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

surface melt driven seasonal behaviour englacial and subglacial from a soft bedded temperate glacier recorded by in situ wireless probes we investigate the spatial and temporal englacial and subglacial processes associated with a temperate glacier resting on a deformable bed using the unique glacsweb wireless in situ probes embedded in the ice and the till combined with other techniques including ground penetrating radar gpr and borehole analysis during the melt season spring summer and autumn high surface melt leads to high water pressures in the englacial and subglacial environment winter is characterised by no surface melting on most days base apart from a series of positive degree days once winter begins a diurnal water pressure cycle is established in the ice and at the ice sediment interface with direct meltwater inputs from the positive degree days and a secondary slower englacial pathway with a five day lag this direct surface melt also drives water pressure changes in the till till deformation occurred throughout the year with the winter rate approximately 60 that of the melt season we were able to show the bed comprised patches of till with different strengths and were able to estimate their size relative percentage and temporal stability we show that the melt season is characterised by a high pressure distributed system and winter by a low pressure channelized system we contrast this with studies from greenland overlying rigid bedrock where the opposite was found we argue our results are typical of soft bedded glaciers with low englacial water content and suggest this type of glacier can rapidly respond to surface driven melt based on theoretical and field results we suggest that the subglacial hydrology comprises a melt season distributed system dominated by wide anastomosing broad flat channels and thin water sheets which may become more channelized in winter and more responsive to changes in meltwater inputs

submarginal debris transport and till formation in active temperate glacier systems the southeast iceland type locality abstract exhaustive sedimentological analysis of freshly exposed subglacial surfaces and moraines in southern iceland provides diagnostic sedimentological signatures of a debris transport pathways through active temperate glacier snouts and b till production in subglacial traction zones dominated by deforming layers three till end members are recognised based on stratigraphic architecture 1 thin and patchy tills over eroded bedrock 2 single push moraines and complexes and 3 overridden moraines or outwash fans typical till thicknesses are 0 10 1 40 m with each till relating to a deformation event driven by the seasonally tuned processes of glacier sub marginal shearing freeze on squeezing and bulldozing clast form trends demonstrate progressive modification towards mature forms in subglacial traction zones with till being clearly differentiated from scree and glacifluvial deposits clast macrofabric strengths are variable rarely matching those of laboratory shearing experiments except where obviously lodged clasts are abundant they also consistently record former glacier flow directions but localized variability is introduced by bedrock protuberances cavity infill clast interference and freshly imported plucked clasts within tills macrofabrics strengthen from lower b horizon to upper a horizon tills but at the outer edges of sub marginally thickening till wedges or push moraines seasonally driven cycles of squeezing flowage freeze on melt out and bulldozing give rise to a range of clast macrofabric strengths as well as superimposed deformation signatures this reflects two extremes of till emplacement including the more mobile flowing and often liquefied matrixes in push squeeze moraines and in contrast the lodgement deformation and ploughing at the thin end of sub marginal till wedges

factors controlling the cenozoic sequence development in the eastern parts of the north sea the causal relationship between the cenozoic sequence development in the southeastern north sea basin and sea level changes climatic fluctuations and tectonic events is unravelled by relating variations in the relative sea level and base level based on interpretations of seismic surveys to published 18 o variations and eustatic changes the latter curve is based on the earth9s orbital forcing and here informally termed as the gsi curve the analysis shows that the cenozoic sequence development in the southeastern north sea was influenced by climatically and tectonically induced sea level changes the major cenozoic sequence stratigraphic boundaries lower order are highly influenced by tectonic events e g uplift of fennoscandia and increased subsidence rates in the basin centre reactivation of mesozoic fault zones controlled the deposition of minor sand bodies transported to the centre of the basin during the late palaeocene by mass flows the location of an oligocene mound structure which constitutes part of a sequence is controlled by the overall palaeotopography of the basin and local fault related depressions correlation between i the ages of our sequences and the 18 o variations in the oligocene succession and ii the gsi curve and the base level fluctuations of the late miocene and younger sequences show that the generation of the higher order sequence boundaries were driven by glacio eustatic sea level changes a climatic control of the sequence formation due to glacio eustatic sea level changes is therefore suggested for the oligocene and pliocene sequences and probably also for the upper miocene sequences

multiple subglacial till deposition a modern exemplar for quaternary palaeoglaciology the sedimentology of a vertical succession of alternating beds of massive and fissile diamictons on a orisjokull plateau icefield outlet foreland is employed to assess the evolution of subglacial traction tills at the margins of active temperate glaciers with deformable substrates where tills appear to form sub marginal incrementally thickened wedges that display multiple till emplacement events potentially of annual scale lodged boulders display strong a axes and surface striae alignments which parallel surface flutings indicating that fluting construction and till emplacement were related to moulding by consistent glacier flow from the ssw during the little ice age in contrast clast macrofabrics at the sub boulder size not unlike those reported from other icelandic tills are not as strong as would be expected in a subglacially sheared medium indicating shear strains too low for a steady state strain signature this separation of fabric data has isolated the strain signatures of the lodgement and deformation components of subglacial traction till whereby the orientations of the largest lodged clasts record high cumulative shear strains and those of the sub boulder sized clasts record greater susceptibility to deformation of their enclosing matrix this is likely due to the effect of clast collisions in clast rich till and the perturbations set up by the numerous large boulders consistent with observations on till fabrics in flutings and around lodged clasts a b plane macrofabric data display unusually high degrees of isotropy reflective of the more variable orientations of a b planes which are thought to reflect a b plane susceptibility to dip parallel or anastomosing shear planes a wide range of clast angularity values reflects the localized input of freshly plucked and hence relatively highly angular blocks to the deforming layer a characteristic of stepped bedrock profiles beneath the snouts of mountain glaciers finally we hypothesize that the massive and fissile units may represent a and b horizons of subglacial deforming layer couplets and that each couplet could record seasonal emplacement and partial inter couplet modification near the ice margin if the latter is the case then less than 1 m of subglacial till is advected to the glacier margin per annual deformation event

sediment deformation beneath glaciers rheology and geological consequences experiments beneath breidamerkurjokull in iceland have led to development of flow laws for the subglacial till relating strain rate to shear stress and effective pressure and assuming either bingham fluid or nonlinearly viscous fluid behavior water pressures in the till are less than ice pressures and it is suggested that this may lead to infiltration of ice into the sediment which inhibits sliding at the ice sediment interface where water pressures are equal or near to ice pressures infiltration does not occur and sliding may result a one dimensional theory of subglacial deformation is developed in which the empirical flow law is coupled with a model of subglacial hydrology and consolidation this predicts stable states in which subglacial sediment either does not deform or a dilatant deforming horizon forms with positive effective pressures at the ice bed interface or unstable states where zero or negative effective pressures are predicted time dependent analyses show that response times following perturbations of the system may be of the order of 103 years and thus that unsteady behavior may be normal on glaciers flowing over unlithified sediment beds it is suggested that the natural variability of material properties in subglacial sediment beds leads to the development of drumlins on the glacier bed it is suggested that unstable deformation at zero or negative effective stress leads to piping in subglacial sediments at the glacier terminus and the growth of sediment floored subglacial tunnels their frequency is that which is sufficient to draw down subglacial water pressures so as to prevent unstable deformation where they discharge large water volumes subglacial sediments flow laterally toward them producing tunnel valleys this sediment is then removed by water flowing along the axial tunnel tunnel valleys can be regarded as the equivalent in soft sediment areas of eskers in bedrock areas

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

dynamics of former ice lobes of the southernmost patagonian ice sheet based on a glacial landsystems approach reconstructions of former ice masses from glacial geomorphology help to constrain the nature and timing of glaciation in relation to climatic forcing this paper presents a new reconstruction of the glacial history of five ice lobes in southernmost south america the bahia inutil san sebastian magellan otway skyring and rio gallegos ice lobes we use previous geomorphological mapping of glacial landforms to reconstruct former glacial limits and proglacial lakes demarcate flow sets from the distribution of glacial lineations and evaluate glacial landsystem signatures and their palaeoglaciological implications evidence suggests that the ice lobes predominantly reflect active temperate glacial landsystems which may have switched to polythermal systems when periods of cold based ice developed ephemerally this complex landsystem signature implies that the ice lobes were sensitive to regional climate variability with active re advances during overall retreat of the ice margins there is also evidence for periods of fast ice flow and possible surge like activity in the region followed by the rapid retreat or even collapse of some of the ice lobes in association with proglacial lakes constraining our new reconstruction with published chronological information suggests that at least some of the ice lobes advanced before the global last glacial maximum glgm ca 26 5 19 ka during the last glacial cycle our new reconstruction demonstrates a more complex picture of ice dynamics than has previously been portrayed and one in which the advance and retreat of the ice lobes was likely to have been primarily driven by changes in climate as such ice advances before the glgm in the southernmost part of the patagonian ice sheet are likely to indicate a wider climatic forcing at this time

application of geomorphons for analysing changes in the morphology of a proglacial valley case study the scott river sw svalbard abstract the progressive degradation of the cryosphere of high arctic areas causes an increase in the dynamics of geomorphic processes that shape the valleys of rapidly retreating glaciers those especially sensitive to global environmental changes are the small land ending valley glaciers that are in the phase of strong retreat under these conditions the river valley s floors that are drained by proglacial waters are constantly undergoing intensive changes for the analysis of these changes two methods were used simultaneously as a synthesis to allow for quantitative and qualitative evaluation the first one is the increasingly more common dod method dem of difference which allows quantifying volumetric changes as a result of topographic differentiation the second one which was applied for the first time on a small valley spatial scale is the geomorphons method that makes it possible to assess the stability of landforms and to determine the directions of their new development to judge the applicability advantages and disadvantages of both methods for analysis of geomorphic changes in rapidly changing proglacial environments the study was carried out over a 3 3 km distance of the non glaciated section of the scott river valley course nw wedel jarlsberg land sw svalbard this area 1 3 km2 is currently shaped by a braided gravel bed river more accurately the study focused on the section spanning from the glacier terminus which is the source of the scott river to its outlet at the rechersche fjord bellsundfiorden the foundation for the development of comparative elevation models was a collection of terrestrial laser scanning tls surveys that were taken with a leica scanstation c10 scanner during the 2010 and 2013 snowmelt seasons on the basis of these surveys and with the use of tin interpolation high resolution 0 2 m digital terrain models dtms were generated the dtm models that had been prepared in this manner were used for the analysis of surface changes by employing geomorphic change detection gcd software and by simultaneously generating geomorphons maps for four selected test areas that covered characteristic fragments of the valley bottom 1 on the close forefield of the scott glacier terminus 2 in the immediate vicinity of the narrow valley outlet at the foot of the marginal moraine ridge 3 in the enlargement of the central section of the non glaciated valley floor 4 within the alluvial fan outlet to the fjord a comparison of the obtained results dod and geomorphons maps zonal statistics as well as a compilation of both the quantitative assessment of the scale of changes and the qualitative assessment of the transformation s direction allowed for reconstructing the range and rate of three year long changes in morphology at the analysed sections of the valley floor it was found that the pattern and rate of changes were closely related to the location of the test areas in the scott river s catchment system significant differences in the dynamics of processes shaping the valley landforms along the longitudinal valley course were found

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

the eyjabakkajokull glacial landsystem iceland geomorphic impact of multiple surges abstract a new glacial geomorphological map of the eyjabakkajokull forefield in iceland is presented the map covers c 60 km2 and is based on high resolution aerial photographs recorded in august 2008 as well as field checking landforms are manually registered in a geographical information system arcgis based on inspection of orthorectified imagery and digital elevation models of the area we mapped subglacially streamlined landforms such as flutes and drumlins on the till plain supraglacial landforms such as ice cored moraine pitted outwash and concertina eskers and ice marginal landforms such as the large multi crested 1890 surge end moraine and smaller single crested end moraines the glaciofluvial landforms are represented by outwash plains minor outwash fans and sinuous eskers extramarginal sediments were also registered and consist mainly of old sediments in wetlands or locally weathered bedrock eyjabakkajokull has behaved as a surge type glacier for 2200 years hence the mapped landforms originate from multiple surges landforms such as large glaciotectonic end moraines hummocky moraine long flutes crevasse fill ridges and concertina eskers are characteristic for surge type glaciers the surging glacier landsystem of eyjabakkajokull serves as a modern analog to the landsystems of terrestrial paleo ice streams

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

structural evolution triggers a dynamic reduction in active glacier length during rapid retreat evidence from falljokull se iceland over the past two decades iceland s glaciers have been undergoing a phase of accelerated retreat set against a backdrop of warmer summers and milder winters this paper demonstrates how the dynamics of a steep outlet glacier in maritime se iceland have changed as it adjusts to recent significant changes in mass balance geomorphological evidence from falljokull a high mass turnover temperate glacier clearly shows that between 1990 and 2004 the ice front was undergoing active retreat resulting in seasonal oscillations of its margin however in 2004 2006 this glacier crossed an important dynamic threshold and effectively reduced its active length by abandoning its lower reaches to passive retreat processes a combination of ice surface structural measurements with radar lidar and differential global navigation satellite systems data are used to show that the upper active section of falljokull is still flowing forward but has become detached from and is being thrust over its stagnant lower section the reduction in the active length of falljokull over the last several years has allowed it to rapidly reequilibrate to regional snowline rise in se iceland over the past two decades it is possible that other steep mountain glaciers around the world may respond in a similar way to significant changes in their mass balance rapidly adjusting their active length in response to recent atmospheric warming

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

fabric signature of subglacial till deformation breidamerkurjokull iceland the foreland of breidamerkurjokull iceland is the only locality where tills known to have undergone subglacial deformation are exposed till on the foreland has a two tiered structure consisting of a dilatant upper horizon c 0 5 m thick and a compact lower till these horizons correspond to the ductile deforming a horizon and the brittle ductile b horizon observed below the glacier by g s boulton and co workers the relationship between known strain history and a variety of macrofabric elements is examined for these two genetic facies of deformation till the upper horizon exhibits variable a axis fabrics and abundant evidence for clast re alignment reflecting ductile flow and rapid clast response to transient strains in contrast the lower horizon has consistently well organized a axis fabrics with a narrow range of dip values recording clast rotation into parallel with strain axes during brittle or brittle ductile shear the data indicate that till strain history imparts identifiable macrofabric signatures providing important analogues to guide the interpretation of pleistocene tills

surges of glaciers in iceland surges are common in all the major ice caps in iceland and historical reports of surge occurrence go back several centuries data collection and regular obser vationover thelast several decadeshave permitteda detailed descriptionof several surges fromwhich it is possible to generalize onthe nature of surging in icelandic glaciers com bining the historical records of glacier front variations and recent field research we sum marize the geographic distribution of surging glaciers their subglacial topography and geology the frequency andduration of surges changes in glacier surface geometry during the surge cycle and measured velocity changes comparedto calculatedbalance velocities wenotetheindicatorsofsurgeonsetanddescribechangesinice waterandsedimentfluxes duringa surge surgesaccomplishasignificantfractionofthetotalmasstransportthrough the main outlet glaciers of ice caps in iceland and have important implications for their hydrology ouranalysisof the data suggeststhat surge type glaciersin icelandarecharac terizedbygentlysloping surfacesandthatthey movetoo slowlytoremain inbalance given their accumulation rate surge frequency is neither regular nor clearly related to glacier size or massbalance steeply sloping glaciers whetherhard or soft bedded seemto move sufficiently rapidly to keep inbalance with the annual accumulation

the glacial landsystem of fjallsjokull iceland spatial and temporal evolution of process form regimes at an active temperate glacier this study assesses the spatial and temporal evolution of the glacial landsystem signature at fjallsjokull southeast iceland using a mapping of the glacial geomorphology and surficial geology and b repeat uncrewed aerial vehicle uav surveys a small scale 1 15 000 scale landsystem map has been compiled using lidar data 2011 2012 and historical aerial photographs 1945 1998 along with a large scale 1 2000 scale map based on uav imagery from may 2019 from our mapping and uav surveys we identify sediment landform assemblages that are typical of active temperate glacial landsystems including recessional push squeeze moraines and intervening flutings overridden moraine arcs proglacial outwash sandur fans and linear ribbon sandar we recognize three landform zones that are defined by changes in moraine morphology and the nature of proglacial outwash deposition 1 the outer foreland is characterized by proglacial outwash fans overridden moraine arcs and broadly linear recessional moraines 2 the middle foreland contains sawtooth moraines and linear sandar and 3 the innermost zone comprises extremely sawtooth and hairpin moraines as well as associated crevasse squeeze ridge limbs this landform zonation reflects spatio temporal changes in moraine forming processes and outwash deposition as determined by changes in snout morphology and proglacial drainage characteristics within this general tripartite zonation we also identify localized azonal intrazonal sediment landform assemblages that are not typically found at active temperate glaciers including ice cored hummocky terrain and localized kame and kettle topography repeat uav surveying in 2016 2019 has allowed us to capture and quantify recent intrazonal landsystem change at the southern glacier margin we identify a switch from moraine formation to the development of ice cored terrain and an ice cored esker complex in association with the uncovering of a depositional overdeepening our study demonstrates the important role that variations in local boundary conditions e g topography can play in the process form response of individual active temperate outlet glaciers contributing to the expanding database on modern glacial landsystems

ice cored moraine degradation mapped and quantified using an unmanned aerial vehicle a case study from a polythermal glacier in svalbard ice cored lateral frontal moraines are common at the margins of receding high arctic valley glaciers but the preservation potential of these features within the landform record is unclear recent climatic amelioration provides an opportunity to study the morphological evolution of these landforms as they de ice this is important because high arctic glacial landsystems have been used as analogues for formerly glaciated areas in the mid latitudes this study uses sfm structure from motion photogrammetry and a combination of archive aerial and uav unmanned aerial vehicle derived imagery to investigate the degradation of an ice cored lateral frontal moraine at austre lovenbreen svalbard across the study area as a whole over an 11 year period the average depth of surface lowering was 1 75 0 89 m the frontal sections of the moraine showed low or undetectable rates of change spatially variable rates of surface lowering are associated with differences in the quantity of buried ice within the structure of the moraine morphological change was dominated by surface lowering with limited field evidence of degradation via back wastage this permits the moraine a greater degree of stability than previously observed at other sites in svalbard it is unclear whether the end point will be a fully stabilised ice cored moraine in equilibrium with its environment or an ice free lateral frontal moraine complex controls on geomorphological change e g topography and climate and the preservation potential of the lateral frontal moraine are discussed the methods used by this research also demonstrate the potential value of sfm photogrammetry and unmanned aerial vehicles for monitoring environmental change and are likely to have wider applications in other geoscientific sub disciplines

an assessment of fluting and till esker formation on the foreland of sandfellsjokull iceland abstract intensive sedimentological analysis of tills parallel sided flutings and a conduit fill till esker on the recently deglaciated foreland of sandfellsjokull a temperate actively receding piedmont lobe draining the eastern margin of the m rdalsjokull ice cap in southern iceland reveals that subglacial sediment was emplaced predominantly as a dilatant a horizon after an initial phase of glacitectonite production from local outwash clast macrofabric strengths weakened through time presumably in response to increasingly wetter substrate conditions until the emplacement of the fluted till when clast alignment was more tightly constrained the fluting phase was initiated only after boulders were plucked from an adjacent bedrock cliff and lodged at the ice till interface this suggests that the parallel sided flutings constrained shearing at the ice bed interface in a similar fashion to a fault gouge thereby strengthening clast alignments but allowing the till to mould around larger obstacles to produce herringbone fabric patterns strong clast macrofabric strengths in the till esker are not parallel to the ice flow direction but instead align parallel with the local axis of the meandering ridge this suggests that the till esker was likely produced by the squeezing of a dilatant till into an elongated cavity or r channel after meltwater evacuation followed by localized deformation constrained by the channel walls as the channel moved downvalley because of ice flow the short period over which the deformation took place was enough to impart weaker fabrics in parts of the conduit that lie transverse to the ice flow direction and stronger fabrics where the conduit trends toward parallelism with the ice flow

glacial landsystems of the southwest laurentide ice sheet modern icelandic analogues landform assemblages and associated stratigraphy sedimentology and structure are used in the reconstruction of palaeo ice sheet dynamics in alberta western canada interpretations are based upon the modern analogues from four outlet glaciers at the margins of vatnajokull and myrdalsjokull iceland in the area between lloydminster and lac la biche central alberta an extensive landform assemblage of megaflutings crevasse squeeze ridges and thrust block moraine arcs document the former surging of part of the margin of the laurentide ice sheet during later stages of recession this landform assemblage including numerous exposures of glacitectonised bedrock and quaternary sediments is comparable to the landsystem of the surging glaciers eyjabakkajokull and bruarjokull in iceland near high river southern alberta the former existence of an ice lobe characterised by active recession is recorded by closely spaced low amplitude recessional push moraines that drape tunnel valleys these are comparable in form and pattern to annual push moraines and fluted till surfaces produced by breidamerkurjokull and sandfellsjokull iceland and also include rimmed depressions produced by the escape of artesian water during ice marginal pushing this study provides interpretations of the regional glacial geomorphology of alberta based upon comparisons of form and stratigraphy with modern glacial analogues and provides an alternative to recent models which invoke large floods of subglacial meltwater to explain many of these same features implications for ice dynamics and regional till stratigraphies are discussed copyright 1999 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

the interpretation and classification of subglacially deformed materials abstract a general classification of subglacially deformed materials is proposed based on sediment properties and their relationship to styles of subglacial strain deformation till is defined as homogenized usually diamictic material formed by glacially induced shear of subsole materials three types are recognized type a formed by pervasive ductile deformation type b formed by brittle shear and comminution till produced by the reduction of void space by in situ crushing and abrasion the term glacitectonite is adopted for materials that have undergone subglacial shear but retain some of the structural characteristics of the parent material original structures may be truncated by glacitectonic fabric elements type a or distorted but not truncated type b the principles of strain and material response particle orientation mechanisms fabric development and drainage conditions are reviewed examples of deformation tills and glacitectonites from breidamerkurjokull iceland slettmarkbreen norway loch lomond scotland and east yorkshire england are used to illustrate the nature of subglacially deformed materials and their relationship to former subglacial strain and drainage conditions the geologic evidence suggests a continuum of bed strengths can be recognized in deforming substrata ranging from high strength low strain type b deformation till and comminution till to low strength high strain type a deformation till

late mesozoic and tertiary sediment supply to the eastern cape basin se atlantic and palaeo drainage systems in southwestern africa isopach asymmetry and sediment component changes in dsdp cores from the se atlantic orange basin support the hypothesis of major drainage system changes in sw africa during late cretaceous cenozoic time this involved alternations in the use of the 28 s modern orange river and 31 s modern olifants river exit points across the western escarpment by rivers carrying run off from the upper orange vaal catchment areas as well as radical re organizations of internal drainage geometry it is postulated that during late cretaceous times the 28 s exit was used with the middle orange river following a course in the interior well to the south up to 150 km of its modern channel sediment discharge rates from this river were relatively high at least 10 106 m3 yr 1 and resulted in rapid advancement of the continental margin sediment prism west of the mouth by large scale slumping the palaeogene orange vaal river exit was via the 31 s escarpment crossing and during the later part of this period the cape canyon was cut across the continental shelf and slope a significant reduction in sediment discharge to 2 0 106 m3 yr 1 suggests that the lower tertiary climate for sw africa was drier than that of late cretaceous times however aridity did not commence until late miocene times when the orange vaal discharge had switched back to the 28 s exit modern sediment discharge rates 6 5 106 m3 yr 1 are relatively high and reflect soil erosion caused by agricultural activity the two major alterations in exit point of the orange vaal late cretaceous early tertiary and late oligocene early miocene are related to periods of low sea level which promoted river capture adjacent to the western escarpment an additional factor in the first course change may have been the disruption of the middle orange channel by late cretaceous igneous intrusions less important internal reorganizations of the drainage system are postulated in late miocene pleistocene times economic implications for offshore diamond distribution are briefly mentioned

till deposition by glacier submarginal incremental thickening macro and micro scale sedimentological analyses of recently deposited tills and complex push squeeze moraines on the forelands of icelandic glaciers and in a stacked till sequence at the former younger dryas margin of the loch lomond glacier lobe in scotland are used to assess the depositional processes involved in glacier submarginal emplacement of sediment where subglacial meltwater is unable to flush out subglacial sediment or construct thick debris rich basal ice by cumulative freeze on processes glacier submarginal processes are dictated by seasonal cycles of refreezing and melt out of tills advected from up ice by a combination of lodgement deformation and ice keel and clast ploughing although individual till layers may display typical a and b horizon deformation characteristics the spatially and temporally variable mosaic of subglacial processes will overprint sedimentary and structural signatures on till sequences to the extent that they would be almost impossible to classify genetically in the ancient sediment record at the macro scale icelandic tills display moderately strong clast fabrics that conform to the ice flow directions documented by surface flutings very strong fabrics typify unequivocally lodged clasts despite previous interpretations of these tills as subglacial deforming layers micro morphological analysis reveals that shearing played only a partial role in the emplacement of till matrixes and water escape and sediment flowage features are widespread a model of submarginal incremental thickening is presented as an explanation of these data involving till slab emplacement over several seasonal cycles each cycle involves 1 late summer subglacial lodgement bedrock and sediment plucking subglacial deformation and ice keel ploughing 2 early winter freeze on of subglacial sediment to the thin outer snout 3 late winter readvance and failure along a decollement plane within the till resulting in the carriage of till onto the proximal side of the previous year s push moraine 4 early summer melt out of the till slab initiating porewater migration water escape and sediment flow and extrusion repeated reworking of the thin end of submarginal till wedges produces overprinted strain signatures and clast pavements

methodological sensitivity of morphometric estimates of coarse fluvial sediment transport abstract the estimation of fluvial sediment transport rate from measurements of morphological change has received growing recent interest the revival of the morphological method reflects continuing concern over traditional methods of rate determination but also the availability of new survey methods capable of high precision high resolution topographic monitoring remote sensing of river channels through aerial digital photogrammetry is a potentially attractive alternative to labour intensive ground surveys however while photogrammetry presents the opportunity to acquire survey data over large areas data precision and accuracy particularly in the vertical dimension are lower than in traditional ground survey methods this paper presents results of recent research in which digital elevation models dems have been developed for a reach of a large braided gravel bed river in scotland using both digital photogrammetry and high resolution rtk gps ground surveys a statistical level of change detection is assessed by comparing surfaces with independent check points the methodological sensitivity of the annual channel sediment budget 1999 2000 to the threshold is presented results suggest that while the remote survey methods employed here can be used to develop qualitatively convincing moderate precision dems of channel topography rmse 0 21 m the remaining errors imply significant limits on reliable change detection which lead to important information losses tests at a 95 confidence interval for change detection show that over 60 of channel deposition and 40 of erosion may be obscured by the lower level of precision associated with photogrammetric monitoring when compared to ground survey measurements this bias reflects the difficulty of detecting the topographic signature of widespread but shallow deposition on bar tops

the active temperate glacial landsystem a model based on breiðamerkurjokull and fjallsjokull iceland accurate interpretations of ancient glaciated terrains rely heavily on our knowledge of process form relationships in contemporary glacierized basins a landsystems model for temperate actively receding glaciers is presented based upon brei amerkurjokull and fjallsjokull iceland historical documentation maps and or aerial photography documenting recession since 1903 provide a unique series of snapshots of the evolving glacial geomorphology at these snouts this documentation is employed in association with sedimentological investigations to assess the evolution of sediment landform assemblages at active temperate glacier margins using the wealth of geomorphological and sedimentological information produced during the recent recession of brei amerkurjokull and fjallsjokull three depositional domains are recognized 1 areas of extensive low amplitude marginal dump push and squeeze moraines derived largely from material on the glacier foreland and often recording annual recession of active ice 2 incised and terraced glacifluvial forms such as recessional ice contact fans and hochsandur fans and simple and complex anabranched eskers and small areas of pitted outwash 3 subglacial landform assemblages of flutes drumlins and overridden push moraines located between ice marginal glacifluvial depo centres the lack of supraglacial sediment in active temperate glaciers like brei amerkurjokull and fjallsjokull generally precludes the widespread development of chaotic hummocky moraine the hummocky terrain previously termed kame and kettle topography has mostly evolved by melt out into a complex network of anabranched eskers over the period 1945 1998 or actually comprises pitted or kettled outwash sandar the tills across the foreland were emplaced by subglacial deformation and lodgement and comprise materials derived from pre existing stratified sediments in addition to localized abrasion of rock surfaces and patches of lake sediments till sequences thicker than 2 m have been constructed by the sequential plastering of till layers onto stratified sediments and bedrock because this stacking is a sub marginal process it is suggested that complex till sequences similar to those observed at brei amerkurjokull fjallsjokull may be employed in the reconstruction of ancient glacier margins additionally the geomorphology of the active temperate landsystem at east brei amerkurjokull may contain subtle surge signatures verifying the historical record of small surges by this part of the glacier this illustrates the danger of employing landform sediment associations from restricted study areas e g parts of landsystems as representative process form models for glaciated terrains

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

the drumlin field and the geomorphology of the mulajokull surge type glacier central iceland article i nfo herewe presenta newgeomorphological mapof the active drumlin field and theforefieldof mulajokull a surge type outlet glacier iceland the map is based on aerial photographs taken in 1995 and lidar data recorded in 2008 mapping was done using arcgis 10 software on orthorectified imagery lidar data and digital elevation models the mapped landforms were initially identified on the aerial imagery and lidar and then ground checked in the field we mapped subglacial supraglacial ice marginal periglacial and glaciofluvial landforms the geomorphology of the mulajokull forefield is similar to that of the forefields of other surge type glaciers in iceland with a highly streamlined forefield crevasse fill ridges and series of glaciotectonic end moraines how ever thelargenumber i e 110 of drumlinsformingthe drumlin fieldisuniqueformodernicelandicsurge type glaciersand as yet unique for contemporary glaciersingeneral also apparent isthat thedrumlins are widerand shorter in the distal part of the drumlin field and narrower and longer in the proximal part hence the mapping reveals a development of the drumlins toward a more streamlined shape of the proximal landforms that have experienced more surges the drumlins in the drumlin field are active i e they form during the modern surges of mulajokull

quantification of historical landscape change on the foreland of a receding polythermal glacier horbyebreen svalbard the assessment of multidecadal scale change in a polythermal glacial landsystem in the high arctic is facilitated by a quantitative approach that utilises time series of aerial photographs satellite images digital elevation models and field geomorphological mapping the resulting spatiotemporal analysis illustrates a transition from glacial to proglacial paraglacial conditions indicating that 1 the areal coverage of ice between the maximum lia extent and 2013 decreased from 29 35 to 16 07 km2 which is a reduction in the glacierized area in the catchment from 62 to 34 2 the ice volume loss in the proglacial area amounted to 214 9 3 million m3 which was attributed mostly to ablation of the glacier snout but to a lesser extent the degradation of ice cored landforms 3 the transition from areas formerly covered by glacier ice to ice cored moraines glacifluvial deposits and other landforms was the most intense in the period 1990 2013 4 two end member scenarios polythermal glacial landsystem domains evolve during glacier recession each one dictated by the volume of debris in englacial and supraglacial positions and include a subglacial surfaces limited englacial and supraglacial debris related to temperate basal ice and b ice cored lateral moraines and moraine mound complexes significant supraglacial debris accumulations related to marginal cold based ice an additional assemblage of geometric ridge networks discrete or linear englacial and supraglacial debris concentrations relates to crevasse and hydrofracture infill branching out from an esker complex and is indicative of either surging or later rapid release of pressurised meltwater from temperate to cold based parts of the former glacier snout

denudation rates for the southern drakensberg escarpment se africa derived from in situ produced cosmogenic 36c1 initial results cosmogenic 36 c1 concentrations in basalt samples from the drakensberg escarpment on the se african passive margin give quantitative estimates of denudation and scarp retreat rates over the 10 4 10 6 year timespan addressed by these data the calculated escarpment retreat rate has been 50 95 m ma 1 and the average summit denudation rate 6 m ma 1 the scarp retreat rate is an order of magnitude less than previously suggested the rate of summit lowering is sufficient to prevent the long term intact survival of erosion cycle surfaces formed in the mesozoic that were previously inferred for this region

glacial geological studies of surge type glaciers in iceland research status and future challenges abstract surging glaciers are potential analogues for land terminating palaeo ice streams and surging ice sheet lobes and research on surge type glaciers is important for understanding the causal mechanisms of modern and past ice sheet instabilities the geomorphic signatures left by the icelandic surge type glaciers vary and range from glaciotectonic end moraines formed by folding and thrusting crevasse squeeze ridges concertina eskers drumlins and fluted forefields to extensive dead ice fields and even drift sheets where fast ice flow indicators are largely missing we outline some outstanding research questions and review case studies from the surge type outlets of bruarjokull eyjabakkajokull and tungnaarjokull vatnajokull ice cap mulajokull and satujokull hofsjokull ice cap hagafellsjokull and su urjokull langjokull ice cap kaldalonsjokull leirufjar arjokull and reykjarfjar arjokull drangajokull ice cap as well as the surge type cirque glaciers in northern iceland we review the current understanding of how rapid ice flow is sustained throughout the surge the processes that control the development of the surge type glacier landsystem and the geological evidence of surges found in sediments and landforms we also examine if it is possible to reconstruct past surge flow rates from glacial landforms and sediments and scale up present day surge processes landforms and landsystems as modern analogues to past ice streams finally we also examine if there is a climate mass balance control on surge initiation duration and frequency

glacial geomorphology of terrestrial terminating fast flow lobes ice stream margins in the southwest laurentide ice sheet glacial geomorphological mapping of southern alberta canada reveals landform assemblages that are diagnostic of terrestrial terminating ice streams fast flowing outlet glaciers with lobate snouts spatial variability in features that comprise the landform assemblages reflects changes in a palaeo ice stream activity switch on off and b snout basal thermal regimes associated with climate sensitive steady state flow palaeo ice stream tracks reveal distinct inset sequences of fan shaped flowsets indicative of receding lobate ice stream margins former ice lobe margins are demarcated by a major often glacially overridden transverse moraine ridges commonly comprising glacitectonically thrust bedrock and b minor closely spaced recessional push moraines and hummocky moraine arcs details of these landform types are well exhibited around the former southern margins of the central alberta ice stream where larger scale more intensive mapping identifies a complex glacial geomorphology comprising minor transverse ridges mtr types 1 3 hummocky terrain ht types 1 3 flutings and meltwater channels spillways the mtr type 1 constitute the summit corrugation patterns of glacitectonic thrust moraines or major transverse ridges and have been glacially overrun and moderately streamlined the mtr type 2 sequences are recessional push moraines similar to those developing at modern active temperate glacier snouts the mtr type 3 document moraine construction by incremental stagnation because they occur in association with hummocky terrain the close association of hummocky terrain with push moraine assemblages indicates that they are the products of supraglacial controlled deposition on a polythermal ice sheet margin where the ht type 3 hummocks represent former ice walled lake plains the ice sheet marginal thermal regime switches indicated by the spatially variable landform assemblages in southern alberta are consistent with palaeoglaciological reconstructions proposed for other ice stream fast flow lobes of the southern laurentide ice sheet where alternate cold polythermal and temperate marginal conditions associated with climate sensitive steady state flow sequentially gave way to more dynamic streaming and surging activity

englacial and subglacial water flow at skalafellsjokull iceland derived from ground penetrating radar in situ glacsweb probe and borehole water level measurements we reconstruct englacial and subglacial drainage at skalafellsjokull iceland using ground penetrating radar gpr common offset surveys borehole studies and glacsweb probe data we find that englacial water is not stored within the glacier water content 0 0 3 instead the glacier is mostly impermeable and meltwater is able to pass quickly through the main body of the glacier via crevasses and moulins once at the glacier bed water is stored within a thin 1 m layer of debris rich basal ice 2 water content and the till the hydraulic potential mapped across the survey area indicates that when water pressures are high most of the year water flows parallel to the margin and emerges 3 km down glacier at an outlet tongue gpr data indicates that these flow pathways may have formed a series of braided channels we show that this glacier has a very low water storage capacity but an efficient englacial drainage network for transferring water to the glacier bed and therefore it has the potential to respond rapidly to changes in melt water inputs

glacier retreat and landform production on an overdeepened glacier foreland the debris charged glacial landsystem at kviarjokull iceland glacier recession and landform development in a debris charged glacial landsystem characterized by an overdeepening is quantified using digital photogrammetry digital elevation model dem construction and mapping of the icelandic glacier kviarjokull for the period 1945 2003 melting of ice cores is recorded by surface lowering rates of 0 8 m yr 1 1945 1964 0 3 m yr 1 1964 1980 0 015 m yr 1 1980 1998 and 0 044 m yr 1 1998 2003 the distribution preservation of pushed and stacked ice cored moraine complexes are determined by the location of the long term glacial drainage network in combination with retreat from the overdeepening into which glacifluvial sediment is being directed and where debris rich ice masses are being reworked and replaced by esker networks produced in englacial meltwater pathways that bypassed the overdeepening and connected to outwash fans prograding over the snout recent accelerated retreat of kviarjokull potentially due to increased mass balance sensitivity has made the snout highly unstable especially now that the overdeepening is being uncovered and the snout flooded by an expanding pro glacial and partially supraglacial lake this case study indicates that thick sequences of debris charged basal ice controlled moraine have a very low preservation potential but ice cored moraine complexes can develop into hummocky moraine belts in de glaciated terrains because they are related to the process of incremental stagnation which at kviarjokull has involved periodic switches from transport dominant to ablation dominant conditions glacier recession is therefore recorded temporally and spatially by two suites of landforms relating to two phases of landform production which are likely typical for glaciers occupying overdeepenings an early phase of active temperate recession recorded by push moraines and lateral moraines and unconfined pro glacial meltwater drainage and a later phase of incremental stagnation and pitted outwash head development initiated by the increasing topographic constraints of the latero frontal moraine arc and the increasing importance of the overdeepening as a depo centre copyright 2012 john wiley sons ltd

response of glacier flow and structure to proglacial lake development and climate at fjallsjokull south east iceland over recent decades the number of outlet glaciers terminating in lakes in iceland has increased in line with climate warming the mass balance changes of these lake terminating outlet glaciers are sensitive to rising air temperatures due to altered glacier dynamics and increased surface melt this study aims to better understand the relationship between proglacial lake development climate glacier dynamics and glacier structure at fjallsjokull a large lake terminating outlet glacier in south east iceland we used satellite imagery to map glacier terminus position and lake extent between 1973 and 2016 and a combination of aerial and satellite imagery to map the structural architecture of the glacier s terminus in 1982 1994 and 2011 the temporal evolution of ice surface velocities between 1990 and 2018 was calculated using feature tracking statistically significant increases in the rate of terminus retreat and lake expansion were identified in 2001 2009 and 2011 our surface velocity and structural datasets revealed the development of localised flow corridors over time which conveyed relatively faster flow towards the glacier s terminus we attribute the overall changes in dynamics and structural architecture at fjallsjokull to rising air temperatures but argue that the spatial complexities are driven by glacier specific factors such as basal topography

glacial geomorphology of the neutral hills uplands southeast alberta canada the process form imprints of dynamic ice streams and surging ice lobes abstract the neutral hills uplands of southern alberta canada is an area of complex and varied glacial landforms dominated by glacitectonic compressional structures but also containing expansive areas of hummocky terrain and kame and kettle topography it lies between the strongly streamlined trunks of the former central alberta cais and maskwa palaeo ice streams of the sw laurentide ice sheet lis and hence comprises an inter ice stream regional moraine zone constructed at around 15 5 cal ka bp this study aimed to compile a regional map of the glacial geomorphology of central southeast alberta in order to decipher the landform sediment signatures of overprinted ice stream margins in terrestrial continental environments and to refine the palaeoglaciological reconstructions for the southwest lis detailed mapping from lidar and aerial imagery identifies distinctive glacial landsystems diagnostic of the partial overprinting of cross cutting ice stream trunks and fast flow lobes widespread evidence of surge diagnostic features indicates that the ice streams experienced repeated flow instabilities consistent with the broader scenario of a highly dynamic and unstable sw lis characterised by markedly transitory and cross cutting palaeo ice streams the inter ice stream moraine zone is characterised by spectacular glacitectonic compression of bedrock cupola hill construction and mega raft displacement but also displays evidence of multi phase stagnant ice melt out where partially overprinted surge lobes advanced into large areas of buried glacier ice contemporaneous ice melting led to the widespread development of glacier karst and the production of eskers at a range of scales the largest of which record deranged drainage patterns indicative of ice walled channel sedimentation controlled by the regional bedrock slope towards the northeast these process form regimes have created a significant local relief that is a product of not only glacitectonic compression of bedrock but also the creation and melting of a melange of ice and bedrock sediment blocks of variable ice volume which are representative of former buried snout ice with a glacier karst system that was repeatedly proglacially thrust due to surging widespread evidence for subglacial channel cutting is likely strongly linked to the transitory surging and cross cutting nature of the palaeo ice streams in the region whereby ice streams switched on and surged in response to the build up migration and marginal outbursts of subglacial water reservoirs in addition to the reduced basal friction caused by the low permeability of the cretaceous bedrock pressurized groundwater and potentially also shallow biogenic gas deposits were likely important to the process form regimes of surging lobes of soft bedded ice streams in a region where ice flow was against an adverse bed slope a scenario that gave rise to a variety of enigmatic landforms such as doughnuts doughnut chains apparent blow out features and possible till eskers as well as glacitectonic mega rafts

lithofacies variations within sandur deposits the role of runoff regime flow dynamics and sediment supply characteristics abstract the icelandic sandur plains have for long acted as classic sites for models of braided river behaviour and of associated lithofacies assemblages however many of the icelandic sandurs are subject to repeated catastrophic flood events or jokulhlaups which are likely to have played a significant role in sandur construction established lithofacies models based on the icelandic sandurs have failed to take account of the varying runoff regimes which characterise the different sandur environments in addition sediment inputs to sandur channel systems are highly variable fluctuating in response both to varying runoff patterns and to advance and retreat of the source glacier that affect sediment availability within the proglacial zone this paper describes the main lithofacies types and vertical profiles that characterize the sandurs of south iceland and demonstrates that they can largely be attributed to extreme runoff events with few deposits typical of braided river facies occurring within the sedimentary record a preliminary qualitative model is developed that allows interpretation and prediction of vertical lithofacies profiles derived from glacial outwash in terms of i the drainage mechanism which in turn controls the dominant runoff population ii sediment availability and iii the spatial variability in flow dynamics

ice volume changes bias estimation of mass balance measurements and changes in subglacial lakes derived by lidar mapping of the surface of icelandic glaciers icelandic glaciers cover 11 000 km2 in area and store 3600 km3 of ice starting in 2008 during the international polar year accurate digital elevation models dems of the glaciers are being produced with airborne lidar more than 90 of the glaciers have been surveyed in this effort including vatnajokull hofsjokull myrdalsjokull drangajokull eyjafjallajokull and several smaller glaciers the publicly available dems are useful for glaciological and geological research including studies of ice volume changes estimation of bias in mass balance measurements studies of jokulhlaups and subglacial lakes formed by subglacial geothermal areas and for mapping of crevasses the lidar mapping includes a 500 1000 m wide ice free buffer zone around the ice margins which contains many glacio geomorphological features and therefore the new dems have proved useful in geological investigations of proglacial areas comparison of the lidar dems with older maps confirms the rapid ongoing volume changes of the icelandic ice caps which have been shown by mass balance measurements since 1995 96 in some cases ice volume changes derived by comparing the lidar measurements with older dems are in good agreement with accumulated ice volume changes derived from traditional mass balance measurements but in other cases such a comparison indicates substantial biases in the traditional mass balance records

a tenfold increase in the orange river mean holocene mud flux implications for soil erosion in south africa soil erosion poses a major threat to sustainable agriculture in southern africa but is difficult to quantify one measure of soil erosion is the sediment flux of rivers the orange river is the principal source of sediment to the western margin of south africa with an estimated mean mud flux over the last 11 500 years the holocene epoch of 5 1 3 2 7 4 million metric tons year mt yr a total of 43 gigatons gt 10 15 g representing 72 of the holocene mud flux has accumulated on the shelf in the orange river prodelta and mudbelt a clayey fine silt deposit focused on the inner to middle shelf only 8 5 gt of the mud flux occurs in holocene calcareous ooze on the slope comparison of the clay to mud ratio of offshore deposits with orange river suspended sediment and catchment soils indicates that 20 11 gt of the holocene mud flux has been lost as clay beyond the margin the orange river mud flux prior to the building of large dams 1930 1969 is ten times greater than the mean holocene mud flux and is reconciled with estimates of soil erosion within the catchment a tenfold increase in the orange river mud flux implies up to a hundredfold increase in total soil erosion depending on the extent of mud storage over periods of decades to centuries within the catchment erosion has shifted from areas of high relief and rainfall of the drakensberg escarpment during the holocene to intensely cultivated lands of low relief having moderate to high rainfall in the eastern catchment and to a lesser extent grazing areas of the southern orange river catchment

sediment deformation beneath glaciers and its coupling to the subglacial hydraulic system abstract the extent and style of shear deformation in sediments beneath modern glaciers and the geological evidence for such deformation in deposited sediments are reviewed new evidence is presented from beneath a modern glacier of the spatial and temporal patterns of water pressure fluctuation and of time dependent patterns of deformation in sediments it is concluded that in most experimental sites beneath soft bedded modern glaciers deformation is a significant or major contributor to glacier movement and the resultant discharge of till is large enough to make sediment deformation a major till forming process particular modes of deformation facilitate incorporation of underlying material into the till whilst the capacity of a deforming till to absorb strain can protect the underlying strata from deformation leading to the commonly found relationship where till overlies other strata with a sharp planar interface it is argued that the almost ubiquitous occurrence of drumlins on the beds of former ice sheets is a reflection of the widespread occurrence of sediment deformation beneath them with important implications for the coupling of ice sheet flow and bed properties it is argued that the mechanical behaviour of the subglacial system is not simply determined by till properties but largely controlled by the subglacial water pressure regime determined by the nature of subglacial drainage results of field experiments show how the nature of the basal hydraulic system can play a vital role in controlling the coupling between the glacier and till deformation processes they show that rapid glacier advances can produce undrained loading of sediments that effective pressure may increase either upwards or downwards in a till according to the direction of drainage and that interstitial water pressures in subglacial sediments can show large and rapid variations producing strong variations in the rate and distribution of strain and in the partitioning of basal movement between sliding and deformation

magnitude and frequency in proglacial rivers a geomorphological and sedimentological perspective abstract proglacial fluvial sedimentary systems receive water from a variety of sources and have variable discharges with a range of magnitudes and frequencies little attention has been paid to how these various magnitude and frequency regimes interact to produce a distinctive sedimentary record in modern and ancient proglacial environments this paper reviews the concept of magnitude and frequency in relation to proglacial fluvial systems from a geomorphic and sedimentary perspective rather than a hydrological or statistical perspective the nature of the meltwater inputs can be characterised as low magnitude high frequency primarily controlled by ablation inputs from the source glacier or high magnitude low frequency primarily controlled by exceptional inputs the most important high magnitude low frequency inputs are catastrophic outburst floods often referred to by the term jokulhlaup icelandic for glacier burst glacier surges are an additional form of cyclical variation impacting the proglacial environment which briefly alter the volumes and patterns of meltwater input the sedimentary consequences of low magnitude high frequency discharges are related to frequent variations in stage the greater directional variability that sediment will record and the increased significance of channel confluence sedimentation in contrast the most significant characteristics of high magnitude low frequency flooding include the presence of large flood bars and mid channel jokulhlaup bars hyperconcentrated flows large gravel dunes and the formation of ice block kettle hole structures and rip up clasts glacier surges result in a redistribution of low magnitude high frequency processes and products across the glacier margin and small floods may occur at the surge termination criteria for distinguishing magnitude and frequency regimes in the proglacial environment are identified based on these major characteristics studies of quaternary proglacial fluvial sediments are used to determine how the interaction of the various magnitude and frequency regimes might produce a distinctive sedimentary record consideration of sandur architecture and stratigraphy shows that the main controls on the sedimentary record of proglacial regions are the discharge magnitude and frequency regime sediment supply the pattern of glacier advance or retreat and proglacial topography a model of sandur development is suggested which shows how discharge magnitude and frequency in combination with sandur incision and aggradation controlled by glacier advance and retreat can control sandur stratigraphy

de icing progression of ice cored moraines in a humid subpolar climate kotlujokull iceland modes and rates of de icing ice cored moraines under humid subpolar conditions have been determ ined for two dead ice fields of different age representing a mature and a final stage of collapse in the kotlujokull terminus region south iceland the melting processes considered are backwasting defined as the lateral retreat of near vertical ice walls or steep ice cored slopes and downwasting defined as the thinning of the ice core by melting along the top and bottom surfaces in the mature stage of collapse where there is less than 1 m of sediment cover major faces of ice exposed for rapid melting are ordinarily significant and long lived due to intense precipitation in this fully ice cored terrain the predominating processes are backwasting of exposed ice walls and downwasting by bottom melt each contributing to the annual surface lowering of about 0 5 m or 35 the total annual surface lowering melt rate due to all processes averages 1 4 m in those parts of the fully ice cored dead ice field

subglacial till formation sedimentary characteristics and classification we review the major subglacial till forming processes as presently understood by glacial researchers and define the parameters within which tills are produced and reconcile them with sedimentary end members processes of deformation flow sliding lodgement and ploughing coexist at the base of temperate glacier ice and act to mobilize and transport sediment and deposit it as various end members ranging from glacitectonically folded and faulted stratified material to texturally homogeneous diamicton the dominance of any one subglacial process varies both spatially and temporally giving rise to the possibility that a till or complex till sequence contains a superimposed signature of former transportation deposition at the ice bed interface we recommend that while glacial geologists and geomorphologists should be able to recognize the sedimentary imprints of various subglacial processes genetic fingerprinting of subglacial tills should be less process specific and till classification must reflect the range of products encompassed by the subglacial till production continuum glacial geologists can presently unequivocally identify a glacitectonite rock or sediment that has been deformed by subglacial shearing deformation but retains some of the structural characteristics of the parent material b subglacial traction till sediment deposited by a glacier sole either sliding over and or deforming its bed the sediment having been released directly from the ice by pressure melting and or liberated from the substrate and then disaggregated and completely or largely homogenised by shearing and support the theoretical case for c melt out till sediment released by the melting of stagnant or slowly moving debris rich glacier ice and directly deposited without subsequent transport or deformation because observations on contemporary glaciers reveal that their beds are most likely to be mosaics of deformation and sliding and warm based and cold based conditions the patterns of which change temporally and spatially it is extremely unlikely that subglacial till end members in the geological record will be anything but hybrids produced by the range of processes operative in the subglacial traction zone

the tekapo glacier new zealand during the last glacial maximum an active temperate glacier influenced by intermittent surge activity abstract quaternary glaciations have created impressive landform assemblages that can be used to understand palaeo glacier extent character and behaviour and hence past global and local glacier forcings however in the southern hemisphere and especially in new zealand the quaternary glacial landform record is relatively poorly investigated with regard to glaciological properties in this study a 1 m digital elevation model dem was generated from airborne lidar data and supplemented with aerial imagery and field observations to analyse the exceptionally well preserved glacial geomorphology surrounding lake tekapo new zealand we describe a rich suite of last glacial maximum lgm and recessional ice marginal subglacial supraglacial glaciofluvial and glaciolacustrine landform assemblages these represent two landsystems comprising i fluted till surfaces with low relief push moraine ridges and ii crevasse squeeze ridges zig zag eskers and attenuated lineations the former landsystem records the behaviour of an active temperate glacier and the latter landsystem which is superimposed upon and inset within the former strongly suggests intermittent surge phases the two landsystem signatures indicate a sequential change in ice marginal dynamics during recession that was likely to have been partially non climatically driven overall we present the first evidence of surge type glacier behaviour in new zealand

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

mid and late holocene vegetation surface weathering and glaciation fjallsjokull southeast iceland a natural section at the southern margin of fjallsjokull in southeastern iceland provides evidence of a mid holocene land surface that has been deformed by little ice age glaciation deformation is inter preted as compression around coarse gravel core and extension along deformable silts restoration of the original sedimentary units reveals a succession of lake sediments and fan gravels with pollen and wood macro fossil remains preserved in the lake silts vegetational and palaeogeographical reconstruction indicates that small ponds existed at the site surrounded by a mosaic of birch woodland and grassland radiocarbon dates spanning a period from 4200 to 3750 bp indicate that the basins were infilled rapidly over a period of about 500 years by stream sedimentation colour changes in the upper part of the sediment sequence and relatively high frequency dependent magnetic susceptibility values on the clay fractions of the sediments indicate that iron minerals were mobilized and oxidized in response to