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

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

inferred glacio eustatic control for high frequency depositional sequences of the plio pleistocene kazusa group a forearc basin fill in boso peninsula japan abstract the plio pleistocene forearc basin fill of the kazusa group as much as 3000 m thick is represented by a series of marine environments ranging from deep sea basin plain to shallow sea it developed during about 2 4 to 0 45 ma and is well exposed in the boso peninsula japan chronostratigraphic resolution of the kazusa group is partly within about 0 05 m y based on the combination of fission track dating of volcanic ash layers and bio and magneto stratigraphy many volcanic ash layers are intercalated in the kazusa group and provide distinct chronostratigraphic surfaces within the heterogeneous lithologies detailed outcrop studies on depositional facies discontinuities and lateral terminations of volcanic ash layers allow high resolution sequence stratigraphic interpretation of the kazusa group seventeen depositional sequences were identified in the kazusa group each depositional sequence was tentatively correlated with the stable oxygen isotope sea level index integrated with the age framework of the kazusa group this correlation indicates that frequencies of the depositional sequences can be estimated to be in the range of 0 2 0 02 m y and are within fourth and fifth order stratigraphic cyclicities depositional sequences constitute third order transgressive and highstand sequence sets and the kazusa group is interpreted to represent a third order composite sequence with a duration of about 1 95 m y development of the third order composite sequence was also controlled by an overall rise and fall of glacio eustatic sea levels overprinted by tectonic events related to fluctuations in oceanic plate motion which occurred at about 2 6 ma and 0 5 ma respectively

controlled moraine development and debris transport pathways in polythermal plateau icefields examples from tungnafellsjokull iceland a modern landsystems analogue for plateau icefield glaciation is presented based upon tungnafellsjokull in the arid cold interior of iceland landform mapping and intensive clast form analysis on three separate forelands occupied during the little ice age reveal variability in the morphology of moraines and the degree of clast modification which is interpreted as a function of the complex interplay between a the efficacy of glacial erosion b passive versus active debris transfer mechanisms and c the volume of debris provision for ice marginal freeze on mechanisms a steep outlet bounded by rockwalls produced a landform assemblage and debris transport signature typical of valley glaciers whereas two unconfined outlets produced a landform sediment imprint typical of polythermal conditions this comprises subglacial bedforms relating to the initiation of warm based ice by strain heating below icefalls at the plateau edge terminating at arcs of ice cored controlled moraine representative of frozen snout conditions patterns in clast form data on the unrestricted forelands reflect the characteristics of glacier dynamics and thermal regimes at the margin of a plateau icefield where bedrock steps of sufficient size to initiate strain heating and bedrock abrasion and plucking are located only a short distance from the marginal freeze on conditions of a snout creating debris rich folia and controlled moraine additional englacial debris may well have been carried to the glacier margin through the development of ogives and englacial thrusting at the base of the icefall thereby explaining the occurrence of striae on clasts that have otherwise been little modified by glacial abrasion copyright 2010 john wiley sons ltd

some geological implications of average quaternary glacial conditions analyses of quaternary landscape evolution tend to focus on events associated with culminations of glacial and interglacial ages but for most of quaternary time environments were intermediate in character average quaternary glacial conditions based on assessment of the marine isotope record approximated those near the stage 2 stage 1 transition and during substages 5b and 5d isotope stages 3 and 4 and substages 5a d lie within one standard deviation of the mean value under average glacial conditions ice sheets lying over northern north america and europe were much more contracted than their full glacial counterparts and the distribution of mountain glaciers reflected a snowline depression of some 500 m geomorphic processes operating under average quaternary conditions contributed importantly to landscape evolution examples of landscapes that may represent such average conditions include cirques and fluvial deposits of the pacific northwest the fjords and strandflat of western norway and atolls of the tropical oceans by examining the geologic record from the perspective of average conditions rather than those of climatic extremes added insight can be gained regarding the evolution of quaternary landscapes

debris transport in a temperate valley glacier haut glacier d arolla valais switzerland hambrey m j goodsell becky glasser n f 2005 debris transport in a temperate valley glacier haut glacier d arolla valais switzerland journal of glaciology 51 172 pp 139 146

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

linking outcrop analogue with flow simulation to reduce uncertainty in sub surface carbon capture and storage an example from the sherwood sandstone group of the wessex basin uk modelling the behaviour of carbon dioxide co2 injected into sub surface reservoirs as part of carbon capture and storage ccs strategies is often performed using models that incorporate very limited geological detail particularly at the subseismic metre to decametre scale those modelling studies that incorporate varying degrees of geological realism show the inherent risks and uncertainties that can result from neglecting heterogeneity and reservoir caprock topography along the migration path of an injected co2 plume a key problem is that detailed geological data are often not available for the relatively deep saline aquifers that are an important target for ccs deep saline aquifers fall between the relatively data rich environments of shallow freshwater aquifers and hydrocarbon reservoirs and it is in these settings that outcrop analogues may play an important part in reducing the risks and uncertainties associated with ccs this study uses an example from the sherwood sandstone group otter sandstone formation of the wessex basin to show how an outcrop study can impart a much greater understanding of heterogeneity in critical reservoir caprock zones here the transition from the sherwood sandstone group fluvial sandstone reservoir to the mercia mudstone group playa lacustrine mudstone seal is not simple but includes a major change in fluvial style that introduces considerable heterogeneity at the top of the reservoir the study shows how laser scanned outcrop can be used to rapidly construct static geological models that are taken through to flow simulations in combination the use of appropriate outcrop analogues and flow modelling can reduce the risks and uncertainties associated with ccs

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

a younger dryas plateau icefield in the monadhliath scotland and implications for regional palaeoclimate a record of younger dryas glaciation in scotland is well established however the role of the monadhliath a significant plateau area extending over 840 km2 in central scotland has never been investigated systematically we present the first systematic glacial geomorphological mapping across the whole region which has led to the identification of hitherto unrecorded glacial and associated landforms the spatial distribution of these landforms indicates that the last phase of glaciation in the area was that of a local plateau icefield in addition a clear morphostratigraphical signature provides a strong indication that the icefield dates to the younger dryas 12 9 11 7 ka which is supported by numerical ages in the southeast of the study area based on the geomorphological evidence and 2d glacier surface profile modelling a 280 km2 icefield is reconstructed a novel approach is introduced to quantify plateau icefield thickness for equilibrium line altitude ela and palaeoprecipitation calculations resulting in greater overall data confidence compared to traditional reconstruction methods the ela for the whole icefield is calculated to be 714 25 m whilst the elas of individual outlet glaciers range from 560 m in the west to 816 m in the east demonstrating a significant w e precipitation gradient across the region during the younger dryas these elas compare well with those calculated for younger dryas ice masses reconstructed in neighbouring regions and are in good agreement with overall precipitation patterns suggested for scotland during this time whilst the total amount of precipitation calculated from these elas is highly dependent on the method used irrespective of this the study suggests a more arid younger dryas climate in the region compared to the present day

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

variability of the path of the kuroshio ocean current over the past 25 000 years the kuroshio current is the strong northwestern component of the subtropical north pacific ocean gyre and advects a large amount of heat from the tropics to northern mid latitudes the kuroshio has bimodal stationary flow patterns with small and large meander paths east of central japan1 2 which switch on annual and decadal timescales3 4 these switches seem to be caused by changes in current velocity and volume transport of the north equatorial current that are associated with variations in the trade wind intensity in the eastern equatorial north pacific ocean5 6 here we present alkenone derived sea surface temperature records at multicentennial resolution from sediment cores from the nishishichitou ridge off central japan these 25 000 year records show that the kuroshio path has also fluctuated on millennial timescales this variability resembles that of the subtropical high pressure of the north pacific reconstructed from terrestrial pollen distributions water levels in north american lakes and marine micropalaeontological records7 together these data indicate that climate variability off central japan over the past 25 000 years may be part of a circum pacific phenomenon reflecting the rate of subtropical surface circulation in the north pacific ocean

sedimentology of latero frontal moraines and fans on the west coast of south island new zealand exposures through the lgm latero frontal moraine loops at sites along the west coast of south island new zealand reveal a depositional environment that was dominated by the progradation of steep fronted debris flow fed fans manifest in crudely stratified to massive diamictons arranged in sub horizontal to steeply dipping clinoforms and containing discontinuous bodies of variably sorted stratified sediment lfa 1 the fans were constructed by debris covered glaciers advancing over outwash plains as recorded by well stratified and horizontally bedded gravels sands and diamicts lfa 0 the ice contact slopes of the fans are offlapped by retreat phase deposits in the form of glacilacustrine depo centres lfa 2 which record the existence of moraine dammed lakes interdigitation of lake rhythmites and subaerial to subaqueous sediment gravity flow deposits documents intense debris flow activity on unstable moraine fan surfaces glacier readvances in all catchments are documented by glacitectonic disturbance and localized hydrofracturing of lfa 2 followed by the emplacement of schist dominated debris flow fed fans lfa 3 inside and over the top of the earlier latero frontal moraine fan loops contorted and disturbed bedding in lfa 3 reflects its partial deposition in supraglacial positions clast lithologies in lfas 1 and 3 reveal that two distinct transport pathways operated during moraine construction with an early period of latero frontal fan construction involving mixed lithologies and a later period of ice contact supraglacial fan construction dominated by schist lithologies from the mountains these two periods of deposition were separated by a period of moraine abandonment and paraglacial reworking of ice contact slopes to produce lfa 2 the occurrence of lfa 3 at all sites indicates that the glacier readvance phase responsible for its deposition was not localized or glacier specific and involved the transfer of large volumes of schist possibly due to rock slope failures onto glacier surfaces the absence of any sediment that could be unequivocally classified as subglacial till reflects the dominance of debris flow and glacifluvial processes in latero frontal moraine construction in this hyper humid west coast setting

glacial landsystems of satujokull iceland a modern analogue for glacial landsystem overprinting by mountain icecaps mapping of the surficial geology and geomorphology of the satujokull foreland of the northern hofsjokull ice cap in central iceland provides a clear signature of glacial landsystem overprinting as a result of complex glacier behaviour during the historical period landsystem 1 comprises a wide arc of ice cored moraine and controlled ridges lying outside fluted and drumlinized terrain and is indicative of polythermal conditions this landform assemblage commonly marks the historical little ice age maximum limit on the forelands of upland icefields in the arid interior of iceland and is therefore a record of climatically driven glacier advance landsystem 2 contains most of the diagnostic criteria for the surging glacier landsystem and records two separate surges by the western margin of satujokull in the period since the attainment of the little ice age maximum advance the occurrence of landsystem 2 is significant because satujokull has not been previously regarded as a surging glacier even though other outlets of hofsjokull are prone to surging landsystem overprinting especially in response to changing thermal regimes and or glacier dynamics and particularly by different flow units in the same glacier is rarely reported but is crucial to the critical application of modern landsystem analogues to quaternary palaeoglaciological reconstruction

numerical modeling of glacial erosion and headwall processes in alpine valleys abstract how rock relief is developed by glacial erosion in alpine landscapes is a key question in understanding the controls on mountain range topography any generation of relief by glaciers at the highest elevations in mountain ranges can affect the distribution of precipitation in alpine landscapes creating feedbacks between glacier mass balance and glacial erosion relief production at high elevation mountain crests is addressed using a numerical model that incorporates glacier dynamics and subglacial erosion as well as relevant hillslope processes blowing snow from a valley bounding plateau and avalanching onto the accumulation zone of the glacier is included in the model furthermore temperature dependent frost cracking is used as a proxy for headwall backwearing the parameterization of subglacial erosion produces about 500 m of erosion over the 400 ka of each numerical simulation in steady and varying climate scenarios valley floors flatten as headwalls increase in height and retreat headward over time headwall slopes increase in simulations in which quarrying is explicitly incorporated rates of quarrying are high near the base of the headwall increasing headwall length and slope as a result of valley floor lowering high rates of subglacial erosion and production of headwall relief also result when elastic flexural uplift occurs in response to mass unloading small overdeepenings form at the base of the headwall in steady climate simulations when the glacier is small at the end of the model run while the final profiles are relatively insensitive to the erosion rule used quarrying is most effective near the head of the glacier whereas rates of abrasion reflect the instantaneous pattern of integrated ice discharge or ice flux in simulations in which cirques are formed the equilibrium line altitude is hundreds of meters above the cirque floor however the time averaged horizontal position of the equilibrium line corresponds well with the downvalley position of the cirques

formation of band ogives and associated structures at bas glacier d arolla valais switzerland hambrey m j glasser n f goodsell becky 2002 formation of band ogives and associated structures at bas glacier d arolla valais switzerland journal of glaciology 48 161 pp 287 300 keywords europe switzerland geometrical structure three dimensional structure radar observation glacier crevasse models debris interface basal ice glacial tongue stratification glacier

major end moraines of younger dryas age on wollaston peninsula victoria island canadian arctic implications for paleoclimate and for formation of hummocky moraine some of the most extensive and massive end moraines of younger dryas age 11 10 14c ka bp yet recognized in north america occur on wollaston peninsula of victoria island on the western part of the peninsula numerous closely spaced end moraines formed in the interval starting 11 100 100 radiocarbon years ago and ending about 10 500 10 200 years ago net recession was generally slow throughout and was punctuated by moraine building and at least two readvances recession is mapped with a resolution that is approximately decadal the moraines form an orderly nested succession and are consistently associated with westward shedding of meltwater which formed a sequence of marine limit deltas we lack firm independent proxy climate evidence needed to assess whether these moraines formed because of cold younger dryas climate rather than because of controls such as topographic setting and water depth but climatic control seems probable the moraines evidently retain glacier ice cores as do most similarly

isotope evidence of paleo el nino southern oscillation cycles in loess paleosol record in the central united states abstract the 13 c of soil carbonate in rhizoconcretions collected from aloess paleosol sequence in the central united states indicates that grow ing season c 3 c 4 plant ratio oscillated by 35 on a 900 200 yr timescale during the late wisconsinan glaciation the pattern appears inphase with advance and retreat of the southern margin of the lauren tide ice sheet suggesting influence by paleo el nino southern oscilla tion cycles the 13 c of soil organic matter indicates that the annual av erage c 3 c 4 plant ratio oscillated only by 18 with a periodicity of450 100 yr and closely matched the cyclic pattern of loess paleosollayers it suggests a periodic enhancement of the penetration of thegulf of mexico air over the region during this time keywords carbon isotope loess paleosol glacial phase paleo enso cycle introduction the el nino southern oscillation enso causes global scale climateanomalies the el nino and la nina are two counterparts of enso whichare associated with warming and cooling in surface water in the eastern trop ical pacific on the basis of modeling studies cane 1998 cane andclement 1999 and clement and cane 1999 proposed that frequency in tensity and duration of long term el nino or la nina intervals have oscil lated on a millennial time scale during the past 150 k y they proposed thatduring glacial periods these long term enso cycles might alter the globalclimate via atmospheric teleconnections in which el nino dominant inter vals may cause retreat and la nina dominant intervals may cause advanceof the southern margin of the laurentide ice sheet the enso sensitive re gions currently in north america partially overlap the area that was coveredby the laurentide ice sheet during the last glaciation fig 1 modernla nina conditions cause heavy snowfall whereas el nino conditions re duce winter precipitation in these regions http www ogp noaa gov enso it is reasonable to assume that la nina or el nino dominant intervals mighthave controlled advance and retreat of the southern margin of the laurentideice sheet if these intervals oscillate on a long term time scale in this paper we use stable isotope ratios from a loess paleosol exposure in the centralunited states to seek evidence for millennial scale paleo enso cycles

geomorphology and sedimentology of surging glaciers a land systems approach the identification of surging glaciers and ice streams in glaciated landscapes is of major importance to the understanding of ice sheet dynamics and for reconstructing ice sheets and climate no single landform or diagnostic criterion has yet been found with which to identify surging glaciers a surging glacier land system model is constructed using observations and measurements from contemporary surging glacier snouts in iceland svalbard u s a and canada for differentiating ancient surging margins from other non surging palaeoglaciers this integrates the suite of landforms sediments and stratigraphy produced at surging glacier margins landforms produced during surging include thrust moraines concertina eskers and subglacial crevasse squeeze ridges sedimentary sequences are usually characterized by multiple stacked diamictons and stratified interbeds which display severe glaciotectonic contortion and faulting hummocky moraine comprising interbedded stratified sediments and mass flow diamictons has also been associated with surge margins where large quantities of supraglacial and englacial debris entrained during the surge event have melted out in situ an example of the application of the land system model is presented for east central alberta canada a surging palaeo ice stream is identified within this part of the southwestern laurentide ice sheet where thrust block moraines crevasse squeeze ridges flutings hummocky moraine and glaciotectonized sediments are juxtaposed

high frequency depositional sequences of the upper part of the kazusa group a middle pleistocene forearc basin fill in boso peninsula japan abstract a middle pleistocene forearc basin fill of the upper part of the kazusa group is represented by slope to shelf sediments and is well exposed in the boso peninsula of japan the slope to shelf sediments are a northeasterly prograded clastic wedge as much as 700 m in maximum thickness and include many volcanic ash layers mapping of volcanic ash layers together with the interpretation of depositional facies permits identification of stratal terminations and spatial and temporal variations of depositional environments this allows sequence stratigraphic analysis of the slope to shelf sediments of the upper part of the kazusa group six depositional sequences were identified in the upper part of the kazusa group by correlating each depositional sequence with the stable oxygen isotope sea level index integrated with the age framework for the upper part of the kazusa group ca 0 72 0 45 ma periodicity of the depositional sequences of the upper part of the kazusa group can be estimated at about 20 000 to 90 000 years the high frequency depositional sequences are interpreted to be a result of interaction between high sedimentation rate in the forearc basin and high rate of glacio eustatic sea level changes during the middle pleistocene

magnetostratigraphy of the sherwood sandstone group lower and middle triassic south devon uk detailed correlation of the marine and non marine anisian the sherwood sandstone group in south devon consists of the budleigh salterton pebble beds and the otter sandstone formation the otter sandstone formation comprises four lithostratigraphic sub units from the base labelled a d and contains tetrapods corresponding to the perovkan land vertebrate faunachron and is consequently a key european non marine anisian succession a total of 181 palaeomagnetic specimens from 92 horizons were measured to determine the palaeomagnetic signal the magnetic properties and characteristic remanence is predominantly carried by haematite most of which probably formed early in the depositional and diagenetic history the lower part of the sherwood sandstone group budleigh salterton pebble beds and otter sandstone formation unit a lower part of unit b has predominantly normal polarity magnetozones bs1 bs2 and bs3n with three thin reversed polarity magnetozones the lower part of unit b to the lower part of unit c of the otter sandstone formation is predominantly reverse polarity magnetozones bs3r bs4 and bs5 but includes three short normal polarity intervals the upper ca 50 m of unit c shows a mix of normal and reverse polarity bs6 bs7 with normal dominating the ca 15 m thick unit d is entirely of normal polarity bs8n the magnetostratigraphy allows unambiguous comparison with conodont and ammonite calibrated magnetostratigraphies from elsewhere in europe these show that the bs2 and bs3n magnetozones of the otter sandstone formation are lower aegean to middle pelsonian lower to middle anisian the bs3r to bs5r magnetozone interval is middle pelsonian to lower illyrian middle to upper anisian and the bs6 to bs8n magnetozone interval is middle illyrian to lower fassanian the top of unit d is correlated to an interval in the middle of the nevadites zone close to the anisian ladinian boundary consequently the otter sandstone formation correlates with the muschelkalk in the polish basin but is equivalent to only part of the germanic basin muschelkalk the continuous magnetostratigraphy from the sherwood sandstone group provides additional details of the polarity pattern through the pelsonian to illyrian interval which appears to be lacking in discontinuous marine sections a synthesis of adjacent european sedimentary basins in combination with the magnetostratigraphy suggests that the budleigh salterton pebble beds are probably late spathian to lower aegean

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

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

millennial scale climate change and oceanic processes in the late pliocene and early pleistocene we generated 200 500 year resolution records of oceanic processes in the north atlantic ocean drilling program site 983 60 24 n 23 38 w 1983 meters water depth for intervals in the latest pliocene 1 86 1 93 ma and the earliest pleistocene 1 75 1 83 ma in order to examine the linkages between millennial scale variations in the ocean and background glacial interglacial climate change within glacial intervals we find evidence for variations similar to those observed in the late pleistocene we find discrete ice rafted debris ird events that reoccur every 2 5 kyr these events are preceded by a short cooling and accompanied by a reorganization of glacial deep waters the timing of ird events in the late pliocene and early pleistocene intervals is similar to that of dansgaard oeschger cycles but we find no ird events comparable in timing to late pleistocene heinrich events although interglacial intervals are much more stable we do find evidence for low amplitude variations in deep water properties that reoccur every 2 kyr within interglacial intervals the similarity between our late pliocene early pleistocene records and late pleistocene records implies that the mechanism driving millennial scale variations cannot be uniquely attributed to the strongly nonlinear linkage between climate and insolation and the large ice sheets of the late pleistocene

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

millennial to decadal scale fluctuation in the paleo kuroshio current documented in the middle pleistocene shelf succession on the boso peninsula japan abstract millennial century and decadal scale cyclicities were identified in a transgressive shelf succession of the middle pleistocene ca 0 7 ma on the boso peninsula japan the shelf succession consists mainly of a sandridge complex and associated outer shelf deposits the deposition was interpreted to have been controlled by fluctuation in speeds and paths of the paleo kuroshio current in general the modern kuroshio current approaches the southern coasts of the boso peninsula in response to its large meander that is interpreted to respond to the el nino episodes depositional cycles in the kuroshio current controlled shelf succession are interpreted to document high frequency paleoclimatic oscillation in the equatorial pacific region during the middle pleistocene time the finding indicates that high frequency paleoclimatic instability that has been strongly expressed in the upper pleistocene successions in the north atlantic region was pervasive in time and space back to the middle pleistocene

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

styles of sedimentation beneath svalbard valley glaciers under changing dynamic and thermal regimes glacier beds provide crucial information concerning past and present ice dynamics and thermal regime in this paper we present structural and sedimentological data from four valley glaciers austre lovenbreen midtre lovenbreen vestre lovenbreen and austre broggerbreen on broggerhalvoya nw spitsbergen the main focus of this paper is midtre and austre lovenbreen two typical high arctic land based polythermal valley glaciers the former has a long record of documentation regarding its response to twentieth century climatic warming structural mapping on the glacier surface and analysis of sediments in the proglacial area of midtre lovenbreen indicate that the dynamic regime and thermal structure of the glacier have changed through time dynamically midtre lovenbreen was once heavily crevassed and relatively fast moving but now is virtually crevasse free and slow moving the sedimentary record indicates that extensive areas of this glacier were wet based when it was in a more advanced state probably at its neoglacial maximum late nineteenth early twentieth centuries during this advance a thin deforming layer of diamicton commonly fluted was draped over the existing morphology in the presently exposed proglacial area this morphology consisted of large streamlined ridges aligned parallel to ice flow erosion of the underlying bedrock appears to have been limited radio echo soundings of the glacier show that at present it is characterized by a polythermal basal thermal regime with wet based subglacial conditions only beneath its thicker parts modification of the bed is limited under this thermal regime and as a result the supraglacial environment dominates modern sedimentation comparative studies on austre lovenbreen which also is probably polythermal indicate similar sedimentary characteristics and facies associations although here there are much more extensive areas of striated bedrock indicative of former basal sliding in contrast both austre broggerbreen and by analogy vestre lovenbreen are known to be predominantly cold based collectively these four glaciers suggest a trend of glacier recession and thinning accompanied by a change in thermal regime from predominantly wet based through partly frozen to completely frozen this study suggests that svalbard valley glaciers have several dynamic modes and that glaciers switch between these modes largely as a reaction to changes in mass balance

quaternary geology of the duck hawk bluffs southwest banks island arctic canada a re investigation of a critical terrestrial type locality for glacial and interglacial events bordering the arctic ocean duck hawk bluffs southwest banks island is a primary section 8 km long and 60 m high in the western canadian arctic archipelago exposing a long record of quaternary sedimentation adjacent to the arctic ocean a reinvestigation of duck hawk bluffs demonstrates that it is a previously unrecognized thrust block moraine emplaced from the northeast by laurentide ice previous stratigraphic models of duck hawk bluffs reported a basal unit of preglacial fluvial sand and gravel beaufort fm forested arctic overlain by a succession of three glaciations and at least two interglacials our observations dismiss the occurrence of preglacial sediments and amalgamate the entire record into three glacial intervals and one prominent interglacial the first glacigenic sedimentation is recorded by an ice contact sandur containing redeposited allochthonous organics previously assigned to the beaufort fm this is overlain by fine grained sediments with ice wedge pseudomorphs and well preserved bryophyte assemblages corresponding to an interglacial environment similar to modern the second glacial interval is recorded by ice proximal mass flows and marine rhythmites that were glacitectonized when laurentide ice overrode the site from amundsen gulf to the south sediments of this interval have been reported to be magnetically reversed 780 ka the third interval of glacigenic sedimentation includes glacifluvial sand and gravel recording the arrival of laurentide ice that overrode the site from the northeast island interior depositing a glacitectonite and constructing the thrust block moraine that comprises duck hawk bluffs sediments of this interval have been reported to be magnetically normal 780 ka the glacitectonite contains a highly deformed melange of pre existing sediments that were previously assigned to several formally named marine and interglacial deposits resting in an undeformed sequence in contrast the tectonism associated with the thrust block moraine imparted pervasive deformation throughout all underlying units highlighted by a previously unrecognized raft of cretaceous bedrock during this advance laurentide ice from the interior of banks island coalesced with an ice stream in amundsen gulf depositing the interlobate sachs moraine that contains shells as young as 24 cal ka bp late wisconsinan during deglaciation meltwater emanating from these separating ice lobes deposited outwash that extended to deglacial marine limit 11 m asl along the west coast of banks island our new stratigraphic synthesis fundamentally revises and simplifies the record of past quaternary environments preserved on southwest banks island which serves as a key terrestrial archive for palaeoenvironmental change

debris transport by loch lomond readvance glaciers in northern scotland basin form and the within valley asymmetry of lateral moraines moraines in six cirques in northern scotland are shown to be asymmetrically developed being larger below north or east facing valley sides moraine asymmetry is strongly correlated with the distribution of free faces in the valleys a relationship that is interpreted as the result of variation in slope retreat rates analysis of clast form and roundness demonstrates that following initial release from bedrock debris entered both passive high level glacial transport and tractive transport at the ice bed interface the importance of glacier velocities and medial moraines on debris flux is discussed consideration is also given to the implications of process asymmetry to long term landform development

comment on the permian triassic transition and the onset of mesozoic sedimentation at the northwestern peri tethyan domain scale palaeogeographic maps and geodynamic implications by s bourquin a bercovici j lopez gomez j b diez j broutin a ronchi m durand a arche b linol and f amour palaeogeography palaeoclimatology palaeoecology 299 2011 265 280 abstract the recent paper by bourquin et al 2011 describes the regional palaeogeographic evolution of the late permian to middle triassic on a pan european scale whilst useful data and interpretations are provided for their southern and intra variscan belt domains additional well and seismic data from the central and northern north sea and the atlantic margin region together with results from recent publications allow us to refine and improve their interpretation of their northern domain the presence of a regional unconformity at the permian triassic boundary with only localised induan sedimentation is less clear in the northern region where multiple extensional events through late permian and triassic time led to the development of localised footwall and rift flank unconformities as arctic rifting propagated southwards and entered the north sea and the atlantic margin regions the hardegsen unconformity may be locally identifiable in the southern portion of the northern domain but again forms one of a number of unconformities marking the onset of rifting data from the northern domain suggest that early triassic aeolian activity was ubiquitous on the distal fringes of terminal fluvial systems but with no evidence of the discrete episode of increased aridity in the smithian identified in the south the onset of vegetation cover in the northern domain was also more diachronous in this region appearing in the central north sea at approximately the same time as muschelkalk flooding of the adjacent southern permian basin and later in basins further to the north in most cases the middle triassic fluvial systems in the north were terminal in nature failed to discharge into marine basins and were not exorheic in character their advance and retreat was independent of sea level fluctuations or the presence of a marine water body and fluvial expansion and retreat aeolian reworking and vegetation cover appear to have been linked to catchment runoff the disconnect with the observations to the south may be in part a product of the more northern latitudinal position of these systems or at least that of the headwaters of the fluvial drainage

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

distribution and origin of subaqueous dunes on the shelf of japan abstract subaqueous dunes are found on the shelf around the japanese islands mainly in the straits between the islands some of the dunes are formed by ocean currents and others by tidal currents combined flows also produce shoreparallel coarse grained bands and medium dunes on the inner shelf the dynamics of these bedforms was examined using repeated observations of bedforms and by comparing the hydraulic conditions required to form the bedforms with the existing oceanographic conditions the study indicates that most of bedforms are active but the volumes of sediment transported are too small to form the sand bodies which underlay the large dunes seismic records show these sand bodies occur on the erosional surfaces formed after the last glacial maximum it is suggested that most of the sand bodies were formed during the postglacial transgression

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 glacial sedimentology and geomorphological evolution of an outwash head moraine dammed lake south island new zealand extensive exposures through the glacial landforms around southern lake pukaki new zealand comprise seven lithofacies lfs 1 7 lfs 1 3 are grouped together as lfa 1 pukaki member and record pulsed subaqueous grounding line fan progradation cohesionless debris flows underflow activity and rhythmite deposition by suspension settling iceberg rafting of dropstones and pulsed traction current activity localized disturbance of these deposits by glacitectonic deformation and multi generational hydrofracture fills records minor readvances by the glacier snout and the emplacement of a glacitectonite lf 4 derived from cannibalization of glacilacustrine sediments lfs 4 6 are grouped together as lfa 2 twizel member and record direct glacigenic deposition of glacitectonite lf 4 subglacial traction till lf 5 and supraglacially dumped boulder rubble lf 6 stratigraphic relationships between lfa 1 with lfa 2 record the oscillatory behaviour of the former tasman glacier snout when it formed a calving margin in a proglacial and locally supraglacial lake dammed by a glacitectonically disturbed outwash head and lateral moraine ridges this is entirely consistent with the landform sediment record of its coeval terrestrial margins where flutings and push moraines are diagnostic of active temperate glacier recession from a glacially overridden outwash head the latter being recorded by the vertically stacked sub horizontally bedded and coarse grained gravels of lf 7 waitaki member previous proposals that late pleistocene lake damming was initiated by an ice cored moraine arc appear unfounded because the glacilacustrine deposits only lie above the altitude of the outwash head lateral moraine arc in locations where they have been glacitectonically compressed alternatively it is proposed that the overdeepened subglacial topography was produced by the construction of an outwash head leading to a glacilacustrine sediment sink which operates at times when the expanded tasman glacier actively retreats from the outwash head apex the changing landsystem imprint related to the shrinkage of the tasman glacier records spatio temporal landsystem change involving evolution from a coupled landsystem to a moraine dammed to an uncoupled landsystem

debris entrainment and transfer in polythermal valley glaciers hambrey mj bennett mr dowdeswell ja et al 1999 debris entrainment and transfer in polythermal valley glaciers journal of glaciology 45 149 69 86 published 1999

structures and textures in triassic braided stream conglomerates bunter pebble beds in the sherwood sandstone group north staffordshire england in the northern parts of the needwood and stafford eccleshall basins england the pebble beds of the sherwood sandstone group contain thick successions of texturally mature fluvial pebble cobble conglomerates which are organized into either horizontal or cross stratified sets the horizontally lying sets generally coarser grained and more poorly sorted than the cross bedded sets are usually disorganized and either matrix or clast supported although thin lenses of well sorted occasionally openwork units interpreted as falling stage phenomena are often present the cross stratified conglomerates have foresets exhibiting remarkable textural organization with a coarse bimodal sometimes matrix supported part grading upwards or being abruptly overlain by a finer well sorted occasionally openwork part and finally capped by sandstone these rhythmic textural changes are attributed partly to an avalanche process at high stage and partly to falling stage conditions the most common types of vertical association are thick successions of horizontally bedded conglomerates up to 20 m and sequences of an upwards coarsening nature 2 12 m in which cross stratified sets are overlain by flat lying sets the environment of deposition of the gravels is interpreted as one in which water depths at high stage were greater than depths in most modern braided stream plains proglacial or alluvial fan but shallower than depths associated with the pleistocene catastrophic floods from which texturally mature giant gravel bars have been recorded recent braided streams with relatively confined channels and considerable bar channel relief are better analogues in particular medial or mid channel bars with a two tier structure subaqueous and partly emergent portions may explain the upward coarsening sequences in which horizontally lying conglomerates overlie cross stratified conglomerates the thicker sequences of horizontally stratified conglomerates represent proximal longitudinal bar deposits sheets of pebbly sandstone and argillaceous sandstone lying between the conglomerates and commonly occurring towards the top of the succession largely represent deposition from sandwaves and dunes finer interbedded argillaceous sandstones siltstones and mudstones are interpreted as overbank and waning flood deposits basin forming tectonism of increasing intensity probably caused the initial coarsening upwards of the lower part of the succession whilst more stable tectonic conditions and decreasing relief on the margins of the basins and in the areas of provenance in the midlands and the hercynides account for the upwards fining of the upper part of the succession

influences of eolian and pedogenic processes on the origin and evolution of desert pavements well developed desert pavements are present above eolian deposits that mantle flows of the cima volcanic field located in the mojave desert california soil stratigraphic data and geochemical data demonstrate that eolian and pedogenic processes play major roles in the evolution of these pavements eolian dust 1 accelerates mechanical fragmentation of flow rock providing the source material for pavements and 2 accumulates slowly below basaltic colluvium in flow depressions eventually promoting development of cumulate soils below the evolving stone pavement an increase in dust flux during the holocene has raised ancient pleistocene pavements as much as 20 cm above the former land surface the results of our studies demonstrate for the first time that most desert pavements do not form by deflation by overland flow or by upward migration of stones through a slowly formed clayey argillic horizon desert pavements are born and maintained at the surface

the evolution of holocene reg gravelly soils in deserts abstract reg soil is an aridisol developed upon a stable alluvial surface composed of sand to coarse gravel the objectives of the present study were 1 to examine the initial evolution of reg soil properties with time 2 to assess and explain the rates of development of different properties 3 to establish the suitability of different soil properties for relative age dating the time dependent soil properties examined were 1 mechanical weathering of surficial rocks and desert pavement evolution 2 chemical and biological weathering of surficial rocks 3 the thickness of soil profiles and soil horizons 4 soil texture in the different horizons 5 salts and gypsum distribution and concentration in different soil horizons 6 degree of mechanical weathering of gravel in c horizons fifteen successive surfaces of the nahal wadi ze elim sequence of alluvial fans were selected for study dead sea region israel under an extremely arid climate the sequence is of holocene age 14 000 years b p to recent the main conclusions are 1 reg soils develop rather fast in several 10 3 years since their initiation however the various soil properties developed at different rates 2 the rates of change of three soil properties decrease with time these are the texture in different horizons change in added airborne and rain washed dust salinity within the soil profile change in added salts and gypsum and the amount of mechanically shattered rocks 3 soil thickness is established rather rapidly young and older holocene soil have practically the same depth surficial weathering rates appear to remain fairly constant with time 4 in coarse gravel the evolution of reg soils is dependent on added fines and salts of airborne origin and the resultant changing hydrologic regime in the soil profile the run off infiltration ratio changes as more fines and salts are added to the soil profile and as desert pavement develops 5 surficial features and fine clay in the soil profile may be used for approximate dating of otherwise undatable holocene alluvial surfaces salts and gypsum content should be cautiously used in a rather general way

ice cored drumlins at the surge type glacier bruarjokull iceland a transitional state landform this paper presents data on a glacial landform that to our knowledge has not previously been described in the literature the ice cored drumlin the study area is the forefield of the surge type glacier bruarjokull at the northeastern margin of the vatnajokull ice cap fast iceland based on sedimentological field investigations and aerial photograph interpretation a qualitative model for the formation of ice cored drumlins is proposed the drumlin core consists of stagnant glacier ice from a previous advance and bubbly ice formed by snowdrifts which were incorporated during the most recent advance the 1963 64 surge this advance deposited a mantle of basal till and streamlined the ice cored moraines till deformation and deposition on the drumlin ice core is facilitated by a substratum of low permeability ice cored moraines less

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

drumlin sedimentology in a hard bed lowland setting connemara western ireland implications for subglacial bedform generation in areas of sparse till cover cores of coastal drumlins in connemara contain stratified diamictons that interdigitate with gravelly clinoforms and finer grained rhythmites the diamictons are interpreted as subaqueous mud apron deposits delivered by subglacial till advection to continuously failing subaqueous ice contact fans whose strata were being syn depositionally over steepened by glacitectonic deformation the localized nature of the stratified sediments reflects the emergence of subglacial deforming tills and meltwater deposits in a glacilacustrine environment to produce interdigitated mass flow diamictons and grounding line fans wedges these depo centres became glacitectonized and subglacially streamlined during glacier overriding and hence regional drumlin sedimentology reflects the varying degrees of inheritance of pre existing glacigenic deposits and suggests that drumlin production relates more to the position of localized sediment accumulations at the glacier bed than full depth till deformation processes e g instability mechanisms within the same drumlin field till cored drumlins give way down ice to stratified cored drumlins with till caps and then to stratified drumlins this zonation is compatible with the increased lateral variability in drumlin composition that would arise from the occurrence of linear assemblages of glacifluvial esker and subaqueous grounding line sediments in an otherwise marginal thickening till sheet

rapid climate transitions in a coupled ocean atmosphere model recent geochemical data1 2 have challenged the view that rapid climate fluctuations in the north atlantic at the end of the last glacial were caused by the thermohaline circulation of the ocean being switched on or off instead these data suggest that the circulation pattern must have switched between a warm deep mode and a cold shallow mode probably associated with different sites of deep convection3 here i present simulations with a three dimensional ocean model coupled to an idealized atmosphere which show this kind of transition the mechanism for the transition is a rearrangement of convection in the north atlantic triggered by a brief freshwater pulse this results in a drop in sea surface temperature in the north atlantic by up to 5 c within less than 10 years the rate of north atlantic deep water nadw forma tion is the same in the cold climate as in the warm climate but nadw sinks to intermediate depths only while antarctic bottom water pushes north to fill the entire abyssal atlantic

the sedimentology and accretionary styles of an ancient gravel bed stream the budleigh salterton pebble beds lower triassic southwest england abstract three accretionary styles are present in the fluvial conglomerates and pebbly sandstones of the lower triassic budleigh salterton pebble beds bspb of east devon the lower portions of this 20 30 m sequence are dominated by extensive 50 m sheets or narrow lenses of planar cross bedded conglomerate sets 1 3 m thick these abruptly pass both downstream and laterally into horizontally bedded conglomerates cross bedded sandstones and muddy sandstones this accretionary style reflects deposition from linguoid shaped macroforms whose distal margins were bounded by slipfaces they accreted at anabranch confluences and as bank attached bars in relatively confined and channelised gravel bed streams lateral facies changes represent macroform evolution resulting from changing discharges or abandonment of a channel reach followed by accretion of a new macroform the upper portions of the bspb mainly comprise couplets of horizontally bedded conglomerate overlain by large scale trough cross bedded sandstone the conglomerate shows local channel macroform relief and lateral and downstream transitions into sets of gently dipping conglomerate this style of accretion represents deposition in less confined and less channelised fluvial systems by relatively low relief gravel macroforms and large sand dunes the third style recognised in the bspb is much more localised it consists of wedge like sets of large scale trough cross bedded conglomerate the sets are formed by erosion and subsequent fill of scours cut into a thick sandy substrate techniques of lateral profile analysis and hierarchical ordering of bounding surfaces can usefully be applied to some parts of the bspb this is important as the approach was originally developed for the deposits of sand bed streams however this approach is more difficult to apply to fluvial conglomerates because of the cryptic nature of some gravel stratification the appearance and character of some hierarchies of bounding surfaces may differ from their equivalents in fluvial sandstones

controlled moraines origins characteristics and palaeoglaciological implications abstract controlled moraines are supraglacial debris concentrations that become hummocky moraine upon de icing and possess clear linearity due to the inheritance of the former pattern of debris rich folia in the parent ice linearity is most striking wherever glacier ice cores still exist but it increasingly deteriorates with progressive melt out as a result moraine linearity has a low preservation potential in deglaciated terrains but hummocky moraine tracts previously interpreted as evidence of areal stagnation may instead record receding polythermal glacier margins in which debris rich ice was concentrated in frozen toe zones recent applications of modern glaciological analogues to palaeoglaciological reconstructions have implied that a controlled moraine development can be ascribed to a specific process e g englacial thrusting or supercooling and b controlled moraine preservation potential is good enough to imply the occurrence of the specific process in former glacier snouts e g ancient polythermal or supercooled snouts these assumptions are tested using case studies of controlled moraine construction in which a wide range of debris entrainment and debris rich ice thickening mechanisms are seen to produce the same geomorphic features polythermal conditions are crucial to the concentration of supraglacial debris and controlled moraines in glacier snouts via processes that are most effective at the glacier permafrost interface end moraines lie on a process form continuum constrained by basal thermal regime the morphological expression of englacial structures in controlled moraine ridges is most striking while the moraines retain ice cores but the final deposits landforms tend to consist of discontinuous transverse ridges with intervening hummocks preserving only a weak impression of the former englacial structure these are arranged in arcuate zones of hummocky moraine up to 2 km wide containing ice walled lake plains and lying down flow of streamlined landforms produced by warm based ice a variety of debris entrainment mechanisms can produce the same geomorphic signature spatial and temporal variability in process form relationships will lead to the sequential development of different types of end moraines during the recession of a glacier or ice sheet margin

tropical cyclone activity in the northwest pacific in relation to the el nino southern oscillation phenomenon abstract the interannual variations in tropical cyclone activity in the northwest pacific nwpac and their relationships with the el nino southern oscillation enso phenomenon were studied using the method of spectral analyses time series of a southern oscillation index soi defined as the sea level pressure difference between easter island and darwin and tropical cyclone activity in the entire nwpac ocean basin as well as in different regions of the nwpac were analyzed two spectral peaks are apparent in all these time series one corresponds to the generally accepted southern oscillation with a period of 3 to 3 5 years and another at the quasi biennial oscillation qbo frequency cross spectral analyses between the soi and tropical cyclone activity show significant coherence in these two spectral peaks the dominant peak is at the southern oscillation frequency with the soi leading typhoon activity by almost a year at the qbo frequency the two series are almost in phase cyclone activity in t

calcrete as a source of heterogeneity in triassic fluvial sandstone aquifers otter sandstone formation sw england carbonate is not generally considered as a potential source of large scale heterogeneity in permo triassic sandstone aquifers this study shows that carbonate in the form of early diagenetic calcrete forms an abundant component of the triassic otter sandstone formation in south devon three types of calcrete are described from the outcrop of this fluvial sandstone dominated aquifer rhizocretions calcrete sheets and calcrete conglomerates data obtained from core plugs show that calcrete reduces sandstone permeability to less than 10 15 m2 and porosity to less than 12 calcrete can be sufficiently abundant to produce a significant up to 30 reduction in the total effective porosity of the aquifer moreover calcrete conglomerates can form laterally extensive up to 1 km low permeability sheets that will represent major baffles to vertical flow

a revised approach to discriminating sediment transport histories in glacigenic sediments in a temperate alpine environment a case study from fox glacier new zealand clast shape measurements have developed into a standard method for reconstructing the transport histories of sediments in glacial environments the majority of studies use the ra c40 covariance approach with some researchers routinely including clasts of varying lithologies within their samples the corollary is that variable lithological properties may control clast form and roundness rather than debris transport mechanisms despite this the role of lithology on clast shape in glacial environments has rarely been analysed furthermore some studies have reported difficulties in using the ra c40 co variance plot in discriminating clasts that have undergone subglacial transport and clasts that have been modified by fluvial activity results from a glacierized valley in a temperate alpine setting indicate that detailed analysis of clast shape where samples are of uniform lithology although time consuming is a useful tool in the investigation of deposits in glaciated environments copyright 2012 john wiley sons ltd

evolution of reg soils in southern israel and sinai abstract reg soils mostly camborthids and gypsiorthids cover some 15 of the negev and sinai deserts analytical data of seven profiles on depositional surfaces of increasing age in the negev show clear relationships between ages of surfaces and soil profile features exemplified in the development of the cambic salic and gypsic horizons the youngest soil a coarse desert alluvium soil typic torriorthent of dry wadi beds up to a few thousand years old has little profile differentiation and is generally non saline or slightly saline on the higher terraces connected with the lisan formation about 70 000 12 000 years b p clear profile differentiation and the beginning of development of cambic horizons can be discerned evident in their colour textural p differences the soils are already saline and somewhat gypsiferous both soils are not yet defined as regs because of their negligible or restricted profile differentiation reg soils on the older and higher geomorphic surfaces in the arava rift valley several hundred thousand years old have well differentiated profiles with cambic salic and gypsic horizons below their stony desert pavements typical reg soils have light coloured vesicular horizons over mellow very pale brown loam frequently with laminar structure almost completely stone free layers the reddish brown loamy to clay loam b horizons are very saline and show intensive salt weathering of gravels gypsic and petrogypsic horizons occur at depth such reg soils represent the stable surfaces and soils of deserts and were developed over a long period of desert weathering

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

mode of subglacial transport deduced from till properties mýrdalsjokull iceland abstract a multi methological study of recent deposited till yields new insights into the mode of subglacial transport at slettjokull the northern margin of the m rdalsjokull ice cap the ice flow direction transport distance transport path and glacier regime are known for a well defined point source this knowledge permits an investigation of the lateral development of till properties and the reconstruction of a sedimentological model comprising some of the parameters affecting the modification of sediment in subglacial transport one of the most remarkable results from this investigation is the very short transport distance that is required for the different till properties to reach a mature state within the first 250 m of transport distance significant changes occur in the grain size distribution clast morphology geochemical and mineral magnetic properties however the variation beyond 250 m suggests that till properties are likely to be a function of parameters other than transport distance it is inferred on the basis of a renewed depositional model that the physical processes and conditions in a deformable bed beneath slettjokull are highly responsive to any change in type of substratum furthermore it is proposed that the ability of comminution processes to act on the sediment in transport is controlled by the prevailing subglacial drainage conditions and its influence on the rheological behaviour of a deformable bed as a consequence it may be demonstrated that the sedimentary properties of the deforming bed till might change significantly over very short distances without direct correspondence to transport distance

geomorphology and style of plateau icefield deglaciation in fjord terrains the example of troms finnmark north norway in spite of a widespread distribution the way in which plateau icefields affect the glaciation and deglaciation of adjacent terrains is not particularly well known this paper aims to identify how the deglaciation of the fjord and plateau terrain of north norway has influenced the glacial geomorphology and relative sea level history of both local and adjacent areas and so serve as a model for interpreting similar areas along the continental margins of northwest europe and elsewhere the identification of moraines and their relationships with the main shoreline of northern norway allows the margins of the oksfjordjokelen svartfjelljokelen and langfjordjokelen plateau icefields to be identified in the adjacent terrains in locations where ice margins are uncertain it is also possible to reconstruct ice limits by means of glacier models appropriately constrained by known local conditions and dates earlier glacier margins characterised in north norway by ice shelves floating in the local inlets of major fjords also can be related to known regional shorelines the distribution of high shoreline fragments augmented by radiocarbon dates helps show the extent to which inter island channels and outermost parts of fjords can become deglaciated relatively early in comparison with published maps of regional deglaciation plateau icefield centred glaciation became important sometime after 14 000 14c yr bp and was characterised by glacier readvances up to and in some locations beyond earlier moraines and raised marine features although overlooked until recently the identification of the influence of plateau icefields on local glaciation and their interaction with local and regional marine limits is of great importance in accurate palaeoenvironmental reconstruction copyright 2002 john wiley sons ltd

long term enso like events represented in the middle pleistocene shelf successions boso peninsula japan abstract millennial century and decadal scale stratigraphic cyclicities are described from transgressive shelf successions of the middle pleistocene ichijiku and kakinokidai formations ca 0 7 ma in the boso peninsula japan the ichijiku formation ca 400 m thick represents a shelf sandridge complex developed under the influence of the large meanders of the paleo kuroshio current and intertongues with outer shelf muddy deposits of the kakinokidai formation ca 170 m thick to the northeast most of the two formations are classified as a transgressive systems tract formed during the rise in glacioeustasy from oxygen isotope stages 18 to 17 three different types of cyclicities are identified in the transgressive shelf deposits the first cyclicity ca 3000 years duration is represented by coarsening upward units of the kakinokidai formation associated with the northeastward extension of the sandridge complex lower parts of each coarsening upward unit are characterized by intercalations of tempestites more than the upper parts the second cyclicity ca 250 years duration is defined by master bedding surfaces within sandridge deposits interpreted as formed in response to lateral migration of foresets of the sandridge complex the third cyclicity ca a few decades or shorter duration is defined as the units bounded by reactivation surfaces within large scale trough cross bedded sandstone units the three different types of cyclicities are interpreted to document fluctuations in the paths and speeds of the paleo kuroshio current in response to the large meanders oscillations of the large meanders of the modern kuroshio current every few to 10 years are interpreted to be in response to enso el nino southern oscillation events and are also associated with the decrease in frequency of typhoons in the western pacific if our stratigraphic interpretation is true the paleo kuroshio current controlled shelf successions document high frequency oscillations in paleoclimates responding to the long term enso like events in the western pacific during the middle pleistocene

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

illite in aridic soils desert dusts and desert loess abstract in some desert loess deposits notably those of central asia illite dominates the clay fraction in others such as in the near east and north africa illite is a minor component the interaction between desert loess deposits and aridic desert soils via desert dusts is used to explain the difference in illite contents vertical profile distribution of illite as well as vertical distributions of soluble and exchangeable potassium are taken to indicate that illite forms pedogenetically in the surface horizon of aridic soils once formed it is stable and accumulates it is postulated that the potassium required for the illitazation process is introduced by aeolian dusts the process is facilitated by wetting and drying cycles dusts originating in deserts where they are presently produced by desert weathering of various rocks are defined as primary or juvenile dusts they have low illite contents such are the dusts that are carried from the eastern sahara and sinai peninsula northeast towards the middle east where they form local loess deposits the central asian dusts on the other hand have been subjected to numerous cycles of deflation and deposition resulting in relatively long residence times in the pedogenic environment of aridic soils this results in the enrichment of these dusts with illite the central asian desert loess deposits that interact with these dusts are consequently enriched with illite similar processes of illite enrichment may have operated in other areas such as australia

abrupt climate events 500 000 to 340 000 years ago evidence from subpolar north atlantic sediments subpolar north atlantic proxy records document millennial scale climate variations 500 000 to 340 000 years ago the cycles have an approximately constant pacing that is similar to that documented for the last glacial cycle these findings suggest that such climate variations are inherent to the late pleistocene regardless of glacial state sea surface temperature during the warm peak of marine isotope stage 11 mis 11 varied by 0 5 to 1 c less than the 4 to 4 5 c estimated during times of ice growth and the 3 c estimated for glacial maxima coherent deep ocean circulation changes were associated with glacial oscillations in sea surface temperature

millennial scale climate instability during the early pleistocene epoch climate proxy records of the past 100 000 years show that the earth s climate has varied significantly and continuously on timescales as short as a few thousand years 1 7 similar variability has also recently been observed for the interval 340 500 thousand years ago8 these dramatic climate shifts expressed most strongly in the north atlantic region may be linked to and possibly amplified by alterations in the mode of ocean thermohaline circulation4 5 6 7 8 9 here we use sediment records of past iceberg discharge and deep water chemistry to show that such millennial scale oscillations in climate occurred over one million years ago this was a time of significantly different climate boundary conditions not only was the early pleistocene epoch generally warmer but global climate variations were governed largely by changes in earth s orbital obliguity our results suggest that such millennial scale climate instability may be a pervasive and long term characteristic of earth s climate rather than just a feature of the strong glacial interglacial cycles of the past 800 000 years

sediments and landforms at kviarjokull southeast iceland a reappraisal of the glaciated valley landsystem abstract eyles identified kviarjokull an outlet of the icecap oraefajokull southeast iceland as an exemplar of the glaciated valley landsystem emphasising rockfall debris supply passive transport and reworking of a thick cover of supraglacial morainic till in this paper we take a fresh look at the sediments and landforms of kviarjokull focusing on clast form analysis to reconstruct primary transport pathways new data demonstrate the importance of active transport of debris derived from the glacier bed substantial portions of the supraglacial debris cover can be traced back to englacial channel fill deposits or anomalously thick exposures of basal ice these two types of sediments also make up much of kviarjokull s large neoglacial moraine rampart we attribute the abundance of these non rockfall sediments to the presence of a terminal overdeepening and the switch from predominantly subglacial to predominantly englacial drainage that this induces this hydrological switch enhances retention of debris within ice transport preventing it from being washed away and making it available to feed ice marginal moraine formation the complexity of sediment transport processes observed at kviarjokull and the contrast between it and alpine glaciers undermines any single concept of the glaciated valley landsystem accordingly we propose kviarjokull as the type example of a distinct subclass defined by its moderate relief high debris turnover and drainage behaviour characteristic of an overdeepened basin

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

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

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

east asian monsoon forcing of suborbital variability in the sulu sea during marine isotope stage 3 link to northern hemisphere climate 1 we have generated a new high resolution record of variations in planktonic foraminiferal oxygen isotopes 18o and mg ca from a sediment core images 97 2141 in the sulu sea located in the philippine archipelago of western tropical pacific this record reveals distinct suborbital scale 18o changes most notably during marine isotope stage 3 mis3 30 000 to 60 000 years b p the amplitudes of these 18o fluctuations 0 4 to 0 7 exceed that which can be attributed to sea level changes and must be due to changes in sea surface conditions in the same interval variations in planktonic foraminifera mg ca suggest that suborbital surface ocean temperature variations of 1 to 1 5 c in the sulu sea were not in phase with 18o combined this evidence indicates that the mis3 millennial 18o events in the sulu sea were primarily the result of changes in surface water salinity which today is directly related to the east asian monsoon eam and its influence on the balance between surface water contributions from the south china sea and western pacific warm pool wpwp within dating uncertainties the mis3 sulu sea 18o suborbital variability indicates that times of fresher surface conditions in the sulu sea coincide with similar conditions in the wpwp stott et al 2002 and also with intensifications of the summer eam as recorded in the u th dated chinese hulu cave speleothem 18o record wang et al 2001 and thus by inference with interstadials in the greenland ice core records combined these results indicate that pronounced suborbital variability in the summer eam and intertropical convergence zone itcz during mis3 was tightly coupled with climate conditions in the northern high latitudes

quantifying climate and glacier mass balance in north norway during the younger dryas abstract oksfjordjokelen is located at 70 n on the troms finnmark border in north norway during the younger dryas it was decoupled from and sat just beyond the margin of the scandinavian ice sheet at this time the major fjords in troms and finnmark were ice free with outlet glaciers from the icefield filling a number of smaller side valleys only one outlet from the icefield sorfjorddalen is temporally well constrained by 14 c dating and association with the main shoreline associated with a period of minimal crustal rebound dated to the younger dryas sorfjorddalen is reconstructed using a valley centre line iterative model and assuming a no slip basal boundary condition this assumption of cold based ice is supported by the geomorphological evidence of angular bouldery fronto lateral moraines formed during the younger dryas the equilibrium line altitude for the sorfjorddalen is calculated using both the balance ratio and accumulation area ratio methods and this is used to constrain the snout positions generally to mapped moraines of the other outlets this approach assumes similarity of mass balance gradients and geometries of the outlet glaciers which is supported by present day symmetry of the icefield this method is extremely useful in such environments where dateable material is often difficult if not impossible to find some margins terminated in deep water where bathymetry was lacking making calving quantification problematic with subsequent impacts on equilibrium line altitudes poorly constrained these deep water terminating snouts were discounted from subsequent palaeo climate reconstructions an empirical equilibrium line altitude temperature precipitation relationship was used to define limits of climate change required to sustain the reconstructed icefield palaeo precipitation estimates were refined using a palaeo temperature estimate for the younger dryas from andoya calculations of ice flux through the equilibrium line altitude were used to further constrain the mass balance characteristics of the reconstructed icefield and these suggest similarities with ice masses found in the northern nordaustlandet regions of svalbard