in situ 10be exposure ages from southeastern norway implications for the geometry of the weichselian scandinavian ice sheet abstract as an initial attempt to constrain the geometry and history of the southern part of the scandinavian ice sheet in situ 10 be concentrations in bedrock samples have been measured from four sites in southeastern norway among our results are a number of pre last glacial maximum lgm exposure ages bedrock outcrops in high elevation blockfields typically give surface exposure ages older than 20 10 be ka whereas glacially moulded bedrock surfaces at lower elevations yield surface exposure ages younger than 15 10 be ka these results clearly indicate the preservation of surfaces and landforms predating the lgm most ice sheet models predict a thick ice mass in southeastern norway at the lgm pre lgm 10 be ages either contradict the models supporting geomorphological reconstructions of a thin lgm ice sheet or indicate preservation of previously exposed surfaces beneath cold based ice in the latter case models of 10 be production incorporating regional glacial chronology and periodic burial suggest that the surfaces with the highest 10 be concentrations may have existed for more than one million years

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

paleoglaciation of the tibetan plateau and surrounding mountains based on exposure ages and ela depression estimates the tibetan plateau holds an ample record of past glaciations and there is an extensive set of glacial deposits dated by exposure dating here a compilation is presented of 10be exposure ages from 485 glacial deposits with 1855 individual samples on the tibetan plateau and ela depression estimates for the glacial deposits based on a simple toe to headwall ratio approach to recalculate the tibetan plateau exposure ages 10be production rates from 24 calibration sites across the world are compiled and recalibrated yielding an updated global reference 10be production rate the recalculated exposure ages from the tibetan plateau glacial deposits are then divided into three groups based on exposure age clustering to discriminate good well clustered from poor scattered deglaciation ages a major part of the glacial deposits have exposure ages affected by prior or incomplete exposure complicating exposure age interpretations the well clustered deglaciation ages are primarily from mountain ranges along the margins of the tibetan plateau with a main peak between 10 and 30 ka indicating glacial advances during the global lgm a large number of deglaciation ages older than 30 ka indicates maximum glaciation predating the lgm but the exposure age scatter generally prohibits accurate definition of the glacial chronology the ela depression estimates scatter significantly but the main part is remarkably low average ela depressions of 337 197 m for the lgm and 494 280 m for the pre lgm indicate restricted glacier expansion

chronology of the late weichselian glaciation in the bohemian forest in central europe abstract a glacial chronology based on in situ produced 10 be surface exposure dating of moraines in the bohemian forest central europe was established eleven exposure ages obtained for moraine boulders in the prasilske lake and laka lake valleys czech republic were complemented by 10 be ages from kleiner arbersee germany recalculated according to recently calibrated production rates in the northern hemisphere the glacial phases in the bohemian forest occurred during the last glacial maximum around 24 1 2 5 23 6 2 4 21 8 2 0 and 19 5 2 1 ka following phases of local glaciation occurred during the northern hemisphere deglaciation period around 16 ka and 14 ka the last indicated phase may correlate with older dryas the glacial chronology of the bohemian forest is in agreement with local glaciation chronologies in the giant mts krkonose mts and the eastern alps

a 10be production rate calibration for the arctic we present a baffin bay 10 be production rate calibration derived from glacial deposits in western greenland and baffin island and test our results against published 10 be calibration datasets to develop an arctic 10 be production rate our calibration comprises i 10 be measurements from moraine boulders linked to a 14 c dated moraine at jakobshavn isfjord in western greenland ii an independent and previously published 10 be production rate at jakobshavn isfjord and iii re measured 10 be concentrations from a baffin island calibration site that is included in the north eastern north america dataset combined we calculate a sea level high latitude 10 be production rate for the baffin bay region of 3 96 0 07 atoms g 1 a 1 lal stone scaling model after testing the baffin bay rate against calibration sites in norway and north eastern north america we calculate a more conservative arctic production rate of 3 96 0 15 atoms g 1 a 1 the baffin bay and arctic 10 be production rates are indistinguishable from the north eastern north america 10 be production rate 3 91 0 19 atoms g 1 a 1 and yield overall uncertainties of 2 3 7 1s these production rates reduce systematic uncertainties in 10 be based chronologies of ice margin change and allow 10 be based chronologies to be more confidently compared with high resolution climate records such as those from greenland ice cores copyright 2013 john wiley sons ltd

late quaternary glacial history of the karlik range easternmost tian shan derived from 10be surface exposure and optically stimulated luminescence datings abstract the karlik range located in the easternmost part of the tian shan is a key area in reconstructing paleoclimate in central asia but few studies have been conducted to constrain the timing and extent of quaternary glaciations in its highlands we investigated the late quaternary glacial history in the turgan valley on the northern slopes of the karlik range using cosmogenic 10be surface exposure and optically stimulated luminescence osl dating techniques four major glacial events were dated to 0 79 0 59 ka little ice age lia 15 8 1 6 ka lateglacial 37 4 4 0 44 2 4 3 ka marine oxygen isotope stage mis 3 and 60 2 3 3 79 3 5 2 ka mis 4 or older with a pattern of continuously restricted glaciations after mis 4 this glacial chronology is consistent with the studies from other parts of the tian shan the overall pattern of glaciations across the tian shan suggests that change in precipitation brought by the westerlies was the primary factor influencing the timing and extent of glacial advances during the last glaciation however lower temperature of the karlik range affected by the siberian high may counteract the effect of lower precipitation to drive a relatively extensive glacial advance in the easternmost tian shan

late glacial and holocene 10be production rates for western norway we present a new regional calibration of the 10be production rate from two well dated surfaces insouthern norway a rock avalanche with 14c dated wood and a precisely dated younger dryas moraine c

late glacial 10be ages for glacial landforms in the upper region of the taibai glaciation in the qinling mountain range china abstract glacial landforms are well preserved on taibai mountain 3767 m the main peak of the qinling mountain range located south of the loess plateau and east of the qinghai tibet plateau the timing and extent of quaternary glaciation in the study area is important for reconstructing quaternary environmental change however numerical ages for glaciation in this study area have not previously been well resolved using terrestrial in situ cosmogenic nuclides we dated four samples collected from two glacially eroded rock steps in the upper part of a valley near the main peak in an area previously identified as having been occupied by ice during the taibai glaciation the 10be results are all late glacial in age 18 6 1 1 ka 16 9 1 0 ka 16 9 1 1 ka and 15 1 1 0 ka the spatial pattern of ages in the valley suggests fast retreat with horizontal and vertical retreat rates estimated to be on the order of 0 4 and 0 09 m a 1 respectively a simple extrapolation of these retreat rates from the ages at the two sample sites suggests that the glacier retreat began during last glacial maximum and that glaciers disappeared from the main peak by about 15 ka

investigating absolute chronologies of glacial advances in the nw sector of the cordilleran ice sheet with terrestrial in situ cosmogenic nuclides abstract geologic mapping in yukon territory canada over the past 100 years has revealed a consistent pattern of diminishing cordilleran ice sheet cis extent during successively younger glaciations although this pattern is generally accepted there is still much uncertainty about the number of glaciations their ages and the dynamics of the different lobes that constituted the digitate ice sheet margin their subglacial thermal regimes and ice thicknesses we address uncertainties in the timing of glaciation using cosmogenic nuclide exposure dating at key localities that straddle several major lobes of the cis in west central yukon territory differences in exposure duration within what are thought to be the same map units are perhaps due to inheritance older than expected but more likely result from postglacial shielding younger than expected or surface erosion despite a significant spread in exposure durations on moraines and within map units and tending to rely on longest exposure durations on moraines due to postglacial degradation and shielding our results indicate that the mcconnell glacial advance occurred during marine oxygen isotope stage mis 2 judging from oldest minimum apparent exposure ages of 15 7 1 5 and 17 7 1 6 ka a gladstone glacial advance occurred before 51 8 4 7 ka mis 4 and reid glacial advances before 79 8 7 3 and 82 8 7 5 ka consistent with mis 6 traces of even older glacial advances predate 100 ka 107 5 9 9 154 3 14 2 ka

analyzing complex rock slope deformation at stampa western norway by integrating geomorphology kinematics and numerical modeling abstract the unstable rock slope stampa above the village of flam norway shows signs of both active and postglacial gravitational deformation over an area of 11 km 2 detailed structural field mapping annual differential global navigation satellite system gnss surveys as well as geomorphic analysis of high resolution digital elevation models based on airborne and terrestrial laser scanning indicate that slope deformation is complex and spatially variable numerical modeling was used to investigate the influence of former rockslide activity and to better understand the failure mechanism field observations kinematic analysis and numerical modeling indicate a strong structural control of the unstable area based on the integration of the above analyses we propose that the failure mechanism is dominated by 1 a toppling component 2 subsiding bilinear wedge failure and 3 planar sliding along the foliation at the toe of the unstable slope using differential gnss 18 points were measured annually over a period of up to 6 years two of these points have an average yearly movement of around 10 mm year they are located at the frontal cliff on almost completely detached blocks with volumes smaller than 300 000 m 3 large fractures indicate deep seated gravitational deformation of volumes reaching several 100 million m 3 but the movement rates in these areas are below 2 mm year two different lobes of prehistoric rock slope failures were dated with terrestrial cosmogenic nuclides while the northern lobe gave an average age of 4 300 years bp the southern one resulted in two different ages 2 400 and 12 000 years bp which represent most likely multiple rockfall events this reflects the currently observable deformation style with unstable blocks in the northern part in between joasete and furekamben and no distinct blocks but a high rockfall activity around ramnanosi in the south with a relative susceptibility analysis it is concluded that small collapses of blocks along the frontal cliff will be more frequent larger collapses of free standing blocks along the cliff with volumes 100 000 m 3 thus large enough to reach the fjord cannot be ruled out a larger collapse involving several million m 3 is presently considered of very low likelihood

glacial and vegetation history of the polar ural mountains in northern russia during the last ice age marine isotope stages 5 2 abstract we describe and discuss the glacial and climate variations in the polar ural mountains in northern russia over the last 100 000 years a series of optically stimulated luminescence osl and radiocarbon ages from sediment cores demonstrate that there has been continuous deposition of lacustrine sediments throughout the last 65 ka in lake gerdizty a lake basin situated on the eastern foothills of the urals below the lacustrine sequence are two till beds the uppermost unit b was probably deposited by a large mountain centred glacier complex that covered the lake basin during marine isotope stage mis 4 this till bed might be a counterpart of the usa moraine in the western foothills of the polar urals which is dated with osl and 10 be cosmogenic nuclide methods to between 68 and 58 ka consistent with the osl ages from the lowermost lacustrine sediments in lake gerdizty during this glaciation some of the northern uralian outlet glaciers probably merged with the adjacent barents kara ice sheet that reached onto the adjacent lowlands forming large ice dammed lakes on both sides of the ural mountains the equilibrium line altitude ela on the local ice cap was then at least 1200 m lower than at present the pollen stratigraphy in lake gerditzy reflects an open tundra and steppe like vegetation throughout mis 3 2 60 11 7 ka the first significant change in vegetation shown by an increase of dwarf shrub communities of salix and betula took place during the lateglacial at around 15 ka or shortly after birch and spruce trees approached the area for the first time soon after the holocene transition 11 7 ka and became dominant elements in the vegetation after a few hundred years our reconstruction suggests a very cold summer climate during mis 4 and presumably also during the preceding mis 5b 95 85 ka glaciation probably amplified by the large ice dammed lakes that existed during these two glaciations a somewhat milder climate prevailed during mis 3 60 25 ka but a treeless vegetation nevertheless suggests that mean summer temperatures did not exceed 10 12 c before the earliest holocene

timing of terminal pleistocene deglaciation at high elevations in southern and central british columbia constrained by 10be exposure dating abstract the cordilleran ice sheet cis covered most of british columbia and southern yukon territory at the local last glacial maximum llgm during marine oxygen isotope stage 2 however its subsequent demise is not well understood particularly at high elevations east of its ocean terminating margin we present 10be exposure ages from two high elevation sites in southern and central british columbia that help constrain the time of initial deglaciation at these sites we sampled granodiorite erratics at elevations of 2126 2230 m a s l in the marble range and 1608 1785 m a s l in the telkwa range at the western margin of the interior plateau the erratics at both sites are near ice marginal meltwater channels that delineate the local ice surface slope and thus the configuration of the ice sheet during deglaciation the locations of the erratics and their relations to meltwater channels ensure that the resulting 10be ages date cis deglaciation and not the retreat of local montane glaciers our sample sites emerged above the surface of the cis as its divide migrated westward from the interior plateau to the axis of the coast mountains two of the four samples from the summit area of the marble range yielded apparent exposure ages of 14 0 0 7 and 15 2 0 8 ka these ages are 1 8 3 0 ka younger than the well established llgm age of ca 17 ka for the puget lobe of the cis in washington state they are 1 7 ka younger than the llgm age for the puget lobe if a snow shielding correction to their uncertainty weighted mean age is applied the other two samples yielded much older apparent exposure ages 20 6 1 4 and 33 0 1 5 ka indicating the presence of inherited isotopes four samples collected from the summit area of the telkwa range in the hazelton mountains yielded well clustered apparent exposure ages of 10 1 0 6 10 2 0 7 10 4 0 5 and 11 5 1 1 ka significant present day snow cover introduces a large uncertainty in the apparent exposure ages from this site a snow shielding correction based on present day snow cover data increases the uncertainty weighted mean exposure age of the telkwa range erratics to 12 4 0 7 ka consistent with deglacial 14c ages from areas near sea level to the west our exposure ages show a thinning of the southern portion of the cis shortly after the llgm and persistence of a remnant mountain ice cap in the central coast mountains into the younger dryas chronozone our data also show that the summit area of the marble range was ice covered during the llgm the presence of an ice body of considerable dimension in north central british columbia until or possibly even after the younger dryas highlights the need for geomorphological and geochronological studies of the ice dispersal centre over the skeena mountains in northwest british columbia and the need for better understanding of the response of the cis to lateglacial climate fluctuations

glacier advances in northeastern turkey before and during the global last glacial maximum abstract our study in the basyayla valley in northeastern anatolia showed evidence of four glacier advances that built terminal and lateral moraines surface exposure dating of boulders on these moraines showed that the maximum ice extent mie was asynchronous with the global last glacial maximum lgm 22 1 4 3 thousand years ka the local mie took place at least 57 0 3 5 ka ago the extent of the basyayla glacier during this advance is not known exactly because the boulders are only preserved on a lateral moraine the next advance was prior to 41 5 2 5 ka and it descended down the valley to approximately 2320 m above sea level m a s l with a glacier length of 5 3 km during the early global lgm the basyayla glacier extended for a distance of 4 9 km down to approx 2430 m a s l the last recorded advance occurred during the global lgm this extension was 0 7 km smaller than the local mie and its terminus reached 2490 m a s l only the exposure ages of boulders in a retreat position at an altitude of approx 3045 m a s l indicate that the valley has remained ice free since the lateglacial period therefore the lateglacial extent was limited to the cirque system in the uppermost part of the catchment furthermore holocene glacier oscillations seem to be either absent or restricted to solifluction in the whole catchment and to rock glacier movements in the southern tributary of the basyayla valley system

an arctic perspective on dating mid late pleistocene environmental history to better understand pleistocene climatic changes in the arctic integrated palaeoenvironmental and palaeoclimatic signals from a variety of marine and terrestrial geological records as well as geochronologic age control are required not least for correlation to extra arctic records in this paper we discuss from an arctic perspective methods and correlation tools that are commonly used to date arctic pleistocene marine and terrestrial events we review the state of the art of arctic geochronology with focus on factors that affect the possibility and quality of dating and support this overview by examples of application of modern dating methods to arctic terrestrial and marine sequences event stratigraphy and numerical ages are important tools used in the arctic to correlate fragmented terrestrial records and to establish regional stratigraphic schemes age control is commonly provided by radiocarbon luminescence or cosmogenic exposure ages arctic ocean deep sea sediment successions can be correlated over large distances based on geochemical and physical property proxies for sediment composition patterns in palaeomagnetic records and increasingly biostratigraphic data many of these proxies reveal cyclical patterns that provide a basis for astronomical tuning recent advances in dating technology calibration and age modelling allow for measuring smaller quantities of material and to more precisely date previously undatable material i e foraminifera for c 14 and single grain luminescence however for much of the pleistocene there are still limits to the resolution of most dating methods consequently improving the accuracy and precision analytical and geological uncertainty of dating methods through technological advances and better understanding of processes are important tasks for the future another challenge is to better integrate marine and terrestrial records which could be aided by targeting continental shelf and lake records exploring proxies that occur in both settings and by creating joint research networks that promote collaboration between marine and terrestrial geologists and modellers

timing and climatic drivers for glaciation across semi arid western himalayan tibetan orogen abstract mapping and forty seven new 10 be ages help define the timing of glaciation in the ladakh and pangong ranges in northwest india five new local glacial stages are defined for the ladakh range from oldest to youngest these include the ladakh 4 glacial stage at 81 20 ka the ladakh 3 glacial stage not dated the ladakh 2 glacial stage at 22 3 ka the ladakh 1 glacial stage not dated and the ladakh cirque glacial stage at 1 8 0 4 ka three local glacial stages are defined for the pangong range which include the pangong 2 glacial stage at 85 15 ka the pangong 1 glacial stage at 40 3 ka and the pangong cirque glacial stage at 0 4 0 3 ka the new 10 be ages are combined with 645 recalculated 10 be ages from previous studies to develop the first regional framework of glaciation across the dryland regions of the greater himalaya transhimalaya pamir and tian shan at the western end of the himalayan tibetan orogen nineteen regional glacial stages are recognized that are termed semi arid western himalayan tibetan stages swhts these include swhts 9 at 311 32 ka swhts 7 at 234 44 ka tentative swhts 6 at 146 18 ka swhts 5e at 121 11 ka swhts 5a at 80 5 ka swhts 5a at 72 8 ka swhts 4 at 61 5 ka swhts 3 at 46 4 ka swhts 2f at 30 3 ka swhts 2e at 20 2 ka swhts 2d at 16 9 0 7 ka swhts 2c at 14 9 0 8 ka swhts 2b at 13 9 0 5 ka swhts 2a at 12 2 0 8 ka swhts 1e at 8 8 0 3 ka tentative swhts 1d at 6 9 0 2 ka tentative swhts 1c at 3 8 0 6 ka swhts 1b at 1 7 0 2 ka and swhts 1a at 0 4 0 1 ka regional glacial stages older than 21 ka are broadly correlated with strong monsoons swhts that are 21 ka or younger have smaller uncertainties and broadly correlate with global ice volume given by marine oxygen isotope stages and northern hemisphere climatic events oldest dryas older dryas younger dryas roman humid period and little ice age

the deep accumulation of 10be at utsira southwestern norway implications for cosmogenic nuclide exposure dating in peripheral ice sheet landscapes cosmogenic nuclide exposure dating is a widely used method for constraining past ice sheet histories we scrutinize a recently published data set of cosmogenic 10be data from erratic boulders in norway used to constrain the deglaciation of the western scandinavian ice sheet to 20 ka our model of the 10be inventory in glacial surfaces leads us to conclude that the chronology may be afflicted by the deep subsurface accumulation of 10be during long lasting ice free periods that resulted in 10be ages 10 too old we suggest that the majority of the dated erratic boulders contain a uniform level of inherited muon produced 10be and were derived from bedrock depths 2 5 m and most likely 4 m the implication of our finding is that for landscapes that experience long ice free periods between brief maximum glacial phases glacial erosion of 5 m is required to remove detectable traces of inherited 10be

cosmogenic 26al 10be surface production ratio in greenland the assumed value for the cosmogenic 26al 10be surface production rate ratio in quartz is an important parameter for studies investigating the burial or subaerial erosion of long lived surfaces and sediments recent models and data suggest that the production ratio is spatially variable and may be greater than originally thought here we present measured 26al 10be ratios for 24 continuously exposed bedrock and boulder surfaces spanning 61 77 n in greenland empirical measurements such as ours include nuclides produced predominately by neutron induced spallation with percent level contributions by muon interactions the slope of a york regression line fit to our data is 7 3 0 3 1 suggesting that the 26al 10be surface production ratio exceeds the commonly used value of 6 75 at least in the arctic a higher 26al 10be production ratio has implications for multi nuclide cosmogenic isotope studies because it results in greater modeled burial durations and erosion rates

subglacial abrasion rates at goldbergkees hohe tauern austria determined from cosmogenic 10be and 36cl concentrations we report concentrations of cosmogenic 10be and 36cl used to determine erosion depths in the recently deglaciated bedrock at goldbergkees in the eastern alps the glacier covered the sampling sites during the little ice age lia until ca 1940 the youngest ages calculated from these concentrations match the known exposure time after the known post lia exposure of 100 years the apparent age no cover no erosion of most samples however is significantly older we show that the measured nuclide concentrations represent subglacial erosion depths rather than exposure times in particular erosion depths calculated using 10be and 36cl concentrations of individual samples match well whereas apparent 36cl ages are consistently older than 10be ages the bedrock at the youngest surfaces was deeply eroded 297 cm by the goldbergkees during the late holocene in contrast bedrock at the margin of the lia ice extent was eroded 35 cm these values convert to subglacial erosion rates on the order of 0 1 mm a to 5 mm a while modeled erosion rates depend on the duration of glacial cover and erosion intrinsic to the different exposure scenarios used for calculation 700 3300 years modeled total erosion depths are insensitive 5 20 change this article is protected by copyright all rights reserved analysis of erosion depths on the transverse valley profile shows a general trend of greatest erosion part way up the valley side and less erosion under thin ice at the lateral margin a second profile along the valley axis indicates depth of erosion is greatest where the ice abuts the foot of the investigated bedrock riegel and at its lee side just beyond the crest this article is protected by copyright all rights reserved

shock induced devolatilization and isotopic fractionation of h and c from murchison meteorite some implications for planetary accretion incipient shock induced devolatilization of murchison meteorite occurs upon subjecting samples to a minimum shock stress or pressure of about 5 gpa this pressure is similar to that required to initiate devolatilization of 20 porous serpentine upon low velocity impact 61 5 km s the solid shocked products were combusted and isotopic analysis of the resulting h 2o and co 2 was performed h and 13 c are partitioned preferentially over d and 12 c respectively into the released gas suggesting that the inorganic mineral portion of murchison is devolatilized preferentially over the organic kerogen fraction which is relatively enriched in d and 12 c at the shock pressures studied these results are combined with previous results on serpentine devolatilization to derive an empirical h fractionation versus devolatilization relation that is used to evaluate the extent of impact induced isotopic fractionation during planetary accretion during accretion of the earth impact induced devolatilization and formation of the early primitive atmosphere would have begun at a point where the growing earth achieved a radius in the 480 800 km range the present experimental results suggest that the earth s early atmosphere would have been enriched in hydrogen relative to d compared to the residual solid with a fractionation factor of 18 to 23 assuming that current planetary atmospheres have resulted from degassing of planetary interiors after loss of the earliest h enriched atmosphere the above degree of isotopic fractionation is not sufficient by itself to explain the large positive d values of the present martian and venusian atmospheres however this mechanism in conjunction with tectonic recycling over geologic time could contribute to preferential h loss for earth and mars

cosmogenic nuclide exposure ages along a vertical transect in western norway implications for the height of the fennoscandian ice sheet 10 be and 26 al exposure ages for bedrock samples from a vertical transect at skala in western norway provide new constraints on the history of the fennoscandian ice sheet the weathered bedrock surface autochthonous block field mantling the summit of skala has an exposure age of 55 ka suggesting that this surface formed before the last glacial maximum 18 14 c ka or 21 calendar ka the block field is truncated by a glacial trimline at 1660 m above sea level glaciated bedrock below the trimline has an exposure age of 26 21 ka the range depends on assumptions about erosion rate ice therefore receded from this altitude at about the time of the last glacial maximum the 10 be age for bedrock immediately below a second lower trimline at skala suggests a glacial advance or stillstand at 18 13 ka consistent with previously documented readvances or stillstands at the western and southern margins of the ice sheet

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

the deglaciation history of the simplon region southern swiss alps constrained by 10be exposure dating of ice molded bedrock surfaces the deglaciation history of the swiss alps after the last glacial maximum involved the decay of several ice domes and the subsequent disintegration of valley glaciers at high altitude here we use bedrock exposure dating to reconstruct the temporal and spatial pattern of ice retreat at the simplon pass altitude 2000 m located 40 km southwest of the rhone ice dome eleven 10be exposure ages from glacially polished quartz veins and ice molded bedrock surfaces cluster tightly between 13 5 0 6 ka and 15 4 0 6 ka internal errors indicating that the simplon pass depression became ice free at 14 1 0 4 ka external error of mean age this age constraint is interpreted to record the melting of the high valley glaciers in the simplon pass region during the warm bolling allerod interstadial shortly after the oldest dryas stadial two bedrock samples collected a few hundred meters above the pass depression yield older 10be ages of 17 8 0 6 ka and 18 0 0 6 ka these ages likely reflect the initial downwasting of the rhone ice dome and the termination of the ice transfluence from the ice dome across the simplon pass toward the southern foreland there the retreat of the piedmont glacier in val d ossola was roughly synchronous with the decay of the rhone ice dome in the interior of the mountain belt as shown by 10be ages of 17 7 0 9 ka and 16 1 0 6 ka for a whaleback at 500 m elevation near montecrestese in northern italy in combination with well dated paleoclimate records derived from lake sediments our new age data suggest that during the deglaciation of the european alps the decay of ice domes was approximately synchronous with the retreat of piedmont glaciers in the foreland and was followed by the melting of high altitude valley glaciers after the transition from the oldest dryas to the bolling allerod when mean annual temperatures rose rapidly by 3 c

cosmogenic exposure age constraints on deglaciation and flow behaviour of a marine based ice stream in western scotland 21 16 ka understanding how marine based ice streams operated during episodes of deglaciation requires geochronological data that constrain both timing of deglaciation and changes in their flow behaviour such as that from unconstrained ice streaming to topographically restricted flow we present seventeen new 10be exposure ages from glacial boulders and bedrock at sites in western scotland within the area drained by the hebrides ice stream a marine based ice stream that drained a large proportion of the former british irish ice sheet exposure ages from tiree constrain deglaciation of a topographic high within the central zone of the ice stream from which convergent flowsets were produced during ice streaming these ages thus constrain thinning of the hebrides ice stream which on the basis of supporting information we infer to represent cessation of ice streaming at 20 6 1 2 ka 3 4 ka earlier than previously inferred a period of more topographically restricted flow produced flow indicators superimposed on those relating to full ice stream conditions and exposure ages from up stream of these constrain deglaciation to 17 5 1 0 ka complete deglaciation of the marine sector of the hebrides ice stream occurred by 17 16 ka at which time the ice margin was located near the present coastline exposure ages from the southernmost outer hebrides mingulay and barra indicate deglaciation at 18 9 1 0 and 17 1 1 0 ka respectively demonstrating that an independent ice cap persisted on the southern outer hebrides for 3 4 ka after initial ice stream deglaciation this suggests that deglaciation of the hebrides ice stream was focused along major submarine troughs collectively our data constrain initial deglaciation and changes in flow regime of the hebrides ice stream final deglaciation of its marine sector and deglaciation of the southern portion of the independent outer hebrides ice cap providing chronological constraints on future numerical reconstructions of this key sector of the former british irish ice sheet

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

a geochronologic framework for the ziegler reservoir fossil site snowmass village colorado abstract the ziegler reservoir fossil site near snowmass village colorado usa provides a unique opportunity to reconstruct high altitude paleoenvironmental conditions in the rocky mountains during the last interglacial period we used four different techniques to establish a chronological framework for the site radiocarbon dating of lake organics bone collagen and shell carbonate and in situ cosmogenic 10 be and 26 al ages on a boulder on the crest of a moraine that impounded the lake suggest that the ages of the sediments that hosted the fossils are between 140 ka and 45 ka uranium series ages of vertebrate remains generally fall within these bounds but extremely low uranium concentrations and evidence of open system behavior limit their utility optically stimulated luminescence osl ages n 18 obtained from fine grained quartz maintain stratigraphic order were replicable and provide reliable ages for the lake sediments analysis of the equivalent dose d e dispersion of the osl samples showed that the sediments were fully bleached prior to deposition and low scatter suggests that eolian processes were likely the dominant transport mechanism for fine grained sediments into the lake the resulting ages show that the fossil bearing sediments span the latest part of marine oxygen isotope stage mis 6 all of mis 5 and mis 4 and the earliest part of mis 3

minor inheritance inhibits the calibration of the 10be production rate from the ad 1717 val ferret rock avalanche european alps to calibrate the in situ 10be production rate we collected surface samples from nine large granitic boulders within the deposits of a rock avalanche that occurred in ad 1717 in the upper ferret valley mont blanc massif italy the 10be concentrations were extremely low and successfully measured within 10 analytical uncertainty or less the concentrations vary from 4829 448 to 5917 476 at g 1 using the historical age exposure time we calculated the local and sea level high latitude i e 60 cosmogenic 10be spallogenic production rates depending on the scaling schemes these vary between 4 60 0 38 and 5 26 0 43 at g 1 a 1 although they correlate well with global values our production rates are clearly higher than those from more recent calibration sites we conclude that our 10be production rate is a mean and an upper bound for production rates in the massif region over the past 300 years this rate is probably influenced by inheritance and will yield inaccurate e g too young exposure ages when applied to surface exposure studies in the area other independently dated rock avalanche deposits in the region that are approximately 103 years old could be considered as possible calibration sites

quaternary evolution of a large alluvial fan in a periglacial setting crau plain se france constrained by terrestrial cosmogenic nuclide 10be abstract located in the foreland of the western alps the crau plain was the outlet of the durance river in the pleistocene in order to constrain its geodynamic evolution in terms of chronology and denudation rates the two main quaternary deposits of this plain have been studied based on cosmogenic nuclide 10 be concentration measurements along depth profiles the abandonment of the miramas and luquier alluvial surfaces occurred at the beginning of glacial periods wurm isotopic stage 4 and riss isotopic stage 6 respectively discrepancy in denudation rates under similar geomorphological and lithological conditions suggests different denudation processes during glacial and interglacial periods the denudation rate has been estimated at about 25 mm ka 1 for the interglacial period and about 60 mm ka 1 for the glacial period the abandonment of the crau plain as the outlet of the durance river occurred sometime between 75 and 35 ka

geomorphological evidence and 10be exposure ages for the last glacial maximum and deglaciation of the velka and mala studena dolina valleys in the high tatra mountains central europe abstract 10be exposure age chronology of the last glaciation was established in a key area at the southern slopes of the high tatra mts western carpathians in situ produced 10be in moraine boulders glacially transformed bedrock surfaces and rockfall accumulations constrains the timing of the last glacial maximum lgm glacier expansion and provides chronological evidence for the post lgm decay of one of the largest paleoglaciers in the range the uncertainty weighted mean age of 22 0 0 8 ka obtained for the terminal moraine in the forefield of the velka studena dolina valley indicates that the oldest moraine was deposited close to the global lgm this finding confirms that well preserved moraines in the range were formed during the last glacial cycle and that glaciation on the southern flank of the range was more extensive than earlier in the last glacial cycle the maximum glacier extent correlates with late wurmian weichselian glacier phases in the alps the bavarian bohemian forest and the krkonose mts but probably postdates the period of maximum glaciation in the southern carpathians re advance moraines at the mouth of the velka studena dolina valley and in the middle part of the mala studena dolina valley were deposited no later than around 20 5 ka and 15 5 ka respectively the timing of these advances is broadly synchronous within the high tatra mts as well as with glacier advances in the alps bavarian bohemian forest and krkonose mts 10be exposure ages obtained from glacially transformed bedrock surfaces range between 20 5 1 7 ka and 10 7 0 3 ka constraining the onset and the final phase of the deglaciation surface exposure dating of four rockfall accumulations produced uncertainty weighted mean ages of 20 2 1 2 ka 17 0 0 7 ka 16 5 0 4 ka and 15 6 0 7 ka these ages indicate that activation of rock slope failures occurred under paraglacial conditions within a few centuries up to 1400 years after the formation of re advance moraines

glacier extent during the younger dryas and 8 2 ka event on baffin island arctic canada greenland ice cores reveal that mean annual temperatures during the younger dryas yd cold interval about 12 9 to 11 7 thousand years ago ka and the 150 year long cold reversal that occurred 8 2 thousand years ago were 15 and 3 to 4 c colder than today respectively reconstructing ice sheet response to these climate perturbations can help evaluate ice sheet sensitivity to climate change here we report the widespread advance of laurentide ice sheet outlet glaciers and independent mountain glaciers on baffin island arctic canada in response to the 8 2 ka event and show that mountain glaciers during the 8 2 ka event were larger than their yd predecessors in contrast to the wintertime bias of yd cooling we suggest that cooling during the 8 2 ka event was more evenly distributed across the seasons

a calendar age estimate of a very late younger dryas ice sheet maximum in western norway abstract we have established an accurate chronology in calendar years for the maximum phase of the younger dryas yd scandinavian ice sheet in western norway glaciomarine silt confidentially identified in shallow marine basins located was 1 2 km distal to a yd ice marginal delta due to the topography of this area the silt monitors faithfully the period when the ice sheet reached and remained at its maximum position in these basins the deposition of silt commenced 6 10 cm above the vedde ash bed ca 10 300 14 c yr bp or ca 12 000 cal yr bp according to calculated sedimentation rates of the deposits the deposition of silt started and thus the ice sheet reached its maximum 300 400 years after the vedde ash fall around 11 600 11 700 cal yr bp the ice sheet receded from its maximum position simultaneously with the increase of betula birch pollen at the yd holocene boundary ca 11 500 cal yr bp the duration of the yd glacial maximum of the scandinavian ice sheet in western norway was only about 100 200 years and is constrained within the 14 c plateau at 10 000 14 c yr bp the yd glacial maximum occurred extremely late in western norway later than elsewhere in scandinavia the result also demonstrates different response times for different glaciers small cirque glaciers farther north in western norway expanded to their maximum position very early in the yd whereas the ice cap at alfotbreen reached its maximum later but still before the vedde ash fall the ice sheet reached its maximum well after the vedde ash fall and only 100 200 years before the yd holocene boundary

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

revised deglaciation history of the pietrele stânisoara glacial complex retezat mts southern carpathians romania abstract although geomorphological evidences of quaternary glaciations of the southern carpathians were extensively studied and discussed the limited number of chronological studies resulted in poor and controversial knowledge on the age of glaciations and deglaciation of the area we use new and recalculated in situ produced 10be surface exposure ages of glacial landforms to shed light on the age of the maximum glacial extent and the glacier oscillations during the last deglaciation process on the northern side of the retezat mountains according to our data the maximum ice extent documented by preserved moraines occurred around 21 0 1 5 0 8 ka coincident with the global last glacial maximum lgm the deglaciation process during the lateglacial was characterized by two glacial advances at 18 6 0 8 0 9 and 16 3 0 6 0 6 ka inferred stabilization date of the penultimate glacial stage at 15 2 0 8 0 7 ka was closely followed by the abrupt warming at the onset of the bolling allerod documented by a local chironomid based temperature reconstruction the last small glacier advance was dated to 13 5 0 4 0 5 ka these recessional readvance phases agree with other european glacial chronologies

cosmogenic 10be production rate calibrated against 3he in the high tropical andes 3800 4900 m 20 22 s abstract many geomorphologic applications notably glacier chronologies require improvements in both the precision and the accuracy of the cosmogenic dating tool of particular importance is the need to better constrain the spatial variability of the cosmogenic nuclides production rates at high elevation and low latitudes one strategy that can be adopted for this is to couple absolute calibrations from independently dated surfaces with cross calibration studies performed by measuring several cosmogenic nuclides in the same rock in the present study we report the highest elevation 4800 m cross calibration published to date comprising measurements of cosmogenic 3 he and 10 be in cogenetic pyroxene and quartz the samples were collected from six dacitic moraine boulders exposed from 32 to 65 ka at 4820 m on the flanks of the uturuncu volcano 22 s 67 w southern lipez bolivia the samples yield a remarkably tight cluster of 3 he 10 be production ratios with a weighted mean of 33 3 0 9 1 this production ratio is undistinguishable within uncertainties from the 3 he 10 be production ratio of 32 3 0 9 determined in the same mineral pair at low elevation 1333 m by amidon et al 2009 these results agree at the 1 level and suggest that any hypothetical increase of the 3 he 10 be production ratio in pyroxene and quartz is likely to be lower than 5 over this elevation range 1000 5000 m moreover the production ratio is almost insensitive to the li content of the pyroxene 20 to 50 ppm li suggesting that the cosmogenic thermal neutron production of 3 he is very low in this setting the high elevation 3 he 10 be production ratio is used in combination with a local determination of the 3 he production rate in the high central altiplano 3800 m blard et al 2013 to establish a local 10 be production rate of 30 0 1 4 at g 1 yr 1 at 3800 m and 20 s after scaling to sea level high latitude with the time dependent lal stone model this yields a 10 be production rate in quartz of 3 63 0 17 at g 1 yr 1 importantly this rate can be used for high precision geomorphologic dating for example for determining glacial chronologies 1 4 through 10 be dating of moraines in the high tropical andes any inaccuracy attached to the scaling model is canceled out when the calibration site is located close to the dated object the same experiment was also undertaken in pyroxene and plagioclase from two andesitic boulders from the tunupa volcano moraines exposed at 3800 m and 4200 m a 3 he 10 be production ratio of 35 9 1 3 1 is obtained for this mineral pair indicating that the 10 be production rate in plagioclase is about 8 lower than in quartz

a 10be chronology of south western scandinavian ice sheet history during the lateglacial period we present 34 new cosmogenic 10be exposure ages that constrain the lateglacial bolling preboreal history of the scandinavian ice sheet in the lysefjorden region south western norway we find that the classical lysefjorden moraines earlier thought to be entirely of younger dryas age encompass three adjacent moraines attributed to at least two ice sheet advances of distinctly different ages the 10be age of the outermost moraine 14 0 0 6 ka n 4 suggests that the first advance is of older dryas age the innermost moraine is at least 2000 years younger and was deposited near the end of the younger dryas 11 4 0 4 ka n 7 after abandonment of the innermost lysefjorden moraine the ice front receded quickly towards the head of the fjord where recession was interrupted by an advance that deposited the trollgaren moraine at 11 3 0 9 ka n 5 10be ages from the inboard side of the trollgaren moraine suggest final retreat by 10 7 0 3 ka n 7 the late culmination of the younger dryas advance contrasts with other sectors of the scandinavian ice sheet where the margin appears to have culminated earlier during the younger dryas stadial followed by retreat during the middle and late part of the younger dryas

late glacial mountain glacier culmination in arctic norway prior to the younger dryas abstract climate changes during the late glacial period lg 15 11 ka as recorded in greenland and antarctic ice cores show a bipolar pattern between 14 5 ka and 13 ka ago the northern latitudes experienced the bolling allerod ba warm period while southern records feature the antarctic cold reversal acr between 12 9 ka and 11 7 ka ago the north was under the younger dryas yd cold spell while southern latitude temperature rose in parallel to atmospheric co2 concentrations while the southern hemisphere pattern is well documented in mountain glacier moraine records from new zealand and patagonia in northern mid latitudes and the arctic the lg glacier culmination has been connected to the yd stadial apparently confirming the bipolar pattern we present a geomorphic map of mountain glaciers in arctic norway a cosmogenic nuclide chronology from 71 moraine boulders from the lg and the holocene and first order glacier modeling experiments the model and dating results show that the studied mountain glaciers are most sensitive to summer temperature change that their response to those changes is highly correlated to a wider region and that these mountain glaciers in arctic norway reached their maximum lg extent about 14 ka ago prior to the yd following considerable retreat through the first part of the yd glaciers re stabilized in the mid yd and showed slower oscillatory retreat through the latter part of the yd we compare this glacier pattern to updated earlier glacier records in the wider arctic and north atlantic region and propose a pattern of coherent glacier response to climate changes during this interval the lg results from arctic glaciers show consistency to the glacier record from new zealand and patagonia this first order interhemispheric coherency of lg mountain glacier fluctuations driven mainly by summer temperature would support the view that the bipolar seesaw was primarily a northern winter phenomenon during the lg period and the yd in particular more similar experiments need to be performed to further test this scenario

deglaciation of fennoscandia abstract to provide a new reconstruction of the deglaciation of the fennoscandian ice sheet in the form of calendar year time slices which are particularly useful for ice sheet modelling we have compiled and synthesized published geomorphological data for eskers ice marginal formations lineations marginal meltwater channels striae ice dammed lakes and geochronological data from radiocarbon varve optically stimulated luminescence and cosmogenic nuclide dating this is summarized as a deglaciation map of the fennoscandian ice sheet with isochrons marking every 1000 years between 22 and 13 cal kyr bp and every hundred years between 11 6 and final ice decay after 9 7 cal kyr bp deglaciation patterns vary across the fennoscandian ice sheet domain reflecting differences in climatic and geomorphic settings as well as ice sheet basal thermal conditions and terrestrial versus marine margins for example the ice sheet margin in the high precipitation coastal setting of the western sector responded sensitively to climatic variations leaving a detailed record of prominent moraines and other ice marginal deposits in many fjords and coastal valleys retreat rates across the southern sector differed between slow retreat of the terrestrial margin in western and southern sweden and rapid retreat of the calving ice margin in the baltic basin our reconstruction is consistent with much of the published research however the synthesis of a large amount of existing and new data support refined reconstructions in some areas for example the lgm extent of the ice sheet in northwestern russia was located far east and it occurred at a later time than the rest of the ice sheet at around 17 15 cal kyr bp we also propose a slightly different chronology of moraine formation over southern sweden based on improved correlations of moraine segments using new lidar data and tying the timing of moraine formation to greenland ice core cold stages retreat rates vary by as much as an order of magnitude in different sectors of the ice sheet with the lowest rates on the high elevation and maritime norwegian margin retreat rates compared to the climatic information provided by the greenland ice core record show a general correspondence between retreat rate and climatic forcing although a close match between retreat rate and climate is unlikely because of other controls such as topography and marine versus terrestrial margins overall the time slice reconstructions of fennoscandian ice sheet deglaciation from 22 to 9 7 cal kyr bp provide an important dataset for understanding the contexts that underpin spatial and temporal patterns in retreat of the fennoscandian ice sheet and are an important resource for testing and refining ice sheet models

dating the source of lower crystal reflectivity using birps deep seismic profiles across the lapetus suture abstract six birps deep seismic reflection profiles around the british isles that cross the trend of the lapetus suture allow a geophysical definition of the suture zone for 900 km along its strike and demonstrate that specific reflective structures have survived since the mid palaeozoic caledonian orogen in an area northeast of england spanning 70 km along caledonian strike and 200 km across strike three profiles show very considerable similarities in the reflectivity patterns of the lower crust when these similarities are mapped the boundaries separating regions of lower crust with the same reflective character run parallel to caledonian strike this strongly suggests that the distribution of reflectivity in the lower crust in this area is directly controlled by caledonian structures geologic models for the area imply that many of the reflectors themselves may also be of caledonian age however though an age for the imposition of patterns of reflectivity can be inferred the age of an individual reflector cannot be determined unless it can be traced to outcrop or unless there is independent evidence as to the physical nature of the reflector

lake store finnsjoen a key for understanding lateglacial early holocene vegetation and ice sheet dynamics in the central scandes mountains the lateglacial lg deglaciation and vegetation development in the scandes mountains has been debated for a century here we present new evidence from microfossils radiocarbon dated plant macrofossils and sedimentary ancient dna from laminated sediments in lake store finnsjoen 1260 m a s l at dovre central norway combined with previous results from three other dovre lakes this allows for new interpretations of events during and immediately after the lg deglaciation the finnsjoen sediments present the first uninterrupted record of local vegetation development in the scandes mountains from the late younger dryas yd ca 12 000 cal years bp to the early holocene around 9700 cal years bp the local vegetation in late yd early holocene was extremely sparse with pioneer herbs e g artemisia norvegica beckwithia campanula cf uniflora koenigia oxyria papaver saxifraga spp and dwarf shrubs betula nana salix including salix polaris from 11 300 cal years bp local vegetation rapidly closed with dominant dryas saxifraga spp and silene acaulis from ca 10 700 cal years bp open birch forests with juniper empetrum nigrum and other dwarf shrubs developed pine forests established within the area from 10 300 cal years bp we identified the cold preboreal oscillation pbo not earlier described from pollen data in south norway around 11 400 cal years bp by a regional pollen signal distinct local vegetation changes were not detected until the post pbo warming around 11 300 cal years bp apparently the earlier warming at the yd holocene transition at 11 650 cal years bp was too weak and short lived for vegetation closure at high altitudes at dovre for the first time we demonstrate a regional glacier readvance and local ice cap formations during the yd in the scandes mountains in two of the deep lakes with small catchments yd glaciation blocked sedimentation without removing old sediments and caused a hiatus separating sediments of the ice free lg interstadial lgi from those of the ice free holocene period both regional glaciers and local ice caps caused hiati ice free pre yd conditions at dovre followed by a yd readvance point to a scenario that is intermediate between the maximum ice model postulating a thick glacier during the entire lg and the minimum ice model postulating thin and multi domed early lg ice

landscape preservation under fennoscandian ice sheets determined from in situ produced 10be and 26al some areas within ice sheet boundaries retain pre existing landforms and thus either remained as ice free islands nunataks during glaciation or were preserved under ice differentiating between these alternatives has significant implications for paleoenvironment ice sheet surface elevation and ice volume reconstructions in the northern swedish mountains in situ cosmogenic 10be and 26al concentrations from glacial erratics on relict surfaces as well as glacially eroded bedrock adjacent to these surfaces provide consistent last deglaciation exposure ages 8 13 kyr confirming ice sheet overriding as opposed to ice free conditions however these ages contrast with exposure ages of 34 61 kyr on bedrock surfaces in these same relict areas demonstrating that relict areas were preserved with little erosion through multiple glacial cycles based on the difference in radioactive decay between 26al and 10be the measured nuclide concentration in one of these bedrock surfaces suggests that it remained largely unmodified for a minimum period of 845 418 461 kyr these results indicate that relict areas need to be accounted for as frozen bed patches in basal boundary conditions for ice sheet models and in landscape development models subglacial preservation also implies that source areas for glacial sediments in ocean cores are considerably smaller than the total area covered by ice sheets these relict areas also have significance as potential long term subglacial biologic refugia

beryllium 10 exposure ages of erratic boulders in southern norway and implications for the history of the fennoscandian ice sheet the margins of the fennoscandian ice sheet fis during the last glacial maximum lgm are fairly well constrained yet the thickness of the fis and its temporal evolution are poorly known here we use beryllium 10 be 10 exposure ages of glacially transported boulders along three vertical transects in southern norway to determine past ice sheet elevations the ice surface elevation during the lgm at our westernmost site skala was likely at approximately 1440 in coinciding with a previously mapped trimline at our central site blaho the ice surface elevation at the lgm was at least at similar to 1620m likely closer to 1800m at elgahogna our easternmost site lgm ice was above the summit elevation of 1460m rapid deglaciation began at skala and blaho at approximately 13 5 14 5 10 beka and at approximately 12 be 10 ka at elgdhogna by approximately 9 be 10 ka the fis had thinned to below our lowest sample at each location periods of rapid thinning correlate with an exposure dated ice margin history as well as the glaciation curve for western scandinavia our data when combined with previous bedrock and blockfield highly weathered bedrock on summits exposure ages resolve a long standing debate over the age and geomorphic interpretation of blockfields and weathering zones in southern norway frozen bed low erosive ice clearly covered the summit blockfields at blaho and especially at elgdhogna where we find a large and progressive divergence between boulder and bedrock exposure ages with elevation we conclude that the lower limit of blockfields in these areas should be interpreted as an englacial thermal boundary rather than the upper limit of the lgm fis and that blockfields have survived multiple glacial cycles we also compare our deglaciation record with several models of the fis models that predict how the fis changed during deglaciation either through inversion of crustal rebound or through climate dependent forward modeling generally match our exposure ages reasonably well during deglaciation but predict larger lgm surface elevations than our data indicate on the other hand the climap maximum model which provides lgm elevations only agrees with our results fairly well c 2007 elsevier ltd all rights reserved

the timing of the weichselian pomeranian ice marginal position south of the baltic sea a critical review of morphological and geochronological results abstract the pomeranian phase of the weichselian glaciation in northern middle europe has been the object of investigation in various studies aiming to derive numerical ages for this specific phase apart from traditional 14 c chronologies surface exposure dating with in situ produced terrestrial cosmogenic nuclides and optically stimulated luminescence dating have been applied by different authors the ages derived are so far not consistent generally cosmogenic exposure dating results in younger ages 15 ka and luminescence dating results in older ages 20 ka for the formation of the pomeranian phase the apparent age gap has been subject to discussions from both methodological and geomorphological viewpoints we recalculated compiled exposure ages with a recent calibration data set which reflects very recent progress in cosmogenic nuclide dating and received results that differ significantly from the originally published ages the newly calculated ages deviate 9 15 from the original ages from the source studies towards the older age range thus reducing the offset between the different dating methods and supporting the theory that the onset of the pomeranian phase was earlier in the marine isotope stage 2 in one example from northeast germany good agreement between both methods results from the recalculations corroborated also by the local geomorphology nevertheless postdepositional movement of glacial boulders as well as erosion and shielding effects are hard to quantify and most probably cause an underestimation of exposure ages the study aims to contribute to a critical evaluation of existent chronologies for the southern margin of the scandinavian ice sheet

constraining holocene 10be production rates in greenland the absence of a production rate calibration experiment on greenland has limited the ability to link 10be exposure dating chronologies of ice margin change to independent records of rapid climate change we use radiocarbon age control on holocene glacial features near jakobshavn isbrae western greenland to investigate 10be production rates the radiocarbon chronology is inconsistent with the 10be age calculations based on the current globally averaged 10be production rate calibration data set but is consistent with the 10be production rate calibration data set from north eastern north america which includes a calibration site nearby on north eastern baffin island based on the best dated feature available from the jakobshavn isbrae forefield we derive a 10be production rate value of 3 98 0 24 atoms g a 1 using the st scaling scheme which overlaps with recently published reference 10be production rates we suggest that these 10be production rate data or the very similar data from north eastern north america are used on greenland copyright 2011 john wiley sons ltd

new age constraints for the limit of the british irish ice sheet on the isles of scilly the southernmost terrestrial extent of the irish sea ice stream isis which drained a large proportion of the last british irish ice sheet impinged on to the isles of scilly during marine isotope stage 2 however the age of this ice limit has been contested and the interpretation that this occurred during the last glacial maximum lgm remains controversial this study reports new ages using optically stimulated luminescence osl dating of outwash sediments at battery tresco 25 5 1 5 ka and terrestrial cosmogenic nuclide exposure dating of boulders overlying till on scilly rock 25 9 1 6 ka which confirm that the isis reached the isles of scilly during the lgm the ages demonstrate this ice advance on to the northern isles of scilly occurred at 26 ka around the time of increased ice rafted debris in the adjacent marine record from the continental margin which coincided with heinrich event 2 at 24 ka osl dating 19 6 1 5 ka of the post glacial hell bay gravel at battery suggests there was then an 5 ka delay between primary deposition and aeolian reworking of the glacigenic sediment during a time when the isis ice front was oscillating on and around the ll n peninsula 390 km to the north

cosmogenic 10 be dating of the salpausselka i moraine in southwestern finland abstract we determined in situ cosmogenic 10 be ages for nine boulders sampled on the salpausselka i ss i moraine previous dating of this moraine indicated that it formed during the younger dryas stadial along the southern margin of the scandinavian ice sheet in southern finland our new exposure ages range from 10 9 1 0 to 13 5 1 2 10 be ka with an error weighted mean age of 12 4 0 7 10 be ka our results confirm four previous 10 be ages obtained 40 km northeast of our sample location the combined data n 13 indicate that retreat from the ss i moraine occurred at 12 5 0 7 10 be ka in excellent agreement with an age of 12 1 ka for retreat from the ss i moraine based on varve chronologies these results identify the ss i moraine as among the best dated margins associated with late quaternary ice sheets

10be cosmic ray exposure dating of moraines and rock avalanches in the upper romanche valley french alps evidence of two glacial advances during the late glacial holocene transition abstract cosmic ray exposure cre dating of moraines allow glacier fluctuations and past climate change reconstructions in the french alps there is a lack of moraine dating for the late glacial holocene transition period here we present a chronology of glacier advances in the upper romanche valley french alps massif des ecrins based on 10 be cre dating cre ages of moraines of 13 0 1 1 ka and 12 4 1 5 ka provide evidence for two stages of glacial advance or standstill at the end of the late glacial the cre dating of a rock avalanche deposit at 12 2 1 5 ka is attributed to post glacial debuttressing and reveals rapid deglaciation at the end of the late glacial a cre age of 7 1 0 7 ka of a second mass wasting whose triggering factor is unidentified so far indicates that up to an altitude of 2300 m a s l the valley was ice free as of 7 kyr at the latest the re evaluation of 21 moraine 10 be cre ages from nine glacial valleys across the alps shows multiple glacial advances occurring at the late glacial holocene transition these results lead to a re evaluation of the importance of cooling events during the allerod and the younger dryas in the alps

holocene ice recession at polygon spur reedy glacier antarctica the holocene history of outlet glaciers affords information on the behavior and mechanisms controlling the extent of the east antarctic ice sheet here we present both new radiocarbon and recalcul

redating the moraines in the kromer valley silvretta mountains new evidence for an early holocene glacier advance among the many well preserved moraine systems that are found throughout the austrian silvretta mountains a set of prominent moraines in the upper kromer valley located in front of the little ice

tectonic and climatic control on terrace formation coupling in situ produced 10be depth profiles and luminescence approach danube river hungary central europe abstract the terrace sequence of the hungarian part of the danube valley preserves a record of varying tectonic uplift rates along the river course and throughout several climate stages to establish the chronology of formation of these terraces two different dating methods were used on alluvial terraces exposure age dating using in situ produced cosmogenic 10 be and luminescence dating using monte carlo approach to model the denudation rate corrected exposure ages in situ produced cosmogenic 10 be samples originated from vertical depth profiles enabled the determination of both the exposure time and the denudation rate post ir irsl measurements were carried out on k feldspar samples to obtain the ages of sedimentation the highest terrace horizon remnants of the study area provided a best estimate erosion corrected minimum 10 be exposure age of 700 ka we propose that the abandonment of the highest terrace of the hungarian danube valley was triggered by the combined effect of the beginning tectonic uplift and the onset of major continental glaciations of quaternary age around mis 22 for the lower terraces it was possible to reveal close correlation with mis stages using irsl ages the new chronology enabled the distinction of tiib 90 ka mis 5b c and tiiia 140 ka mis 6 in the study area surface denudation rates were well constrained by the cosmogenic 10 be depth profiles between 5 8 m ma and 10 0 m ma for all terraces the calculated maximum incision rates of the danube relevant for the above determined 700 ka time span were increasing from west

final deglaciation of the scandinavian ice sheet and implications for the holocene global sea level budget abstract the last deglaciation of the scandinavian ice sheet sis from 21 000 to 13 000 yr ago is well constrained by several hundred 10be and 14c ages the subsequent retreat history however is established primarily from minimum limiting 14c ages and incomplete baltic sea varve records leaving a substantial fraction of final sis retreat history poorly constrained here we develop a high resolution chronology for the final deglaciation of the sis based on 79 10be cosmogenic exposure dates sampled along three transects spanning southern to northern sweden and finland combining this new chronology with existing 10be ages on deglaciation since the last glacial maximum shows that rates of sis margin retreat were strongly influenced by deglacial millennial scale climate variability and its effect on surface mass balance with regional modulation of retreat associated with dynamical controls ice volume estimates constrained by our new chronology suggest that the sis contributed 8 m sea level equivalent to global sea level rise between 14 5 ka and 10 ka final deglaciation was largely complete by 10 5 ka with highest rates of sea level rise occurring during the bolling allerod a 50 decrease during the younger dryas and a rapid increase during the early holocene combining our sis volume estimates with estimated contributions from other remaining northern hemisphere ice sheets suggests that the antarctic ice sheet ais contributed 14 4 5 9 m to global sea level rise since 13 ka this new constraint supports those studies that indicate that an ice volume of 15 m or more of equivalent sea level rise was lost from the ais during the last deglaciation

10be surface exposure ages on the late pleistocene and holocene history of linnebreen on svalbard abstract arctic glaciers were sensitive to past changes in high latitude winter precipitation and summer temperature here we develop a late pleistocene to holocene history for linnebreen linne glacier in western svalbard using 10 be surface exposure ages on isolated erratic and moraine boulders we show that linnebreen had separated from the larger ice sheet over svalbard and was retreating up valley around the start of the younger dryas cold period we attribute this retreat during a cold period on svalbard to moisture starvation of linnebreen from advanced sea ice and or elevated shortwave boreal summer insolation that overwhelmed any reduction in sensible heat after an ice free period during the early to middle holocene linnebreen reformed sometime after 4 6 0 2 ka and was at a position roughly equivalent to its little ice age lia maximum extent before it began to retreat at 1 6 0 2 ka comparison with calibrated 14 c dates from three other glaciers could suggest that this period of ice retreat at 1 6 ka could be regional in extent linnebreen occupied the pre lia moraine when there was an increased ratio of cold arctic sourced relative to warm atlantic sourced waters around svalbard and advanced sea ice the retreat of linnebreen at 1 6 ka was concurrent with the increased presence of warm atlantic waters around svalbard and attendant sea ice retreat these coincident changes in ocean temperatures sea ice extent and linnebreen moraine age could imply a climatic forcing of the pre lia advance and retreat of linnebreen summer temperatures rather than changes in precipitation would then be dominant in driving ice retreat although the possibility of stochastic glacier margin variability cannot be excluded our data therefore suggest that linnebreen may have responded differently to past changes in sea ice extent that could depend on the background climate state deglacial climate vs late holocene climate which highlights the complexity in climatic controls on arctic glaciers

a relict landscape in the centre of fennoscandian glaciation cosmogenic radionuclide evidence of tors preserved through multiple glacial cycles the presence of well developed tors boulder fields and weathering mantles in the parkajoki area of northeastern sweden near the centre of fennoscandian glaciation has been used to suggest that these landscapes were preserved during all glacial cycles since ice sheet initiation in the late cainozoic this implies that all successive large scale glaciations must have had frozen bed conditions across this area to allow for subglacial landscape preservation cosmogenic 10be and 26al data from three tors and a meltwater channel in the parkajoki area were used to test this hypothesis of landscape preservation through multiple glacial cycles apparent exposure ages of tor summit bedrock surfaces ranging between 79 and 37 ka in an area deglaciated at 11 ka are consistent with the interpretation of these features as relict landforms that have survived glaciation with little or no erosion single nuclide minimum exposure age data require that the tors have survived at least two complete glacial cycles this estimate is based on i the approximate duration of periods of ice sheet cover versus ice free conditions as deduced from the dsdp 607 marine benthic foraminifer oxygen isotope record in conjunction with ii a record of fennoscandian ice sheet flow traces and hence ice sheet extent and iii noting that cosmogenic nuclides are accumulated only during ice free periods in addition mean cosmogenic 26al 10be concentration ratios from two of the sites indicate a minimum model total history of 605 ka and a maximum erosion rate of 1 6 m ma 1 thus the numerical ages confirm the overall qualitative interpretation of landscape preservation through multiple glacial cycles

scaling time integrated in situ cosmogenic nuclide production rates using a continuous geomagnetic model abstract spatial and temporal variations in earth s magnetic field affect the corresponding time integrated distribution of in situ cosmogenic nuclide cn production rates these effects can be quantified by the effective vertical cutoff rigidity r c a measure of the energy required for primary cosmic rays to penetrate the geomagnetic field and interact with the atmosphere at a given location recent cn production rate scaling models are based on atmospheric cosmic ray measurements parameterized using r c estimates derived from detailed modern geomagnetic field representations which include both dipole and non dipole field contributions however published methods for quantifying time integrated geomagnetic effects on cn production rate scaling rely on various geocentric dipolar approximations to r c driven by separate records of paleomagnetic pole position and paleointensity therefore applying dipolar paleomagnetic records spanning millennial time scales which explicitly ignore past non dipole effects to scaling models derived using modern geomagnetic field representations may lead to systematic errors in any calculated results a recently published continuous geomagnetic model covering the last 7 kyr cals7k 2 m korte and c g constable continuous geomagnetic field models for the past 7 millennia 2 cals7k 2005 geochem geophys geosyst 6 q02h16 doi 10 1029 2004gc000801 may allow reduction of such errors by bridging the gap between detailed modern geomagnetic and simplified paleomagnetic models we have developed a new model framework describing temporal and spatial variation in r c for 0 7 ka and earlier based on cals7k 2 which explicitly accounts for non dipole field effects while attempting to mitigate systematic scaling biases scaling factors derived using the new r c framework predict significant longitudinal variability in time integrated cn production while predictions using dipolar geomagnetic approximations do not one can test these predictions using in situ cosmogenic 14 c in situ 14 c in quartz due to its short half life 5 73 kyr 14 c attains secular equilibrium between production and decay after approximately 25 kyr of exposure at which point its measured concentration is only a function of its integrated average production rate initial in situ 14 c results from samples at secular equilibrium from 38 n and 3 5 km in tibet and eastern california are consistent with the longitudinal variability predicted by the new framework

atmospheric scaling of cosmogenic nuclide production climate effect 1 absorption of cosmic rays by atmospheric mass varies temporally due to a redistribution of atmospheric pressure by ice sheets during glaciations the compression and expansion of the atmosphere due to cooling and warming and changes in katabatic winds near large ice masses these atmospheric processes can result in changes in production rates of cosmogenic nuclides which when integrated over long exposure durations may result in 0 to 5 adjustments in site production rates depending on location combining a ccm3 model with imbedded ice sheets for 20 ka we show that production rates changes relative to today are greatest at high elevations 6 7 at 5 km altitude due to atmospheric compression from decreased temperature production rates at specific times for sites near ice sheet margins can be reduced more than 10 due to a combination of katabatic winds draining off the ice sheet margins and atmospheric cooling nunatak settings may be significantly affected by the climate effect due to persistent glacial atmospheric conditions atmospheric variability may explain some of the disparities among cosmogenic nuclide production rate calibrations

sea level fluctuations imply that the younger dryas ice sheet expansion in western norway commenced during the allerod after the first emergence following deglaciation relative sea level rose by 10 m in western norway and culminated late in the younger dryas yd the relative sea level history reconstructed by dating deposits in isolation basins shows a sea level low stand between 13 640 and 13 080 cal yr bp a 10 m sea level rise between 13 080 and 11 790 cal yr bp and a sea level high stand between 11 790 and 11 550 cal yr bp shortly after the yd holocene boundary sea level fell abruptly by 37 m the shorelines formed during the sea level low stand in the mid allerod and during the sea level high stand in the yd have almost parallel tilts with a gradient of 1 3 m km 1 indicating that hardly any isostatic movement has taken place during this period of sea level rise we conclude that the transgression was caused by the major re advance of the scandinavian ice sheet that took place in western norway during the lateglacial the extra ice load halted the isostatic uplift and elevated the geoid due to the increased gravitational attraction on the sea our results show that the crust responded to the increased load well before the yd starting 12 900 cal yr bp with a sea level low stand at 13 640 cal yr bp and the subsequent yd transgression starting at 13 080 cal yr bp thus we conclude that the so called yd ice sheet advance in western norway started during the allerod possibly more than 600 years before the allerod yd transition r 2007 elsevier ltd all rights reserved

scaling factors for production rates of in situ produced cosmogenic nuclides a critical reevaluation abstract new scaling factors are presented describing the altitude and latitudinal dependence of production rates for in situ produced cosmogenic nuclides the new factors incorporate the influence of the non dipole contributions to the geomagnetic field on the cosmic ray flux the currently used scaling factors of lal earth planet sci lett 104 1991 424 439 are based on the assumption of a dipole field the overall strategy used in deriving the new scaling factors is however very similar to that of lal and relies on the same and or similar nuclear data in this reevaluation data are only used if the effective geomagnetic parameters inclination horizontal field strength can be reconstructed for the time of measurement the absorption free pathlengths for cosmic rays selected for this study are based on observational data at altitudes relevant for exposure age dating sea level to 7000 m at sea level and latitudes between 20 and 40 the new factors are up to 18 lower and at high altitudes more than 30 higher than those of lal in addition to accounting for the influence of the effective geomagnetic field and providing more applicable estimates of the new factors also allow for correction for the significant deviations from the standard pressure altitude relationship that exist in the atmosphere 10

holocene fluctuations of bregne ice cap scoresby sund east greenland a proxy for climate along the greenland ice sheet margin abstract the greenland ice sheet is a major component of the arctic cryosphere and the magnitude of its response to future climate changes remains uncertain longer term records of climate near the ice sheet margin provide information about natural climate variability and can be used to understand the causes of past changes in the greenland ice sheet as a proxy for holocene climate near the ice sheet margin we reconstruct the fluctuations of bregne ice cap in the scoresby sund region of central east greenland bregne is a small ice cap 2 5 km 2 in area and responds sensitively to summer temperatures we employ a multi proxy approach to reconstruct the ice cap fluctuations using geomorphic mapping 10 be ages of boulders and bedrock and lake sediment records past extents of bregne ice cap are marked by moraines and registered by sediments in downvalley lakes 10 be ages of bedrock and boulders outboard of the moraines indicate that bregne ice cap was within 250 m of its present day limit by at least 10 7 ka multi proxy data from sediments in two move lake located downvalley from bregne ice cap indicate that the ice cap likely completely disappeared during early and middle holocene time increasing magnetic susceptibility and percent clastic material from 6 5 to 1 9 cal ka bp in two move lake sediments suggest progressively colder conditions and increased snow accumulation on the highlands west of the lake laminated silt deposited at 2 6 cal ka bp and 1 9 cal ka bp to present registers the onset and persistence of bregne ice cap during the late holocene 10 be ages of boulders on an unweathered unvegetated moraine in the bregne ice cap forefield range from 0 74 to 9 60 ka the youngest 10 be age 0 74 ka likely represents the age of the moraine whereas older ages may be due to 10 be inherited from prior periods of exposure this late holocene moraine marks the second largest advance of the ice cap since deglaciation of the region at the end of the last ice age the oldest moraine in the forefield dates to 2 6 cal ka bp the fluctuations of bregne ice cap were likely influenced by northern hemisphere summer insolation throughout the holocene and abrupt late holocene cold events

very low inheritance in cosmogenic surface exposure ages of glacial deposits a field experiment from two norwegian glacier forelands terrestrial cosmogenic nuclide dating has been widely used to estimate the surface exposure age of bedrock and boulder surfaces associated with deglaciation and holocene glacier variations but the

repeated catastrophic valley infill following medieval earthquakes in the nepal himalaya geomorphic footprints of past large himalayan earthquakes are elusive although they are urgently needed for gauging and predicting recovery times of seismically perturbed mountain landscapes we present evidence of catastrophic valley infill following at least three medieval earthquakes in the nepal himalaya radiocarbon dates from peat beds plant macrofossils and humic silts in fine grained tributary sediments near pokhara nepal s second largest city match the timing of nearby m 8 earthquakes in 1100 1255 and 1344 c e the upstream dip of tributary valley fills and x ray fluorescence spectrometry of their provenance rule out local sources instead geomorphic and sedimentary evidence is consistent with catastrophic fluvial aggradation and debris flows that had plugged several tributaries with tens of meters of calcareous sediment from a higher himalayan source 60 kilometers away

deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research