differences between the subregions a composite regional moraine chronology for jotunheimen identifies 12 episodes of moraine formation in ad 1743 1750 the regional little ice age glacier maximum 1762 1771 1782 1790 1796 1802 1811 1818 1833 1838 1845 1854 1860 1868 1871 1879 1886 1898 1915 1922 and 1927 1934 spatial and temporal patterns in glacier behaviour between the subregions and between jotunheimen and the neighbouring jostedalsbreen are explained in terms of the interaction of annual to decadal variations in summer temperature and winter precipitation glacier advances and moraine formation events driven primarily by winter precipitation variations exhibit subregio

schmidt hammer exposure age dating shd of rock glaciers in the schoderkogel eisenhut area schladminger tauern range austria schmidt hammer rebound values r values enable relative age dating of landforms with r values relating to degree of weathering and therefore length of exposure this method recently termed as schmidt hammer exposure age dating shd was applied to date five rock glaciers size range 0 01 0 12 km2 and one recent rockfall deposit at the study area schoderkogel eisenhut in the schladminger tauern range 14 03 e 47 15 n austria the rock glaciers consist of gneiss or high metamorphic series of mica schist that are comparable in their r values four of them are relict permafrost absent and one is intact containing patches of permafrost on each of the five rock glaciers shd was carried out at 4 6 sites 50 measurements per site along a longitudinal transect from the frontal ridge to the root zone results at all five rock glaciers are generally consistent with each other sharing statistically significant r values along transects the range between the highest and the lowest mean r value at ea

rapid age assessment of glacial landforms in the pyrenees using schmidt hammer exposure dating shed schmidt hammer sh sampling of 54 10 be dated granite surfaces from the pyrenees reveals a clear relationship between exposure and weathering through time n 52 r 2 0 96 p 0 01 and permits the use of the sh as a numerical dating tool to test this10 be sh calibration curve 100 surfaces were sampled from five ice front positions in the tet catchment eastern pyrenees with results verified against independent 10 be and 14 c ages gaussian modelling differentiates holocene 9 4 0 6ka younger dryas 12 6 0 9ka oldest dryas 16 1 0 5ka last glacial maximum lgm 24 8 0 9ka and wurmian maximum ice extent stages mie 40 9 1 1ka these data confirm comparable glacier lengths during the lgm and mie 300m difference in contrast to evidence from the western pyrenees 15km reflecting the relative influence of atlantic and mediterranean climates moreover pyrenean glaciers advanced significantly during the lgm with a local maximum at 25ka driven by growth of the laurentide ice sheet southward advection of the polar front and a solar radiation minimum in the northern hemisphere this calibration curve is available online http shed earth to enable wider application of this method throughout the pyrenees

age constraints of rock glaciers in the southern alps new zealand exploring their palaeoclimatic potential two rock glaciers in the valley head of irishman stream in the central ben ohau range southern alps new zealand have been investigated using the electronic schmidt hammer silverschmidt longitu

comparison of electronic and mechanical schmidt hammers in the context of exposure age dating are q and r values interconvertible application of schmidt hammer exposure age dating shd to landforms has substantially increased in recent years the original mechanical schmidt hammer records r rebound values although the newly introduced electronic schmidt hammer silverschmidt facilitates greatly improved data processing it measures surface hardness differently recording q velocity values that are not a priori interconvertible with r values this study is the first to compare the performance of both instruments in the context of field based exposure age dating with a particular focus on the interconvertibility of r values and q values the study was conducted on glacially polished pyroxene granulite gneiss jotunheimen southern norway results indicate that mean q values are consistently 8 10 units higher than mean r values over the range of values normally encountered in the application of shd to glacial and periglacial landforms a convenient conversion factor of 10 units may therefore be appropriate for all but the softest rock types close to the technical resolution of the instruments the electronic schmidt hammer should therefore be regarded as a useful complement and potential replacement for the mechanical schmidt hammer conversion of published r values data to q values requires however careful control and documentation of instrument calibration copyright 2014 john wiley sons ltd

holocene glacier fluctuations of flatebreen and winter precipitation changes in the jostedalsbreen region western norvay based on glaciolacustrine sediment records the history of holocene glacier variations of flatebreen an independent glacier close to the sw part of the jostedalsbreen ice cap has been reconstructed from lacustrine sediments in the proglacial lake jarbuvatnet the sedimentary succession shows evidence of three maini episodes of holocene glacier expansion the first is recorded in the basal part of the core up to 370 cm according to the age depth relationship in the sediment core based on 12 ams radiocarbon dates this glacier expansion episode terminated about 10200 cal yr bp the second major glacier phase lasted from 8400 to 8100 cal yr bp while the third was initiated around 4000 cal yr bp and has continued up to the present at 43 cm in the core the medium silt content increases significantly accompanied by a minor increase in the sand content this textural change is interpreted as the first time that the tenninus of flatebreen extended inlto an upstream lake at 1083 m a s l the age model suggests that this event took place around