grain size dependent concentration of cosmogenic 10be and erosion dynamics in a landslide dominated himalayan watershed for documenting recent or late quaternary erosion rates at the scale of a small watershed or even an entire mountain range the use of in situ terrestrial cosmogenic nuclides tcn such as 10be in river sediments has become widespread over the last decade in mountainous settings however landslides may induce a two fold complication in the cosmogenic nuclide budget first they may episodically deliver large amounts of sediment with low tcn concentrations to the river channel second they may generate a grain size concentration dependence in these sediments however studies that have explored grain size dependence in landslide dominated areas have reached differing conclusions and the underlying mechanisms remain poorly understood the present study focuses on the khudi khola river basin a small drainage basin in the central himalayas the area is characterized by steep slopes heavy rainfall and high sediment production rates importantly the watershed contains a large area of active landsliding in situ 10be was analyzed in sediments of grain sizes ranging from 75 m to 4 cm collected from five locations upstream downstream and in the small tributaries which drain the landslides in all sampling locations including those situated upstream of the landslides the finest grains 75 250 m are two to four times more concentrated in 10be than the largest clasts 4 7 mm we developed a numerical slope model which includes a low level of background soil erosion and episodic denudation from large mass wasting events we then introduced a coarsening of average grain size with soil depth to the model our simulation shows that the data available for this valley are compatible with a scenario in which landslides deliver coarse grains to the channel that are less concentrated in tcn and have deeper provenance best fit estimates of the model parameters suggest recurrence times of 3000 to 9000 years for a major landslide on the same slope and mean long term landslide denudation rates of 1 7 to 4 7 mm yr 1 a negative correlation between tcn concentration and grain size is also observed directly upstream and 5 km downstream of the landsliding area suggesting that nearly all of the sediment carried by the river is derived from ancient landslides while almost no sediment is supplied by erosion of soil mantled slopes despite these complications apparent denudation rates directly derived from the tcn concentrations and from previously published data in the region are all on the same order of magnitude around 2 mm yr 1 however a factor of three variability remains between the different studies depending on the location the year of sampling and the analyzed grain size fraction thus although tcn derived average denudation rates provide a useful first order estimate even in fast eroding terrains dominated by landslides caution should be applied when using quantitative results in such settings

african laterite dynamics using in situ produced 10be abstract we have investigated the development of iron crust lateritic systems and rain forest soils in tropical environments using in situ produced 10be in quartz veins and cobbles the variability of its concentration as function of subsurface depth in soil profile provides criteria for distinguishing between allochthonous elsewhere formation and autochthonous in situ formation processes and hence for determining whether colluvial transport or in situ chemical weathering dominates soil development in these environments in the stable west african craton in southwest burkina faso at larafella the exponential decrease in 10be concentration observed along a quartz vein from the lowland lateritic system corresponds to the decrease in its production rate associated with attenuation of cosmic rays and thus indicates an autochthonous development models of the 10be depth profile in this unit suggest that this surface has been subject to erosion at a mean rate of 2 m my 1 and that 1 5 of the surface 10be production rate is associated with muon induced reactions in a contrasting environment tropical rain forest malemba congo 10be concentrations have been measured in quartz vein and in round and angular quartz cobbles incorporated in a downslope stone line comparison with data from larafella suggests that the angular cobbles have been transported a few meters from the quartz veins by downslope lateral creeping whereas the round cobbles have an allochthonous origin models of 10be distributions as this site yield an erosion rate of 12 m my 1 and a rate of lateral creeping on the order of 60 m my 1

transient sediment supply in a high altitude alpine environment evidenced through a 10be budget of the etages catchment french western alps although beryllium 10 10be concentrations in stream sediments provide useful synoptic views of catchment wide erosion rates little is known on the relative contributions of different sediment supply mechanisms to the acquisition of their initial signature in the headwaters here we address this issue by conducting a 10be budget of detrital materials that characterize the morphogenetic domains representative of high altitude environments of the european alps we focus on the etages catchment located in the ecrins pelvoux massif southeast france and illustrate how in situ 10be concentrations can be used for tracing the origin of the sand fraction from the bedload in the trunk stream the landscape of the etages catchment is characterized by a geomorphic transient state high topographic gradients and a large variety of modern geomorphic domains ranging from glacial environments to scarcely vegetated alluvial plains beryllium 10 concentrations measured in the etages catchment vary from similar to 1 x 104 to 4 5 x 105 atoms per gram quartz while displaying consistent 10be signatures within each representative morphogenetic unit we show that the basic requirements for inferring catchment wide denudation from 10be concentration measurements are not satisfied in this small dynamic catchment however the distinct 10be signature observed for the geomorphic domains can be used as a tracer we suggest that a terrestrial cosmogenic nuclide tcn budget approach provides a valuable tool for the tracing of material origin in basins where the let nature do the averaging principles may be violated

evidence for muon induced production of 10be in near surface rocks from the congo distributions of 10be in vein quartz from a lateritic weathering profile from the congo provide evidence for significant in situ production of 10be by reactions other than neutron induced spallation after consideration of geomorphological and nuclear processes which might contribute to the observed depth variability we conclude that cosmic ray muon induced reactions are the most likely mechanism and that such reactions lead to 1 to 3 of 10be production at the surface this small muon induced component has only minor implications for the use of 10be for quantification of exposure histories of surficial rocks nevertheless the muogenic component has the potential to expand the utility of cosmogenic nuclides in examination of surficial processes overcoming some of the limitations associated with the use of the neutron produced component

the role of ocean atmosphere reorganizations in glacial cycles abstract a case is made that glacial to interglacial transitions involve major reorganizations of the ocean atmosphere system such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere only in this way can the rapidity of glacial terminations the hemispheric synchroneity and symmetry of mountain glaciation and the large polar air temperature and dustiness variations be accounted for if these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean s salinity distribution

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

plateau reduction by drainage divide migration in the eastern cordillera of colombia defined by morphometry and 10be terrestrial cosmogenic nuclides catchment wide erosion rates were defined using 10be terrestrial cosmogenic nuclides for the eastern cordillera of the colombian andes to help determine the nature of drainage development and landscape evolution the eastern cordillera characterized by a smooth axial plateau bordered by steep flanks has a mean erosion rate of 11 1 mm ka across the plateau and 70 10 mm ka on its flanks with local high rates of 400 mm ka the erosional contrast between the plateau and its flanks was produced by the increase in the orogen regional slope derived from the progressive shortening and thickening of the eastern cordillera the erosion rates together with digital topographic analysis show that the drainage network is dynamic and confirms the view that drainage divides in the eastern cordillera are migrating towards the interior of the mountain belt resulting in progressive drainage reorganization from longitudinal to transverse dominated rivers and areal reduction of the sabana de bogota plateau this article is protected by copyright all rights reserved

cirques have growth spurts during deglacial and interglacial periods evidence from 10be and 26al nuclide inventories in the central and eastern pyrenees cirques are emblematic landforms of alpine landscapes the statistical distribution of cirque floor elevations is used to infer glacial equilibrium line altitude and the age of their frontal moraines for reconstructing glacial chronologies very few studies however have sought to measure cirque floor and supraglacial ridgetop bedrock downwearing rates in order to confront these denudation estimates with theoretical models of quaternary mountain landscape evolution here we use 10 be nuclide samples n 36 from moraines bedrock steps and supraglacial ridgetops among a population of cirques in the east central pyrenees in order to quantify denudation in the landscape and detect whether the mountain topography bears any relevance to the glacial buzzsaw hypothesis minimum exposure ages meas obtained for a succession of moraines spanning the oldest dryas to the holocene produced a deglaciation chronology for three different pyrenean ranges maladeta bassies and carlit based on a series of corrections calibrations and chronostratigraphic tuning procedures meas on ice polished bedrock exposures were further used to model denudation depths at nested timescales during the wurm the younger dryas and the holocene results show that subglacial cirque floor denudation was lower during glacial periods wurm 10 mm ka than during deglacial and interglacial periods tens to hundreds of mm ka the relative inefficiency of glacial denudation in the cirque zone during the wurm would have resulted from i cold based and or ii low gradient glaciers situated in the upper reaches of the icefield and or from iii glacier load starvation because of arrested clast supply from supraglacial rockslopes situated in the permafrost zone denudation peaked during the younger dryas and holocene glacial advances a time when cirque glaciers became steeper warmer based and when frost cracking weakened supraglacial ridgetops thus enhancing sub glacial erosion by providing debris to the sliding glacier base cirques therefore grow faster during more temperate periods of cirque glaciation than under full glacial conditions another key finding was the very low rates of ridgetop lowering averaged over the wurm and holocene 10 25 mm ka a comparison of the denudation rates obtained from the cirque zone with regional estimates of crustal uplift indicates that the alpine topography is not in a steady state the low intensity of glacial denudation failed to bring the topography to a buzzsaw equilibrium state

estimation of thermal conductivity of rocks from their mineralogical composition asturian coal basin nw spain for modelling purposes the carboniferous coal basin ccb in nw spain has been extensively mined for a long time at present abandoned and flooded mines constitute mining reservoirs which act as storage facilities containing mine water susceptible to being exploited as a geothermal resource to supply heating and cooling using heat pumps the development of numerical models capable of predicting the geothermal behaviour of the reservoir after a certain number of years of use can be useful and applicable to this and other sedimentary mining basins a procedure for predicting in situ thermal conductivity k profiles using lithological and mineralogical information for modelling purposes was applied to a mining reservoir in the ccb first all the involved geological units were sampled in unaltered outcrops assuming that weathering have not significantly biased thermal properties the matrix thermal conductivity of each sample was estimated from the thermal conductivities of the respective mineralogical components whose proportion were determined by optical microscopy a final k was acquired considering the effects of porosity temperature and mineralogical composition of the rock matrix and assuming water as the pore filling fluid finally the obtained parameters were extended to the deep geological profile affected by the mining works values ranging from 1 42 w m 1 k 1 lutite to 4 89 w m 1 k 1 sublitarenite were found in the studied reservoir average of 2 86 w m 1 k 1

the deglaciation of eastern scotland cosmogenic 10be evidence for a lateglacial stillstand cosmogenic nuclide analysis using 10be has been used to date a lateglacial stillstand in the eastern highlands of scotland at 16 6 13 6 kyr bp the dates constrain the extent of the local cairngorm ice cap and the larger scottish ice sheet at a particular stage during deglaciation the geomorphological and sedimentological evidence suggests that the glacial stillstand persisted for around 1 kyr independent 14c dating from loch etteridge within strathspey shows that deglaciation proceeded rapidly after ca 15 kyr bp critically this study demonstrates that glaciers last occupied the valleys of the cairngorms immediately prior to the lateglacial interstadial bolling allerod contrary to previous assumptions that the last large scale glaciation of the massif took place in the loch lomond stadial younger dryas this later event in the cairngorms was therefore confined to the high corries

cosmogenic nuclide exposure ages and glacial history of late quaternary ross sea drift in mcmurdo sound antarctica 3he 10be and26al surface exposure ages were determined for rock samples from late quaternary drift sheets deposited on the coast of mcmurdo sound antarctica by the ross sea ice sheet the youngest drift previously believed to be late wisconsin in age has exposure ages of 8 106 kyr 19 samples these results suggest that the apparent late wisconsin ice margin may represent a number of ice sheet advances during the last glacial period 3he exposure ages from analogous stratigraphically older drift range from 104 to 567 kyr seven samples and clearly distinguish the youngest drift from older deposits comparison of10be and3he concentrations in ross sea drift quartz samples indicates significant3he loss in only one sample suggesting that cosmogenic3he is generally retained in young antarctic quartz samples exposure age 100 kyr of appropriate grain size in two of the five quartz samples analyzed significant excesses of26al relative to10be preclude meaningful26al exposure age calculations these excesses may be due to nucleogenic26al produced as a byproduct of uranium and thorium decay

linking morphology across the glaciofluvial interface a 10be supported chronology of glacier advances and terrace formation in the garonne river northern pyrenees france abstract the garonne river drains an important part of the northern pyrenees and its northern foreland we investigated the middle reaches of the garonne river establishing a detailed morphogenetic profile of its foreland terrace staircase and the preserved palaeoglacier margins we particularly focussed on the glaciofluvial interface linking also genetically the fluvial sediment archives in the foreland with the terminal glacial basin upstream of the pyrenees mountain front using cosmogenic nuclide 10be analyses two terrace exposures have been dated including a prominent fluvioglacial outwash fan at the foreland transition we identified three terminal margins of late pleistocene glacier advances the prominent garonne staircase consists of three major terrace complexes comprising eight individual terrace levels results indicate a young age of the lower terrace complex of the garonne staircase mis 4 2 the morphogenetic relationships and the new 10be exposure age constraints suggest that during the last glaciation wurmian the garonne glacier reached its maximum extent at the north pyrenean mountain front apparently already during mis 4 two different ice margins were associated with mis 2 indicating close to maximum ice extent during early mis 2 lgm and relatively stationary ice recession in the late mis 2 the extensive garonne terrace complexes formed under cold climate conditions and were abandoned by incision during major glacial interglacial transitions during warm cold climate transitions lateral erosion caused the reworking of previously abandoned palaeofloodplains the long term quaternary incision of the garonne and other north pyrenean rivers indicates that the proximal aquitaine foreland basin experienced uplift however non uniform lateral course migrations and valley asymmetries of the north pyrenean piedmont rivers indicate that uplift magnitude is variable with maximum amounts in the centre of the molasse fan of lannemezan rivers on the western part of the fan were tilted toward the west whereas rivers in the eastern part like the garonne were tilted to the east

active transpressional tectonics in the andean forearc of southern peru quantified by 10be surface exposure dating of an active fault scarp our understanding of the style and rate of quaternary tectonic deformation in the forearc of the central andes is hampered by a lack of field observations and constraints on neotectonic structures here we present a detailed analysis of the purgatorio fault a recently recognized active fault located in the forearc of southern peru based on field and remote sensing analysis pleiades dem we define the purgatorio fault as a subvertical structure trending nw se to w e along its 60km length connecting on its eastern end to the crustal incapuquio fault system the purgatorio fault accommodates right lateral transpressional deformation as shown by the numerous lateral and vertical plurimetric offsets recorded along strike in particular scarp with a 5m cumulative throw is preserved and displays cobbles that are cut and covered by slickensides cosmogenic radionuclide exposure dating be 10 of quartzite cobbles along the vertical fault scarp yields young exposure ages that can be bracketed between 0 to 6ka depending on the inheritance model that is applied our preferred scenario which takes in account our geomorphic observations implies at least two distinct rupture events each associated with similar to 3 and similar to 2m of vertical offset these two events plausibly occurred during the last thousand years nevertheless an interpretation invoking more tectonic events along the fault cannot be ruled out this work affirms crustal deformation along active faults in the andean forearc of southern peru during the last thousand years

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

diffusion of cosmogenic3he in olivine and quartz implications for surface exposure dating abstract thein situ production of3he in surface rocks by cosmic ray induced nuclear reactions offers an important geochronological tool to evaluate helium loss problems in this technique cosmogenic3he diffusivities were measured in quartz and olivine by incremental heating at 150 600 c arrhenius temperature dependences were observed in both minerals with similar activation energies ea 25 4 kcal mole logd0 3 7 0 9 in olivine andea 25 2 0 9 logd0 0 2 0 4 in quartz and imply very low diffusivities when extrapolated to environmental temperatures less than 10 18 cm2 s in quartz and 10 22 cm2 s in olivine at 20 c these low diffusivities suggest helium loss will not significantly affect cosmogenic helium exposure dating for time scales on the order of 106 years in quartz and 109 years in olivine provided large 2 mm sample grains are used exposure ages obtained with smaller grains need to be corrected for diffusive helium loss and equations are provided for this purpose cosmogenic3he diffuses more than 100 times faster than trapped magmatic3he in olivine or radiogenic4he in quartz the mechanisms responsible for these differences have yet to be determined but may involve both trapping processes at mineral defects and enhanced mobility associated with spallation produced crystal damage therefore it is possible that helium diffusivities may depend on a sample s cosmic ray exposure or radiogenic production history whatever the precise mechanism the higher mobility of3he suggests that incremental heating will be useful in separating cosmogenic helium from magmatic or radiogenic helium in future studies comparison of the diffusivity results with total cosmogenic3he contents of different quartz size fractions for an antarctic quartzite suggests that he loss may have occurred more rapidly than predicted by the laboratory measurements nonetheless retention of cosmogenic3he is quite high equivalent to more than a million years of exposure and cosmogenic3he geochronology is feasible in this and other quartz containing rocks

the global average production rate of10be precipitation collected in continuously open containers for about a year at seven sites around the united states was analyzed for10be 90sr 210pb and238u based on these data and long term precipitation 90sr and210pb delivery patterns the stratospheric tropospheric and recycled10be components in the collections were estimated and the global10be production rate was assessed single station production rate estimates range from 0 52 106 atoms cm 2 yr 1 to 2 64 106 atoms cm 2 yr 1 the mean value is 1 21 106 atoms cm 2 yr 1 with a standard error of 0 26 106 atoms cm 2 yr 1

cosmogenic 3he in terrestrial rocks the summit lavas of maui we have identified terrestrial cosmic rayproduced 3he in three lava flows on the crest of haleakala volcano on maui 3 km above sea level and 0 5 million years old although these lavas like all oceanic basalts contain primordial 3he from the mantle the cosmogenic component 3hec can be identified unambiguously because it is extractable only by high temperature vacuum fusion in contrast a large fraction of the mantle helium resides in fluid inclusions and can be extracted by vacuum crushing leaving a residual component with 3he 4he ratios as high as 75 those in the atmosphere which can be liberated by melting the crushed grains cosmogenic 3he is present in both olivines and clinopyroxenes at 0 8 1 2 10 12 ml stp g and constitutes 75 5 of the total 3he present the observed 3hec levels require a cosmic ray exposure age of only some 64 000 years much less than the actual age of the lavas if there is no erosion using a model that includes effects of uplift or submergence as well as erosion we calculate an apparent erosion rate of the order of 8 5 m 106 years for the western rim of the summit crater as an example of the application of measurements of cosmogenic rare gases to terrestrial geological problems

application of in situ produced cosmogenic 10be and 26al to the study of lateritic soil development in tropical forest theory and examples from cameroon and gabon abstract depth profiles of in situ produced cosmogenic nuclides including 10 be t 1 2 1 5 10 6 years and 26 al t 1 2 0 73 10 6 years in the upper few meters of the earth s crust may be used to study surficial processes quantifying denudation and burial rates and elucidating mechanisms involved in landform evolution and soil formations in this paper we discuss the fundamentals of the method and apply it to two lateritic sequences located in african tropical forests

10be and 26al production rates deduced from an instantaneous event within the dendro calibration curve the landslide of kofels otz valley austria surface exposure dating requires the knowledge of cosmogenic nuclide production rates when determining time integrated production rates the exposure ages of the calibration samples need to be accurately known the landslide of kofels austria is very well suited for this purpose it is the largest landslide in the crystalline alps of austria dating back to 7800 100 years bc ams 14c dating of buried wood which is well within the 14c dendro calibration curve exposed quartz veins were sampled from the tops of large boulders from the toe of the landslide for analysis of 10be and 26al to calculate sea level high geomagnetic latitude 60 open sky radionuclide production rates corrections were applied for altitude and latitude for shielding by surrounding mountains for sample geometry vegetation and snow cover and for sample thickness the production rates for an exposure age of 10 000 years are 5 75 0 24 10be atoms yr g sio2 and 37 4 1 9 26al atoms yr g sio2 a 26al 10be ratio of 6 52 0 43 can be calculated the influence of the geomagnetic field on these production rates has been estimated using two different geomagnetic field records our production rates should be a good approximation for the use of surface exposure dating between about 5000 and 13 000 years bp

10be derived himalayan denudation rates and sediment budgets in the ganga basin abstract the himalayas represent the archetype of mountain building due to active continental collision and are considered in many studies as the locus of intense interactions between climate denudation and tectonics estimates of modern denudation rates across the entire range remain however relatively sparse in this study in situ produced cosmogenic 10 be concentrations were measured in detritic quartz in order to determine basin scale denudation rates for the central part of the himalayan range river sand was sampled over several years in the main trans himalayan rivers from the himalayan front to the ganga outlet in bangladesh the calculated 10 be denudation rates of the trans himalayan river basins range from 0 5 to 2 4 mm yr 1 average 1 3 mm yr 1 and vary by up to a factor of 3 between sampling years these denudation rates strongly contrast with the 0 007 mm yr 1 denudation rate of southern tributary basins draining the indian craton this work also shows that in the ganga basin no systematic evolution of average 10 be concentrations is observed during floodplain transfer implying that distal samples can be used to estimate the integrated denudation rate of the whole central himalayan range samples from the ganga in bangladesh display remarkably low variability in 10 be concentration implying an average himalayan denudation rate of 1 0 1 1 mm yr 1 however within the floodplain several samples suggest a recent perturbation of sediment transport dynamics with a recent increase in the relative sediment contribution from southern tributaries the himalayan sediment flux deduced from the 10 be denudation rate of the range is 610 230 mt yr 1 this flux is consistent within uncertainty with sediment fluxes derived from sediment gauging the similarity of the two flux estimates suggests that himalayan erosion fluxes have remained stable over the last centuries even if the large uncertainties associated with each method hamper more precise assessments

cosmogenic10be 26al and3he in olivine from maui lavas we report the presence of cosmogenic10be and26al in olivines from the maui haleakala basalts in which cosmogenic3he and21ne were discovered based on production rate calibrations in quartz crystals from late pleistocene granite exposures in the sierra nevada the haleakala crater erosion rates derived from10be and26al concentrations agree within 10 and give a mean rate of 12 m myr about 40 greater than the rate of 8 5 m myr previously derived from3he measurements these results establish the feasibility of the simultaneous use of radioactive and stable cosmogenic nuclides for studies of exposure ages and erosion rates in basaltic and andesitic terrains

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

timing of the last deglaciation in the sierra nevada of the merida andes venezuela abstract in the tropical merida andes northwestern venezuela glacial landforms were found at altitudes between 2600 and 5000 m corresponding to 600 km2 of ice cover during the maximum glacial extension however the lack of sufficient absolute age data prevents detailed reconstruction of the timing of the last deglaciation on the northwestern flank of the mucunuque massif successive moraines and striated eroded basement surfaces were sampled for cosmogenic 10be investigation their compilation with published data allows the establishment of a detailed chronology of the post lgm glacier history the oldest moraines 18 1 and 16 8 ka correspond to the oldest dryas successive moraine ridges indicate stops in the overall retreat between the lgm and the younger dryas the cold and short older dryas stadial has been identified results indicate that most of the ice withdrew during the pleistocene the dataset supports an intensification of the vertical retreat rate from 25 m ka during the late pleistocene to 310 m ka during the pleistocene holocene afterwards the glacier was confined and located in the higher altitude zones the altitude difference of the younger dryas moraines in the mucubaji la victoria and los zerpa valleys indicates a strong effect of valley orientation on the altitude of moraine development

growth of south rough ridge central otago new zealand using in situ cosmogenic isotopes and geomorphology to study an active blind reverse fault 1 in situ cosmogenic 10be and 26al measurements on sedimentary quartzites together with analysis of abandoned river terraces can be used to show how drainage responded to the lateral propagation of a late quaternary anticline forming above a blind reverse fault in central otago new zealand a close link between the progression of cosmogenic ages and the tectonic geomorphology allows us to confirm that uplift and propagation rates on the anticline are in the ranges 0 08 0 12 mm yr 1 and 0 8 1 5 mm yr 1 respectively over the last 550 000 years the agreement between the isotopic and geomorphological evidence in turn requires that minimum 10be exposure ages as great as 660 ka are not in steady state with respect to erosion this is a geochemical result of significance as it opens the possibility of a more regional analysis of landscape evolution in this region using the same rocks on an adjacent anticline thought to be even older on geomorphological arguments 10be concentrations give minimum exposure ages in the range 750 1400 ka these extremely old minimum ages are rare worldwide as they are usually limited to smaller values by erosion they are attributable to the very resistant nature of the quartz rich boulders in which the measurements were made which in places are shown to have erosion rates lower than 0 5 mm kyr 1

squeezing river catchments through tectonics shortening and erosion across the indus valley nw himalaya tectonic displacement of drainage divides and the consequent deformation of river networks during crustal shortening have been proposed for a number of mountain ranges but never tested in order to preserve crustal strain in surface topography surface displacements across thrust faults must be retained without being recovered by consequent erosion quantification of these competing processes and the implications for catchment topography have not previously been demonstrated here we use structural mapping combined with dating of terrace sediments to measure quaternary shortening across the indus river valley in ladakh nw himalaya we demonstrate 0 21 m k y 1 of horizontal displacement since ca 45 ka on the stok thrust in ladakh which defines the southwestern margin of the indus valley catchment and is the major back thrust to the tethyan himalaya in this region we use normalized river channel gradients of the tributaries that drain into the indus river to show that the lateral continuation of the stok thrust was active for at least 70 km along strike shortening rates combined with fault geometries yield vertical displacement rates that are compared to time equivalent erosion rates in the hanging wall derived from published detrital 10be analyses the results demonstrate that vertical displacement rates across the stok thrust were approximately twice that of the time equivalent erosion rates implying a net horizontal displacement of the surface topography and hence narrowing of the indus valley at 0 1 m k y 1 a fill terrace records debris flow emplacement linked to thrust activity resulting in damming of the valley and extensive lake development conglomerates beneath some of the modern alluvial fans indicate a northeastward shift of the indus river channel since ca 45 ka to its present course against the opposite side of the valley from the stok thrust the integration of structural topographic erosional and sedimentological data provides the first demonstration of the tectonic convergence of drainage divides in a mountain range and yields a model of the surface processes involved

microbial trace fossil formation biogenous and abiotic weathering in the antarctic cold desert in the antarctic cold desert ross desert the survival of the cryptoendolithic microorganisms that colonize the near surface layer of porous sandstone rocks depends on a precarious equilibrium of biological and geological factors an unfavorable shift of this equilibrium results in death and this may be followed by formation of trace fossils that preserve the characteristic iron leaching pattern caused by microbial activity similar microbial trace fossil may exist in the geological record if life ever arose on early mars similar processes may have occurred there and left recognizable traces

examination of surface exposure ages of antarctic moraines using in situ produced 10be and 26al concentrations of 10be t12 1 5 106 y and 26a1 t12 0 72 106 y have been determined by accelerator mass spectrometry ams in a suite of quartz samples taken from sandstone boulders in several moraines in arena valley a dry valley adjacent to the taylor glacier in the quatermain mountains southern victoria land east antarctica these isotopes are produced in surficial quartz by cosmic ray spallation of o and si the concentrations in these samples ranged from 6 1 105 to 3 0 107 at g 1 for 10be and from 9 4 106 to 1 2 108 at g 1 for 26a1 depending upon the extent of exposure at the surface analyses of 10be in several samples from a single moraine at altitudes ranging from 1300 to 1650 m permitted an estimation of the air attenuation pathlength of cosmic ray neutrons the value of 142 96 41 g cm 2 is consistent with other published values production rates of 17 6 4 at g 1 y 1 for 10be and 113 54 16 at g 1 y 1 for 26a1 at 1300 m and 87 s and a 26al 10be production ratio of 6 5 1 3 1 3 were calculated from the data these values correspond to sea level production rates at high geomagnetic latitude of 6 4 at g 1 y 1 and 41 7 at g 1 y 1 for 10be and 26a1 respectively consistent with determinations based on 11 ky glacially polished surfaces in the sierra nevada in california these production rates imply exposure ages for the various moraines ranging from 50 ky to 2 5 my in accordance with other geological evidence the 10be and 26al ages of these rocks compare favorably with those found using a similar dating method based on in situ production of 3he examination of the 3he concentrations in conjunction with the present data set yields an estimate of 3he production of 230 8540 at g 1 y 1 corresponding to 85 31 15 at g 1 y 1 at sea level this is lower than previously reported values of 240 60 at g 1 y 1 and 190 at g 1 y 1 scaled to sea level and high geomagnetic latitude based respectively on volcanic flows less than 2000 years old at low latitude and samples collected from 14 400 year old volcanic flows this discrepancy is likely due to diffusive losses which may become significant up to 50 for surface exposure ages on the order of 2 0 my nevertheless the general correlations among the three isotopes suggest that 3he does not suffer gross losses through diffusion

late cenozoic glacial history of the ross embayment antarctica abstract the ross ice drainage system comprises about 25 per cent of the surface area of the antarctic ice sheet its fluctuations during the late quaternary have been determined in two ways from analyses of three deep ice cores extracted at byrd west antarctica and at vostok and dome circe east antarctica and from the distribution stratigraphy and chronology of glacial drifts in the transantarctic mountains the ice core studies give time series records for the last 160 ka that correspond well with the marine isotope record and clearly show glacial interglacial stadial and interstadial intervals they also suggest that during glaciation maxima the polar plateau was characterised by an accumulation rate 50 per cent lower and temperature 7 9 c lower than present values glacial geological studies reveal a hiatus in the drift record between older miocene early pleistocene glacial sediments and drifts of the last two glaciations isotope stages 6 and 2 there are two leading but contradictory interpretations of the older drift sirius formation one is based primarily on biological data and favours partial deglaciation of antarctica in the pliocene early pleistocene followed by regrowth of the east antarctic ice sheet to dimensions larger than now and then substantial uplift of the transantarctic mountains the other is founded on glacial geological observations and implies a larger than present ice sheet over antarctica during the miocene and only 200 m of uplift subsequently for the late quaternary reconstructed ice surface profiles based on detailed mapping and dating of drift sheets show that large outlet glaciers from the east antarctic polar plateau became about 1000 m thicker during glaciation maxima while the plateau ice barely thickened at all this is attributed to extensive northward migration of the ice grounding line in the ross embayment as global sea level fell dates obtained from the drift sheets confirm that glaciers in the ross embayment area reached maximal limits at 190 160 ka bp and at 23 14 ka bp recession from the last glaciation maximum was underway by 13 ka bp and was complete by ca 6 ka bp alpine glaciers terminating in dry valleys fluctuate asynchronously with the ross embayment glaciers they retreat during glacial maxima when they become starved of accumulation and readvance during warmer intervals because of their dependence on grounding line position glacier fluctuations in much of antarctica are primarily led by sea level changes controlled by ice sheets in the northern hemisphere

late pleistocene holocene development of the tista megafan west bengal india 10 be cosmogenic and irsl age constraints abstract the himalayan proximal foreland is characterized by quaternary megafans of which the formational mechanisms remain debated the tista megafan spreads over more than 16 000 km2 from the mountain front where it is strongly incised to the confluence of the tista river with the jamuna brahmaputra river and stores sediments produced in the sikkim himalaya we propose a scenario for the late pleistocene holocene development of the tista megafan based on new 10be cosmogenic and infra red stimulated luminescence irsl age constraints and discuss the main potential controls on its evolution we suggest that two distal lobes developed successively downstream from a common proximal lobe deposition in the proximal lobe took place since at least 135 ka and incision began at 3 7 0 7 1 0 ka the western distal lobe of the megafan was deposited early in the history of the megafan when the sikkim himalaya catchment was drained by a tributary of the ganga river and was abandoned in the early holocene 10 11 ka the eastern recent

evidence for active retreat of a coastal cliff between 3 5 and 12 ka in cassis south east france this study on the cap canaille cliff n 43 19 e 5 55 cassis se france combines cosmic ray exposure cre dating using two cosmogenic nuclides in situ produced 10be and 36cl and morphological analyses to gain a better understanding of a major coastal cliff collapse event morphological analysis reveals evidence cliff morphology presence of big collapsed blocks of a possible major collapse of cap canaille in the past aerial pictures and gis software allow estimation of a potential collapsed volume of at least 7 106 m3 of which roughly 6 106 m3 fell into the mediterranean sea in situ produced 10be and 36cl concentrations were measured in samples collected on collapsed block surfaces and in situ produced 10be was measured along the cliff face to date the last major collapse event statistical analysis of the cre ages calculated from cliff samples shows that these ages cluster around 3 5 and 6 7 ka suggesting the existence of a two step past major collapse the older ages obtained at 9 and 12 ka coincides with the approach of present day sea level implying a control of sea level on the cliff retreat the cre ages calculated from collapsed block samples are more scattered toward younger ages due to several geomorphological factors the estimated collapsed volume associated with the last major collapse around 3 5 ka seems sufficient to have triggered a local tsunami in the cassis bay if it fell at once into the sea

dating geomorphologic surfaces using cosmogenic 3he cosmogenically produced 3he in rocks can be used to date geomorphologic surfaces using the late pleistocene bonneville flood event the subsequent development of the provo shoreline and associated volcanic rocks a production rate of 432 atoms g yr in olivine is determined for 38 56 n latitude present geomagnetic latitude 46 5 at 1445 m altitude integrated over the last 14 400 years measurements of cosmogenic helium in flood deposits on river scoured surfaces and lava flows show that it is possible to date directly large scale events such as volcanic eruptions and catastrophic floods olivine and pyroxene are both satisfactory minerals for cosmogenic dating by the 3he method however in most cases plagioclase and quartz are unsuitable because they do not quantitatively retain helium isotopes in their lattices

cosmic ray exposure dating with in situ produced cosmogenic 3he results from young hawaiian lava flows in an effort to determine the in situ production rate of spallation produced cosmogenic 3 he and evaluate its use as a surface exposure chronometer we have measured cosmogenic helium contents in a suite of hawaiian radiocarbon dated lava flows the lava flows ranging in age from 600 to 13 000 years were collected from hualalai and mauna loa volcanoes on the island of hawaii because cosmic ray surface exposure dating requires the complete absence of erosion or soil cover these lava flows were selected specifically for this purpose the 3 he production rate measured within olivine phenocrysts was found to vary significantly ranging from 47 to 150 atoms g 1 yr 1 normalized to sea level although there is considerable scatter in the data the samples younger than 10 000 years are well preserved and exposed and the production rate variations are therefore not related to erosion or soil cover data averaged over the past 2000 years indicate a sea level 3 he production rate of 125 30atoms g 1 yr 1 which agrees well with previous estimates the longer record suggests a minimum in sea level normalized 3 he production rate between 2000 and 7000 years 55 15atoms g 1 yr 1 as compared to samples younger than 2000 years 125 30 atoms g 1 yr 1 and those between 7000 and 10 000 years 127 19atoms g 1 yr 1 the minimum in production rate is similar in age to that which would be produced by variations in geomagnetic field strength as indicated by archeomagnetic data however the production rate variations a factor of 2 3 0 8 are poorly determined due to the large uncertainties in the youngest samples and questions of surface preservation for the older samples calculations using the atmospheric production model of o brien 1979 35 and the method of lal and peters 1967 11 predict smaller production rate variations for similar variation in dipole moment a factor of 1 15 1 65 because the production rate variations archeomagnetic data and theoretical estimates are not well determined at present the relationship between dipole moment and production rate will require further study precise determination of the production rate is an important uncertainty in the surface exposure technique but the data demonstrate that it is feasible to date samples as young as 600 years of age providing that there has been no erosion or soil cover therefore the technique will have important applications for volcanology glacial geology geomorphology and archaeology

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

rock to sediment slope to sea with 10be rates of landscape change abstract measurements of cosmogenic nuclides predominately 10be allow new insights into the ways in which and the rates at which sediment is generated transported and deposited over timescales ranging from 103 to 106 years samples from rock exposures are used to estimate erosion rates at points on the landscape whereas samples of fluvial sediment provide estimates of basin scale rates of denudation integrated over 104 km2 nuclide data show that hilltop bare rock outcrops erode more slowly than basins as a whole suggesting the potential for relief to increase over time as well drained outcrops grow higher more elaborate experiments and interpretive models provide insight into the distribution of hillslope processes including the bedrock to soil conversion rate which appears to increase under shallow soil cover and then decrease under deeper soils changes in average nuclide activity down slopes can be used to estimate grain speed over millennia suggesting for example that sediment o

control of geomorphic processes on 10be concentrations in individual clasts complexity of the exposure history in gobi altay range mongolia the dating of alluvial landforms by cosmogenic nuclides requires distinguishing the pre deposition inheritance from the post deposition history of the clasts in the studied marker moreover estimating catchment scale erosion rates from the concentrations of cosmogenic nuclides in active alluvia requires a good knowledge of the local regional relationships between rock exhumation and transport through space and time this is still poorly known for timescales of tens of thousand years in order to document the evolution of clast exhumation and transport rates through time we analyze in situ 10be concentrations in boulders and cobbles from hillslopes to outlet of an arid mountainous catchment located in gobi altay mongolia strongly affected by global climatic changes during the pleistocene holocene period samples were collected on bedrock abandoned alluvial deposits active colluvia and alluvia our results show a large 10be scattering in the active river bed consistent with a low and discontinuous catchment erosion rate dominated by mass wasting and fluvial incision on the contrary pre exposure signal within abandoned terraces is much more homogeneous consistent with climatic pulses responsible of strong erosional events on hillslopes and rapid fluvial transport these results show that exhumation transport processes at the catchment scale vary in style and intensity through time as a consequence of climatic oscillations the occurrence of abrupt climatic changes during short periods of time recorded by 10be concentrations in abandoned alluvia raise questions about the temporal applicability of catchment erosion rates derived from cosmogenic nuclide concentrations measured in sediments of active rivers on the other hand strong and short erosion events limit and homogenize the pre exposure 10be signal in associated deposits like debris flows making them particularly suitable markers for dating in active tectonic and paleoclimatic studies

quaternary geomorphological evolution of a granitic shore platform constrained by in situ 10 be concentrations penmarc h sw brittany france abstract the penmarc h granitic coastal domain sw brittany western france offers the opportunity to address the little investigated issue of erosional processes in a granitic coastal context from land to sea the granitic coast is composed of 1 an aerial marine terrace 10 be analyses supplies new constraints on the weathering and denudation processes recorded by the penmarc h platform in quaternary times the role of at least two denudation events is emphasized i a 1 8 m thick level of granitic material is assumed to have been removed by erosion during the mis5 sea level highstand both in the offshore domain and in the low part of the marine terrace ii an additional 0 6 m thick level of the granitic substratum was later removed during the last holocene transgression mainly in the marine domain the lack of any morphological step between the subaerial marine terrace and the shore platform is here attributed to the combined effect of multiple factors including i a quaternary tectonic quiescence ii a major eustatic transgression mis5 shaping both the shore platform and the low part of the marine terrace iii the mechanically strong behaviour of the granitic basement with regard to erosion and iv the moderate influence of the holocene sea level stillstand since 6 ka on the shore platform thanks to 10 be content analysis a range of vertical erosion rates of ca 3 6 m ma 1 is obtained for the onshore domain showing no discernable difference between the intertidal and aerial erosion rates from that result it is thus determined that the long term development of the penmarc h granitic shore platform was mainly driven by marine erosive processes during the mis5 and holocene marine transgressions whereas subaerial erosive processes prevailed after the mis5 event

steady erosion rates in the himalayas through late cenozoic climatic changes sediment accumulation rates and thermal trackers suggest a substantial and global increase in erosion rates over the past few million years that increase is commonly associated with the impact of the northern hemisphere glaciation but methodological biases have led researchers to debate this hypothesis here we test whether himalayan erosion rates increased by measuring beryllium 10 10be in the sediment of the bengal bay seabed sediment originated from rocks that produced 10be under the impact of cosmic rays during erosion near surface thus the 10be concentrations indicate erosion rates the 10be concentration of the bengal bay sediment depends on the contributions of the ganga and brahmaputra rivers their sediments have distinct 10be concentrations because of distinct elevations and erosion in their drainage basins variable contributions could thus complicate erosion rate calculation we traced these contributions by a provenance study using the strontium sr and neodymium nd isotopic sediment compositions within uncertainties of 30 our reconstructed past erosion rates show no long term increase for the past six million years this stability suggests that climatic changes during the late cenozoic have an undetectable impact on the erosion patterns in the himalayas at least on the ten thousand to million year timescales accounted for by our dataset long term himalayan erosion rates remained stable through the global climatic changes of the past six million years according to the cosmogenic nuclide composition of terrestrial sediments recovered from the bay of bengal

moraine preservation and boulder erosion in the tropical andes interpreting old surface exposure ages in glaciated valleys cosmogenic dating provides a long awaited means of directly dating glacial deposits that pre date the last glacial cycle although the potential benefits of longer chronologies are obvious the greater uncertainty associated with older cosmogenic ages may be less readily apparent we illus trate the challenges of developing and interpreting a long chronology using our data from the peruvian andes we used surface exposure dating with cosmogenic radionuclides crns 10 be and 26 al to date 140 boulders on moraines in valleys bordering the junin plain 11 s 76 w in central peru our chronology spans multiple glacial cycles and includes exposure ages greater than 1 million years which indicate that long term rates of boulder erosion have been very low interpreting the chronology of moraines for glaciations that predate the last glacial cycle is complicated by the need to consider boulder erosion and exhumation surface uplift and inheritance of crns from pre vious exposure intervals as an example we recalculate exposure ages using our boulder erosion rates 0 3 0 5 metres per million years and estimated surface uplift rates to emphasise both the chal lenges involved in interpreting old surface exposure ages and the value of chronological data even with large uncertainties when reconstructing the palaeoclimate of a region copyright 2005 john wiley sons ltd

a comparison of deep antarctic ice cores and their implications for climate between 65 000 and 15 000 years ago abstract three ice cores drilled in the central part of the antarctic continent extend back to the last glacial period one from west antarctica byrd and two from east antarctica vostok and dome c this period is also partly covered by a few cores from the coastal areas in these cores climatic information is mostly derived from the isotopic profiles d or 18 o from which surface temperature and more indirectly precipitation rate can be estimated the main objective has been to compare thoroughly the three deep ice cores for the main part of the last glacial period from ca 65 000 15 000 yr b p the time scales have been examined in detail and a new 40 000 yr chronology for the dome c core adopted special emphasis is placed on the link between the concentration of 10 be and past accumulation changes and on the use of peaks in the concentration of this cosmogenic isotope as stratigraphic markers elevation changes of the ice sheet derived from gas content and isotopic data bear directly on interpretations of past temperature and precipitation rate changes

major temporal variations in shortening rate absorbed along a large active fold of the southeastern tianshan piedmont china the investigation of deformation rates on a mountain piedmont can provide key information for improving our understanding of the overall dynamics of a mountain range here we estimate the shortening rate absorbed by a quaternary emergent detachment fold on the southeastern piedmont of the tianshan china our work is primarily based on new 10be cosmogenic exposure dating of deformed alluvial surfaces the method we have developed combines depth profiling with sampling of surface cobbles thereby allowing exposure time erosion rate and inheritance to be simultaneously constrained the exposure ages of the uppermost uplifted alluvial surfaces are around 140 17 ka140 17 ka 130 9 ka130 9 ka and 47 9 ka47 9 ka from west to east a terrace lying below the 140 ka surface is dated at 65 5 ka65 5 ka the ages of the uplifted and folded alluvial surfaces were then combined with estimates of shortening obtained using two distinct methods 1 the excess area method where sedimentation rates extracted from magnetostratigraphic studies are used to determine the amount of sedimentation after the abandonment of the river and 2 a folding model derived from sandbox experiments the late pleistocene shortening rates are shown to be between 0 4 0 1 mm yr0 4 0 1 mm yr and 0 8 0 5 mm yr0 8 0 5 mm yr on the western part of the fold and 2 1 0 4 mm yr2 1 0 4 mm yr along its central part the central part of the frontal yakeng anticline therefore accommodates up to 25 of the total shortening currently absorbed across the whole eastern tianshan range 8 mm yr however this situation seems to have prevailed for only the last 150 ka as the shortening rate absorbed by this nascent fold was previously ten times slower while the initiation of folding of the yakeng anticline can be traced back to 5 5 ma ago the basinward migration of the active deformation front onto the yakeng fold is a relatively recent phenomenon and appears to be diachronous from west to east probably in relation to the tectonic activity of the folds in the hinterland

spatial variations in late quaternary slip rates along the doruneh fault system central iran the doruneh fault system dfs is one of the major active strike slip faults in the arabia eurasia collision zone despite its geological activity no large m 6 5 historical or instrumental earthquakes have been recorded along it to date the rate and distribution of slip as well as the seismic behavior of the dfs have been unknown we reconstructed 67 geomorphic offsets recorded by three successive alluvial abandonment surfaces q1 q2 and q3 displaced along the western wfz and central cfz fault zones the determined ages of 12 36 and 120 ka using in situ produced 10 be and 36 cl cosmogenic nuclides for theses surfaces allowed to estimate three sets of individual left lateral slip rates and consequently to describe the spatiotemporal distribution of slip along the cfz and wfz the slip rates averaged over time intervals of 36 and 120 ka reveal variable slip rates along length but similar slip rates at a point with a maximum rate of 8 2 mm yr during the holocene however the fault slip behavior appears more complex with a maximum rate of 5 3 mm yr the cfz is divided into two 4 km apart segments with symmetrical slip distributions relative to a persistent boundary which has not been ruptured over the last 12 ka the maximum length of seismic fault segments varies from 70 to 100 km which could produce earthquakes with a magnitude of m w 7 2 7 4 this emphasizes the necessity of segmentation models for long strike slip faults that may not necessarily rupture along their whole length during a single earthquake

new constraints on slip rates of the fodongmiao hongyazi fault in the northern qilian shan ne tibet from the 10 be exposure dating of offset terraces abstract the fodongmo hongyazi fault fhf is a major thrust of northeastern tibet bounding the qilian shan it accommodates crustal shortening across this region and has produced a strong historical earthquake until now the slip rate has been poorly constrained limiting our understanding of its role in the accommodation of deformation across this region in this paper faulted terraces at two sites on the western and middle segments of the fhf were mapped with satellite imagery and field observations chronological constraints are placed on the ages of displaced river terraces at these sites using terrestrial cosmogenic nuclide tcn exposure dating these ages combined with offsets measured from spot 6 dem s yield average vertical slip rates of 1 3 0 1 mm yr for the western segment since 207 ka and 0 9 0 1 mm yr since 46 ka for the middle segment these data suggest that the fhf accommodates 15 20 of the total shortening across the qilian shan 5 5 7 mm yr in addition comparisons of our data with published slip rates along the northern qilian thrust fault zone show that the fastest tectonic uplift occurs along the western portion of the northern qilian shan this is consistent with estimates deduced from geomorphology the western portion of the qilian shan is mainly controlled by compressional deformation produced by the northward movement of the northeastern tibetan plateau while the eastern qilian shan is mainly controlled by the eastward extrusion of material along the left lateral haiyuan strike slip fault

measurements of past ice sheet elevations in interior west antarctica a lateral moraine band on mount waesche a volcanic nunatak in marie byrd land provides estimates of past ice sheet surface elevations in west antarctica helium 3 and chlorine 36 surface exposure ages indicate that the proximal part of the moraine up to 45 meters above the present ice surface was deposited about 10 000 years ago substantially later than the maximum ice extent in the ross embayment the upper distal part of the moraine may record multiple earlier ice sheet high stands a nonequilibrium ice sheet model predicts a delay of several thousand years in maximum ice levels at mount waesche relative to the maximum ice extent in the ross sea the glacial geologic evidence coupled with the ice sheet model indicates that the contribution of the ross sea sector of the west antarctic ice sheet to holocene sea level rise was only about 3 meters these results eliminate west antarctic ice as the principle source of the large meltwater pulse during the early holocene

revisiting the age of the jumento volcano chichinautzin volcanic field central mexico using in situ produced cosmogenic 10be abstract previous studies on jumento volcano based on radiocarbon dating and comparative morphometric analysis suggest that it could be the youngest volcano of the sierra chichinautzin here we establish a new chronology of the emplacement of the late holocene lava flows of jumento volcano using in situ produced 10be cosmic ray exposure cre dating of quartz xenocrysts to test this hypothesis depending on the choice of the cosmogenic nuclide production parameters in the exposure age calculators used the mean 10be cre ages ranges between 1 86 0 68 ka and 2 41 0 97 ka for the inner lava flow and between 1 90 0 29 ka and 2 49 0 41 ka for the breakout lava flow these preliminary mean 10be cre ages confirm that the jumento volcano is one of the youngest volcanoes of the sierra chichinautzin although slightly older than the xitle volcano this first 10be eruption chronology of the sierra chichinautzin shows that 10be cre dating represents an alternative approach to date volcanic rocks not only for the sierra chichinautzin but also for other volcanic fields especially when no charcoal or paleosoils are available for radiocarbon dating furthermore it suggests that in situ produced cosmogenic nuclide dating has considerable potential to throw light on the volcanic history and eruption recurrence of this volcanic field in order to provide enough data for the mitigation of the hazards and related risks in mexico city the city of cuernavaca and the small towns around the volcanic field

dating faulted alluvial fans with cosmogenic 10be in the gurvan bogd mountain range gobi altay mongolia climatic and tectonic implications the gurvan bogd mountain range is a fault system characterized by strong earthquakes m 8 separated by long periods of quiescence further to the previous works in the area our study provides new data concerning the tectonic and climatic processes in the gobi altay to quantify the slip rates along the faults we dated offset alluvial fans analysing the in situ produced 10 be along profiles at depth the slip rates along the bogd strike slip fault and its associated thrust faults over the upper pleistocene holocene period are 0 95 0 29 mm yr 1 and comprised between 0 12 0 02 and 0 13 0 02 mm yr 1 respectively the surfaces ages account for a cyclic formation of the fans over the past 360 ka in correlation with the terminations of the marine isotope stages 2 6 8 and 10

the accumulation of cosmogenic chlorine 36 in rocks a method for surface exposure dating because of the reaction of cosmic rays with elements in minerals chlorine 36 accumulates in rocks exposed at the earth s surface this suggests that the ratio of chlorine 36 to stable chloride can be used as a geochronometer reasonable agreement has been obtained between measurements of chlorine 36 in volcanic rocks of known age and calculations of chlorine 36 production based on rock composition and cosmicray flux the buildup of chlorine 36 should be a useful means for measuring the surface exposure time of young volcanic rocks and geomorphic features in the age range of 10 3 to 10 6 years

co seismic deformation and post glacial slip rate along the magallanes fagnano fault tierra del fuego argentina fil roy sandrine centre national de la recherche scientifique francia universite savoie mont blanc francia

geochemical characterization of malm zeta laminated carbonates from the franconian alb sw germany ii abstract during jurassic times especially within the malm stage local depressions formed on the eastern bavarian carbonate platform that were surrounded by wall reefs this created a unique depositional environment where in an open marine setting stagnant and anoxic bottom waters developed in an intra reef depression anoxic conditions were stabilized below wave base by enhanced salinity in the bottom waters and establishment of a density stratification biomarker analysis was applied to characterize palaeosalinity and redox conditions utilizing organic sulfur compound methylated chroman hopanoid and saturated isoprenoid distributions prevention of terrigenous influx by protecting reef walls lead to iron deficiency in intra reefal sediments causing early diagenetic sulfurization of functionalized lipids absence of clay mineral catalysts and early sulfurization favored an unusual steroid distribution lacking rearranged analogues but providing coexistence of saturated steranes with and configuration 13 17 spirosterenes unknown sterenes and steradienes as well as mono di and triaromatic steroids desulfurization of the polar fraction was carried out for two samples to verify that palaeoenvironment reconstruction based on free hydrocarbon and heterocompound distribution was not invalidated by sulfur quenching of selected compounds gammacerane was found to be the only component to occur exclusively in the sulfur bound fraction only minor amounts of hydrocarbons were released upon desulfurization implying that free bitumen analysis was applicable for organofacies characterization organic petrological investigation of organic mats revealed the presence of two different types of such structures comparison of organoclast fluorescence spectra with those of extracted porphyrin fractions indicate an origin of porphyrins exclusively from cyanobacterial mats whereas algal dominated mats yield no porphyrins this aims towards a better localization of specific biomarker origin in geological samples

cosmic ray production rates of 10be and 26al in quartz from glacially polished rocks we have studied the concentrations of 10be and 26al in quartz crystals extracted from glacially polished granitic surfaces from the sierra nevada range these surfaces were identified with the glacial advance during the tioga period 11 000 years ago our measurements yield the most accurate estimates to date for the absolute production rates of these nuclides in sio2 due to cosmic ray nucleons and muons for geomagnetic latitudes 43 8 44 6 n and altitudes 2 1 3 6 km the estimates are relatively free from uncertainties in snow cover since we studied a suite of rock surfaces inclined 0 75 with respect to the horizontal the principal uncertainty arises due to the lack of a precise date for the glacial retreat event about 10 the 26al 10be ratio at production 6 0 is determined more accurately since the exposure age of the samples is 2 orders of magnitude smaller than the mean lives of the two nuclides production rates of 10be and 26al in quartz at other latitudes and altitudes in the troposphere can be determined from the present measurements by scaling using the known altitude and latitude dependence of cosmic ray fluxes of nucleons and negative muons knowledge of the production rates of these nuclides is a prerequisite for their application in erosion and geomorphological studies

late wisconsin and early holocene glacial history inner ross embayment antarctica abstract lateral drift sheets of outlet glaciers that pass through the transantarctic mountains constrain past changes of the huge ross ice drainage system of the antarctic ice sheet drift stratigraphy suggests correlation of reedy iii reedy glacier beardmore beardmore glacier britannia hatherton darwin glaciers ross sea mcmurdo sound and younger terra nova bay drifts radiocarbon dates place the outer limits of ross sea drift in late wisconsin time at 24 000 13 000 yr b p outlet glacier profiles from these drifts constrain late wisconsin ice sheet surface elevations within these constraints we give two extreme late wisconsin reconstructions of the ross ice drainage system both show little elevation change of the polar plateau coincident with extensive ice shelf grounding along the inner ross embayment however in the central ross embayment one reconstruction shows floating shelf ice whereas the other shows a grounded ice sheet massive late wisconsin holocene recession of grounded ice from the western ross embayment which was underway at 13 040 yr b p and completed by 6600 6020 yr b p was accompanied by little change in plateau ice levels inland of the transantarctic mountains sea level and basal melting probably controlled the extent of grounded ice in the ross embayment the interplay between the precipitation low late wisconsin and high holocene values and the influence of grounding on outlet glaciers late wisconsin thickening and late wisconsin holocene thinning with effects dying out inland probably controlled minor elevation changes of the polar plateau

erosion of the eastern united states observed with 10be the problem of identifying areas of accelerated erosion in a dynamic landscape is complicated the limited history of sediment yield measurements makes this task difficult even if geomorphic evidence is available beryllium 10 a cosmogenic isotope produced by cosmic rays interacting with the earth s atmosphere and surface has chemical and physical properties that make it useful as a tracer for erosion and sediment transport processes the rarity of the stable isotope 9be allows 10be to be detected with accelerator mass spectrometry in natural materials at extremely low levels backgrounds for rocks and sediments below 105 atom per g are now attainable a value to be compared with an average deposition rate of 1 3 106 atom cm 2 yr 1 the affinity of be for the components of soil and sediment is sufficiently high that it is effectively immobilized on contact thereby allowing 10be to function as a tracer of sediment transport to a good approximation all the 10be transport out of a drainage basin is on the sediment leaving it the number of 10be atoms passing the gauging station can be determined by measuring the concentration of the isotope in the sediment if the annual sediment load is known the ratio of the 10be carried from the basin by the sediment to that incident upon it called the erosion index has been determined for 48 drainage basins within the same physiographic province which allows them to be reasonably compared all of which have sediment yield data basins located in the atlantic coastal plain have an average index of 0 3 with the maximum observed being 0 9 basins located between the fall line and the mountains a region called the piedmont have an average value of 2 2 with individual values ranging from 0 6 to 6 7 this marked difference is thought to result from two centuries of farming on land of moderate gradient basins in the highland regions reflect local conditions with low indices for those in grass and timber and high indices associated with destructive land use the data allow an estimate of the erosion index for the pre colonial piedmont which then allows the pre colonial sediment yield to be calculated a number of basins have also been examined world wide with similar conclusions derived an important deviation from the rule is noted for rivers that erode large regions of loess such as the mississippi hwang ho and yangtze large aeolian deposits were laid down during the ice age in these basins deposits that brought inherited 10be with them and that are easily eroded

dating inset terraces and offset fans along the dehshir fault iran combining cosmogenic and osl methods summary be and 36 cl cosmic ray exposure cre and optically stimulated luminescence osl dating of offset terraces have been performed to constrain the long term slip rate of the dehshir fault analysis of cosmogenic 10 be and 36 cl in 73 surface cobbles and 27 near surface amalgamscollectedfrominsetterracesdemonstratestheoccurrenceofalowdenudationrateof 1mm a 1 and of a significant and variable inheritance from exposure prior to the aggradation of these alluvial terraces the significant concentrations of cosmogenic nuclides measured in the cobbles collected within the riverbeds correspond to 72 20 ka of inheritance the mean creageofthesurfacesamplescollectedontheolderterracet3is469 88kabuttheanalysis of the distribution of 10 be concentration in the near surface samples discard ages older than 412 ka the mean cre age of the surface samples collected on terrace t2 is 175 62 ka but the 10 be depth profile discard ages older than 107 ka for each terrace there is a statistical outlier with a younger age of 49 9 3 3 and 235 5 35 4 ka on t2 and t3 respectively the late sediments aggraded before the abandonment of t2 and inset levels t1 b and t1a yielded osl ages of respectively 26 9 1 3 21 9 1 5 and 10 0 0 6 ka for a given terrace the osl ages where available provide ages that are systematically younger than the cre ages these discrepancies between the cre and osl ages exemplify the variability of the inheritance and indicate the youngest cobble on a terrace that minimizes the inheritance is the most appropriate cre age for approaching that of terrace abandonment however the upper bound on the age of abandonment of a terrace that is young with respect to the amount of inheritance is best estimated by the osl dating of the terrace material for such terraces the cre measurements are complementary of osl dating and can be used to unravel the complex historyofweatheringandtransportinthecatchmentofdesertalluvialfans thiscomprehensive set of dating is combined with morphological offsets ranging from 12 2t o 380 20 m to demonstrate the dehshir fault slips at a rate in the range 0 9 mm yr 1 1 5 mm yr 1 t he variable inheritance exemplified here may have significant implications for cre dating in arid endorheic plateaus such as tibet and altiplano

surface exposure chronology using in situ cosmogenic 3he in antarctic quartz sandstone boulders abstract in situ produced cosmogenic helium 3 he c provides a new tool for constraining histories of quaternary geomorphic surfaces before general application of the technique however the systematics and production rates of 3 he c must be well understood in a companion study 3 he and 10 be data from sandstone and granite boulders in the dry valleys region of antarctica have been used to constrain the ages of an important moraine sequence formed by the taylor glacier data from these deposits also provide information about the systematics of 3 he in quartz that has important implications for geochronology based on 3 hec in contrast to previous results from olivine and clinopyroxene crushing quartz in vacuo releases helium with high 3 he 4 he ratios up to 148 r a where r a is the atmospheric 3 he 4 he ratio indicating that crushing cannot be used to determine the isotopic composition of trapped i e noncosmogenic helium in quartz analysis of 3 he in different size fractions of the same samples indicates significant 3 he loss not predicted by existing 3 he diffusion data for quartz the origin of the discrepancy is not clear but loss from these samples is not as significant as suggested by the limited data of previous studies

denudation rates of the southern espinhaco range minas gerais brazil determined by in situ produced cosmogenic beryllium 10 article to investigate denudation rates in the southern part of the espinhaco range central eastern brazil and to understand how this important resistant and residual relief has evolved in the past 1 38 my cosmogenic 10 be concentrations produced in situ were measured in alluvial sediments from the three main regional ba sins whose substratum is composed primarily of quartzites the long term denudation rates up to 1 38 my estimated from these measurements were compared with those that affect the western sao francisco river and eastern doce and jequitinhonha rivers basins which face the west san francisco craton and the atlantic respectively denudation rates were measured in 27 samples collected in catchments of different sizes 6 970 km 2 and were compared with geomorphic parameters the mean denudation rates determined in the northern part are low and similar to those determined in the southern part despite slightly different geomorphic parameter values catchment relief and mean slope for the southern catchments the values are 4 91 1 01 mmy 1 and 3 65 1 26 mmy 1 for the doce and sao francisco river basins respectively for the northern catchments they are 4 40 1 06 mmy 1 and 3 96 0 91 mmy 1 for the jequitinhonha and sao francisco river basins respectively these low values of denudation rates suggest no direct correlation if plotted against geomorphic parameters such as the catchment area maximum elevation catchment relief average relief and mean slope gradients these values show that the regional landscape evolves slowly and is strongly controlled by resistant lithology with similar erosional rates in the three studied basins

improved discrimination of subglacial and periglacial erosion using 10be concentration measurements in subglacial and supraglacial sediment load of the bossons glacier mont blanc massif france deciphering the complex interplays between climate uplift and erosion is not straightforward and estimating present day erosion rates can provide useful insights glaciers are thought to be powerful erosional agents but most published glacial erosion rates combine periglacial subglacial and proglacial erosion processes within a glaciated catchment sediments found in subglacial streams originate either from glacial erosion of substratum or from the rock walls above the glacier that contribute to the supraglacial load terrestrial cosmogenic nuclides tcn are produced by interactions between cosmic ray particles and element targets at the surface of the earth but their concentration becomes negligible under 15 m of ice measuring tcn concentrations in quartz sand sampled in subglacial streams and in supraglacial channels is statistically compliant with stochastic processes e g rockfalls and may be used to discriminate subglacial and periglacial erosion results for two subglacial streams of the bossons glacier mont blanc massif france show that the proportion of sediments originating from glacially eroded bedrock is not constant it varies from 50 to 90 n 6 the difference between the two streams is probably linked to the presence or absence of supraglacial channels and sinkholes which are common features of alpine glaciers therefore most of the published mean catchment glacial erosion rates should not be directly interpreted as subglacial erosion rates in the case of catchments with efficient periglacial erosion and particularly rockfalls the proportion of sediments in the subglacial stream originating from the supraglacial load could be considerable and the subglacial erosion rate overestimated here we estimate warm based subglacial and periglacial erosion rates to be of the same order of magnitude 0 39 0 33 and 0 29 0 17 mm a 1 respectively

cosmogenic chlorine 36 chronology for glacial deposits at bloody canyon eastern sierra nevada deposits from mountain glaciers provide an important record of quaternary climatic fluctuations but have proved difficult to date directly a chronology has been obtained for glacial deposits at bloody canyon california by measurement ofthe accumulation of chlorine 36 produced by cosmic rays in boulders exposed on moraine crests the accumulation ofchlorine 36 indicates that episodes of glaciation occurred at about 21 24 65 115 145 and 200 ka thousand years ago although the timing of the glaciations correlates well with peaks of global ice volume inferred from the marine oxygen isotope record the relative magnitudes differ markedly the lengths of the moraines dating from 115 ka and 65 ka show that the early glacial episodes were more extensive than those during the later wisconsin and indicate that the transition from interglacial to full glacial conditions was rapid