spatial patterns of glacier motion during a high velocity event haut glacier d arolla switzerland the surface motion of haut glacier d arolla switzerland was monitored at a high spatial and temporal resolution data are analyzed to calculate surface velocities surface strain rates and the components of the glacier force budget before during and after an early melt season speed up or spring event we investigate the extent to which variations in glacier motion can be attributed to hydrologically induced local forcing or to non local forcing transmitted via horizontal stress gradients enhanced glacier motion is dependent on a change in the spatial distribution of areas of high drag across the glacier

viking formation albian at eureka saskatchewan a transgressed and degraded shelf sand ridge 1 the viking oil field at eureka is part of the long 80 km narrow 10 km east west trending dodsland hoosier offshore sand ridge in west central saskatchewan the various facies of the ridge are encased in marine mudstones and the ridge has formerly been interpreted as a tidal current deposit however core examination shows that the facies are burrowed and bioturbated and very few primary sedimentary structures are preserved the sandstone facies are extensively bioturbated by teichichnus and contain no medium scale cross bedding and no other tidal features such as reactivation surfaces spring neap cycles and tidal bundles cross sections constructed from well logs and cores demonstrate that the ridge overlies an erosion surface and that at least three other erosi n surfaces occur within the sand body these surfaces strike east west and dip very gently southward pebble veneers occur in patches on the erosion surfaces we interpret the ridge as having formed from a plume of sand in a shallow sea with its western end close to a deltaic distributary channel similar to the plume east of the modern nile delta the regional viking shoreline moved north or northeastward into the basin during a lowstand of relative sea level during subsequent transgression the delta was eroded and displaced an unknown distance southwestward the ridge also shifted southward and was finally detached from the distributary and abandoned on the shelf original slopes of the southern ridge margin were flattened to gradients of 0 0006 0 0009 by storm generated currents the internal erosion surfaces were probably formed during the overall transgression rates of sediment movement were relatively slow resulting in almost c mplete bioturbation and hence destruction of primary sedimentary structures

which heterogeneous glacier melting patterns can be robustly observed from space a multi scale assessment in southeastern tibetan plateau abstract region wide investigation of glacier change in high mountain asia marked the strongest recession in southeastern tibetan plateau setp in recent decades however evident differences of quantitative glacier mass balance mb estimations on fine scales exist in the prior reports the large uncertainties in current geodetic observations over this region highlight the need for more independent validations and investigations on the spatial variability of glacier change this study enriched glacier mb estimates over the setp by using the newly released global digital elevation model dem the tandem x and analyzed the spatial pattern of glacier change on multi spatial scales by comparing available satellite based geodetic observations results reveal that the tandem x srtm elevation differences which show no obvious horizontal shifts and no significant elevation dependent bias provide reliable elevation change information over this challenging area on the regional scale the geodetic datasets the aster elevation change rates data tandem x srtm differences icesat achieved a highly consistent estimate of glacier mb at 4 11 1 52 gt a 1 0 60 0 16 m w e a 1 during 2000 and 2010s on the subregional scale the two gridded geodetic datasets revealed a clear contrast between moderate thinning of spring accumulation type glaciers in the south and significantly more negative glacier mb of summer accumulation type glaciers in the north glacier wide mb showed high heterogeneity which was closely related to the combined effect of topographic variation and climate forcings we observed similar glacier thinning rates between debris covered land terminating glaciers and clean ice glaciers 0 50 0 32 m w e a 1 but remarkable more negative mb 0 89 0 36 m w e a 1 of debris covered glaciers connected with glacial lakes which may indicate different evolution process of debris covered glaciers in the monsoon influenced region this study demonstrates that current satellite based geodetic observations achieve overall consistent patterns of glacier mass changes even over the most challenging mountainous areas complicated terrain and climate with the global tandem x dem and increasing observations from the mission we expect improved consistency in glacier mb estimation on large spatial scales as well as detailed investigation of glacier mass change variability in the future

effect of precipitation seasonality on climatic sensitivity of glacier mass balance abstract numerical calculations are described aimed at evaluating the influence of precipitation seasonality and seasonality concentration on climatic sensitivity of glacier mass balance equilibrium line altitudes elas are modeled using idealized meteorological variables and then a warming test 1 c is performed which revealed that the effects of latitude and the annual precipitation amount are less than those of precipitation seasonality and its concentration calculation shows higher sensitivities for the glaciers located in a summer precipitation climate than for those located within a winter precipitation climate difference due to seasonality is enhanced with the seasonality concentration the present study suggests that the earlier parameterization of glacier mass balance with annual precipitation amount is insufficient to describe the response of glaciers to climate change distribution of precipitation seasonality and its concentration suggest that many parts of the world have a summer precipitation climate but their seasonality concentration is not significant worldwide on the other hand an extensive region of asia and part of the andes are located in the highly concentrated summer precipitation climate this suggests the high sensitivity of glacier mass balance in these regions to climate change

glacier variations in the naimona nyi region western himalaya in the last three decades this work quantifies glacier variations in the naimona nyi area of the western himalaya by integrating glacier spatial data from aster and the landsat series of satellite imagery at four different times 1976 1990 1999 and 2003 comparison of the results from individual images with those from the integrated method indicates that the integrated approach provides a better result glacier variations were mapped and analyzed discrepancies between images could be detected and removed from the integrated data using remap tables in arc info grid both graphically and numerically our results show that glaciers in the region both retreated and advanced during the last 28 years however retreat dominates the variation of glaciers in the western himalayan region is dramatic compared with other regions in high asia from 1976 to 2003 glacier area decreased from 84 41 km 2 to 77 29 km 2 sequential images show that glacier areas shrank by 0 17 0 19 and 0 77 km 2 a 1 on average during the periods 1976 90 1990 99 and 1999 2003 respectively suggesting that glacier retreat has accelerated

performance of aster and srtm dems and their potential for assessing glacial lakes in the lunana region bhutan himalaya to assess the potential volume of a glacial lake outburst flood glof more precisely than in previous studies we analyze ground survey data and remote sensing digital elevation models dems around glacial lakes in the lunana region bhutan based on a dem generated from differential gps ground surveys we first evaluate the relative accuracies of dems produced by the advanced spaceborne thermal emission and reflection radiometer aster and the shuttle radar topography mission srtm root mean square errors of the altitudinal difference between these dems and ground survey data were 11 0 m for aster and 11 3 m for srtm these errors are similar to those of previous studies we show that a topographical classification allows a better estimate of elevation on lakes ponds riverbeds and glaciers due to their flat surfaces while the relative accuracy is worse over moraines and hill slopes due to their narrow ridges and steep slopes using the optical satellite images and the ground survey data we re evaluate the glof volume in 1994 as 17 2 5 3 10 6 m 3 we show glof related information such as distance altitudinal difference and gradient at possible outburst points where the lake level is higher than the neighboring riverbed and or glacial lake

contribution of the patagonia icefields of south america to sea level rise digital elevation models of the northern and southern patagonia icefields of south america generated from the 2000 shuttle radar topography mission were compared with earlier cartography to estimate the volume change of the largest 63 glaciers during the period 1968 1975 2000 these glaciers lost ice at a rate equivalent to a sea level rise of 0 042 0 002 millimeters per year in the more recent years 1995 2000 average ice thinning rates have more than doubled to an equivalent sea level rise of 0 105 0 011 millimeters per year the glaciers are thinning more quickly than can be explained by warmer air temperatures and decreased precipitation and their contribution to sea level per unit area is larger than that of alaska glaciers

glacier runoff and its impact in a highly glacierized catchment in the southeastern tibetan plateau past and future trends we investigate past and future trends in glacier runoff and the associated hydrological impacts on river runoff in the hailuogou catchment a highly glacierized catchment with extensive debris cover in the southeastern tibetan plateau using a catchment scale glacio hydrological model past trends in various runoff components of the catchment indicate that glacier runoff has been a large component of total runoff contributing similar to 53 4 of total runoff during the period 1952 2013 future changes in runoff calculated using the outputs of ten global climate models for representative concentration pathway rcp 4 5 and rcp8 5 reveal that glacier runoff plays different roles in the water supply of the catchment for the two rcps and the discrepancies between the two rcps increase in the second half of this century leading to a considerable difference in the hydrological regime of the catchment in particular changes are more remarkable under rcp8 5 under which all glaciers are projected to retreat dramatically and total runoff to decrease slightly by the end of this century an experimental analysis in which no debris cover is assumed on glacier ablation zones indicates that excess meltwater from the debris covered area provides an 8 1 increase in total runoff relative to the no debris assumption case

early permian giant cross beds near nqutu south africa interpreted as part of a shoreface ridge abstract sandstones and siltstones of a giant cross bed sedimentary association at the base of the coal bearing vryheid formation cannot be satisfactorily explained in terms of the currently accepted fluviodeltaic model for these strata in view of the sedimentary structures and associational characteristics of the facies a shoreface ridge interpretation is adopted instead the sandridge probably detached from the shoreface was situated on the slope towards the basin plain and associated with some elements of a minor submarine fan complex rapid shoreface by pass in the course of a marine transgression seems to have provided favourable conditions for sandridge formation the major bedform appears to have been in water of about 45 m depth possibly some kilometres from the contemporary shoreline there is evidence that it was mainly constructed by the action of strong easterly flowing currents probably of relaxant or geostrophic origin these were aided by ebb dominant tidal currents possible actualistic models include north sea and bering sea sandridges currents of the strength needed to build such large bedforms could only have existed in an open ended seaway and it is suggested that the ecca sea must have communicated at least intermittently with open ocean to the northeast and possibly the southeast as well as towards the west

elevation changes in antarctica mainly determined by accumulation variability antarctic ice sheet elevation changes which are used to estimate changes in the mass of the interior regions are caused by variations in the depth of the firn layer we quantified the effects of temperature and accumulation variability on firn layer thickness by simulating the 1980 2004 antarctic firn depth variability for most of antarctica the magnitudes of firn depth changes were comparable to those of observed ice sheet elevation changes the current satellite observational period 15 years is too short to neglect these fluctuations in firn depth when computing recent ice sheet mass changes the amount of surface lowering in the amundsen sea embayment revealed by satellite radar altimetry 1995 2003 was increased by including firn depth fluctuations while a large area of the east antarctic ice sheet slowly grew as a result of increased accumulation

changes in the glacier extent and surface elevation along the ningchan and shuiguan river source eastern qilian mountains china we investigate the changes at nine glaciers in the ningchan and shuiguan river source eastern qilian mountains between 1972 and 2010 according to analysis of topographic maps and multispectral satellite data all nine glaciers in the study area have retreated by a maximum of 250 57 4 m and a minimum of 91 57 4 m the total glacier area decreased by 1 20 km 2 corresponding to 9 9 of the glacierized area in 1972 comparing the two dems generated from the topographic maps and real time kinematic gps data the mean glacier thinning rate was 0 64 m yr 1 between 1972 and 2010 the most significant thinning generally occurred on the termini the ice volume loss was about 106 8 46 7 x 10 3 km 3 equal to 90 8 39 7 x 10 3 km 3 w e which suggested a mean water discharge of 0 1 0 05 m 3 s during 1972 2010 based on analysis of meteorological data the summer temperature june august tends to increase over a similar time period the consistency of temperature increase and glacier shrinkage allows us to suggest that air temperature plays an important role in glacier changes in this region c 2014 university of washington published by elsevier inc all rights reserved

constraints of three dimensional geological modeling on reservoir connectivity a case study of the huizhou depression pearl river mouth basin south china sea abstract the z21 gas field is the only one gas field in the huizhou depression the distributions of sandstone and mudstone in the adjacent west zone control the extent of the z21 gas field making the confirmation of the reservoir connectivity between the west zone and main zone rcwm crucial in this study a practical workflow was proposed to confirm the rcwm first the sandstone and mudstone distributions were modeled by a sequential indicator simulation using the vertical proportion curves as constraints the porosity and permeability distributions were then predicted using a sequential gaussian simulation based on sandstone and mudstone models the sandstone mudstone and physical property models were treated as components of a geological embryonic model gem prior to the rcwm confirmation different hypotheses on the rcwm of the gems were drawn bringing variations to the gems and the gems turned to be different new models these new models were then applied to numerical simulations not only to perform quality checks but also to attain the simulated formation pressure coefficients pfcs and couple the study with the current formation pressure coefficients pfcc derived from the modular formation dynamics tester mdt a hypothesis is negated if the pfcs is not equal or approximately equal to the pfcc a coupled result was iteratively generated until the rcwm was confirmed this coupling study on reservoir connectivity makes use of general geological reservoir models and highlights the ingenious designs based on different hypotheses of the rcwm to generate reliable results coupling study shows that distributions of formation pressure in the west zone of z21 field are largely affected by a low permeability belt and rcwm is proved weak due to the existence of the low permeability belt

multi decadal ice velocity and elevation changes of a monsoonal maritime glacier hailuogou glacier china digital elevation models dems of the ablation area of hailuogou glacier china produced from advanced spaceborne thermal emission and reflection radiometer aster data obtained in 2009 differential gps dgps data surveyed in 2008 and aerial photographs acquired in 1966 and 1989 are differenced to estimate long and short term glacier surface elevation change dh dt the mean dh dt of the ablation area over 43 years 1966 2009 is 1 1 0 4 m a 1 since 1989 the thinning has accelerated significantly ice velocities measured by dgps at 28 fixed stakes implanted in the ablation area increase with distance from the glacier terminus ranging from 41 0 m a 1 approaching the glacier terminus to a maximum of 205 0 m a 1 at the base of an icefall our results reveal that the overall average ice velocity in the ablation area has undergone significant temporal variability over the past several decades changes in glacier surface elevation in the ablation area result from the combined effects of climate change and glacier dynamics which are driven by different factors for different regions and periods

growth and drainage of supraglacial lakes on debris mantled ngozumpa glacier khumbu himal nepal ablation of debris mantled glaciers in nepal has resulted in the formation of several potentially unstable moraine dammed lakes some of which constitute serious hazards ngozumpa glacier khumbu himal has undergone significant downwasting in recent decades and is believed to lie close to the threshold for moraine dammed lake formation the debris mantled ablation area of the glacier is studded with numerous supraglacial lakes the majority of which occupy closed basins with no perennial connections to the englacial drainage system perched lakes perched lakes can undergo rapid growth by subaerial and water line melting of exposed ice faces and calving subaerial and subaqueous melting beneath thick 1 m debris mantles is comparatively insignificant although lake expansion can contribute substantially to ablation of the glacier perched lakes cannot continue to grow indefinitely but are subject to rapid drainage once a connection is made to englacial conduits the level of one of the lakes on the ngozumpa however is controlled by the altitude of a spillway through the lateral moraine of the glacier this lake underwent only limited growth in the period 1998 2000 but is likely to experience monotonic growth if glacier mass balance continues to be negative

glacier retreat as a result of climate warming and increased precipitation in the tarim river basin northwest china the tarim river basin a river system formed by the convergence of nine tributaries is the most heavily glacierized watershed in arid northwest china in the basin there are 11 665 glaciers with a total area of 19 878 km 2 and a volume of 2313 km 3 glaciers in the basin play a significant role in the water resource system it is estimated that they provide about 133 10 8 m 3 of meltwater annually contributing 39 of the total river runoff under the influence of global warming northwest china has experienced a generally warmer and drier climate since the mid 19th century however a so called warm and wet transition has occurred since the late 1980s evidenced by an increase in both precipitation and stream discharge in the xinjiang autonomous region and neighboring regions this paper describes how glaciers in the tarim river basin have responded to such warming and increased precipitation and the impact of these glacier changes we analyzed the variations of more than 3000 glaciers since the 1960s using topographical maps high resolution satellite images and aerial photographs of the river basin our results indicate that glaciers in the basin have been mostly in retreat in the past 40 years and ice wastage has significantly influenced water resources in the tarim river basin estimation by a degree day meltwater model shows the positive anomaly in stream runoff of the tailan river can be partly attributed to the increase in glacier runoff amounting to one third of the stream discharge and a rough estimation using observed average ablation on the termini of 15 glaciers in china verifies that the mass loss calculated by a glacier area volume relation is reasonable 1 study area

the retreat of glaciers in response to recent climate warming in western china glaciers in china are primarily located in the tibetan plateau tp and surrounding high mountains the chinese glacier inventory indicates that there are 46 377 glaciers in western china meteorological records indicate that air temperature in western china has risen by 0 2 c per decade since 1951 and 1998 was the warmest year precipitation in the region increased by 5 10 per decade from 1953 to 1997 using remote sensing and geographic information system methods we have monitored the changes in 5000 glaciers over the past 50 years we conclude that 80 of glaciers in western china have retreated losing 4 5 of their combined areal coverage although some glaciers have advanced in addition regional differences characterize glacier changes over the past few decades for example glaciers in the central and northwestern tp were relatively stable while glaciers in the mountains surrounding the tp experienced extensive wastage mass balance variations for some glaciers show accelerated ice shrinkage in the last two decades

generation of early archaean felsic greenstone volcanic rocks through crustal melting in the kaapvaal craton southern africa abstract high potassium felsic volcanic rocks interlayered with basalt and komatiite in early archaean greenstone sequences in the barberton greenstone belt of south africa and swaziland previously considered to be derived from melting of mafic precursors are shown to be the result of melting of significantly older felsic crust this is documented by a combination of shrimp zircon dating with hf in zircon and whole rock lu hf and sm nd isotopic data zircons from felsic rocks of the oldest barberton unit the 3 53 ga theespruit formation yielded predominantly negative e hf t values whereas whole rock e hf t and e nd t data are slightly negative to slightly positive similar results were obtained for ca 3 45 ga felsic rocks in the hoeggenoog and noisy formations higher up in the greenstone stratigraphy these data rule out derivation of the felsic units from melting of basaltic precursors and favor a crustal source most likely of ttg composition the isotopic data are not compatible with an entirely oceanic origin of the barberton greenstone sequences and favor a pre greenstone basement beneath the volcanic rocks crustal melting of eo to paleoarchaean lower crust probably generated the felsic volcanic rocks and is likely to have been responsible for gradual stabilization of the kaapvaal craton

implications of jurassic cretaceous and proterozoic piercing lines for laramide oblique slip faulting in new mexico and rotation of the colorado plateau discussion and reply discussion cather 1999 1 reevaluated piercing lines created by depositional pinch outs and truncations of jurassic cretaceous strata across the rio grande rift to conclude that a minimal dextral offset of 85 km of these rocks postdates their deposition his graphical depiction of the data and analysis of

mass balance of glaciers and ice caps consensus estimates for 1961 2004 1 working with comprehensive collections of directly measured data on the annual mass balance of glaciers other than the two ice sheets we combine independent analyses to show that there is broad agreement on the evolution of global mass balance since 1960 mass balance was slightly below zero around 1970 and has been growing more negative since then excluding peripheral ice bodies in greenland and antarctica global average specific balance for 1961 1990 was 219 112 kg m 2 a 1 representing 0 33 0 17 mm sle sea level equivalent a 1 for 2001 2004 the figures are 510 101 kg m 2 a 1 and 0 77 0 15 mm sle a 1 including the smaller greenland and antarctic glaciers global total balance becomes 0 38 0 19 mm sle a 1 for 1961 1990 and 0 98 0 19 mm sle a 1 for 2001 2004 for 1991 2004 the glacier contribution 0 77 0 26 mm sle a 1 is 20 30 of a recent estimate of 3 2 0 4 mm a 1 of total sea level rise for 1993 2005 while our error estimates are not rigorous we believe them to be liberal as far as they go but we also discuss several unquantified biases of which any may prove to be significant

monitoring the glacier changes in the muztag ata and konggur mountains east pamirs based on chinese glacier inventory and recent satellite imagery glaciers in the muztag ata and konggur mountains of the eastern pamir plateau northwestern china have been monitored by applying aerial photo stereo models 1962 66 and landsat tm 1990 and etm 1999 images all of which have been compared in order to detect areal and frontal changes through the past four decades the mean frontal retreat of glaciers in the muztag ata and konggur mountains increased from 6 0 m a 1 between 1962 66 and 1990 to 11 2 m a 1 between 1990 and 1999 with an overall glacier length reduction of 9 9 for the whole study period the glacier area has decreased by 7 9 mainly due to changes observed in the most recent period 1990 99 when the annual area loss almost tripled to 1 01 km 2 a 1 based on meteorological data from taxkogan station since 1957 we conclude that climate change particularly the rise in summer temperature after 1994 is the main forcing factor in glacier shrinkage

catchment scale reconstruction of glacier mass balance using observations and global climate data case study of the hailuogou catchment south eastern tibetan plateau summary debris covered glaciers are common in the tibetan plateau where ablation zones are mantled in a supraglacial debris cover that influences glacier mass balance runoff and response to climate change by affecting the melt rate of the underlying ice the impact of debris cover has not yet been taken into account in regional or global scale assessments of glacier mass balances and freshwater resources by using physically based numerical models here a surface energy mass balance model that accounts for the significance of debris cover and its effect on the ice melt rate is applied to reconstruct the glacier mass balance of hailuogou catchment which is located in the south eastern tibetan plateau and contains three debris covered and four debris free monsoonal maritime glaciers according to our calculations the glaciers in hailuogou catchment show a mean annual balance of 0 42 m water equivalent w e per year for a total mass loss of 24 3 m w e over the period 1952 2009 a comparison of summer temperature and precipitation mass balance equilibrium line altitude ela relations indicates that the glaciers in the catchment are much more sensitive to temperature change than to precipitation change in the last 20 yrs increasing summer temperature is the main cause of rapid wasting of the glacier mass in the catchment meanwhile the presence of supraglacial debris markedly accelerates glacier mass loss resulting in the unstable termini of debris covered glaciers in hailuogou catchment this highlights the importance of debris cover for understanding glacier mass balance and hydrology in the tibetan plateau

distribution of debris thickness and its effect on ice melt at hailuogou glacier southeastern tibetan plateau using in situ surveys and aster imagery debris cover is widely present in glacier ablation areas of the tibetan plateau and its spatial distribution greatly affects glacier melt rates high resolution in situ measurements of debris thickness on hailuogou glacier mount gongga southeastern tibetan plateau show pronounced inhomogeneous debris distribution an analysis of transverse and longitudinal profiles indicates that the ground surveyed debris thicknesses and advanced spaceborne thermal emission and reflection radiometer aster derived thermal resistances of debris layers correlate strongly over the entire ablation area across and along glacier patterns of aster derived thermal resistance correspond well with spatial patterns of debris thickness which may reflect large scale variations in the extent and thickness of the debris cover the ice melt rate variability over the ablation area simulated by a surface energy balance model that considered thermal resistance of the debris layer indicates clearly the crucial role of debris and its spatial continuity in modifying the spatial characteristics of melt rates because of the inhomogeneous distribution of debris thickness about 67 of the ablation area on hailuogou glacier has undergone accelerated melting whereas about 19 of the ablation area has experienced inhibited melting and the sub debris melt rate equals the bare ice melt rate in only 14 of the ablation area

seasonal variations in ice deformation and basal motion across the tongue of haut glacier d arolla switzerland records of surface motion englacial tilt and repeat inclinometry are used to determine patterns of surface internal and basal motion across the tongue of haut glacier d arolla switzerland over temporal scales ranging from days to months findings are interpreted with reference to contemporaneous measurements of subglacial water pressures and prior knowledge of the glacier s subglacial drainage system structure long term inclinometry results show pronounced extrusion flow over a subglacial drainage axis with basal velocities up to twice those measured at the glacier surface deformation profiles are more conventional away from the drainage axis with basal velocities 60 70 of surface velocities comparison of long term tilt rates from repeat inclinometry and englacial tilt meters shows close correspondence englacial tiltmeter data are used to reconstruct internal velocity profiles and to split surface velocities into internal deformation and basal motion contributions over spring summer and autumn winter periods although spatial patterns of surface movement are similar between periods patterns of internal and basal motion are not results are interpreted in terms of the location of sticky and slippery spots with temporally changing patterns of basal drag reflecting changing distributions of water pressure

glacier change and glacier runoff variation in the tuotuo river basin the source region of yangtze river in western china glaciers in the tuotuo river basin western china have been monitored in recent decades by applying topographical maps and high resolution satellite images results indicate that most of glaciers in the tuotuo river basin have retreated in the period from 1968 1971 to 2001 2002 and their shrinkage area is 3 2 of the total area in the late 1960s to assess the influence of glacier runoff on river runoff a modified degree day model including potential clear sky direct solar radiation has been applied to the glaciated regions of the river basin over the period 1961 2004 it was found that glacier runoff has increased in the last 44 years especially in the 1990s when a two thirds increase in river runoff was derived from the increase in glacier runoff caused by loss of ice mass in the entire tuotuo river basin

glacier thickening and decay analysis from 50 years of glaciological observations performed on glacier d argentiere mont blanc area france numerous glaciological data have been obtained from measurements carried out on glacier d argentiere mont blanc area france since the beginning of the 20th century moreover data on annual mass balance ice flow velocity thickness variation and length fluctuation have been obtained from yearly measurements performed since 1975 this dataset provides an excellent opportunity to analyze the relationships between surface mass balance and dynamic response over time periods during which net mass balance changed from positive to negative following a positive specific net balance period between 1960 and 1981 the ablation zone experienced a large increase in thickness and ice flow velocities conversely the highly negative specific net balance period since 1982 has led to strong thinning deceleration and retreat of the tongue the response of these observed dynamics to surface mass balance is analyzed from ice flux calculations performed on three transverse cross sections our results reveal that the ice fluxes are largely accommodated by ice flow velocities velocity fluctuations are synchronous over the entire area studied in the largest part of the glacier no compressing extending flow change has been observed over the last 30 years and thickness changes are solely driven by surface mass balance changes however on the tongue of the glacier thickness changes do not depend on surface mass balance but are mainly driven by changes in the longitudinal strain rate

lowstand deltas in the frontier formation powder river basin wyoming implications for sequence stratigraphic models deposits of lowstand deltas formed on the floor of the cretaceous interior seaway of north america are found in the cenomanian lower belle fourche member of the frontier formation central wyoming sandstones located in similar distal basin locations hundreds of kilometers basinward of highstand shoreline deposits form important hydrocarbon reservoirs isolated within marine shales but interpretation of their origin has been highly controversial the distribution geometry and internal facies of these sandstones are documented by an extensive outcrop study and regional subsurface correlations to develop genetic facies models for these deposits this integrated record of lithofacies ichnofacies palynofacies paleocurrent data bedding relationships and isolith maps incorporates observations from nearly 100 measured outcrop sections and about 550 subsurface well logs four episodes of sediment progradation and subsequent transgression each left behind gradually upward coarsening deltaic sandstones that have eroded tops these deltaic sandstones have a lobate to elongate geometry basinward dipping internal clinoform bedding radiating paleocurrents a low to moderate degree of shallow marine burrowing and show variable wave influence and tidal influence on deposition delta plain paralic and nonmarine facies have been eroded from the top of deltaic successions erosion surfaces capping progradational deltaic successions are the only stratal discontinuities that can be mapped regionally and they appear to record transgressive ravinement enhanced over areas of structural uplift compared with lowstand surfaces of erosion which record the bypass of sediments basinward low accommodation during lowstands left little room for sandstones to stack vertically and successive episodes of delta progradation were offset along strike more tide influenced delta deposits formed within shoreline embayments begin page 262 defined by the topography of older wave influenced delta lobes and subtle syndepositional deformation of the basin floor standard sequence stratigraphic terminology is difficult to use in broad lowstand systems like the frontier formation because sandstones do not show simple vertical stacking patterns major stratal discontinuities can form by processes other than lowstand fluvial erosion and minor syndepositional deformation of the basin floor exerts a first order influence on depositional and sediment preservation patterns although many basin distal sandstones have been interpreted to be deposits of offshore bars shelf isolated valley fills and stranded shorelines the frontier formation examples documented here suggest that many of these deposits may be top eroded deltas formed where rivers delivered sediment to lowstand coastlines the external geometry and internal heterogeneities of hydrocarbon reservoirs found in these types of deposits reflect processes active on the low accommodation deltaic shoreline even in cases where subsequent ravinement has significantly truncated the deposits during transgression

offshore bar deposits of semilla sandstone member of mancos shale upper cretaceous san juan basin new mexico the semilla sandstone which crops out on the eastern side of the san juan basin formed as several discrete offshore shallow marine sandbars separated laterally by muddy interbar areas bar sequences consist of a lower fine grained silty sandstone that grades upward into a coarser grained better sorted trough cross bedded sandstone the maximum thickness of the semilla is 21 m bars are elongated parallel with the shore and in the direction of dip of cross bedding the bars were deposited approximately 50 to 80 km from the shoreline by storms possibly augmented but not overshadowed by tidal currents sand deposition was probably localized on the ancient shelf at a slight steepening of slope of the sea floor a tidal current origin is unlikely for the semilla sandston and for most other described offshore bars

a storm dominated offshore sandstone interval from the corallian group upper jurassic weald basin southern england abstract the upper jurassic corallian group of the subsurface of the weald basin southern england contains two stacked marine sand bodies they have an elongate geometry 9 25 m thick 100 km long 30 km wide and consist predominantly of cross bedded fine to medium grained glauconitic sandstones with bioturbated low angle cross laminated silty sandstones the sandbodies trend east west subparallel to the palaeoshoreline but oblique with respect to the south easterly palaeocurrent direction in general facies are stacked in progressively upward coarsening sequences with lower clays passing up into bioturbated siltstones followed by various types of cross bedded medium grained sandstones the characteristics and distribution of the lithofacies indicate that these sandbodies are not shoreline deposits however they are strikingly like offshore sand ridges widely documented from the cretaceous western interior seaway of north america the lack of any typical features of tidal sandbodies and the common occurrence of erosively based low angle cross lamination resembling hummocky cross stratification in the lower part of the coarsening upwards sequences indicate that storm currents may have been important in generating the corallian offshore sandbodies

glacier changes since the little ice age maximum in the western qilian shan northwest china and consequences of glacier runoff for water supply based on aerial photographs topographical maps and the landsat 5 imidge data we have analyzed fluctuations of glaciers in the western qilian shan northwest china from the little ice age lia to 1990 the areas and volumes of glaciers in the whole considered region decreased 15 and 18 respectively from the lia maximum to 1956 this trend of glacier shrinkage continued and accelerated between 1956 and 1990 these latest decreases in area and volume were about 10 in 34 years the recent shrinkage may be due either to a combination of higher temperatures and lower precipitation during the period 1956 66 or to continuous warming in the high glacicrized mountains from 1956 to 1990 as a consequence glacier runoff from ice wastage between 1956 and 1990 has increased river runoff by 6 2 km 3 in the four river basins under consideration besides the equilibrium line altitude ela rise estimated from the mean terminus retreat of small glaciers 1 km long is 46 m which corresponds to a 0 3 c increase of mean temperatures in warm seasons from the lia to the 1950s

elevation changes measured during 1966 2010 on the monsoonal temperate glaciers ablation region gongga mountains china abstract temperate glaciers are more sensitive to climate change than are polar or continental glaciers and can drive remarkable runoff variation in local water catchments changes in the glacier area and surface elevation of the three monsoonal temperate glaciers in the gongga mountains china were analyzed using series of remote sensing images and digital elevation model dem data all possible sources of uncertainty were considered in detail the results showed that the total glacier area decreased by 4 3 km 2 6 7 between 1966 and 2010 a comparison of glacier surface elevations using dems derived from dual frequency differential gps dgps surveys in 2010 and from 1966 to 1989 from topographic maps the three glaciers underwent significant mass loss from 1966 to 2010 and the mean surface elevation changes were 0 90 0 45 m y 1 06 0 45 m y and 1 12 0 45 m y for hailuogou hlg dagongba dgb and yanzigou yzg glaciers respectively from 1966 to 2010 analysis of the meteorological data showed that the mean annual air temperature increase was the main reason for the thinning and volume loss thinning of the glacier tongue and volume loss was more intense in the period 1989 2010 than in 1966 89 debris thickness and other factors are also believed to play important roles in differential thinning among different areas and periods