Description: Publication date: Available online 24 December 2014 Source: Quaternary Geochronology Author(s): M.D. Bateman , S. Stein , R.A. Ashurst , K. Selby Establishing a robust chronology is fundamental to most palaeoenvironmental studies. However, the number and positioning of dated points is critical. Using a portable luminescence reader, it is possible to rapidly generate high resolution down core relative age profiles. Profiles of portable luminescence data from two coastal dunes were evaluated and compared with the results of particle size analysis, stratigraphy, and an independent historical chronology. Results show that, even in young samples, portable luminescence data is dominated by an age related signal which in homogeneous sediment need not be corrected for moisture, feldspar content changes or grain size. Profiles therefore provide relative chronologies from which accumulation phases can be established, and from which better targeted sampling and comparison to other sites could be undertaken. Even though they do not provide instant absolute chronologies, field-based portable luminescence profiling of Late Quaternary sites hold much potential to improve the resultant chronologies.

Description: Publication date: Available online 15 December 2014 Source: Quaternary Geochronology Author(s): O. Trandafir , A. Timar-Gabor , C. Schmidt , D. Veres , M. Anghelinu , U. Hambach , S. Simon Previous works focused on optically stimulated luminescence dating of quartz extracted from Romanian and Serbian loess reported significant discrepancies between ages obtained on fine (4-11 μm) and coarse (63-90 μm) quartz. The present study is directed at expanding these investigations. The SAR-OSL and double SAR-OSL protocols are applied on quartz of different grain sizes belonging to 9 samples extracted from a newly identified archaeological site at Bistricioara-Lutărie III on the Bistrița Valley (NE Romania). Radiocarbon ages are also obtained for the 3 uppermost cultural layers hosted in the loess-like deposit. Discrepant ages are obtained between fine (4-11 μm) and coarse (63-90 and 90-200 μm, respectively) quartz for equivalent doses higher than ∼80-100 Gy. However, a very good agreement is achieved for the youngest sample, with an age of ∼8 ka (with a D e of 38 Gy for fine and 35 Gy for coarse grains, respectively). The comparison with independent control provided by radiocarbon dating suggests better agreement of ages calculated for coarse quartz. Our results are once again proof that concerns should be raised regarding the reliability of the equivalent doses obtained on quartz samples for which the laboratory dose response cannot be fitted by a single saturating exponential function. Further systematic investigations are required regarding the very different saturation characteristics of fine and coarse grained quartz.

Description: Publication date: Available online 15 December 2014 Source: Quaternary Geochronology Author(s): Guillaume Guérin , Mayank Jain , Kristina Thomsen , Andrew Murray , Norbert Mercier Single grain OSL has become a widely used approach in Quaternary geochronology. However, the origins of D e distributions and the sources of variation in individual dose estimates are still poorly understood. The amount of scatter in these distributions on top of the known uncertainties in measurement and analysis is defined by overdispersion and this quantity is generally used for weighting individual D e values to calculate a central equivalent dose. In this study, we address the nature and amount of different sources of dispersion in quartz single grain D e estimates, by (i) using appropriate statistical tools to characterize D e populations and (ii) modelling, with a specifically designed Geant4 code, dose rate distributions arising from the presence of potassium feldspar grains in well-sorted sands. The model uses Monte Carlo simulations of beta emissions and interactions in a random close packing of quartz and feldspar spheres representing a sand sample. Based on the simulation results, we explain the discrepancy between intrinsic and natural overdispersion values in a well-bleached sample, thus validating the model. The three parameters having the most influence on dispersion in dose rate distributions, and modelled in this study, appear to be grain size, potassium content and total dose rate. Finally an analysis of measurement uncertainties and other sources of variations in equivalent dose estimates leads us to conclude that all age models (both logged and unlogged) which include an overdispersion value to weight individual D e values rely mainly on unknown parameters; this ignorance may lead to an inadvertent bias in D e estimates. Assuming counting statistics make a small contribution to dispersion (as is often the case), we suggest that in some cases it is most appropriate to use unweighted averages of equivalent doses when dividing by commonly measured average dose rates.

Description: Publication date: Available online 11 December 2014 Source: Quaternary Geochronology Author(s): Christina M. Neudorf , Olav B. Lian , Ian J. Walker , Dan H. Shugar , Jordan B.R. Eamer , Libby C.M. Griffin The Quaternary geology of British Columbia’s central coast contains a rich and complex record of glacial activity, post-glacial sea level and landscape change, and early human occupation spanning the last ∼10,000 years. At present, however, this region remains a largely understudied portion of coastal North America. This study describes the luminescence characteristics of quartz and K-feldspar from coastal dune and beach sands on Calvert Island and develops a suitable luminescence dating protocol that will allow for a more rigorous chronology for post-glacial landscape evolution and human occupation on BC’s central coast. Luminescence signals from Calvert Island quartz are dim, and appear to lack the so-called “fast” component that is most desirable for optical dating. K-feldspar signals are sufficiently bright for optical dating. We test and refine a single-aliquot regenerative-dose (SAR) protocol for K-feldspar specific to Calvert Island samples through a series of dose recovery and preheat plateau tests. Two approaches for correcting a sample age for anomalous fading are compared and a correction for phototransfer is introduced and applied. Measured fading rates vary from sample to sample implying that, in this region, it is not sufficient to rely on two or three representative fading rates as has sometimes been done elsewhere. Refined age estimates show consistency with independent radiocarbon dating control and help identify radiocarbon-dated organic-rich sediments that have been reworked.

Description: Publication date: February 2015 Source: Quaternary Geochronology, Volume 25 Author(s): Ulrike Proske , Rachel Wood , Stewart Fallon , Janelle Stevenson Sample preparation protocols for concentrating organic material from sediments for radiocarbon dating often include a large number of steps and the use of hazardous chemicals. Thus, these protocols are often problematic for pollen-poor sediments as material can get lost or may become degraded. Pyrite in samples for radiocarbon dating hinders an effective graphitisation process and thus needs to be removed during sample preparation. Standard protocols require the use of nitric acid, a strong oxidant that corrodes organic material. Therefore, the use of nitric acid needs to be avoided when preparing pollen-poor but pyrite-rich sediments. We present a method that minimises the sample preparation steps by replacing acid treatment with heavy liquid separation. Using non-toxic LST at a density of 2.0 g cm −3 is shown to be effective for separating the organic fraction from sulphides, silicates and carbonates. We applied this method to pyrite-rich and pollen-poor sediments from Western Australia that had previously been problematic to date. The successful AMS radiocarbon dating of all samples pre-treated with LST demonstrates the effectiveness of this method.

Description: Publication date: Available online 4 December 2014 Source: Quaternary Geochronology Author(s): M. Jagercikova , S. Cornu , D. Bourlès , P. Antoine , M. Mayor , V. Guillou Meteoric 10 Be, due to its high affinity with soil and sediment particles, is widely used in geomorphologic and environmental studies attempting to evaluate the soil production/denudation rates or soil ages up to 10 7 years. However, the evolution of the 10 Be distribution as a function of depth is poorly known in soils as revealed by recent reviews ( Graly et al., 2010 ; Willenbring and von Blanckenburg, 2010). In this study, 10 Be concentrations in the bulk and the 0-2 μm (lutum) granulometric fraction of samples along Luvisols profiles developed from loess in Northern France have been measured. The bulk 10 Be concentrations are significantly higher in one of the three sites, likely reflecting differences in the inherited 10 Be concentrations of the loess parent material as well as in the accumulation rates of the later. However, the bulk 10 Be concentrations along all profiles are significantly correlated with the lutum (0-2 μm fraction) content, the maximum 10 Be concentrations being evidenced in the Bt-horizon. Dominant adsorption of 10 Be to the lutum has been furthermore corroborated by the mass-balance calculations with as much as 79.8 ± 9.0 % of 10 Be being associated with the lutum. Contrary to the bulk 10 Be concentrations, the lutum 10 Be concentrations showed several maxima coinciding with shifts in the coarse to fine silt ratio. This was interpreted as a change in the loess deposit dynamic. Finally, using numerical modeling approach based on the advection-diffusion equation, an average downward migration of 10 Be by clay translocation was estimated. It ranges from 0.01 to 0.08 cm yr –1 . Inherited 10 Be in the loess parent material represented from 64 to 71 % of the total 10 Be content in the simulated soils. Vertical 10 Be distributions and their maximum concentrations in the Bt-horizon thus mainly result from redistribution of the inherited 10 Be by clay translocation and bioturbation.

Description: Publication date: February 2015 Source: Quaternary Geochronology, Volume 25 Author(s): Barbara Fiałkiewicz-Kozieł , Piotr Kołaczek , Adam Michczyński , Natalia Piotrowska The main aim of this paper is to present the pitfalls connected with the construction of reliable chronologies for anthropogenically disturbed peatlands over the last two millennia based on 210 Pb and 14 C dating, i.e. the period of the strongest human impact on these ecosystems. The following hypotheses have been formulated: i) parts of peatlands suspected to be affected by peat extraction may possess traces of mechanical disturbances undetectable using different analyses based on biota proxy; ii) failure to consider information included in radionuclide date inversions may contribute to the establishment of misleading chronologies. To test these hypotheses, different scenarios of chronology based on high resolution 210 Pb and 14 C dating from a peat core retrieved from the Puścizna Krauszowska bog (southern Poland) have been analysed. Nowadays, this mire is intensively exploited by humans; however, it contains remains of dome considered undisturbed, from which the core presented in this paper was collected. The set of dates revealed the presence of marked 14 C date inversions (mechanical disturbances) which, if inappropriately interpreted before the age–depth modelling process, may lead to the establishment of misleading chronologies, and thus an incorrect interpretation of biota proxy records, e.g. pollen. Those sections of peat profiles with prominent age inversions and/or strong discrepancies between the peat accumulation rate and bulk density should be rejected from age–depth modelling, even if interpretable chronologies can be obtained.

Description: Publication date: February 2015 Source: Quaternary Geochronology, Volume 25 Author(s): W. Derek Hamilton , Jane Kenney In recent years, the use of Bayesian statistical analysis for modelling radiocarbon dates has become much more commonplace within archaeology, however there remains very little literature to aid new practitioners with understanding the archaeological assumptions that underpin many of the modelling choices. Using a suite of radiocarbon dates from a sample of seven ovens, from the 18 excavated across the site at Ysgol yr Hendre, Caernarfon, North Wales, this paper explores the various methods of modelling this group of features. It stresses the underlying archaeological assumptions of each model, while also highlighting some of the tools that should especially be considered when developing very precise models. Finally it compares the results of the models.

Description: Publication date: February 2015 Source: Quaternary Geochronology, Volume 25 Author(s): Guaciara M. Santos , Roberto Linares , Claudio S. Lisi , Mario Tomazello Filho This work reports the first high-precision 14 C-AMS dating of holocellulose from a Brazilian subtropical species for the period 1927–1997, with the goal to identify suitable Southern American tree species that will serve as benchmarks for improving the calibration of the 14 C time-scale for the Southern Hemisphere (SH). The tree rings analyzed here came from a single tree of Paraná pine ( Araucaria angustifolia ) growing at 22°50′S, 46°04′W (Camanducaia, Minas Gerais, Brazil). A slight depletion of atmospheric 14 C after 1927 AD was observed, due to the Suess effect. Our 14 C results also showed the rise and rapid decrease of atmospheric 14 C concentrations associated with the detonation of nuclear weapons during the late 50s, and its subsequent uptake by other large C sinks. Current 14 C data can be used for the study of the global carbon cycle, forensic sciences applications, and the determination of the age and growth rate of tropical trees without annual ring patterns. The remarkable overall agreement of our tree-ring/ 14 C data with the SH Zone 1–2 compilation dataset shows this subtropical tree species' potential to refine the 14 C calibration curve.

Description: Publication date: Available online 3 December 2014 Source: Quaternary Geochronology Author(s): Eva Panagiotakopulu , Thomas F.G. Higham , Paul C. Buckland , Jennifer A. Tripp , Robert E.M. Hedges Results from AMS dating applied to insect chitin from a variety of contexts and different preservation conditions and retrieval methods are presented. Secure contexts, which include other dated organic material from different geographic locations ranging from Egypt to Greenland and different chronological periods, from Lateglacial to Medieval, have been used. In addition, insect species with different dietary requirements have been selected for dating purposes in order to provide an understanding as to whether diet plays a role in the chitin dating results. Dates from each context/site are discussed separately in the context of their stratigraphy and/or archaeology. Our research concentrates on the results from pre-treatment methods which require small quantities of chitin as these could be applied in a variety of Quaternary and archaeological contexts. The dates from carbonised and desiccated remains where no chemicals had been involved in storage fell within the range of dates from other organics or the archaeology. Although some of the dates from waterlogged contexts were successful, problems were encountered and these have been linked with long term storage in various alcohols of uncertain provenance. Whilst short term immersion in paraffin (kerosene) and alcohols during processing probably has no impact, it is recommended that chitinous material for dating be stored in acidified distilled water. Our results demonstrate the potential of chitin as a dating medium and provide a basis for its wider application.