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Establishing chronologies of archaeological sites by using a single dating method may not always reliably constrain the age of a deposit or a fossil, as potential biases may naturally arise, particularly in complex sedimentary settings such as caves. In this study, we performed a multi-technique dating approach that targets different materials in two caves from the Cueva Mayor-Cueva del Silo karst system, Sierra de Atapuerca, Spain. Two new fossil teeth from lithostratigraphic unit LU4 (GE-I pit) at Galería de las Estatuas have been dated by combined U-series/ESR and Amino Acid Racemisation (AAR) methods. The former provides ages of 117 ± 13 and 87 ± 9 ka that agree with previous dating studies of this Neandertal site, confirming the assignment of level LU4 to Marine Isotope Stage (MIS) 5. In contrast, AAR analyses produce very scattered ages, pointing to significant post-burial chemical modifications in dentine. A first set of ages is presented for the Cata Litario pit at Sala de los Cíclopes, a palaeontological site formed exclusively of cave bear fossils belonging to the Middle Pleistocene species Ursus deningeri. We provide U-series/ESR and AAR ages for two bear teeth from lithostratigraphic unit LU5, and extended-range luminescence ages for the sediment deposits that host, and immediately underlie and overlie, the bear accumulation. Depositional ages of the sediment were obtained using single-grain thermally-transferred optically stimulated luminescence (TT-OSL) dating of individual quartz grains and post-infrared-infrared stimulated luminescence (pIR-IR) dating of K-feldspars. Several speleothems, both in situ and reworked fragments embedded in the different lithostratigraphic units, have additionally been dated by U-series to constrain the timing of the sequence formation. The results indicate that the sediment originally entered the cave between MIS-12 and MIS-10 (444 ± 28 ka to 367 ± 32 ka). Nevertheless, the AAR and U-series/ESR fossil ages, as well as some of the speleothem fragment ages from LUs 5 and 6 are significantly younger. Leaving aside methodologically questionable results for one of the bear tooth samples, the most reliable AAR and U-Series/ESR ages range from 287 ± 23 ka to 256 ± 24, while the speleothem fragments indicate several formation episodes between 444 ± 19 and 284 ± 8 ka. The apparent difference between the U-Series/ESR ages on the fossils and the luminescence ages on the host sediment are not likely to be wholly explained by uncertainties on uranium uptake modelling or gamma dose rate evaluation, and thus is most likely related to taphonomic processes or a complex site formation history. The presence of fossils and eroded speleothem clasts of younger age within these levels is consistent with either an event of prior erosion, transport and resedimentation of LUs 4, 5 and 6, and/or a complex post-depositional mixing history for the stratigraphic sequence at Cata Litario. This study highlights the importance of using different dating methods to reconstruct reliable chronological frameworks, and to understand the geological factors that can affect the dated materials. This includes the accumulation and taphonomic histories of fossils, post-depositional mixing or reworking processes affecting sediments during the residence time within the karst system. [ABSTRACT FROM AUTHOR]

Abstract The fossil evidence of hominins in China is crucial to understand the human evolution and dispersal in Eurasia. However, the dating of Chinese Early and Middle Pleistocene hominin record remains a serious problem. In this study, we applied coupled ESR/U-series dating method on Bailongdong hominin cave site in Hubei Province, central China, which is a key area to study early human migration between South and North China. The U-series analyses show that the fossil teeth samples from three horizons are close or beyond equilibrium, which indicate very early uptake or potential loss of uranium. Single saturation exponential fitting of 10 dose points irradiated up to 4 kGy was used for D E determination except one by double saturation exponential fitting with 16 dose points up to 63 kGy. Calculated by two uranium migration models, we obtain a weighted mean age of 509 ± 16 ka for five fossil teeth from layer 2. Combined with cosmogenic nuclides 26Al/10Be burial dating carried out on the cave deposits beneath the fossil layers in previous study, the multi-methods dating study places Bailongdong site at the early stage of Middle Pleistocene, and pinpoints the deposition of the fossil remains to the time of marine isotope stages 13. This is in agreement with the fauna composition and sedimentary characteristics which show a subtropical-tropical warm forest-grass environment. The multi-methods dating of Bailongdong site by both cosmogenic and coupled ESR/U-series methods is a good example for the future chronological studies of early human sites in China. Highlights • A Middle Pleistocene hominin site was dated by coupled ESR/U-series method. • Multi-methods dating study by ESR fossil dating and 26Al/10Be burial dating. • D E estimation by two fitting functions with different maximum doses was compared. [ABSTRACT FROM AUTHOR]

We use the uranium-series (U-Th) dating method to investigate the accuracy of a relative chronology based on laminae correlation between a pair of coeval twin stalagmites and compare their stable isotope and trace element records based on the two chronologies. U-Th dating shows that a relative chronology based on laminae correlation can be inaccurate: a hiatus in one of the stalagmites was not recognised, as well as more subtle changes in growth rates. Use of the stratigraphic correlation alone resulted in significant differences in the timing of stable isotopes and trace element peaks, with implications for their interpretation. Our results reveal the importance of a robust and direct chronology with which to interpret proxy data. Poor relative chronologies can lead to a misinterpretation of palaeoclimate data. The study reveals potential implications for speleothem records where proxy data and samples for dating were not taken in close proximity to each other and/or were correlated via laminae over distances of more than a few centimetres. [ABSTRACT FROM AUTHOR]

In situ U-series zircon dating has yielded unique insights into magmatic processes and the complexity of zircon crystallization. However, the approach requires some knowledge of the state of isotopic disequilibrium of the melt from which zircon crystallizes. Current practices for correcting initial 230 Th include use of an isochron array (defined by several coexisting zircons) or two-point isochrons based on a tie between each zircon and a common glass (or whole rock) measurement. However, magmas are complex and measured U/Th in zircons from a single extrusive can vary by up to a factor of seven, casting doubt on the assumption that a single glass composition is representative of the magma from which each zircon crystallized. We propose a correction scheme using the measured zircon 238 U/ 232 Th, a U/Th partition coefficient ratio between zircon and melt, and the observation that most magmas are within 15% (1σ) of the equiline. Using this correction scheme, we show that uncertainties can be underestimated by up to a factor of three and that published dates are potentially biased towards older ages. [ABSTRACT FROM AUTHOR]

Yumidong (Corn Cave) is a newly discovered Paleolithic site in the Three Gorges region of central China. Numerous Paleolithic artifacts have been excavated from the sedimentary deposits of the cave in association with faunal remains attributed to the Middle-Late Pleistocene Ailuropoda - Stegodon fauna of southern China. To establish the chronology of the sedimentary sequence (>5 m thick), 14C dating was applied to bone and charcoal samples (n = 6); the U-series method was used to date in situ precipitated speleothems (n = 12), transported speleothem samples (n = 6) and 18 subsamples of a fossil tooth; and the coupled ESR/U-series method was used to date fossil teeth (n = 6). The derived dates were combined using a hierarchical Bayesian approach to generate a unified chronostratigraphy for the Yumidong sequence. In our Bayesian analyses, the 14C and coupled ESR/U-series dates were considered to provide direct age estimates for the target layers, while the U-series dates of the in situ precipitated speleothems and fossil tooth were used as minimum age constraints and those of the transported speleothem fragments as maximum age constraints. The Bayesian analyses provided robust time intervals for the archeological layers: L2-Upper (14–23 ka), L2-Lower (27–63 ka), L3 (106–171 ka), L4 (140–192 ka), L10 (157–229 ka), L11 (181–256 ka), and L12 (214–274 ka) with a probability of 95%, allowing the establishment of a ∼300 ka long geological and archeological history for the Yumidong site and placing it as a reference site for Paleolithic cultural evolution in the Three Gorges region from the late Middle Pleistocene to Late Pleistocene. [ABSTRACT FROM AUTHOR]

Abstract: Cave sequences provide some of the most important archives of Palaeolithic archaeology that are currently available. The potential value of such sequences is, however, frequently limited by the problems associated with constructing robust chronologies for archaeologically significant levels. In this study, we apply 230Th/U and OSL SAR techniques to the dating of deposits from the Calcareous Group at Grotte des Pigeons, Taforalt, eastern Morocco. The advantage of combining these techniques is: 1) they allow the cross-checking of chronologies derived from independent sets of measurements and assumptions, and 2) they date different facies of cave sediments (i.e. clastic cave sediments as opposed to cave precipitates such as speleothems) allowing the timing of deposition by different cave processes to be constrained more robustly. The age estimates derived by these techniques from different sampling locations are in good agreement with one another, suggesting the potential of these techniques when used in tandem for producing more robust chronologies of Palaeolithic sequences. The deposition of the Calcareous Group is placed within the middle to late part of MIS 5 (MIS 5c to 5a). Furthermore, the Bayesian analysis of the dates derived in this study along with those that have been previously published, allows the duration of deposition of this unit to be estimated at 25.4 ± 3.7 ka (mean ± 1σ). The paper concludes by discussing the significance of these ages for the archaeology of the Taforalt sequence. We suggest that the collection of samples for multiple independent dating methods in direct association combined with the use of careful, stratigraphic constraints in Bayesian models results in the most robust dates available for such cave sequences. [Copyright &y& Elsevier]

Abstract: The Sidi Messaoud site provides a 40m thick sedimentary infilling of great importance for the study of environmental changes and landscape evolution during the Upper Pleistocene in the Western Sahara. In this study, chronological results obtained by the 14C, U-series and optical dating techniques are compared. Each individual age, depositional environment and post-deposition history of the various samples are evaluated, in order to explain the methodological reasons for discordances and concordances. Stratigraphic and palaeoenvironmental implications for the last 120ka history in southwestern Morocco are also inferred: the wadi Noun gorges had been incised before MIS 5, and later, during MIS 3, the valley has been filled in with a mean sedimentation rate of ∼1m/ka. [Copyright &y& Elsevier]

Abstract: ESR dating was carried out on Cervus elaphus tooth enamel samples from the depositional sequence of Lazaret Cave, Nice, France. The deposits contain Anteneandertal hominid fossils associated with abundant lithic artefacts and faunal remains. Three samples from the Mousterian occupations in complex CIII (Fouille d''entrée) yielded early uptake (EU) ages between 108 and 125ka and linear uptake (LU) ages between 133 and 160ka. Seven samples from the Acheulian levels in the upper part of the complex CII (Fouille d''entrée and Fouille centre) gave EU ages between 113 and 165ka and LU ages between 147 and 210ka, with weighted means at 131±7 and 165±9ka, respectively. The results of six enamel samples from the lower Acheulian levels at Locus VIII, another place in the cave, were discarded because of their decreasing tendency with depth. The US–ESR combination method was also applied and the CSUS–ESR dates were calculated using the ESR-DATA program. Altogether, the data suggest that the Lazaret Acheulian and Mousterian occupations were rapidly formed during OIS 6. [Copyright &y& Elsevier]

Abstract: The archaeological site of Payre (France) yielded Middle Palaeolithic layers with Neanderthal remains, which are partly bracketed by two stalagmitic flowstones. To obtain a precise chronological framework for the human occupation and the faunal remains of this site, several dating methods were used: uranium-series (U-series by alpha spectrometry and TIMS) and electron spin resonance (ESR) on stalagmitic flowstones, combined ESR/U-series on teeth and bones, and thermoluminescence (TL) on burnt flints. Most of the ages obtained for levels H to C range from ∼300 to ∼140ka. The age-spread obtained for the anthropic (burnt flints) and faunal remains (bones and teeth) suggests that the dated levels represent several human occupation periods, near the transition from MIS8 to MIS7 (levels G–F) and from MIS6 to MIS5 (levels D–E). [Copyright &y& Elsevier]

Abstract: Electron spin resonance (ESR) dating on teeth has been used to determine the antiquity of the human presence in the area of Gunung Sewu (East Java, Indonesia). The Song Terus cave is one of the archaeological sites located in this area, which has yielded an important collection of fossil bones and prehistoric lithic industry. ESR dating shows that this cave belongs to a karstic system which has been in place since Middle Pleistocene. The results of coupled ESR/Uranium-series dating indicates closed system for uranium in tooth tissues yielding ages of between 216 and 392ka for the oldest archaeological levels, confirming the possibility of finding Middle Pleistocene human occupations in such karstic sites in Java. [Copyright &y& Elsevier]

Abstract: Building upon the work of Richards et al. [1998. U–Pb dating of a speleothem of Quaternary age. Geochimica et Cosmochimica Acta 62, 3683–3688], we have developed a method for precise dating of speleothems beyond the range of the U–Th technique using the U–Pb decay scheme. By coupling low-blank sample preparation procedures and multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) analytical methodologies developed for low-level Pb-isotope analysis, we find that, under ideal circumstances (radiogenic speleothems with very low common Pb), U–Pb dating of speleothems is not only possible, but also produces excellent age resolution—often comparable to or better than U–Th studies. Corrections for initial isotopic disequilibrium are necessary and exert a strong control on the achievable age uncertainty. The technique will be of immediate benefit in extending speleothem-based climate proxy records beyond ∼500ka and will also find other uses, such as the dating of associated sub-fossil remains, and providing constraints on rates of landscape evolution and neo-tectonic processes. Here we present initial results for speleothems from the Nullarbor Plain, Western Australia, and the Alpi Apuane, Italy. The Nullarbor samples provide important new constraints on the development of aridity in Australia during the late Tertiary/early Quaternary, while the Apuane samples offer insights into the landscape history and uplift of that region. [Copyright &y& Elsevier]

Basaltic lavas provide a window into their mantle sources and the associated geodynamic processes associated with them. Obtaining absolute chronology on young basalt flows is often challenging. Some gypsum crusts in pyro-duct (lava tube) caves crystallize during the last "cooling" stages of tube formation probably at relatively low temperatures (i.e., <100 °C). Here we propose uranium-series dating of these 'speleogenetic' gypsum crusts as a way to establish the ages of young basalt flows. We demonstrate the technique using cave crusts from four young basalt flows in El Malpais National Monument, New Mexico, three of which are moderately well-dated by alternative methods (14C, 36Cl, and 3He ages). They all exhibit well-formed lava tube systems that contain gypsum crust speleothems interpreted to be remnant of the volcanic sulfur or sulfate processes when the tube systems were active during their terminal stages. δ18O SO4 , δ34S, 87Sr/86Sr, and δ234U values for the gypsum crusts have near-basaltic signatures, and the crusts contain uranium concentrations suitable for uranium-series dating in three of these four basalt flows. Analyses of gypsum from caves of two well-dated basalt flows yielded uranium-series ages that agree with the ages determined by other techniques showing that absolute ages of young basalt flows can be achieved by this method. The fourth flow, the Hoya de Cibola basalt, previously undated by other absolute means has a U–Th gypsum crust isochron age of 16.9 ± 0.9 ka. The uranium-series age and isotopic analyses of these gypsum crusts should be useful in geologic applications involving young basalt flows. [ABSTRACT FROM AUTHOR]