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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]

Statistical analysis has become increasingly important in optically stimulated luminescence (OSL) dating since it has become possible to measure signals at the singlegrain scale. The accuracy of large chronological datasets can benefit from the inclusion, in chronological modelling, of stratigraphic constraints and shared systematic errors. Recently, a number of Bayesian models have been developed for OSL age calculation; the R package "BayLum" presented herein allows different models of this type to be implemented, particularly for samples in stratigraphic order which share systematic errors.We first show how to introduce stratigraphic constraints in BayLum; then, we focus on the construction, based on measurement uncertainties, of dose covariance matrices to account for systematic errors specific to OSL dating. The nature (systematic versus random) of errors affecting OSL ages is discussed, based -- as an example -- on the dose rate determination procedure at the IRAMAT-CRP2A laboratory (Bordeaux). The effects of the stratigraphic constraints and dose covariance matrices are illustrated on example datasets. In particular, the benefit of combining the modelling of systematic errors with independent ages, unaffected by these errors, is demonstrated. Finally, we discuss other common ways of estimating dose rates and how they may be taken into account in the covariance matrix by other potential users and laboratories. Test datasets are provided as a Supplement to the reader, together with an R markdown tutorial allowing the reproduction of all calculations and figures presented in this study. [ABSTRACT FROM AUTHOR]

Urbanism in the Bronze-age Indus Civilisation (~4.6–3.9 thousand years before the present, ka) has been linked to water resources provided by large Himalayan river systems, although the largest concentrations of urban-scale Indus settlements are located far from extant Himalayan rivers. Here we analyse the sedimentary architecture, chronology and provenance of a major palaeochannel associated with many of these settlements. We show that the palaeochannel is a former course of the Sutlej River, the third largest of the present-day Himalayan rivers. Using optically stimulated luminescence dating of sand grains, we demonstrate that flow of the Sutlej in this course terminated considerably earlier than Indus occupation, with diversion to its present course complete shortly after ~8 ka. Indus urban settlements thus developed along an abandoned river valley rather than an active Himalayan river. Confinement of the Sutlej to its present incised course after ~8 ka likely reduced its propensity to re-route frequently thus enabling long-term stability for Indus settlements sited along the relict palaeochannel. [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]

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]

In the note “A response to some unwarranted criticisms of single-grain dating” Feathers raises many issues with both the approach and the conclusions of Thomsen et al. (2016) . After careful consideration, we find we disagree with Feather's analysis and conclusions, and stand by the original conclusions of Thomsen et al. (2016) . We reiterate that, for these samples, the multi-grain measurements are demonstrably in better agreement with the independent age control than are the standard single-grain measurements. In our view, Feathers’ most important criticisms are that the 14 C age control is reported incorrectly and that Thomsen et al. (2016) cannot conclude that standard single-grain methods are in poorer agreement with the independent age control than the multi-grain methods. We acknowledge the presence of a minor presentation error in Figure 3 of Thomsen et al. (2016) , but we demonstrate that this detail has no bearing on the conclusions of Thomsen et al. (2016) . [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]

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]

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]

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]