cirques in the sierra de guadarrama and7 somosierra mountains iberian central system shape size and controlling factors the guadarrama and somosierra mountain ranges form the eastern sector of the iberian central system and hosted numerous glaciers during the late pleistocene mis2 glaciation was of low intensity with glaciers of small sizes strongly controlled by the climatic context and the topography this study analyses the shape size distribution and location of 96 cirques existing in these mountain ranges in addition to the standard morphometric parameters and controlling factors altitude aspect and lithology used in most studies additional factors were considered here in relation to the pre glacial relief and fracture network the data were obtained and processed using arcgis 10 4 and relations between the parameters and controlling factors were evaluated using statistical methods the results indicate that most are simple cirques tending to isometry with low vertical incision capacity considerable variation in size and predominantly east facing in the context of the iberian peninsula and other european mountains these cirques are among the most isometric the lowest in height and present the least overdeepening the development of these cirques has generally been the result of random combination of various factors thus i the largest cirques are located at intermediate altitudes with the headwall located on the main divides at former torrential valley heads or at the headwalls of fracture corridor valleys and are north facing ii the longest cirques are located at former torrential valley heads on metamorphic bedrock i e schists slates and on uniform slopes finally the prevailing eastern aspects are explained by topoclimatic factors and are in agreement with previous studies which have proposed a circulation weather type cwt model throughout the iberian peninsula during the last glacial period similar to its current configuration

late pleistocene glacial evolutionary stages in the gredos mountains iberian central system during the last glacial period late pleistocene the summits of the gredos mountains iberian central system were covered by plateau glaciers and later evolved into valley and slope glaciers the evolutionary sequence of these paleoglaciers has been obtained using geomorphological indicators and taking the principal moraine as reference these moraines show the limit between the glaciation and deglaciation periods in the glaciation period g four chronologically sequenced stages have been identified the local glacial maximum or maximum ice extent gm limited retreat lr re advance ra and finally major stabilization the steady state stage of greatest glacial stability ms in the deglaciation period d six chronologically sequenced stages have been identified an absolute retreat which involved regression and stabilization d1 two major retreat periods d2 and d4 and two stabilization periods d3 and d5 finally the last stage represents the complete disappearance of the glaciers d6 this evolutionary sequence allows more precise studies of the ages assigned through numerical dating procedures and of the correlation of the paleoglaciers in the gredos mountains with those of other regions

selachians from the niobrara formation of the upper cretaceous coniacian of carrot river saskatchewan canada acid etching of a shell bed zone has enabled us to reclaim numerous fish remains for the niobrara formation coniacian of east central saskatchewan including teeth of the following new taxa odon

glacial landforms and their paleoclimatic significance in sierra de guadarrama central iberian peninsula abstract this paper investigates the glacial evolution on the east face of pico de penalara 40 51 n 3 57 w 2428 m the highest elevation of sierra de guadarrama in the center of the iberian peninsula the geomorphologic stability of glacial landforms and permanence of snow cover were examined and 18 samples were selected for dating with cosmogenic isotope 36cl from moraine formations in four well differentiated phases as well as from a pre glacial periglacial blockfield and a glacial threshold near the headwall the results show the synchrony between the last glacial maximum lgm advance and most results obtained recently by cosmogenic dating in southern europe within the mis marine isotope stage 2 stadial but earlier than the global lgm i e between 25 and 19 ka bp there was slow glacial retreat with minor re advances between 19 and 16 ka and rapid deglaciation from 16 ka this paper presents initial results still pending confirmation for the minimum age of the periglacial summit block formation around 80 ka for the existence of moraine formations older than the last advance and for the existence of glaciers during the younger dryas stadial to explain the synchrony between two moraine formations at different altitudes this paper formulates the hypothesis of the secondary moraine evidenced in currently existing glaciers similar to those which existed on penalara

last deglaciation in northwestern spain new chronological and geomorphologic evidence from the sanabria region abstract geomorphologic mapping morphometric analysis of glacial features and sedimentologic characterization of glacial deposits together with gis management have led to reconstruction of the glacial evolution of the tera valley glacier sanabria lake basin nw spain after the local glacial maximum moreover a structural analysis of the bedrock fracture network based on a detailed map containing 898 fractures has been used to evaluate the influence of bedrock geology in the development of the glacier pattern a detailed model of the deglaciation has been constructed by complementing the geomorphologic evidence with the chronological and sedimentologic study of a drilling core retrieved from the eastern subbasin of sanabria lake in 2004 according to this model 10 episodes of glacier front retreat and stabilization took place after the local glacial maximum subsequently a proglacial lake was established in the eastern subbasin of current sanabria lake fed by ablation waters coming from the glacier front retreat the proglacial activity was extended from a minimum age of 25 6 to 14 3 ka bp in which the sedimentation of organic rich muds took place until 13 1 ka bp subsequently around 13 1 to 12 2 ka bp a short advance of the tera glacier is inferred from the deposition of coarser and less organic sediments after this date the glacier front would have retreated to the headwaters of the tera valley sedimentologic and chronological data from another core retrieved in a moraine dammed deposit indicate that a marginal lake would have been active since at least 22 ka bp until at least up to 10 5 ka bp to the north of sanabria lake these results suggest a local glacial maximum prior to the global lgm and therefore new evidence of an early deglaciation in sw europe

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

early holocene humidity patterns in the iberian peninsula reconstructed from lake pollen and speleothem records abstract comparison of selected well dated lacustrine speleothem and terrestrial pollen records spanning the holocene onset and the early holocene ca 11 7 8 cal kyrs bp in the iberian peninsula shows large hydrological fluctuations and landscape changes with a complex regional pattern in timing and intensity marine pollen records from alboran the mediterranean and off shore atlantic sites show a step wise increase in moisture and forest during this transition however available continental records point to two main patterns of spatial and temporal hydrological variability i atlantic influenced sites located at the northwestern areas enol sanabria lucenza prd 4 characterized by a gradual increase in humidity from the end of the younger dryas to the mid holocene similarly to most north atlantic records and ii continental and mediterranean influenced sites laguna grande villarquemado fuentillejo padul estanya banyoles salines with prolonged arid conditions of variable temporal extension after the younger dryas followed by an abrupt increase in moisture at 10 9 cal kyrs bp different local climate conditions influenced by topography or the variable sensitivity gradual versus threshold values of the proxies analyzed in each case are evaluated vegetation composition conifers versus mesothermophilous taxa and resilience would explain a subdued response of vegetation in central continental areas while in mediterranean sites insufficient summer moisture availability could not maintain high lake levels and promote mesophyte forest in contrast to atlantic influenced areas comparison with available climate models greenland ice cores north atlantic marine sequences and continental records from central and northern europe and the whole mediterranean region underlines the distinctive character of the hydrological changes occurred in inner iberia throughout the early holocene the persistent arid conditions might be explained by the intensification of the summer drought due to the high seasonality contrast at these latitudes caused by the orbital induced summer insolation maximum new records particularly from western and southernmost iberia and palaeoclimate models with higher spatial resolution would help to constrain these hypotheses

palaeoglaciation of parque natural lago de sanabria northwest spain abstract detailed geomorphological mapping provides evidence for at least three phases of glaciation in the parque natural lago de sanabria in northwest spain the most extensive glaciation was characterised by a large plateau ice cap a combination of geomorphological evidence and glacier modelling indicates that this ice cap covered an area of more than 440 km 2 with a maximum ice thickness of c 300 m and outlet glaciers reaching as low as 1000 m this represents the largest ice mass in iberia outside the pyrenees and one of the largest in the mountains of southern europe and the mediterranean region radiocarbon dates from the base of lacustrine sequences appear to suggest that the most extensive phase of ice cap glaciation occurred during the last cold stage weichselian with deglaciation occurring before 14 15 ka 14 c bp a second phase of glaciation is recorded by the moraines of valley glaciers which may have drained small plateau ice caps whilst a final phase of glaciation is recorded by moraines in the highest cirques

deglaciation in the central pyrenees during the pleistocene holocene transition timing and geomorphological significance abstract in this study we document deglaciation in a sector of the southern central pyrenees the panticosa massif and the upper gallego and ossau valleys using cosmic ray exposure cre dating methods which were applied to samples from high altitude polished rock steps and rock glacier boulders the obtained cre dates show a coherent spatial distribution and confirm results previously obtained in this study area thus demonstrating the reliability and robustness of the method the results of analyses based on two distinct isotopes 10 be and 36 cl are consistent although the error is higher for results based on the 36 cl isotope the study provides evidence for ice extent in the high gallego valley during the oldest dryas with glacial advance until the bottom of the valleys although the main glacier tongues remained disconnected from each other during this period the extent of glacier advance was directly related to the elevation of the associated summits the younger dryas glaciers were constrained to cirques or very short ice tongues and dating of the polished rock steps indicates that the ice masses were present until the first millennium of the holocene the brazato rock glacier developed at the beginning of the holocene and remained active until the holocene thermal optimum because of the protective effect of large masses of blocks and boulders

an inventory and morphometric analysis of british columbia glaciers canada we describe an automated method to generate an inventory of glaciers and glacier morphometry from a digital topographic database containing glacier boundaries and a digital elevation model for british columbia canada the inventory contains over 12 000 glaciers with a total cumulative area that exceeds 25 000 km 2 based on mapping from aerial photographs circa the mid 1980s we use the inventory to examine dimensional characteristics among glaciers namely the scaling relations between glacier length width and area glacier length is a good predictor of glacier area and its predictive ability improves when glaciers are stratified by the number of up valley accumulation basins the spatial pattern of glacier mid range altitude parallels glaciation limits previously mapped for british columbia and similarly reflects large scale controls of orographic precipitation and continentality the inventory is also used to refine models that relate glacier mid range and terminus altitudes to regional position aspect and in the case of terminus altitudes an index of glacier shape relations between glacier altitude limits and controlling spatial and topographic factors are used to make further climatic and mass balance inferences from the glacier inventory

an ice cap landsystem for palaeoglaciological reconstructions characterizing the younger dryas in western scotland abstract this paper reviews the contrasting behaviours of ice caps and icefields defines a generic landsystem model that can effectively discriminate between them and applies the model to landform sediment assemblages in an area of western scotland such a model is necessary since many palaeoenvironmental inferences from formerly glaciated terrains are based on the geometry extent and dynamics of reconstructed ice masses the validity of these glacier reconstructions is dependent on the accurate initial interpretation of relict landforms and sediments and their inter relationships a new landsystems model is presented here in which individual geological and geomorphological elements are checked against a set of eight theoretical diagnostic criteria that characterize the style of former glaciation when applied to a 1200 km 2 area of the western scottish highlands the landsystem tool predicts 1 an extensive younger dryas ice cap with a maximum surface elevation of 900 m above sea level implying colder or wetter conditions than previously thought and 2 the survival of an independent mountain icefield in part of the area during deglaciation glaciological theory proxy palaeoenvironmental data and established glacier climate topography relationships support these predictions thereby giving credibility to the landsystem methodology as a generic tool for palaeoglaciological reconstructions

climate variability in the spanish pyrenees during the last 30 000 yr revealed by the el portalet sequence abstract palynological sedimentological and stable isotopic analyses of carbonates and organic matter performed on the el portalet sequence 1802 m a s l 42 48 00 n 0 23 52 w reflect the paleoclimatic evolution and vegetation history in the central western spanish pyrenees over the last 30 000 yr and provide a high resolution record for the late glacial period our results confirm previous observations that deglaciation occurred earlier in the pyrenees than in northern european and alpine sites and point to a glacial readvance from 22 500 to 18 000 cal yr bp coinciding with the global last glacial maximum the patterns shown by the new high resolution pollen data from this continental sequence chronologically constrained by 13 ams 14c dates seem to correlate with the rapid climate changes recorded in greenland ice cores during the last glacial interglacial transition abrupt events observed in northern latitudes heinrich events 3 to 1 oldest and older dryas stades intra allerod cold period and 8200 cal yr bp event were also identified for the first time in a lacustrine sequence from the central western pyrenees as cold and arid periods the coherent response of the vegetation and the lake system to abrupt climate changes implies an efficient translation of climate variability from the north atlantic to mid latitudes

exposure age chronology of the last glaciation in the eastern pyrenees abstract we present a chronology of ice recession in the eastern pyrenees based on in situ produced 10be data obtained from the tet paleoglacier complex the sampling strategy is based on the relative chronology provided by a detailed geomorphological map of glacial landforms results indicate that the last maximum ice advance occurred late i e during marine isotope stage 2 compared to the chronology currently established for the rest of the pyrenees despite debatable evidence for a glacial readvance during the oldest dryas stade ice cap melt out was rapid residual cirque glaciers having disappeared by the allerod interstade this is consistent both with north atlantic excursions established by the greenland ice cores and paleoenvironmental data for the region the rapid response of the east pyrenean ice cap to temperature variations is primarily linked to its small size compared to larger pyrenean ice fields to the dry mediterranean climate and to topography related nonlinearities in which a small vertical rise in equilibrium line altitude generates a large change in ice mass possible sources of age uncertainty are discussed in the context of sampling design for single nuclide 10be dating of landform sequences in formerly glaciated landscapes

reconstructions of mountain glacier profiles northeastern united states ice surface profiles are reconstructed for 37 proposed mountain glacier localities in the northeastern united states including sites in the catskill and adirondack mountains new york the green mountains vermont the white mountains new hampshire and the longfellow mountains and mount katahdin maine the reconstructions determined numerically from the shear stress equation gh sin show estimated ice thickness as a function of valley position and slope in general ice thickness increases from zero at the position of the glacier terminus terminal position is a required input to the model to some equilibrium slab thickness in the upper valley where the slab thickness is inversely proportional to valley slope glacier reconstructions support the empirical evidence for former local glaciation in the catskill and white mountains and in some localities in the adirondack mountains in several proposed glacier locations in the adirondack and green mountains in very shallow basins and in very gently sloping valleys however estimated ice thicknesses exceed the depth of their respective valleys or the elevation of up valley cols suggesting a re evaluation of these localities as sites of local confined ice flow confirmed localities of local glaciation are mostly in valleys with mean gradients greater than about 5 where reconstructed ice thicknesses are less than about 200 m

modeling topographic and climatic control of east west asymmetry in sierra nevada glacier length during the last glacial maximum 1 glaciers draining westward from the sierra nevada divide california during the last glacial maximum lgm were 7 times longer than east draining glaciers we address the degree to which this difference may be attributed to the topographic asymmetry of the west tilted sierran block and the climate asymmetry resulting from orographic modification of pacific ocean storms we simulate kilometer scale glaciers within the 50 50 km kings canyon region of the southern sierra by employing a two dimensional numerical model that is driven by simple spatially variable climates and treats ice transport by deformation sliding and avalanching in numerical experiments we match simulated termini to lgm moraine positions to constrain the parameters of different climate scenarios the 38 km long lgm glacier in kings canyon was reproduced by a climate specified by an equilibrium line altitude ela of 3170 m a mass balance gradient of 0 01 m yr m and a maximum positive balance of 2 m yr this climate generates much shorter average 6 km long east draining glaciers that however overshoot the lgm moraines by 1 km roughly 97 of the e w difference in glacier lengths can therefore be attributed to topographic asymmetry alone a second experiment suggesting a 120 m higher ela of 3290 m east of the divide can explain the shorter east draining glaciers an experiment in which orographic precipitation is explicitly simulated and melt is prescribed using a positive degree day algorithm matches both kings canyon and the average east draining glacier length with an lgm climate that was 5 6 c cooler and 2 times wetter than the modern sierra nevada

glacier development and topographic context 10 paginas 4 figuras 2 tablas the definitive version is available at www3 interscience wiley com

permafrost conditions in the mediterranean region since the last glaciation the relatively warm climate conditions prevailing today in the mediterranean region limit cold geomorphological processes only to the highest mountain environments however climate variability during the late pleistocene and holocene has led to significant spatio temporal variations of the glacial and periglacial domain in these mountains including permafrost conditions here we examine the distribution and evolution of permafrost in the mediterranean region considering five time periods last glaciation deglaciation holocene little ice age lia and present day the distribution of inactive permafrost derived features as well as sedimentary records indicates that the elevation limit of permafrost during the last glaciation was between 1000 m and even 2000 m lower than present permafrost was also widespread in non glaciated slopes above the snowline forming rock glaciers and block streams as well as meter sized stone circles in relatively flat summit areas as in most of the northern hemisphere the onset of deglaciation in the mediterranean region started around 19 20 ka the ice free terrain left by retreating glaciers was subject to paraglacial activity and intense periglacial processes under permafrost conditions many rock glaciers protalus lobes and block streams formed in these recently deglaciated environments though most of them became gradually inactive as temperatures kept rising especially those at lower altitudes following the younger dryas glacial advance the early holocene saw the last massive deglaciation in mediterranean mountains accompanied by a progressive shift of permafrost conditions to higher elevations it is unlikely that air temperatures recorded in mediterranean mountains during the holocene favoured the existence of widespread permafrost regimes with the only exception of the highest massifs exceeding 2500 3000 m lia colder climate promoted a minor glacial advance and the spatial expansion of permafrost with the development of new protalus lobes and rock glaciers in the highest massifs finally post lia warming has led to glacial retreat disappearance enhanced paraglacial activity shift of periglacial processes to higher elevations degradation of alpine permafrost along with geoecological changes

integrated research on mountain glaciers current status priorities and future prospects abstract mountain glaciers are sensitive probes of the local climate and thus they present an opportunity and a challenge to interpret climates of the past and to predict future changes furthermore glaciers can constitute hazards including glacier outburst floods changes in the magnitude and timing of runoff in the mountains and adjacent regions and through worldwide loss of glacier ice a global rise in sea level to understand and ultimately to predict the dynamics and nature of climate and associated glacial and hydrological changes requires an integrated approach with communication and collaboration among glaciologists glacial geologists atmospheric scientists geomorphologists geochronologists and tectonists current strategies of research are evolving towards integrating research on mountain glaciers to address key scientific socio economic and political issues given the rapid birth and growth of new technologies and tools with which to study glaciers and glacial landscapes this community stands poised to address many of these challenges in the near future the key challenges that must be met soon include 1 determining the spatial temporal pattern of fluctuations of mountain glaciers from the last glacial cycle through the present 2 relating historical and past fluctuations in glaciers to variability in the primary features of ocean atmospheric circulation 3 identifying important but poorly understood processes controlling the motion and erosion of glaciers 4 developing and expanding the application of numerical models of glaciers 5 modeling the evolution of mountain landscapes in the face of repeated glaciation 6 examining the climate and the balance of energy and mass at the surface of glaciers 7 characterizing the role of intrinsic climate variability on glacier variations and 8 predicting the distribution sizes and nature of glaciers in the future while these ambitious goals are achievable and the research tools exist success will require significant bridging between the existing research communities involved and ambitious integration of research on mountain glaciers

alpine evidence for atmospheric circulation patterns in europe during the last glacial maximum the configuration of alpine accumulation areas during the last glacial maximum lgm has been reconstructed using glacial geological mapping the results indicate that the lgm ice surface consisted of at least three major ice domes all located south of the principal weather divide of the alps this implies that the buildup of the main alpine ice cover during oxygen isotope stage ois 2 was related to precipitation by dominant southerly atmospheric circulation in contrast to today s prevalent westerly airflow such a reorganization of the atmospheric circulation is consistent with a southward displacement of the oceanic polar front in the north atlantic and of the associated storm track to the south of the alps these results combined with additional paleoclimate records from western and southern europe allow an interpretation of the asynchronous evolution of the different european ice caps during the last glaciation 18o stages ois 4 and 3 were characterized by location of the polar front north of 46 n gulf of biscay this affected prevailing westerly circulation and thus ice buildup in western scandinavia the pyrenees vosges and northern alps at the lgm however the polar front lay at 44 n causing dominating southerly circulation and reduced precipitation in central and northern europe

topographic control of asynchronous glacial advances a case study from annapurna nepal 1 differences in the timing of glacial advances which are commonly attributed to climatic changes can be due to variations in valley topography cosmogenic 10be dates from 24 glacial moraine boulders in 5 valleys define two age populations late glacial and early holocene moraine ages correlate with paleoglacier valley hypsometries moraines in valleys with lower maximum altitudes date to the late glacial whereas those in valleys with higher maximum altitudes are early holocene two valleys with similar equilibrium line altitudes elas but contrasting ages are 5 km apart and share the same aspect such that spatial differences in climate can be excluded a glacial mass balance cellular automata model of these two neighboring valleys predicts that change from a cooler drier to warmer wetter climate as at the holocene onset would lead to the glacier in the higher altitude catchment advancing while the lower one retreats or disappears even though the ela only shifted by 120 m

asynchroneity of maximum glacier advances in the central spanish pyrenees the deglaciation history of the escarra and lana mayor glaciers upper gallego valley central spanish pyrenees had been reconstructed on the basis of detailed geomorphological studies of glacier deposits sedimentological and palynological analyses of glacial lake sediments and an accelerator mass spectrometry ams 14c chronology based on minimum ages from glacial lake deposits the maximum extent of the pyrenean glaciers during the last glaciation was before 30 000 yr bp and pre dated the maximum advances of the scandinavian ice sheet and some alpine glaciers a later advance occurred during the coldest period around 20 000 yr bp synchronous with the maximum global ice extent but in the pyrenees it was less extensive than the previous one later there were minor advances followed by a stage of debris covered glaciers and a phase of moraine formation near cirque backwalls the deglaciation chronology of the upper gallego valley provides more examples of the general asynchroneity between mountain and continental glaciers the asynchroneity of maximum advances may be explained by different regional responses to climatic forcing and by the southern latitude of the pyrenees copyright 2002 john wiley sons ltd

combined numerical and geomorphological reconstruction of the serra da estrela plateau icefield portugal abstract the paper focuses on reconstructing a plateau icefield surface from field geomorphological data and a physical based glacier model the results allow the analysis of the patterns of glacial erosion and the estimation of the palaeo equilibrium line altitudes ela the study area is the serra da estrela a plateau in central portugal rising to 2000 m asl the glaciated area during the last maximum of the serra da estrela glaciation lmgse was 66 km 2 the reconstruction of the topography of the icefield and valley glaciers in the lmgse is based on the schilling and hollin model it iterates along the valley longitudinal profile and is based on the gradient on valley shape indices and on yield basal shear stresses these variables influence ice thickness and therefore also the slope of the ice surface allowing for its reconstruction the key variable is basal yield shear stress and its value was included in the model manually starting from the points of maximum extent of the valley glaciers and following a range known to occur in contemporary conditions the input values are validated by matching the resulting ice surface to geomorphological features where these are absent a constant value of 100 kpa was used the icefield was reconstructed from a radiating set of long sections along which ice thicknesses were calculated a dem of the ice surface was constructed allowing the estimation of the hypsometric curves of the distinct glacier catchments and the calculation of the palaeo elas the results show a regional ela at 1650 m asl with spatial variations across the icefield reflecting mainly the effect of eastward snow drift the lmgse glaciers were very sensitive to minor climatic changes especially due to the large area of the plateau icefield and to the positioning of the elas close to or in the flat part of the hypsometric curve the model of the ice surface is of significant value for the analysis of the patterns of glacial erosion at the landscape level in the serra da estrela most of the glacial erosion occurred near the plateau margins and in valley heads where glacier surface slope was steeper allowing for a faster ice flow and where ice flow concentrated strong glacier erosion in the zezere valley is linked to the tectonic setting but also to the confluence of glaciers and to the overfeeding of snow from the plateau

the plateau glacier in the sierra de bejar iberian central system during its maximum extent reconstruction and chronology abstract a detailed study of the glacial morphology in the sierra de bejar iberian central system provided a data set of geomorphic indicators to reconstruct the paleoglaciers developed in this mountain area during the last glacial cycle late pleistocene applying a physical based glacier model and using the geomorphic indicators a three dimensional reconstruction of the ice mass during the maximum extent of the glaciers has been carried out we used this reconstruction to project hypsometric curves over the former glaciers and to estimate the elas equilibrium line altitudes of the paleoglaciers for their stage of maximum extent at this stage the sierra de bejar hosted a plateau glacier considered as a dome shaped icecap around 57 km2 in area according to our estimations the maximum thickness of the ice was 211 m the minimum elevation of paleoglaciers 1210 m asl and the regional ela was at 2010 m asl during later stages reduction in ice mass due to deglaciation caused the icecap to evolve into an icefield and finally the main glacier was fragmented in valley and cirque glaciers the geochronological data obtained with 10be provides an age of 27 ka for the maximum extent of the glaciers gm whereas the global last glacial maximum lgm represents a younger stage of the sierra de bejar glacier evolution finally the new data obtained in the sierra de bejar allow evaluating the influence of some factors such as the continentality and latitudinal location in the development of glacial processes in these areas of the iberian central system

last glacial maximum and deglaciation of sierra de gredos central iberian peninsula abstract the study area is located in the sierra de gredos a portion of the sistema central range of central spain specifically in the gredos gorge on the north side of pico almanzor 2596 masl where glacial forms are present down to an altitude of 1410 m 10 km from the headwall this paper presents cosmogenic 36 cl surface exposure dates of four closely spaced lateral moraine ridges within the area of maximum advance of the ancient glacier 8 km from the headwall and two glacially polished bedrock thresholds 3 and 5 km from the headwall the dates are overall coherent and indicate a maximum advance at 26 24 ka subsequently the glacier front stabilized around its maximum position for 3 ka with small scale fluctuations resulting in small closely spaced moraines ridges glacier recession began after 21 ka accelerating sharply by 16 ka the glacier had probably disappeared from the gredos gorge by 15 ka there are no traces of older or more recent moraines than those dated in this study these results are in agreement with the well known late pleistocene climatic evolution of the northern atlantic and with the glacial chronology of the alps and other mediterranean mountains however the gredos gorge has no geomorphic evidence of the younger dryas cold event probably because of the low altitude and southern character of these mountains

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

small isolated glacial catchments as priority targets for cosmogenic surface exposure dating of pleistocene climate fluctuations southeastern pyrenees a new 10 be data set from a small glacial catchment in the pyrenees confirms almost full glacier extent during marine isotope stage mis 2 extends the oldest cosmogenic exposure ages of moraines in this mountain range to mis 5 and constrains paleoclimate reconstructions in the mediterranean region it also illustrates the advantageous conditions for the long term preservation of terminal moraines provided by small low gradient glacier catchments that did not merge with compound ice masses even during glacial maxima these small gently sloping and isolated glacier catchments are proposed as priority targets for terrestrial cosmogenic nuclide dating of peak pleistocene glacier advances providing scope for greater accuracy in interregional paleoclimatic correlations

attempt at using the single aliquot regenerative dose procedure for the determination of equivalent doses of upper palaeolithic burnt stones the equivalent dose of upper palaeolithic quartzite pebbles burnt in prehistoric hearths was determined using the optically stimulated luminescence osl signal and the single aliquot regenerative dose sar procedure since previously published thermoluminescence tl dates for these samples were in agreement with the archaeological record and other chronological data the tl equivalent doses were used as a reference the observed discrepancies between some tl and osl sar equivalent doses are probably due to accidental bleaching before the stones reached the laboratory instead of reflecting a deficiency of the sar procedure this hypothesis is confirmed by experiments which indicate that bleaching could reach considerable depths in quartzite specimens and significantly deplete the osl signal

the last deglaciation in the picos de europa national park cantabrian mountains northern spain a sedimentological and geochemical study of the lago enol sequence cantabrian mountains northern spain together with detailed geomorphological mapping provides a first record of glacier evolution and climate change over the last 40 ka in the picos de europa national park the enol glacier retreated from its maximum extent prior to 40 ka bp as demonstrated by the onset of proglacial lacustrine sedimentation in two glaciated depressions the comella hollow to the north before 40 ka bp and the lago enol before 38 ka bp these results support previous evidence that the maximum extent of southern european glaciers occurred earlier than in northern europe alternation of homogeneous and laminated proglacial sediments during the glacier retreat illustrate a dynamic glacial evolution during the marine isotope stage mis 3 40 26 ka bp a slight warming is detected at 26 ka ago with the change from proglacial sediments in a lake located in contact to the glacier to glaciolacustrine sedimentation in a non contact or distal lake finally the onset of organic rich sediments took place at 18 ka ago this last transition occurred in two phases similarly to the north atlantic last termination suggesting a link between north atlantic deep water formation oscillations and palaeohydrological variability in the cantabrian mountains copyright 2009 john wiley sons ltd

global variations of local asymmetry in glacier altitude separation of north south and east west components north south and east west differences in firn line altitude equilibrium line altitude or middle altitudes of glaciers can be separated by regression on the cosine and sine of glacier aspect accumulation area azimuth allowing for regional trends in altitude the north south differences expected from radiation and shade effects can be reliably quantified from world glacier inventory wgi data the north south differences are greater in sunnier climates mid latitudes and steeper relief local altitude differences between north and south facing glaciers are commonly 70 320 m such asymmetry is near universal although weak in the arctic and tropics east west contrasts are less and found mainly in the tropics and areas most exposed to strong winds altitude latitude glacier gradient and height range calculable from most of the wgi data are potential controls on the degree of north south contrast as well as surrogates for climatic controls temperature precipitation radiation and cloudiness an asymmetric sine cosine power model is developed to describe the variation of north south contrast with latitude multiple regression over 51 regions shows altitude and latitude to be the strongest controls of this contrast aspect altitude analysis for former glaciers provides new evidence of cloudiness

application of a degree day model to reconstruct pleistocene glacial climates there is empirical evidence of a nonlinear relation between annual precipitation or accumulation and summer mean temperature at the equilibrium line altitude ela on glaciers around the world the degree day model gives a similar relation between accumulation and summer temperature although instead of a single universal curve there is a family of curves depending upon the annual temperature range furthermore the degree day model also gives nonlinear relations between accumulation and annual mean temperature thus estimations of accumulation can be made from both summer and annual temperatures at the ela of former reconstructed glaciers such as those in greece this is particularly useful since these climatic variables have major implications for biological proxies such as vegetation history indicated in the pollen record and for periglacial proxies such as permafrost distributions indicated in the geomorphological record the close relationship between glaciers and climate provides one of the most precise methods for reconstructing former climates and offers considerable potential for resolving our understanding of pleistocene cold stage climates

late glacial early holocene vegetation and environmental changes in the western iberian central system inferred from a key site the navamuno record bejar range spain abstract a new record from a long sediment core s3 in navamuno 1505 m asl western iberian central system provides the reconstruction of the vegetation history and environmental changes in the region between 15 6 and 10 6 ka cal bp namely during the late glacial and the early holocene using a multiproxy analysis pollen based vegetation and climate reconstruction sedimentary macrocharcoals loss on ignition magnetic susceptibility and x ray fluorescence xrf measurements the results are then compared with other sequences from the iberian central system and the whole iberian peninsula in order to better understand the past dynamics of the main forest constituents the pollen record shows a shift from open pine forests 15 6 14 7 ka cal bp oldest dryas to mixed open pine birch woodlands 14 7 14 0 ka cal bp bolling woodlands were succeeded by a steppe like landscape until 13 4 ka cal bp older dryas which was replaced again by high mountain pine forests and riparian woodlands 13 4 12 6 ka cal bp allerod a great development of cold steppe grasslands linked to the decline of birch woodlands is documented 12 6 11 7 ka cal bp younger dryas the early holocene 11 7 10 6 ka cal bp was characterized by a progressive reforestation of the study area by pine and birch forests in the highlands and oak woods in the lowlands temperate tree taxa carpinus betulus castanea sativa corylus avellana fraxinus juglans tilia and ulmus were also common but likely at lower elevations pollen of fagus sylvatica was already recorded during the late glacial and the early holocene the marked increasing local fire activity during the warmer and wetter allerod oscillation could be related to a rise in tree cover supporting the climatically driven character of these fires nevertheless the strong increase in fire activity during the younger dryas would probably be related to growing tree and shrub mortality as well as to the wet dry biphasic structure of this stadial the standard modern analogue technique has been also applied to the navamuno sequence to provide quantitative climate estimations for the late glacial and the early holocene periods this record is one of the few continental archives that show the climatic trend between the late glacial and the early holocene in central iberia agreeing with many other regional records from the western mediterranean

mountain glacier evolution in the iberian peninsula during the younger dryas abstract we review the evolution of glaciers in the iberian mountains during the younger dryas 12 9 11 7 ka following the chronology of greenland stadial 1 gs1 and compare with available environmental and climate data to investigate glacier dynamics during cold stadial episodes the best examples of younger dryas moraines are found in the central pyrenees involving short ice tongues up to 4 km in length in the highest massifs above 3000 m a s l of the southern versant small cirque glaciers and rock glaciers formed during the yd occurred in other pyrenean massifs in the cantabrian range and in the gredos and guadarrama sierras central range as indicated by several rocky polished thresholds that were ice free at the beginning of the holocene although some former rock glaciers were re activated during the younger dryas glacial activity was limited in the southernmost part of the iberian peninsula sierra nevada most iberian records show vegetation changes during the yd characterized by a forest decline and an expansion of shrubs mainly juniperus and steppe herbs although the vegetation response was not homogeneous because of variable resilience among ecosystems available records also document a variable lake response in terms of hydrology and productivity with a decrease in sedimentation rates and organic productivity in most high altitude lakes and increases in salinity and relatively lower lake levels at lower altitudes the impact of the younger dryas on the coastal environment was almost negligible but it was responsible for a brief cessation in sea level rise high resolution analyses of new speleothem records have documented a double structure for the yd with an earlier drier phase followed by a relatively more humid period the review of geomorphological evidence demonstrates a strong latitudinal control of glacial activity during the yd with more intense development in the northern than in the southern regions the increase in humidity during the second phase of the yd in southern latitudes could have been a decisive factor for glacier advance in the northern iberian mountains

not so deserted paleoecology and human subsistence in central iberia guadalajara spain around the last glacial maximum abstract in contrast to the coastal areas of the iberian peninsula the upper palaeolithic settlement of central iberia dominated by the spanish plateau is poorly known traditional models assume a total or virtual depopulation of the interior of the iberian peninsula during the last glacial in this paper we present a detailed investigation of human environment interactions through the first zooarchaeological taphonomic and isotopic study of the key site of pena capon a rock shelter located in the south eastern foothills of the central system range that contains a multi layered deposit dated to marine isotope stage 2 mis 2 analyses of the faunal assemblages of the proto solutrean 3 and middle solutrean 2 layers show that human preferentially hunted horse deer and iberian ibex living in the vicinity of the rock shelter isotope geochemistry of the animal remains of pena capon provides us with the first detailed intra tooth multi proxy analysis for this time period in south western europe providing estimates of climatic conditions seasonal flucturation of diet as well as patterns of seasonal mobility our results indicate that human presence at pena capon was apparently restricted to relatively warm intervals around the lgm or reflects the presence of an ecological refuge and provide us with evidence of recurrent human presence in the iberian interior during the upper paleolithic prior to the magdalenian