clast shape analysis and clast transport paths in glacial environments a critical review of methods and the role of lithology the reconstruction and tracing of transport paths in glaciated and other environments have a long tradition in the earth sciences we here present a dataset of clast shape samples from a worldwide selection of glaciated mountain environments in order to assess the reliability of this approach overall and the role of lithology on the performance of clast shape measurements in particular our findings demonstrate that the widely used ra c40 co variance approach is applicable to 63 of the 19 catchments investigated while the alternative rwr c40 approach is more widely applicable to 75 of these catchments a systematic assessment of mixing of lithologies at the catchment scale demonstrates that such mixing leads to pronounced overlaps between different control envelopes that had previously been separated thereby removing the discriminatory power of the method mixing of similar lithologies between different catchments shows an even more extreme loss of discriminatory power which strongly suggests that lithology plays a primary role in determining clast shape and that catchment specific processes are superimposed systematic analysis of the dataset also shows that nearly all catchments apart from two can be grouped into two types type i relates to sites in lesser mountain ranges and is characterised by dominantly blocky forms in the subglacial realm highlighting significant reworking processes type ii sites are dominantly in high mountain environments and characterised by a high similarity between subglacial and fluvial control envelopes this indicates that although reworking may be pronounced it is not necessarily effective enough to remove the platy shape that most likely results from extraglacial and supraglacial inputs our study highlights the potential of clast shape analysis as a tool that allows generic processes to be identified between catchments thereby enabling an understanding of debris cascades in glaciated mountain environments we finish with recommendations for ensuring that future clast shape studies are robust reproducible and comparable between different sites

historical glacier fluctuations of jostedalsbreen and folgefonna southern norway reassessed by new pictorial and written evidence glaciers are sensitive indicators of past climate and thus valuable sources of climate history unfortunately direct determinations of glacier changes variations in length and mass balance did not start with increasing accuracy before the end of the nineteenth century therefore historical and geomorphological evidence has to be used to reconstruct glacier variability for preceding time periods here we present new glacier length reconstructions for selected outlet glaciers of jostedalsbreen and folgefonna two ice caps in southern norway a wealth of different historical sources drawings paintings prints photographs maps written accounts about 400 documents allows reconstruction of glacier length variations for the last 300 jostedalsbreen and 200 years folgefonna respectively we present historical material newly collected for briksdalsbreen boyabreen store supphellebreen bergsetbreen nigardsbreen lodalsbreen all jostedalsbreen and bondhusbrea buerbreen both southern folgefon

revised palaeoclimatic significance of mueller glacier moraines southern alps new zealand a sequence of late holocene moraines on the foreland of the mueller glacier southern alps new zealand forms part of a local moraine age database used to establish a regional glacier chronology and subsequently to investigate potential intra hemispheric and global climate forcing mechanisms we present new sedimentological and geomorphological evidence that a set of these moraine ridges previously considered to represent individual advances constitutes a single moraine complex the mueller memorial moraine formed by supraglacial transport of a large volume of landslide debris to the glacier terminus because a moraine formed in this way is not necessarily associated with an advance triggered by a climate event we question the palaeoclimatic significance of the mueller memorial moraine as well as that of other moraines in comparable settings our findings suggest that the mode of formation and glacio dynamical context of moraines whose ages contribute to existing palaeoclimate reconstructions need to be re examined in order to assess the reliability of these reconstructions copyright 2015 john wiley sons ltd

impact of backstop thickness lateral variations on the tectonic architecture of orogens insights from sandbox analogue modeling and application to the pyrenees 1 we performed sandbox analogue models to investigate the influence of along strike tapering of the backstop on the three dimensional architecture of natural doubly vergent thrust fold belts applying the results to a natural example as the pyrenees available geological and geophysical data indicate that the european crust which provided the backstop in the pyrenean orogen has a westward tapering on both the upper westward thickening of the mesozoic cover rocks and the lower westward rising of the moho envelope surfaces accordingly we performed laboratory models characterized by backstops with an along strike tapering of either the upper or the lower surface our results indicate a significant impact of backstop lateral tapering in thrust wedge architecture in terms of the outward propagation of the deformation fronts the width and elevation of the axial zone and the timing of thrust polarity reversal along strike when compared to the pyrenees our results support the inferred westward tapering of the european basement and its commonly accepted backstop role in the pyrenean orogen moreover comparison between the map pattern of the pyrenees and of laboratory experiments suggests that the along strike tapering of the bottom envelope surface of the backstop played a most important role on the three dimensional thrust wedge architecture than the tapering of the upper envelope surface

glacier reconstruction and mass balance modelling as a geomorphic and palaeoclimatic tool the reconstruction of former mountain glaciers has long been used to examine the implications of rapid climate shifts for example at the last glacial interglacial transition and for evaluating asynchronous behaviour of mountain glaciers compared with mid latitude ice sheets during the late quaternary glacier reconstruction has also been used as a source of palaeoclimatic information based on the recognition of empirical relationships between glaciers and climate this paper reviews the application and implications of a recently revised method of glacier reconstruction carr and coleman 2007 based around glaciological principles of mass balance this study examines how this approach can be used to test geomorphological interpretations of former mountain glaciation and also to infer precipitation fields at sites of former glaciation sites of younger dryas niche and icefield glaciation in the british isles demonstrate how this method can verify interpretations of marginal glaciation and begin to understand the different behaviour of outlet glaciers within the same environmental regime examination of a site of former niche glaciation in southern africa demonstrates how glacier reconstruction may be used to infer annual and seasonal precipitation values and strongly supports the idea that winter precipitation in lesotho and se south africa was substantially greater than present day values during the last glacial cycle copyright 2010 john wiley sons ltd

controls on the strength of coupling among climate erosion and deformation in two sided frictional orogenic wedges at steady state 1 many important insights regarding the coupling among climate erosion and tectonics have come from numerical simulations using coupled tectonic and surface process models however analyses to date have left the strength of the coupling between climate and tectonics uncertain and many questions unanswered we present an approximate analytical solution for two sided orogenic wedges obeying a frictional rheology and in a condition of flux steady state that makes explicit the nature and sensitivity of the coupling between climate and deformation we make the simplifying assumption that the wedge grows in a self similar fashion consistent with airy isostasy such that topographic taper is invariant with orogen width tectonic influx rate and climate we illustrate first how and why the form of the erosion rule matters to orogen evolution and then derive a physically based orogen scale erosion rule we show that steady state orogen width crest elevation and crustal thickness are controlled by the ratio of accretionary flux to erosional efficiency to a power dictated by the erosion process remarkably we show that for most combinations of parameters in the erosion law rock uplift rate is more strongly controlled by erosional efficiency than it is by the accretionary flux further assuming frontal accretion with no underplating the spatial distribution of erosional efficiency dictates the relative rock uplift rates on the pro wedge and retro wedge and the time averaged trajectories of rocks through the orogen the restriction to invariant frictional properties is conservative in these respects systems subject to positive feedback between erosion and rheology will exhibit even stronger coupling among climate erosion and deformation than shown here

the morphology structural evolution and significance of push moraines abstract push moraines glaciotectonic ice marginal moraines have a restricted distribution at modern glacier margins and consequently are of potential value in reconstructing pleistocene ice sheets providing data both on former glaciodynamics and on the palaeoenvironment of the glacial foreland to the wider earth science community push moraines are of interest as analogues for thin skin tectonics within orogenic belts this paper reviews the morphology structural geology formation and significance of push moraines the morphological and structural characteristics of small seasonal push moraines through to large multi crested examples produced by sustained glacier advances are reported before the primary controls on push moraine formation are examined these controls include the nature of the applied glacial stress field the presence and properties of decollement horizons and the shear strength and rheology of the glacial foreland a conceptual model of push moraine formation is introduced in which the range of observed morphological and structural forms are viewed within a matrix defined by the main variables which control their formation the absence of consensus over which of these variables is of greatest importance currently limits the significance of push moraines in palaeoglaciological research as a consequence this review emphasises the need for future research in order to realise the true potential of push moraine in the reconstruction of pleistocene environments

early holocene glacier fluctuations in krundalen south central norway palaeoglacier dynamics and palaeoclimate krundalen a valley occupied by three eastern outlet glaciers of the jostedalsbre ice cap contains three groups of moraines two of which are outside the dated neoglacial little ice age lia l

frontal accretion an internal clock for bivergent wedge deformation and surface uplift 1 we propose a conceptual model of frontal accretion within bivergent wedges which is based on two dimensional sandbox simulations and the analysis of particle displacement fields each frontal accretion cycle consists of a thrust initiation an underthrusting phase and a reactivation phase the location and magnitude of deformation within a bivergent wedge and its associated surface uplift vary systematically with the phase of the frontal accretion cycle and are thus predictable therefore the frontal accretion cycle can be considered as an internal clock for wedge scaled deformation and surface uplift we further demonstrate that the geometry of the deformation front and the spatial distribution of surface uplift can be used to infer the currently active phase within a frontal accretion cycle surface uplift of the axial zone and the retrowedge may reach up to half of the thickness of the incoming sedimentary layer during a frontal accretion cycle we estimate cycle duration to range between 104 and 105 years which is thus similar to the time frame of climatic cycles the proposed conceptual model provides an explanation for the commonly observed transience of deformation and surface uplift and for the discrepancy between geodetic paleoseismologic and geologic estimates of fault slip

development of minor outwash fans at kotlujokull iceland throughout the 1980s the development of minor outwash fans was studied at and beyond a northeastern section of the steep advancing ice front of kotlujokull the largest outlet glacier on the east side of the ice cap myrdalsjokull in central south iceland in contrast to the extensive outwash fans of gravelly and stony material deposited by high energy streams from underneath the glacier the minor fans consist of fine grained material mainly of sand size deposited by low energy streams draining the debris covered glacier surface the vertical alteration in texture of the minor fan deposits results from changing influx of sediments which in turn is coupled to varying activity in the processes working in the supraglacial sediment source area these processes are ablation sudden drainage of pockets of water influx of rainwater and resedimentation of debris by fall slide and flow along with the glacier advance during the 1980s slabs of fan sediments were incorporated in the push moraine ridge being formed the subsequent glacier retreat during the 1990s has largely curtailed the production of minor outwash fans it is concluded that this type of outwash fan is likely to be produced along advancing or stationary glaciers where the frontal slope is steep and covered by debris similar minor outwash fans termed hochsander fans have been identified beyond ice marginal moraine ridges bounding dead ice morainic terrain in pleistocene landscapes

characteristics of recessional moraines at a temperate glacier in se iceland insights into patterns rates and drivers of glacier retreat icelandic glaciers are sensitive to climate variability on short term timescales owing to their north atlantic maritime setting and have been undergoing ice marginal retreat since the mid 1990s recent patterns rates and drivers of ice frontal retreat at skalafellsjokull se iceland are examined using small scale recessional moraines as a geomorphological proxy these small scale recessional moraines exhibit distinctive sawtooth planform geometries and are constructed by a range of genetic processes associated with minor ice margin re advance including i combined push squeeze mechanisms ii bulldozing of pre existing proglacial material and iii submarginal freeze on remote sensing investigations and lichenometric dating highlight sequences of annually formed recessional moraines on the northern and central parts of the foreland conversely moraines are forming on a sub annual timescale at the southeastern skalafellsjokull margin using annual moraine spacing as a proxy for annual ice margin retreat rates imrrs we demonstrate that prominent periods of glacier retreat at skalafellsjokull are coincident with those at other icelandic outlet glaciers as well as those identified at greenlandic outlet glaciers analysis of imrrs and climate data suggests summer air temperature sea surface temperature and the north atlantic oscillation have an influence on imrrs at skalafellsjokull with the glacier appearing to be most sensitive to summer air temperature on the basis of further climate data analyses we hypothesise that sea surface temperature may drive air temperature changes in the north atlantic region which in turn forces imrrs the increase in sea surface temperature over recent decades may link to atmospheric driven variations in north atlantic subpolar gyre dynamics

the genesis and significance of hummocky moraine evidence from the isle of skye scotland abstract the range of genetic and climatic interpretations of scottish hummocky moraine is reviewed and new data are presented from the isle of skye western scotland which are used as the basis of a genetic classification hummocky moraine on skye is shown to consist of three principal sediment landform associations 1 recessional moraines 2 chaotic ice stagnation moraines and 3 drumlins and fluted moraines the recessional moraines consist of transverse moraine ridges and chains of mounds and were formed by a combination of glaciotectonics and debris accumulation at active ice margins second chaotic moraines consist of randomly distributed hummocks mounds and rim ridges and record deposition in contact with inactive ice finally drumlins and fluted moraines are longitudinally oriented subglacial bedforms formed by a combination of lodgement and sediment deformation individual occurrences of hummocky moraine may comprise one two or all of these associations the detailed study and differentiation of scottish hummocky moraine provides a valuable source of information on former glacier dynamics and landscape change

origin chronology and climatological significance of annual moraine ridges at myrdalsjokull iceland minor transverse moraine ridges have formed annually at the retreating north margin of myrdalsjokull 550 600 m a s l in south iceland during the period 1928 1981 they are composed of slabs of clast paved lodgement till and their formation at the glacier edge results from subglacial freezing on of sediment slabs during winter and the annual cycle of ice front activity this type of annual moraine ridge is likely to be characteristic of retreating temperate glaciers where the glacier toe is thin and winters are cold the speed of glacier retreat is finely balanced with changes in mean summer temperature suggesting that the short term ice front fluctuations are climatically induced and not a result of surge activity

glacier fluctuations equilibrium line altitudes and palaeoclimate in lyngen northern norway during the lateglacial and holocene based on lacustrine and morpho stratigraphical evidence from lyngen in troms northern norway 13 marginal moraines have been mapped in front of lenangsbreene in strupskardet moraines m1 m13 are inferred to represent glacier halts or advance readvance taking place during the lateglacial and holocene the presence of collapse depressions suggests that some of them were ice cored m1 m3 a chronological framework taking into account a combination of former shorelines and related glacier meltwater channels lichenometry and ams radiocarbon dated lacustrine sediments spanning the last 20 000 cal yr bp has been established the distal glacier fed lake aspvatnet was isolated from the sea c 10 300 cal yr bp and the lacustrine sediments have been investigated by use of loss on ignition loi magnetic susceptibility water content wet and dry bulk density dbd and the magnetic parameters anhysteretic remanent magnetization arm and saturation remanent magnetization sirm there is in general good agr

the sedimentary signature of ice contact sedimentation and deformation at macro and micro scale a case study from nw scotland abstract studies on the genesis of subaerial debris flows and associated deposits are relatively rare in the literature especially in an ice marginal context of moraine formation the present contribution reports results from both the macro and micro scales of a subaerial depositional setting in order to contribute to closing this gap at the macroscale alternating loose stratified clast and matrix supported diamicts and finely laminated sand units indicate deposition of debris flows and fluvial units in a subaerial ice marginal setting that were stacked up to form a terrestrial ice contact fan macroscale and micromorphological analyses show that this fan displays evidence of a three phased formation a overriding and glaciotectonisation of pre existing sediments followed by retreat and burial of this core by b ice contact fan deposition dominated by water rich fluvial deposition with relatively little debris flow activity and c a switch to a gravitational sedimentation style with dominantly debris flow deposition and fewer and thinner fluvial units thin sections of both the diamict and laminated sand units show evidence of deposition of a mud and fine sand rich slurry being expelled from the tops of advancing mass flows water rich fine grained slurries appear to have been progressively overridden and deformed in response to ductile shear occurring at the base of individual flows liquefaction and remobilisation of sand within laminated deposits occurred during such basal shear events resulting in the injection of liquefied sediments into variably deformed laminated sands and clays deformation is more likely to have taken place through internal movement of the sediment due to changing porewater conditions and loading upon emplacement our approach confirms previous results that highlight the possibilities of increasing the accuracy of sedimentological investigations through combined sedimentological analyses at varying scales

alpine younger dryas glaciers as palaeo precipitation gauges moraines of the younger dryas egesen stadial which are widespread features in the alps are a valuable terrestrial data source for quantitative palaeoclimatic studies the depression of the early younger dryas egesen i ela shows a distinct spatial pattern it was highest ca 450 500 m against present day in those areas which are exposed towards the west and northwest in the central more shielded valleys it was in the order of 300 m and less summer temperature depression which can be derived from the younger dryas timberline depression is in the order of 3 5 k the stochastic glacier climate model by ohmura and others 1992 which relates summer temperature and precipitation at the ela is used to infer precipitation change results are compared with those obtained from the glacial meteorological approach by kuhn 1981a both models lead to highly similar results during the early younger dryas climate in the central valleys of the alps seems to have been considerably drier than today in those areas which are open to the west and northwest precipitation seems to have been the same as today or even slightly higher these results which are based on a rather dense network of data points agree well with the results from permafrost climate studies and the more qualitative information from palaeobotanical research they also support the results from atmospheric general circulation models for the younger dryas in europe which point towards a more zonal type of circulation

push moraines and glacier contact fans in marine and terrestrial environments the local climatic regime and the mass balance state are important determinants of the dynamics of terrestrial and marine glacier fronts which in turn determine the sediments and landforms produced at the glacier front many modern glaciers undergoing overall retreat in areas of maritime climate produce winter push moraines during a late winter readvance followed by a summer retreat whilst in more continental regions no significant winter readvance occurs and annual push moraines are absent the frontal dynamics which lead to these changes are analysed and the form structure sequence and field relations of both terrestrial and marine push moraines are described from iceland spitsbergen and baffin island long term changes in mass balance leading to major glacier advances or readvances also generate large push moraines in terrestrial environments push moraine formation is accompanied by uplift rejuvenation and down cutting of outwash systems whose sediments become closely associated with glaciotectonic structures which permit pre syn and post tectonic sequences to be identified the development of ice marginal fan moraine complexes is modelled as a function of the relative magnitude of two parameters the velocity of ice movement and the calving rate a high ice velocity just exceeded by the calving rate gives closely spaced push moraines and confluent ice marginal fans a high velocity far exceeded by the calving rate produces closely spaced moraines but separate ice marginal fans a low ice velocity in combination with a high calving rate results in well separated and feebly developed push moraines while a low ice velocity and a low calving rate produces feeble push moraines and coalescent fans

lateglacial and early holocene glacier stages new dating evidence from the meiental in central switzerland abstract in order to improve our understanding of the glacier development in central switzerland after the last glacial maximum lgm we have investigated moraine sequences of the meiental meien valley after detailed field mapping 34 rock samples from different moraines were dated with cosmogenic 10be the results indicate that the investigated moraines were deposited mainly in multi phased advances during the younger dryas and the early holocene this is in contrast to previous studies suggesting that these moraines represent equivalents of the older egesen and daun stadials our research shows that factors like the moraine stratigraphy geomorphologic characteristics and equilibrium line altitudes elas can be highly variable at the local scale which can make a stadial correlation of moraines between different valleys or regions within the alps without age constraints ambiguous and unreliable against this background the interregional use of elas ela depressions for the parallelization of paleo glacier extents throughout the alps according to traditional concepts of the lateglacial deglaciation seems to produce erroneous results geomorphologic observations and relative age relationships in moraine successions based on stratigraphic principles remain the basis for this kind of studies but as we show here it is necessary to base local to regional comparisons of moraine sequences additionally on exposure ages to gain a more reliable understanding of the alpine glacier development after the lgm

chironomids as a tool for inferring holocene climate an assessment based on six sites in southern scandinavia abstract chironomid subfossil assemblages from six low alpine and sub alpine holocene stratigraphies are presented and compared they are from five lakes in mid southern and western norway and one in central sweden when comparing the chironomid inferred july air temperatures there are many time segments with a poor among lake fit in inferred temperatures possible environmental variables influencing the fossil chironomid assemblages are discussed using a modern norwegian calibration data set to indicate taxon environment relationships these analyses indicate that local changes in ph water chemistry and productivity at times may have overridden the regional temperature signal in addition other causes of poor among site temperature fit are discussed in particular those related to chronological uncertainties holocene temperature inferences from single cores based on chironomids may not always be able to provide a reliable regional temperature signal but can act as a guide from which hypotheses about past environmental conditions can be tested with the aid of chironomid inferred temperatures from several sites and from other environmental proxies we have obtained a regional picture of holocene summer temperature change by developing a consensus reconstruction based on the overall temperature signal from all six sites this consensus is developed by fitting a smoother through all 330 site specific temperature deviations from the holocene mean the consensus temperature deviations vary from 0 8 c at 8800 cal years bp to 0 8 c at 6500 cal years bp

younger dryas glacial landsystems in north west scotland an assessment of modern analogues and palaeoclimatic implications abstract by explicitly linking process to form landsystem models developed in modern environments provide powerful tools for the reconstruction of past environments from the sedimentological and geomorphological record some landform characteristics however may originate by more than one process equifinality so although a particular depositional model may fit the data it is not necessarily the correct one here we critically examine the use of modern analogues to interpret glacial landforms focusing on hummocky moraine a distinctive landform association consisting of numerous sharp crested moraine mounds and ridge fragments which occurs on many valley floors in upland britain detailed studies of examples of younger dryas age in the north west highlands of scotland show that they represent ice contact fans which have been affected to varying degrees by ice push and subglacial deformation and that they formed at active oscillating ice margins the sedimentological data are inconsistent with an origin by englacial thrusting as has been proposed for similar moraines elsewhere in upland britain on the basis of morphological criteria comparison with modern glacial landsystems shows that although aspects of hummocky moraines in the study area have close modern counterparts none provides an exact analogue in all respects this may reflect the distinctive climate of western scotland during the younger dryas estimates of mean july temperatures in the younger dryas in scotland based on chironomid assemblages are c 8 c at sea level when combined with reconstructed equilibrium line altitudes for contemporaneous glaciers these estimates indicate mean annual precipitation totals in the range of 2358 337 mm yr 1 at sea level in nw scotland c 26 higher than present day values the implied heavy snowfall suggests that glaciers in western scotland during the younger dryas were of high activity type unlike modern glaciers in svalbard for example high glacier velocities and high winter precipitation would suppress permafrost development despite low mean annual temperatures the climatic environment also favoured rapid oscillations of glacier margins during both glacier build up and retreat phases climatic factors combined with the availability of large quantities of subglacial debris led to the development of distinctive glacial landsystems which may have no direct modern analogue

subglacial water escape structures and till structures slettjokull iceland beyond slettjokull the north part of the ice cap m rdalsjokull south iceland an undulating till plain is dissected by meltwater streams throughout a transect from the ice margin to the 1900 ice marginal moraine a distance of about 1 2 km finely laminated wedge shaped water escape structures wes are present originating in the till and disappearing down ice into the underlying sands and fine gravels a second set of much smaller and deformed black wes occurring within the till has been produced by upward injection into the till as a response to stiffening of the till after dewatering by the downward developing wes at present the toe of the glacier is frozen to its bed and the frozen bed material is more than 2 m thick during the relatively cold period around the turn of the century and until the late 1920s a similar submarginal body of permafrost must have existed the sequence reveals that subglacial meltwater attributed to drainage following the 1918 katla eruption was blocked by a frozen glacier toe causing the formation of water escape structures subsequently glacier flow deformed the substratum and produced the threefold division of the till bed the study has important implications for theories envisaging subglacial floods because it demonstrates that it is very difficult for temperate glaciers with a temporary frozen bed in the toe region to retain subglacial meltwater copyright 1999 john wiley sons ltd

episodic folding inferred from syntectonic carbonate sedimentation the santaren anticline bahamas foreland abstract sedimentation coeval with growth of the santaren anticline provides an excellent opportunity to study the relationships between sedimentation and anticline uplift through time the santaren anticline is a kilometre scale nw se trending fold offshore of cuba in the bahamas foreland of the cuban fold and thrust belt the growth strata associated with this anticline consist of a thick package of carbonate sediments that were deposited without major interruptions from neogene and perhaps before to present day the excellent seismic resolution and age control of a number of seismic horizons within the growth strata allowed us to define 25 growth beds each of them representing between 0 1 and 3 2 ma an analysis of the thickness of these beds allowed us to determine accurate quantitative values of cumulative decompacted thickness and crestal structural relief at the time of their deposition in addition for the same periods sedimentation and fold uplift rates were calculated moreover some information on relationships between sedimentation and fold uplift rates was inferred from the growth stratal geometry growth beds that overlap the fold crest and thin over it indicate that sedimentation rates outpaced fold growth rates during their deposition some overlapping beds have constant thickness indicating that no fold uplift occurred during their sedimentation the rest of the growth beds exhibit onlap offlap geometries that do not indicate a unique sedimentation fold uplift rate relationship only in those cases in which the geometry of the underlying bed at the end of its deposition is known is it possible to infer a specific sedimentation fold uplift rate relationship as a result of this analysis we have been able to 1 illustrate that the geometry of the growth strata associated with the santaren anticline results from competition between sedimentation and tectonic fold uplift 2 document the episodic and non steady nature of fold growth and 3 show that short term rates at the scale of hundreds of thousands years provide much insight into the interplay between sedimentation and tectonic fold uplift that control the growth stratal patterns

a spatially restricted younger dryas plateau icefield in the gaick scotland reconstruction and palaeoclimatic implications considerable research has been conducted in scotland to reconstruct younger dryas glaciers and palaeoclimatic conditions but our understanding remains incomplete in this contribution we examine the gaick a dissected plateau that extends over 520 km 2 in the central grampians scotland the extent and style of younger dryas glaciation in the gaick has been repeatedly contested although a model of extensive plateau icefield glaciation has become generally accepted this is despite well documented issues with key elements of the plateau icefield reconstruction we synthesise the results of recent geomorphological mapping in the gaick and recognise a distinct morphostratigraphic signature in the upper parts of the western catchments this differs markedly from sediment landform associations in other parts of the area and we argue this provides a strong indication of spatially restricted younger dryas 12 9 11 7 ka glaciation in the gaick our interpretation is independently supported by glacierisation threshold analysis which implies that the eastern gaick was unable to nourish younger dryas ice we therefore contest the accepted paradigm of extensive younger dryas glaciation in this area based on the geomorphological evidence and glacier surface profile modelling we reconstruct a 42 km 2 plateau icefield that yields an equilibrium line altitude of 751 46 m using this value a sea level precipitation value of 826 331 mm a 1 is inferred for the younger dryas which suggests considerably drier conditions than at present using recalculated glacier derived precipitation estimates from scotland we present regional climate analysis that corroborates arguments for a strong west east precipitation gradient across scotland

exhumation history of the southern altiplano plateau southern bolivia constrained by apatite fission track thermochronology 1 although the structural geometry of the cenozoic altiplano puna plateau in the central andes is well defined the temporal evolution of this contractile deformation is poorly constrained to address this shortcoming we used apatite fission track thermochronology aft to quantify the cooling and exhumation history along a transect at 21 s in southern bolivia through the deformed intermontane altiplano basin the doubly vergent thrust belt of the eastern cordillera and the inner foreland thrust belt east of the plateau interandean zone thermal history modeling combined with published balanced cross sections and stratigraphic data constrain exhumation histories exhumation started during the late eocene 40 36 ma in the central eastern cordillera possibly due to bivergent thrusting and cretaceous rift structure inversion during the early oligocene 33 27 ma exhumation spread across the study area as the current boundary thrusts of the eastern cordillera were activated the inner west vergent thrust system became active in irregular order until circa 20 ma whereas the east vergent interandean thrust belt formed by eastward propagating deformation since circa 30 ma plateau exhumation continued at 0 2 mm yr until shortening terminated by 11 7 ma shortening within the plateau since circa 30 ma did not evolve by lateral accretion of thrust wedges the propagating deformation style is spatially confined to the foreland thrust belt which initiated coeval to plateau deformation interandean zone but propagated mainly after circa 10 ma subandean zone early oligocene plateau wide tectonically driven exhumation suggests that subduction related processes had already thermally weakened the continental lithosphere prior to the 27 25 ma onset of volcanic activity

multiple origins of large hummock deposits in alai valley northern pamir implications for palaeoclimate reconstructions abstract this paper interprets the origin of several of the largest hummocky landform assemblages in the alai valley northern pamir a formerly glaciated intermontane depression the vast hummocky deposits in the koman suu and achik tash river catchments are found to be of two contrasting modes of formation glacial hummocks deposited during koman and lenin glaciers withdraw and avalanche hummocks produced during catastrophic koman and lenin rock avalanches the origins of the deposits we assessed through remote and field based geomorphological mapping as well as sedimentological investigations which included clast analysis and the identification of micro scale agglomerates indicative of rock avalanche emplacement both the koman and lenin rock avalanches were large catastrophic events with run outs of 34 and 24 km respectively and a volume over 1 109 m3 each that occurred subsequent to glacier withdrawal from the area the complex conditions on the moment of the rock avalanche emplacement promoted unusual deposits geomorphology and extensive run outs the landslide landforms formed over the pre existing glacial hummocks and fluvial deposits and are geomorphologically and sedimentologically distinct from the larger glacial hummocks the reconstruction of this sequence of events has implications for how hummock dating should be interpreted this research illustrates large scale catastrophic landsliding in the glacial environment and adds to the ongoing debate about the misidentification of rock avalanche deposits as of glacial origin and their relevance to palaeoclimatological and palaeoseismological reconstructions

topographic controls on plateau icefield recession insights from the younger dryas monadhliath icefield scotland plateau icefields are a common form of mountain ice mass frequently found in mid latitude to high arctic regions and increasingly recognized in the quaternary record their top heavy hypsometry makes them highly sensitive to changes in climate when the equilibriaum line altitude ela lies above the plateau edge allowing ice to expand significantly as regional elas decrease and causing rapid recession as climate warms with respect to future climate warming it is important to understand the controls on plateau icefield response to climate change in order to better predict recession rates with implications for water resources and sea level rise improving knowledge of the controls on glacier recession may also enable further palaeoclimatic information to be extracted from the quaternary glacial record we use the distribution of moraines to examine topographic controls on younger dryas icefield recession in scotland we find that overall valley morphology influences the style of recession through microclimatic and geometric controls with bed gradient affecting moraine spacing ice mass reconfiguration may occur as recession progresses because ice divide migration could alter the expected response based on hypsometric distribution these results add to a growing body of research examining controls on glacier recession and offer a step towards unravelling non linear ice mass behaviour less

erosion and tectonics at the margins of continental plateaus the topography across the eastern margin of the central andean plateau north of 18 s beni region bears a strong resemblance to the topography of the southern margin of the tibetan plateau nepal himalaya with both regions featuring a steep frontal slope and high peaks at the plateau edge in contrast the topography of the eastern margin of the central andean plateau south of 18 s pilcomayo region tapers toward the foreland more gently and has no line of high peaks at the margin both the himalayan and the beni regions have been the sites for large amounts of denudation and in both regions geologic evidence suggests that erosion has been sufficiently vigorous for the physiographic plateau margin to have retreated toward the plateau interior during the neogene we hypothesize that the steep frontal slope and high peaks of the beni region and himalayan front largely reflect the high orographic precipitation and high erosion rates occurring in these regions and that the more gentle topography of the semiarid pilcomayo region reflects a tectonic landform only slightly modified by erosion we propose that orographic precipitation impinging on a plateau margin will generally tend to drop moisture low on the slope eroding back the plateau while enhancing or maintaining the steep long wavelength slope a numerical model coupling orographic precipitation erosion and tectonic uplift demonstrates the plausibility of this hypothesis the erosional efflux in both the beni and nepal himalaya have been considerable and simple mass balance calculations for the himalaya suggest that during the neogene the erosional mass efflux has generally outpaced the tectonic mass influx this contrasts with the apparent prior domination of tectonic influx and may reflect a decrease in the rate of tectonic addition during the same period and or increased late cenozoic erosion rates

the loch lomond readvance on the isle of mull scotland glacier reconstruction and palaeoclimatic implications geomorphological mapping of mull provides evidence for an icefield 143 km2 in area flanked by six corrie glaciers with a total area of ca 13 km2 the absence of lateglacial periglacial features shorelines and pollen sites from the area occupied by this readvance together with radiocarbon dating of shell fragments confirm that it occurred during the loch lomond younger dryas stade the thickness of glacigenic deposits within the area of the readvance is attributed to reworking of paraglacial sediments up valley continuity of recessional moraines indicates that the ice remained active and near to equilibrium during retreat consistent with slow warming following the coldest part of the stade reconstructed equilibrium line altitudes elas imply vigorous snow blowing by westerly winds and are consistent with a general southwestwards decline in elas across the scottish highlands an ela of 250 m was calculated for the mull icefield using an ablation accumulation balance ratio abr approach palaeotemperature and palaeoprecipitation estimates were derived by calculating a theoretical regional ela from meteorological data and assuming that the combination of temperature and precipitation implied by the theoretical ela approximates conditions at 250 m on mull during the loch lomond stade the result indicates a mean july sea level temperature of 5 7 0 5 c and a mean annual precipitation at 250 m of ca 2700 3800 mm best estimate 3200 mm indicating higher precipitation totals than at present owing to more vigorous atmospheric circulation copyright 2002 john wiley sons ltd

glacial geomorphological mapping a review of approaches and frameworks for best practice geomorphological mapping is a well established method for examining earth surface processes and landscape evolution in a range of environmental contexts in glacial research it provides crucial data for a wide range of process oriented studies and palaeoglaciological reconstructions in the latter case providing an essential geomorphological framework for establishing glacial chronologies in recent decades there have been significant developments in remote sensing and geographical information systems gis with a plethora of high quality remotely sensed datasets now often freely available most recently the emergence of unmanned aerial vehicle uav technology has allowed sub decimetre scale aerial images and digital elevation models dems to be obtained traditional field mapping methods still have an important role in glacial geomorphology particularly in cirque glacier valley glacier and icefield ice cap outlet settings field mapping is also used in ice sheet settings but often takes the form of necessarily highly selective ground truthing of remote mapping given the increasing abundance of datasets and methods available for mapping effective approaches are necessary to enable assimilation of data and ensure robustness this paper provides a review and assessment of the various glacial geomorphological methods and datasets currently available with a focus on their applicability in particular glacial settings we distinguish two overarching work streams that recognise the different approaches typically used in mapping landforms produced by ice masses of different sizes i mapping of ice sheet geomorphological imprints using a combined remote sensing approach with some field checking where feasible and ii mapping of alpine and plateau style ice mass cirque glacier valley glacier icefield and ice cap geomorphological imprints using remote sensing and considerable field mapping key challenges to accurate and robust geomorphological mapping are highlighted often necessitating compromises and pragmatic solutions the importance of combining multiple datasets and or mapping approaches is emphasised akin to multi proxy approaches used in many earth science disciplines based on our review we provide idealised frameworks and general recommendations to ensure best practice in future studies and aid in accuracy assessment comparison and integration of geomorphological data these will be of particular value where geomorphological data are incorporated in large compilations and subsequently used for palaeoglaciological reconstructions finally we stress that robust interpretations of glacial landforms and landscapes invariably requires additional chronological and or sedimentological evidence and that such data should ideally be collected as part of a holistic assessment of the overall glacier system

assessing vertical axis rotations in large magnitude extensional settings a transect across the death valley extended terrane california models for neogene crustal deformation in the central death valley extended terrane southeastern california differ markedly in their estimates of upper crustal extension versus shear translations documentation of vertical axis rotations of range scale crustal blocks or parts thereof is critical when attempting to reconstruct this highly extended region to better define the magnitude aerial extent and timing of vertical axis rotation that could mark shear translation of the crust in this area paleomagnetic data were obtained from tertiary igneous and remagnetized paleozoic carbonate rocks along a roughly east west traverse parallel to about 36 n latitude sites were established in 7 to 5 ma volcanic sequences greenwater canyon and brown s peak and the 10 ma chocolate sundae mountain granite in the greenwater range 8 5 to 7 5 ma and 5 to 4 ma basalts on the east flank of the black mountains the 10 6 ma little chief stock and upper miocene basalts in the eastern panamint mountains and paleozoic pogonip group carbonate strata in the north central panamint mountains at the site level most materials yield readily interpretable paleomagnetic data group mean directions after appropriate structural corrections suggest no major vertical axis rotation of the greenwater range e g d 359 i 46 95 8 0 n 12 7 normal n 5 reversed r polarity sites little post 5 ma rotation of the eastern black mountains e g d 006 i 61 95 4 0 n 9 n 6 r sites and no significant post 10 ma rotation of the panamint range e g d 181 i 51 95 6 5 n 9 r sites in situ data from the greenwater canyon volcanic rocks chocolate sundae mountain granite funeral peak basalt rocks the little chief stock and paleozoic carbonate rocks remagnetized are consistent with moderate south east side down tilting of the separate range blocks during northwest directed extension the paleomagnetic data reported here suggest that the panamints shared none of the 7 ma to recent clockwise rotation of the black mountains crystalline core as proposed in recent models for transtensional development of the central death valley extended terrane

sedimentary successions in ice marginal fans of the late saalian glaciation southwestern poland abstract the late saalian end moraines of southwestern poland contain several features that may be attributed to the formation that is predominantly controlled by the deposition of sorted waterlaid sediments these hills are essentially small alluvial fans with ice contact facies they have a semi conical form plano convex geometry their distal slopes are up to 5 and proximal slopes are between 5 and 20 the sedimentary sequences contain two units the lower unit comprises coarse grained material of gravel bed sheetflow facies and gravel bed channel facies with subordinate high energy channel flow facies and boulders up to 1 8 m in diameter the upper unit contains sand bed sheetflow facies and sand bed channel facies the sediment bedding is usually conformable with and parallel to the inclined fan surface these sequences represent typical proximal distal fan facies associations with a high energy and pulsatory water discharge in the proximal zone the fans in spite of their formation in the proglacial zone have geomorphological features and sedimentary sequences that are very similar to present day fans and are equivalent to sheetflow dominated or humid alluvial fans in non glacial environments

steady state erosion of critical coulomb wedges with applications to taiwan and the himalaya 1 orogenic structure appears to be partially controlled by the addition to and removal of material from the mountain belt by tectonic accretion and geomorphic erosion respectively we developed a coupled erosion deformation model for orogenic wedges that are in erosional steady state and deform at their coulomb failure limit erosional steady state is reached when all material introduced into the wedge is removed by erosion that is limited by the rate at which rivers erode through bedrock we found that the ultimate form of a wedge is controlled by the wedge mechanical properties sole out depth of the basal decollement erosional exponents basin geometry and the ratio of the added material flux to the erosional constant as this latter ratio is increased wedge width and surface slopes increase we applied these models to the taiwan and himalayan orogenic wedges and found that despite a higher flux of material entering the former the inferred ratio was larger for the latter calculated values for the erodibility of each wedge showed at least an order of magnitude lower value for the himalaya relative to taiwan these values are consistent with the lower precipitation regime in the himalaya relative to taiwan and the exposure of crystalline rocks within the himalayan orogenic wedge independently determined rock erodibility estimates are consistent with the accretionary wedge sediments and metasediments and the crystalline and high grade metamorphic rocks exposed within taiwan and the himalaya respectively therefore differences in rock type and climate apparently lead to key differences in the erosion and hence orogenic structure of these two mountain belts

three dimensional numerical models with varied material properties and erosion rates implications for the mechanics and kinematics of compressive wedges received 19 march 2008 revised 29 january 2009 accepted 13 february 2009 published 21 april 2009 1 we develop three dimensional mechanical models of a compressive wedge and investigate how the form and kinematics of the outboard wedge are affected by variation in initial topography material properties and erosion rate inclusion into the wedge of weaker less dense material affects the form of the wedge producing a region of steeper average slopes and higher topography while depriving the region further inboard of material enhanced erosion has a similar effect the wedge attempts to replace the eroded material by focusing deformation the result is a stepped region of lower topography within the outboard of the orogen we observe that uplift velocities at three points in the orogen vary cyclically from near zero to 3 times the average uplift rate over cycles lasting on the order of 15 200 000 model years our models along with analog models and some well dated examples from active orogens suggest that transient accommodation of strain may be common the cycles observed responded rapidly to changes in the amount of erosion imposed our models suggest that orogens may be driven by strong coupling between erosion and strain on temporal scales of 10 4 10 5 years and spatial scales comparable to the scale of the erosional perturbation we compare our models to the puli embayment of west central taiwan a region of anomalous low topography and suggest that it presence may reflect the presence of weaker and more erodible sediments than those present along strike in the orogen

reconstruction of a lateglacial younger dryas mountain ice field in sutherland northwestern scotland and its palaeoclimatic implications quaternary geomorphological and geological mapping of a large area 1800 km2 in the northwestern scottish highlands has led to the reconstruction of a coherent mountain ice field approximately 45 km long and 30 km wide at its maximum extent this west sutherland ice field covered an area of 350 km2 and had a mean equilibrium line altitude of 334 m assuming that the outlet glaciers all reached their maxima simultaneously numerical dating strongly suggests a younger dryas 12 9 11 7 ka age of the mapped limits of this mountain ice field this study also shows that the area of northwestern scotland covered by younger dryas glaciers was five times larger than previously thought palaeo temperature estimates obtained from chironomid and beetle assemblages elsewhere have been used to reconstruct palaeo precipitation during the younger dryas for west sutherland using a previously published global empirical dataset annual precipitation of 2344 248 mm a 1 at sea level is inferred from our new palaeo glacier reconstruction suggesting slightly wetter conditions compared to the present day these figures are in good agreement with those reconstructed for other parts of the scottish highlands and islands and this may indicate a marked w e palaeo precipitation gradient during the younger dryas this paper goes on to discuss the wider validity of palaeo climatic reconstructions from inferred palaeo glacier geometries and presents a number of possible scottish lateglacial climate scenarios which warrant further testing copyright 2010 john wiley sons ltd

genesis stability and preservation potential of large lateral moraines of alpine valley glaciers towards a unifying theory based on findelengletscher switzerland abstract lateral moraines are prominent features of glaciated landscapes in high mountain environments and key landforms in glacier and palaeoclimatic reconstructions yet compared to smaller moraines they have been little studied and several aspects are not well understood we here present detailed sedimentological results from the lateral moraines of findelengletscher in sw switzerland to gain new insights into the formation of these landforms the lateral moraines studied here stand up to 140 m above the valley floor are over 3 km long and strongly asymmetrical in cross profile with distal slopes between 29 and 36 and proximal slopes that are commonly 41 64 but locally reach angles of up to 80 recorded lithofacies comprise loose clast and matrix supported stratified diamicts and intercalated sorted sediments in the distal slopes and near the crestline overconsolidated matrix supported massive and weakly stratified diamicts and streaked out sorted sediment lenses in the core and proximal slopes and partly intercalated dark brown layers overlain by loose and consolidated diamicts exposed in near vertical walls in the proximal flank these are interpreted as supraglacial debris flow units with intercalated fluvial wash horizons glaciotectonised and subglacial traction till with boudinaged and streaked out sediment lenses and palaeosoils overlain by sediment produced by overtopping of the former moraine surface during a subsequent advance of the glacier clast shape analysis and process observations reveal that the dominant mode of transport is subglacial and glaciofluvial and that the main mode of sediment delivery to the moraines is by debris flows after the material has been transferred from the bed via englacial debris bands and meltout at the surface this differs from previous studies that found that a supraglacial source was dominant sedimentary structures clast fabric and process observations during the 1979 1980 readvance of findelengletscher strongly suggest that proximal layers of reworked pre existing sediments and or basal traction zone till have been plastered onto the moraine core in several locations causing a high degree of overconsolidation and strongly clustered fabric eigenvalues s 1 0 94 with clustering parallel to the moraine crestline this suggests that a combination of basal lateral drag and lateral plastering produces the observed proximal stability and ensures a high preservation potential we develop a conceptual model that describes alpine lateral moraines as structurally complex landforms that do not just record a single event as often surmised and we discuss implications for palaeo glacier reconstruction and the application of numerical dating methods

genesis of an imbricate push moraine hofdabrekkujokull iceland observations on a push moraine now being formed at the margin of the advancing glacier hofdabrekkujokull in iceland provide a background for interpreting the geomorphic and paleoclimatic significance of pleistocene push moraines this moraine up to 10 m high consists partly of unfrozen thrust slabs of glaciofluvial sand and partly of debris derived from the glacier surface during the present advance 10 to 12 m yr 1982 thrust planes intersect the glacier foreland and recurrent thrusting produces an imbricate structure as the moraine grows in height folds and faults are produced as the first formed slabs are rotated slowly backward up the glacier front and the whole moraine deforms under its own weight simultaneously the moraine receives a cover of supraglacial debris from the glacier surface above during the summer of 1982 the push moraine moved forward at a rate averaging about 4 cm day

the final phase of dead ice moraine development processes and sediment architecture kotlujokull iceland consecutive phases of de icing of ice cored moraines and the formation of dead ice moraine were monitored over a 4 year period at the terminus of the kotlujokull glacier iceland particularly the transition from partially ice cored moraine with isolated dead ice blocks to the ice free landscape receives attention in this paper in order to link the final melting processes to the architecture of the sedimentary end product in the current humid sub polar climate of south iceland de icing of partially ice cored moraines results chiefly from melting along the bottom surface of ice cores with an annual average rate of 25 cm the final de icing is associated with an interrelated group of re sedimentation processes and surface features series of sinkholes evolve at the toe of dead ice blocks which initiate retrogressive rotational sliding or backslumping of the ice cored slopes and the formation of distinct edges and fractures in the adjacent basins although backslumping is the dominant process in this phase of re sedimentation structures resulting from this process are rarely recognized in the ice free landscape as ice cores gradually diminish the effect of the latest re sedimentation events will overprint or destroy most existing sedimentary characteristics thus in the ice free landscape structures mainly related to the formation of sinkholes and fractures remain imprinted on the sediment succession generally no inversion of the topography occurs during the final phase of de icing the overall topography recognized in the late phase of the fully ice cored terrain is merely lowered and the amplitude of the relief reduced as de icing progresses the sediment architecture of the ice free landscape is characterized by heterogeneous and often slumped diamict sediments with variable thickness and lateral distribution clast orientation is related to the direction of slopes and boulders are found in isolated groups or in linear arrangements

modern glacier characteristics as a basis for inferring former climates with particular reference to the loch lomond stadial abstract studies of the mass balance of modern glaciers have indicated that the equilibrium line altitude ela is the most critical parameter in the link between glaciers and climate average accumulation on a glacier includes components derived from direct precipitation on the glacier surface as well as wind drifting and avalanching of snow and approximates closely to accumulation at the equilibrium line ablation is most usefully predicted by mean summer temperature and there is a close non linear relationship between accumulation and mean summer temperature at the equilibrium line following discussion of methods of reconstructing former glaciers and calculating their equilibrium line altitudes the application of the above relationships to the loch lomond readvance glaciers of highland britain is considered and an outline of the precipitation pattern and the mean summer temperature of the loch lomond stadial is given

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

lithofacies types and vertical profile models an alternative approach to the description and environmental interpretation of glacial diamict and diamictite sequences abstract increased knowledge of modern glacial depositional environments has resulted in rapidly evolving classifications of glacial tills these are based to a large degree on theoretical considerations of likely depositional processes the classifications are sophisticated and more advanced than the establishment of simple field criteria whereby individual till facies can be identified in quaternary and pre quaternary successions this situation is compounded in many quaternary terrains by the continued description of tills in terms of laboratory derived analytical data only reflecting a traditional interest in stratigraphic correlation rather than reconstruction of depositional environment detailed sedimentological logging of lithofacies is rarely undertaken there is thus considerable confusion as to what is being described or sampled when analytical data are presented for many pleistocene tills the same remarks apply to pre pleistocene tillites a lithofacies code is presented here for the rapid description and visual appraisal of field sequences or drill cores containing unconsolidated diamicts or lithified diamictites the term till is not used as it has a strict genetic definition referring to direct aggregation and deposition by glacier ice use of a four part code in conjunction with codes already published for fluvial sediments allows fundamental field properties to be depicted independent of genetic terminology and provides a firm basis for subsequent environmental interpretation and analytical work the value of this approach is illustrated by comparing a representative suite of vertical profiles of diamict assemblages deposited by modern grounded glaciers with a classic late pleistocene glacigenic sequence at scarborough bluffs ontario

should quaternary sea level changes be used to correct glacier elas vegetation belt altitudes and sea level temperatures for inferring climate changes abstract changes in the altitudes of glacier snowlines elas and the altitudes of montane vegetation belts vbas measure quaternary climatic change an accepted correction to such changes by deducting the amount of contemporary sea level fall is wrong since the air displaced by the ice sheets approximately fills the space left by the falling sea level and so there is no overall downward movement of the troposphere this also causes a reduced cooling at the lowered sea level relative to that at the former inter glacial sea level about 1 c at the las glacial maximum which reduces the discrepancies previously noted by others between terrestrial and marine estimates of sea level cooling the change in temperature is indicated by the product of the ela or vba lowering and the environmental lapse rate elr prior estimates of ela 900 135 m and elr 6 0 1 c km 1 would indicate a cooling of 5 4 c at interglacial sea level and 4 4 c at glacial sea level although glacial period elrs are not known reliably established ela corrections for local epeirogenic uplift or subsidence are appropriate

climate at the equilibrium line of glaciers the relationships between temperature precipitation and radiation on glacier equilibrium lines are investigated using 70 glaciers for which the mass balance and meteorological observations have been carried out for sufficiently long periods it is found that the characteristic climate at glacier equilibrium lines can be described using the summer 3 months temperature in a free atmosphere annual total precipitation and the sum of global and long wave net radiation all of these are measured at or very near the equilibrium line altitudes then it is shown how the shift of the equilibriumline will occur as a result of a climatic change finally the effect of the shift of the equilibrium line on the annualmean specific mass balance is analytically derived and compared with observations the present results make it possible to identify the altitudes in climate models where glacierization should begin and to evaluate the mass balance changes as a result of possible future changes in the climate

the geomorphological impact of loch lomond younger dryas stadial plateau icefields in the central lake district northwest england detailed geomorphological mapping has revealed evidence for the development of plateau icefields in the central fells of the english lake district during the loch lomond younger dryas stadial ca 12 9 11 5 ka the largest plateau icefield system which covered an area of approximately 55 km2 including outlet glaciers was centred on high raise to the west smaller plateau icefields developed on grey knotts brandreth and dale head covering areas of 7 km2 and 3 km2 respectively the geomorphological impact of these plateau icefields appears to have been minimal on the summits where the survival of blockfields and other frost weathered debris mostly peat covered implies the existence of at least patches of protective cold based ice ice moulded bedrock at some plateau edges however documents a transition to wet based erosive conditions prominent moraine systems were produced by outlet glaciers which descended into the surrounding valleys where their margins became sediment traps for supraglacial debris and inwash in some valleys ice marginal moraines record successive positions of outlet glaciers which actively back wasted towards their plateau source this interpretation differs from that of previous workers who assumed an alpine style of glaciation with reconstructed glaciers emanating from corries and valley heads it is likely that plateau icefields were more common at this time in upland britain than hitherto has been appreciated

the use of hypsometry to indicate long term stability and response of valley glaciers to changes in mass transfer a simple equation is derived relating the net mass balance and hypsometric curves of a steady state valley glacier it is used to examine how valley shape is linked to disparate extents and responses of glaciers subjected to similar climatic conditions examples are given which show that area based indices e g aar for estimating the equilibrium line altitude ela may be subject to a substantial built in variance because they implicitly rely upon similarity of glacier shape and regimen over a region if accurate topographic maps are available the equation may be used to infer the regimen of modern glaciers in the form of a dimensionless ratio of net mass balance gradients alternatively if similar information is available concerning regional glacier regimen disparate extents and responses may be collectively utilized to estimate values of ela or to infer climatic influence taking glacier hypsometry into account

exhumation rates in the st elias mountains alaska abstract reprocessing and interpretation of seismic profiles from the gulf of alaska in the vicinity of the st elias mountains indicate that over 3000 km 3 of sediment were deposited on the ocean shelf since the end of the last glacial epoch approximately 10 000 years ago this estimate of the sediment volume does not include material moved out of the region by long shore currents transportation from the shelf to deeper waters or material trapped in fiords and basins on and near land thus an estimated sedimentation rate offshore of 7 9 mm year and the average erosion rate of 5 1 mm year from the st elias mountains derived from the estimated sedimentation rate represent minimum estimates we infer that these estimated rates are not typical of the approximately 5 m y history of mountain building in the area but rather they represent the result of efficient erosion by glaciers during this interglacial period

sedimentary and tectonic architecture of a large push moraine a case study from hagafellsjokull eystri iceland original article can be found at http www sciencedirect com science journal 00370738 copyright elsevier b v full text of this article is not available in the uhra

a reinterpretation of scottish hummocky moraine and its significance for the deglaciation of the scottish highlands during the younger dryas or loch lomond stadial the aim of this paper is to demonstrate that much of the hummocky moraine present within the northern part of the lochlomond readvance ice cap formerly situated in the north west scottish highlands may be interpreted as suites of ice front moraines deposited during active decay these landforms can be used to reconstruct ice cap decay whichleads to important insights into the shrinking form of the ice cap and associated environmental conditions evidence has been collected from 10803 airphotographs and from detailed field survey it is presented at three spatial scales

timing equilibrium line altitudes and climatic implications of two early holocene glacier readvances during the erdalen event at jostedalsbreen western norway following the younger dryas the e rst evidence of glacial activity in southern norway in response to climatic change occurred during the early holocene when terminal moraines from the erdalen event formed beyond the position of later little ice age moraines in front of present outlet glaciers on both sides of the jostedalsbreen ice cap sets of pre little ice age marginal moraines have been morphostratigraphicallycorre lated with the erdalen event the lithostratigraphyin a peat bog at hellemyrane in jostedalen western norway provides e rm evidence for a two phase erdalen event associated with two glacier readvances of nigardsbreen at the preboreal boreal transition radiocarbon dates from the peat bog give age estimates for the two phases the e rst erdalen event readvance took place between 10 100 and 10 050 cal bp while the second occurred close to 9700 cal bp the lowering of the equilibrium linealtitude ela during these readvances is estimated using the little ice age ratio lr approach to be about 230 m and 215 m respectively the e rst readvance is attributed to an increase in winter precipitation while the second readvance may have been primarily caused by a marked drop in summer temperature which reactivated already existing ice masses

a review of topographic controls on moraine distribution ice marginal moraines are often used to reconstruct the dimensions of former ice masses which are then used as proxies for palaeoclimate this approach relies on the assumption that the distribution of moraines in the modern landscape is an accurate reflection of former ice margin positions during climatically controlled periods of ice margin stability however the validity of this assumption is open to question as a number of additional nonclimatic factors are known to influence moraine distribution this review considers the role played by topography in this process with specific focus on moraine formation preservation and ease of identification topoclimatic controls are not considered published literature indicates that the importance of topography in regulating moraine distribution varies spatially temporally and as a function of the ice mass type responsible for moraine deposition in particular in the case of ice sheets and ice caps 1000 km2 one potentially important topographic control on where in a landscape moraines are deposited is erosional feedback whereby subglacial erosion causes ice masses to become less extensive over successive glacial cycles for the marine terminating outlets of such ice masses fjord geometry also exerts a strong control on where moraines are deposited promoting their deposition in proximity to valley narrowings bends bifurcations where basins are shallow and or in the vicinity of topographic bumps moraines formed at the margins of ice sheets and ice caps are likely to be large and readily identifiable in the modern landscape in the case of icefields and valley glaciers 10 1000 km2 erosional feedback may well play some role in regulating where moraines are deposited but other factors including variations in accumulation area topography and the propensity for moraines to form at topographic pinning points are also likely to be important this is particularly relevant where land terminating glaciers extend into piedmont zones unconfined plains adjacent to mountain ranges where large and readily identifiable moraines can be deposited in the case of cirque glaciers 10 km2 erosional feedback is less important but factors such as topographic controls on the accumulation of redistributed snow and ice and the availability of surface debris regulate glacier dimensions and thereby determine where moraines are deposited in such cases moraines are likely to be small and particularly susceptible to post depositional modification sometimes making them difficult to identify in the modern landscape based on this review we suggest that despite often being difficult to identify quantify and mitigate topographic controls on moraine distribution should be explicitly considered when reconstructing the dimensions of palaeoglaciers and that moraines should be judiciously chosen before being used as indirect proxies for palaeoclimate i e palaeoclimatic inferences should only be drawn from moraines when topographic controls on moraine distribution are considered insignificant

transverse englacial debris rich ice bands at kviarjokull southeast iceland thick exposures of debris rich ice at various icelandic glaciers are central to the debate over the prevalence of glacial sediment transfer by glaciohydraulic supercooling we present physical analyses of ice and debris at kviarjokull a temperate glacier in southeast iceland with a terminal glacier bed overdeepening where stratified debris rich ice forms up to metre thick transverse englacial bands our results are not consistent with debris rich ice formation predominantly by supercooling because 1 137cs was absent from sediment filtered from debris rich ice 2 isotopic analysis d and 18o demonstrated no clear pattern of isotopic enrichment of debris rich ice with respect to englacial ice and 3 melt out debris from debris rich ice included large striated clasts from both fluvial and basal sources we support transverse englacial debris rich ice band formation by the thickening and elevation of basal materials in a region of longitudinally compressive ice flow situated between the reverse slope of the overdeepening and the base of an ice fall debris band form and distribution are likely to be controlled by thrusting along transverse englacial foliae associated with the formation of band ogives on the glacier surface

palaeoclimatic reconstruction from loch lomond readvance glaciers in the west drumochter hills scotland geomorphological mapping in the west drumochter hills provides evidence of a readvance of locally nourished glaciers during the loch lomond younger dryas stade in the form of an icefield 67 7 km2 in area drained by outlet glaciers the icefield limits accord broadly with those proposed by sissons 1980 but all geomorphic stratigraphic and sedimentological evidence conflicts with a recent proposal that the landforms in the area reflect southwestwards retreat of the last ice sheet up valley continuity of recessional moraines indicates that the ice remained active and close to climatic equilibrium during the earlier stages of glacier retreat consistent with slow warming following the coldest part of the stade the pattern of equilibrium line altitudes elas across the icefield is consistent with transfer of snow by westerly and southerly winds the ela of the reconstructed icefield as a whole is 622 629 m although this figure is likely to be lower than the regional climatic ela because the icefield probably received additional snow blown from adjacent plateau surfaces and slopes inclusion of potential snow blow areas in the ela calculation yields a value of 648 656 m the climatic ela is therefore likely to have lain between 622 and 656 m mean june to august temperature at the ela based on chironomid assemblages at two sites falls within the range 4 0 0 7 c empirical relationships between temperature and precipitation at modern glacier elas indicate that mean annual precipitation map at the ela was 1977 464 mm statistically indistinguishable from modern values comparison with precipitation values calculated for the isle of mull on the west coast suggest that the precipitation gradient across the central highlands of scotland was steeper during the loch lomond stade than at present probably as the result of efficient scavenging of precipitation from westerly airflows by the west highland icefield copyright 2005 john wiley sons ltd

reconstructing the transport history of glacigenic sediments a new approach based on the co variance of clast form indices abstract two indices are used to describe the aggregate shape and roundness characteristics of glacially transported clasts the c40 index the percentage of clasts with c a ratios 0 4 and the ra index the percentage of very angular and angular clasts in a sample analysis of the between and within sample co variance of these indices provides a powerful tool for discriminating actively and passively transported clasts in glacigenic deposits use of these indices is illustrated in an analysis of the form characteristics of clasts from lateral and frontal moraines at storbreen jotunheimen these fall between those of actively transported clasts in basal till low c40 and ra values and those of unmodified frost weathered clasts high c40 and ra values both indices decline down moraine within sample analyses of clast shape demonstrates that these aggregate clast form gradients reflect changes in the relative proportions of actively and passively transported debris on the moraines rather than progressive modification of actively transported clasts these analyses also indicate that actively transported clasts form the dominant component of the moraines particularly near the former glacier terminus further applications of the approach developed here are suggested

asymmetric growth of the pyrenees revealed through measurement and modeling of orogenic fluxes orogenic asymmetry is ubiquitous in terms of topography structure and metamorphism but the relative influences of climate and tectonics in determining such asymmetry remain contentious this study demonstrates that for the case of the european pyrenees orogenic asymmetry is not defined by inherited structural asymmetry nor by orographic asymmetry of precipitation but is the simple consequence of the inherent tectonic growth of a doubly vergent orogen the pyrenees record approximately 60 myr of upper crustal accretion erosion and sedimentation that developed from late cretaceous to early miocene times approximately 165 km of plate convergence was accommodated by four phases of orogenic growth that can be summarized in terms of their generic orogenic development as follows 1 early inversion of passive margin extensional faults initiating the pro wedge 2 growth by a combination of frontal accretion and underplating to the pro wedge symmetrical and steady record of erosion and foreland basin sedimentation 3 cessation of pro wedge frontal accretion with propagation of the retro wedge deformation front 4 accelerated growth of pro wedge antiformal stack induced by underplating accelerated erosion over antiformal stack and increase in sediment discharge to pro foreland basin stabilization of outer pro wedge by sediment blanketing discrete element model experiments are used to explore the natural tendency of the system towards asymmetry model output demonstrates that during active frontal accretion to the pro wedge of an orogen the maxima in erosional denudation is offset towards the pro wedge relative to the maximum depths of exhumation this asymmetry is fundamentally driven by the progressive reduction in advection velocities of material within the orogen from the pro wedge into the retro wedge hence for an efficient erosional regime a dynamic coupling between erosion and structural uplift of the pro wedge will reduce activity of the retro wedge and hence drive asymmetry in terms of low temperature thermochronometry erosion and sedimentation the models also demonstrate the tendency for pro wedge growth through frontal accretion to slow however the cessation of frontal accretion as recorded by the south pyrenean thrust belt phases 3 and 4 requires additional forcing it is proposed that the thick wedge top sedimentation recorded at this time increased taper angles and hence stabilized the wedge accretionary influx into the orogen at this time was accomplished through underplating these processes governing asymmetry do not require a spatially variable climate or a laterally heterogeneous underthrust plate

lateglacial and early holocene palaeoclimatic reconstruction based on glacier fluctuations and equilibrium line altitudes at northern folgefonna hardanger western norway northern folgefonna c 23 km 2 is a nearly circular maritime ice cap located on the folgefonna peninsula in hardanger western norway by combining the position of marginal mor aines with ams radiocarbon dated glacier meltwater induced sediments in proglacial lakes draining northern folgefonna a continuous high resolution record of variations in glacier size and equili brium line altitudes elas during the lateglacial and early holocene has been obtained after the termination of the younger dryas c 11 500 cal yr bp a short lived 100 150 years climatically induced glacier readvance termed the jondal event 1 occurred within the preboreal oscillation pbo c 11 100 cal yr bp bracketed to 10 550 10 450 cal yr bp a second glacier readvance is named the jondal event 2 a third readvance occurred about 10 000 cal yr bp and corresponds with the erdalen event 1 recorded at jostedalsbreen an exponential relationship between mean solid winter precipitation and ablation season temperature at the ela of norwegian glaciers is used to reconstruct former variations in winter precipitation based on the corresponding ela and an indepen dent proxy for summer temperature compared to the present the younger dryas was much colder and drier the jondal event 1 pbo was colder and somewhat drier and the jondal event 2 was much wetter the erdalen event 1 started as rather dry and terminated as somewhat wetter varia tions in glacier magnitude elas and corresponding palaeoclimatic reconstructions at northern folge fonna suggest that low altitude cirque glaciers lowest altitude of marginal moraines 290 m in the area existed for the last time during the younger dryas these low altitude cirque glaciers of sug gested younger dryas age do not fit into the previous reconstructions of the younger dryas ice sheet in hardanger copyright 2005 john wiley sons ltd

climatic reconstruction for the younger dryas early holocene transition and the little ice age based on paleo extents of argentiere glacier french alps abstract investigation of holocene extents of mountain glaciers along with the related naturally driven climate conditions helps improve our understanding of glacier sensitivity to ongoing climate change here we present the first holocene glacial chronology in the mont blanc massif argentiere glacier in the french alps based on 25 in situ produced cosmogenic 10be dates of moraines and glacial bedrocks the obtained ages from mapped sequences of moraines at three locations reveal that the glacier retreated from its lateglacial extent and oscillated several times between 11 7 ka and 10 4 ka i e during the younger dryas early holocene yd eh transition before substantially retreating at 10 4 ka climate conditions corresponding to the past extents of argentiere glacier during the yd eh transition 11 ka and the little ice age lia were modelled with two different approaches by determining summer temperature differences from reconstructed ela rises and by using a positive degree day pdd mass balance model the ela rise reconstructions yield a possible range of temperatures for the yd eh transition that were lower by between 3 0 and 4 8 c compared to the year 2008 depending on the choice of the ela sensitivity to temperature the results from the pdd model indicate temperatures lower by 3 6 5 5 c during the yd eh transition than during the 1979 2002 period for the lia our findings highlight the role of local precipitation changes superimposed on the dominant temperature signal in the detailed evolution of the glacier overall this study highlights the challenge that remains in accurately inferring paleoclimate conditions from past glacier extents

the pleistocene end moraine fans controls on their sedimentation and location abstract this paper presents a model of end moraine sedimentation based on data from pleistocene ice sheet margins according to this model end moraines quite often constitute alluvial fans or coalesced fans formed at the ice margin by redeposition of supraglacial material three types of end moraine fan have been recognized those composed mainly of mass flow deposits type a equivalent to dry alluvial fan in nonglacial settings those containing both mass flow and waterlain sediments type b and those that contain mainly sorted waterlain material type c equivalent to wet alluvial fan in nonglacial settings for each type of fan several sedimentary subenvironments differentiated by distance from the ice front are identified the diagnostic processes on the end moraine fans are cohesive and cohesionless debris flows or grain flows types a and b or hyperconcentrated flows and sheetflows types b and c the type b fan seems to represent the most typical sequence in the end moraine zones but the type c fan is also quite common at the pleistocene ice sheet margins our studies also suggest that the terminal supraglacial drainage controls the type of end moraine fan sedimentary subenvironment moraine types a b c whereas subglacial hydrology and ice stream regime which determine the mobility of the ice front and larger scale conditions of sediment supply to the ice margin control the location and size of the end moraine fan

sub annual moraine formation at an active temperate icelandic glacier this paper presents detailed geomorphological and sedimentological investigations of small recessional moraines at fjallsjokull an active temperate outlet of oraefajokull southeast iceland the moraines are characterised by striking sawtooth or hairpin planforms which are locally superimposed giving rise to a complex spatial pattern we recognise two distinct populations of moraines namely a group of relatively prominent moraine ridges mean height 1 2 m and a group of comparatively low relief moraines mean height 0 4 m these two groups often occur in sets systems comprising one pronounced outer ridge and several inset smaller moraines using a representative subsample of the moraines we establish that they form by either i submarginal deformation and squeezing of subglacial till or ii pushing of extruded tills locally proglacial glaciofluvial sediments are also incorporated within the moraines during pushing for the first time to our knowledge we demonstrate categorically that these moraines formed sub annually using repeat uncrewed aerial vehicle uav imagery we present a conceptual model for sub annual moraine formation at fjallsjokull that proposes the sawtooth moraine sequence comprises i sets of small squeeze moraines formed during melt driven squeeze events and ii larger push moraines formed during winter re advances we suggest the development of this process form regime is linked to a combination of elevated temperatures high surface meltwater fluxes to the bed and emerging basal topography a depositional overdeepening these factors result in highly saturated subglacial sediments and high porewater pressures which induces submarginal deformation and ice marginal squeezing during the melt season strong glacier recession during the summer driven by elevated temperatures allows several squeeze moraines to be emplaced this process form regime may be characteristic of active temperate glaciers receding into overdeepenings during phases of elevated temperatures especially where their englacial drainage systems allow efficient transfer of surface meltwater to the glacier bed near the snout margin

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

holocene mean july temperature and winter precipitation in western norway inferred from palynological and glaciological lake sediment proxies reconstructions of mean july temperature tjul and winter precipitation pw for the last 11 500 years on the folgefonna peninsula are presented tjul was reconstructed using pollen climate transfer functions and pw was reconstructed based on the exponential relationship between mean solid winter precipitation and ablation season temperature at the equilibrium line altitude ela with a reconstructed former ela using tjul as the proxy for ablation season temperature the reconstructions from the folgefonna peninsula suggest that the early holocene was relatively cool and dry until c 8000 cal yr bp followed by a warm and humid mid holocene until c 4000 cal yr bp with inferred tjul above 128c and pw reaching as high as 225 of the present day subsequent to c 4000 cal yr bp a reduction is seen in both inferred tjul and pw with large fluctuations during the last 500 years in addition new calculations of pw from two glaciers hardangerjokulen and jostedalsbreen in southern norway are presented the results show that pw varied in phase at all glaciers probably as a response to the same climate forcing factor during the early holocene a major shift is suggested between winds from the west and the east

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

last glacial maximum glaciers in the northern apennines reflect primarily the influence of southerly storm tracks in the western mediterranean abstract during the local last glacial maximum llgm the northern apennines hosted more than 100 valley and mountain glaciers covering collectively more than 260 km2 cosmogenic 10be exposure ages obtained for the first time along the apenninic range constrain the age of the llgm to pre date ca 21 ka the estimated volumes of these late pleistocene glaciers exceeded 9 1 km3 w e their reconstructed equilibrium line altitudes elas range from ca 1200 m a s l for northerly facing compound basin valley glaciers to ca 1620 m a s l for southerly facing mountain glaciers reconstructed elas in the western sector of the northern apennines were among the lowest recorded for the whole of the italian peninsula including the alps and also when compared with other mountain chains in the surrounding mediterranean basin these probably reflect exceptionally high accumulation rates fed by storm tracks in the western mediterranean which in turn has implications for the atmospheric circulation pattern that prevailed in the region at the time