Electron Spin Resonance Dating Research Articles

Preliminary ESR dating results of fault barite shed new insights into the retrospective history of bedrock fault activities in basaltic regions

The chronology of fault activity in bedrock is critical to constraining and understanding periods of active faulting, assessing seismic hazards, and mitigating the effects of earthquakes. However, because of the lack of suitable materials for dating, the temporal reconstruction of faulting in bedrock remains highly challenging for geologists. In the present study, we determine for the first time the electron spin resonance (ESR) ages of fault barite (BaSO4), which is produced by episodes of intense faulting on basalt bedrock fault surfaces. Three barite samples were obtained from a basalt fault section (27°5′23″N, 100°25′45″E, 1.8 km above sea level) of the Lijiang–Xiaojinhe Fault (LXF), southeastern Tibetan Plateau, for ESR measurements. Similar to marine barite, the ESR spectrum of fault barite shows an electron-type center with g = 2.0037, 2.0034, and 2.0028 attributed to SO3−. The signal intensity systematically increased with increasing gamma-ray dose. Dose rates were calculated using a model based on the location and burial depth of the barite samples, as well as their surrounding bedrock. The three barite samples yield ESR ages of 131 ± 26, 503 ± 61, and 1416 ± 246 ka, respectively, which indicate that the LXF was active during the Early and Middle Pleistocene. The three ESR ages for fault barite from basalt extend the time range of activity of the LXF compared with previous carbonate ESR and radiocarbon dating results. Consequently, we propose that ESR dating of barite is valuable for reconstructing the history of bedrock fault activity. However, given that this investigation represents a preliminary application of the fault-barite ESR method, further study is needed to confirm its usefulness and the accuracy and precision of dating results.

Electron Spin Resonance Dating of Shells—A Systematic Literature Review

Electron Spin Resonance Dating of Shells—A Systematic Literature Review

Extended-range luminescence and ESR dating of Iberian fluvial terraces (Duero and Guadiana basins) associated with the Lower Palaeolithic sites of La Maya I, II, III, Burganes and Albalá (west-central Spain)

The major river basins of the Iberian Peninsula that drain towards the Atlantic coast contain extensive Lower Palaeolithic (Acheulean) records associated with well-preserved fluvial terrace sequences. These open-air archaeological records are often difficult to constrain chronologically due to a lack of suitable material for dating (e.g., faunal remains) or because their Middle Pleistocene antiquity precludes the use of otherwise routinely applicable geochronometric techniques such as conventional optically stimulated luminescence (OSL) dating. As a result, many important Iberian Acheulean sites lack precise and accurate chronologies, and their existing temporal frameworks are based solely on morphostratigraphic correlations with regional fluvial terrace systems. Here we present the first application of extended-range luminescence dating – namely multi-grain post-infrared infrared stimulated luminescence (pIR-IRSL) dating of K-feldspars and single-grain thermally transferred-OSL (TT-OSL) dating of quartz – to a series of terrace sequences in the Duero basin (central sector) and Guadiana basin, as well as associated Lower Palaeolithic sites of La Maya I, II and III along the Tormes River, Burganes (and related sites) along the Tera River, and Albalá along the Guadiana River. Additionally, we present results of a parallel electron spin resonance (ESR) quartz dating study of the Tormes River terrace (Duero basin), which has been undertaken independently on the same samples to enable stratigraphically paired dating comparisons. Our study indicates that sedimentary quartz from this sector of the Duero basin produces very weak TT-OSL signals, variable Al signal repeatability and below-average Ti signal fitting uncertainties, though it is still possible to determine consistent comparative ages using the measurements protocols employed here. For samples where both pIR-IRSL and TT-OSL signals were measured, the paired luminescence dating ages are in agreement at 1σ. Agreement between the quartz ESR and TT-OSL ages is also observed for one sample from the Tormes River. However, the ESR signals (both Al and Ti) of a second sample showed insufficient bleaching and age overestimation in comparison to the paired TT-OSL dataset. Comparison of our latest dating results with published chronological datasets point to some fluvial terraces of the Duero basin potentially having diachronous formation histories. Despite this, our combined chronological results show that the terrace systems are chronologically ordered and suggest that, regionally, the +8 to +34 m terraces likely post-date marine isotope stage (MIS) 10, whilst the +50 m terraces formed prior to, or during, MIS 10. The related Acheulean sites that contain lithic material in stratigraphic position are dated to MIS 9–7 (193–314 ka at 2σ age range), and temporally overlap with the early Middle Palaeolithic records in the Duero basin, also dated here to MIS 8–7 (or 159–259 ka at 2σ). Our results are consistent with previous observations regarding the chronological overlap of these two technologies in the region, and support the possibility of a non-linear pattern of replacement for the Acheulean in the Iberian Peninsula during the Lower to Middle Palaeolithic transition.

Evaluating signal bleaching of Al and Ti–Li centers in fluvio-lacustrine sediments of Datong, North China, and its implications for the volcanic eruption chronology

Assessing the adequate bleaching of quartz Electron Spin Resonance (ESR) signals at the time of deposition is essential for sediment ESR dating. In this study, we focus on the Datong volcanic group is situated in Datong City, Shanxi Province, and is among the most renowned volcanic groups in China. The eruption within the Datong volcanoes during a geological period resulted in extensive high-temperature lava flow that directly overlaid Quaternary lacustrine deposits and subjected the underlying lacustrine layers to high-temperature heating. Thus, an investigation of the field profile in the Yujiazhai area, southeast of the Datong Volcanic Group, shows a novel approach for assessing the bleaching extent of ESR centers. This is accomplished by comparison of the DE values of the Al and the Ti–Li centers in partly-heated layer sample. The result reveals that quartz Al and Ti–Li centers in the lacustrine sediments appear to undergo sufficient bleached during transportation and natural bleaching processes in the study area. Furthermore, this study provides insight into the chronology of volcanic eruption in the Yujiazhai area, estimating an eruption age of approximately 300 ka. This volcanic activity most likely corresponds to the third volcanic activity period in the Datong region.

Can We “Play Dirty” in ESR Dating?

Can We “Play Dirty” in ESR Dating?

An integrated chronological study on the Quaternary sedimentary sequences of the Yangtze River delta, China

The sedimentary sequences of the Yangtze River delta comprise important Quaternary records of tectonics, sea-level oscillation, and climatic change; however, analysis is hampered by a lack of a reliable chronological framework. In this paper, we present an integrated chronology for two sedimentary sequences (core ZKW2 and ZKW4) on the southern side of the Yangtze River delta, based on magnetostratigraphy and absolute methods (OSL, 14C, and ESR dating). The basal ages of the core ZKW2 and ZKW4 are ca. 2.25 Ma and 2.96 Ma, respectively. The integrated chronology indicates significant increases in the sedimentary accumulation rate at ∼0.15 Ma, rather than the Matuyama-Brunhes boundary as indicated by magnetostratigraphy alone. The observed sedimentary transition is possibly controlled by regional subsidence of the Zhe-Min Uplift, and climate evolution during the last interglacial period.

Combined uranium-series and electron spin resonance dating from the Pliocene fossil sites of Aves and Milo's palaeocaves, Bolt's Farm, Cradle of Humankind, South Africa.

Bolt's Farm is the name given to a series of non-hominin bearing fossil sites that have often been suggested to be some of the oldest Pliocene sites in the Cradle of Humankind, South Africa. This article reports the results of the first combined Uranium-Series and Electron Spin Resonance (US-ESR) dating of bovid teeth at Milo's Cave and Aves Cave at Bolt's Farm. Both tooth enamel fragments and tooth enamel powder ages were presented for comparison. US-ESR, EU and LU models are calculated. Overall, the powder ages are consistent with previous uranium-lead and palaeomagnetic age estimates for the Aves Cave deposit, which suggest an age between ~3.15 and 2.61 Ma and provide the first ages for Milo's Cave dates to between ~3.1 and 2.7 Ma. The final ages were not overly dependent on the models used (US-ESR, LU or EU), which all overlap within error. These ages are all consistent with the biochronological age estimate (<3.4->2.6 Ma) based on the occurrence of Stage I Metridiochoerus andrewsi. Preliminary palaeomagnetic analysis from Milo's Cave indicates a reversal takes place at the site with predominantly intermediate directions, suggesting the deposit may date to the period between ~3.03 and 3.11 Ma within error of the ESR ages. This further suggests that there are no definitive examples of palaeocave deposits at Bolt's Farm older than 3.2 Ma. This research indicates that US-ESR dating has the potential to date fossil sites in the Cradle of Humankind to over 3 Ma. However, bulk sample analysis for US-ESR dating is recommended for sites over 3 Ma.

Two-phase kinematic evolution of the Qilian Shan, northern Tibetan Plateau: Initial Eocene−Oligocene deformation that accelerated in the mid-Miocene

The Cenozoic growth of the Tibetan Plateau and the distribution of deformation across it are a consequence of India-Asia collision and continued convergence, which have implications for studies of continental tectonics. The spatio-temporal development of Cenozoic deformation along the northern margin of the plateau is an important issue that can be better understood by testing various models of plateau growth. The northern Tibetan Plateau is bounded by the Cenozoic Qilian Shan thrust belt and the Haiyuan left-slip fault. We conducted geologic mapping, field observations, electron spin resonance (ESR) dating, and apatite (U-Th)/He (AHe) and apatite fission-track (AFT) analysis in the Qilian Shan thrust belt to improve our understanding of the timing of brittle faulting and range exhumation in the northern Tibetan Plateau. We document the first direct age constraints for Oligocene deformation within the central Qilian Shan via ESR dating, which correlates with AHe-AFT cooling ages in adjacent ranges. We demonstrate that the Qilian Shan thrust belt experienced a two-phase growth history, including Eocene−Oligocene fault-related uplift shortly after the India-Asia convergence, and mid-Miocene regional overprinting deformation that reactivated the proximal thrust faults. This deformational pattern suggests that the Qilian Shan thrust belt has experienced out-of-sequence development since the Eocene−Oligocene and has persisted as the stationary northeastern boundary of the Himalayan-Tibetan Orogen throughout the Cenozoic. The Paleozoic Qilian suture systems acted as a pre-existing weakness and played a decisive role in controlling the lithospheric rheology, which therefore impacted the timing, pattern, and strain distribution of Cenozoic deformation across the northern Tibetan Plateau.

ESR dating of optically-bleached quartz grains: Evaluating measurement repeatability and reproducibility

The true random uncertainty associated with ESR measurements of quartz grains at cryogenic temperature is currently unknown, as well as its impact on resulting equivalent dose (DE) estimates for ESR dating purpose. We provide here the results from the first quantitative evaluation study based on experimental data. Repeated single aliquot and multiple aliquot measurements of 100–200 μm quartz grains show that the random uncertainty (1σ) on the measurement of an individual aliquot usually lies in the range of 1–2%, 2–3 and 3–6% for the Al, Ti and Ti–H signals, respectively. These values are strongly sample and laboratory dependent, as they directly correlate with the signal-to-noise ratio associated with each signal, and may also be influenced by the stability of the experimental setup. The resulting variability of the DE values obtained from the multiple aliquot additive dose method over repeated measurements is estimated to 9%, 11% and 24% (1σ) on average for the Al, Ti and Ti–H signals, respectively.In the light of this outcome, the reliability of a dose estimate derived from one single measurement may be reasonably questioned, and we strongly advocate for the necessity to systematically carry out repeated measurements of a given quartz sample, a procedure that is far from being systematic within the community. Finally, our reproducibility experiments suggest that the experimental setup, measurement temperature or operator do not induce a significant bias in the dose evaluation, provided that repeated measurement are carried out. Our small-scale interlaboratory comparison shows consistent DE results for the Al and Ti signals, giving us some general confidence for the comparison of the dating results obtained by independent laboratories. We nevertheless acknowledge that a larger intercomparison study should be performed within the ESR dating community in order to confirm these initial results.

Hydrogen transfer reactions via organic radicals in gamma-irradiated chibaite.

Chibaite, a silica-framework structure with cage-like voids occupied by gaseous molecules, was found in marine sediments. Its formation age could be evaluated using electron spin resonance (ESR) if the radicals formed by natural radiation can be assumed to accumulate over time. To investigate whether hydrogen transfer reactions, where organic radicals withdraw hydrogen atoms from other molecules in adjacent cages, occur in chibaite and affect ESR dating, gamma-irradiated chibaite was measured by ESR. Methyl, ethyl, n-propyl, isopropyl, tert-butyl radicals and hydrogen atoms were created by gamma irradiation at 77K. The amount of tert-butyl radicals increased around 240K and the similar amount of the other organic radicals decreased simultaneously, implying that hydrogen transfer reactions occur between isobutane and the organic radicals in chibaite around 240K and therefore would have no influence on ESR dating because the reactions are completed at the environmental temperature.

Electron Spin Resonance Dating of the Quaternary Fluvial Terrace System of the Upper Han River, Central China

The geomorphology of the upper Han River, which is located in the southern Qinling Mountains (central China) and within the northern subtropical monsoon climate zone, contains abundant information on tectonic and climatic changes. Many Paleolithic sites are preserved in the Quaternary terraces in this region, making it an ideal area for studying both geomorphology and ancient human activity. However, owing to limitations in dating methods, the formation ages of the higher terraces T3–T5 of the upper Han River remain unclear. We collected 11 samples of sediment from the higher Quaternary terraces of Wufeng, Qingqu and the Yunyang Basin for electron spin resonance (ESR) dating of quartz grains. Results show that the formation ages of terraces T3, T4 and T5 are 422–401 ka, 627–621 ka and 1129–1099 ka, respectively. Integrating this information with the timings of documented climatic transitions and the history of regional uplift, we propose that the upper Han River terraces formed in response to the combined effects of climatic transition and tectonic uplift.

Preliminary comparison of close-range photogrammetric and microCT scanning: Surface Deviation Analysis of 3D digital models of hominin molar crowns

This study is a preliminary assessment of the viability of close-range photogrammetry in comparison to microCT scanning for the construction of 3D models of isolated molar crowns. Photogrammetric scanning is more cost-effective and less time-consuming than CT scanning, and in paleoanthropological contexts eliminates the possibility of exposing fossils to doses of radiation that affect ESR dating. Samples of fossil (Homo naledi), archaeological, and contemporary human molars were scanned via microCT and close-range photogrammetric scanning. The photogrammetric scans included 96 digital images per tooth and the resulting models were compared to their corresponding CT models using point-to-point Surface Deviation Analysis. The surface difference between the CT mesh models before and after processing functions such as smoothing and retriangulation was also assessed. Signed-rank tests comparing the surface difference between the two sets of mesh pairs show no significant difference in the level of deviation within the archaeological and contemporary molar samples. The Dinaledi sample demonstrates complementary results, as the majority of the photogrammetric meshes fall within a devised acceptable range of difference when compared to the processed CT meshes. A total of 81% of specimens in the study with suitable characteristics—a stained and unreflective crown surface—provided photogrammetric meshes that fell into this devised range. Crown characteristics that produced unsuitable models had unstained and reflective surfaces. Areas of higher deviation tend to occur in crenulations and fissures. The exploratory results suggest that sufficient reflectance and color contrast data must be present on the tooth enamel to create viable photogrammetric surface models, however further study is needed to fully understand the capabilities and limitations of close-range photogrammetry in comparison to microCT scanning.

16th International Conference on Luminescence and Electron Spin Resonance Dating, 13–17 September 2021

16th International Conference on Luminescence and Electron Spin Resonance Dating, 13–17 September 2021

Luminescence and ESR dating of the sedimentary infill from the multi-level cave system of Alkerdi-Zelaieta (Navarre, N Spain)

The finding of Upper Paleolithic engravings in 2016 triggered a multidisciplinary investigation of the Alkerdi cave system (Urdazubi, N Spain). The study of the speleogenetic processes led to the identification of at least 6 paragenetic cave levels with associated sedimentary infill. In order to unravel the timing of changes in the karst dynamics and to get some insights about sediment origin, two sediment samples were collected from cave levels 4 and 1 for numerical dating purpose, using both Optically Stimulated Luminescence (OSL) and Electron Spin Resonance (ESR) methods. One additional modern-age sample was also taken from the entrance of the karst to evaluate the magnitude of the optical bleaching achieved by the quartz grains before entering the cave system. Last, one sample was collected from a flowstone for U-series dating, providing independent age control. OSL measurements were carried out using small quartz multi-grain (MG) and single-grain (SG) Single Aliquot Regenerative-dose (SAR) protocol. Initial Equivalent Dose (D e ) results show evidence of saturated OSL signal for the sample of the higher level (with ∼60% of saturated aliquots). Unlike SA data, SG analyses do not meet the usual quality criteria (e.g., relatively high recuperation ratios, only a few grains with useable signal), suggesting that corresponding dating results should be treated with caution. Hence, both MG and SG TT-OSL and MG ESR methods were subsequently employed, as the corresponding signals are known to have higher saturation levels than OSL ones. ESR analyses were based on the Multiple Centre (MC) approach using the standard multi-grain multi-aliquot additive (MAA) dose method, while TT-OSL measurements were performed following Demuro et al. (2020). The latter, however, did not return any useful results for both samples. MC ESR data show the usual D e pattern (D e (Al)>D e (Ti op. D)>D e (Ti–H)) indicating that among the three ESR signals analyzed, the Ti–H most likely provides the closest estimate to the true burial age. However, low measurement repeatability and goodness-of-of fit indicate that the reliability of the ESR results may be reasonably questioned. Results derived from this multi-technique dating approach provide the first chronological constraints for the sedimentary infill of the Alkerdi cave system. In particular, they suggest that sediment deposition in Cave Level 4 (ALK-OSL01) occurred around 130 ka, which is in good agreement with the minimum age constraint given by the speleothem (80.5 ± 9.0 ka). In comparison, the young age obtained for sample ALK-OSL02 (5.0 ± 0.9 ka) suggests recent Holocene formation of the lowest cave level 1. Finally, the MG De value obtained for the modern sample is close to zero (<1 Gy), indicating that the OSL signal is almost fully reset at a multi-grain level before entering the cave. Additionally, despite the large De overdispersion measured in this modern sample, the De values are one to two order of magnitude lower than those obtained with the same model in the other two samples. Therefore, the large OSL D e overdispersion (OD) values of up to 64% obtained for the two samples from Cave Level 4 and 1 are most likely related to re-sedimentation processes inside the cave system.

Chronostratigraphy of a loess-paleosol sequence in the western Chinese Loess Plateau based on ESR dating and magnetostratigraphy

The western area of the Chinese Loess Plateau (CLP) is close to the northeastern margin of the Tibetan Plateau (NTP) and arid regions of northern China. Loess-paleosol sequence is a good archive for studying the variation of the East Asian summer monsoon (EASM) and the evolutionary history of paleoclimate. However, excessive remagnetization makes it challenging to infer the location of the time-scaled strata, and only a few high-resolution long scale paleomagnetic data are available from the western CLP. To solve this problem, this paper presents a study on establishing a Quaternary chronological framework using the traditional paleomagnetic method and quartz electron spin resonance (ESR) dating. The result is validated by comparing sequences in a variation of magnetic susceptibility and grain-size. Detailed thermal demagnetization records show that declination is reversed, but the inclination reversal is not apparent between S7 and S8. ESR estimated that the three samples collected at a depth of ∼112–145 m were 853.51 ± 133.43 ka, 962.12 ± 144.30 ka, and 1004.27 ± 206.86 ka, respectively. Constrained by these ESR dates, the age of the L9-L15 is defined as ∼0.9–1.2 Ma, which is corroborated the observation in the field stratigraphic survey, the characteristics of magnetic susceptibility and grain-size data. Based on these ages, the Matuyama and Brunhes boundary (MBB, ∼0.78 Ma) is deduced in L8 as inferred from the declination sequence. The bottom age of the loess-paleosol sequence extrapolated from the sedimentation rate is 2.13 Ma. The chronological sequence is therefore established. Several environmental indexes were changed coordinately in broad areas based on the chronological framework, indicating that it is logical and reliable.

Using X-rays as an irradiation source for direct ESR dating of fossil teeth

In this paper we have tested the potential application of X-rays as an irradiation source in Electron Spin Resonance dating of tooth enamel. A range of modern and fossil samples were used to assess the feasibility of dose estimations using this alternative irradiator. The use of a known laboratory additive dose allows the calculation of an absorption equivalent coefficient between gamma-rays and X-rays. The results show that equivalent doses obtained with gamma-rays on fossil powder enamel was frequently less than the doses obtained on fragments using only X-rays. This agrees with other studies that gamma irradiation can lead to age underestimation problems, and also indicates that X-ray sources could be more suitable for ESR dating. Here, we show that testing penetration attenuation for each individual irradiation source is required to accurately estimate the maximum enamel thickness and produce reliable protocols. We conclude that X-rays are an alternative irradiation source for ESR dating protocols, however, limitations remain in particular with alpha efficiency.

Thermal stability and closure temperature of barite for electron spin resonance dating

Electron spin resonance (ESR) dating has been applied to barite from hydrothermal vents. Barite in hydrothermal vents cools down rapidly after formation so little attention was paid to the thermal stability of the ESR signal of barite for dating. To discern multiple episodes of fluid flow or to date barite in other geological settings, it is essential to know how the ESR intensity decays with heat, the characteristic decay time and the closure temperature. In this study, we demonstrate that the decay of the ESR intensity of the SO 3 − radical in barite is a second-order reaction. The characteristic decay time for the ESR intensity to drop by half at 100 °C, 200 °C, 300 °C and 500 °C is of the order of magnitude of 10 6 years, 10 years, 10 h and 1 s respectively. The closure temperature of barite is generally between 190 and 340 °C. These results provide essential information on environments where the ESR intensity in barite is stable and conditions under which ESR ages can be erased. • ESR intensity of barite decreases rapidly between 300 and 400 °C. • The thermal decay of ESR intensity in barite is a second-order reaction. • The characteristic decay time is at least 8 Ma at 100 °C and 14 years at 200 °C. • The closure temperature is generally between 190 and 340 °C. • ESR dating of barite can be applied to a variety of geological settings.

Electron spin resonance dating of quartz from archaeological sites at Victoria Falls, Zambia

When electron spin resonance (ESR) is applied to sedimentary quartz, dealing with the poor bleachability of the signals is particularly challenging. In this study, we used both the single-grain optically stimulated luminescence (OSL) and the single aliquot ESR dating of quartz from deep sand deposits preserving a Stone Age archaeological sequence to combine the advantages of the two methods: good bleaching behaviour and extended age range. Using the youngest samples at each sampling site we were able to calculate the mean ESR residual age from the difference between the OSL ages and the apparent ESR ages. Focusing mainly on the single aliquot regenerative dose (SAR) protocol here, we were able to calculate the mean ESR residual age for the Ti and Al centres, including the non-bleachable signal component for the latter. For the NP site, residual ages of 209 ± 13 ka and 695 ± 23 ka were calculated for the two centres, whereas for the ZS site 268 ± 39 ka and 742 ± 118 ka were determined. These residual ages are significant and cannot be neglected. Thus, the residual age was subtracted from the apparent ESR ages. The validity of the residual subtraction method was tested through a comparison of the oldest OSL age from each site with the residual subtracted ESR age. For both NP and ZS sites, the residual subtracted Ti and Al ages were consistent with the OSL age within 2-σ uncertainty, and therefore confirm the robustness of the subtraction method. Within the NP sequence, we were able to locate the end of the Early Stone Age at 590 ± 86 ka, and this provides a maximum age for the transition to the Middle Stone Age in this part of south-central Africa.

The Cultural and Chronostratigraphic Context of a New Leaf Point from Hohle Fels Cave in the Ach Valley of Southwestern Germany

During the summer of 2020 the excavation team at Hohle Fels Cave in the Ach Valley of southwestern Germany recovered a leaf point (in German Blattspitze) made from gray Jurassic chert. The find is well-preserved and remarkable for a number of reasons. First this is the only leaf point recovered by a modern excavation in the Swabian Jura, and is the first leaf point discovered in situ since 1936, when Gustav Riek’s crew recovered two well-preserved leaf points at the excavation of Haldenstein Cave in the Lone Valley. The leaf point and associated finds originate from archaeological horizon (AH) X, 120 cm below the base of the rich Aurignacian deposits at the site that dates with radiocarbon to ca. 42 ka cal BP. Four ESR dates made on the teeth of large mammals from AH IX overlying the new leaf point yielded an average age of 62.5 ± 4 ka BP. This date represents a minimum age for the new horizons, which based on convention would be placed in the cultural taxonomic unit of the Blattspitzengruppe. Since the Blattspitzengruppe is typically interpreted as the last Middle Paleolithic cultural unit, we were intrigued to find an assemblage containing a Blattspitze in such an early chronostratigraphic context. While in Germany the Blattspitzengruppe is usually associated with the end of the Middle Paleolithic, many researchers across Europe have described these leaf point assemblages as being transitional industries at the interface between the Middle and Upper Paleolithic. Historically, some authors have even suggested a degree of cultural continuity between leaf point assemblages of the Middle and Upper Paleolithic. Here we present the stratigraphic and chronological context of the AH X and provide a preliminary description of the material cultural record from this horizon. Keeping in mind that we so far have only excavated parts of 6 m2 of the new find horizon and the underlying find horizon AH XI, the paper provides initial observations that will need revision as the excavation proceeds. These findings suggest that leaf points represent a feature in the technological repertoire of the Late Pleistocene Neanderthals of southwestern Germany rather than a reliable cultural stratigraphic marker for the last phase of the Middle Paleolithic.

ESR dating of quartz grains: Evaluating the performance of various cryogenic systems for dosimetric purpose

We present the results of the first detailed comparative and quantitative study of various cryogenic systems that can be used for ESR measurements of quartz grains. Three experimental setups were tested: (i) a standard liquid nitrogen Variable Temperature Unit (VTU), operating at 90–100 K and used in most ESR dating studies; (ii) a helium-based VTU that can reach measurement temperatures as low as 15–20 K; and a (iii) finger dewar filled with liquid nitrogen operating at 77 K.As expected, our results show significant gains in signal intensity and resolution when working at temperatures below 90 K, which is extremely useful when dealing with samples with weak intensities or poorly-resolved spectra. The improved signal resolution at 40 K allows the differentiation of the Ti–Li and Ti–H absorption lines around g = 1.913 that are typically merged at 90 K or above. It is therefore possible to extract the ESR intensity of a resolved Ti–Li signal for dating.The results obtained with each experimental configuration are highly consistent for both the Al and Ti centres. In particular, equivalent dose values obtained from eleven of the twelve samples analysed agree at a 1σ confidence level. The various cryogenic systems do no induce any significant systematic bias for ESR dose evaluation.