luminescence dating of sediments from buctouche spit new brunswick in this paper we describe our efforts to determine the formation chronology of a sequence of dunes on buctouche spit a holocene deposit on the northeast coast of new brunswick optical dating using infrared stimulation of k feldspar grains yielded ages ranging from 5 30 a for an embryo dune to 765 45 a for the oldest dune thermoluminescence ages although less precise support the recent formation of the dunes the ages exhibit the expected sedation from youngest to oldest and are consistent with historical evidence coupled with an assumed constant sediment aggradation rate the age resolution obtained was very good and we conclude that the optical dating method used here shows great promise

style and timing of glaciation in the lahul himalaya northern india a framework for reconstructing late quaternary palaeoclimatic change in the western himalayas

facies architecture and sequence stratigraphy in glacially influenced basins basic problems and water level glacier input point controls with an example from the quaternary of ontario canada abstract sequence architecture is controlled by two fundamental factors the water level relative to the depositional surface which controls accommodation space and the points or areas of sediment injection which control how this space is filled in relative water level accommodation space and injection points normally vary together and various genetic terms are used to define systems tracts but in glacially influenced basins accommodation space is controlled not only by water level but also by the glacier injection points are similarly dually controlled by water level and by the terminus of the glacier during high lake levels the injection point of the glacier may be underwater at the base of the slope genetic terms like highstand and lowstand therefore are meaningless in successions controlled by sediment input points which are independent of water levels and accommodation space distinct water level and glacier input point systems can occur side by side the water level system controlled by lake level or sea level the glacier input point system controlled by the position of the subaqueous glacier front and both can form juxtaposed systems passing laterally into each other a bewildering and incompatible terminology is needed if the terms of genetic sequence stratigraphy are used for both water level and glacier input point systems because the sedimentary injection points and sequence boundaries of the two systems fluctuate out of phase with one another sequences developed by movement of the glacier are completely independent of those controlled by water levels if genetic sequence stratigraphy is applied to a basin with both lake level and glacier input point systems then each needs separate genetic terminologies to describe them which leads only to confusion however descriptive sequence stratigraphy allostratigraphy can be readily applied to successions like the quaternary of lake ontario we therefore suggest that genetic sequence terms be discarded and simpler allostratigraphic terminology used in glacially influenced basins

optical dating of a scroll bar sequence on the klip river south africa to derive the lateral migration rate of a meander bend problems are often encountered in accurately establishing the rates of processes associated with river channel change in this study optical dating was used to obtain the lateral migration rate of an abandoned meander bend on the klip river eastern free state south africa five samples were collected by augering along a transect across an approximately 200 m wide scroll bar sequence on the inner meander bend and an additional sample was collected from the channel fill of the related oxbow lake optically stimulated luminescence osl ages were derived for each sample using the single aliquot regenerative dose protocol on small aliquots of quartz incomplete bleaching was evident in some of the samples and thus the appropriate statistical analysis was performed using the finite mixture model for the scroll bar samples and the minimum age model for the channel fill sample the ages calculated were in the correct chronological order for the depositional sequence which was formed over the last 1000

reconstructing the architecture and sequence stratigraphy of the preserved fluvial record as a tool for reservoir development a reality check driven in part by the need for better information about fluvial systems for the purpose of nonmarine reservoir evaluation and development much valuable work is now being conducted on modern rivers and their deposits aided by such techniques as ground penetrating radar however studies of modern and recent systems cannot address the question of the long term preservability of the present day deposits only studies of the rock record itself can explore this issue two separate studies of ancient fluvial systems illustrate some of the problems a study of the hawkesbury sandstone triassic sydney basin australia highlighted the difficulty in interpreting the dimensions of large sand bodies from comparisons with a modern analog even when very large outcrops are available a seismic time slice study of pliocene pleistocene fluvial systems in the gulf of thailand revealed major changes in channel size and fluvial style over short vertical intervals braided and meandering systems meander belt widths 4 to 10 km 2 5 to 6 mi are separated by a few tens of meters of section or less and are interbedded with the deposits of much smaller rivers showing straight meandering and anastomosed patterns incised valleys and underfit streams are also present these variations can be interpreted in terms of a sequence model but they indicate the problems that could arise from the use of a single suite of dimensional variables as input into numerical reservoir heterogeneity and flow models most numerical simulation models make use of sets of equations relating such parameters as channel width depth and sinuosity but most such equations are generalized across the whole spectrum of fluvial styles and can be conditioned to the reality of individual reservoirs only with difficulty the application of the principles of sequence stratigraphy to fluvial deposits is rendered difficult by the complex response to allogenic forcing that characterizes fluvial systems episodes of aggradation and degradation that may be used to define sequences and their bounding unconformities in the stratigraphic record may be the result of the complex interplay of several allogenic mechanisms governing varying stream power and sediment supply mechanisms that may be operating at different time scales and may be out of phase with each other in developing practical solutions for reservoir development numerical modeling and simulation may provide generalized starting points for the analysis history matching commonly demonstrates inaccuracies in many initial models further progress may be made by direct study of the reservoir itself using three dimensional 3 d seismic and surveillance techniques there is a continuing role for the study of ancient analogs as providing a realistic database on the long term preservation styles of fluvial reservoir deposits

underwater bleaching of signals from sediment grains new experimental data abstract the results of an underwater bleaching experiment are reported the purpose of the experiment was to evaluate the degree to which thermoluminescence tl and optically stimulated luminescence osl signals are reduced by a three hour exposure to light at different water depths samples of quartz and feldspar separates were annealed in the laboratory and then given fixed doses of laboratory beta radiation before exposure the results indicate that a three hour light exposure is sufficient to zero the optical signals down to water depths of 10 m for feldspar infra red stimulated luminescence and 12 14 m for quartz osl the tl results for the same quartz and feldspar samples exhibit some bleaching effects with tl signals at 14 m water depth being reduced to 50 65 of the initial value scatter of the tl results limits their interpretation

the effect of thermal transfer on the zeroing of the luminescence of quartz from recent glaciofluvial sediments abstract the natural optically stimulated luminescence osl response of quartz grains extracted from a range of recent glaciofluvial and other glaciogenic sediments from western greenland is presented all samples were deposited within the last 10 years many only days or hours before collection consequently we would expect to measure zero or very small d e values had optical resetting of the osl signal been complete in the case of most samples d e values in the range 0 5 10 gy are observed while higher values are observed for a handful of samples however the regenerated osl growth curves constructed after daylight exposure of at least several hours also show large apparent d e values negative x axis intercepts corresponding samples from four different locations in the indian himalaya display similar osl characteristics the measurement of several regenerated osl growth curves omitting the preheat procedure which normally precedes osl measurement confirms that a significant degree of thermal transfer is occurring during the preheating it is this thermal transfer of charge during the preheat which is responsible for a significant contribution to the large apparent d e values observed for the regenerated osl growth in this paper we describe combined osl and tl measurements which have been used to monitor the charge transfer in detail for one sample an attempt is made to describe the charge transfer behaviour and we discuss methods appropriate to eliminating the unwanted effects of this phenomenon during osl dating preliminary results from the application of these techniques are presented and the implications of these observations for the osl dating of glaciogenic sediments are discussed

thermoluminescence dating studies of glacial silts from ontario to develop procedures for the direct dating of glacially related silts by thermoluminescence tl i have applied previously proposed techniques to three polymineralic 4 11 m samples from the toronto area furthermore one of these samples was studied in detail by isolating some mineral fractions the principal conclusion is that the tl of the lodgment halton till from woodbridge was not significantly reset during deposition whereas the tl of the waterlaid upper thorncliffe silt from the scarborough bluffs was reset as was the tl of the third sample wc st a massive silt from woodbridge that has been generally correlated with the glaciolacustrine sunnybrook diamict at the bluffs this conclusion follows from the observation of feldspar tl apparent ages of 140 ka for the 12 ka bp halton till and of 36 and 66 ka for the upper thorncliffe and wc st samples respectively the four laboratory factors that contributed most to inaccuracies in the tl apparent ages were 1 anomalous fading in the felds

optically stimulated luminescence dating of late quaternary glaciogenic sediments in the upper hunza valley validating the timing of glaciation and assessing dating methods we present a comprehensive comparison of optically stimulated luminescence osl ages with cosmogenic radionuclide crn ages and the first study to validate crn dates from boulders on moraine ridges using luminescence dates from glaciogenic sediments from associated moraines accomplished from both direct and stratigraphic relationships between crn and osl sampling sites both quartz and k feldspars extracted from 12 late quaternary glaciogenic sediments were studied using single aliquot osl techniques rapid signal saturation in preliminary additive dose infrared stimulated k feldspar luminescence growth data was interpreted as evidence of insufficiently bleached latent luminescence and these data gave rise to overestimated ages in the majority of samples further analysis concentrated on replicated single aliquot regenerative dose sar measurements of quartz minerals using blue green stimulation the sar sensitivity correction method repeatedly failed in two of the samples and a further sample exhibited significant thermal transfer nevertheless three of the eight glacial successions in the upper hunza valley were defined using quartz luminescence although we discuss the possibility of inherited components in the crn data in terms of paleoclimatic interpretations both dating techniques give concordant results

the fan like forms in the southern margin of the mazovian lowland area central poland a new high resolution textural timing study an optically stimulated luminescence technique with a high resolution sampling strategy as well as a set of multiple proxies such as grain size distribution shape surface and microstructures of quartz grains along with mineral composition of light and heavy fractions was used to investigate the age and origin of fan like forms at the southern margin of mazovian lowland poland the predominance of aeolian factors was observed throughout all of the investigated sites however the sedimentary variability of the grains reflected the superposed influence of multiple cold environmental factors such as snow ice interbedded layers cryoturbation processes or a fluvial transformation luminescence ages provide the first detailed chronology of the southern margin of the mazovian lowland deposition began after ca 42 ka and onwards and resulted in the depositional alternation of dry and humid environmental interactions between ca 31 and 25 ka the pre lgm aeolian transformation took place finally during the pomeranian phase in poland at 14 ka polar desert environmental conditions prevailed

cosmogenic dating of rock avalanches constraining quaternary stratigraphy and regional neotectonics in the argentine central andes 32 s abstract this paper provides a comprehensive review of the chronostratigraphy of six rock avalanches clustered in the northern extreme of the cordon del plata range these rock avalanches are stratigraphically related to pleistocene glacial drifts and valley fill deposits documenting the regional neotectonic activity we used cosmogenic dating tcn to directly date block surfaces of rock avalanche deposits as well as optically stimulated luminescence dating osl of paleo lakes dammed by these rock avalanches our new direct dates 17 tcn and 4 osl determine the middle to late pleistocene age of these collapses these are in contrast to the previously established chronostratigraphy based on relative dating techniques paleontological context and tephrochronology these new data help to redefine the geomorphological evolution of the mendoza river valley especially the new data indicate that the glacial stratigraphy earlier proposed must be reconsidered we redefine this stratigraphy as far as possible with our data and discuss the data in relation with other recently published results however it becomes clear that the glacial history of the mendoza valley has to be studied anew by using modern dating techniques in addition our data suggest that the carrera fault system bounding the valleys of the cordillera del plata has been active more recently than proposed earlier

testing an approach to osl dating of late devensian glaciofluvial sediments of the british isles in the british and irish isles the understanding of expansion and retreat of the last ice sheet in marine isotope stage mis 2 has been hindered by a lack of chronological control for the timing of its maximum extent and subsequent retreat stages in this research a suite of lithofacies from a former distal ice marginal sandur at orrisdale isle of man were identified and selected for optically stimulated luminescence dating different size fractions of quartz grains were extracted from selected lithofacies types with the aim of identifying which depositional environments and grain size fractions are best suited for optical dating tests have been undertaken to identify the luminescence properties of this quartz including preheat dose recovery and constant wave optically stimulated luminescence osl decay curve fitting equivalent dose distributions for all samples were wide and positively skewed indicative of heterogeneous bleaching a comprehensive statistically based decision making protocol has been defined in order to find the appropriate statistical model for burial dose estimation ages in the range of 17 14 ka have been obtained which agree with the expected geologically constrained chronology the orrisdale formation is contemporaneous with heinrich event 1 and the killard point stadial identified in eastern ireland ca 16 4 ka the suggested approach for osl dating of glaciofluvial sediments has the potential for much wider application to high latitude or temperate areas where there is an abundance of such sediments and where improved chronological control is much needed copyright 2009 john wiley sons ltd

the resolution of stratigraphic inconsistency in the luminescence ages of marine terrace sediments from korea several sets of marine terraces are exposed along the southeastern coast of the korean peninsula the formation ages of these terraces have attracted considerable attention because they provide essential information on local crustal stability over the last few years considerable effort has been put into the determination of these ages using optically stimulated luminescence osl dating of the marine sediments from which the terraces were built for several sites the results of dose recovery tests and other osl characteristics including the dependence of equivalent dose on heat treatment prior to stimulation have been described in detail elsewhere quat sci rev 22 2003 407 however it has been found that the samples from one site exhibit various undesirable osl characteristics which result in stratigraphically inconsistent osl ages in this paper we investigate these characteristics and use luminescence component separation to resolve this inconsistency the resolved osl ages obtained as such are then used for the discussion on the local crustal stability of the southeastern coast of korea during the late pleistocene

effectiveness of natural zeroing of the thermoluminescence in sediments the last exposure to sunlight of detrital feldspars and quartz grains in quaternary sediments can be dated directly by thermoluminescence tl methods but the effectiveness of zeroing of the light sensitive tl signal by daylight varies widely depending upon details of the sedimentation processes to document this variability and to help develop objective criteria useful for future sample selection and laboratory procedures i have collected and analyzed several eolian fluvial marine deltaic and lacustrine samples from less than 100 year old deposits as well as suspensions from sediment plumes also underwater spectral irradiance was measured during recovery of suspensions tl properties of polyrnineralic feldspar dominated 2 4 m and 4 11 m size fractions were measured in the laboratory unexpectedly some light sensitive tl was found to remain in all samples however the light sensitive tl was more effectively zeroed in some samples a proximal loess a sandy braided channel deposit tidal flat and upper delta front muds and thin clayey lacustrine laminae than in others a silty braided channel deposit submarine fan muds and silt bearing lacustrine laminae for the first group the minimum relict paleodose obtained with the partial bleach technique is about 0 4 0 3 gy corresponding to a relict tl age estimate of about 200 years for these sediments thus similar sediments excluding fluvial deposits as young as about 2 ka can be accurately and routinely dated without significant correction for a zero point error if one uses the partial bleach technique coupled with integrated optical bleaching energy fluences of less than 1 j cm 2 and wavelengths only above about 550 nm also some simple optical bleaching tests are reported that have a potential use in sample selection and in provenance studies of some surficial detrital sediments finally a simple mathematical model is presented that helps account for the gross features of the observed bleaching response curves

aeolian dust transport and deposition by foehn winds in an alpine environment lake tekapo new zealand abstract observations from an automatic weather station and anemograph network are used in conjunction with recorded dust deposition rates to identify principle sources of wind blown dust within an alpine lake basin meteorological observations made throughout the study indicate that foehn windstorms provide ideal conditions for the initiation of aeolian processes including dust storm genesis a mean wind speed during foehn windstorms of 7 5 m s 1 at 2 65 m above the surface was observed to initiate entrainment of dust particles from geomorphically active areas within the lake basin particularly from the dry braid channels of glacier fed rivers exposed lacustrine deltas and degraded tussock grasslands this threshold entrainment velocity is similar to others presented within the international literature for such surface types a diurnal modulation of meteorological parameters monitored during foehn wind events suggests that aeolian processes such as dust entrainment are most likely to occur from late morning to early evening however where topography enhances wind speeds for example by channelling airflow down river valleys favourable conditions for dust entrainment may prevail throughout the night in the absence of precipitation potential dust roses were determined for two sites within the lake basin the dust roses supported anecdotal and observational evidence of principle dust sources within the study area and appear to be an effective tool for identifying the potential hazard to a particular location from blowing dust once the physical trigger conditions for dust entrainment are known this requires detailed and concurrent monitoring of meterological variables in association with dust transportation and deposition rates especially in complex terrain where many micro climates often exist

optical dating studies of quartz and feldspar sediment extracts abstract continuing developmental work into optical dating has led to some clarification of the optical behaviour of quartz and feldspar sediment extracts we have verified the key assumption intrinsic to the method that the optical signal is zeroed completely upon exposure to daylight we also show that the rate of zeroing in optical dating is much more rapid than it is in tl dating studies concerned with the extraction of the thermally stable signal from laboratory irradiated samples showed that problems may arise from medium to high temperature preheating of young samples optical alternatives to thermal stabilization were tested using dye and krypton lasers using a krypton laser we have succeeded in obtaining an equivalent dose of 0 0 0 7 gy for the quartz from a modern intertidal sand and an average dose of 120 22 gy for the feldspar extract of a 70 ka sand unit both were obtained using six wavelengths from the infrared to the violet and no dependence on wavelength was found we found that the photon energies of infrared and deep red light can stimulate luminescence in unirradiated quartz and feldspar extracts of sediments this was not expected and suggests that the process of trap emptying is more complex than we had envisioned but implies a far greater than expected degree of technical flexibility for the optical dating method

towards successful osl sampling strategies in glacial environments deciphering the influence of depositional processes on bleaching of modern glacial sediments from jostedalen southern norway the optically stimulated luminescence osl signals of quartz and k feldspar are known to bleach poorly within some glacial settings and can present a major challenge to dating applications however because the osl signal is extremely sensitive to sunlight exposure history the residual luminescence signals of modern glacial sediments also encode information about transport and depositional processes through examination of the residual luminescence properties equivalent dose de and overdispersion values of a suite of modern glacial sediments from different depositional settings sandar proglacial delta and main meltwater channel this study provides insights not only into which sediments are likely to be fully bleached within glacial settings but also into how osl can be used to trace different depositional processes across sedimentary landforms improved understanding of the processes of sediment bleaching will enable better sample selection and may improve the accuracy and precision of osl dating of glacial sediments the luminescence signals of both coarse grained quartz and k feldspar with similar sediment sources are found to be sensitive to both depositional process and specific depositional setting whereas modern braid bar head deposits from the nigardsdalen ice proximal proglacial delta typically have ages of 3 ka similar depositional features from the fabergstolsgrandane sandur have residual ages of 26 ka exploration of changing residual luminescence signals across individual sandur and proglacial delta braid bar features shows that braid bar head deposits can retain large residual d e values while the partner braid bar tail deposits are almost completely bleached the quartz osl signal and k feldspar irsl50 and post ir irsl250 signals are shown to bleach at the same rate across the same bar feature and the irsl50 k feldspar signal is also shown to be completely bleached for bar tail deposits in nigardsdalen therefore the irsl50 k feldspar signal is suitable for dating some glacial deposits circumventing the challenges associated with dim quartz signals 2014 the authors published by elsevier ltd this is an open access article under the cc by license

architectural element analysis applied to glacial deposits internal geometry of a late pleistocene till sheet ontario canada deposits left by continental ice sheets are characterized by sedimentological complexity and stratigraphic heterogeneity but stratigraphic descriptions of such deposits and resulting first generation facies models are still based primarily on one or two dimensional borehole or outcrop data reconstruction of depositional environments hydrogeological investigations of pleistocene glacial deposits and hydrocarbon exploration in pre pleistocene glaciated basin fills require a more detailed understanding of the form and heterogeneity of lithofacies sequences in three dimensions architectural element analysis is used widely by sedimentologists for categorizing internal stratigraphic heterogeneity in sandstones particularly those of fluvial origin this paper demonstrates the first application of architectural element analysis to glacial deposits such as tills outcrop borehole and a broad range of subsurface geophysical data were collected from a thick 60 m till sheet present across an 80 km 2 study area near toronto canada the till sheet is not homogeneous but is composed of three distinct architectural elements and associated lithofacies viz diamict elements interbeds of subglaciofluvial sediments and glaciotectonically deformed zones application of architectural element analysis to these subglacial strata provides insights into the origin of drumlin bedforms and subglacial processes below the laurentide ice sheet and creates a framework for understanding ground water and contaminant movement in underlying aquifers

luminescence dating of quaternary sediments recent advances duller geoffrey 2004 luminescence dating of quaternary sediments recent advances journal of quaternary science 19 2 pp 183 192 rae2008

luminescence dating of proglacial sediments from the eastern alps the potential of optically stimulated luminescence osl for dating proglacial deposits is tested here at three last glacial key sites in the eastern alps this was undertaken using both sand sized feldspar and quartz grains as well as fine silt sized material the samples reveal rather poor luminescence intensities of the investigated quartz grains and it is also clearly demonstrated that several of the deposits were incompletely bleached prior to deposition bleaching experiments were carried out and different approaches for extracting the aliquots where the osl was completely bleached prior to burial were tested applying different osl measurement techniques and analytical procedures we investigated which approach was most appropriate for dating known age proglacial sediments best results were achieved using single aliquot regenerative dose methodology on coarse grain quartz and feldspar samples in combination with the approach of preusser et al 2007 luminescence dating of proglacial sediments from switzerland boreas in press for ed calculation

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

bayesian modelling the retreat of the irish sea ice stream we present an 8000 year history spanning 650km of ice margin retreat for the largest marine terminating ice stream draining the former british irish ice sheet bayesian modelling of the geochronological data shows the isis expanded 34 0 25 3ka accelerating into the celtic sea to reach maximum limits 25 3 24 5ka before a collapse with rapid marginal retreat to the northern irish sea basin isb this retreat was rapid and driven by climatic warming sea level rise mega tidal amplitudes and reactivation of meridional circulation in the north atlantic the retreat though rapid is uneven with the stepped retreat pattern possibly a function of the passage of the ice stream between normal and adverse ice bed gradients and changing ice stream geometry initially wide calving margins and adverse slopes encouraged rapid retreat 550m a 1 that slowed 100m a 1 at the topographic constriction and bathymetric high between southern ireland and wales before rates increased 200m a 1 across adverse bed slopes and wider and deeper basin configuration in the northern isb these data point to the importance of the ice bed slope and lateral extent in predicting the longer term 1000 a patterns and rates of ice marginal retreat during phases of rapid collapse which has implications for the modelling of projected rapid retreat of present day ice streams copyright 2013 john wiley sons ltd

evidence from the rio bayo valley on the extent of the north patagonian icefield during the late pleistocene holocene transition abstract this paper presents data on the extent of the north patagonian icefield during the late pleistocene holocene transition using cosmogenic nuclide exposure age and optically stimulated luminescence dating we describe geomorphological and geochronological evidence for glacier extent in one of the major valleys surrounding the north patagonian icefield the rio bayo valley geomorphological mapping provides evidence for the existence of two types of former ice masses in this area i a large outlet glacier of the north patagonian icefield which occupied the main rio bayo valley and ii a number of small glaciers that developed in cirques on the slopes of the mountains surrounding the valley cosmogenic nuclide exposure age dating of two erratic boulders on the floor of the rio bayo valley indicate that the outlet glacier of the icefield withdrew from the rio bayo valley after 10 900 1000 yr the mean of two boulders dated to 11 400 900 yr and 10 500 800 yr single grain optically stimulated luminescence osl dating of an ice contact landform constructed against this glacier indicates that this ice mass remained in the valley until at least 9700 700 yr the agreement between the two independent dating techniques osl and cosmogenic nuclide exposure age dating increases our confidence in these age estimates a date obtained from a boulder on a cirque moraine above the main valley indicates that glaciers advanced in cirques surrounding the icefield some time around 12 500 900 yr this evidence for an expanded north patagonian icefield between 10 900 1000 yr and 9700 700 yr implies cold climatic conditions dominated at this time

compositional variations of the lunar crust results from radiative transfer modeling of central peak spectra 1 we present model mineralogy of impact crater central peaks combined with crustal thickness and crater central peak depth of origin models to report multiple perspectives of lunar crustal composition with depth here we report the analyses of 55 impact crater central peaks and how their compositions directly relate to the lunar highlands sample suite a radiative transfer model is used to analyze clementine visible plus near infrared spectra to place compositional constraints on these central peak materials central peaks analyzed are dominantly magnesian and plagioclase poor strong compositional similarities to lunar mg suite materials are evident relative to crustal thickness estimates central peak mineralogy becomes more plagioclase rich as the crust thickens relative to the crust mantle boundary the origin of peaks with dominantly mafic mineralogy are confined to the lower crust and primarily within the south pole aitken and procellarum kreep terranes pkt additionally central peaks with anorthositic mineralogy 60 vol plagioclase are transported to the surface from all depths in the crustal column and confined to the feldspathic highlands terrane fht the discovery of mafic and magnesian materials consistent with mg suite rocks of the sample collection in all lunar terranes suggests that the process and sources that give rise to these types of rocks is not unique to the pkt and not necessarily dependent on incompatible elements for formation the identification of ferroan and magnesian anorthositic material near the crust mantle boundary of the fht is also inconsistent with an increasing mafic feldspar ratio and mg with depth in the crust

characteristics of aeolian grain transport over a fluvio glacial lacustrine braid delta lake tekapo new zealand this paper presents results from one of the few scientific studies to examine the physical characteristics of aeolian sediment transport in an alpine area where topographically reinforced foehn winds initiate dust storm events the major objective of this study is to improve knowledge of aeolian processes in mid latitude alpine regions experiencing extreme wind speeds of particular interest is the role of surface characteristics in contributing to the unusually deep saltation layer which is seen to form over fluvio glacial deposits in the southern alps of new zealand sediment was collected at several heights 0 5 1 2 and 4 m and locations over a large alpine braided river delta and standard laboratory techniques used to examine grain size characteristics an image processing technique was also used to evaluate grain roundness grains filtered from the airstream at 0 5 m and 1 m above such surfaces were found to display a mean grain size of approximately 300 to 435 m resembling grain size characteristics of saltation clouds previously observed in high latitude cold climate locations in contrast to desert and prairie environments samples collected at 2 and 4 m above the surface were found to consist of 60 to 65 per cent sand sized material with some grains exceeding 1 1 5 mm in diameter grain shape analysis conducted on silt and clay sized grains filtered from the airstream above mixed sand and gravel surfaces showed such grains to display an increase in grain roundness with height this characteristic is thought to reflect the airstream s shape sorting ability and has important implications with respect to the often observed increase in grain roundness in aeolian deposits with increasing distance from source areas namely if more rounded grains are preferentially carried higher into the airstream and therefore into regions of higher wind speed they should theoretically be transported further from the entrainment zone before being deposited the high wind speeds observed often exceeding 30 m s 1 are seen to transport significantly larger sediment than reported in the literature for desert and prairie environments in addition the mixture of grain sizes and especially the pebble and cobble sized clasts that dominate the fluvio glacial deposits associated with the braided rivers in this mountain region also appear to increase significantly the trajectory height of saltating sand grains as a result of these two factors the depth of the saltation cloud often exceeds 1 m observations made in this study therefore highlight the need for field and laboratory aeolian process studies to be extended to examine grain transport over coarse grained beds during much higher wind velocities than typically reported in the literature such studies would provide a valuable insight into aeolian processes in high latitude altitude environments such as loess genesis 1997 by john wiley sons ltd

from morphostratigraphy to geochronology on the dating of ice marginal positions abstract this study focuses on the glacial landscape of northern germany as a part of the southwestern sector of the scandinavian ice sheet sis as it has a research history reaching back about 130 years since the glacial theory replaced the drift theory in the late 19th century it has experienced a number of key changes including the introduction of the concept of polyglaciation or the differentiation of ice advances within one glaciation which is closely linked to the morphostratigraphical definition of ice marginal positions with the development of numerical dating methods the rather static morphostratigraphically based chronologies which are deeply rooted in research history have been confronted with a growing number of geochronometrical data obtained from glacigenic deposits in order to date ice marginal positions the two most commonly used dating methods for that purpose are optically stimulated luminescence osl and surface exposure dating of erratic boulders this study highlights the dependency of the significance of results from different dating methods on the sampling position within the geomorphological framework results from osl and surface exposure dating for the same ice marginal position in theory cannot be the same as the methods date different processes in the development of the glacial landscape osl dating of fluvioglacial sandur sediments dating the process of active sedimentation at the ice front and surface exposure dating of boulders on end moraines dating the process of stabilisation of end moraines after the retreat of the ice front often qualify as the most useful combination of techniques in order to define a time interval for the formation of the landforms at a specific ice marginal position methodological drawbacks which might occur unfortunately tend to widen the process induced offset between osl and surface exposure ages incomplete bleaching of fluvioglacial sediments might cause an offset towards a maximum osl age for an ice marginal position whereas delayed stabilisation or post exposure relocation of boulders might cause a shift towards a minimum age of key importance are the influence of periglacial processes and the effects of melting of buried ice on landform stabilisation which remain to be quantified a possible solution to this problem combining osl and surface exposure dating is suggested in this study nevertheless the possibility exists to date different geomorphological processes by applying different dating methods to glacigenic deposits this allows for a differentiated reflection of morphostratigraphically based chronologies against the background of the modern concept of dynamic ice sheets in contrast to the traditional morphostratigraphical definition of ice marginal positions a time based definition is proposed because it offers the possibility of a more detailed reconstruction of ice sheet dynamics at a certain point in time

luminescence dating of glacial advances at lago buenos aires 46 s patagonia abstract understanding the timing of past glacial advances in patagonia is of global climatic importance because of the insight this can provide into the influence on glacier behaviour of changes in temperature and precipitation related to the southern westerlies in this paper we present new luminescence ages determined using single grains of k feldspar from proglacial outwash sediments that were deposited by the patagonian ice sheet around lago buenos aires 46 s east of the contemporary northern patagonian icefield the new luminescence ages indicate that major outwash accumulations formed around 110 20 ka to 140 20 ka and that these correspond to the moreno i and ii moraine ridges which were previously dated using cosmogenic isotope dating to 150 30 ka luminescence dating at lago buenos aires has also identified outwash sediments that were deposited during glacial advances 30 8 5 7 ka and 34 0 6 1 ka mis 3 that are not recorded in the moraine record younger outwash accumulations were then deposited between 14 7 2 1 and 26 2 1 6 ka which correspond to the fenix i v moraine ridges the combined chronology suggests that glacial advances occurred 110 20 ka to 150 30 ka mis 6 30 8 5 7 ka to 34 0 6 1 ka mis 3 and 14 7 2 1 to 26 2 1 6 ka mis 2 at lago buenos aires overall luminescence dating using single grains of k feldspar has excellent potential to contribute towards the ever increasing geochronological dataset constraining the timings of glacial advances in patagonia

extensive glacial advances during the last glacial maximum near the eastern himalayan syntaxis abstract climatically the eastern himalaya are mainly controlled by the indian summer monsoon ism and important region for understanding the relationship between ism and glacial change this region is therefore useful for studies of the relation between glacial changes and ism using a geomorpho stratigraphic method combined with gis we investigated and mapped the outmost lateral frontal moraine of the most extensive glaciations that occurred in the basongcuo bsc catchment near the eastern himalayan syntaxis using optically stimulated luminescence osl and 10 be surface exposure dating technique we dated five boulders and 23 sediment samples the resultant osl and 10 be ages show that the region s glaciers were at their most extensive positions between 16 and 31 ka glacial coverage was 507 5 km 2 9 9 times greater than it is today 51 5 km 2 with an equilibrium line altitude ela depression of 690 m the rapidity with which the last glacial maximum lgm glacial advance and retreat occurred suggests that temperature was the dominant control on glacial change

climate forcing and the initiation of glacier advance during mis 2 in the north sikkim himalaya india abstract the present study investigates the relics of the most extensive glacier advances and their retreat in the transitional climatic zone of the chopta valley northern sikkim himalaya with an aim to understand the forcing factors the optically stimulated luminescence osl dating of the stratigraphically oldest glacier advance and its retreat in the chopta valley revealed that the glacier advanced at 28 2 8 ka and sustained through the global last glacial maximum glgm 26 5 ka and 19 ka mix et al 2001 the deglaciation is manifested by recessional moraine ridge dated at 18 2 2 ka comparing the results of the present study with the existing glacial chronologies from the himalayan region it has been observed that irrespective of the geographical locations the intensified mid latitude westerlies during the glgm and the associated decrease in winter temperature was the major driver of glacier advance during the mis 2

optical dating of holocene sediments from a variety of geomorphic settings using single grains of quartz this paper presents an improved method for the optical dating of holocene sediments from a variety of geomorphic settings we have measured the equivalent dose de in individual grains of quartz using green laser light for optical stimulation and have simulated the de distributions for multiple grain synthetic aliquots using the single grain data for 12 samples of known independent age we show that application of a minimum age model to the single grain and small 10 grain aliquot de data provides the most accurate estimate of the burial dose for nine of the samples examined 3 aeolian 5 fluvial and 1 marine the weighted mean de as obtained using the central age model gives rise to burial age overestimates of up to a factor of 10 for these nine samples whether single grains small aliquots or large 100 grain aliquots are used for the other three samples two aeolian and one fluvial application of either the minimum age model or the central age model to the single grain small aliquot and large aliquot de data yields burial ages in accord with the independent age control we infer that these three samples were well bleached at the time of deposition these results show that heterogeneous bleaching of the optical dating signal is commonplace in nature and that aeolian transport offers no guarantee that the sample will be well bleached at the time of deposition we also show that grains sensitive to infrared ir stimulation can give rise to low de values which will result in significant underestimation of the burial dose and hence of the age of deposition we demonstrate that use of a modified single aliquot regenerative dose protocol incorporating ir stimulation prior to green light stimulation deals effectively with contamination by ir sensitive grains we conclude that application of the modified protocol to single grains or small aliquots of quartz using the lowest de population to estimate the burial dose is the best means of obtaining reliable ages for holocene sediments from a wide range of depositional environments d 2003 elsevier b v all rights reserved

luminescence dating of late pleistocene proximal glacial sediments in the olympic mountains washington abstract late pleistocene glacial sediments from the south fork hoh river valley in the olympic mountains washington usa were dated using optically stimulated luminescence osl on quartz sand high sediment supply typical of glacial environments short transport distances and sediment newly eroded from bedrock sources were expected to pose problems for luminescence dating samples were collected from five distinct sedimentary facies using approximated distances from the ice front to assess how luminescence results varied due to these factors and to determine which samples produced the most reliable age estimates results from the south fork hoh highlight the importance of transport environment and sedimentary facies on solar resetting sediments from better sorted ice distal environments were determined to be more completely bleached and more reliable for osl dating samples were collected as part of larger research goals to improve understanding of the glacial history of the south fork hoh river valley

rates of dust deposition between 50 ka and 20 ka revealed by osl dating at yuanbao on the chinese loess plateau abstract a new chronology has been constructed for an 18 m section of malan loess at yuanbao near linxia on the western edge of the chinese loess plateau the chronology has been obtained using the optically stimulated luminescence signal from coarse silt sized grains of quartz extracted from eighteen samples collected at approximately 1 m intervals down the section in the upper 9 m the dust deposition rate was 1 11 m ka covering the time period from 26 1 1 9 ka to 17 5 1 2 ka and there is no evidence of hiatus at this scale of analysis at greater depths the average rate of dust deposition is lower although there was a short period of higher deposition between 37 ka and 34 ka no large breaks 5 ka in deposition were deduced from the osl ages for the lower part of the loess section dating from 51 2 4 6 ka to 30 0 2 5 ka the age of the boundary at 9 1 m between the more uniformly deposited upper loess and the lower loess is compared to the age of the transition in the marine record between marine isotope stages 3 and 2 the chronological information at yuanbao is also used to challenge the previous use at this section of an age model based on changes in grain size

luminescence chronology of late quaternary moraines and last glacial maximum equilibrium line altitude reconstruction from parlung zangbo valley south eastern tibetan plateau optically stimulated luminescence dating was applied to samples from glacial sediments in the parlung zangbo valleys daba and charao of the south eastern tibetan plateau to better constrain the timing of late quaternary glaciation which is thought to have been linked to the indian monsoon the single aliquot regenerative dose protocol on quartz was used for equivalent dose d e determination using small aliquots for samples from the daba valley the comparison of ages using two grain size fractions middle 38 63 mu m and coarse 90 250 mu m were conducted the coarse grain ages in the daba valley p3 and charao valley p7 range from 16 4 to 26 0 ka and are consistent with previously published cosmogenic radionuclide exposure ages in the baiyu valley pb1 our dating results reveal that these moraines were formed during the last glacial maximum lgm we then reconstruct the past equilibrium line altitudes elas during the lgm for five glacial valleys in the study area which range from 3286 to 4014 m with an average value of 3730 m while the contemporary average ela is 4655 m after correction for terrain uplift about 8 m since the lgm the difference in the ela values between the lgm and today is 917 m according to these data the estimated temperature during the lgm is 6 3 degrees c lower than present for the parlung zangbo river valley copyright c 2014 john wiley sons ltd

reassessment of the record of linear dune activity in tasmania using optical dating abstract stabilized linear dunes in northeastern tasmania have previously been dated using luminescence signals from quartz duller g a t augustinus p 1997 luminescence studies of dunes from north eastern tasmania quaternary geochronology qsr 16 357 365 and gave ages from 44 4 to 29 3 ka unexpectedly no evidence was found for dune activity at the last glacial maximum lgm the ages were obtained using analytical methods available at the time including multiple aliquot methods in recent years the single aliquot regenerative dose sar procedure has been developed and this method gave ages from 23 8 1 6 to 21 8 1 3 ka for the same samples a further seven samples from other linear dunes in the area gave ages from 16 8 to 19 7 ka these ages are strong evidence that linear dunes in northeastern tasmania were last active at or immediately after the lgm consistent with evidence for enhanced aridity through large parts of the australian continent at that time earlier methods of optical dating using quartz did not explicitly check for changes in luminescence sensitivity and thus their reliability must be suspect for samples measured here the largest discrepancy in equivalent dose between the sensitivity corrected and non sensitivity corrected data is 84 while for the remainder it is much smaller these results demonstrate the importance of checking the validity of previously published optical dating results which were obtained using methods that did not explicitly check for sensitivity change

thermoluminescence dating of glacially transported sediments some considerations abstract theoretical considerations imply that the suitability of glacially deposited sediments for thermoluminescence tl dating will be influenced by transport routes within the ice and by facies of deposition measurments on sediments obtained from the austerdalsbreen glacier in western norway indicate that zeroing of sediment does not occur at the base of a valley glacier but that englacial and supraglacial sediments showed evidence of bleaching but not total zeroing analysis of sediments from recent glacial and fluvioglacial landforms showed no evidence that they had been zeroed prior to deposition results indicate that the tl age of glacial landforms will be a function of the derivation and travel paths of the sediments of which it is composed rather than of the form itself it is concluded that as knowledge of the rates of bleaching associated with various facies of transport and deposition of glacial sediments improves so the potential of the technique to act as a diagnostic sedimentological tool will increase even when dating of glacial deposits by tl is impossible

optically stimulated luminescence dating of a moraine and a terrace in laohugou valley western qilian shan northeastern tibet the qilian shan is one of the most important mountain ranges for understanding quaternary glaciation in the northeastern tibetan plateau however its western part is not well studied a moraine and an outwash terrace in the laohugou valley were mapped using geomorpho stratigraphy and dated by optically stimulated luminescence after analyzing the minimum age and central age of coarse and fine grained quartz most of the minimum ages for coarse grains are consistent with geomorpho stratigraphic sequence indicating they are closest to the true ages of the sediments the lateral moraine was initially formed at 20 2 2 6 ka during the last glacial maximum and was modified between 11 6 2 0 and 12 9 1 3 ka in the late glacial the outwash terrace was formed between 10 0 1 7 and 5 5 0 7 ka and coincides with temperature rise in the early holocene and the holocene optimum at its last glacial maximum the palaeo glacier was similar to 13 6 km long with an area of 45 3 km 2 4 3 km longer and 34 larger than the contemporary glacier the reconstructed palaeo glacier equilibrium line altitude ela was 4600 40 m or 140 m lower than the present ela the glacier advance in the laohugou valley was less extensive and ela depression was less than found in the eastern qilian shan during lgm and late glacial suggesting a drier climate during the last glacial c 2013 elsevier ltd and inqua all rights reserved

optical dating of young glacial sediments from the source area of the urumqi river in tianshan mountians northwestern china abstract incomplete bleaching which will lead to overestimation of age still remains one of the most significant problems in luminescence dating on glacial sediments in order to test the bleachability of luminescence signals of mountain glacial sediments nineteen young samples from different geomorphological positions and different sediment settings in the source area of the urumqi river in tianshan mountains a key area of quaternary glaciation study in china were collected and dated using optically stimulated luminescence osl dating methods equivalent dose d e was determined by quartz sar sgc procedures results show that most of the samples suffer from varying degrees of overestimation in general glaciofluvial and lateral moraine till samples show relatively low residual doses 0 20 5 gy while subglacial tills tills from terminal moraines ground moraines and hummocky moraines show higher residual doses 22 4 205 6 gy reworked loessic sediments exhibit surprisingly high residual doses 24 1 and 46 5 gy glaciofluvial and materials from lateral moraine upper part are recommended when sampling whereas those from subglacial tills terminal moraines ground moraines and hummocky moraines should be avoided

timing of the last interglacial in northern europe derived from optically stimulated luminescence osl dating of a terrestrial saalian eemian weichselian sedimentary sequence in ne germany abstract based on the results of palynological and geochemical analyses a sediment section near the village of vevais north eastern brandenburg is assumed to encompass a succession of saalian eemian and weichselian sediments and is expected to cover a time span from marine isotope stage mis 6 to mis 2 it is regarded as a key site for the study of the last interglacial cycle in north eastern germany palynological analyses had revealed an almost complete record of the eemian mis 5e preserved within a succession of lake marls exposed in the sediment sequence but results from numerical dating methods were still missing within this study five samples from sand layers within the profile have been analyzed using luminescence dating techniques in order to set up a geochronometrical time frame for the eemian interglacial first results from optically stimulated luminescence osl dating of quartz showed severe age underestimation of some samples with regard to their relative stratigraphical position to the eemian lake marls radionuclide analyses revealed disequilibria within the 238u decay chain and inconsistencies concerning the 40k content for most of the samples in order to overcome these dosimetric problems additional infrared stimulated luminescence irsl and post infrared yellow osl post ir yosl measurements from feldspar were conducted and a subtraction dating method was successfully applied hence it was for the first time possible to set up a time frame for the eemian interglacial inferred from luminescence dating techniques of a terrestrial sedimentary archive in north eastern germany the onset of the eemian was dated to 126 16 ka the termination and beginning transition from the eemian to the weichselian cold stage was dated to 108 9 7 8 ka these results are in excellent agreement with the marine isotope record as well as with the results of the analysis of the continuous varve record of lago grande di monticchio with a period of 17 7 0 2 ka from the onset at 127 2 1 6 ka bp for the eemian interglacial

dating the quaternary progress in luminescence dating of sediments abstract luminescence dating comprises a collection of numerical age techniques that are among the most significant chronological tools currently used in quaternary research this paper briefly reviews the key historical developments in luminescence dating from its roots in thermoluminescence dating of heated minerals to the development of optical dating methods for sunlight exposed sediments we describe the principles and practicalities of the various techniques commonly used in luminescence dating including multiple aliquot single aliquot and single grain procedures and we discuss some of the latest approaches to recognising and minimising potential errors in age estimation e g by means of component analysis and dose distribution methods in optical dating the overview also introduces the other papers in this special issue of quaternary science reviews which address a selection of important issues in basic research technique development and application of luminescence dating to critical questions in the geological and archaeological sciences illustrated with examples from around the world and the last million years of earth history

historical tsunami deposits in peru sedimentology inverse modeling and optically stimulated luminescence dating the entire coast of peru was surveyed to document deposits of historical tsunami evidence of four tsunami was found at puerto casma in northern peru a graded heavy mineral rich layer with shell and rock fragments was detected osl dating revealed an age of 0 37 0 03 ka 1615e1667 ad inverse modelling of tsunami onshore flow parameters indicates a flow depth of w 6ma nd aflow speed of w8 m s at a distance of w60 m from the shoreline for the chimbote earthquake of 1619 ad a tsunami was not listed in the historical tsunami catalogues although it is seen as a predecessor of the 1996 chimbote earthquake and tsunami hence this study may provide the first evidence of a local tsunami triggered by this event a graded shell rich event layer that contains cobbles with attached marine organisms was found at vila vila in southern peru this layer was dated to 0 17 0 04 ka 1797e1871 ad and is most probably the result of the 1868 arica tsunami two additional event layers found in boca del rio southern peru were dated 2 26 0 37 ka 615 bce119 ad and 1 98 0 23 ka 207 bce255 ad thus the layers record for the first time tsunami much older than the events listed in tsunami catalogues these two events exhibit similar parameters with flow speeds of 7e8 m s and depths of 6 m in a distance of 460 m from the present shoreline the time that passed between the events is similar to the recurrence interval of the two arica tsunami of 1604 and 1868 ad hence giving evidence of another prehistoric earthquake and tsunami couplet

high resolution chronologies for loess comparing ams 14c and optical dating results the nuxloch loess section in south west germany is famous in central europe for its thick deposits from the last glacial maximum it has therefore been intensively studied during the past few years and offers an excellent opportunity to compare the performance of different dating techniques covering the period 15 45 ka here we present results fromoptical and ams 14 c dating the silt sized polymineral fraction of the clastic sediments and a multiple aliquot approach was used for ir osl dating 14 c dating was carried out on organic macro remnants and humin fractions extracted fromthe sedim ents with the exception of samples taken from the uppermost 1 5 m of the section ir osl and calibrated 14 c ams ages are consistent over the entire period the inconsistencies in the upper meters are thought to be due to disturbances during soil formation in the holocene the good agreement obtained on the remaining sequence demonstrates the high accuracy of both methods when studying loess sections for the ir osl ages no significant age underestimations are obvious the results clearly document that accurate chronologies can be developed for such continental sedimentary sequences this gives access to archives that can now be studied with a high temporal resolution and allows the establishment of new paleoclimatic proxies for the study of terrestrial responses to past climatic changes r 2003 elsevier science ltd all rights reserved

quaternary glacial chronology of the kanas river valley altai mountains china the kanas river originates on the southern slope of youyi peak the largest center of modern glaciation in the altai mountains in central asia glaciers advanced and retreated repeatedly during quaternary glacialeinterglacial cycles in the kanas river valley and four moraine complexes and associated glaciofluvial deposits are preserved in the valley optically stimulated luminescence osl dating has been used to determine ages of glaciofluvial deposits sand lenses sandwiched between tills in moraines using a single aliquot regenerative dose sar protocol based on dating results from this and previous studies including 14 c electron spin resonance esr and osl dates and geomorphic relationships the innermost moraine complex was concluded to deposit during the little ice age lia the second akekule moraine complex was deposited during the neoglacial the third kanas moraine complex was deposited during the last glacial cycle marine oxygen isotope stage mis 2e4 and the outermost set of moraines is mis 6 in ages penultimate glaciation the kanas moraine complex could be divided into three subsets iii1 iii2 and iii3 with inferred ages of mis 2 mid mis 3 and mis 4 respectively which is consistent with moraine records from other areas in central asia and climate reconstructions from the guliya ice core the glaciers in the kanas valley at their maximum extents during the lia neoglacial last glaciation and penultimate glaciation were 13 8 km 32 km w100 km and w120 km long respectively

measurement of equivalent doses in quartz from contemporary water lain sediments using optically stimulated luminescence the single aliquot technique and its derivatives are very attractive for the measurement of the very small doses found in young materials because they inherently avoid concerns about low dose non linearity and can offer high precisions a modification is outlined to the single aliquot regeneration and added dose sara protocol mejdahl and botter jensen 1994 quaternary geochronology quaternary science reviews 13 551 5541 to permit its application to sedimentary quartz using the optically stimulated luminescence signal this revised protocol is then used to determine the doses found in several contemporary fluvial sediments and one coastal beach sand thought to be deposi ted by recent wave action two over bank river deposits were both homogeneously well bleached with doses of 0 4 gy although most of the grains in three channel deposits from a range of catchment sizes were also well bleached contamination by a small proportion of very poorly bleached quartz grains prevented the measurement of the dose in the majority the beach deposit was homogeneously bleached and contained a dose of about 0 02 gy it is concluded that over bank sites may provide accurate dates for samples older than a few hundred years but that the heterogeneity of the channel sites limits the accuracy of dates less than a few thousand years

ubiquity of anomalous fading in k feldspars and the measurement and correction for it in optical dating anomalous fading rates were measured in k feldspars separated from 49 sediment samples mainly from north america the intensity of the optically stimulated luminescence was found to decrease linea

luminescence dating of glaciofluvial deposits linked to the penultimate glaciation in the eastern alps during the penultimate glaciation vast areas of the alps were glaciated with piedmont glaciers protruding into the foreland in the easternmost part of the northward draining valleys of the alps the glaciers did not reach the foreland but formed valley glaciers confined by the mountainous terrain this also applies to the ybbs valley where samples for luminescence dating out of glaciofluvial gravel accumulations were taken at three locations along the present day river course in a highly dynamic depositional environment such as a glacier fed river system incomplete resetting of the luminescence signal is possible in particular when transport distances are short in such cases quartz usually is the preferred mineral over feldspar especially if dose rates are low and may theoretically allow obtaining quartz ages beyond 150 ka because previous research has shown and as corroborated within this study quartz from the research area exhibits analytical problems in the high age range therefore luminescence properties of coarse grain 100 200 m quartz and in addition k rich feldspar were investigated with the aim to reconstruct the chronology of the glacial processes within the ybbs catchment area issues of incomplete bleaching were pirir225 encountered and addressed by comparing quartz osl fading corrected k feldspar ir50 and pirir225 to identify reliable ages depositional ages based on quartz osl and feldspar pirir225 signals revealed deposition of ice marginal kame terraces and glaciofluvial foreland terraces during late to middle mis 6 in combination with results from previous studies we could reconstruct the valley evolution during the riss glaciation newly gained luminescence ages of the deglaciation in the easternmost alps coincide with osl dated deglaciation events in the western alps indicating that climatic change along the north side of the alps happened simultaneously

geochronology and geomorphology of the jones point glacial landform in lower hudson valley new york insight into deglaciation processes since the last glacial maximum abstract the glacial deposits at jones point located on the western side of the lower hudson river new york were investigated with geologic geophysical remote sensing and optically stimulated luminescence osl dating methods to build an interpretation of landform origin formation and timing osl dates on eight samples of quartz sand seven single aliquot and one single grain of quartz yield an age range of 14 27 ka for the proglacial and glaciofluvial deposits at jones point optical age results suggest that jones point deposits largely predate the glacial lake albany drainage erosional flood episode in the hudson river valley ca 15 13 ka based on this data we conclude that this major erosional event mostly removed valley fill deposits leaving elevated terraces during deglaciation at the end of the last glacial maximum lgm our analysis supports the earlier 15 ka date for the flood occurrence and suggests that more recent overlying glaciofluvial deposits formed in the lee side of the jones point promontory

glacial advances and stability of the moraine dam on mount namcha barwa since the last glacial maximum eastern himalayan syntaxis abstract the tibetan plateau and indian plain exhibit the largest altitudinal difference between two geographically contiguous areas on earth but the eastern margin of the plateau has not experienced headward erosion of the yarlung zangbo river yzr since 2 5 ma in the past some scientists have argued that moraine dams on mount namcha barwa in the eastern himalayan syntaxis frequently blocked the yzr thus keeping the plateau s margin intact at this point in this study three sets of moraines were identified in the pai valley alongside namcha barwa and were dated using optically stimulated luminescence osl and 10be exposure dating the resultant ages would suggest that three glaciations occurred at 22 2 4 7 and 1 3 ka respectively comparison of osl and 10be ages for glacial advances with local paleoclimatic proxies would suggest that temperature was the dominant factor controlling glacial change because of the paleoglacial advance frequency coupling with rapid fluvial incision moraine dams were cut through by the yzr thus any moraine dams that lost their efficacy in impacting upon knickpoint migration instead similarities between rock uplift and fluvial incision rather than moraine dams might have been the main control impeding headward erosion of the yzr thereby keeping this part of the eastern tibetan plateau margin intact

timing and style of late quaternary glaciation in the eastern hindu kush chitral northern pakistan a review and revision of the glacial chronology based on new optically stimulated luminescence dating abstract glacial landforms and sediments provide evidence for two late quaternary major glaciations in the eastern hindu kush new optically stimulated luminescence osl dating was undertaken to define the timing of these glaciations and associated sediment deposition the drosh glacial was defined by osl dating to have occurred during marine isotopic stage 3 producing an extensive valley glaciation that extended to an altitude of 1300 m above sea level asl in the main valley with an equilibrium line altitude ela depression of 1200 m the pret glacial produced a valley glaciation that extended to an altitude of 1670 m asl in the main valley with an ela depression of 1000 m the new osl dating suggests that this glacial stage probably represents several glacial advances that occurred during the latter part of the last glacial moraines representing two minor glacial advances the shandur and barum glacial stages were also recognized near the contemporary glaciers these probably formed during the middle late holocene and little ice age respectively this study and comparisons with adjacent regions suggest that there was limited glaciation during the global last glacial maximum lgm in the hindu kush deglaciation in the mountain ranges of the himalayas and the consequent meltwater discharge into the adjacent seas was negligible immediately after the global lgm and it was therefore of minor importance as a forcing factor for global climate change during the end of the last glacial cycle however our studies show that glaciation and particularly deglaciation is important in controlling the deposition of thick valley fills and the landscape evolution of the high mountain environments

delineating stratigraphic breaks at the bases of postglacial eolian dunes in central alberta canada using a portable osl reader temporal constraints for the late pleistocene deposition of eolian dunes that occur in central and northern alberta canada can be provided by dating sediments from the dune bases using luminescence techniques in places however the postglacial dunes overlie glaciofluvial sands that resemble the eolian deposits in texture such that demarcating the bases of the dunes is often problematic in this study we address the problem by employing a portable optically stimulated luminescence osl reader to construct luminescence profiles that depict luminescence signal variation with depth with the portable osl reader measurement can be performed on bulk sediments negating the need for laborious separation procedures to isolate pure mineral fractions as is required in regular luminescence dating measurements can also be carried out in the field permitting quicker decision making during sample collection results from this study presented as depth variations of feldspar derived infrared stimulated luminescence irsl signals and predominantly quartz generated post ir blue osl signals show that luminescence profiling enables one to distinguish between eolian deposits that make up the dunes from the underlying non eolian sands the identification of such cryptostratigraphic interfaces is made possible by differences in the dosimetric histories of the sediments the delineation of the dune bases allows targeted sampling that yields best luminescence age approximations for the initiation of postglacial eolian deposition in the region luminescence profiling of eolian sequences would also in theory permit the identification of depositional breaks of extended duration copyright 2012 john wiley sons ltd

optical and tl dating on glaciofluvial sediments abstract three glaciofluvial sediment samples from the yukki area near leningrad were studied in order to compare and combine results from optical and thermoluminescence tl dating the formation of the sediments can be related to the end of the last deglaciation of the area and thus the age is around 13 ka two of the samples were collected from a kame ridge where a rapid sedimentation process and consequently poor bleaching of the sediments can be assumed and one sample was collected from a terrace with slower sedimentation poor tl plateaux reflect this situation and tl dating of the sample was not fruitful the result from optical dating of the kame samples led to ages that were far too high but for the terrace sample the optical age of 16 ka is quite realistic it is proposed that when optical dating of rapidly accumulated glaciofluvial sediments is attempted tl plateau tests should be used to estimate whether the duration of bleaching at deposition had been adequate to achieve a sufficiently low residual signal

luminescence dating of glaciofluvial deposits a review abstract for glacigenic sediments optically stimulated luminescence osl dating offers an opportunity to date the time of deposition of quartz and feldspar minerals that are ubiquitous within the sediment matrix rather than relying upon the chance occurrence of organic material for radiocarbon dating the osl dating signal or charge accumulates in crystal defects of individual quartz and feldspar minerals through exposure to environmental radiation within their depositional setting the osl signal within individual grains can be reset or bleached through exposure to daylight during transportation processes thus osl dating of sediments attempts to determine the time elapsed since burial glacigenic sediments present considerable challenges for osl dating not only in terms of poor bleaching of the osl signal during the transport and deposition cycle but also poor quartz luminescence characteristics which are often related to sediment provenance the nature of the bedrock or source material and the freshly eroded nature of many such deposits this paper reviews luminescence dating techniques as applied to glaciofluvial sediments and explores the challenges that such deposits present to the technique successful application of osl techniques can be judged in a number of ways comparison with the independent chronologies is prevalent in the literature but recently the movement towards measurement of large numbers of small aliquots and single grains allows a more robust assessment of luminescence properties and behaviour for individual samples and ultimately more precise luminescence ages to be determined for glaciofluvial sediments in particular it is important to investigate the depositional sub environment of each sample in relation to the chance of sufficient bleaching during transport and deposition a lithofacies based approach to sampling for optically stimulated luminescence dating of these sediments is suggested whereby hypothetically well bleached deposits are targeted after a detailed investigation into possible environments of deposition this approach together with small aliquot single grain analysis methodologies should further enhance the likelihood of obtaining a sufficiently bleached sample for osl dating

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

a solution to anomalous fading and age shortfalls in optical dating of feldspar minerals abstract recent reports of age underestimations for events of interest in both palaeoclimatology and archaeology have led to questioning the validity of using luminescence for dating sediments the commonly designated culprit is anomalous fading of feldspar luminescence we investigated the differential fading rates of single feldspar grains in sediment samples from different geological domains of north america and deduced how one could extrapolate to zero fading this is shown to resolve an extreme case of optical age underestimation documented for the late pleistocene norfolk formation a key palaeoclimate stratigraphic unit exposed along the north american atlantic coast

luminescence dating of the last weichselian glacier advance in east greenland abstract we have studied fluvial and deltaic sediments that accumulated at the margin of a fjord during the flakkerhuk stade when the last major glaciers advanced and retreated in the scoresby sund region east greenland the sediments have been dated using the optically stimulated luminescence of quartz and as a control on the technique those sediments deposited after deglaciation were also dated using 14 c we conclude that the last glacier build up began much earlier than previously suggested our data indicate the existence of a more or less stable ice cover for a period of c 50 ka this is consistent with the record of ice rafted detritus on the continental slope off the scoresby sund fjord complex and suggests that the glacier had a polar regime with little surface melting or basal slide

unprecedented last glacial mass accumulation rates determined by luminescence dating of loess from western nebraska abstract a high resolution chronology for peoria last glacial period loess from three sites in nebraska midcontinental north america is determined by applying optically stimulated luminescence osl dating to 35 50 m quartz at bignell hill nebraska an osl age of 25 000 yr near the contact of peoria loess with the underlying gilman canyon formation shows that dust accumulation occurred early during the last glacial maximum lgm whereas at devil s den and eustis nebraska basal osl ages are significantly younger 18 000 and 21 000 yr respectively at all three localities dust accumulation ended at some time after 14 000 yr ago mass accumulation rates mars for western nebraska calculated using the osl ages are extremely high from 18 000 to 14 000 yr much higher than those calculated for any other pre holocene location worldwide these unprecedented mars coincide with the timing of a mismatch between paleoenvironmental evidence from central north america and the paleoclimate simulations from atmospheric global circulation models agcms we infer that the high atmospheric dust loading implied by these mars may have played an important role through radiative forcing in maintaining a colder than present climate over central north america for several thousand years after summer insolation exceeded present day values

landscape change and its influence on human activities in lhasa basin of central tibetan plateau since the last deglacial abstract human activity and adaptation to the environmental changes on the tibetan plateau are under debate lhasa is the political and economic center of the tibetan autonomous region and was founded in 633 ce the potential influence of changes in the landscape on the city s development remains unclear in this paper optically stimulated luminescence and radiocarbon dating techniques were applied to determine the ages at which landforms have changed since the last glacial maximum combining these results with archaeological evidence taken from two sites changguogougou and qugong in the lhasa area the relation between river migration and human adaptation was discussed the results showed that the two terraces t1 and t2 of the lhasa river are fill and fill cut terraces and that these were formed after 0 9 ka and 0 08 cal ka bp respectively land below an altitude of 3650 m above sea level was lower than the contemporary river level before 0 9 ka with the down cutting of the lhasa river more land became available for habitation and the flood risk to the city was also reduced the sediments of the lower land around the changguogou area appear to be composed of fluvial lacustrine facies during the last glacial maximum to late glacial period humans occupied the changguogou area between 3 255 and 3 059 cal ka bp when there was weaker aeolian activity and abandoned this area when aeolian activity increased

optical dating of sediments a new method for dating sediments is proposed which determines the time since the sediment was last exposed to sunlight an argon ion laser is used to excite electrons from thermally stable light sensitive traps and the subsequent luminescence used as a measure of the past radiation dose two sample sequences spanning the periods 0 700 kyr and 0 6 kyr show steadily increasing luminescence with age an age of 62 8 kyr is obtained for a silt radiocarbon dated at 58 8 0 3 kyr problems were found with two much younger samples

thermoluminescence dating of the british coversand deposits abstract coversand deposits thought to be of lateglacial age are found in britain in north lincolnshire south west lancashire and central east anglia a comprehensive dating study of them using thermoluminescence tl techniques is currently underway in an attempt to link the british coversand deposits to the european coversand chronology initial results from four of the british coversand sites sampled are presented the 26 tl dates from 14 samples show that in lincolnshire aeolian deposition took place from 12 5 ka to i1 ka cessation of the initial sand deposition was synchronous with this in lancashire but sand deposition occurred significantly earlier in east anglia the upper layers of aeolian sand in lancashire are much younger and are attributed to holocene reworking on the basis of these dates lincolnshire and lancashire coversand deposition occurred at a similar time to the younger coversand ii whilst east anglian coversand deposition coincided with the younger coversand i phase in the european coversand chronology

a climatic trigger for catastrophic pleistocene holocene debris flows in the eastern andean cordillera of colombia the geomorphology and stratigraphy of massive debris flows on the eastern andean cordillera colombia indicate two distinct deposits can be recognized the lower chinauta deposit covers 14 km2 and has a thickness of 60 m whereas the upper fusagasuga deposit covers 20 km2 and has a thickness of 20 m the lower chinauta section consists of matrix supported gravels with isolated boulders and massive to moderately bedded structure and local inverse grading the upper section displays sequences of inversely graded clast supported gravels with boulders 2 m in axial length capped by massive matrix supported fine gravels the latter are dissected by coarse channelized gravels we interpret these facies as a series of debris and hyper concentrated flows dissected by river channels the fusagasuga deposit is dominated by massive to inversely graded matrix supported gravels with isolated boulders single grain optically stimulated luminescence dates of the sandy silty matrix of debris and hyper concentrated flows constrain the timing of deposition of the chinauta debris flow deposits between 38 9 and 8 7 ka we postulate that millennial scale climate variability is responsible for causing these massive debris flows through a combination of elevated temperatures and increased rainfall that triggered runoff and sediment transport

some remarks about a new last glacial record from the western salzach foreland glacier basin southern germany the amount of glacial advances into the alpine foreland during the pleistocene is still a matter of discussion the big four glaciations of the classical approach were originally derived from outwash sequences from glacial basins only very few long records and studies are known in the context of a geological mapping programme of the bavarian environment agency a research drilling through the salzach foreland glacier area was undertaken continuous coring reached the base of the glacial basin sequence 117 m below surface geological and geophysical logging pollen sampling and dating attempts of core material were conducted while age constraints for the lower part of the sequence are still uncertain the upper part can be ascribed to the last glacial cycle the interpretation of diamictons from the early part of the last glacial cycle is discussed a validation compared to other stratigraphic observations and interpretations from northern alpine quaternary records is presented

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

the distribution of apparent dose as determined by optically stimulated luminescence in small aliquots of fluvial quartz implications for dating young sediments abstract we noted recently murray et al 1995 that quartz samples taken from in channel fluvial deposits have apparent doses ranging over several orders of magnitude we suggested that these dose distributions are best explained by a mixture of a small number of poorly bleached grains and a larger number of well bleached grains in this paper we examine the distribution of apparent dose in small aliquots each composed of 2000 grains of different particle size fractions 63 90 m 90 125 m 125 180 m 180 212 m 212 250 m diameter from two samples collected from the murrumbidgee river new south wales australia the samples are of known burial age the first being 70 years old and the second being its modern equivalent 0 2 gy the difference in the lowest apparent dose in the two samples is considered to be the result of their different burial times we suggest a method for dating recently deposited

fluctuations in the thermoluminescence signal of suspended sediment in an alpine glacial meltwater stream abstract analysis of the thermoluminescence tl signal from suspended sediment samples from the dora di ferret river in northern italy reveals two scenarios for entrainment transport and bleaching of the tl signal in clear weather a simple diurnal fluctuation in luminescence intensity is apparent but the correlation with sediment concentration in the stream is very low storm events in contrast cause large amounts of unbleached sediment to be mobilised and entrained in the flow producing a significant positive correlation between tl intensity and sediment concentration such storm events may be identified by an initial dip in the intensity of the tl signal believed to be due to zeroed grains on the surface of valley slopes being washed off the slopes followed by a major rise in signal as erosion starts to incorporate previously unbleached sediment into the flow

the timing of linear dune activity in the strzelecki and tirari deserts australia abstract linear dunes occupy more than one third of the australian continent but the timing of their formation is poorly understood in this study we collected 82 samples from 26 sites across the strzelecki and tirari deserts in the driest part of central australia to provide an optically stimulated luminescence chronology for these dunefields the dunes preserve up to four stratigraphic horizons bounded by palaeosols which represent evidence for multiple periods of reactivation punctuated by episodes of increased environmental stability dune activity took place in episodes around 73 66 35 32 22 18 and 14 10 ka intermittent partial mobilisation persisted at other times throughout the last 75 ka and dune activity appears to have intensified during the late holocene dune construction occurred when sediment was available for aeolian transport in the strzelecki and tirari deserts this coincided with cold arid conditions during marine isotope stage mis 4 late mis 3 and mis 2 and the warm dry climates of the late pleistocene holocene transition period and late holocene localised influxes of sediment on active floodplains and lake floors during the relatively more humid periods of mis 5 also resulted in dune formation the timing of widespread dune reactivation coincided with glaciation in southeastern australia along with cooler temperatures in the adjacent oceans and antarctica

luminescence dating of quaternary sediments in the himalaya and high asia a practical guide to its use and limitations for constraining the timing of glaciation abstract knowledge of the glacial history of high asia is of critical importance for scientific understanding of the palaeoclimate of this region the lack of absolute age controls on glacial landforms of the himalaya and high asia region is arguably the greatest problem facing the construction of a history of quaternary glaciation in these areas a major reason for this lack of dates has been the absence of a suitable dating method this paper reviews the use of optically stimulated luminescence osl dating in the himalaya critical examination of existing data is used to suggest guidelines for the collection of suitable sediments for dating using osl in order to constrain the timing of glaciations osl has been shown to provide reproducible and apparently accurate ages which constrain glacial advances however the correct selection of sediments is of critical importance in spite of developments in the technique there remain limitations to its applicability reasons for this are considered as is the potential of osl for constraining the timing of glacial expansion

apparent osl ages of modern deposits from fabergstolsdalen norway implications for sampling glacial sediments the application of optically stimulated luminescence osl dating within glacial settings can be limited where sediments have not had their osl signal fully reset by sunlight exposure heterogeneous bleaching can result in age overestimations and although it is recognized that certain depositional settings are more likely to have experienced sufficient sunlight exposure to bleach the osl signal no comprehensive study has empirically investigated the processes of sediment bleaching or the variability in bleaching between deposits of the same type and within the same glacial catchment a suite of modern glacial and glaciofluvial sediments from fabergstolsda len southern norway have been analysed to explore the controls that sedimentary processes and depositional setting have on bleaching of the osl signal of quartz there is considerable variability in the residual osl ages of similar modern deposits which reflects high sensitivity of the osl signal to sediment source sedimentary process transport distance and depositional setting overdispersion values are greatest for the sediments which have been most heterogeneously bleached and these sediments have the lowest residual ages sampling strategies that incorporate sufficient consideration of the depositional framework of sample settings can minimize the effects of unbleached residuals on osl age determinations copyright 2013 the authors journal of quaternary science published by john wiley sons ltd on behalf of quaternary research association

luminescence dating and its application to key pre late devensian sites in scotland abstract relatively few sites have been identified in scotland that contain records that predate the peak of the late devensian glaciation ca 18 ka bp where such records have been identified they have assumed a key role in developing our understanding of climate change in scotland radiocarbon dating has been the primary chronological tool applied to these sites but the reliability of age determinations in excess of 30 ka is questionable in this paper we describe the results of a programme which applies luminescence dating methods to eight key pre late devensian sites in scotland methods were developed and tested to enable the identification of samples for which luminescence dating was only able to provide an upper limit on the age because of the limited light exposure that the sample experienced at deposition these new approaches were applied to four sites where independent age control was available this meant that the choice of sediments from test sites was restricted to those sediments which were formed in the last 40 000 years and hence were amenable to radiocarbon dating the luminescence age estimates for the control sites and the pre late devensian sites are discussed within the context of any existing chronological control on a site by site basis

zeroing of the tl signal in sediment undergoing fluvioglacial transport an example from austerdalen western norway abstract study of levels of natural tl in sediment undergoing fluvial transport in austerdalen norway shows that bleaching does occur but does not follow a regular pattern this is attributed to the incorporation of older unbleached material into the sediment load as a result of riverbank erosion levels of residual tl are high enough to raise doubts about the accuracy of fine grain tl dating of fluvioglacial sediments which have experienced only a short distance of transport

neodymium strontium and lead isotopes in the maloin ranch pluton wyoming implications for the origin of evolved rocks at anorthosite margins abstract neodymium strontium and lead isotopic data are used in this study to investigate the origin of chemically evolved rocks in the maloin ranch pluton a composite body that borders and intrudes the laramie anorthosite the range of rock types present is similar to that found at the margins of proterozoic anorthosites throughout the world in the maloin ranch pluton these include ferrodiorite at the base of the intrusion overlain progressively by fine grained monzonite monzosyenite and porphyritic granite biotite gabbro and fine grained granitic dikes are present locally at various levels of this sequence the origin of the evolved rocks and their possible relation to associated anorthositic bodies has been much debated in the maloin ranch pluton each rock type has distinct isotopic characteristics which together with trace element data previously reported suggest different source characteristics for each member strontium and neodymium isotopic data for maloin ranch ferrodiorite and laramie anorthositic rocks show considerable overlap consistent with a comagmatic relation biotite gabbro is chemically and isotopically the most primitive rock type in the maloin ranch pluton the data suggest that biotite gabbro has a mantle source but has undergone extensive fractionation in the crust our results suggest that the remainder and bulk of the intrusion formed by partial melting of the lower crust due to the emplacement of the laramie anorthosite maloin ranch fine grained monzonite is chemically more evolved than the underlying ferrodiorite i e lower mg higher silica and alkalis yet has more primitive isotopic characteristics lower isr higher epsilonnd formation of fine grained monzonite by in situ fractionation of ferrodiorite is precluded by both the isotopic data and by mass balance the isotopic data do not rule out formation of fine grained monzonite by fractionation or contamination of ferrodiorite at depth but this model requires that the ferrodiorite is isotopically heterogeneous and that very large volumes of ferrodiorite were present alternatively trace element and isotopic characteristics of the fine grained monzonite are explained by partial melting of mantle derived lower crust added to the margin of the archean wyoming craton at about 1 8 ga neodymium strontium and lead isotope data for maloin ranch monzosyenite and porphyritic granite also suggest a lower crustal source these data indicate a 1 8 ga source component for the maloin ranch monzosyenites but do not require input of archean crust from the wyoming province to the north

timing of past glaciations in kanchenjunga himal nepal by optically stimulated luminescence dating of tills abstract optically stimulated luminescence osl was used to date glacial sediments to elucidate the ages of past glacial advances in kanchenjunga himal eastern nepal seven glacial sediments samples were collected from four different moraines and quartz grains were extracted from samples however the luminescence from feldspars existing as minor contamination and or microinclusion in the quartz grains was so bright it masked the quartz signal after etching the fraction 20 min extra with hf the natural infrared stimulated luminescence irsl signal which indicates the existence of feldspar almost disappeared equivalent dose de values were estimated by the single aliquot regenerative dose protocol using two different quartz fractions fraction a which was etched 20 min extra and fraction b which was prepared by the standard procedure still had a strong feldspar signal although the natural irsl intensity for fraction a was so weak the regenerated irsl was relatively strong and not negligible for most of the aliquots such aliquots were omitted because the sensitivity of the feldspar is much higher than quartz and the difference in the sensitivity can cause de underestimation out of 42 aliquots from four samples for fraction a only six aliquots from two samples were remained the de values for single aliquots were uniformly distributed for fraction b moreover the calculated osl ages for fractions a and b from the two samples agreed with each other it is suggested that both quartz and feldspars grains or microinclusions in quartz grains were likely to have been bleached while glacial debris has been transported on the glacier the resulting osl ages suggest that the glaciers expanded at 5 6 8 10 and 20 21 ka in the kanchenjunga himal

geochronological osl and geomorphological investigations at the presumed frankfurt ice marginal position in northeast germany abstract the weichselian frankfurt ice marginal position in northeast germany has been critically discussed in the past owing to weak morphological evidence and a lack of clear sedimentological records this study aims to contribute to this discussion with new geochronological and geomorphological results apart from very few cosmogenic exposure ages the time frame is to date still based on long distance correlation with radiocarbon chronologies we selected a study site in a key position regarding the classic location of the frankfurt ice marginal position and the recently described arcuate ridge structures on the barnim plateau for the first time we present optically stimulated luminescence osl ages of quartz from glaciofluvial deposits for this weichselian phase our results indicate an advance of the scandinavian ice sheet sis at around 34 1 4 6 ka this is in agreement with osl ages from sandur deposits at the brandenburg ice marginal position located farther south and could also be correlated with the klintholm advance in denmark the subsequent meltdown phase lasted until around 26 3 3 7 ka during the meltdown phase a minor oscillation of the sis caused the formation of the recently described arcuate ridges on the barnim till plain recalculated surface exposure ages of glacigenic boulders with an updated global production rate indicate a landscape stabilization phase at around 22 7 1 6 ka which is in agreement with our ages a phase of strong aeolian activity has been dated with osl to 1 0 1 ka this may have been triggered by human activities that are documented in this region for the medieval period

optical dating of young modern sediments using quartz results from a selection of depositional environments abstract equivalent dose ed evaluations for quartz grains extracted from a number of modern or young samples collected from a range of depositional environments are reported the signal used was optically stimulated luminescence osl with an argon ion laser tuned to 514 nm as a light source typical equivalent dose values were 0 05 0 3 gy for the given samples which is substantially less than equivalent doses expected for similar sediments by conventional thermoluminescence tl the non zero equivalent dose exhibited by the samples may be a product of relict osl from incompletely bleached traps sample pre treatment procedures or due to signal recuperation following bleaching during antiquity the potential significance of each are discussed a number of modifications to sample pre treatment and processing are also described

the chronostratigraphy of late pleistocene glacial and periglacial aeolian activity in the tuktoyaktuk coastlands nwt canada aeolian periglacial sand deposits are common in the tuktoyaktuk coastlands of western arctic canada regionally extensive and thick aeolian sand sheet deposits have been observed in two major stratigraphic settings within a sand unit characterized by large aeolian dune deposits and interbedded with glaciofluvial outwash from the laurentide ice sheet lis small localized sand sheets have also been observed along the tops of sandy bluffs within sequences of drained thermokarst lakes deposits and as an involuted veneer above buried basal ice of the lis on the basis of radiocarbon and optically stimulated luminescence osl dates from preserved periglacial aeolian sand sheets and dunes a regional chronostratigraphy is presented which indicates that both extensive dunes and sand sheets accumulated mainly between ca 30 and 13 ka a switch to dominantly sand sheet aggradation at ca 14 13 ka with sand sheets forming widely until ca 8 ka is attributed to a surface armouring by glacial deposits associated with the advance of the lis and b amelioration of the climate from cold aridity an absence of osl dates between ca 8 and 1 ka suggests that sand sheets stabilized during much of the holocene local sand sheet aggradation during recent centuries has occurred near sandy bluffs and on the floors of drained thermokarst lakes the osl dates constrain the maximum extent of the lis in the tuktoyaktuk coastlands to marine isotope stage 2

age limits on middle pleistocene glacial sediments from osl dating north norfolk uk the lowland region of north norfolk contains some of the best preserved evidence for glacial deposition during the middle pleistocene in northwest europe despite the importance of these deposits there is limited chronological control and it is debated whether they belong to a single glaciation equated to the anglian glaciation marine isotope stage 12 or represent deposition over a number of middle pleistocene cold stages in order to develop an improved chronology for glaciation in this region we obtained 18 samples for optical stimulated luminescence osl dating from glacial outwash facies samples of coarse grained quartz sand were measured using the sar single aliquot regenerative dose protocol the low radioactive isotope concentrations in sediments of this region enable the traditionally accepted age limit of luminescence dating to be extended the form of the dose response curves pre heat plateaux tests and dose recovery experiments also indicate that laboratory doses can be reliably measured in these samples age overestimation due to partial bleaching is thought to be insignificant the osl ages suggest that the glacial sediments studied were deposited during mis 12 rather than in different post mis 12 stages

late quaternary glacial advances in the eastern qilianshan north eastern tibet as inferred from luminescence dating of fluvioglacial sediments

fluvial suspended sediment transport from cold and warm based glaciers in svalbard an analysis of temporal variability in proglacial suspended sediment concentration is undertaken using time series data collected from three svalbard basins which include one largely cold based glacier austre broggerbreen one largely warm based glacier finsterwalderbreen and one intermediate polythermal glacier erdmannbreen the temporal variability in proglacial suspended sediment concentration is analysed using multiple regression techniques in which discharge is supplemented by other predictors acting as surrogates for variability in sediment supply at diurnal medium term and seasonal timescales these multiple regression models improve upon the statistical explanation of suspended sediment concentration produced by simple sediment rating curves but need to account for additional stochastic elements within the time series before they may be considered successful an interpretation of the physical processes which are responsible for the regression model characteristics is offered as a basis for comparing the different arctic glaciofluvial suspended sediment transport systems with that of their better known temperate glaciofluvial counterparts it is inferred that the largely warm based glacier is dominated by sediment supply from subglacial reservoirs which evolve in a similar manner to temperate glaciers and which cause a pronounced seasonal exhaustion of suspended sediment supply the largely cold based glacier however is dominated by sediment supply from marginal sources which generate a responsive system at short time scales but no significant seasonal pattern the intermediate polythermal glacier basin which was anticipated to be similar to the warm based glacier instead shows a highly significant seasonal increase in suspended sediment supply from an unusual subglacial reservoir emerging under pressure in the glacier foreland the temperate model of glaciofluvial suspended sediment transport is therefore found to be of limited use in an arctic context copyright 1999 john wiley sons ltd

irsl from fine grained glacifluvial sediment abstract samples of suspended sediment were obtained from the dora di ferret a glacifluvial stream in the italian alps over a period of 24 h irsl analysis of the sediment indicates that the residual i nat signal is almost completely zeroed within 3 km of fluvial transport during daylight hours in contrast samples collected at night possess environmental doses d e in excess of 100 gy probably the luminescence signal of the parent till from which the fine grained suspended load has been derived quaternary deposits of glacifluvial sediment will contain a mixture of daylight and night transported mineral grains the resulting complex behaviour accounting for difficulties in luminescence dating such materials adaptations of single aliquot protocols and single grain protocols appear to offer the best chance of dating glacifluvial deposits accurately