erosional feedbacks and the oscillation of ice masses 1 an analytical solution to the development of a glacier or ice sheet in a region where the underlying rock rises steadily shows that the ice mass oscillates in size independefntly of changes in the climate in response to a feedback in which ice thickness is linked to topography by ice induced erosion the rate of vertical movement of the underlying rock uplift and the parameters governing ice erosion ablation and precipitation determine the period of oscillation two dimensional numerical simulations show that the tectonic uplift rate is the most important control on the period of oscillation and that the feedback period is likely to be between 10 and 100 kyr an examination of sediment data from the deep sea drilling project shows evidence of ice mass oscillations in the chugach st elias mountains and in the himalayas with periods consistent with those produced by the proposed mechanism localized changes in glacial extent may not therefore always be the consequence of climate change and care must be taken in interpreting evidence of glacial advance and retreat

a persistent and dynamic east greenland ice sheet over the past 7 5 million years 10be and 26al isotopic evidence in quartz sand from the seafloor shows that a dynamic east greenland ice sheet has existed for the past 7 5 million years understanding the growth and stability of the greenland ice sheet is a long standing priority in palaeoclimate research and one that is at the heart of modern discussion of sea level rise paul bierman and colleagues present marine records of cosmogenic isotopes and conclude that an ice sheet in east greenland was continuously eroding sediments over the past 7 5 million years although the method could miss transient deglaciations and cannot firmly distinguish between remnant and larger ice sheets the results are consistent with model simulations of a waxing and waning but continuously present regional ice sheet climate models show that ice sheet melt will dominate sea level rise over the coming centuries but our understanding of ice sheet variations before the last interglacial 125 000 years ago remains fragmentary this is because terrestrial deposits of ancient glacial and interglacial periods1 2 3 are overrun and eroded by more recent glacial advances and are therefore usually rare isolated and poorly dated4 in contrast material shed almost continuously from continents is preserved as marine sediment that can be analysed to infer the time varying state of major ice sheets here we show that the east greenland ice sheet existed over the past 7 5 million years as indicated by beryllium and aluminium isotopes 10be and 26al in quartz sand removed by deep ongoing glacial erosion on land and deposited offshore in the marine sedimentary record5 6 during the early pleistocene epoch ice cover in east greenland was dynamic in contrast east greenland was mostly ice covered during the mid to late pleistocene the isotope record we present is consistent with distinct signatures of changes in ice sheet behaviour coincident with major climate transitions although our data are continuous they are from low deposition rate sites and sourced only from east greenland consequently the signal of extensive deglaciation during short intense interglacials could be missed or blurred and we cannot distinguish between a remnant ice sheet in the east greenland highlands and a diminished continent wide ice sheet a clearer constraint on the behaviour of the ice sheet during past and ultimately future interglacial warmth could be produced by 10be and 26al records from a coring site with a higher deposition rate nonetheless our analysis challenges the possibility of complete and extended deglaciation over the past several million years

varied climatic and topographic influences on late pleistocene mountain glaciation in the western united states the timing of late pleistocene mountain glacier fluctuations varied widely across the western united states glaciers in the maritime olympic mountains reached local maxima 125 60 ka and 34 31 ka and were far less extensive during the global last glacial maximum lgm glaciers in the cascade mountains showed a similar general pattern but with contrasts in detailed timing most mountain glacier systems further inland exhibited maximum ice extent during marine isotope stage mis 2 in the wallowa wind river and possibly the sawtooth mountains maximum ice extent occurred ca 20 23 ka mountain glacier systems of the cordilleran ice sheet puget lobe greater yellowstone region and uinta mountains reached maximum extent ca 19 16 ka and those in the wallowa sawtooth and wind river ranges were at near maximum positions ca 17 ka the variable timing of maximum and near maximum ice advances appears to be related to climatic setting and glacier mass balance characteristics mountain glacier systems under the strongest maritime influences reached maximum extent at times of strong westerly atmospheric flow olympic and cascades glaciers appear to have been negatively influenced by weakened westerly flow at the time of the global lgm perhaps associated with ice sheet induced anticyclonic flow glacier systems with maximum advances correlative with the global lgm appear to have responded more strongly to depressed temperature the ca 17 ka ice advances of several glacier systems are broadly correlative with heinrich event 1 in the north atlantic region and imply a cooling event and reinvigoration of moisture transport into the region post lgm advances of uinta mountain glaciers appear to have arisen from moisture influences of pluvial lake bonneville copyright 2008 john wiley sons ltd

terrestrial cosmogenic surface exposure dating of moraines at lake tahoe in the sierra nevada of california and slip rate estimate for the west tahoe fault abstract two sets of pleistocene moraines tioga and tahoe are preserved at cascade lake along the west side of lake tahoe the 10 be terrestrial cosmogenic nuclide surface exposure ages for two younger tioga moraines yield an average age of 22 3 1 2 ka coincident with the global last glacial maximum the ages suggest that the tioga glaciation may have reached its maximum several thousand years earlier in the lake tahoe basin than to the south along the east flank of the sierra nevada the oldest 10 be age 120 8 ka determined for an additional suite of 10 boulders exhibiting significant scatter in 10 be ages is interpreted to be the minimum age of formation for older tahoe moraines in the tahoe basin suggesting they were deposited during marine oxygen isotope stage 6 the moraines at cascade lake are displaced by the west tahoe fault that strikes northward for 45 km along the western edge of the lake tahoe basin vertical displacements of the crests of the tahoe and tioga moraines are 59 10 and 32 12 m respectively averaged over the time since the formation of the tahoe and tioga moraines the average vertical separation rates are

isostatic uplift driven by karstification and sea level oscillation modeling landscape evolution in north florida isostatic uplift of tectonically stable passive margin lithosphere can preserve a record of paleo shoreline position by elevating coastal geomorphic features above the influence of nearshore wave activity conversely depositional ages and modern elevations of these features can provide valuable information about the uplift history of a region we present a numerical model that combines sea level oscillation subaerial exposure a precipitation karstification function and isostatic uplift to explore the dynamic geomorphic behavior of coastal carbonate landscapes over multiple sea level cycles the model is used to estimate ages of coastal highstand depositional features along the atlantic coast of north florida numerical simulations using current best estimates for pleistocene sea level and precipitation histories suggest ages for trail ridge 1 44 ma the penholoway terrace 408 ka and the talbot terrace 120 ka that are in agreement with fossil evidence in addition model results indicate that the rate of karstification void space creation or equivalent surface lowering rate within the north florida platform is 3 5 times that of previous estimates 1 m 11 2 k y vs 1 m 38 k y and uplift rate is 2 times as high as previously thought 0 047 mm yr vs 0 024 mm yr this process has implications for landscape evolution in other carbonate settings and may play an underappreciated role within the global carbon cycle

the quaternary glacial history of the lahul himalaya northern india this paper presents the first glacial chronology for the lahul himalaya northern india the oldest glaciation the chandra glacial stage is represented by glacially eroded benches at altitudes greater than 4300 m above sea level this glaciation was probably of a broad valley type the second glaciation the batal glacial stage is represented by highly weathered and dissected lateral moraines which are present along the chandra valley and some of its tributaries this was an extensive valley glaciation the third major glaciation the kulti glacial stage is represented by well preserved moraines in the main tributary valleys of the chandra valley this represents a less extensive valley glaciation two minor glacial advances the sonapani i and ii are represented by small sharp crested moraines which are within a few hundred metres or few kilometres of the present day glaciers the change in style and extent of glaciation is attributed to an increase in aridity throughout the quaternary due either to global climatic change or uplift of the pir panjal mountains to the south of lahul which restricted the northward penetration of the south asian summer monsoon 1996 john wiley sons ltd

insights into alpine moraine development from cosmogenic 36cl buildup dating abstract we have used cosmogenic 36cl surface exposure dating to determine apparent construction ages of late pleistocene moraines in the sierra nevada the white mountains and the wind river range all in the western united states the inferred glacial chronologies from the various localities all exhibit certain characteristics 1 local records are fragmentary and deposits of some glacial advances are always missing no location has deposits of all glaciations and no glacial advance is recorded at all locations this is due either to unfavorable conditions for glacier development at some times or to obliteration of earlier deposits by later more extensive glaciers 2 most moraines have young apparent exposure ages with only a few older than the last glacial cycle this may be due to young true ages of these deposits erosion of moraine surfaces or obliterative overlap and covering of older deposits by younger ones 3 many deposits that were previously correlated e g based on their stratigraphic positions are not correlative they may represent different stades and sometimes even different glaciations similarly some previously uncorrelated deposits have the same exposure ages and may be correlative 4 clusters of several distinct moraines of nearly the same age are present at most locations these clusters suggest that alpine moraines are formed during short deposition episodes that last between several hundred and several thousand years

glacial geology and chronology of bishop creek and vicinity eastern sierra nevada california the valley of bishop creek which drains part of the eastern flank of the sierra nevada california contains an unusually well preserved set of middle to late quaternary moraines these deposits have been mapped by previous investigators but they have not been quantitatively dated we used the accumulation of cosmogenic 36 cl to assign a chronology to the maximal glacial positions mapped in the valley our results indicate that the terminal moraines mapped by previous investigators as tahoe were all deposited between ca 165 and ca 135 ka during marine isotope stage mis 6 moraines mapped as tioga were deposited between 28 and 14 ka during mis 2 these can be subdivided into tioga 1 28 24 ka tioga 3 18 5 17 0 ka and tioga 4 16 0 14 5 ka advances no moraines dated to tioga 2 21 19 ka were found presumably because the tioga 3 advance either overrode or fluvially eroded them at 15 0 14 5 ka the tioga 4 glacier retreated abruptly to the crest of the range this was followed by the brief and fairly minor recess peak advance at ca 13 4 ka no holocene advances extended beyond the very restricted limits of ice during the matthes little ice age advance all preserved terminal moraines at lower elevations were deposited during either the tahoe or tioga stades the tahoe terminal moraines are extensive and voluminous whereas the tioga moraines are relatively narrow and have small volumes however this notable difference may be more a result of idiosyncrasies in the local glacial history than the result of differences in the length or intensity of glaciation between the two glacial episodes the history of glacial advances at bishop creek exhibits a strong correspondence to global climate cycles and to paleoclimate events in the north atlantic in particular

reconstruction of a complex late quaternary glacial landscape in the cordillera de cochabamba bolivia based on a morphostratigraphic and multiple dating approach abstract although glacial landscapes have previously been used for the reconstruction of late quaternary glaciations in the central andes only few data exist for the eastern cordillera in bolivia here we present results from detailed morphostratigraphic mapping and new data of surface exposure dating sed optically stimulated luminescence osl and radiocarbon dating 14 c from the huara loma valley cordillera de cochabamba bolivia discrepancies between individual dating methods could be addressed within the context of a solid geomorphic framework we identified two major glaciations the older is not well constrained by the available data whereas the younger glaciation is subdivided into at least four major glacial stages regarding the latter a first advance dated to 29 25 ka occurred roughly contemporaneous with the onset of the global last glacial maximum lgm and was followed by a less extensive re advance around 20 18 ka the local last glacial maximum llgm in the huara loma valley took place during the humid lateglacial 17 16 ka followed by several smaller readvances until 10 11 ka and complete deglaciation at the end of the early holocene

wave driven sediment transport and beach dune dynamics in a headland bay beach abstract this paper presents a comprehensive study of wave refraction wave and wind driven sediment transport foredune development and holocene barrier evolution over a variety of time scales at mocambique beach santa catarina state southern brazil the motivation for this study was to examine the relationships between estimated wave driven sediment transport medium and long term aeolian transport foredune development and holocene barrier volumes and morphology an analysis of 2 years of wave rider data for the region shows two well defined peaks of frequencies one of swell waves from the south with a period of 12 s and another peak of sea waves from east northeast with a period of 7 s longshore sediment transport rates were calculated using high resolution hindcast wave data for the south atlantic ocean which was calibrated by the measured buoy data the dominant southerly waves drive a longshore gradient in wave energy from south to north and nearshore surf zone sediment transport increases from south to north beach grain size is fine in both the south and north and medium in the center the combination of grain size and wave energy variations creates a marked alongshore variation in surf zone beach types ranging from low energy dissipative in the south moderate energy intermediate in the central area to moderate to high energy dissipative in the north estimates of aeolian sediment transport volumetric changes in foredune deposition and total holocene dunefield volumes were also calculated results indicate that the morphological behavior of the foredune profiles reflects the gradients of longshore sediment transport and the exposure to wind energy and aeolian sediment delivery with a maximum of sediment volume and transport towards and in the central part and northern end of the barrier holocene 0 7000 years barrier volumes vary along the embayment mimicking the trends in both calculated wave and wind driven sediment transport the short and hesp 1982 model was more suitable in predicting the long term holocene barrier evolution than the size and volume of the foredune the combination of wide beach high energy dissipation maximum sediment supply and high exposure to strong onshore winds is found in the northern end of the embayment where holocene subaerial barrier volumes are at a maximum overall this study proves that foredune development is closely related to wind exposure wave energy and gradients of longshore sediment transport and that dunefield development reflects the increase downdrift in potential sediment supply from the southern to the northern end of the beach and the change alongshore from low energy dissipative through intermediate to high energy dissipative beach surf zone environments this paper significantly extends previous models of beach and dune interactions in that it i actually determines wave driven sediment transport for various sections of a long embayment ii relates those transport patterns to surf zone beach morphodynamic types and variations in alongshore sediment patterns and iii correlates foredune volumes and holocene barrier volumes which reflect proxy holocene onshore transport rates with wave driven sediment transport rates

the response of glaciers to intrinsic climate variability observations and models of late holocene variations in the pacific northwest discriminating between glacier variations due to natural climate variability and those due to true climate change is crucial for the interpretation and attribution of past glacier changes and for the expectations of future changes we explore this issue for the well documented glaciers of mount baker in the cascades mountains of washington state usa using glacier histories glacier modeling weather data and numerical weather model output we find that natural variability alone is capable of producing kilometer scale excursions in glacier length on multi decadal and centennial timescales such changes are similar in magnitude to those attributed to a global little ice age the null hypothesis that no climate change is required to explain the glacier fluctuations in this setting cannot be rejected these results for mount baker glaciers are also consistent with an earlier study analyzing individual glaciers in scandinavia and the alps the principle that long timescale fluctuations of glacier length can be driven by short timescale fluctuations in climate reflects a robust and fundamental property of stochastically forced physical systems with memory it is very likely that this principle also applies to other alpine glaciers and that it therefore complicates interpretations of the relationship between glacier and climate history however the amplitude and timescale of the length fluctuations depends on the details of the particular glacier geometry and climatic setting and this remains largely unevaluated for most glaciers

characteristics of recessional moraines at a temperate glacier in se iceland insights into patterns rates and drivers of glacier retreat icelandic glaciers are sensitive to climate variability on short term timescales owing to their north atlantic maritime setting and have been undergoing ice marginal retreat since the mid 1990s recent patterns rates and drivers of ice frontal retreat at skalafellsjokull se iceland are examined using small scale recessional moraines as a geomorphological proxy these small scale recessional moraines exhibit distinctive sawtooth planform geometries and are constructed by a range of genetic processes associated with minor ice margin re advance including i combined push squeeze mechanisms ii bulldozing of pre existing proglacial material and iii submarginal freeze on remote sensing investigations and lichenometric dating highlight sequences of annually formed recessional moraines on the northern and central parts of the foreland conversely moraines are forming on a sub annual timescale at the southeastern skalafellsjokull margin using annual moraine spacing as a proxy for annual ice margin retreat rates imrrs we demonstrate that prominent periods of glacier retreat at skalafellsjokull are coincident with those at other icelandic outlet glaciers as well as those identified at greenlandic outlet glaciers analysis of imrrs and climate data suggests summer air temperature sea surface temperature and the north atlantic oscillation have an influence on imrrs at skalafellsjokull with the glacier appearing to be most sensitive to summer air temperature on the basis of further climate data analyses we hypothesise that sea surface temperature may drive air temperature changes in the north atlantic region which in turn forces imrrs the increase in sea surface temperature over recent decades may link to atmospheric driven variations in north atlantic subpolar gyre dynamics

chronology for fluctuations in late pleistocene sierra nevada glaciers and lakes mountain glaciers because of their small size are usually close to equilibrium with the local climate and thus should provide a test of whether temperature oscillations in greenland late in the last glacial period are part of global scale climate variability or are restricted to the north atlantic region correlation of cosmogenic chlorine 36 dates on sierra nevada moraines with a continuous radiocarbon dated sediment record from nearby owens lake shows that sierra nevada glacial advances were associated with heinrich events 5 3 2 and 1

asynchronous glaciations in arid continental climate abstract mountain glaciers at 26 19 ka during the global last glacial maximum near the end of the last 10 5 yr glacial cycle are commonly considered on the basis of dating and field mapping in several well studied areas to have been the largest of the late quaternary and to have advanced synchronously from region to region however a numerical sensitivity model rupper and roe 2008 predicts that the fraction of ablation due to melting varies across central asia in proportion to the annual precipitation the equilibrium line altitude of glaciers across this region likely varies accordingly in high altitude cold and arid regions sublimation can ablate most of the ice whereas glaciers fed by high precipitation cannot ablate completely due to sublimation alone but extend downhill until higher temperatures there cause them to melt we have conducted field studies and 10 be dating at five glaciated sites along a precipitation gradient in mongolia to test the rupper roe model the sites are located in nearby 1 875 1 875 cells of the rupper roe model each with a different melt fraction in this little studied region the modern environment of the sites ranges from dry subhumid in the north 47 7 n to arid in the south 45 n our findings show that the maximum local advances in the dry subhumid conditions predated the global last glacial maximum and were likely from mis 3 however we also found that at 8 7 ka a cirque glacier in one mountain range of the arid gobi desert grew to a magnitude comparable to that of the local maximum extent this holocene maximum occurred during a regional pluvial period thousands of years after the retreat of the pleistocene glaciers globally this asynchronous behavior is not predicted by the prevailing and generally correct presumption that glacier advances are dominantly driven by temperature although precipitation also plays a role our findings are consistent with and support the rupper roe model which calls for glaciation in arid conditions only at high altitudes of sub freezing temperatures where the melt fraction in ablation is low we expect a heterogeneous pattern of glacial responses to a changing modern climate in cold arid regions an individual glacier advance should not be necessarily interpreted as evidence of cooling climate

pleistocene lake outburst floods and fan formation along the eastern sierra nevada california implications for the interpretation of intermontane lacustrine records berin d i owen l a finkel r c clemmens s 2006 pleistocene lake outburst floods and fan formation along the eastern sierra nevada california implications for the interpretation of intermontane lacustrine records quaternary science reviews 25 2729 2748 sponsorship national science foundation grant ear 0207245

new geomorphological and chronological constraints for glacial deposits in the rivoli avigliana end moraine system and the lower susa valley western alps nw italy our new dataset from the rivoli avigliana end moraine system the westernmost amphitheatre of the italian alps provides an important step towards understanding foreland reaching glaciations before and during the last glacial maximum lgm in the western alps 10be data from six boulders in pre lgm deposits gave ages between 26 8 2 1 and 41 2 1 9 ka based on morphological and pedological data we interpret the oldest age as a minimum age for the glacier advance s 10be results suggest that the lgm occurred in two major steps during the first at 24 0 1 5 ka several ridges were constructed demonstrating oscillation of the dora riparia glacier snout at the maximum position our data demonstrate a significantly larger lgm extent in the rivoli avigliana amphitheatre than shown on previous maps the maximum advance was followed by a short re advance of the glacier at 19 6 0 9 ka as recorded by 10be ages from boulders in lateral positions along the lower susa valley the maximum ice surface during the lgm was at 1000 920 m a s l in the final reach of the valley 560 620 m of elevation above the alluvial plain and at 620 340 m a s l at the continuous moraines in the amphitheatre

10 be exposure dating of the timing of neoglacial glacier advances in the ecrins pelvoux massif southern french alps alpine glacier variations are known to be reliable proxies of holocene climate here we present a terrestrial cosmogenic nuclide tcn based glacier chronology relying on 24 new be 10 exposure ages which constrain maximum neoglacial positions of four small to mid sized glaciers rateau lautaret bonnepierre and etages in the ecrins pelvoux massif southern french alps glacier advances marked by mainly lateral moraine ridges that are located slightly outboard of the little ice age lia c 1250 1860 ad maximum positions were dated to 4 25 0 44 ka 3 66 0 09 ka 2 09 0 10 ka c 1 31 0 17 ka and to 0 92 0 02 ka the 4 2 ka advance albeit constrained by rather scattered dates is to our knowledge exposure dated here for the first time in the alps it is considered as one of the first major neoglacial advance in the western alps in agreement with other regional paleoclimatological proxies we further review alpine and northern hemisphere mid to high latitude evidence for climate change and glacier activity concomitant with the 4 2 ka event the 2 1 ka advance was not extensively dated in the alps and is thought to represent a prominent advance in early roman times other neoglacial advances dated here match the timing of previously described alpine neoglacial events our results also suggest that a neoglacial maximum occurred at etages glacier 0 9 ka ago i e during the medieval climate anomaly mca c 850 1250 ad at rateau glacier discordant results are thought to reflect exhumation and snow cover of the shortest moraine boulders overall this study highlights the need to combine several sites to develop robust neoglacial glacier chronologies in order to take into account the variability in moraine deposition pattern and landform obliteration and conservation

calendar dated glacier variations in the western european alps during the neoglacial the mer de glace record mont blanc massif holocene glacier records from the western european alps are still sparse although a number of sites are well suited to constraining pre and early little ice age lia glacier advances the present study provides the first dendrochronologically based and calendar dated neoglacial glacier chronology for the mont blanc massif french alps it is based on the analysis of over 240 glacially buried pinus cembra subfossil logs and wood remains found either embedded in till or as detrital material in the mer de glace right lateral moraine only a few of the samples were found to be formally in situ but we show that some logs were virtually in situ not rooted but showing little or no evidence of reworking and could be used to accurately reconstruct past glacier margin behavior in space and time uncertainties regarding the other samples may relate to original growth location and or to outer wood decay the resulting dates followed by a were therefore considered maximum limiting ages for glacier advances the main burial events interpreted as glacier advances occurred between ca 1655 and 1544 bc between ca 1230 and 1105 bc between ca 1013 and 962 937 bc at ca 802 777 bc after 608 bc between 312 and 337 ad between ca 485 ad and 606 ad between 1120 and 1178 ad between ca 1248 and 1278 1296 ad and after 1352 ad these advances predate the late lia maxima known from historical sources the magnitude of the advances gradually increased to culminate in three near neoglacial maxima during the 7th 12th and 13th centuries ad followed by a first lia neoglacial maximum in the second half of the 14th century ad the pattern of neoglacial events described here is coherent with central and eastern alpine glacier chronologies this indicates marked synchronicity of late holocene glacier variability and forcing at a regional scale although occasional differences could be detected between western and eastern records the mer de glace record also confirms the link between the timing of sediment erosion in a high elevation glaciated alpine catchment and subsequent deposition in the sub alpine lake bourget

high frequency holocene glacier fluctuations in the himalayan tibetan orogen abstract holocene glacial chronostratigraphies in glaciated valleys spread throughout the himalayan tibetan orogen including the himalaya tibet pamir and tian shan are developed using a landsystems approach detailed geomorphic mapping and new and published 10be surface exposure dating new studies in the kulti valley of lahul and the parkachik valley of the nun kun massif of the himalaya of northern india define three glacier advances at 14 7 12 2 0 5 ka in addition to one historically dated late 19th century advance in the kulti valley and one late holocene advance at 0 2 ka in the parkachik valley three major climatic groups subdivided into five climatic zones are defined across the orogen using cluster analysis ca and principal component analysis pca to identify glaciated regions with comparable climatic characteristics to evaluate the timing and extent of holocene glacier advances across these regions our regional analyses across the himalayan tibetan orogen suggest at least one lateglacial 15 3 11 8 ka and five himalayan tibetan holocene glacial stages hths at 11 5 9 5 8 8 7 7 7 0 3 2 2 3 1 0 and

cosmogenic dating of late pleistocene glaciation southern tropical andes peru we present 30 10be dates on three moraines formed by small glaciers in the southern tropical andes of peru to determine the timing of the local last glacial maximum lgm and subsequent deglaciation two terminal moraines indicate that the local lgm ended at 23 5 0 5 and 21 2 0 8 ka or well before the end of the global lgm 20 19 ka a recessional moraine perched at the base of a steep valley wall has a 10be age of 19 8 0 3 ka suggesting that glaciers had largely retreated from the area during the earliest stages of the last termination and before the onset of the deglacial co2 rise and increase in tropical sea surface temperatures these ages generally agree with other tropical glacial chronologies and reflect a broad synchroneity between low and high latitude deglaciation at the lgm but the trigger for early deglaciation of the tropics remains unclear

10be exposure age chronology of the last glaciation in the krkonose mountains central europe abstract a new chronology of the last glaciation is established for the krkonose giant mountains central europe based on in situ produced 10be in moraine boulders exposure ages and schmidt hammer rebound values obtained for terminal moraines on the northern and southern flank of the mountains suggest that the oldest preserved moraines represent early phases of the last glacial maximum lgm large moraines at the outlet of the snowy cirques niezne kotly and in the middle part of the upa ob i d l trough were deposited around 21 ka while a series of smaller moraines above the lgm deposits represent readvances that occurred no later than 18 1 0 6 ka 15 7 0 5 ka 13 5 0 5 ka and 12 9 0 7 ka an exposure age of 13 8 0 4 ka obtained for protalus ramparts at the foot of the upska jama cirque headwall indicates that glaciers advanced only in north to east facing cirques during the lateglacial the last glacier fluctuation was synchronous with the younger dryas cold event the timing of local glacier advances during the last glacial episode correlates with the late weichselian glacier phases in the alps and in the bavarian bohemian forest

cosmogenic exposure age chronologies of pinedale and bull lake glaciations in greater yellowstone and the teton range usa abstract we have obtained 69 new cosmogenic 10be surface exposure ages from boulders on moraines deposited by glaciers of the greater yellowstone glacial system and teton range during the middle and late pleistocene these new data combined with 43 previously obtained 3he and 10be ages from deposits of the northern yellowstone outlet glacier establish a high resolution chronology for the yellowstone teton mountain glacier complexes boulders deposited at the southern limit of the penultimate ice advance of the yellowstone glacial system yield a mean age of 136 13 10be ka and oldest ages of 151 157 10be ka these ages support a correlation with the bull lake of west yellowstone with the type bull lake of the wind river range and with marine isotope stage mis 6 end moraines marking the maximum pinedale positions of outlet glaciers around the periphery of the yellowstone glacial system range in age from 18 8 0 9 to 16 5 1 4 10be ka and possibly as young as 14 6 0 7 10be ka suggesting differences in response times of the various ice cap source regions moreover all dated pinedale terminal moraines in the greater yellowstone glacial system post date the pinedale maximum in the wind river range by 4 6 kyr indicating a significant phase relationship between glacial maxima in these adjacent ranges boulders on the outermost set and an inner set of pinedale end moraines enclosing jenny lake on the eastern teton front yield mean ages of 14 6 0 7 and 13 5 1 1 10be ka respectively the outer jenny lake moraines are partially buried by outwash from ice on the yellowstone plateau hence their age indicates a major standstill of an expanded valley glacier in the teton range prior to the younger dryas followed closely by deglaciation of the yellowstone plateau these new glacial chronologies are indicative of spatially variable regional climate forcing and temporally complex patterns of glacier responses in this region of the rocky mountains during the pleistocene

holocene cirque glacier activity in western spitsbergen svalbard sediment records from proglacial linnevatnet holocene glacial variations of a presently ice free cirque in western spitsbergen are inferred from sediment records from the proglacial lake linnevatnet glaciation is indicated in the core records by increased intensity of laminae derived from the cirque inflow and by increase in sediment accumulation rate radiocarbon ages on terrestrial plant macrofossils limit the onset of glaciation in the cirque to within the last six centuries no evidence for earlier glaciation is recognized in the core records indicating that the threshold for glaciation in the cirque was not reached during prior neoglacial advances local climate events favouring glacier expan sion were either of greater magnitude or of longer duration during the little ice age than at any other time during the holocene

constraining quaternary ice covers and erosion rates using cosmogenic 26 al 10 be nuclide concentrations abstract paired cosmogenic nuclides are often used to constrain the exposure burial history of landforms repeatedly covered by ice during the quaternary including tors high elevation surfaces and steep alpine summits in the circum arctic regions the approach generally exploits the different production rates and half lives of 10 be and 26 al to infer past exposure burial histories however the two stage minimum limiting exposure and burial model regularly used to interpret the nuclides ignores the effect of variable erosion rates which potentially may bias the interpretation in this study we use a monte carlo model approach to investigate systematically how the exposure burial and erosion history including variable erosion and the timing of erosion events influence concentrations of 10 be and 26 al the results show that low 26 al 10 be ratios are not uniquely associated with prolonged burial under ice but may as well reflect ice covers that were limited to the coldest part of the late pleistocene combined with recent exhumation of the sample e g due to glacial plucking during the last glacial period as an example we simulate published 26 al 10 be data from svalbard and show that it is possible that the steep alpine summits experienced ice free conditions during large parts of the late pleistocene and varying amounts of glacial erosion this scenario which contrasts with the original interpretation of more or less continuous burial under non erosive ice over the last 1 myr thus challenge the conventional interpretation of such data on the other hand high 26 al 10 be ratios do not necessarily reflect limited burial under ice which is the common interpretation of high ratios in fact high 26 al 10 be ratios may also reflect extensive burial under ice combined with a change from burial under erosive ice which brought the sample close to the surface to burial under non erosive ice at some point during the mid pleistocene importantly by allowing for variable erosion rates the model results may reconcile spatially varying 26 al 10 be data from bedrock surfaces preserved over multiple glacial cycles suggesting that samples from the same high elevation surface or neighbouring alpine summits may have experienced similar long term burial under ice but varying amounts of glacial erosion

can glacial erosion limit the extent of glaciation kaplan m r hein a s hubbard a 2009 can glacial erosion limit the extent of glaciation geomorphology 103 2 172 179

nature and timing of quaternary glaciation in the himalayan tibetan orogen abstract much effort has been made in recent years to define the timing and extent of quaternary glaciation throughout the himalayan tibetan orogen these studies are challenging because of the logistical and political inaccessibility of the region and the inherent problems associated with the application of numerical dating techniques nevertheless the studies are providing abundant evidence for significant glacial advances throughout the last several glacial cycles and are beginning to accurately define the extent and timing of glaciation in selected regions studies are showing that himalayan tibetan glaciers in arid regions during the last glacial cycle reached their maximum extent early in the cycle and that global last glacial maximum glacier advances were significantly less extensive however along the more monsoonal influenced greater himalaya there is increasing evidence to suggest that glaciation was more extensive later in the last glacial cycle but this has yet to be fully assessed in addition the new studies are showing that throughout most himalayan tibetan regions significant glacier advances occurred during the lateglacial and early holocene with minor advances in some regions during the mid holocene the still relatively poor chronological control in the himalayan tibetan orogen however makes it difficult to construct correlations across the region and with regions elsewhere in the world this in turn makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation across the himalayan tibetan orogen and to quantify paleoclimate change in this high altitude subtropical region the lateglacial and holocene glacial records however are particularly well preserved in several himalayan tibetan regions glacial successions such as these have the greatest potential to be examined in detail using newly developing numerical dating and geomorphic and sedimentologic methods to derive high resolution terrestrial records of glaciation that will help in paleoclimatic reconstruction for high altitude subtropical regions

assessing climatic and nonclimatic forcing of pinedale glaciation and deglaciation in the western united states new 10 be surface exposure ages from adjacent valleys in the upper arkansas river basin colorado united states indicate that pinedale maxima culminated asynchronously at 22 4 1 4 19 2 0 2 17 8 0 6 and 15 8 0 4 ka but that deglaciation initiated synchronously between ca 16 and 15 ka these data are combined with published glacial chronologies across the western united states and indicate that although the ages of pinedale terminal moraines vary within individual ranges as well as regionally most western united states glaciers remained near their pinedale termini until ca 16 ka at which time widespread deglaciation commenced we hypothesize that the near synchronous demise of glaciers across the western u s between ca 15 and ca 13 ka was driven by the first major northern hemisphere warming following the last glacial maximum but that some differences in pinedale culmination ages can be explained by nonclimatic factors intrinsic to individual valleys these results suggest the need for caution in focusing exclusively on climate forcings to explain apparent asynchrony in pinedale maxima

hillslope and channel evolution in a marine terraced landscape santa cruz california a flight of marine terraces along the central california coastline provides a unique setting for the study of topographic evolution wavecut platforms mantled by 2 6 m of marine terrace cover deposits are separated by 10 50 m tall decaying sea cliffs paleocliff edges become more rounded with age yet the details of the profiles and frequent bedrock exposure on the upper slopes imply weathering limited transport five bedrock stream channels etched through the marine terrace sequence display one to three distinct convexities in their longitudinal profiles detailed hand level surveys of the hillslopes and of the stream channel longitudinal profiles constrain hillslope evolution and channel incision components of a numerical model of landscape evolution we account for regolith production as a function of regolith depth in accord with the field observation that hillslope processes are presently dominated by the activities of burrowing rodents the transport process is taken to be diffusive stream incision is assumed to be controlled by stream power for which we use the surrogate of local drainage area slope product best fits of the numerical model to field data imply hillslope diffusivity is 10 m2 kyr 1 regolith production rate on bare bedrock is 0 3 m kyr 1 and falls off rapidly with regolith cover and the constant controlling the efficiency of stream incision is 5 to 7 10 7m 1 kyr1

a detailed study of the distribution of heat flow and radioactivity in new hampshire u s a abstract we present a set of 39 new determinations of heat flow and radiogenic heat production for several different geological environments in the state of new hampshire u s a with the extensive data set now available for the state the linear relation of heat flow and heat production appears as a very useful generalization for the study of the heat flow field of a geological province our measurements indicate that the vertical distribution of radiogenic heat production is similar in plutonic and metasedimentary rocks our data are compatible with the linear relationship established earlier by f birch and his co workers in 1968 young granites are markedly enriched in radioactive elements and those which do not outcrop are revealed by anomalies in the general relation of heat flow versus radioactivity heat flow is high for plutons by low elsewhere the mean heat flow through metasedimentary formations is 1 15 cal cm2 s 48 mw m2 a value near the mean heat flow for old cratons the lowest heat flow measured is 0 76 cal cm2 s 32 mw m2 for a unit poor in radioactivity the heat flow field grades smoothly into the low heat flow regions of the canadian shield the new hampshire region is in thermal equilibrium its heat flow is in secular equilibrium with the heat generated by crustal sources and that supplied from the mantle in this area the thermal perturbations due to orogenic events decrease below the detection level in less than 200 275 ma the thickness of the layer which is thermally affected during continent continent collision type orogenies cannot be greater than about 190 km

genesis stability and preservation potential of large lateral moraines of alpine valley glaciers towards a unifying theory based on findelengletscher switzerland abstract lateral moraines are prominent features of glaciated landscapes in high mountain environments and key landforms in glacier and palaeoclimatic reconstructions yet compared to smaller moraines they have been little studied and several aspects are not well understood we here present detailed sedimentological results from the lateral moraines of findelengletscher in sw switzerland to gain new insights into the formation of these landforms the lateral moraines studied here stand up to 140 m above the valley floor are over 3 km long and strongly asymmetrical in cross profile with distal slopes between 29 and 36 and proximal slopes that are commonly 41 64 but locally reach angles of up to 80 recorded lithofacies comprise loose clast and matrix supported stratified diamicts and intercalated sorted sediments in the distal slopes and near the crestline overconsolidated matrix supported massive and weakly stratified diamicts and streaked out sorted sediment lenses in the core and proximal slopes and partly intercalated dark brown layers overlain by loose and consolidated diamicts exposed in near vertical walls in the proximal flank these are interpreted as supraglacial debris flow units with intercalated fluvial wash horizons glaciotectonised and subglacial traction till with boudinaged and streaked out sediment lenses and palaeosoils overlain by sediment produced by overtopping of the former moraine surface during a subsequent advance of the glacier clast shape analysis and process observations reveal that the dominant mode of transport is subglacial and glaciofluvial and that the main mode of sediment delivery to the moraines is by debris flows after the material has been transferred from the bed via englacial debris bands and meltout at the surface this differs from previous studies that found that a supraglacial source was dominant sedimentary structures clast fabric and process observations during the 1979 1980 readvance of findelengletscher strongly suggest that proximal layers of reworked pre existing sediments and or basal traction zone till have been plastered onto the moraine core in several locations causing a high degree of overconsolidation and strongly clustered fabric eigenvalues s 1 0 94 with clustering parallel to the moraine crestline this suggests that a combination of basal lateral drag and lateral plastering produces the observed proximal stability and ensures a high preservation potential we develop a conceptual model that describes alpine lateral moraines as structurally complex landforms that do not just record a single event as often surmised and we discuss implications for palaeo glacier reconstruction and the application of numerical dating methods

correlation of late quaternary moraines impact of climate variability glacier response and chronological resolution abstract the last decade has seen a global surge in the number and resolution of well dated geomorphological reconstructions of mountain glacier fluctuations and former ice sheet extents this has been facilitated by the widespread deployment of large samples of terrestrial cosmogenic nuclide dating tcnd allowing more sophisticated probability analyses for reducing the statistical uncertainty of moraine ages and testing of correlations at local regional and hemispheric scales geochronological advances in the field laboratory and on model calibration have taken place in parallel with modelling of palaeoclimate based on glacier reconstructions and of glacier sensitivity to temperature and precipitation forcing in spite of these advances basic conceptual issues remain this review questions whether the technical leap forward in dating has encouraged us to over reach our interpretive limits particularly in terms of the concept and practice of correlation we propose that to enable reliable correlation glacier chronologies should first be examined for their climatic integrity spatial coherence and chronological robustness even with excellent dating interpretive complexity remains due to complex climate signals and glacier response characteristics and to erosion censoring of the landform record all are issues which must be addressed to avoid either spurious lumping correlation or splitting differentiation of glacier chronologies and thus misinterpretation of the climatic significance of reconstructed glacier advances we suggest that the reliability of correlation is no better than the weakest link in the chain of reasoning which connects climatic fluctuations with dated landforms and sediments improved dating means that poor chronological resolution is less likely to be the limiting factor for correlation but shifts the focus onto other less quantifiable sources of uncertainty these conceptual statements are exemplified with reference to holocene glacial chronologies of contrasting mid latitude environments in southern norway iceland and new zealand

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

timing and process of river and lake terrace formation in the kyrgyz tien shan abstract well preserved flights of river and lake terraces traverse an actively deforming rangefront and form a link between glaciated mountains and a large intermontane lake in the issyk kul basin of the kyrgyz tien shan we investigated the history and geometry of these lake and river terraces using geologic mapping surveying and radiocarbon and terrestrial cosmogenic nuclide dating a prominent late pleistocene highstand of the lake occurred over at least the period of 43 25 ka followed by a period of deep regression and subsequent rise of the lake to the modern sill level in the late holocene major aggradation of the most prominent latest quaternary river terrace along the ak terek and barskaun rivers likely started at 70 60 ka coincident to the local last glacial maximum in this region in contrast to some models of aggradation and incision the rivers appear to have stayed near the top of the fill for 20 ka incising subtly below the top of this fill by 37 ka locally deep incision likely did not occur until the peak deglaciation in the latest pleistocene older dated terrace surfaces are consistent with one major terrace forming event per glacial constant deformation and incision rates and typical fluvial gradients lower than the modern incising streams the dating confirms regional terrace correlations for the most prominent late quaternary terraces but correlating higher terraces is complicated by spatially varying uplift rates and preferential terrace preservation between basins in the tien shan

numerical modeling of fluvial strath terrace formation in response to oscillating climate many river systems in western north america retain a fluvial strath terrace rec ord of discontinuous downcutting into bedrock through the quaternary their importance lies in their use to interpret climatic events in the headwaters and to determine long term incision rates terrace formation has been ascribed to changes in sediment supply and or water discharge produced by late quaternary climatic fluctuations we use a one dimensional channel evolution model to explore whether temporal variations in sediment and water discharge can generate terrace sequences the model includes sediment transport vertical bedrock erosion limited by alluvial cover and lateral valley wall erosion we set limits on our modeling by using data collected from the terraced wind river basin two types of experiments were performed constant period sinusoidal input histories and variable period inputs scaled by the marine 18 o rec ord our simulations indicate that strath terrace formation requires input variability that produces a changing ratio of vertical to lateral erosion rates straths are cut when the channel floor is protected from erosion by sediment and are abandoned and terraces formed when incision can resume following sediment cover thinning high sediment supply promotes wide valley floors that are abandoned as sediment supply decreases in contrast wide valleys are promoted by low effective water discharge and are abandoned as discharge increases widening of the valley floors that become terraces occurs over many thousands of years the transition from valley widening to downcutting and terrace creation occurs in response to subtle input changes affecting local divergence of sediment transport capacity formation of terraces lags by several thousand years the input changes that cause their formation our results suggest that use of terrace ages to set limits on the timing of a specific event must be done with the knowledge that the system can take thousands of years to respond to a perturbation the incision rate calculated in the field from the lowest terrace in these systems will likely be higher than the rate calculated by using older terraces because the most recent fluvial response in the field is commonly downcutting associated with declining sediment input since the last glacial maximum this apparent increase in incision rates is observed in many river systems and should not necessarily be interpreted as a response to an increase in rock uplift rate

cosmogenic 3he ages and frequency of late holocene debris flows from prospect canyon grand canyon usa abstract lava falls rapid which was created and is maintained by debris flows from prospect canyon is the most formidable reach of whitewater on the colorado river in grand canyon and is one of the most famous rapids in the world debris flows enter the colorado river at tributary junctures creating rapids the frequency of debris flows is an important consideration when management of regulated rivers involves maintenance of channel morphology we used cosmogenic 3 he 14 c and historical photographs to date 12 late holocene and historic debris flows from prospect canyon the highest and oldest deposits from debris flows on the debris fan yielded a 3 he date of about 3 ka which indicates predominately late holocene aggradation of one of the largest debris fans in grand canyon the deposit which has a 25 m escarpment caused by river reworking crossed the colorado river and raised its base level by 30 m for an indeterminate although likely short period we mapped depositional surfaces of 11 debris flows that occurred after 3 ka two deposits inset against the highest deposit yielded 3 he ages of about 2 2 ka and at least two others followed shortly afterwards at least one of these debris flows also dammed the colorado river the most recent prehistoric debris flow occurred no more than 0 5 ka the largest historic debris flow which constricted the river by 80 occurred in 1939 five other debris flows occurred after 1939 these debris flows constricted the colorado river by 35 80 assuming the depositional volumes of late holocene debris flows can be modeled using a lognormal distribution we calculated recurrence intervals of 15 to more than 2000 years for debris flows from prospect canyon

multiple independent records of local glacier variability on nuussuaq west greenland during the holocene abstract the sensitivity of mountain glaciers to small scale climate fluctuations makes records of their past extent among the best proxies for identifying spatio temporal climate variability here we build on the few existing holocene records of local glacier change in greenland by using three independent geochronological methods proglacial lake sediment analysis cosmogenic 10be surface exposure dating and in situ 14c burial modeling to reconstruct continuous records of holocene glacier variability on nuussuaq west greenland 10be ages of perched boulders indicate eastern nuussuaq was deglaciated between 11 0 and 10 5 ka radiocarbon dated sediments from two lakes on nuussuaq contain mineral rich layers between 9 6 and 9 0 and 8 7 8 0 cal ka bp that may be correlative with nearby ice sheet moraines deposited in the early holocene multiple proxies for glacier size indicate frequent high amplitude glacier fluctuations superimposed on net glacier growth during the late holocene with significant ice expansion phases at 3 7 ka 2 8 ka and throughout the past 2 ka mean 10be ages from five nested moraine crests confirm that local glacier extents on nuussuaq culminated during both the little ice age 1470 c e n 3 and 1750 c e n 3 and the preceding centuries 520 1320 c e n 11 results reveal that local glaciers on nuussuaq episodically advanced and retreated at centennial timescales throughout the holocene most likely in response to regional climate changes in west greenland superimposed on the progressive insolation driven cooling trend in the northern hemisphere our new 10be moraine chronologies coupled with other glacier size proxies corroborate an emerging pattern of significant summer cooling and glacier expansion in the centuries prior to the little ice age in the arctic

probability of moraine survival in a succession of glacial advances emplacement of glacial moraines normally results in obliteration of any older moraines deposited by less extensive glacial advances a process we call obliterative overlap a probability analysis of the likely impact of obliterative overlap on the completeness of the glacial record assumes that moraines were deposited at various distances from their glacial source areas randomly over time assuming randomness and obliterative overlap after 10 glacial episodes the most likely number of surviving moraines is only three the record of the pleistocene is in agreement with the probability analysis the 10 glaciations during the past 0 9 m y inferred from the deep sea record resulted in moraine sequences in which only two or three different aged moraine belts can generally be distinguished

climatic implications of alternating clay and carbonate formation in semiarid soils of south central montana abstract evidence for climatic change is found in petrographic thin sections from soils formed on glaciofluvial deposits of rock creek and the lower clarks fork montana these soils presently in a semiarid climate range from late pliocene to holocene in age and have undergone periodic fluctuations in soil moisture caused by climatic changes in the lower parts of soil b horizons accretion of illuvial layers of clay argillans occurs mainly during wet glacial climatic periods whereas carbonate precipitates mainly during dry interglacial climatic periods thin section studies of the argillan and carbonate layers show that 1 post pinedale soils that have formed only in the present interglacial climate contain areas of secondary carbonate unrelated to argillans 2 soils formed on outwash of successively older glaciations contain proportionately more alternating layers of argillans and carbonate and 3 the maximum number and sequence of layers in a soil correspond to the number of local cycles of glacial outwash deposition and subsequent stream incision that followed the beginning of soil formation these cycles are inferred to correspond to local glacial interglacial fluctuations the correspondence between the microscopic record and the glacial outwash record for rock creek suggests that some of the climatic changes seen in the marine oxygen isotope record did not strongly affect the study area

a lacustrine based neoglacial record for glacier national park montana usa abstract multi proxy study of sediment cores retrieved from lakes below modern glaciers supports the first detailed neoglacial chronology for glacier national park gnp montana analysis focused on sedimentary properties sensitive to the extent and activity of upstream glacier ice including water organic matter carbonate and biogenic silica content bulk density mass accumulation rate phosphorus fractionation magnetic susceptibility l a b color values and grain size distribution results indicate that alpine glaciers in gnp advanced and retreated numerous times during the holocene after the onset of neoglaciation ca 6500 bp the two oldest phases of glacier expansion were synchronous with the well documented garibaldi 5600 6900 bp and tiedemann peyto 1900 3700 bp phases in western canada younger phases correspond with the first millennium advance in western canada as well as glacier with advances in the sierra nevada the culminating little ice age lia advance was the most recent and extensive of a series of advance retreat cycles over the past millennium retreat from the lia maximum was the most dramatic episode of ice retreat in at least the last 1000 years

holocene mountain glacier history in the sukkertoppen iskappe area southwest greenland abstract mountain glaciers and ice caps gic independent of the greenland ice sheet respond rapidly to climate variations and records of their past extent provide information on the natural envelope of climate variability here we use a multi proxy approach that combines proglacial lake sediment analysis cosmogenic nuclide surface exposure dating in situ 10be and 14c and radiocarbon dating of recently ice entombed moss to generate a centennial scale record of holocene gic fluctuations in southwestern greenland following local deglaciation 10 9 ka sediments from proglacial crash lake record a glacier advance at 9 ka that is indistinguishable from nearby ice sheet moraines implying a synchronous response of gic and the greenland ice sheet to a centennial scale climate event following this local glacier advance gic experienced net recession until 4 6 ka radiocarbon ages of in situ moss n 29 and crash lake sediments reveal intervals of glacier expansion at 1 8 1 2 and 0 7 ka that are superimposed on an overall trend of net glacier expansion throughout the late holocene in situ 14c concentrations from bedrock adjacent to radiocarbon dated moss samples further constrain the duration of ice cover through the holocene in this region we find that our glacier size proxy records during the past 4 ka are broadly consistent with relatively lower temperatures recorded in gisp2 and occur during or following intervals of volcanic perturbations thus we speculate that volcanic activity although less frequent and intense than in the early holocene and during the little ice age may have led to centennial scale variability imprinted on net glacier expansion due to decreasing summer insolation through the late holocene

holocene moraine chronology spitsbergen svalbard lichenometric evidence for multiple neoglacial advances in the arctic late holocene neoglacial moraines occurring within 1 or 2 km of present glacier margins are prominent features in the forefields of spitsbergen glaciers little ice age moraines are typically the most extensive and best preserved moraines of older holocene advances are much less common where observed older moraines occur as moraine remnants and provide irrefutable evidence of earlier neoglacial advances the fragmentary moraine record indicates two little ice age advances and two older neoglacial advances lichenometry provides calibrated ages for periods of moraine stabilization the oldest moraines stabilized by ca 1500 years ago and a second group of moraines stabilized by ca 1000 years ago little ice age moraines were deposited during two periods an early group of moraines stabilized ca 650 years ago and a later group during the last several centuries the proposed moraine chronology compares well with other proxy climate records on spitsbergen and with moraine records from areas borde

incipient axial collapse of the main cordillera and strain partitioning gradient between the central and patagonian andes lago laja chile 1 lago laja is a late quaternary volcanic dammed lake located near the drainage divide of the south central andes field observations lake reflection seismic profiles bathymetry and remote sensing data reveal an active fault system that runs parallel to the volcanic arc along the axis of the main cordillera the lago laja fault system llfs normal faults of this extensional system cut late pleistocene volcanics 2 7 mm yr since 7 1 ka the llfs accounts for 0 7 of arc normal extension at an average minimum rate of 1 2 mm yr and strain rate of 10 14 s 1 seismites and surface ruptures evidence m 6 paleoearthquakes the main cordillera at 37 s is a large scale pop up structure uplifted by thrusting along its foothills in this light we interpret extension in the axial and highest part of the andes as incipient synorogenic gravitational collapse in response to uplift and crustal thickening thermal weakening due to elevated heat flow and postglacial lithospheric rebound and unbending have probably contributed to the arc limited collapse and holocene acceleration of deformation rates the lack of significant strike slip offsets along the llfs as well as along both foothills thrust systems at 37 s contrasts with the intra arc dextral fault zone south of 38 s regional structural data indicates that north of 38 s diffusely distributed strain reflects low partitioning of oblique subduction while to the south deformation is localized in a discrete strike slip fault zone along the volcanic arc reflecting a higher degree of partitioning we relate this strain partitioning gradient to favorable fault orientations in the fore arc north of the arauco peninsula a major seismotectonic boundary

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

the effects of interannual climate variability on the moraine record valley glacier moraines are commonly used to infer past mean annual precipitation and mean melt season temperature however recent research has demonstrated that even in steady climates multi decadal kilometer scale fluctuations in glacier length occur in response to stochastic year to year variability in mass balance when interpreting moraine sequences it is important to include the effect of interannual weather variability on glacier length moraines record advances that are forced either by interannual variability or by a combination of climate change and interannual variability we address this issue for the last glacial maximum lgm glaciers of the colorado front range united states using a linear glacier model that allows thorough exploration of parameter uncertainties supplemented by a shallow ice flowline model our analyses suggest that 1 glacial standstills longer than 50 years were unlikely 2 mean glacier lengths are 10 15 up valley from maximum glacier lengths and 3 individual lgm terminal moraines were formed by a combination of a climate change and interannual variability forced advances

millennial scale pulsebeat of glaciation in the southern alps of new zealand abstract we undertook geomorphological mapping in conjunction with 10be surface exposure dating in a previously unstudied sector of the left lateral moraine sequence of the ice age pukaki glacier in the southern alps of new zealand the mapping and dating approach enabled the identification of six distinct moraine belts that were formed during maxima of glacier extent during the last glaciation the chronology implies that ice recession occurred during northern hemisphere heinrich stadials while expansion occurred between heinrich stadials the ages of the moraine belts identified here are 44 000 1000 yrs 41 800 1100 yrs 36 450 940 yrs 26 730 740 yrs 20 030 460 yrs and 18 000 400 yrs this moraine chronology is consistent with previous dating results from other sectors of the pukaki moraine sequence except that the c 44 000 yr old moraine belt has not previously been detected elsewhere in the pukaki moraines collectively with previously published 10be chronologies from the pukaki glacier and the adjacent ohau glacier valley the results demonstrate that there were several millennial scale episodes of ice advance to full glacial extent and subsequent ice recession during marine isotope stages 3 and 2 this millennial scale pulsebeat of oscillations of the pukaki and ohau glaciers in sympathy with the north atlantic heinrich episodes is further emphasized by rapid ice recession in the southern alps early in the last glacial termination coeval with the onset of heinrich stadial 1 hs 1 in the northern hemisphere that this pattern is widespread in mid latitudes of the southern hemisphere is highlighted by similar chronologies of glacier variation for andean ice lobes in the chilean lake district of south america

fingerprinting of glacial silt in lake sediments yields continuous records of alpine glaciation 35 15 ka western usa abstract fingerprinting glacial silt in last glacial age sediments from upper klamath lake ukl and bear lake bl provides continuous radiocarbon dated records of glaciation for the southeastern cascade range and northwestern uinta mountains respectively comparing of these records to cosmogenic exposure ages from moraines suggests that variations in glacial flour largely reflect glacial extent the two areas are at similar latitudes and yield similar records of glacial growth and recession even though ukl lies less than 200 km from the ocean and bl is in the continental interior as sea level began to fall prior to the global last glacial maximum lgm existing glaciers in the ukl area expanded near the beginning of the global lgm 26 5 ka the bl record indicates onset of glaciation and ukl area glaciers underwent further expansion both records indicate that local glaciers reached their maximum extents near the end of the global lgm remained near their maxima for 1000 yr and underwent two stages of retreat separated by a short period of expansion

neoglacial ice expansion and late holocene cold based ice cap dynamics on cumberland peninsula baffin island arctic canada abstract radiocarbon dating of fossil flora and fauna collected along receding cold based ice caps and cold based sections of polythermal glaciers on cumberland peninsula reveal insights into neoglacial ice expansion and late holocene ice dynamics the taphonomic advantages of subfossilized moss were exploited to precisely document regional expansions of ice caps through the late holocene when compared with climate proxies and records of volcanic eruptions the moss radiocarbon age distributions indicate i onset of neoglaciation shortly after 5 ka concomitant with increased sea ice cover ii intensification of ice expansion between 1 9 and 1 1 ka followed by halt of ice growth or ice recession during the medieval warm period and iii renewed ice expansion after 0 8 ka in response to cooling related to a combination of large volcanic eruptions and low solar activity overall the observations support a model of near instantaneous glacial response to regional climate controls and that these responses were synchronous throughout eastern canadian arctic and possibly eastern greenland

a review of topographic controls on moraine distribution ice marginal moraines are often used to reconstruct the dimensions of former ice masses which are then used as proxies for palaeoclimate this approach relies on the assumption that the distribution of moraines in the modern landscape is an accurate reflection of former ice margin positions during climatically controlled periods of ice margin stability however the validity of this assumption is open to question as a number of additional nonclimatic factors are known to influence moraine distribution this review considers the role played by topography in this process with specific focus on moraine formation preservation and ease of identification topoclimatic controls are not considered published literature indicates that the importance of topography in regulating moraine distribution varies spatially temporally and as a function of the ice mass type responsible for moraine deposition in particular in the case of ice sheets and ice caps 1000 km2 one potentially important topographic control on where in a landscape moraines are deposited is erosional feedback whereby subglacial erosion causes ice masses to become less extensive over successive glacial cycles for the marine terminating outlets of such ice masses fjord geometry also exerts a strong control on where moraines are deposited promoting their deposition in proximity to valley narrowings bends bifurcations where basins are shallow and or in the vicinity of topographic bumps moraines formed at the margins of ice sheets and ice caps are likely to be large and readily identifiable in the modern landscape in the case of icefields and valley glaciers 10 1000 km2 erosional feedback may well play some role in regulating where moraines are deposited but other factors including variations in accumulation area topography and the propensity for moraines to form at topographic pinning points are also likely to be important this is particularly relevant where land terminating glaciers extend into piedmont zones unconfined plains adjacent to mountain ranges where large and readily identifiable moraines can be deposited in the case of cirque glaciers 10 km2 erosional feedback is less important but factors such as topographic controls on the accumulation of redistributed snow and ice and the availability of surface debris regulate glacier dimensions and thereby determine where moraines are deposited in such cases moraines are likely to be small and particularly susceptible to post depositional modification sometimes making them difficult to identify in the modern landscape based on this review we suggest that despite often being difficult to identify quantify and mitigate topographic controls on moraine distribution should be explicitly considered when reconstructing the dimensions of palaeoglaciers and that moraines should be judiciously chosen before being used as indirect proxies for palaeoclimate i e palaeoclimatic inferences should only be drawn from moraines when topographic controls on moraine distribution are considered insignificant

use of lacustrine sedimentary sequences as indicators of holocene glacial history banff national park alberta canada abstract bottom sediments from three lakes in the canadian rocky mountains were examined with the aim of evaluating the usefulness of downvalley sediment studies in reconstruction of holocene glacial histories analyses of organic carbon and carbonate contents of core sediments provide information on changing sedimentation rate and changing relative importance of glacial and non glacial sediment sources sedimentary histories of the three lakes are similar suggesting that they record regional glacial climatic forcing rather than localized events and thus that they may be useful in reconstructing holocene glacial history lacustrine sediments indicate a period of high sedimentation rates and relatively large glacial sediment contribution prior to 7500 7000 yr b p with much reduced rates and decreased glacial sediment contribution between about 6000 and 4000 yr b p possibly interrupted by a brief period of increased glacial sediment output shortly after 5000 yr b p sometime after 4000 yr b p sedimentation rates and glacial sediment output began to rise again reaching approximately present levels by 2750 2650 yr b p and have not since returned to low mid holocene levels in detail over the last 3000 yr there is some indication of a slight decrease in sedimentation rate for more than 1000 yr after about 2200 yr b p sedimentation rates and glacial sediment input into all three lakes rose between about 900 and 750 yr b p and have remained very high since if the lake sediments are interpreted as a proxy record of upvalley glacial activity they allow the development of a glacial chronology which is at once generally consistent with and more complete and easily datable than the surficial glacial record

reconstruction of holocene glacier history from distal sources glaciofluvial stream bank mires and a glaciolacustrine sediment core near sota saeter breheimen southern norway this study attempts to reconstruct the holocene glacier history of breheimen southern norway from four stream bank mire sites and a downstream lake sediment core near sota saeter based on lithostr

holocene glacier variations in new zealand a review abstract in the central southern alps of new zealand ice surface lowering has exposed extensive sections of lateral moraines allowing investigation of moraine stratigraphy and genesis the presence of multiple superposed palaeosurfaces within moraine sequences allows recognition of any disturbances displacements or contamination of till layers and interbedded organic material radiocarbon dating of buried wood and soils allows comparison between the holocene glacial history of the eastern ranges and that of the westland region the periodicity of glacier response has been similar to both areas although the precise timing of events has differed due to local climatic and environmental factors in general glaciers in new zealand expanded about 5000 4500 4200 3700 3500 3000 2700 2200 1800 1700 1500 1100 900 700 600 and 400 100 bp