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Rock surface luminescence exposure dating (RSLED) is an evolving tool in dating prehistoric rock surfaces. In this study, we explore and compare current and new models and calibration methods using optically stimulated luminescence (OSL) depth profiles from quartz grains and Infrared Stimulated Luminescence (IRSL; IR 50 , pIRIR 225 , and MET 290) from feldspar grains found in granite and sandstone samples. This study shows that, although correct model assumptions improve the quality of exposure age estimates, significant discrepancies between observed and expected fitting parameter values remain, and these discrepancies leads to inaccurate age estimation. This is particularly the case when post-IR signals from feldspar are used. Here, the spectral dependency of luminescence signals is examined to better understand these problems. The demonstrated depth dependency of fitting parameters, previously assumed to be constant with depth, also gives rise to discrepancies in parameter values. The surprising observation that, in rocks, the IR 50 signal is apparently more easily bleached than the quartz fast-component OSL signal is explained in terms of the wavelength dependence of light attenuation increasing the effective path length for shorter wavelengths, and so changing the shape of the light spectrum with penetration depth. This complicates parameter estimates in exposure dating even more. Alternative approaches (rather than parameter estimation) for estimating how long a rock surface has been exposed to light are considered, based on modelling the shape and position of the measured luminescence-depth profile. It is concluded that the most accurate exposure age is derived by interpolating the depth of an unknown profile onto a curve of profile depths from known age profiles (the Exposure Response Curve, or ERC, approach). • Investigating calibration methods for rock surface luminescence exposure dating. • Rock surface luminescence exposure dating experiments on quartz and feldspar. • Correct model assumptions improve the quality of exposure age estimates. • Discrepancies in exposure age estimations exist using current calibration methods. • The most accurate exposure age is derived by interpolation of bleaching depth (ERC). [ABSTRACT FROM AUTHOR]

Located in the mountain range of the Pyrenees, ~100 km from the current coastline, the archaeological site of Gatzarria -- in and around a karstic cave -- has yielded an important Palaeolithic sequence, spanning from the Middle to the Upper Palaeolitic. The lithic industries identified correspond to several Middle Paleolithic technocomplexes, based either on the Levallois, the Discoid or the Quina technology, and a few Châtelperronian elements have also been identified. Several chronological variants of Aurignacian superpose the Middle Palaeolithic sequence, and the Gravettian completes the Upper Palaeolithic sequence [1]. Whereas both the Aquitaine Basin (SW France) and the Cantabrian region (North of Spain) are very rich in archaeological sites from these periods, the northwestern foothill of the Pyrenees, where Gatzarria is located, is less well known, despite a non-negligible number of sites. Similarities do however exist with the archaeological record of all three areas and raw material sourcing supports long distance movements, of objects and/or people, between them. Obtaining a numerical chronology at Gatzarria cave will thus enable us to describe population dynamics and interactions in a key region of SW Europe, the "Basque crossroads", during several key moments of the Upper Pleistocene. Here we present OSL ages obtained from 34 sediment samples collected for OSL dating and processed in the usual manner using sand-sized (180-250 µm) quartz and feldspar grains. Preliminary multigrain quartz measurements using the single-aliquot regenerative-dose (SAR) protocol show that quartz is fast-component dominated, has satisfactory luminescence characteristics and dose response curves have an average characteristic dose (Dc value) of ~70 Gy. Single-grain quartz measurement show that only about 2% of the grains give detectable luminescence signals and a significant fraction of these are in saturation on the laboratory dose response curve. Only very little K-rich feldspar is present in these samples, but comparison with quartz age will be made where possible. Age modelling will be undertaken using both the commonly applied frequentist approach as well as Bayesian modelling using the specifically designed software tool BayLum [2]. [ABSTRACT FROM AUTHOR]

Central Asia is a key migratory route for the peopling of Asia during the Palaeolithic. Unfortunately, chronological information is limited, leaving a geographical and temporal gap in our knowledge of human migrations. One of the aims of the transdisciplinary project THOCA ("Timing and Ecology of the Human Occupation in Central Asia") is to determine the chronology of the first settlements in Central Asia over time through the study of three major archaeological sites (Khonako, Obi Mazar and Kuldara) located in the Khovaling Loess Plateau of Tajikistan [1]. Luminescence dating is being used to date the upper part of the sections, providing a chronological framework for palaeoenvironmental, palaeoecological, and palaeoclimatic studies over the past ~250 ka. Here we present the first detailed luminescence chronology of the Khonako sites. These sections consist of an alternation of thick loess units and up to 16 well-developed pedocomplexes (PC), providing a sedimentary record presumably back to MIS 31. Lithic assemblages excavated in the upper PC 1 and PC 2 are among the best representatives of the regional Middle Palaeolithic industries. About 320 samples were taken to establish a chronological model down to at least PC 2. Because of the high dose rates (~ 3 Gy/ka), the OSL signal from quartz can only be used to date the last ~30 ka, and so only the upper part of the section (~ top of L1). Quartz OSL and feldspar pIRIR200,290 ages are compared to evaluate the completeness of bleaching of the pIRIR200,290 signal and evaluate the size of the presumed residual dose that was present at deposition. First IR stimulation temperature tests are used to confirm the suitability of our pIRIR protocol. Because of the fine-grained nature of the sediment, only very small amounts of 63-90 µm K-rich feldspar grains could be extracted. Therefore, measurements using a pIRIR200,290 protocol were also carried out on the polymineral 63-90 µm fractions (i.e. no HF treatment or heavy liquid separation). All these measurements were made using a test dose approximately equal to the measured De. Dose recovery ratios (of between 0.91 ± 0.09 and 1.07 ± 0.02) are satisfactory for 6 samples ranging from ~ 20 ka (given dose of ~ 90 Gy) to ~ 250 ka (given dose of ~ 770 Gy) after the subtraction of residual doses (from 16 Gy to 54 Gy). Our preliminary test results also show that the polymineral 63-90 µm fraction yields the same De values as purified K-rich feldspar extracts. The new chronology for the Khonako sites confirms that PC 2 and PC 1 can be associated with MIS 7 and 5, respectively. The sedimentary record appears to be almost continuous through the last 250 ka, although there may be a hiatus in sedimentation at the bottom of PC 1 (end of MIS 6/beginning MIS 5). [ABSTRACT FROM AUTHOR]

The main purpose of this study is to investigate the accuracy of single-grain quartz OSL SAR dating for samples with known absorbed natural doses in the 150-200 Gy range. There exists some evidence that at least multi-grain quartz OSL ages tend to underestimate the true burial age in this dose interval by ~10- 15% (e.g. [1,2]). It has been hypothesized that single-grain data are superior to multi-grain data, because the latter must contain signals from `aberrant' grains (e.g. grains failing SAR procedural tests and/or grains in saturation), which can be excluded in single-grain analysis. Here we test this hypothesis using five known-age Eemian (MIS 5e, ~125-130 ka) sediment samples collected in northern Russia (Sula [1]) and in Denmark (Gammelmark [2]); conventional multi-grain methods using quartz gave results consistent with expectations for both sites, although there appeared to have been a small systematic age underestimate. Preliminary single-grain measurements show that ages are in poor agreement with the age control when using the conventional frequentist approach; the expected dose is underestimated by ~50%. Applying commonly used rejection criteria (e.g. recycling, OSL IR depletion and recuperation) does not improve this significant underestimation. However, a significant fraction (~40- 50%) of the detectable grains have natural sensitivity corrected OSL signals which cannot be interpolated on to the individually constructed laboratory dose response curves to give finite dose values, i.e. the grains are said to be in saturation. Previously, it has been argued that discarding such grains has the potential to significantly bias the resulting dose distributions towards low doses. In an attempt to circumvent this bias, it has been suggested that all grains with dose response curves with low characteristic doses (Dc values) compared to the natural dose ought to be rejected. Here we test if the so-called Dc criterion suggested by [3] in combination with Bayesian modelling using the specifically designed software tool BayLum [4] can help overcome this bias. [ABSTRACT FROM AUTHOR]

Luminescence dating of rock surfaces is an emerging absolute chronological technique that has the potential to determine how long a rock surface has been exposed to daylight and/or how long it has been buried. By measuring the OSL signal as a function of depth into the rock surface, it is possible to determine how long the rock surface has been exposed to daylight by fitting a luminescence kinetic model to the measured luminescence-depth profile. Despite increasing use of this technique, the possible dependence of derived ages on the chosen model has not been examined. Existing studies are based on the assumption that first-order kinetics apply and a first order model (F.O.M.) has been used. In this study, we use (i) a general-order kinetics model G.O.M., (McKeever and Chen, 1997) and (ii) a localised recombination model here referred to as the fading model, F.M., (Jain et al., 2015) to develop new analytical expressions for luminescence-depth profiles in rocks. These models are tested using both simulated and experimental data based on the IR 50 signal. Based on these tests it is concluded that the derived apparent exposure ages are dependent on the chosen model. This model dependence occurs despite the fact that the speed of progression of the bleaching front into the rock surface is model independent. The reasons for this apparent discrepancy are discussed in details. Calibration with a single known-age sample (Sohbati et al., 2012b) gives inaccurate exposure ages for all investigated models unless the appropriate model is applied and/or the age of the calibration profile is of the same order of magnitude as the age of the unknown profile, but using the G.O.M. improves the accuracy of age estimates for IRSL profiles. An alternative approach to exposure dating is presented here as "Exposure Response Curve" calibration. We conclude that using inflection points, to avoid the difficulties caused by fitting parameter correlation, proves model-independent, and is a promising method for further investigation in Rock Surface Luminescence Exposure dating. • Develop new analytical expressions for luminescence-depth profiles in rocks. • Testing models using simulated and experimental data based on the IR50 signal. • Model dependence occurs despite that the speed of progression is model independent. • The general order model improves the accuracy of age estimates for IRSL profiles. • Calibrating by using Exposure Response Curve (ERC) proves model independent. [ABSTRACT FROM AUTHOR]

Two fluvial sediment cores taken from a floodplain of the Hawkesbury- Nepean River system in the Sydney region, eastern Australia are dated using Optically Stimulated Luminescence ( OSL) to provide a reliable chronology essential for the management and planning of water resources. Nine charcoal 14 C ( AMS) dates constrain these OSL ages. Quartz extracted from seven OSL samples from each of the cores was measured using both single-grain and multi-grain OSL techniques. Three of the single-grain natural dose distributions appear to be well bleached, but the others appear to be incompletely bleached to various degrees. Three minimum-age models ( MAM, MAMUL and IEU) are applied to the single-grain dose distributions. We conclude that these models give consistent age estimates. For one of the cores it appears to be necessary to use a minimum-age model to obtain accurate ages, but in the other core incomplete bleaching is probably less important than postdepositional mixing and mixing during sampling. As a result, the burial age is probably best estimated using the weighted average of the individual single-grain dose estimates. The application of multi-grain OSL techniques to these samples results in an average apparent age overestimation of ∼200 years, which is significant for these samples, but negligible for sediments older than a few thousand years. The intention is that the chronology obtained in this study will be used in conjunction with a proxy flood record, derived from floodplain sediments, to gain an understanding of the long-term variability in periods of high and low rainfall in eastern Australia. [ABSTRACT FROM AUTHOR]

Abstract: The use of single grain quartz OSL dating has become widespread over the past decade, particularly with application to samples likely to have been incompletely bleached before burial. By reducing the aliquot size to a single grain the probability of identifying the grain population most likely to have been well-bleached at deposition is maximised and thus the accuracy with which the equivalent dose can be determined is – at least in principle – improved. However, analysis of single grain dose distributions requires knowledge of the dispersion of the well-bleached part of the dose distribution. This can be estimated by measurement of a suitable analogue, e.g. a well-bleached aeolian sample, but this requires such an analogue to be available, and in addition the assumptions that the sample is in fact a) well-bleached, and b) has a similar dose rate heterogeneity to the fossil deposit. Finally, it is an implicit assumption in such analysis that any over-dispersion is not significantly dose dependent. In this study we have undertaken laboratory investigations of the dose dependency of over-dispersion using a well-bleached modern sample with an average measured dose of 36 ± 3 mGy. This sample was prepared as heated (750 °C for 1 h), bleached and untreated portions which were then given uniform gamma doses ranging from 100 mGy to 208 Gy. We show that for these samples the relative laboratory over-dispersion is not constant as a function of dose and that the over-dispersion is smaller in heated samples. We also show that the dim grains in the distributions have a greater over-dispersion than the bright grains, implying that insensitive samples will have greater values of over-dispersion than sensitive samples. [Copyright &y& Elsevier]

In this study we present the first luminescence ages for the upper part of the Kuldara loess-palaeosol sequence, in the Khovaling Loess Plateau in Southeast Tajikistan. This study is part of the THOCA project ("Timing and Ecology of the Human Occupation in Central Asia", www.thoca.org) in which we aim to reconstructthe timing of hominin arrival in Central Asia, and the environmental and palaeoclimatic conditions under which they lived and evolved. The Kuldara site is located ~15 km from the famous Khonako site complex (see Challier et al., these proceedings) and is close to the Obi-Mazar/Lakhuti palaeolithic site [1,2]. The upper ~20 m of the stratigraphy at Kuldara is made up of a Holocene soil (~1.4 m thick), a thick (~10 m) L1 loess and two pedocomplexes (PC1 and PC2) separated by only ~2 m of (L2?) loess; the latter suggests that part or most of the presumed MIS6 loess was eroded at this site. In general, Tajik loess sequences consist of more than 40 pedocomplexes and cover a sedimentary history of the last 2 Ma; they are presumed to be complete. Even though previous studies noted that most parts of the sequences have no distinguished hiatuses, many sections have shortened loess layers between PC1 and PC2, and in some cases these two PC's are sitting immediately on top of eachother. This phenomenon suggests a regional erosional event, which could be activated by wind/water/ slope processes or tectonic uplift. For understanding this important event we need to identify the chronological range of this regional hiatus. In order to provide an independent timescale for palaeoclimatic studies using grain size, magnetic mineral assemblages, etc., and to check the completeness of the sedimentary record, 70 luminescence samples were collected using stainless steel tubes down to below the PC2 complex. A higher spatial sampling density was used in S0 and L1 (~15 cm) compared to the lower part of the sequence where it was ~50 cm. Quartz and feldspar in the coarse-silt and/or fine sand (40-63/63-90 µm) range were extracted using conventional sample preparation techniques. Quartz was purified using HF only, no heavy liquid separation was attempted and so the feldspar fraction must have contained significant quartz. Dose rates were determined using high resolution gamma spectrometry and are typical for loess in Tajikistan (~3-3.5 Gy/ka to silt-size d quartz grains). Quartz OSL dating is used to constrain the timing of loess deposition for the upper part of the sequence (De ≤ 150 Gy) and to determine a residual dose for the pIRIR200,290 signal. We apply pIRIR200,290 dating to the bottom part of the sequence using a relatively large test dose as suggested by the results of dose recovery tests. It appears that we can obtain reliable pIRIR200,290 De estimates up to ~800 Gy allowing us to provide a detailed luminescence chronology for the Kuldara site back to ~250 ka. [ABSTRACT FROM AUTHOR]

Marine sediments occupy a significant portion of the Quaternary succession in the West Siberian Arctic but, until recently, their ages and distributions have been strongly debated. Based on new geological, palaeontological and geochronological data obtained within the last decade, we hereby postulate the following: (i) Two different Pleistocene interglacial marine formations are exposed across the West Siberian Arctic. The older Kheta marine formation, sandwiched between two Middle Pleistocene till beds, yields optically stimulated luminescence (OSL) ages of c. 200 ka (MIS 7). The younger Karginsky/Payuta marine formation, overlying the Middle Pleistocene Taz till, contains a boreal mollusc fauna and has an OSL age of c. 115 ka (MIS 5e). These Middle and Upper Pleistocene marine beds have been correlated across a vast region between the Ob' and Yenisey estuaries. (ii) The marine transgression during MIS 7 spread as far south into West Siberia as 65°N, almost 1000 km southwards from the present‐day Kara Sea shoreline. Meanwhile, the smaller marine transgression during MIS 5e reached as far south as 68°N. (iii) Both marine formations contain a boreal molluscan fauna, which is not found in the modern Kara Sea but is characteristic of the North Atlantic. We propose that warmer Atlantic waters penetrated much further eastwards during both MIS 7 and MIS 5e than at present. The diagnostic extinct mollusc species Cyrtodaria jenisseae has only been found in the older Kheta marine formation (MIS 7). [ABSTRACT FROM AUTHOR]

Abstract: This paper gives a review of recent developments in luminescence measurement facilities on the Risø TL/OSL reader including radio-luminescence (RL), exo-electron and violet stimulation attachments, and a method for characterising and if necessary correcting for beta irradiation source non-uniformity. We first describe improvements to the existing RL option to allow near infra-red detection (NIR) during irradiation by the built-in 90Sr/90Y beta source. The RL optical signal is collected by a liquid light guide through an F34-901 interference filter and detection is based on a dedicated thermoelectrically cooled NIR sensitive PMT (detection window peak at 855 nm, FWHM 27 nm). Software and electronics have been modified to allow standard TL and OSL measurements in the same sequence as RL measurements. Together with a new bleaching source based on a high-power UV LED (395 nm; 700 mW/cm2), this facility has been used to measure natural doses in feldspar using the decaying NIR RL signal. Secondly, we present a method for mapping radiation field of the built-in 90Sr/90Y β-source and estimating grain-location specific dose-rates. This is important for the accuracy of single grain results, when radiation field is spatially non-uniform across the sample area. We document the effect of this correction method and further investigate on the effect of lifting the source to achieve a better dose-rate uniformity. Finally we summarise two recently-developed novel facilities to help investigate (i) the time scales involved in OSL processes (time-resolved exo-electron detection) and (ii) extending the age range (violet stimulated signals from deep quartz OSL traps). [Copyright &y& Elsevier]

Located in southwest France, Roc de Marsal is a cave with a rich Mousterian stratigraphic sequence. The lower part of the sequence (Layers 9–5) are characterized by assemblages dominated by Levallois lithic technology associated with composite faunal spectra (including red deer, roe deer and reindeer) that shows a gradual increase in the frequency of reindeer. The top of the sequence (Layers 4–2) are characterised instead by Quina lithic technology (both in terms of technology and typology) with the faunal remains dominated by reindeer. Roc de Marsal thus provides a very interesting case study to place behavioural changes in a context of changing climates and environments in western Europe during the late Pleistocene. To link the occupations at Roc de Marsal with global and regional climatic conditions known independently, a robust chronology is needed. With this aim in mind, we applied three luminescence dating methods (TL, OSL and IRSL) on different minerals (flint, quartz and K-feldspar extracts). Here the results of two of these methods are presented in detail (TL and OSL) and compared with preliminary IRSL data. At Roc de Marsal, a comparison of methods was necessary to overcome a complex sedimentary history, with very heterogeneous dose rate distributions, both at the beta (mm) and gamma (dm) dose rate scales. The results indicate that the lower Levallois layers are dated to ∼65–70 ka, while overlying Quina layers are dated to ∼49 ka. These ages for the lower layers fit well with some models that place mixed faunal assemblages in the initial MIS 4; however, while the Quina ages overlap with several other Quina assemblages from the region, they place the reindeer dominated fauna well after the peak cold of MIS 4 and suggest a more extended and complex period of contemporaneous lithic techno-complexes than posited by some current models. [ABSTRACT FROM AUTHOR]

• A wide-field EMCCD camera-based alpha imaging system is presented. • An efficient near-real-time image processing algorithm is developed. • Fully automated removal of cosmic and thermal noise and locating alpha particle interactions in CCD images. • Comparison of counting efficiency with a photomultiplier-based alpha counter. • Demonstration of application by comparison to a micro XRF determined element map. We demonstrate a wide-field alpha-particle imaging system based on the detection of alpha-induced scintillation light from ZnS:Ag screen using an EMCCD camera. We develop an efficient image processing algorithm to remove cosmic and thermal noise and to locate alpha particle interactions in EMCCD images. This algorithm is particularly suited to imaging low-activity samples where long image acquisition periods entail a large number of frames with no detected alpha particle. Our system has a relative counting efficiency of ∼50 % compared to a PMT-based alpha counter. It can detect alpha particles at a resolution of <480 µm over an imaging area of ∼45 × 45 mm. We demonstrate the performance of this system by imaging a granite sample. Correlation between the resulting alpha image and the micro XRF-determined element map demonstrates that most of the alpha activity in our sample is held in dark-coloured Ba-rich veins and inclusions at mineral grain boundaries. [ABSTRACT FROM AUTHOR]

We report the first geochemical record in two drill-sediment cores from a buried channel in the Ghaggar Plains of NW India, which are used to infer variations in provenance, paleoclimate, and paleovegetation in the locality during the Late Quaternary. Aeolian sediments (~ 150 ka) in both the cores are overlain by fluvial sediments (~ 75 ka–recent). Major oxide compositions of the core sediments ( n = 35) generally vary between that observed for the modern-day Ghaggar/Sutlej and Yamuna river sand. The isotopic composition ( 87 Sr/ 86 Sr: 0.7365 to 0.7783 and ε Nd : − 14.6 to − 19.0) of core sediments ( n = 18) suggest binary mixing of sediments from compositionally distinct Higher Himalaya (HH) and Lesser Himalaya (LH) endmembers in the catchment, and support involvement of a river system originating in the Himalayan hinterland. Distinctly higher 87 Sr/ 86 Sr and lower ε Nd in the core sediments during glacial periods can be explained by increasing sediment contribution from LH (high 87 Sr/ 86 Sr and low ε Nd ) due to an increase in glacial cover over HH. Whereas relatively less glacial cover over HH during interglacial periods resulted in more erosion and sediment contribution from HH. The down-core Sr–Nd isotopic variability clearly reflects climate-controlled sediment erosion in the Himalayan catchment. Temporal variations in δ 18 O and δ 13 C of carbonate nodules ( n = 27) are consistent with that reported from the Ganga interfluves. The δ 13 C variability (− 4.1‰ to 1.2‰) in carbonates is mainly controlled by the extent of silicate (HH) versus carbonate (LH) source weathering due to significant climatic shifts. The δ 13 C of sediment organic matter (− 27.4‰ to − 23.2‰, n = 24) suggests dominantly C 3 plants in the catchment during the last ~ 75 ka. More negative δ 13 C values in sediments during glacial periods relative to those during interglacial periods can be explained by increasing C 4 abundance during interglacial periods characterized with both higher summer rainfall and mean annual temperature. [ABSTRACT FROM AUTHOR]

While reviews of comparisons between multi-grain OSL ages and independent chronological information are available in the literature, there is hardly any such performance test for single-grain OSL ages. And yet, this is all the more needed as the interpretation of single-grain dose distributions remains a difficult task, given the typically considerable dispersion in equivalent dose values measured by OSL – and the numerous sources of such dispersion in measurements. Here, we present the study of 19 samples for which independent age control is available, and whose ages range from 2 to 46 ka. Based on multi-grain OSL age estimates, these samples are presumed to have been both well-bleached at burial, and unaffected by mixing after deposition. Two ways of estimating single-grain ages are then compared: the standard approach on the one hand, consisting of applying the Central Age Model to D e values determined with the Analyst software; on the other hand, the central dose model recently proposed by Combès et al. (Combès, B., Philippe, A., Lanos, P., Mercier, N., Tribolo, C., Guerin, G., Guibert, P., Lahaye, C., in press. Quaternary Geochronology). The median of the relative discrepancy between single-grain OSL and reference ages is about twice as large for the standard approach (12%) as with the Bayesian model (7%). Statistical tests show that, based on our (limited) dataset, the difference between the two models seems to be significant for samples in the age range 4–46 ka. Finally, the influence of various factors on the (in-)accuracy of single grain OSL ages is discussed; it appears that the accuracy of ages estimated in a standard way decreases when age is increased, while the Bayesian model seems more robust. This study also shows that (i) there is no 20% limit on the CAM overdispersion parameter for well-bleached samples; (ii) dose recovery experiments do not seem to be a very reliable tool to estimate the accuracy of a SAR measurement protocol for age determination. [ABSTRACT FROM AUTHOR]

A new interdisciplinary project was initiated to excavate a portion of the Palaeolithic site of La Ferrassie left intact by earlier excavations. One of the aims of this project was to provide chronological information on the succession of Middle and Upper Palaeolithic layers, as well as on the skeletons unearthed by Capitan and Peyrony in the early 1900's. We report here preliminary results on the lithics, faunal remains, site formation processes, and on the stratigraphic context of the La Ferrassie 1 and 2 skeletons that were found adjacent to our excavations. Finally, results from luminescence dating of the sediments and a preliminary set of radiocarbon ages are presented. Quartz OSL, both at the multi-grain and single-grain levels of analysis, and post-IR IRSL of feldspar at various stimulation temperatures are compared. The quartz/feldspar comparison revealed a bleaching problem for the quartz OSL (and the feldspar pIRIR signals) from Layer 2; as a consequence, the age of this Layer was determined using a minimum age model. A Mousterian industry with bifaces, at the base of the sequence, has been dated between 91 ± 9 and 44 ± 3 ka. The Ferrassie Mousterian layers are attributed to MIS 3, between 54 ± 3 and 40 ± 2 ka, and thus appear very late in the final Middle Palaeolithic of the region; furthermore, these ages constrain the chronology of the La Ferrassie 1 and 2 skeletons, which have been attributed to one of these Ferrassie Mousterian layers. The Châtelperronian layer is dated to 42 ± 3 ka and the Aurignacian to 37 ± 2 ka. Implications of the ages for the La Ferrassie 1 and 2 skeletons, and for the variability of late Mousterian, are discussed. [ABSTRACT FROM AUTHOR]

Luminescence dating is used extensively to provide absolute chronologies for Late Pleistocene sediments. Nowadays, most optical dates are based on quartz optically stimulated luminescence ( OSL). However, the application of this signal is usually limited to the last ∼100 ka because of saturation of the quartz luminescence signal with dose. In contrast, the feldspar infrared stimulated luminescence ( IRSL) dose-response curve grows to much higher doses; this has the potential to extend the datable age range by a factor of 4-5 compared with quartz OSL. However, it has been known for several decades that this IRSL signal is unstable, and this instability often gives rise to significant age underestimation. Here we test against independent age control the recently developed feldspar post- IR IRSL approach to the dating of sediments, which appears to avoid signal instability. A physical model explaining our observations is discussed, and the method is shown to be accurate back to 600 ka. The post- IR IRSL signal is reduced by exposure to daylight more slowly than that from quartz and low-temperature IRSL, preventing its general application to young (e.g. Holocene) sediments. Nevertheless, this new approach is widely applicable (feldspar of appropriate luminescence behaviour is even more ubiquitous than quartz). These characteristics make this a method of great importance for the dating of Middle and Late Pleistocene deposits. [ABSTRACT FROM AUTHOR]

In the comment on our paper (this issue), Clift et al. (2016) compared our recently reported radiogenic Nd-isotopic record in two drill cores (Singh et al., 2016) with those from the Hakra floodplain sediments and Indus Delta sediments. While they agree with the concept of erosion patterns in the western Himalayan sources being climatically modulated, they offer an alternative interpretation for our reported variability in the radiogenic Nd-isotopic values. Here, we show that the Nd-isotopic values for the Holocene succession instead can be explained by the bedrock geology of the source region of these sediments. Moreover, we note that whereas our paper considers a ~ 75 ka fluvial depositional record, their comment is only based on the post-Last Glacial Maximum (LGM) record. When considering the longer record, their arguments do not negate the main conclusions of our original paper. [ABSTRACT FROM AUTHOR]

We report on quartz Optically Stimulated Luminescence (OSL) dating of the infill of 14 relict sand wedges and composite-wedge pseudomorphs at 5 different sites in Flanders, Belgium. A laboratory dose recovery test indicates that the single-aliquot regenerative-dose (SAR) procedure is suitable for our samples (measured to a given dose ratio 0.980 ± 0.005; n=139). Completeness of resetting of the wedge infill of two samples was confirmed by single-grain analyses. The suite of optical ages indicates that repeated thermal contraction cracking, degradation and infilling with wind-blown sediment appear to have been commonplace in Flanders during the Late Pleniglacial (Oxygen Isotope Stage 2; OIS2); more specifically, around the Last Glacial Maximum (LGM, ∼21 kyr ago) and the transition period between the LGM and the start of the Lateglacial (∼15 kyr ago). Optical dating at one site has revealed two significantly older wedge levels, the younger inset into the older; the younger wedge has an age of 36 ± 4 kyr (Middle Pleniglacial; OIS3), the older wedge 129 ± 11 kyr, which points to formation during the Late Saalian (OIS6). Our OSL ages of the wedges and host sediments bracket formation of the BGB (Beuningen Gravel Bed: a widespread deflation horizon in northwestern Europe) at between ∼15 and 18 kyr; this is in good agreement with previous OSL dating studies. We conclude that optical dating using quartz SAR OSL establishes an absolute chronology for these periglacial phenomena and allows secure palaeoenvironmental reconstructions to be made. [ABSTRACT FROM AUTHOR]