spruce trees from a melting ice patch evidence for holocene climatic change in the colorado rocky mountains usa in september 2006 we found the remains of timber sized spruce trees picea engelmannii on the floors of melting ice patches at altitudes of 3465 3480 m in the mummy range of north central colorado the ice patches occupy northeast facing recesses in which windblown snow scoured from a tundra upland to the southwest accumulates deeply we hypothesize that the upland was timbered during the early to middle holocene dense forest vegetation intercepted snow preventing it from blowing to the recesses and allowing trees to become established there neoglacial cooling led to gradual deforestation of the upland renewed transport and deposition of snow by wind and death of the ice patch trees radiocarbon dates show that the trees died between 3860 15 and 3780 20 14c yr bp c 4200 cal yr bp the trunks show decay similar to that of historic log structures built above timberline during the late nineteenth and early twentieth centuries suggesting that they have been protected by ice for all but a

late holocene glacial activity of bridge glacier british columbia coast mountains bridge glacier is a prominent eastward flowing valley glacier located on the east side of the pacific ranges within the southern british columbia coast mountains the terminus of bridge glacier has retreated at rates up to 125 m year over the last 50 years and currently calves into proglacial bridge lake field investigations of the recently deglaciated terrain and moraines led to the discovery of detrital boles and glacially sheared stumps dendroglaciological analyses of this subfossil wood produced five radiocarbon controlled floating tree ring chronologies the relative age and stratigraphic location of these samples revealed that bridge glacier experienced at least four periods of significant advance during the late holocene a tiedemann aged advance ca 3000 14c years bp an unattributed advance ca 1900 14c years bp a first millennium advance ca 1500 14c years bp and a little ice age advance beginning ca 700 14c years bp lichenometric investigations at eight terminal and lateral moraine comple

subsurface hydrology of layered colluvium mantles in unchannelled valleys south eastern brazil the effects of subsurface hydrology on the evolution of erosive processes inside layered colluvium mantles in unchannelled valleys are investigated tensiometer nests are installed in different morphological conditions with their specific depths controlled by the subsurface structure of the colluvium mantle daily readings during one year and physical and mechanical analyses of the different colluvium layers are carried out in spite of a highly discontinuous subsurface structure present topography is the major factor controlling subsurface flow in this landscape paleotopographic features usually resulting from the lateral mobilization of the previous topographic hollow axis can locally control the preferential expansion of the saturated zone towards areas other than the present hollow axis during rainy periods pressure head at the base of the hollow axis increases towards a maximum value which is not increased by subsequent precipitation inputs new water input is dissipated by direct precipitation onto the saturated zone and exfiltration by seepage at the gully head walls precluding the development of the excess pore pressures required to trigger failure by landsliding

the rhone glacier was smaller than today for most of the holocene we present the development and application of the novel in situ cosmogenic 14 c 10 be chronometer to recently exposed proglacial bedrock of the rhone glacier switzerland results show that during the holocene the glacier was smaller than today for 6500 2000 yr and larger than today for 4500 2000 yr this pattern is consistent with limited data from other techniques for glaciers in the alps and scandinavia but in contrast to glaciers from the southern alps of new zealand emphasizing the high sensitivity of large mountain glaciers to small climate changes the 14 c 10 be chronometer also shows that abrasion rates beneath the rhone glacier increased with ice speed

a major widespread climatic change around 5300 cal yr bp at the time of the alpine iceman palaeoenvironmental and archaeological data from arbon bleiche lake constance switzerland give evidence of a rapid rise in lake level dated by tree ring and radiocarbon to 5320 cal yr bp this rise event was the latest in a series of three successive episodes of higher lake level between 5550 and 5300 cal yr bp coinciding with glacier advance and tree limit decline in the alps this west central european climate change may have favoured the quick burial and the preservation of the alpine iceman recently found in the tyrolean alps it has possible equivalents in many records from various regions in both hemispheres dating to 5600 5000 cal yr bp and corresponds to global cooling and contrasting patterns of hydrological changes this major mid holocene climate event marks the hypsithermal neoglaciation transition possibly resulting from a combination of different factors including orbital forcing changes in ocean circulation and variations in solar activity copyright 2004 john wiley sons ltd

8000 year old wood from the athabasca glacier alberta several wood fragments of pinus sp dated at 8230 80 and 8000 90 years bp and abies sp were recovered from the snout of the athabasca glacier this wood derived from an unknown source up valley indicates that the glacier was less extensive than at present during the hypsithermal and that an area up valley of the present snout was tree covered ca 8000 8300 years bp

late holocene expansion of istorvet ice cap liverpool land east greenland abstract the greenland ice sheet is undergoing dynamic changes that will have global implications if they continue into the future in this regard an understanding of how the ice sheet responded to past climate changes affords a baseline for anticipating future behavior small independent ice caps adjacent to the greenland ice sheet hereinafter called local ice caps are sensitive indicators of the response of greenland ice marginal zones to climate change therefore we reconstructed late holocene ice marginal fluctuations of the local istorvet ice cap in east greenland using radiocarbon dates of subfossil plants 10 be dates of surface boulders and analyses of sediment cores from both threshold and control lakes during the last termination the istorvet ice cap had retreated close to its maximum holocene position by 11 730 cal yr bp radiocarbon dates of subfossil plants exposed by recent recession of the ice margin indicate that the istorvet cap was smaller than at present from ad 200 to ad 1025 sediments from a threshold lake show no glacial input until the ice cap advanced to within 365 m of its holocene maximum position by ad 1150 thereafter the ice cap remained at or close to this position until at least ad 1660 the timing of this the most extensive of the holocene expansion is similar to that recorded at some glaciers in the alps and in southern alaska however in contrast to these other regions the expansion in east greenland at ad 1150 appears to have been very close to if not at a maximum holocene value comparison of the istorvet ice cap fluctuations with holocene glacier extents in southern hemisphere middle to high latitude locations on the antarctic peninsula and in the andes and the southern alps suggests an out of phase relationship if correct this pattern supports the hypothesis that a bipolar see saw of oceanic and or atmospheric circulation during the holocene produced asynchronous glacier response at some localities in the two polar hemispheres

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

onset of neoglaciation in the southern hemisphere a review of evidence documenting an early neoglacial mid holocene advance of mountain glaciers in south america and new zealand reveals that of 16 glaciers for which radiocarbon age control exists only two have associated dates that may approximate the culmination of an advance advances of the remaining glaciers are controlled only by minimum or maximum limiting ages additional dates for several new zealand glaciers are based on weathering rind measurements having large potential errors twelve of the glaciers now terminate or have terminated in lakes or in tidewater and are subject to instabilities associated with calving termini an extensive debris cover in the ablation zone of nearly half of the glaciers makes their moraine succession potentially suspect as a record of detailed climatic variation the two glaciers with seemingly reliable age control are located in valleys where large rock avalanches could affect glacier mass balance and lead to random advances or where rock avalanche deposits might easily be mistaken for moraines and tills the early neoglacial interval has been defined primarily based on this set of data the ages taken at face value suggest that the early neoglacial advance culminated between ca 5400 and 4900 cal yr ago ca 4600 4400 14c yr bp this chronology however should remain provisional until improved age control is obtained for a large population of glaciers based on closely bracketing radiocarbon dates and or an adequate number of cosmogenic isotope ages data from calving glaciers and those subject to rock avalanche activity should be avoided or assessed critically copyright 2000 john wiley sons ltd

mid holocene glacier expansion between 7500 and 4000 cal yr bp in the british columbia coast mountains canada the mid holocene behaviour of five glaciers in the british columbia coast mountains was reconstructed from radiocarbon ages and stratigraphic analysis subfossil wood evidence at canoe fyles jaco

neoglaciation in the southern coast mountains of british columbia chronology prior to the late neoglacial maximum moraine stratigraphy and morphology radiocarbon dates from klinaklini franklin tiedemann gilbert and bridge glaciers and related information from elsewhere in the coast mountains are used to construct a chronology for glacier fluctuations the garibaldi phase of glacier expansion 6000 5000 14c years bp at the end of the early holocene xerothermic interval is indicated by overridden tree stumps the mid neoglacial tiedemann advance 3300 1900 14c years bp is represented by moraines till and meltwater sediments at three glaciers but only tiedemann glacier attained its greatest holocene extent at this time late neoglacial expansion commenced before 900 14c years bp and continued without notable interruption until glaciers achieved their maximum post pleistocene expansion during the eighteenth and nineteenth centuries evidence for the garibaldi and tiedemann events is scarce within the coast mountains because of the more extensive late neoglacial advance however correlative advances have been

heterogeneity of fluvial deltaic reservoirs in the appalachian basin a case study from a lower mississippian oil field in central west virginia since discovery in 1924 granny creek field in central west virginia has experienced several periods of renewed drilling for oil in a fluvial deltaic sandstone in the lower mississippian price formation depositional and diagenetic features leading to reservoir heterogeneity include highly variable grain size thin shale and siltstone beds and zones containing large quantities of calcite siderite or quartz cement electrofacies defined through cluster analysis of wireline log responses corresponded approximately to facies observed in core three dimensional models of porosity computed from density logs showed that zones of relatively high porosity were discontinuous across the field the regression of core permeability on core porosity is statistically significant and differs for each electrofacies zones of high permeability estimated from porosity and electrofacies tend to be discontinuous and aligned roughly north south cumulative oil production varies considerably between adjacent wells and corresponds very poorly with trends in porosity and permeability original oil in place estimated for each well from reservoir thickness porosity water saturation and an assumed value for drainage radius is highly variable in the southern part of the field which is characterized by relatively complex interfingering of electrofacies and similar variability in porosity and permeability

multi proxy record of holocene glacial history of the spearhead and fitzsimmons ranges southern coast mountains british columbia abstract evidence from glacier forefields and lakes is used to reconstruct holocene glacier fluctuations in the spearhead and fitzsimmons ranges in southwest british columbia radiocarbon ages on detrital wood and trees killed by advancing ice and changes in sediment delivery to downstream proglacial lakes indicate that glaciers expanded from minimum extents in the early holocene to their maximum extents about two to three centuries ago during the little ice age the data indicate that glaciers advanced 8630 8020 6950 6750 3580 2990 and probably 4530 4090 cal yr bp and repeatedly during the past millennium little ice age moraines dated using dendrochronology and lichenometry date to early in the 18th century and in the 1830s and 1890s limitations inherent in lacustrine and terrestrial based methods of documenting holocene glacier fluctuations are minimized by using the two records together

expansion of outlet glaciers of the juneau icefield in northwest british columbia during the past two millennia radiocarbon and dendrochronological dating of glacially overridden stumps and detrital wood indicates that two outlet glaciers of the juneau icefield advanced shortly before the little ice age tulsequah glacier advanced to within 2 4 km of its all time holocene limit between ad 865 and ad 940 llewellyn glacier one of the largest glaciers in british columbia advanced sometime between ad 300 and ad 500 and reached to within 400 m of its holocene limit between ad 1035 and ad 1210 well before the climactic classical little ice age advances of the past several centuries our data show that some glaciers in western north america were extensive and expanding at times when alpine glaciers have in the past been assumed to be restricted the evidence raises questions about how to define the time of the beginning of the little ice age and perhaps more importantly about the utility of the term

paragenesis and reservoir quality within a shallow combination trap central west virginia sandstone character and reservoir quality of the lower mississippian pocono big injun sandstone were examined in granny creek stockly field clay county west virginia sixty three samples from 6 wells were analyzed using transmitted light x ray diffraction and scanning electron microscopy techniques the pocono big injun formation is divided into four sands injun 1 through 4 based on composition and hydrocarbon productivity the injun 1 sand is a fine grained carbonate cemented litharenite below the oil producing zone the oil productive injun 2 and 3 sands are well sorted fine grained litharenites which contain more authigenic and allogenic clay minerals than adjacent sands these sands have produced more than 3 4 million bbl of oil from the granny creek part of the field since 1925 the injun 4 sand is generally a coarse grained sublitharenite with marginal gas production limited to the uppermost section of the sand the paragenetic sequence consists of 1 minor quartz overgrowths 2 illite and chlorite grain coatings 3 quartz overgrowths 4 early carbonate 5 kaolinite 6 calcite 7 dolomite and 8 pyrite porosity and permeability were not preserved once paragenesis progressed past the kaolinite stage porosity and permeability are variably preserved when steps in the paragenetic sequence are absent within the pocono group where any porosity is identified within the pocono sandstones primary porosity is dominant however secondary porosity and microporosity in clay rich intervals are also important secondary porosity was c eated by the dissolution of cements and detrital grains authigenic chlorite grain coatings may not be responsible for preserving primary porosity in the big injun sands

dendroglaciological investigations of mid to late holocene glacial activity in the mt waddington area british columbia coast mountains canada dendroglaciological investigations near mt waddington in the central british columbia coast mountains provide an enhanced perspective of holocene glacial activity field investigations at confederation franklin and jambeau glaciers led to the discovery of subfossil wood mats encased in glacial deposits and glacially sheared stumps buried beneath till radiocarbon dated wood collected from valley bottom and lateral moraine sites at confederation glacier suggest that an early holocene advance occurred at c 5665 cal yr bp followed by succeeding intervals of glacier expansion at c 3700 and 3500 cal yr bp at jambeau glacier detrital wood mats buried close to the contemporary lateral moraine crests document glacier expansion at c 3000 cal yr bp detrital subfossil wood buried in lateral moraines at the confluence of confederation and franklin glaciers records distinct episodes of little ice age glacier expansion as early as c 1212 cal yr ad and suggests the glacier surface continued to thicken u

latest pleistocene and holocene alpine glacier fluctuations in scandinavia abstract during the early holocene abrupt decadal to centennial scale climate variations caused significant glacier variations in norway increased freshwater inflow to the north atlantic and arctic oceans has been suggested as one of the most likely mechanisms to explain the abrupt and significant lateglacial and early holocene climatic events in nw europe the largest early holocene glacier readvances occurred 11 200 10 500 10 100 9700 9200 and 8400 8000 cal yr bp the studied norwegian glaciers apparently melted away at least once during the early mid holocene the period with the most contracted glaciers in scandinavia was between 6600 and 6000 cal yr bp subsequent to 6000 cal yr bp the glaciers started to advance and the most extensive glaciers existed at about 5600 4400 3300 2300 1600 cal yr bp and during the little ice age times with overall less glacier activity were apparently around 5000 4000 3000 2000 and 1200 cal yr bp it has been proposed that several glacier advances occurred in scandinavia including northern sweden at 8500 7900 7400 7200 6300 6100 5900 5800 5600 5300 5100 4800 4600 4200 3400 3200 3000 2800 2700 2000 1900 1600 1200 1000 and 700 200 cal yr bp glaciers in northern sweden probably reached their greatest little ice age extent between the 17th and the beginning of the 18th centuries evidence for early holocene glacier advances in northern scandinavia however has been questioned by more recent multi disciplinary studies the early to mid holocene glacier episodes in northern sweden may therefore be questioned most norwegian glaciers attained their maximum little ice age extent during the mid 18th century cumulative glacier length variations in southern norway based on marginal moraines dated by lichenometry and historic evidence show an overall retreat from the mid 18th century until the 1930s 40s subsequently most norwegian glaciers retreated significantly maritime outlet glaciers with short frontal time lags 15 20 years continued their retreat to the 1970s and 1980s however maritime glaciers started to advance as a response to higher winter accumulation during the first part of the 1990s after 2000 several of the observed glaciers have retreated remarkably fast annual frontal retreat 100 m mainly due to high summer temperatures the general glacier retreat during the early holocene and the neoglacial advances after 6000 cal yr bp are in line with orbital forcing due to the decrease of northern hemisphere summer solar insolation and the increase in winter insolation in addition regional weather modes such as the north atlantic oscillation nao and the arctic oscillation ao play a significant role with respect to decadal and multi decadal climate variability

a new interpretation of the date of the little ice age glacier maximum at svartisen and okstindan northern norway new results concerning the dating of little ice age glacier variations at svartisen and okstindan northern norway are presented measurements of lichens of the rhizocarpon subgenus on gravestones are used to construct several local sets of lichenometric dating curves these are partly adjusted in relation to well established lichenometric dating curves from southern norway the little ice age maximum at svartisen and okstindan is thereby dated to the mid eighteenth century i e in agreement with southern norway pre viously suggested earlier little ice age advances are demonstrated to have resulted from an underestimation of the growth rates of the rhizocarpon subgenus synchroneity of little ice age maxima in southern norway and at svartisen and okstindan suggest that a north south migration of latitudinal depressional tracks can be excluded as the main forcing factor as an alternative an increased se nw trend of moist air ow in winter parallel to the coast of norway is suggested as the

orbital insolation ice volume and greenhouse gases abstract the specmap models of orbital scale climate change imbrie et al paleoceanography 7 1992 701 paleoceanography 8 1993 699 are the most comprehensive to date all major climatic observations were analyzed within the framework of the three orbital signals subsequently tuning of signals in vostok ice to insolation forcing has fixed the timing of greenhouse gas changes closely enough to permit an assessment of their orbital scale climatic role in addition evidence from several sources has suggested changes in the specmap 18 o time scale this new information indicates that the timing of co 2 changes at the periods of precession and obliquity does not fit the 1992 specmap model of a train of responses initiated in the north propagated to the south and later returning north to force the ice sheets in addition analysis of the effects of rectification on 100 000 year climatic signals reveals that all have a phase on or near that of eccentricity this close clustering of phases rules out the long time constants for 100 000 year ice sheets required by the 1993 specmap model a new hypotheses presented here revives elements of an earlier climap view hays et al science 194 1976a 1121 but adds a new assessment of the role of greenhouse gases as proposed by milankovitch summer mid july insolation forces northern hemisphere ice sheets at the obliquity and precession periods with an ice time constant derived here of 10 000 years changes in ice volume at 41 000 years drive ice proximal signals sst nadw dust that produce a strong positive co 2 feedback and further amplify ice volume changes at the precession period july insolation forces ice sheets but it also drives fast and early responses in ch 4 through changes in tropical monsoons and boreal wetlands and variations in co 2 through southern hemisphere processes these ch 4 and co 2 responses enhance insolation forcing of ice volume climatic responses at 100 000 years result from eccentricity pacing of forced processes embedded in obliquity and precession cycles increased modulation of precession by eccentricity every 100 000 years produces 23 000 year co 2 and ch 4 maxima that enhance ablation caused by summer insolation and drive climate deeper into an interglacial state when eccentricity modulation decreases at the 100 000 year cycle ice sheets grow larger in response to obliquity forcing and activate a 41 000 year co 2 feedback that drives climate deeper into a glacial state alternation of these forced processes because of eccentricity pacing produces the 100 000 year cycle the 100 000 year cycle began 0 9 myr ago because gradual global cooling allowed ice sheets to survive during weak precession insolation maxima and grow large enough during 41 000 year ice volume maxima to generate strong positive co 2 feedback the natural orbital scale timing of these processes indicates that ice sheets should have appeared 6000 3500 years ago and that co 2 and ch 4 concentrations should have fallen steadily from 11 000 years ago until now but new ice did not appear and co 2 and ch 4 began anomalous increases at 8000 and 5000 years ago respectively human generation of co 2 and ch 4 is implicated in these anomalous trends and in the failure of ice sheets to appear in canada

neoglacial history of the stikine iskut area northern coast mountains british columbia information about neoglacial features was obtained from aerial photograph interpretation observations during low level flights ground checking and historical records terminal moraines at great flood and mud glaciers date from the late seventeenth to early eighteenth centuries and recessional moraines at these glaciers and terminal moraines at glaciers farther east date from the late nineteenth to early twentieth centuries these late neoglacial terminal moraines appear in general to mark the greatest post pleistocene extent of the glaciers radiocarbon dates from overridden trees and soil indicate that 500 600 14c years bp glaciers were considerably more extensive than they are at present and were advancing preservation of a 3800 14c year old caribou antler in a snowbank that is now rapidly shrinking suggests that climate has been relatively cool and moist for the past four millennia

holocene and latest pleistocene fluctuations of stutfield glacier canadian rockies the holocene and late glacial history of fluctuations of stutfield glacier are reconstructed using moraine stratigraphy tephrochronology and dendroglaciology stratigraphic sections in the lateral moraines contain tills from at least three glacier advances separated by volcanic tephras and paleosols the oldest pre mazama till is correlated with the crowfoot advance dated elsewhere to be younger dryas equivalent a neoglacial till is found between the mazama tephra and a paleosol developed on the bridge river tephra a log dating 2400 bp from the upper part of this till indicates that this glacier advance correlated with the peyto advance culminated shortly before deposition of the bridge river tephra radiocarbon and tree ring dates from overridden trees exposed in moraine sections indicate that the initial cavell little ice age lia advance overrode this paleosol and trees after a d 1271 three subsequent phases of the cavell advance were dated by dendrochronology the maximum glacier extent occurred in the mid 18th century predating 1743 on the southern lateral although ice still occupied and tilted a tree on the north lateral in 1758 subsequent glacier advances occurred ca 1800 1816 and in the late 19th century the relative extent of the lia advances at stutfield differs from that of other major eastward flowing outlets of the columbia icefield which have maxima in the mid late 19th century this is the first study from the canadian rockies to demonstrate that the large morphologically simple lateral moraines defining the lia glacier limits are actually composite features built up pro gressively but discontinuously over the holocene and contain evidence of multiple holocene and crowfoot age gla cier advances resume la stratigraphie des moraines la tephrochronologie et la dendroglaciologie des moraines ont servi a recons truire les fluctuations a l holocene et au cours de l histoire glaciaire tardive du glacier stutfield les sections stratigra phiques dans les moraines laterales contiennent des tills d au moins trois avancees glaciaires separees par des tephras volcaniques et des paleosols le plus ancien le till pre mazama est correle a l avancee crowfoot dont on a determine l ge ailleurs comme etant un equivalent du dryas recent un till de l epoque neo glaciaire se retrouve entre le tephra mazama et un paleosol developpe sur le tephra de bridge river un billot date 2400 bp provenant de la partie supe rieure de ce till indique que cette avancee glaciaire correlee a l avancee de peyto a culmine peu de temps avant la deposition du tephra de bridge river des datations au 14 c et des series chronlogiques provenant d arbres recouverts puis exposes dans des sections de moraine indiquent que l avancee cavell initiale petit ge glaciaire a chevauche ce paleosol et les arbres apres l an 1271 la dendrochronologie a permis la datation de trois phases subsequentes de l avancee cavell l etendue glaciaire maximale eut lieu au milieu du 18e siecle avant 1743 sur le cote sud bien que la glace fut encore presente sur le cote nord et y ait bascule un arbre en 1758 des avancees glaciaires subsequentes ont eu lieu vers 1800 1816 et vers la fin du 19e siecle l etendue relative des avancees du petit ge glaciaire a stutfield differe de celles d autres glaciers majeurs du champ de glace columbia s ecoulant vers l est et qui ont eu leur maxi mum dans la deuxieme moitie du 19e siecle cette etude est la premiere provenant des rocheuses canadiennes a de monter que les grandes moraines laterales morphologiquement simples definissant les limites du glacier au petit ge glaciaire sont en fait des elements composites developpes progressivement mais de facon discontinue tout au cours de l holocene et qu elles contiennent des evidences d avancees glaciaires multiples d ge holocene et crowfoot

reduced ice extent on the western antarctic peninsula at 700 970 cal yr b p rapid warming and consequent ice shelf collapse have focused attention on the glacial record of the antarctic peninsula here we present the first record of terrestrial organic material exposed by recently retreating ice that bears on past glacier extent and climate in this sensitive region radiocarbon dates show that ice on anvers island was at or behind its present position at 700 970 cal yr b p coincident with ice reduction elsewhere in the southern hemisphere moreover the data indicate that present reduced ice extent on the western antarctic peninsula is not unprecedented and is similar to that experienced during at least three periods in the last 5600 yr

evidence for a neoglacial advance of the boundary glacier banff national park alberta direct evidence for an early neoglacial advance in the canadian rocky mountains is presented radiocarbon dates from buried peat and tree remains at boundary glacier suggest limiting dates for this advance of between 3800 and 4200 years bp these data from boundary glacier are consistent with previously published dates for the onset of the neoglacial and an early neoglacial advance

late holocene glacier variations in the frontal and inner ranges of the tian shan central asia evidence for the timing and extent of late holocene glacial advances in the tian shan mountains central asia is based on lichenometric and radiocarbon dating of end moraines three phases of glacial advance occurred at 1700 2100 and 1100 1300 lichenometric l years ago and then during the little ice age 150 700 l years ago differences in the pattern of glacier variations between the northwestern frontal and inner areas of the tian shan are reflected in the equilibrium line altitude ela depression of 23 glaciers studied at nine selected sites the peripheral glaciers appear to have been significantly more extensive during late holocene advances than the glaciers of the inner areas this difference seems to be explained by regional differences in humidification in the northwestern periphery of the tian shan the cold periods of the late holocene were more humid than the warm period of the mid holocene whereas in the inner areas the pattern of climate changes was the opposite a warm and hu

the onset of neoglaciation 6000 years ago in western mongolia revealed by an ice core from the tsambagarav mountain range glacier highstands since the last glacial maximum are well documented for many regions but little is known about glacier fluctuations and lowstands during the holocene this is because the traces of minimum extents are difficult to identify and at many places are still ice covered limiting the access to sample material here we report a new approach to assess minimal glacier extent using a 72 m long surface to bedrock ice core drilled on khukh nuru uul a glacier in the tsambagarav mountain range of the mongolian altai 4130 m asl 48 39 338 n 90 50 826 e the small ice cap has low ice temperatures and flat bedrock topography at the drill site this indicates minimal lateral glacier flow and thereby preserved climate signals the upper two thirds of the ice core contain 200 years of climate information with annual resolution whereas the lower third is subject to strong thinning of the annual layers with a basal ice age of approximately 6000 years before present bp we interpret the basal ice age as indicative of ice free conditions in the tsambagarav mountain range at 4100 m asl prior to 6000 years bp this age marks the onset of the neoglaciation and the end of the holocene climate optimum the ice free conditions allow for adjusting the equilibrium line altitude ela and derive the glacier extent in the mongolian altai during the holocene climate optimum based on the ela shift we conclude that most of the glaciers are not remnants of the last glacial maximum but were formed during the second part of the holocene the ice core derived accumulation reconstruction suggests important changes in the precipitation pattern over the last 6000 years during formation of the glacier more humid conditions than presently prevailed followed by a long dry period from 5000 years bp until 250 years ago present conditions are more humid than during the past millennia this is consistent with precipitation evolution derived from lake sediment studies in the altai

latest pleistocene and early holocene fluctuations of glaciers in the canadian and northern american rockies in the canadian and northern american rockies small scale fluctuations of glaciers during and after late wisconsinan deglaciation have been identified using stratigraphy of superimposed glacial deposits geomorphology and records of glacial advance in lake and peat sediments several authors have proposed that valley glacier readvances of relatively modest scale followed the late wisconsinan maximum evidence for some of these is difficult to evaluate from the literature and no deposits recording such readvances have been numerically dated several minimum limiting radiocarbon dates for deglaciation suggest ice had retreated to within a few tens of km of present limits by ca 12 ka bp and to very near present limits by ca 11 ka bp one or more minor glacial advances or stillstands during recession evidently occurred in valley heads prior to 11 ka bp part of the evidence consists of moraines a few km downvalley from subsequently emplaced little ice age and crowfoot moraines the piper lake moraine in the mission mountains of montana is overlain by glacier peak g tephra and thus has a minimum age of 11 200 14c years bp the crowfoot advance a minor advance of about the same magnitude as little ice age advances occurred between ca 11 300 and 10 000 14c years bp and is thought to be related to the younger dryas climatic reversal crowfoot moraines have been found from jasper national park on the north to the mission mountains on the south crowfoot elas were an average of 40 m lower than modern elas around the canada u s border there have been past proposals of significant early holocene glacial advances in the rockies i e after crowfoot time but before the lia but recent evidence indicates that glaciers then were less extensive than at present

alpine glaciers and permanent ice and snow patches in western canada approach their smallest sizes since the mid holocene consistent with global trends most alpine glaciers in the northern hemisphere reached their maximum extents of the holocene between ad 1600 and 1850 since the late 1800s however glaciers have thinned and retreated mainly be

calendar dated early little ice age glacier advance at robson glacier british columbia canada dendrochronological studies at robson and bennington glaciers have provided the first calendar dating of an early little ice age glacier advance in north america dates derived from in situ stumps indicate that robson glacier began over riding forest between c ad 1142 and 1150 and continued until at least ad 1350 the highest rates of glacier advance c 3 8 m yr 1 occurred between ad 1214 and 1261 based on a series of kill dates from in situ stumps between c ad 1142 1214 and 1261 1350 rates were somewhat lower at c 2 2 5 m yr 1 this glacier advance terminated upvalley of the little ice age maximum position of robson glacier and there is no evidence at this site for glacial events between ad 1350 and 1783 however two smaller glaciers in the robson area and the main tongue of small river glacier have outermost little ice age moraines that date from the first decades of the ad 1700s all glaciers examined in the mount robson area have several well developed moraines dating from the period c

substantial agreement on the timing and magnitude of late holocene ice cap expansion between east greenland and the eastern canadian arctic a commentary on lowell et al 2013

the alpine iceman and holocene climatic change abstract the finding of a prehistoric mummified corpse at the upper edge of the accumulation area of an alpine glacier together with its unique set of artifacts provided new information on glacier dimensions during the little known phases of major glacier shrinkage that characterized the warmest parts of the holocene the sudden burial of the corpse in a permanent snow cover occurred 5300 5050 cal yr b p indicating a significant climatic change that induced glacier expansion at the beginning of neoglaciation new geomorphologic data and two ams14c ages from buried soils suggest that the present glacier size following over 100 yr of shrinkage is comparable to that immediately preceding neoglaciation therefore we can deduce that the current global climatic warming may have interrupted the environmental conditions prevailing in the alps during neoglacial time restoring characteristics similar to those prevailing during theclimatic optimumthat were never achieved during the second half of the holocene

the sedimentary record of carboniferous rivers continuing influence of land plant evolution on alluvial processes and palaeozoic ecosystems abstract evidence from modern rivers and the deep time geological record attests to the fundamental importance of plant life for the construction of physical habitats within fluvial environments data from an extensive literature review and original fieldwork demonstrates that many landforms and geomorphic features of modern river systems appear in the palaeozoic stratigraphic record once terrestrial vegetation had adopted certain evolutionary advances for example stable point bars are associated with the onset of rooted plants in the siluro devonian and avulsive and anabranching fluvial systems become common at the same time as extensive arborescent vegetation in the carboniferous in this paper we demonstrate a correlation between the diversification of physical fluvial environments and the expansion of terrestrial fauna and flora with an emphasis on the culmination of these trends within carboniferous alluvial systems many extrinsic factors have been considered as possible controls on the evolutionary timelines of terrestrialization for organisms however a fundamental prerequisite for achieving terrestrial biodiversity was the variety of physical habitats especially riparian systems available for newly evolved organisms in association with abundant lowland meandering systems the widespread appearance across carboniferous alluvial plains of fixed channel and anabranching reaches created further physical landforms for colonization and would have promoted increasingly complex hyporheic flow regimes furthermore the associated increase in arborescent vegetation and supply of large woody debris to inland and coastal rivers would have created a wealth of microhabitats for continental organisms we argue that the expanding extent and diversity of physical alluvial niches during the palaeozoic is an underappreciated driver of the terrestrialization of early continental life the study of the deep time fossil and stratigraphic record also illustrates that vegetation is a fundamental prerequisite for the creation of biogeomorphic alluvial landforms and physical habitats and microhabitats

neoglacial glacier fluctuations in the canadian rockies abstract the little ice age was the most extensive neoglacial glacier advance in the canadian rockies evidence of earlier less extensive neoglacial glacier advances is based on wood recovered from several glacier forefields wood flushed out of athabasca glacier 7550 8230 yr b p three dates and dome glacier 6120 6380 yr b p two dates indicates that forests occurred upvalley of present glacier termini during the hypsithermal detrital logs from peyto 14 dates saskatchewan 3 dates robson 3 dates and yoho 1 date glaciers plus in situ slumps at peyto and robson glaciers have yielded 14 c dates between 2490 and 3300 yr b p 12 dates between 2800 and 2990 this wood is derived from sources at or upvalley from present glacier termini and represents forests overridden by glaciers between ca 3100 and 2500 yr b p treeline was higher than present immediately prior to this advance this advance which did not extend beyond the little ice age maximum position is designated the peyto advance and correlated with the tiedemann advance in western british columbia earliest little ice age advances at peyto and robson glaciers are dated ca 800 600 yr b p at positions ca 500 m upvalley from little ice age limits

glacier fluctuations in extratropical south america during the past 1000 years article i nfo this paper presents an updated extensive review of glacier fluctuations during the past 1000 years in the extratropical andes of south america between ca 17 and 55 s given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range regional accounts are given for the desert andes 17 31 s the andes of central chile and argentina 31 36 s and the north 36 45 s and south 45 55 s patagonian andes the techniques dating limitations and interpretations of the glacier records along this transect are also discussed information on glacier fluctuations in the desert andes is limited to the 20th century documentation on past glacier variations is more abundant in the central chilean argentinean andes but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited most records indicate that glaciers were generally more extensive prior to the 20th century with dates of maximum expansion ranging from the 16th to the 19th centuries the number and extent of glaciers increase significantly in the patagonian region where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area for some patagonian glaciers maximum little ice age lia or post lia advances have been precisely dated by dendro geomorphological determinations or in situ measurements however for most sites the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum lia expansion identified in most areas between the 16th and 19th centuries evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium these events were generally less extensive than the lia maximum pulses despite the occurrence of several post lia readvances over the past 100 110 years most areas in the andes of extratropical south america have experienced a general pattern of glacier recession and significant ice mass losses the differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and or the dating techniques used in each case together with the varying dominance of precipitation temperature and other climatic and non climatic factors on glacier mass balance and glacier dynamics these differences indicate that the late holocene glacier history of southern south america is more complex than commonly assumed the evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed well dated records of glacier fluctuations

late holocene glacial activity in manatee valley southern coast mountains british columbia canada the dendroglaciologic and lichenometric research methodologies employed in this study provide a perspective of glaciological conditions from 5 ka to present in a remote headwater area of the british columbia coast mountains since holocene ice fronts of four glaciers at this site periodically extended below treeline previous glacier advances overrode and buried forests beneath till deposits this study suggests that glaciers were expanding into standing forests at 4 76 and 3 78 ka following glacier expansion at 3 78 ka a period of recession ensued when glaciers withdrew upvalley long enough for the development of deep pedogenic surfaces and the growth of trees exceeding 300 years investigations at beluga and manatee glaciers benchmark a subsequent episode of significant glacial expansion at 2 42 ka referred to as the manatee advance this advance has regional correlatives and is distinguished from the tiedemann advance at manatee glacier by documentation of substantive ice front retreat between the

the alps with little ice evidence for eight holocene phases of reduced glacier extent in the central swiss alps glacially deformed pieces of wood organic lake sediments and clasts of reworked peat have been collected in front of alpine glaciers since ad 1990 the palaeoglaciological interpretation of these organic materials is related to earlier phases of glacier recession surpassing that of today s shrunken glaciers and to tree growth and peat accumulation in the valleys now occupied by the glaciers glacial transport of the material is indicated by wood anatomy incorporated silt sand and gravel particles missing bark and deformed treerings a total of 65 samples have been radiocarbon dated so far and clusters of dates provide evidence of eight phases of glacier recession 9910 9550 9010 7980 7250 6500 6170 5950 5290 3870 3640 3360 2740 2620 and 1530 1170 calibrated years bp allowing for the timelag between climatic fluctuations glacier response and vegetation colonization these recession phases may lag behind climatic changes by 100 200 years

utilizing physical sediment variability in glacier fed lakes for continuous glacier reconstructions during the holocene northern folgefonna western norway the maritime plateau glacier of northern folgefonna in western norway has a short subdecadal response time to climatic shifts and is therefore well suited for reconstructing high resolution glac

climatic depositional and burial controls on diagenesis of appalachian carboniferous sandstones qualitative and quantitative methods abstract carboniferous quartz lithic and feldspar rich sandstones from different stratigraphic intervals within the central appalachian basin contain evidence for eogenetic and mesogenetic diagenesis important eogenetic products include fe oxide oxyhydroxide siderite kaolinite chlorite and calcite whereas quartz albite illite sericite fe carbonate and secondary porosity are the most important mesogenetic components correspondence and detrended correspondence analysis of the framework grain and diagenetic mineral data set has guided diagenetic interpretations and leads to two major conclusions first minerals that formed early appear to have been influenced by stratigraphic position the distribution of siderite and iron oxide oxyhydroxide is considered to reflect a second order paleoclimatic signature recognized throughout the carboniferous where siderite formed during everwet periods and iron oxide oxyhydroxide during semi arid conditions reflecting differences in redox second framework grain composition controlled the distribution of diagenetic products in the burial environment lithic arenites are deficient in authigenic quartz yet have undergone various degrees of illitization quartz deficiency is attributed to compaction related loss of primary porosity relatively early which inhibited sufficient fluid flow to account for much higher concentrations of quartz cement in the more competent quartz rich sandstones