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: 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 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: Available online 3 December 2014 Source: Quaternary Geochronology Author(s): S. Carretier , V. Regard , R. Vassallo , G. Aguilar , J. Martinod , R. Riquelme , F. Christophoul , R. Charrier , E. Gayer , M. Farías , L. Audin , C. Lagane Cosmogenic nuclides in river sediment have been used to quantify catchment-mean erosion rates. Nevertheless, variable differences in B 10 e concentrations according to grain size have been reported. We analyzed these differences in eleven catchments on the western side of the Andes, covering contrasting climates and slopes. The data include eight sand (0.5-1 mm) and gravel (1-3 cm) pairs and twelve sand (0.5-1 mm) and pebble (5-10 cm) pairs. The difference observed in three pairs can be explained by a difference in the provenance of the sand and coarser sediment. The other sand-pebble pairs show a lower B 10 e concentration in the pebbles, except for one pair that shows similar concentrations. Two sand-gravel pairs show a lower B 10 e concentration in the gravel and the other five pairs show a higher B 10 e concentration in the gravel. Differences in climate do not reveal a particular influence on the B 10 e concentration between pairs. The analysis supports a model where pebbles and gravel are mainly derived from catchment areas that are eroding at a faster rate. The five gravel samples with high B 10 e concentrations probably contain gravel that were derived from the abrasion of cobbles exhumed at high elevations. In order to validate this model, further work should test if pebbles are preferentially exhumed from high erosion rate areas, and if the difference between pebbles with high B 10 e concentrations and sand decreases when the erosion rate tends to be homogeneous within a catchment.

Description: Publication date: Available online 30 September 2014 Source: Quaternary Geochronology Author(s): David C. Argento , John O. Stone , Robert C. Reedy , Keran O'Brien We present a comprehensive, nuclear-physics-based cosmogenic nuclide production rate model combining radiation transport modeling with excitation functions for commonly measured nuclides. This model allows investigation of factors influencing nuclide production, such as the energy spectrum and angular distribution of the incident radiation that cannot be easily isolated in calibration measurements on natural samples. We present neutron and proton fluxes over a range of atmospheric depths and cut-off rigidities. Calculated production rates for 3 He, 10 Be, 14 C, 21 Ne, 26 Al, and 36 Cl based on these fluxes are presented. The model predicts that production rates for these nuclides diverge from one another with altitude, hence that production ratios depend on altitude. Compared to existing scaling schemes, the model predicts a larger difference between sea-level production rates at low and high latitude.

Description: Publication date: Available online 30 September 2014 Source: Quaternary Geochronology Author(s): Beatrice Demarchi , Emily Clements , Mauro Coltorti , Renée van de Locht , Roland Kröger , Kirsty Penkman , James Rose This work focuses on the bivalve Glycymeris , commonly used in classic amino acid racemisation (AAR) studies in the Mediterranean, as part of an extensive assessment of the suitability of intra-crystalline protein diagenesis (IcPD) dating. We test the closed system behaviour (a prerequisite for IcPD studies) of Glycymeris through bleaching and heating studies, as well as fossil material sourced from Last Interglacial deposits in Sardinia (Calamosca), Mallorca (Palma Bay) and Tunisia (Hergla). Although bleaching appears to be effective in isolating an intra-crystalline fraction of proteins, this fraction may not behave as a closed system in all molluscan taxa, as we verify here for some of the fossil Glycymeris . We show that open-system behaviour can be identified by analysing the co-variance between FAA and THAA fractions and the relative THAA composition and we also provide further evidence that, for taphonomic reasons, dating the molluscan fauna does not necessarily yield age information for the sedimentary units when these contain derived shells.

Description: Publication date: Available online 16 September 2014 Source: Quaternary Geochronology Author(s): B. Guralnik , C. Ankjærgaard , M. Jain , A.S. Murray , A. Müller , M. Wälle , S.E. Lowick , F. Preusser , E.J. Rhodes , T.-S. Wu , G. Mathew , F. Herman Optically stimulated luminescence (OSL) thermochronometery is an emerging application, whose capability to record sub-Million-year thermal histories is of increasing interest to a growing number of subdisciplines of Quaternary research. However, several recent studies have encountered difficulties both in extraction of OSL signals from bedrock quartz, and in their thermochronometric interpretation, thus highlighting the need for a methodological benchmark. Here, we investigate the characteristic OSL signals from quartz samples across all major types of bedrock and covering a wide range of chemical purities. High ratios of infrared to blue stimulated luminescence (IRSL/BLSL), an insensitive ‘fast’ OSL component, and anomalously short recombination lifetimes seen in time-resolved luminescence (TR-OSL), are often encountered in quartz from crystalline (magmatic and metamorphic) bedrock, and may hamper successful OSL dating. Furthermore, even when the desirable signal is present, its concentration might be indistinguishable from its environmental steady-state prediction, thus preventing its conversion to a cooling or heating history. We explore the saturation properties and the thermal activation parameters of various OSL signals in quartz to outline the capabilities and limitations for their use in low-temperature thermochronometry.

Description: Publication date: Available online 16 September 2014 Source: Quaternary Geochronology Author(s): Tony Reimann , Paul D. Notenboom , Matthieu A. De Schipper , Jakob Wallinga We present a multiple luminescence signal measurement procedure that simultaneously measures six different luminescence signals from a single polymineral aliquot (i.e. multiple-signal, short MS-SAR approach). The six signals show different bleaching rates in bleaching experiments, ranging from rapid bleaching for the quartz dominated blue stimulated luminescence signal (measured at 125 °C, BSL-125), to the slow-bleaching polymineral thermoluminescence signal. The bleaching rate of the infrared stimulated luminescence (IRSL) measured at room temperature (IR-25) and elevated temperature post-IR IRSL (pIRIR-90, pIRIR-155, pIRIR-225) signals decrease with increasing measurement temperature. Owing to these different bleaching rates, the MS-SAR approach allows inference of the degree of bleaching, and thereby information on the transport history of sediments. We test this approach by applying the MS-SAR to four coastal samples from a well-monitored sand-nourishment site at the Dutch coast. Our results show that the proposed MS-SAR approach can be utilised to construct bleaching plateaus which provide an independent and time-effective measure of the degree of poor bleaching in a sediment sample based on the measurement of only a few large aliquots. We propose that the MS-SAR protocol can be used to profile the age, luminescence properties and degree of bleaching of minimal prepared polymineral. This pre-profiling will allow the selection of suitable samples for full luminescence dating analysis in a target-orientated and time-effective manner.

Description: Publication date: Available online 10 September 2014 Source: Quaternary Geochronology Author(s): David A. Grimley , Eric A. Oches Amino acid racemization (AAR) values measured in gastropod shells are demonstrated to be an important aid for correlations and chronology of fossiliferous loessal, lacustrine, and alluvial Pleistocene units in Illinois, central USA. Aspartic acid (Asx) and Glutamic acid (Glx) D/L values were analyzed on a total of 167 Succinea , Hendersonia , and Pomatiopsis shells from 9 geologic units, with clear stratigraphic relationships, at a total of 18 localities in central and southern Illinois. AAR data from Hendersonia and Succinea are less variable and more normally distributed than Pomatiopsis data, but the latter are locally useful for units lacking preferred genera. Based on analysis of variance tests, Asx- and Glx-D/L data can confidently distinguish among Wisconsin Episode (MIS 2 – 3), Illinois Episode (MIS 6), late pre-Illinois Episode (MIS 8 – 14), and early pre-Illinois Episode (MIS 20) deposits. Last glacial Peoria Silt (MIS 2) and Roxana Silt (MIS 3), have mean Asx-D/L values of 0.34 – 0.37 and 0.42 – 0.43, respectively, considering all genera. The Illinois Episode Petersburg Silt (∼150 ka) has Asx-D/L (Ā: 0.50 – 0.56) and Glx- D/L (Ā: 0.17 – 0.22) ratios that are statistically distinctive from other units. Three late pre-Illinois Episode units (Harkness Silt Member, Belgium Member, and Banner silt units) have similar Asx D/L values (Ā: 0.63 – 0.71) and, along with stratigraphic context, confirm extensive middle Pleistocene glaciations in the region. Using parabolic kinetic age models, depositional ages of ∼ 550 – 250 ka (MIS 14 – 8) are implied for these units, with a favored correlation with MIS 12 (∼450 ka), a time of especially high global ice volume. The Canteen member, a preglacial alluvium-colluvium below the Harkness Silt, is statistically indistinguishable from other pre-Illinois Episode units with AAR data, but was likely deposited during ∼ 660 – 480 ka (MIS 16 or 14), based on parabolic age estimates. The paleomagnetically reversed County Line silt (∼780 – 830 ka: MIS 20), with the highest mean AAR values, is the oldest known gastropod-bearing Pleistocene unit in Illinois.

Description: Publication date: Available online 7 September 2014 Source: Quaternary Geochronology Author(s): P.-H. Blard , G. Balco , P.G. Burnard , K.A. Farley , C.R. Fenton , R. Friedrich , A.J.T. Jull , S. Niedermann , R. Pik , J.M. Schaefer , E.M. Scott , D.L. Shuster , F.M. Stuart , M. Stute , B. Tibari , G. Winckler , L. Zimmermann This study reports an inter-laboratory comparison of the 3 He and 4 He concentrations measured in the pyroxene material CRONUS-P. This forms part of the CRONUS-Earth and CRONUS-EU programs, which also produced a series of natural reference materials for in situ produced 26 Al, 10 Be, 14 C, 21 Ne and 36 Cl. Six laboratories (GFZ Potsdam, Caltech Pasadena, CRPG Nancy, SUERC Glasgow BGC Berkeley, Lamont New York) participated in this intercomparison experiment, analyzing between 5 and 22 aliquots each. Intra-laboratory results yield 3 He concentrations that are consistent with the reported analytical uncertainties, which suggests that 3 He is homogeneous within CRONUS-P. The inter-laboratory dataset (66 determinations from the 6 different labs) is characterized by a global weighted mean of (5.02±0.12)×10 9 at.g -1 with an overdispersion of 5.6% (2σ). 4 He is characterized by a larger variability than 3 He, and by an inter-lab global weighted mean of (3.60±0.18)×10 13 at.g -1 (2σ) with an overdispersion of 10.4% (2σ). There are, however, some systematic differences between the six laboratories. More precisely, 2 laboratories obtained mean 3 He concentrations that are about 6% higher than the clustered other 4 laboratories. This systematic bias is larger than the analytical uncertainty and not related to the CRONUS-P material (see Schaefer et al., same issue ). Reasons for these inter-laboratory offsets are difficult to identify but are discussed below. To improve the precision of cosmogenic 3 He dating, we suggest that future studies presenting cosmogenic 3 He results also report the 3 He concentration measured in the CRONUS-P material in the lab(s) used in a given study.