the cosmogenic 21ne production rate in quartz evaluated on a large set of existing 21ne 10be data abstract based on a compilation of published combined 10 be and 21 ne cosmogenic nuclide data sets from quartz samples obtained at eth zurich we assess the 21 ne 10 be p21 p10 production rate ratio with the goal to determine the 21 ne production rate p21 in quartz a variety of sliding erosion islands in a 21 ne 10 be versus 10 be diagram were evaluated to find the one that fits the data best which in turn yields the most probable p21 if the 10 be production rate is known the approach minimizes the influence of samples with a complex exposure history a best fit value for p21 p10 sp sp the 10 be fraction being produced by spallation as opposed to production by muons of 4 23 0 17 is obtained for a 10 be half life of 1 39 ma adopting a p10 sp value in quartz of 4 41 0 52 at g 1 yr 1 this yields a p21 of 18 7 2 3 at g 1 yr 1 it is possible that 2 of the 21 ne is produced by fast muons

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

the 21ne production rate in quartz revisited abstract i have revised our earlier production rate determination of 21ne in terrestrial quartz s niedermann th graf j s kim c p kohl k marti and k nishiizumi 1994 earth planet sci lett 125 341 355 taking account of improved knowledge about the exposure age of samples used in that work and applying distinct procedures for scaling to sea level and high latitudes the corrected value of 19 0 3 7 atoms g 1 a 1 is in excellent agreement with expectations based on nuclear properties j masarik and r c reedy 1995 earth planet sci lett 136 381 395 and closely corresponds to the present day production rate in the case of substantial variations of the geomagnetic field in the past as proposed by several studies the revised value can consistently be used with suitable correction methods

dating of sirius group tillites in the antarctic dry valleys with cosmogenic3he and21ne we measured in situ produced cosmogenic3he and21ne in boulder and bedrock surface samples in and near sirius group tillites from two localities in southern victoria land antarctica pyroxene quantitatively retains cosmogenic3he for millions of years the deposit at mt fleming has a minimum exposure age of 6 5 ma while 6 ma is a probable minimum age for the table mountain tillite these lower limits not taking into account erosion of the sampled surfaces are based on the samples with the highest concentrations of cosmogenic noble gases and currently accepted production rates since the plagioclase bearing mt fleming samples almost certainly lost part of their cosmogenic ne the minimum exposure age at this location is presumably even 50 higher than the stated value the concentrations of cosmogenic ne in our samples constrain uplift rates of the transantarctic mountains to 170 m ma these data contradict the hypothesis of a collapse of the east antarctic ice sheet in the pliocene coupled with high uplift rates and support the model of a stable ice sheet since the middle miocene

dating the incision of the yangtze river gorge at the first bend using three nuclide burial ages incision of the yangtze river gorge is widely interpreted as evidence for lower crustal flow beneath the southeast margin of the tibetan plateau previous work focused on the onset of incision but the duration of incision remains unknown here we present cosmogenic nuclide burial ages of sediments collected from caves on the walls of the gorge that show the gorge was incised 1 km sometime between 18 and 9 ma thereafter incision slowed substantially we resolve middle miocene burial ages by using three nuclides and accounting for in situ muogenic production this approach explains the absolute concentrations of 10be 26al and 21ne as well as 26al 10be and 21ne 10be ratios a declining incision rate challenges existing geodynamic interpretations by suggesting that either 1 surface uplift has ceased immediately south of the plateau margin or 2 gorge incision is not a useful proxy for the timing of surface uplift

cosmogenic beryllium 10 and neon 21 dating of late pleistocene glaciations in nyalam monsoonal himalayas we present cosmogenic 10be and 21ne chronologies from 21 erratic boulders on three moraine sequences in nyalam county monsoonal himalayas southern margin of the tibetan plateau the surface exposure ages provide evidence for at least two distinct glacial advances during the late stage of the last glacial cycle and for one or more significantly older glaciations the distribution of cosmogenic ages from the three ridges of the old moraine sequence is inconsistent with their stratigraphic order because exposure periods of the erratics prior to deposition on the moraine surface is shown to be small the chronology stratigraphy mismatch suggests that the cosmogenic ages do not date moraine deposition but most likely significant moraine ridge denudation and related boulder exhumation after initial deposition of the moraines during the penultimate glacial cycle or earlier the surface exposure ages based on various currently accepted production rate scaling protocols yield age differences of up to 35 reflecting the poor knowledge of terrestrial cosmogenic production rates at low latitude high altitude sites even within this conservative uncertainty range our results do not yield evidence for late pleistocene glaciations in monsoonal tibet to be asynchronous to those in mid latitudes on both hemispheres there is an urgent need to improve the knowledge of terrestrial cosmogenic nuclide production rates and their scaling to low latitude regions to fully exploit the climate information archived in tropical moraine sequences

degradation of glacial deposits quantified with cosmogenic nuclides quartermain mountains antarctica many glacial deposits in the quartermain mountains antarctica present two apparent contradictions regarding the degradation of unconsolidated deposits the glacial deposits are up to millions of years old yet they have maintained their meter scale morphology despite the fact that bedrock and regolith erosion rates in the quartermain mountains have been measured at 0 1 4 0 m ma 1 additionally ground ice persists in some miocene aged soils in the quartermain mountains even though modeled and measured sublimation rates of ice in antarctic soils suggest that without any recharge mechanisms ground ice should sublimate in the upper few meters of soil on the order of 103 to 105 years this paper presents results from using the concentration of cosmogenic nuclides beryllium 10 10be and aluminum 26 26al in bulk sediment samples from depth profiles of three glacial deposits in the quartermain mountains the measured nuclide concentrations are lower than expected for the known ages of the deposits erosion alone does not always explain these concentrations and deflation of the tills by the sublimation of ice coupled with erosion of the overlying till can explain some of the nuclide concentration profiles the degradation rates that best match the data range 0 7 12 m ma 1 for sublimation of ice with initial debris concentrations ranging 12 45 and erosion of the overlying till at rates of 0 4 1 2 m ma 1 overturning of the tills by cryoturbation vertical mixing or soil creep is not indicated by the cosmogenic nuclide profiles and degradation appears to be limited to within a few centimeters of the surface erosion of these tills without vertical mixing may partially explain how some glacial deposits in the quartermain mountains maintain their morphology and contain ground ice close to the surface for millions of years copyright 2010 john wiley sons ltd

cosmic ray produced 21ne in terrestrial quartz the neon inventory of sierra nevada quartz separates the study of cosmic ray produced radioactive and stable nuclides on the surface of the earth can provide relevant geomorphological and glaciological information at present the cosmic ray production rates of stable 21ne are not well known this study attempts to remedy the situation by determining the production rate ratio of 21ne and 26al p21p26 in quartz 26al concentrations and p26 rates have previously been investigated for quartz separates of sierra nevada rocks which were brought to the surface by glacial scouring during the tioga period at the end of the last ice age 1 we used splits of the same samples for our studies and found that ne in these rocks represents a mixture of several components trapped ne nucleogenic 21ne and 22ne produced by n reactions in oxygen and fluorine respectively as well as cosmic ray produced ne which is the component of interest in this study the trapped component was substantially lost in one sample w86 12 by crushing and by a density separation of the grain sizes 38 90 m and 90 125 m permitting the resolution of the in situ produced 21ne into cosmic ray spallation and n produced components and the determination of a lower limit to p21p26 in a second sample w86 8 one split contained small enough amounts of nucleogenic 21ne to permit the determination of a reasonable upper limit to p21p26 the two ratio determinations are consistent within error limits and the value adopted 0 65 0 11 2 agrees with ratios observed in extraterrestrial matter apparently p21p26 is thus not very sensitive to the neutron spectrum however the observed production rate ratio is substantially larger than theoretical estimates for si targets reflecting poorly known neutron excitation functions the above p21p26 value coupled to the observed 26al production rate 1 corresponds to a 21ne production rate of p21 21 atoms g 1 a 1 in quartz or to p21 45 atoms g si 1 a 1 at sea level and high latitudes this rate is based on an adopted exposure age of 11 000 yr for our quartz samples

controls on subaerial erosion rates in antarctica erosion rates offer insight on landscape development and the relative importance of chemical and physical processes of weathering minimal chemical weathering makes antarctica an ideal location in which to compare the physical weathering of carbonate rocks to other lithologies here we report the first cosmogenic nuclide derived erosion rates for carbonate rocks in antarctica carbonate samples collected in the southernmost ellsworth mountains reflect a 36cl erosion rate of 0 22 0 02 mm ka this erosion rate is consistent with other reported antarctic erosion rates but is lower than 36cl erosion rates derived from other arid regions in the world these results are integrated with a continent wide reanalysis of 28 erosion rate studies 200 measurements which comprise numerous rock types and other cosmogenic nuclides by combining cosmogenic nuclide derived erosion rates across studies the larger trends provide insight into factors e g lithology glacial history and availability of abrasive material affecting subaerial erosion rates in antarctica statistical analysis of the compiled data set shows differences based on lithology with sandstone having the largest range of erosion rates the compiled data also reveals higher erosion rates in areas with a large potential sediment supply like the dry valleys samples collected from boulders yield lower erosion rates than those collected from bedrock likely due to a combination of physical processes that affect boulders and bedrock differently and glacial history which can affect the apparent cosmogenic nuclide derived erosion rate

minimum 10be exposure ages of early pliocene for the table mountain plateau and the sirius group at mount fleming dry valleys antarctica using accelerator mass spectrometry ams we have measured 10be and 26al in quartz from granites and sandstones from table mountain and mount fleming antarctica our data show that the plateau surface at table mountain had formed by early pliocene time at the latest granites fringing but within the sirius group at table mountain give a minimum exposure age of 2 6 ma for this deposit a sandstone clast on the ferrar dolerite surface just outside and below and thus postdating the sirius group has a minimum age of 2 9 ma two samples from the sirius group at mount fleming have 10be concentrations that have reached secular equilibrium this deposit is at least 4 8 m y old the sirius group at mount fleming cannot have been deposited after 3 0 2 5 ma as implied by biostratigraphic data our dates contradict the hypothesis that in the pliocene east antarctica was deglaciated and the climate was significantly warmer and wetter the preservation of these surfaces indicates a continuous cold desert in the dry valleys since the beginning of the pliocene the high 10be concentrations we have measured cannot be reconciled with uplift of the transantarctic mountains at a rate of 1 km m y during the past 3 m y

cenozoic landscape evolution of the convoy range to mackay glacier area transantarctic mountains onshore to offshore synthesis on the basis of geomorphic mapping we reconstruct the landscape evolution of the convoy range to mackay glacier area of the rifted margin of the transantarctic mountains and compare the land record with that obtained from offshore marine sedimentary rocks in the ross sea three landform assemblages reflect 1 fluvial planation and dissection 2 local glaciation under temperate conditions and 3 overriding by the east antarctic ice sheet overall landscape evolution is typical of a passive continental margin contrasts in morphology between the convoy range and the adjacent dry valleys and royal society mountains reflect the varying location of the initial drainage divide in relationship to the rifted coast in a wider synthesis we draw the following conclusions for the 260 km long mcmurdo sector of the transantarctic mountains denudation since rifting at ca 55 ma has removed a wedge 4 7 km thick at the coast declining inland to 1 km most denudation occurred in the eocene from planation and incision of river valleys near the coast a subsequent pulse of denudation most rapid at 34 31 ma and declining until ca 17 ma coincided with further crustal extension and a change from cool temperate to polar climate during the same interval there was a progressive decrease in landscape modification by warm based glaciers and or rivers between 14 8 and 13 6 ma the maximum overriding antarctic ice sheet flowed northeastward across the mountains leaving meltwater features crossing high altitude saddles and areally scoured bedrock near the coast since 13 6 ma the landscape has seen little change under a hyperarid polar climate either by local glaciers or subaerially fragile middle miocene surficial deposits still survive there has been tectonic stability since the middle miocene

an improved experimental determination of cosmogenic 10be 21ne and 26al 21ne production ratios in quartz abstract the confidence in surface exposure dating and related research such as erosion rate studies or burial dating strongly depends on the accuracy and precision of the currently used production rates of in situ produced cosmogenic nuclides reducing the uncertainties of nuclide production rates by more accurate calibrations with independently dated natural rock surfaces is crucial for further improving the quantification of earth surface processes here we use surface samples from the 760 2 ka old bishop tuff in eastern california to quantify the 10 be 21 ne and 26 al 21 ne production rate ratios in quartz our determination is based on 1 measured nuclide concentrations of cosmogenic 10 be 21 ne and 26 al 2 a conservative estimate for the erosion of the tuff in the volcanic tableland area which we base on our previously published 21 ne concentrations goethals m m niedermann s hetzel r fenton c r 2009 determining the impact of faulting on the rate of erosion in a low relief landscape a case study using in situ produced 21 ne on active normal faults in the bishop tuff california geomorphology 103 401 413 and a conservative estimate for the uncertainty of the 21 ne production rate and 3 the assumption of steady state erosion other assumptions such as the applied scaling procedure the muon contribution to nuclide production or the attenuation lengths of neutrons and muons in rock do not substantially affect the results based on 13 samples the following average production rate ratios and conservative uncertainty estimates are obtained for sea level high latitude open sky and rock surface 0 249 0 009 or 0 232 0 009 for 10 be 21 ne using 10 be half lives of 1 51 and 1 39 ma respectively and 1 80 0 09 for 26 al 21 ne for an 26 al half life of 0 72 ma the 10 be 21 ne and the 26 al 21 ne production ratios are consistent with currently used production rates but the ratios are much more precise than previous determinations the resulting 26 al 10 be production ratio of 7 23 0 45 for a 10 be half life of 1 51 ma or 7 76 0 49 for a 10 be half life of 1 39 ma is high when compared to previously published values we discuss reasons for this difference amongst them the possibility that 26 al analyses in general might be compromised by artefacts affecting the stable al concentration measurements when combined with a 10 be production rate of 5 01 at g 1 a 1 for the 1 51 ma half life or 4 61 at g 1 a 1 for the 1 39 ma half life our production ratios convert to 21 ne and 26 al production rates of 20 1 and 36 2 at g 1 a 1 or 19 9 and 35 7 at g 1 a 1 respectively

the age and origin of the labyrinth western dry valleys antarctica evidence for extensive middle miocene subglacial floods and freshwater discharge to the southern ocean a 50 km long network of bedrock channels and scoured terrain occupies the ice free portion of a major trough that crosses the transantarctic mountains in southern victoria land the channels collectively termed the labyrinth emerge from beneath the margin of the east antarctic ice sheet wright upper glacier and are incised into a 300 m thick sill of ferrar dolerite at the head of wright valley upper and intermediate elevation erosion surfaces of the labyrinth exhibit striations and molding characteristic of glacial erosion channels and canyons on the lower surface are as much as 600 m wide and 250 m deep have longitudinal profiles with many reverse gradients and contain potholes 35 m deep at tributary junctions these characteristics are most consistent with incision from fast flowing subglacial meltwater estimated discharge is on the order of 1 6 2 2 10 6 m 3 s 1 our 40 ar 39 ar analyses of volcanic tephra from the labyrinth show that the chan nels are relict that major channel incision predates 12 4 ma and that the last major subglacial flood occurred sometime between 14 4 ma and 12 4 ma the most plausible origin for the labyrinth is erosion associated with episodic drainage of subglacial lakes in east antarctica one compelling possibility is that discharge of large volumes of sub glacial meltwater to the southern ocean and to the ross sea in particular may have coincided with and contributed to oscillations in regional and or global climate during the middle miocene

pothole and channel system formation in the mcmurdo dry valleys of antarctica new insights from cosmogenic nuclides large pothole and channel features 15 m deep 30 m wide carved into the beacon sandstone in the upland dry valleys of antarctica have been used to infer catastrophic subglacial flooding beneath an expanded east antarctic ice sheet that overran the transantarctic mountains during the mid miocene though the age and erosion rates of these geomorphic features have not been quantified preservation of the potholes and channels has been attributed to negligible erosion under consistent polar desert conditions since the retreat of the ice sheet at 14 ma we present cosmogenic 21 ne and 10 be data

production rate of cosmogenic 21ne in quartz estimated from 10be 26al and 21ne concentrations in slowly eroding antarctic bedrock surfaces abstract we estimated the production rate of 21ne in quartz using a set of samples from slowly eroding sandstone surfaces in the antarctic dry valleys geologic evidence as well as cosmogenic 10be and 26al concentrations indicate that i these sites have experienced millions of years of surface exposure at low erosion rates and ii steady erosion has been sustained long enough that surface 10be and 26al concentrations have reached equilibrium with the erosion rate under these conditions surface cosmogenic 21ne concentrations should be a function only of the erosion rate and the 21ne production rate as the erosion rate can be determined from 10be and 26al concentrations this allows an estimate of the 21ne production rate estimating the reference 21ne production rate on this basis with the assumption that all 21ne production is by neutron spallation yields a poor fit to measured 21ne concentrations and a systematic residual that is correlated with the erosion rate of the sample site the same steady erosion assumption with a production model that includes production by deeply penetrating muons yields a good fit both to our measurements and to similar independent measurements from an antarctic bedrock core both data sets together yield a total reference 21ne production rate of 18 3 0 4 atoms g 1 a 1 of which 0 66 0 10 atoms g 1 a 1 is due to muon interactions

geomorphological evidence of cold based glacier activity in south victoria land antarctica cold based glaciers have long been recognized as capable of covering and protecting landscapes however recent studies of modern cold based glaciers in antarctica show that in some situations erosion deformation and deposition can occur recognizing the dual ability of cold based glaciers to protect and preserve surfaces on the one hand and erode and modify on the other is important for correctly interpreting the often subtle imprint of cold based glaciers on landscapes a range of geomorphological features related to cold based glacier activity has now been documented along with an improved understanding of cold based glacier structure processes and interaction with various substrates collectively this provides an enhanced ability to understand the impact of cold based glaciers on landscapes and reappraise the geomorphological record such insight allows recognition of previously unknown glacial events and better interpretations of the landscape exposure record this is particularly important at the margins of the antarctic ice sheets where past fluctuations in ice sheet volume and its contributions to post glacial sea level rise are poorly constrained this paper reviews the known geomorphological evidence associated with cold based glaciers in the south victoria land region of the transantarctic mountains it aims to provide progress towards a set of criteria for recognizing cold based glacier activity in other regions and to highlight the implications of cold based glacial activity for surface exposure studies and interpreting glacial history cold based glaciers are below pressure melting point throughout and are therefore frozen to the substrate and move primarily by internal deformation drewry 1986 this led to the long standing view that cold based glaciers cannot slide and are thus incapable of erosion and deposition and therefore protect the underlying surface while numerous studies have shown this to be true in many situations recent investigations of modern cold based glaciers have revealed that in some circumstances complex processes operate at subfreezing temperatures in the basal zone and that cold based glaciers can generate a variety of geomorphological features these studies have forced a reappraisal of the geomorphic effectiveness of cold based glaciers and have confirmed that they can both protect and modify landscapes e g fitzsimons 1996 atkins et al 2002 fitzsimons 2003 waller et al 2012 thus the debate has moved on and the challenge now is to understand the full range of processes and products associated with cold based glaciers and the implications for landscape development hambrey fitzsimons 2010 waller et al 2012 recognizing the often subtle features indicative of cold based glacial activity offers the potential to delineate and date previously unknown or poorly constrained glacial events this is particularly relevant for interpreting glacial history and modelling ice sheet reconstructions for example numerous surface exposure dating studies have been carried out on ice marginal landforms with the aim of constraining past variations in the ice sheet volume however many of these studies have produced inconsistent contradictory results including evidence of complex exposure histories suggesting episodes of burial and reworking by cold based ice e g strasky et al 2008 di nicola et al 2009 compared with warm based glaciers there are still relatively few studies of cold based glaciers and significant gaps in our understanding of the processes and products remains in addition lingering misconceptions regarding the geomorphic effectiveness of cold based glaciers and historic use of ambiguous terminology to describe cold based sediments and landforms mean that the evidence and implications of past cold based glacial events have yet to be fully appreciated by the wider geomorphological community this review provides a summary of known geomorphological features associated with cold based glaciers in the south victoria land region of antarctica it aims to provide a basis for recognizing similar features elsewhere and attempts to draw attention to the implications of cold based glacial geomorphology for the correct application of surface exposure dating studies and interpretation of cold based glacial history

26al 10be 21ne burial dating abstract cosmogenic nuclide burial dating relies on a pair of cosmic ray produced nuclides that are produced in the same rock or mineral target at a fixed ratio but have different half lives for example 26 al and 10 be are produced in quartz at 26 al 10 be 6 75 1 if a sample of quartz is exposed at the surface for a time 26 al and 10 be concentrations reflect this ratio if it is then buried below the penetration depth of cosmic rays production stops and both nuclides decay the half life of 26 al is half that of 10 be so the 26 al 10 be ratio decreases over time and can be used to date the burial event because quartz derived from surface erosion and then buried by sediment accumulation is common the method is widely applicable for dating plio pleistocene clastic sediments all terrestrial applications of burial dating so far have used the 26 al 10 be pair here we show that coupling cosmogenic 21 ne which is also produced in quartz with 26 al or 10 be should improve upon both the age range and accuracy of 26 al 10 be burial dating we establish the feasibility of this approach by 21 ne measurements at two sites that have already been dated using 26 al 10 be burial dating burial ages from all three nuclide pairs agree at both sites which shows that currently accepted values for decay constants and production ratios are internally consistent thus it is possible at present to increase the useful range of cosmogenic nuclide burial dating by incorporating 21 ne fully realizing the potential improvements in accuracy would benefit from additional estimates of 21 ne 26 al and 21 ne 10 be production ratios that are independent of the 26 al and 10 be decay constants

controls on interior west antarctic ice sheet elevations inferences from geologic constraints and ice sheet modeling abstract knowledge of the west antarctic ice sheet wais response to past sea level and climate forcing is necessary to predict its response to warmer temperatures in the future the timing and extent of past interior wais elevation changes provides insight to wais behavior and constraints for ice sheet models constraints prior to the last glacial maximum lgm however are rare surface exposure ages of glacial erratics near the wais divide at mt waesche in marie byrd land and at the ohio range in the transantarctic mountains range from 10 ka to 500 ka without a dependence on elevation the probability distribution functions pdf of the exposure ages at both locations are remarkably similar during the last glaciation maximum interior ice elevations as recorded by moraines and erratics were reached between 10 ka and 12 ka however most exposure ages are older than the lgm and cluster around 40 ka and 80 ka the peak in the exposure age distributions at 40 ka includes ages of alpine moraine boulders at mercer ridge in the ohio range comparison of the pdf of exposures ages from the ohio range and mt waesche with the temperature record from the fuji dome ice core indicates that the youngest peak in the exposure age distributions corresponds to the abrupt warming during the last glacial termination a prominent peak in the ohio range pdf corresponds to the penultimate termination stage 5e during the intervening glacial period there is not a consistent relationship between the peaks in the pdf at each location and temperature a combined ice sheet ice shelf model with forcing scaled to marine 18 o predicts that interior wais elevations near the ice divide have varied 300 m over the last glacial cycle peaks in the pdf correspond to model highstands over the last 200 ka in the simulated elevation history maximum ice elevations at ohio range 100 m and mt waesche 60 m occur at 10 ka in agreement with observations from these sites during collapse of the marine portion of the wais ice elevations at ohio range and mt waesche are drawn down at least 200 m below the present ice elevation the good correspondence between the model results and observations at both the ohio range and mt waesche supports the conclusion that interior wais highstands do not occur during glacial maximums rather the highstands are controlled primarily by increased accumulation during temperature maximums that occur early in the interglacials interior down draw events follow highstands resulting from the arrival of a wave of thinning triggered by retreat of the wais grounding line coupled with decreasing accumulation rates

active erosion deposition cycles in the hyperarid atacama desert of northern chile 10be 21 ne abstract there is significant debate over the rates and types of fluvial activity at the plio pleistocene boundary in the hyperarid atacama desert of chile to quantify fluvial processes and help resolve this debate we measure terrestrial cosmogenic nuclide tcn 10 be and 21 ne concentration depth profiles in three settings representing a chronosequence 1 a late pliocene alluvial fan representative of major regional deposits 2 a modern active channel and 3 an adjacent low terrace inset into the pliocene alluvium late pliocene deposits that are widely preserved in the region contain tcn profiles consistent with relatively rapid stripping of upland sediment at the plio pleistocene boundary deposits inset into these late pliocene features record cut and fill cycles that rework sediment throughout the quaternary the tcn profile in the modern channel is best explained by sediment aggradation at 2 1 m myr 1 during the last 250 000 yr similarly the adjacent low terrace sediments contain tcn concentration profiles consistent with aggradation of 2 0 m myr 1 over a period of 250 000 750 000 yr prior to the last 250 000 yr of stability in summary depth profiles of two tcns provide constraints on the rates of sediment deposition sources of sediment and transport history as well as the subsequent exposure conditions of the sediment following deposition our results are consistent with early quaternary initiation of hyperaridity for the region during the quaternary winter precipitation events experienced at our sites latitude 241s drive active erosion deposition cycles the northward migration of the subtropical front during quaternary glacial cycles may have enhanced precipitation at 241s leading to more active fluvial processes during cooler periods

calculated rates of cosmic ray muon produced ne in subsurface quartz 1 interactions of cosmic ray secondaries with subsurface rocks produce both stable 3he 21ne 22ne and radioactive 10be 26al and 36cl cosmogenic nuclides as the production rates by muons of 21ne and 22ne in quartz are not known these can be estimated from published cross sections of analogous reactions separately for fast and slow muon reactions our calculations show that subsurface 21ne is affected mainly by fast muon interactions p f21ne 0 39 0 15 at g 1a 1 vs p 21ne 0 12 0 03 at g 1a 1 sea level high latitude we also infer that the resulting production rate ratio p21ne p10be of 21ne and 10be changes with depth below the earth s surface this ratio in turn may provide supplemental erosion rate information in geological settings of varying erosion surface covers and for long time scales when radionuclide data provide incomplete information in environments with very low erosion rates our calculations indicate noticeable differences in the production ratios p21ne p10be specifically for long time scales however calibrations are needed and may be carried out on a well documented quartz core

cosmogenic noble gas studies in the oldest landscape on earth surface exposure ages of the dry valleys antarctica extraordinarily high surface exposure ages have been determined for sirius group tillites of mt fleming and mt feather as well as at localities in the inner dry valleys using cosmogenic helium and neon ages of 10 ma at mt fleming 5 3 ma at mt feather and 6 5 ma at insel mountain are among the highest nominal exposure ages published so far these values are minimal ages as they are based on the assumption of zero erosion and uplift the mt feather sample independently confirms the pre pliocene age of the sirius group sediments in the dry valleys as previously determined at mt fleming the insel mountain samples provide evidence for a landscape formation of the inner dry valleys not later than late miocene time assuming conservatively low values of 2 5 cm ma 1 for erosion rate and 50 m ma 1 for uplift rate we infer that the sirius group tillites at mt fleming were deposited earlier than 20 ma ago this indicates that the overriding of the dry valleys block of the transantarctic mountains by the east antarctic ice sheet occurred not later than the early miocene maximum long term erosion rates in the inner dry valleys must be 15 cm ma 1 down to altitudes 1000 m since such low erosion rates require permanently cold and hyperarid conditions the response of antarctica to the pliocene warm climatic episode must have been small cosmogenic nuclide data from both the inner dry valleys and the sirius group sediment localities support the hypothesis of a stable east antarctic ice sheet since at least late miocene time implying that the climate of antarctica was decoupled from that of lower southern latitudes we present also new elemental 21ne production rates of p21 mg 196 atoms g 1 yr 1 and p21 al 55 atoms g 1 yr 1 at sea level and high geomagnetic latitude these figures are consistent with a 3he production rate of p3 110 atoms g 1 yr 1 similar to previously published values this consistency provides evidence that pyroxene is retentive for both helium and neon over at least 10 ma cosmogenic ne in quartz and pyroxene has a 22ne 21ne cos ratio of 1 266 0 040 and 1 159 0 040 respectively

geomorphology on geologic timescales evolution of the late cenozoic pacific paleosurface in northern chile and southern peru abstract the atacama desert on the western margin of the central andes is one of the driest and oldest deserts in the world it is defined by a distinct and ancient surface known as the pacific paleosurface pps or atacama paleosurface the age of this surface is determined as the time at which sediment deposition ceased and the surface was effectively abandoned early studies suggested that this abandonment took place between 14 and 10 ma and was related to both the uplift of the andes and the onset of hyperaridity in the region here we provide a regional re examination of the pps compiling existing work on the underlying geology sedimentology surface exposure dating and seismic profiling we also present new multispectral satellite maps of the pps and 45 new cosmogenic 3he and 21ne surface exposure ages in order to constrain the formation age and the preservation and incision history of the paleosurface we conclude that the pps is not a single paleosurface but instead is a mosaic of smaller surfaces that were formed by aggradational and degradational processes over 19 million years or more and should be termed collectively as the pacific paleosurfaces the time at which individual paleosurfaces formed is related to regional climate where the location of each is controlled by regional tectonic activity cosmogenic surface exposure ages suggest that the surfaces are a record of regional scale climate events

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

multiple cosmogenic nuclides document the stability of the east antarctic ice sheet in northern victoria land since the late miocene 5 7 ma the timing and amplitude of changes in the antarctic ice level are relevant to understanding past climate fluctuations and ongoing changes in the global climate and sea levels in this study we present surface exposure ages based on in situ produced cosmogenic 10be and 21ne in the bedrock samples of glacially eroded relict surfaces from the deep freeze range northern victoria land the proximity of this region to the east antarctic ice sheet indicates that the area is sensitive to variations in inland ice volume permitting the investigation of the behavioural relationship between the east antarctic ice sheet and the alpine glacial system in northern victoria land dating erosional surfaces provides a precise chronology of northern victoria land paleoclimate evolution and allows us to correlate the east antarctic ice sheet response to global climate events and local ice level variations the 10be and 21ne concentrations from the highest peaks of the deep freeze range strongly indicate that the relict landscape features were continuously exposed for 5 7 ma denudation rates inferred from our data show that the erosion rate of the summits has been extremely low 5 cm ma for at least 5 7 ma along with evidence of persistent climate stability cold and arid conditions from other sectors of the transantarctic mountains our results indicate that the transition from the wet based to the cold based glacial regime in northern victoria land occurred after the creation of the polar east antarctic ice sheet in the middle miocene

cosmogenic 3he production rate in ilmenite and the redistribution of spallation 3he in fine grained minerals cosmogenic nuclide surface exposure dating and erosion rate measurements in basaltic landscapes rely primarily on measurement of 3he in olivine or pyroxene however geochemical investigations using 3he have been impossible in the substantial fraction of basalts that lack separable olivine or pyroxene crystals or where such crystals were present but have been chemically weathered fine textured basalts often contain small grains of ilmenite a weathering resistant mineral that is a target for cosmogenic 3he production with good he retention and straightforward mineral separation but with a poorly constrained production rate here we empirically calibrate the cosmogenic 3he production rate in ilmenite by measuring 3he concentrations in basalts with fine grained 20 m cross section ilmenite and co existing pyroxene or olivine from the columbia river and snake river plain basalt provinces in the western united states the concentration ratio of ilmenite to pyroxene and olivine is 0 78 0 02 yielding an apparent cosmogenic 3he production rate of 93 6 7 7 atom g 1 yr 1 that is 20 30 greater than expected from prior theoretical and empirical estimates for compositionally similar minerals the production rate discrepancy arises from the high energy with which cosmic ray spallation reactions emit tritium and 3he and the associated long stopping distances that cause them to redistribute within a rock fine grained phases with low cosmogenic 3he production rates like ilmenite will have anomalously high production rates owing to net implantation of 3he from the surrounding higher 3he production rate matrix semi quantitative modeling indicates implantation of spallation 3he increases with decreasing ilmenite grain size leading to production rates that exceed those in a large grain by 10 when grain radii are 150 m the modeling predicts that for the ilmenite grain size in our samples implantation causes production rates to be 20 greater than expected for a large grain and within uncertainty resolves the discrepancy between our calibrated production rate theory and rates from previous work the redistribution effect is maximized when the host rock and crystals differ substantially in mean atomic number as they do between whole rock basalt and ilmenite

long term low latitude cosmogenic 3he production rate determined from a 126 ka basalt from fogo cape verdes an ankaramite lava from fogo cape verdes has been used to determine the long term cosmogenic 3he 3hecos production rate at low latitude 14 9 n 40ar 39ar incremental heating yield an eruption age of 125 8 7 ka cosmogenic 3he abundances yield local production rates of 75 6 7 0 atoms g year in olivine 1 n 10 and 70 1 2 9 atoms g yr in pyroxene 1 n 11 the lower 3hecos production rate in pyroxene is consistent with compositional control on production when scaled to sea level high latitude using available algorithms the olivine 3hecos production rate ranges from 86 109 atoms g yr these values overlap the long term production rate determined at the canary islands 99 atoms g yr they are however lower than previously reported long term production rates from hawaii and southern south america 129 152 atoms g yr and the range of 20 ka calibration sites 110 130 atoms g yr erosion burial and high atmospheric pressure appear to be of negligible importance the likeliest explanation is that the geomagnetic field strength was higher in the past the agreement between the fogo geomagnetic field strength corrected production rate scaled using various published scaling algorithms suggests that differences in incorporation of the non dipole component of the earth magnetic field in the scaling algorithms are negligible for long term production rate determinations at low elevation and low latitude longitudinal variation in long term cosmogenic nuclide production rates between the central atlantic ocean and the americas hawaii and patagonia may exist this has implications for exposure dating of old surfaces it will require that locally determined production rates should be used where available and that scaling schemes incorporating longitudinal variations should be used if nearby calibration sites are not available furthermore if long term longitudinal production rate variations exist it implies that variation in the geomagnetic field may not average out after around 20 ka but may require significantly longer periods up to 100 ka

miocene to pleistocene glacial history of west antarctica inferred from nunatak geomorphology and cosmogenic nuclide measurements on bedrock surfaces we report geomorphic observations and cosmogenic nuclide measurements on bedrock surfaces from three isolated nunatak groups in west antarctica the pirrit hills and nash hills located in the weddell sea sector and the whitmore mountains located on the ross weddell divide the objectives of this paper are to i establish a chronology for landscape development at these sites and ii quantify the long term history of ice thickness variations in west antarctica these nunataks display relic alpine landscapes on which weathered bedrock surfaces are superimposed in the pirrit hills an erosional trimline is etched into alpine ridges and separates smooth crested ridges below from serrated ridges above below the trimline geomorphic evidence indicates repeated frozen based ice cover while above the trimline evidence for ice cover is entirely absent there is also no geomorphic evidence for thicker than present ice at the whitmore mountains cosmogenic nuclide concentrations in the oldest bedrock surfaces from the whitmore mountains and from above the pirrit hills trimline indicate uninterrupted exposure for 12 myr at extraordinarily low erosion rates this places a lower limit on the timing of the formation of alpine landscapes in west antarctica and we hypothesize that this occurred during the relatively warm climates prior to the mid miocene cooling the absence of evidence for thicker ice at the whitmore mountains is consistent with the hypothesis that the divide was typically thinner than present during pleistocene glacial periods due to reduced accumulation bedrock surfaces below the trimline have much lower nuclide concentrations and are most easily explained by a scenario of repeated frozen based ice cover and occasional subglacial plucking which is consistent with geomorphic observations bedrock surfaces near the modern ice level appear to have been covered more than half of the time while higher elevation surfaces indicate progressively less cover the trimline and associated geomorphic features are very similar to a prominent trimline in the ellsworth mountains and we conclude that these are in fact part of the same feature the ellsworth trimline is hypothesized to have formed during the mid miocene cooling and the transition from alpine to continental glaciation and our results are consistent with this hypothesis

21ne versus 10be and 26al exposure ages of fluvial terraces the influence of crustal ne in quartz abstract the accuracy of 21 ne surface exposure ages depends critically on the correction for a trapped ne component commonly the amount of cosmogenic ne used to calculate 21 ne exposure ages is considered to be the ne excess relative to a trapped component of atmospheric composition 21 ne 20 ne 0 00296 here we document a trapped ne component in quartz samples from a series of river terraces at the northern margin of tibet hetzel et al nature 417 2002 428 432 which has a non atmospheric 21 ne 20 ne ratio varying from 0 00299 to 0 00398 vacuum crushing of amalgamated samples each derived from 30 80 quartz clasts revealed that the non atmospheric trapped component is present in fluid inclusions it has probably been incorporated into the quartz crystals during their growth in veins at low grade metamorphic conditions only if the amount of cosmogenic 21 ne is determined relative to this trapped component are the calculated 21 ne exposure ages consistent with the relative ages of the tectonically induced terraces and in agreement with independent 10 be and 26 al exposure ages of the fluvial terraces a significant in situ production of nucleogenic 21 ne by the reaction 18 o n 21 ne in the paleozoic quartz minerals is ruled out by extremely low u contents of the order of 1 5 ppb all ages have been corrected for an inherited cosmogenic component that results from cosmic ray exposure during erosion of the host rock and transport of the clasts to the terraces the origin of the trapped component from crustal fluids is supported by high 40 ar 36 ar ratios of 2000 6000 and slightly elevated 136 xe 132 xe ratios relative to air which can be explained by radioactive decay of 40 k and spontaneous fission of u in the crust

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

detrital cosmogenic 21ne records decoupling of source to sink signals by sediment storage and recycling in miocene to present rivers of the great plains nebraska usa the preservation of conglomerates far from mountainous sources is commonly interpreted in terms of tectonic or climatic forcing to relate a depositional signal to changing conditions in source areas the process and duration of sediment routing from source to sink need to be determined for the first time we quantified sediment transport histories using cosmogenic 21ne in quartzite pebbles from modern river gravels and neogene conglomerates from the modern and ancient north platte river of the great plains of nebraska united states we demonstrate that at 400 km distance from the front ranges of the rocky mountains the majority of pebbles were stored in older channel deposits for up to several millions of years before being recycled this was enabled by very slow to zero basin subsidence rates this implies that upstream tectonic or climatic controls on surface processes were decoupled from the downstream depositional record a result supported by the similarities in cosmogenic 21ne values among miocene pliocene and modern river channel pebbles despite known changes in tectonic and climatic forcing

enhanced erosion rates on mars during amazonian glaciation abstract observations of mars from the surface and from orbit suggest that erosion rates over the last 3 gyr the amazonian have been as slow as 10 5 m myr and have been dominated by aeolian processes while ancient noachian erosion rates may have been orders of magnitude higher due to impact bombardment and fluvial activity amazonian aged glacial deposits are widespread on mars but rates of erosion responsible for contributing debris to these remnant glacial deposits have not been constrained here we calculate erosion rates during amazonian glaciations using a catalog of mid latitude glacial landforms coupled with observational and theoretical constraints on the duration of glaciation these calculations suggest that erosion rates for scarps that contributed debris to glacial landforms are 4 7 orders of magnitude higher than average amazonian rates in non glaciated low slope regions these erosion rates are similar to terrestrial cold based glacier erosion and entrainment rates consistent with cold based glacier modification of parts of mars

geochemical methods to infer landscape response to quaternary climate change and land use in depositional archives a review abstract understanding and quantifying the processes and geochemical cycles associated with catchment erosion the development of soils and weathering horizons and terrestrial habitat change beyond the scales of modern observations remain challenging such research however has become increasingly important to help predict future landscape change in light of increasing land use and rapid global warming we herein review organic and inorganic geochemical tools applied to depositional archives to better understand various aspects of landscape evolution on geological time scales we highlight the potentials and limitations of inorganic geochemical analytical methods such as major element geochemistry metal and radiogenic isotopes and in situ cosmogenic nuclides as qualitative semi quantitative and quantitative proxies for the transformation of bedrock material via regolith and soils to sediments we also show how stable isotope geochemistry applied to lacustrine endogenic carbonates can be used to infer rock water interactions vegetation change and soil development in limestone rich catchments proxies focusing on the silicilastic element of sediment formation transport and deposition are ideally combined with organic geochemical proxies for vegetation change and soil organic matter evolution in a catchment to gain a comprehensive picture of the critical zone s evolution over time multi proxy and multidisciplinary research combining organic and inorganic geochemical techniques from several sedimentary archives in the same catchment have high potential to provide comprehensive information on quaternary landscape evolution and thus improve the robustness of associated forecasting models

cosmogenic and nucleogenic 3he in apatite titanite and zircon cosmogenic 3he was measured in apatite titanite and zircon and cosmogenic 21 ne in quartz at 13 depth intervals in a 2 7 m long drill core in a miocene ignimbrite from the altiplano of bolivia all three 3he depth profiles as well as the 21 ne profile attenuate exponentially with depth indicating that both of these isotopes are cosmogenic in origin with no significant contribution from other sources the attenuation lengthscale for 3he production of 180 11 g cm 2 is consistent with expectations for neutron spallation and is identical to that found for the cosmogenic 21 ne in quartz by normalizing the measured 3he concentrations to 21 ne and using the independently known cosmogenic 21 ne production rate the apparent cosmogenic 3he production rates in apatite titanite and zircon were respectively found to be 112 97 and 87 atoms g yr at sea level and high latitude the formal uncertainty on these estimates is 20 2 and arises in equal parts from uncertainties in the measured 3he 21 ne ratios and the uncertainty in the 21 ne production rate however an additional factor affecting the apparent 3he production rate in these phases arises from the long stopping range of spalled 3he and tritium which decays to 3he because all three accessory phases have higher mean atomic number than major rock forming minerals they will have lower 3he production rates than their surroundings as a consequence the long stopping ranges will cause a net implantation of 3he and therefore higher apparent production rates than would apply for purely in situ production thus these apparent production rates apply only to the specific grain sizes analyzed analysis of sieved zircon aliquots suggests that a factor of 2 increase in grain size from 50 to 100 m cross section yields a 10 decrease in apparent production rate while this effect warrants further study the grain sizes analyzed here are typical of the accessory phases commonly encountered so the apparent rates provide an appropriate starting place for surface exposure dating using 3he in these minerals

constraints on age erosion and uplift of neogene glacial deposits in the transantarctic mountains determined from in situ cosmogenic 10be and 26al 10 be and 26 al data from sandstone boulders in three neogene glacial deposits in the mcmurdo sound dry valleys region of southern victoria land antarctica indicate minimum exposure ages of approx 3 ma and maximum long term erosion rates of approx 5 12 cm m y supporting the suggestion that polar desert conditions have persisted in the dry valleys since at least late pliocene time variation of cosmogenic nuclide production rate with altitude also allows constraints on past uplift rates model calculations employing 10 be data indicate little or no uplift in the dry valleys region in the past 3 m y precluding rapid 1 km m y late pliocene uplift previously suggested for some parts of the transantarctic mountains

mass spectrometric identification of cosmic ray produced neon in terrestrial rocks with multiple neon components studies of cosmic ray produced nuclides in terrestrial rocks are expected to provide important geomorphological and glaciological information such as surface exposure ages erosion rates and extent of glacial cover in the case of the stable nuclide21ne the cosmic ray produced component may represent but one of several components and a component resolution based on three isotope correlations is essential we developed analytical techniques which permit accurate corrections for all interfering ions we show for our modified nier source that corrections for doubly charged species based on constant charge state ratios are not satisfactory the improved techniques permit isotopic studies of 106 atoms of21ne the spallation ratio 22ne 21ne c from si was calibrated using a quartz separate from an allan hills sandstone and yields a value of1 243 0 022 this ratio is expected to be essentially constant for terrestrial quartz samples and should be useful in component resolutions the stepwise release of ne at increasing temperatures shows that cosmic ray produced ne is released from quartz at rather low temperatures this permits an estimate of the activation energy for ne diffusion in quartz 90 10 kj mol