holocene glacial activity and climatic variations in the swiss alps reconstructing a continuous record from proglacial lake sediments cores recovered from proglacial lake silvaplana swiss alps were investigated to examine the influence of holocene glaciers on lacustrine sedimentation during times of glacial activity in the catchment the sedimentation in the lake is dominated by the input of silt and clay sized material delivered by glacial meltwaters the deposition of fine grained material and the formation of varves reflect the existence of glaciers in the catchment and can therefore be used for the reconstruction of glacial history sedimentation rates are up to nine times higher in the varved than in the non varved sediments indicating significantly higher erosion rates under glaciated catchment conditions glacial varves were deposited in lake silvaplana during glacial retreat in the latest pleistocene and early holocene until 9400bp non varved deposits having a higher organic content and coarser grain sizes accumulated at lower rates when glacial activity was absent or negligible within the catchment between 9400 and 3300 bp

permafrost and climate in europe monitoring and modelling thermal geomorphological and geotechnical responses we present a review of the changing state of european permafrost within a spatial zone that includes the continuous high latitude arctic permafrost of svalbard and the discontinuous high altitude mountain permafrost of iceland fennoscandia and the alps the paper focuses on methodological developments and data collection over the last decade or so including research associated with the continent scale network of instrumented permafrost boreholes established between 1998 and 2001 under the european union pace project data indicate recent warming trends with greatest warming at higher latitudes equally important are the impacts of shorter term extreme climatic events most immediately reflected in changes in active layer thickness a large number of complex variables including altitude topography insolation and snow distribution determine permafrost temperatures the development of regionally calibrated empirical statistical models and physically based process oriented models is described and it is shown that though more complex and data dependent process oriented approaches are better suited to estimating transient effects of climate change in complex mountain topography mapping and characterisation of permafrost depth and distribution requires integrated multiple geophysical approaches and recent advances are discussed we report on recent research into ground ice formation including ice segregation within bedrock and vein ice formation within ice wedge systems the potential impacts of climate change on rock weathering permafrost creep landslides rock falls debris flows and slow mass movements are also discussed recent engineering responses to the potentially damaging effects of climate warming are outlined and risk assessment strategies to minimise geological hazards are described we conclude that forecasting changes in hazard occurrence magnitude and frequency is likely to depend on process based modelling demanding improved understanding of geomorphological process response systems and their impacts on human activity

off line acquisition of crustal reflection and refraction data a piggy back seismic reflection survey was carried out in 1984 as part of the dekorp 2 s profile the signal from explosive sources was digitally recorded on 120 channels the objectives were a to record crustal reflections at a wide range of incidence angles 5 85 km offset b to provide 3 d control of deep crustal reflectors seen on the main profile an important consideration throughout the fieldwork was to avoid interference with the main reflection survey this experiment showed that explosive charges as small as 5 90 kg may provide sufficient energy for observations from the steep angle to the wide angle range the off line position of the receivers allowed the reconstruction of steep angle reflection profiles parallel and perpendicular to the main reflection line a strong diffraction cluster on the main line could be correlated laterally and indications about the diffractors shape could be obtained

younger dryas and holocene glacier fluctuations and equilibrium line altitude variations in the jostedalsbre region western norway reconstructed younger dryas 11000 10000 y bp valley and cirque glaciers west of the jostedalsbre ice cap suggest an equilibrium line altitude ela depression of 450 50 m compared to the present level the mid preboreal 9500 200 y bp deglaciation was characterized by vertical wastage indicating that the ela was above the summit plateaus during the erdalen event 9100 200 y bp marginal moraines were formed up to 1 km beyond the little ice age lia moraines which lie in front of the present valley outlet glaciers of the jostedalsbre ice cap the average ela lowering during this event is calculated to 325 m below the modern level lithostratigraphic and paleobotanical studies show that the hypsithermal ca 8000 6000 y bp ela was about 450 m higher than at present as a result jostedalsbreen probably disappeared entirely during that period the glacier reformed about 5300 y bp the ela intersected the modern mean equilibrium line altitude five times from ca 2600 y bp to the present the outlet valley glaciers reached their maximum neoglacial extent during the lia in the mid 18th century when the ela was depressed 100 150 m below the present level

glacier fluctuations of muztagh ata and temperature changes during the late holocene in westernmost tibetan plateau based on glaciolacustrine sediment records late holocene glacier variations in westernmost tibetan plateau were studied based on the analysis of grain size magnetic susceptibility and elements from an 8 3 m long distal glaciolacustrine sediment core of kalakuli lake our results show that there are four glacier expansion episodes occurring in 4200 3700 calibrated years cal years b p 2950 2300 cal years b p 1700 1070 cal years b p and 570 100 cal years b p and four glacier retreat periods of 3700 2950 cal years b p 2300 1700 cal years b p 1070 570 cal years b p and 50 cal years b p present the four glacier expansion episodes are generally in agreement with the glacier activities indicted by the moraines at muztagh ata and kongur shan as well as with the late holocene ice rafting events in the north atlantic over the last 2000 years our reconstructed glacier variations are in temporal agreement with reconstructed temperature from china and the northern hemisphere indicating that glacier variations at centennial time scales are very sensitive to temperature in western tibetan plateau

remarkably extensive glaciation and fast deglaciation and climate change in turkey near the pleistocene holocene boundary moraines in the taurus mountains of south central turkey dated to latest pleistocene or earliest holocene show that glaciers were extraordinarily large typical of the last glacial maximum 21 ka and that rates of glacier retreat and temperature rise exceeded those of the past century surface exposure ages of 7 moraines in a valley at altitudes between 1100 m and 3100 m above sea level range from 10 2 0 2 ka to 8 6 0 3 ka computed using our own production rates and spatiotemporal scaling factors hitherto unresolved differences in cosmogenic 36 cl production rate estimates can make these ages signifi cantly older and therefore the analysis presented here focuses on the rate of change and not on the absolute chronology during deglaciation the equilibrium line altitude ascended 1430 m and the air temperature rose by 9 c deglaciation occurred in two phases during the second faster phase which lasted 500 yr the glacier length decreased at an average rate of 1700 m 100 yr implying a warming rate of 1 44 c 100 yr indicating a rapid climate shift marking the onset of the holocene in turkey

gravity interpretation of the southern wind river mountains wyoming the wind river range is the largest laramide uplift in wyoming and is cored by precambrian rocks thrust over sedimentary rocks of the green river basin to the southwest the origin of these uplifts is in dispute it has been ascribed to horizontal compression along thrusts or vertical movement along high angle reverse faults therefore the attitude of the bounding fault is critical to understanding the mechanics of deformation a gravity study based on 1800 stations has been carried out to attack this question and to complement a cocorp deep crustal reflection study smoothed free air gravity anomalies are highly positive over the wind river range and near zero over the adjacent margins bouguer gravity anomalies range from 252 and 225 mgal in the green river basin and wind river basin respectively to 150 mgal in the basement core of the wind river range the bulk density of sedimentary rocks in the adjacent basins is the critical parameter for gravity interpretation of the deep structure and ranges

lake level fluctuations at ljustjarnen central sweden and their implications for the holocene climate of scandinavia abstract a detailed reconstruction of water level fluctuations in ljustjarnen a small kettle lake in south central sweden provides a preliminary outline of holocene changes in water balance for that region lake levels were generally high from 9200 to 8000 yr b p falling from then until c 6500 6000 yr b p and rising again by 5000 yr b p temporary lowerings were recorded c 4000 yr b p and c 2000 yr b p and water levels have risen dramatically since c 500 yr b p the reconstruction is based on sedimentologic and fossil analyses of multiple cores as well as on geomorphological evidence comparison of lake level fluctuations in south central sweden with those from southern sweden and western finnish lapland and with records of glacier fluctuations in the scandinavian mountains suggest a distinct north south contrast in water balance from 9000 to 5000 yr b p consistent with strongly zonal atmospheric circulation during that period between 7000 and 5000 yr b p the mid holocene dry period appears to have been time transgressive across scandinavia perhaps as a result of a gradual shift in the position of the atlantic polar front and its associated cyclonic stormtrack since 4000 yr b p however most detectable fluctuations are synchronous across scandinavia with the most prominent and widespread change being increased net moisture during the little ice age

two dimensional synthetic seismogram modeling of wide angle seismic data from the wichita uplift oklahoma abstract in conjunction with the 1979 cocorp wichita uplift survey wide angle reflection refraction data were recorded on a fixed array the object of the present study is to model and interpret these wide angle data to add independent constraints on the deep structure of the wichita uplift three common receiver profiles were extracted from the data recording apertures were 3 2 to 23 4 km to the north of the array 4 2 to 14 9 km to the east and 4 2 to 12 6 km to the west these profiles are modeled by iterative fitting of high frequency synthetic seismograms computed by asymptotic ray theory the model derived contains low velocity 2 0 to 2 16 km sec surficial sediments that vary in thickness these account for strong local travel time variations of 0 05 sec and for a small but persistent ghost arrival that follows all the main branches with a delay of 0 2 sec the basement granites rhyolites and gabbros are very near the surface throughout the study area both granite and gabbro outcrops are seen basement p wave velocities are therefore relatively high representative velocities are 4 7 km sec at 0 8 km depth 6 2 at 1 8 6 4 at 2 8 and 6 5 at 4 0 local velocities as high as 7 4 km sec may be present the basement is fairly transparent beneath the wichita uplift with only a few local reflectors present this is consistent with the cocorp results

the holocene vegetation history of the khibiny mountains implications for the post glacial expansion of spruce and alder on the kola peninsula northwestern russia

low velocity zone reflections observed in geometrical shadows of refraction profiles summary a low velocity zone lvz shadow on a refraction profile may contain coherent energy if the lvz contains reflectors the corresponding pre critical reflection branches will lie within the geometrical shadow such energy is observed in data and can via inversion or synthetic seismogram modelling potentially provide information on the location and character of the main structural features those with significant reflectivity within the lvz

tracing surface features to great depths a powerful means for exploring the deep crust abstract seismic reflection profiling of the continental basement provides a means for tracing known features from the surface to great depths and hence for exploring and identifying deep and inaccessible subsurface geology some examples based on cocorp data illustrate the power and potential of this method which has not commonly been applied on a crustal scale

holocene glacier fluctuations in the american cordillera abstract in many areas of the american rocky mountains colorado wyoming utah idaho montana cascade range washington oregon and the sierra nevada california radiocarbon ages suggest that ice receded to near present limits before 10 ka bp a pre altithermal readvance or stillstand left moraines ca 1 3 km beyond and ca 50 300 m below present glacier margins at one locality on glacier peak in washington these deposits are perhaps dated to the early holocene but in general these deposits are probably at least 10 ka old glacial advances during the altithermal ca 8 to 5 ka bp elsewhere are rare radiocarbon evidence for altithermal glacial advances in the colorado front range is questionable the earliest radiocarbon dated neoglacial advances occurred about 5 ka bp in the washington cascades moraines and related deposits believed to be of early neoglacial age i e 5 to 3 ka bp elsewhere are poorly dated for example moraines believed to date to the early neoglacial in colorado triple lakes and wyoming temple lake are actually late pleistocene age based on radiocarbon ages derived from lake sediments at the type localities although relative age data i e lichens rock weathering soils from many areas suggest a three fold neoglacial sequence little supporting radiocarbon evidence is available however tephrochronology distinguishes three neoglacial advances near mount rainier in washington in most mountain ranges of the western united states fresh unweathered sharp crested moraines usually adjacent to present ice margins or near headwalls in empty cirques date to the little ice age of the last several centuries however detailed photographic or other historical records of glacial fluctuations during the last century are rare and detailed mass balance studies rarer still whether or not pre little ice age glacial fluctuations in the american cordillera are synchronous must await better radiometric dating of local moraine sequences

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

migration of wide angle seismic reflection data from the grenville front in lake huron under the auspices of the great lakes international multidisciplinary program on crustal evolution glimpce coincident steep and wide angle seismic reflection data sets were acquired in lake huron the wide angle data were recorded at stationary onshore receivers during the shooting and recording of the conventional marine steep angle survey to extract information from the wide angle data a variety of processing techniques including automatic trace editing amplitude balancing f k filtering static corrections and predictive deconvolution were applied to the wide aperture common receiver gather before migration the application of a slowness weighted depth migration algorithm which was first tested on synthetic data and which included a slowness filter resulted in an image of the grenville front tectonic zone gftz remarkably similar to that observed in the multichannel steep angle section the migrated wide angle data suggest that prominent bands of east dipping seismic reflections observed across the gftz extend unattenuated to depths of at least 45 km

uplift unbuckling and collapse flexural history and isostasy of the wind river range and granite mountains wyoming two dimensional gravity and flexural models constrain the structure and isostatic compensation of the wind river range and granite mountains wyoming these ranges are asymmetric basement cored laramide uplifts their large positive isostatic gravity anomalies imply that the topography of the uplifts is not locally compensated for the wind river range gravity data are consistent with thrusting along a listric fault which flattens and soles out at 30 km depth with no detectable offset on the moho we model the large bouguer gravity high over the range with high density lower crustal rocks emplaced over lower density middle crustal rocks along the wind river thrust the high positive gravity anomaly over the granite mountains can be modeled as an extension of the south pass greenstone belt from the southern wind river range eastward beneath the emigrant trail thrust a crustal root as required in local airy compensation for either range requires unreasonably high density material in the upper crust to obtain the observed anomaly combined gravity and flexural models show that a flexural rigidity at least 2 55 1022 n m maximum deflection of 2 km of the moho is required to satisfy the gravity data our results are consistent with models of uplift due to horizontal compression and support of the resulting topography by lithospheric strength an otherwise puzzling episode of oligocene uplift of the wind river range can be explained as unbuckling decrease of deflection of lithosphere accompanying release of laramide compressional stresses flexurally supported uplifts will collapse if the lithosphere is weakened a number of laramide uplifts have collapsed primarily east west trending structures such as the granite mountains the southern end of the wind river range and the uinta mountains we propose that collapse has occurred along zones of established weakness in the crust in response to north south extension

late pleistocene glacial equilibrium line altitudes in the colorado front range a comparison of methods abstract six methods for approximating late pleistocene pinedale equilibrium line altitudes elas are compared for rapidity of data collection and error rmse from first order trend surfaces using the colorado front range trend surfaces computed from rapidly applied techniques such as glaciation threshold median altitude of small reconstructed glaciers and altitude of lowest cirque floors have relatively high rmses 97 186 m because they are subjectively derived and are based on small glaciers sensitive to microclimatic variability surfaces computed for accumulation area ratios aars and toe to headwall altitude ratios thars of large reconstructed glaciers show that an aar of 0 65 and a thar of 0 40 have the lowest rmses about 80 m and provide the same mean ela estimate about 3160 m as that of the more subjectively derived maximum altitudes of pinedale lateral moraines rmse 149 m second order trend surfaces demonstrate low elas in the latitudinal center of the front range perhaps due to higher winter accumulation there the mountains do not presently reach the ela for large glaciers and small front range cirque glaciers are not comparable to small glaciers existing during pinedale time therefore pleistocene ela depression and consequent temperature depression cannot reliably be ascertained from the calculated ela surfaces

the reconstruction of past climates using multi proxy evidence an example of the weichselian pleniglacial in northwest and central europe abstract different lines of terrestrial biotic and abiotic evidence are used for large scale climate reconstructions to transform proxy data into climate parameter values standardisation procedures are defined and described as each type of biotic and abiotic proxy provides its own climate parameter a detailed climate reconstruction may be obtained the multi proxy database for palaeoclimate reconstruction is a specially designed computer database that facilitates data processing and management of weichselian climate proxies this paper describes the application of multi proxy evidence to reconstruct the climate across lowland northwest and central europe during the interval 41 38 bp for this period the mean temperature of the warmest month is estimated at 10 to 11 c and the mean temperature of the coldest month ranges from 27 to 20 c the annual range suggests a cold continental setting with an estimated mean annual temperature between 9 and 4 c a north to south transition from dis continuous permafrost to seasonally frozen ground is suggested by periglacial evidence

late holocene glacier fluctuations in bevringsdalen jostedalsbreen region western norway ca 3200 1400 bp lithostratigraphy and radiocarbon dates from a 1 3 m deep gully section in bevringsdalen sw of jostedalsbreen in western norway with alternating minerogenic glacial and peat non glacial layers demonstrate that glaciers upvalley from the site were present during the following intervals 2595 85 bp 840 700 cal bc to 2360 80 bp 525 385 cal bc between 2250 65 bp 395 225 cal bc and 2150 80 bp 360 105 cal bc between 1740 75 bp cal ad 205 385 and 1730 75 bp cal ad 210 395 and subsequent to 1430 45 bp cal ad 595 645 detailed altitudinal fluctuations of the glaciation threshold equilibrium line relative to the present have been reconstructed for the time interval between 1430 45 bp cal ad 595 645 and 3180 90 bp 1540 1395 cal bc

surface displacements and surface age estimates for creeping slope landforms in northern and eastern iceland using digital photogrammetry abstract in this study three areas of different active coarse debris slope processes are investigated in northern and eastern iceland surface displacement of some glacier derived rock glaciers and a debris covered glacier in the holar area a moving debris accumulation close to siglufjor ur and a debris layer in sey isfjor ur are measured the displacement fields are obtained by cross correlation matching of multi temporal orthophotos orthophotos are generated using a z i imaging digital photogrammetric workstation and various series of air photos from 1964 to 1994 cross correlation matching is done with the cias software the results are analyzed and used for rough surface age estimates in addition type and cause of movement are discussed the velocity of the debris covered glacier and the rock glaciers in the holar area averages from 0 14 to 0 67 m a 1 the debris accumulation at almenningsnof close to siglufjor ur shows an average displacement of 0 19 m a 1 with a maximum value of 0 84 m a 1 the displacements at almenningsnof agree well with displacements surveyed by gps by the icelandic road authorities the measured velocities in sey isfjor ur although using air photos taken 30 years apart turned out not to be significant but the homogenous direction of the displacement vectors suggests that the debris is currently creeping based on the surface age results all the landforms in holar are suggested to have developed during the late holocene cooling period with ages from around 1500 and 3000 to around 5000 years for the different landforms these surface age estimates coincide with data from moraine datings nearby and holocene climatic development in the north atlantic region

the briksdalsbre event a winter precipitation induced decadal scale glacial advance in southern norway in the ad 1990s and its implications in the ad 1990s maritime glaciers in scandinavia started to advance as a response to positive net mass balance in the preceding years invoking annual advance rates in the order of 50 60 m and a total frontal advance of 285 m at briksdalsbreen in less than a decade records from six south norwegian glaciers with continuous annual front measurements are used to evaluate the magnitude duration climatic causes and frontal time lags involved in this mass balance perturbation and the following frontal response of glaciers in southern norway a climate index based on meteorological data from bergen unequivocally demonstrates that the main cause for the large glacier advances in scandinavia in the 1990s was high winter precipitation linked to positive nao index in the winters of 1988 1989 1989 1990 1992 1993 1994 1995 1997 1998 and 1999 2000 less positive or negative glacier mass balance years were 1990 1991 1993 1994 1995 1997 and 1998 1999 between 1996 1997 and 2009 briksdalsbreen retreated

holocene glacier history of bjornbreen and climatic reconstruction in central jotunheimen norway based on proximal glaciofluvial stream bank mires abstract holocene variations of bjornbreen smorstabbtinden massif west central jotunheimen are reconstructed from the lithostratigraphy of two alpine stream bank mires flooded episodically by meltwater the approach uses multiple sedimentological indicators weight loss on ignition mean grain size grain size fractions bulk density moisture content and magnetic susceptibility an a priori model of overbank deposition of suspended glaciofluvial sediments a detailed chronology based on 56 radiocarbon dates and a little ice age sedimentological analogue rapid late preboreal deglaciation was indicated by immigration of betula pubescens by 9700 cal bp an interval of at least 3000 years in the early holocene when glaciers were absent was interrupted by two abrupt episodes of glacier expansion around the time of the finse event the first at ca 8270 7900 cal bp bjornbreen i event and the second at ca 7770 7540 cal bp bjornbreen ii event neoglaciation began shortly before ca 5730 cal bp with gradual build up to the maximum of the bjornbreen iii event at ca 4420 cal bp later maxima occurred at ca 2750 cal bp bjornbreen iv event and at 1300 1260 1060 and 790 cal bp all within the bjornbreen v event glaciers were smaller than today and possibly melted away on several occasions in the late holocene ca 3950 1410 and 750 cal bp minor maxima also occurred at ca 660 and 540 cal bp within the late mediaeval warm period and the early little ice age respectively the little ice age maximum was dated to 213 25 bp ca 205 cal bp the relative magnitudes of the main glacier maxima were determined erdalen event little ice age event bjornbreen vi bjornbreen i finse event bjornbreen ii bjornbreen v bjornbreen iv bjornbreen iii these episodic events of varying magnitude and abruptness were used in conjunction with an independent summer temperature proxy to reconstruct variations in equilibrium line altitude ela and a holocene record of winter precipitation since the preboreal ela varied within a range of about 390 m and winter precipitation ranged between 40 and 160 of modern values winter precipitation variations appear to have been the main cause of these century to millennial scale holocene glacier variations

application of two dimensional synthetic seismogram modeling to interpretation of wide angle seismic data from wind river wyoming in conjunction with the 1977 cocorp wind river project wide angle reflection refraction data were recorded on a fixed array the goals of the present study were to model these wide angle data to provide independent constraints on the wind river structure a common receiver profile extracted from these data forms a pseudo split spread with maximum offsets of 13 3 km toward the southwest and 19 1 km toward the northeast the first 10 s of these data are modeled by iterative fitting of synthetic seismograms computed by asymptotic ray theory the result is a two dimensional velocity model that extends from the center of the wind river mountains into the wind river basin and from the earth s surface to a depth of 25 km the major features of the model are 1 surficial sediments that thicken toward the center of the wind river basin 2 precambrian basement that underlies the sediments and outcrops in the wind river mountains 3 an intrabasement reflector at 5 km depth 4 a low velocity region from 6 to 15 km depth 5 a local high reflectivity laminar zone possibly an intrusive feature at 15 km depth 6 a second low velocity region from 17 to 23 km depth and 7 a laminar transition zone between 23 and 25 km depth that separates the middle crust average velocity 6 km s from the lower crust average velocity 7 km s this study clearly reveals the major crustal structures the most interesting result is tentative evidence that they may be secondary local intrusion of high velocity material as well as the primary horizontal thrusting in the wind river uplift

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

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

problems and interpretation of cocorp deep seismic reflection data wind river range wyoming before the consortium for continental reflection profiling cocorp deep crustal reflection profile across the wind river range wyoming can be understood problems involving velocity multiple reflections and structural style associated with thrusting must be resolved measurements from boreholes to maximum depths of 7 8 km show that a strong velocity inversion is associated with overpressured zones primarily in cretaceous shales one dimensional 1 d synthetic seismograms generated using the detailed velocity distribution closely duplicate the seismic trace on line 1 and produce multiple reflections of significant amplitude to record times of l0 sec other data including auto correlograms demonstrate presence of abundant multiple reflection energy to times of 10 to 12 sec on lines 1 and 2 and suggest that most of the deep events on these lines are multiple reflections because this area has not been known as a problem area for multiples in shallow industry reflection surveys we conclude that mult

late holocene glacier growth in svalbard documented by subglacial relict vegetation and living soil microbes much renewed research interest in arctic regions stems from the increasing concentration of atmospheric greenhouse gases and the alleged climatic sensitivity of high latitude areas glacier and permafrost changes are among a number of proxies used for monitoring past and present arctic climate change here we present observations on frozen in situ soil and vegetation found below cold based glacier longyearbreen 78813 n 2 km upstream from the present glacier terminus dating of the relict vegetation indicates that the glacier has increased in length from about 3 km to its present size of about 5 km during the last c 1100 years the meteorological setting of non surging longyearbreen suggests this example of late holocene glacier growth represents a widespread phenomenon in svalbard and in adjoining arctic regions in addition we use the subglacial permafrozen soil system to evaluate microbial survival capacity over considerable time periods and we present evidence for microbes having survived more than 1100 years in a subglacial permafrozen state

topographic control of equilibrium line altitude depression on reconstructed little ice age glaciers grovabreen western norway little ice age marginal moraines in the grovabreen area inner sunnfjord are mapped and described the modem and little ice age mid eighteenth century equilibrium line altitude ela of the plateau glacier grovabreen is calculated by the use of an accumulation area ratio aar of 0 6 giving a little ice age ela depression of 125 m aar ela depression of the little ice age glaciers is also calculated for northern and southern outlet glaciers different estimates are considered to be the result of topographic differences other methods such as the mean elevation of glaciers meg and the toe to headwall altitude ratio thar gave ela depressions of 260 m and 315 m respectively these differences due to topographic conditions indicate that only glaciers with a uniform slope should be used to calculate the regional ela of former glaciers

depth migration and interpretation of the cocorp wind river wyoming seismic reflection data to better understand laramide deformation deep seismic reflection data have been depth migrated focused or imaged in order to more clearly reveal structural features associated with the wind river thrust wyoming major structural features displayed in the migrated data are the wind river fault zone and the pacific creek anticline the wind river fault zone is seen to a depth of at least 25 km and interpretively to 32 km it is a complex zone that includes numerous splays flattening with depth the wind river range was tilted along these arcuate splays as it was compressionally thrust up the pacific creek anticline is asymmetric and thrust cored with the top of basement offset 600 m the pacific creek thrust is viewed as an embryonic wind river thrust

recognition and paleoclimatic implications of late holocene glaciation on mt taranaki north island new zealand evidence for the timings of inter hemispheric climate fluctuations during the holocene is important with mountain glacier moraine systems routinely used as a proxy for climate in new zealand such evidence for glacier expansion during the late holocene is fragmentary and is limited to glaciers in a narrow zone within the southern alps here we present the first evidence for late holocene glacier expansion on the north island of new zealand in the form of two unconsolidated debris ridges on the south side of the stratovolcano mt taranaki mt egmont at 1920 m a s l the two ridges are aligned north south along the western and eastern sides of a small basin rangitoto flat which is formed between the main taranaki cone to the north and the parasitic cone of fanthams peak to the south the approximate age of the ridges is constrained by dated eruptive events and the relationship between ridge locations and the spatial positioning of adjacent volcanic landforms we propose the ridges formed as two l

filtration fronts in pressure compliant reservoirs hydrofracturing is believed to be the major mechanism responsible for the migration of crust fluids and for the transport of hydrocarbons from overpressured fluid compartments in their analysis of the process of porosity reduction in the earth s crust and crustal pore pressure generation walder and nur 1984 point out that elevated pore pressure generated as a result of local porosity reduction may lead to brittle failure with partial relief of high pore pressure such episodic fracturing accompanied by crack healing may be a common process throughout most of the crust hunt 1990 also speculates that the generation of oil and gas within the compartments plus the thermal expansion of pore fluids eventually causes fracturing of the top compartment seal during periods of basin sinking seal fracturing causes a pressure drop with compartment fluids rushing to the breakout point episodic cycles of resealing and breakout may occur in intervals of thousands of years in rapidly sinking basins such as the u

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

near vertical and intermediate offset seismic reflection data from west of the whipple mountains se california during a seismic reflection survey conducted by the california consortium for crustal studies in the basin and range province west of the whipple mountains se california a piggyback experiment was carried out to collect intermediate offset data 12 31 km these data were obtained by recording the vibroseis energy with a second passive recording array deployed twice at fixed positions at opposite ends of the reflection lines the reflection midpoints fall into a 3 km wide and 15 km long region in vidal valley roughly parallel to a segment of one of the near vertical reflection profiles this data set makes three unique contributions to the geophysical study of this region 1 from forward modeling of the observed travel times using ray tracing techniques a shallow layer with velocities ranging from 6 0 to 6 5 km s was found this layer dips to the south from 2 km depth near the whipple mountains to a depth of 5 km in rice valley these depths correspond closely to the westward projection of the whipple detachment fault which is exposed 1 km east of the near vertical profiles in the whipple mountains 2 on the near vertical profile the reflections from the mylonitically deformed lower plate at upper crustal and mid crustal depths are seen to cease underneath a sedimentary basin in vidal valley however the piggyback data which undershoot this basin show that these reflections are continuous beneath the basin thus near surface energy transmission problems were responsible for the apparent lateral termination of the reflections on the near vertical reflection profile 3 the areal distribution of the midpoints allows us to construct a quasi three dimensional image on perpendicular profiles at the cross points we determined the true strike and dip of reflecting horizons this analysis shows that the reflections from the mylonitically deformed lower plate dip to the southwest westward of the whipple mountains and dip to the south southward of the turtle mountains the results of this study support the interpretation of crustal reflectivity in the near vertical reflection profiles to be related to the mid tertiary episode of extension which produced the whipple metamorphic core complex this association geometrically suggests a more regionally distributed mechanism for crustal thinning as compared with single detachment fault models