DRAC: Dose Rate and Age Calculator for trapped charge dating

Accurate calculation of the environmental radiation dose rate (Ḋ) is an essential part of trapped charge dating methods, such as luminescence and electron spin resonance dating. Although the calculation of Ḋ is not mathematically complex, the incorporation of multiple variables and the propagation of uncertainties can be challenging. The Dose Rate and Age Calculator (DRAC) is an open access, web-based program which enables rapid Ḋ calculation for trapped charge dating applications. Users can select from recently published attenuation and conversion factors to make mathematically robust, reproducible Ḋ calculations. Comparison of DRAC calculated Ḋ values against the published Ḋ determinations of 422 samples from 32 studies results in a reproducibility ratio of 1.01 ± 0.05. It is anticipated that DRAC will facilitate easier inter-laboratory comparisons and will provide greater transparency for Ḋ calculations. DRAC will be updated to reflect the latest advances in Ḋ calculation and is freely accessible at www.aber.ac.uk/alrl/drac. The code for DRAC is available from github at https://github.com/DRAC-calculator/DRAC-calculator.     

ESR dating of dental enamel from Middle Palaeolithic levels at Lazaret Cave,France

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 125 ka and linear uptake (LU) ages between 133 and 160 ka. 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 165 ka and LU ages between 147 and 210 ka, with weighted means at 131 ± 7 and 165 ± 9 ka, 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.     

Selection of spectrum- and seismo-compatible accelerograms for the Tuscany region in Central Italy

This article illustrates the results of a study aimed at developing a methodology for the automatic identification of the seismic input at outcropping rock sites and flat topographic conditions necessary to carry out non-linear dynamic analysis of structures and geotechnical systems. The seismic input is provided in terms of a set of 7 natural accelerograms recorded on outcropping rock and satisfying the average spectral compatibility requirements prescribed by the Italian seismic code (NTC08).The study focuses on the territory encompassing Tuscany region in Central Italy and it has been carried out for six return periods, which are 50, 75, 101, 475, 712 and 949 years. The procedure involved four main steps: (1) grouping of the response spectra with similar features; (2) definition of the reference response spectrum for each group; (3) selection of spectrum-compatible accelerograms using the reference response spectrum of each group; and (4) linear scaling of the accelerograms to satisfy the compatibility requirement with respect to other response spectra of the group. The last step is implemented through an interactive, user-friendly program named SCALCONA 2.0, which provides the seismic input in agreement with the site location and return period specified by the user. The program is freely available at the following web site: http://www.rete.toscana.it/sett/pta/sismica/01informazione/banchedati/input_sismici/progettazione/index.htm.     

Two types of CO2− radicals threaten the fundamentals of ESR dating of tooth enamel

In ESR dating of tooth enamel, dose values are usually obtained from powdered samples. It has been shown that the qualitative response of enamel powder to environmental and laboratory dosing is closely similar, thus apparently validating ESR protocols for dose estimation. When working on human fossils, their cultural and scientific value prevents the powdering of any samples. Measurements are carried out on enamel fragments instead. In fragments, natural and laboratory irradiations cause significantly different ESR responses. These can be attributed to two distinct CO₂⁻ radicals, one with apparently axial symmetry (orientated) and one that has no preferential orientation (non-orientated). The spectra of the naturally irradiated samples investigated here show a mix of about 90% of the orientated and about 10% of the non-orientated CO₂⁻ radicals. In contrast, laboratory irradiation induces a mix of about 60% orientated and 40% non-orientated CO₂⁻ radicals. Heating experiments show that the non-orientated CO₂⁻ radicals are significantly less stable than the orientated. This fact on its own would have serious implications for dose estimations, implying massive underestimations. It turns out, however, that with the heating induced decline of the non-orientated CO₂⁻ radicals, a larger number of orientated CO₂⁻ radicals is created. It is presently unclear whether these two processes are directly connected. In spite of very large internal reorganisations during these processes, powder spectra are only little affected by heating, because the powder spectra of both CO₂⁻ radicals are closely similar.The maximum differences that are observed on powder spectra in post-irradiation heating experiments, are in the range of 3%, dose values may be affected by a similar amount. However, when using preheating steps, which would occur when applying post-irradiation heating protocols to single aliquots, the thermal behaviour of the irradiated samples is quite different. While the annihilation of the non-orientated CO₂⁻ radicals has about the same decay rate in preheated and non-preheated samples, the increase of the orientated CO₂⁻ radicals is less pronounced in the preheated samples. As a result, overall intensity changes become critically dependent on the preheating times. The observed increase in signal intensity is in contrast to long-term fading experiments that showed that the ESR intensity of irradiated samples actually decreased over 6–12 years after laboratory irradiation. In view of this complexity and the small amount of quantitative information available, it is presently not possible to recommend any pre- or post-irradiation protocols.The good news for ESR dating is that any systematic errors introduced by a different mix of orientated and non-orientated CO₂⁻ radicals in the natural and irradiation spectra seem relatively small (<5%). At present, the most reliable way for the dose estimation of fragments seems to measure the samples rotating around the three principal axes and to merge the spectra to produce a powder-equivalent spectrum and use this for the construction of the dose response curve.     

The DATA program for the calculation of ESR age estimates on tooth enamel

The supplementary ZIP file of this paper contains the DATA program, which can be used for ESR age calculations of tooth enamel. This paper outlines the use and limitations of this program.     

Orthotropic anisotropy: on contributions of elasticity parameters to a difference in quasi-P-wave-squared velocities resulted from propagation in two orthogonal symmetry planes

We investigate the dependence of quasi P-wave phase velocity propagating in orthotropic media on particular elasticity parameters. Specifically, due to mathematical facilitation, we consider the squared-velocity difference, , resulted from propagation in two mutually perpendicular symmetry planes. In the context of the effective medium theory, may be viewed as a parameter evaluating the influence of cracks – embedded in the background medium – parallel to one or both aforementioned planes. Our investigation is both theoretical and numerical. Based on Christoffel's equations, we propose two accurate approximations of . Due to them, we interpret the aforementioned squared-velocity difference as being twice more dependent on , than on . To describe the magnitude of the dependence, we consider the proportions between the partial derivatives of . Further, it occurs that is influenced by the ratio of vertically propagating quasi P-wave to vertically propagating quasi S-wave. Anomalously high might be caused by the low P/S ratio, which in turn can be an indicator of the presence of gas in natural fractures or aligned porosity. Also, we carry out numerical sensitivity study, according to which is approximately twice more dependent on than on , twice more sensitive to than to , and equally dependent on as on . The dependence on and can be neglected, especially for small phase angles. We verify the approximations and perform the sensitivity study, using eight examples of the elasticity tensors.     

ESR dating of optically bleached quartz grains from Plio-Pleistocene to Holocene coastal dune deposits (Wilderness-Knysna area,South Africa): a comparison with luminescence

Five Plio-Pleistocene to Holocene aeolian quartz samples from the coastal dune deposits of the Wilderness-Knysna area (South Africa) previously dated by OSL were selected for ESR dating. Samples were processed following the Multiple Centre approach and using the Multiple Aliquot Additive dose method. Aluminium (Al) and Titanium (Ti) signals were systematically measured in all samples.Our study shows that ESR results obtained for Middle Pleistocene to Holocene samples may be strongly impacted by (i) the presence of a significant high frequency noise in the ESR spectra acquired for the Ti signals and (ii) the choice of the fitting function employed. In particular, if not taken into account, very noisy spectra can lead to a significant overestimation of the true ESR intensity measured for the Ti–H signal. These sources of uncertainty are however not sufficient to remove the ESR age overestimations. Consequently, our results indicate that the Al and Ti ESR signals of these quartz samples have not been fully reset during their aeolian transport.While this work contributes to improve our understanding of the ESR method applied to quartz grains, and especially of the potential and limitations of the Ti signals, it also provides additional baseline data to illustrate the existing variability among quartz samples of different origins or sedimentary context. Our results are consistent with previous studies by confirming that the Ti–H signal shows the best potential for the evaluation of low dose values (<100 Gy for these samples), whereas it becomes inappropriate for the higher dose range, and the Ti–Li–H (option D sensu Duval and Guilarte, 2015) should be used instead.Beyond the methodological outcome, this ESR dating study also provides a useful addition to the existing chronology of the aeolian deposits in this region. In particular, new (and possibly) finite numerical age results were obtained for the two oldest samples, constraining the aeolianite landward barrier dune and the coversand formations to the MIS 10-8 and Pliocene, respectively.     

Incipient sediment motion based on turbulent fluctuations

The current study modifies the representation of the Shields parameter using turbulent strength,i.e.the root-mean-square(rms) fluid velocity.Experiments were done under a steady,uniform flow using eight sediment sizes with particle Reynolds numbers(Rep) ranging between 1.0(fine sediment) and 183.4(coarse sediment).Utilising the peak rms horizontal(u) values,the critical Shields parameter,θ_c,was calculated and a trend similar to the well-established Shields curve was developed.The analysis was extended to the Shields curve obtained based on the critical shear velocity,Reynolds shear stress,and data extracted fro m the oscillating grid-turbulence experiments.Results show that turbulent fluctuations are crucial for the incipient sediment motion and are essentially better predictors than the commonly used critical shear velocity.A quadrant analysis to identify the role of turbulent bursting events in incipient sediment motion also was done where sweeps and ejections are dominant for finer and coarser sediment sizes,respectively.     

Costanti armoniche e non armoniche delle Maree di Porto Lignano

Riassunto Porto Lignano si trova fra Trieste e Venezia. Il mareografo riduce nel rapporto 110 e ha uno scorrimento di 72 mm per giorno. Le costanti armoniche sono dedotte col metodo delDoodson da una serie di tre mesi. Le maree sono di tipo prevalentemente semidiurno, in vicinanza alle quadrature diventano diurne. Dalle costanti armoniche si deducono quelle non armoniche. I valori trovati si confrontano con quelli di Trieste e Venezia.

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Summary Porto Lignano is situated between Trieste and Venice. The self-reconding tide gauge have a height ratio 110 and a time scale 7,2 cm/day. The method of analysis adopted for the calculation of harmonic tidal constant is that ofDoodson applied to 3 months. The tides are generally semidiurnal, near the quadrature they becom diurnal. From the harmonic constant are deducted the nonharmonic. The determined values are compared with that of Trieste and Venice.

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Zusammenfassung Porto Lignano liegt zwischen Triest und Venedig. Der selbstregistriende Pegel reduziert im Verhältnis 110 und hat einen Ablauf von 72 mm pro Tag. Die harmonischen Konstanten wurden mit derDoodson Methode von einer dreimonatlichen Reihe berectnet. Die Tiden sind vorwiegend Halbtagsgezeiten, bei den Quadraturen werden sie Eintagstiden. Aus den harmonischen Konstanten wurden die nictharmonischen Konstanten abgeleitet. Die berechneten Werte wurden mit jenen von Triest und Venedig verglichen.

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Lavoro eseguito con il contributo del Consiglio Nazionale delle Ricerche.     

U-series,ESR and 14C studies of the fossil remains from the Mousterian levels of Zafarraya Cave (Spain): A revised chronology of Neandertal presence

Zafarraya Cave is considered a reference site for the last presence of Homo neanderthalensis presence in the south of the Iberian Peninsula. In this paper, accelerator mass spectrometry (AMS) radiocarbon dates were carried out on charcoals and faunal remains, U–Th dating using either alpha spectrometry or Thermal-Ionization Mass Spectrometry (TIMS) and ESR dating were performed on faunal remains. These analyses were carried out on samples from the Mousterian levels of the site (archaeostratigraphic units UC, UD, UE, UF, UG). The ¹⁴C AMS dates of charcoal samples (n = 11) were scattered and displayed no coherence with the stratigraphy suggesting possible alteration. The delicate charcoal and faunal samples underwent the gentle RR, ZR (ABA) or AG (ABA) pretreatment procedures at ORAU. The RR protocol is currently considered too gentle and the results are considered with caution. Four ZR charcoal pretreatments failed due to the fact that the charcoal samples were altered. Only two charcoals samples subjected to the ZR pretreatment yielded a reliable % C (>60%) (OxA-9001 and OxA-9002, 40,294–42,761 and 38,763–40,604 cal BP). Their ages are consistent with the stratigraphy and are considered to provide the best age estimate for the level bearing the Z2 Neandertal mandible (Unit UE). For the dentine and the bone samples, the ¹⁴C AMS were less dispersed. ¹⁴C analyses failed for four bone samples due to insufficient collagen content. Moreover, the %C is very low for two samples, suggesting alteration of the fossil remains at Zafarraya. Only two other samples with enough %C (>30%) were retained: OxA-8024 and OxA-8999 (Unit UE). The respective ¹⁴C ages range from ∼34 to 39 ka cal BP. The U/Th (TIMS) analyses of enamel samples displayed an extremely low uranium content (< ∼ 0.02–0.04 ppm). Moreover, the U/Th age range of faunal remains is large, thus providing no conclusive results. ESR dating was chosen for this exercise as, in combination with U-series, it can be used to assess U-uptake in open systems. The combined ESR and U/Th (TIMS) age estimates on tooth enamel yielded US-ESR ages between 33 (+3/−4) ka to 43 ± 3 ka (MIS3) for two Equus teeth and one Capra tooth in unit UE, overlapping with the oldest charcoal and bone ¹⁴C dates. The age of the Zafarraya fossil remains was derived from the US-ESR time range of 30–46 ka (MIS 3). We consider this age range to be more representative of the Neandertal occupations at the site than the hitherto widely cited uncalibrated ¹⁴C age of around 30 ka.     

Least-squares self-coherency analysis of superconducting gravimeter records in search for the Slichter triplet

We develop a new approach for the spectral analysis of the superconducting gravimeter data to search for the spheroidal oscillation ₁S₁ of the Earth solid inner core. The new method, which we call least-squares (LS) self-coherency analysis, is based on the product of the least-squares spectra of segments of the time series under consideration. The statistical foundation of this method is presented in the new least-squares product spectrum theorem that establishes rigorously confidence levels for detecting significant peaks. We apply this approach along with a number of other innovative ideas to a 6-year long gravity series collected at the Canadian Superconducting Gravimeter Installation (CSGI) in Cantley, Canada, by splitting it into 72 statistically independent monthly records. Each monthly record is analysed spectrally and all monthly LS spectra are multiplied to construct the self-coherency spectrum of the 6-year gravity series. The self-coherency spectrum is then used to detect significant peaks in the band 3-7 h at various significant levels with the aim to identify a triplet of periods associated with the rotational/ellipsoidal splitting of ₁S₁ (Slichter triplet). From all the Slichter periods predicted by various researchers so far, Smylie's triplet appears to be the most supported one, albeit very weakly, both, before and after the atmospheric pressure effect is removed from the series. Using the viscous splitting law [Smylie, D.E., 1992. The inner core translational triplet and the density near Earth's center. Science 255, 1678-1682] as guide, we can also see one interesting and statistically significant triplet with periods A = {4.261 h, 4.516 h, 4.872 h}, which changes slightly to A′ = {4.269 h, 4.516 h, 4.889 h} after the atmospheric pressure correction is applied to the gravity series.     

Die Temperaturinversion im Tiefenwasser des Südatlantischen Ozeans

Zusammenfassung Die südatlantische Temperaturinversion wurde 1873–1876 zwischen 5° N und 40° S in 1000–2400 m Tiefe von Challenger und Gazelle mittels Minimumthermometer entdeckt, wie von A. Merz 1922 dargelegt ist. Es wird gezeigt, daß die Fehlerquellen der alten Reihenmessungen in der Regel kleiner sind als das Ausmaß der Inversion und daß sich bereits die ersten Bearbeiter in der Deutung dieses Phänomens auf dem richtigen Wege befanden. Doch finden diese Ergebnisse wegen der (nur z. T. berechtigten) Skepsis gegenüber der Meßgenauigkeit der Extremthermometer keinen Eingang in die Ozeanographie. Erst 1911 wird die südatlantische Temperaturinversion von Brennecke auf Deutschland mittels exakter Kippthermometer auf der Westseite wiederentdeckt und 1925–27 von den Ozeanographen des Meteor bis zu den letzten Spuren im ganzen Ozeanraum verfolgt. Eine Darstellung dieses Phänomens bot der Verfasser bei der Bearbeitung der ozeanischen Stratosphäre im Meteor-Werk 1936. In Abb. 1 und 2 der folgenden Arbeit werden nunmehr neue Karten über die regionale Verbreitung des Inversionsausmaßes auf Grund der Reihenmessungen von Challenger-Gazelle und von Meteor vorgelegt, die in großen Zügen übereinstimmen, jedoch abweichend von Merz lehren, daß weite Gebiete der Osthälfte keine Inversion (bzw. Isothermie) aufweisen. Aus den engabständigen Meteor-Serien ergibt sich eine unerwartet enge Beziehung der Inversion zum Relief des Tiefseebodens. In ihrem Ausmaß spiegelt sich ferner die bevorzugte Tiefenzirkulation der Westseite mit ihren schwächeren Ausläufern nach Osten, wodurch die von Defant und vom Verfasser im Meteor-Werk erzielten Ergebnisse bestätigt werden. Das räumliche Bild der Inversion wird durch Karten der Temperatur und Topographie ihrer Grenzschichten ergänzt (Abb. 4 u. 5). An Wiederholungsserien des Meteor (Stat. 197 u. 241) wird gezeigt, daß sich die Tiefenlage der Inversion im Rhythmus der halbtägigen inneren Gezeitenwelle hebt und senkt und daß die Amplitude dieser vertikalen Verlagerung mit ±60 bzw. ±25 m bemerkenswert groß ist (Abb. 7 u. 8). Neben diesen kurzperiodischen Änderungen deuten gewisse Anzeichen auf langperiodische (jahreszeitliche) und unperiodische Pulsationen im Ausmaß der Inversion.

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The temperature inversion in the deep water of the South Atlantic

Summary The temperature inversion in the South Atlantic has been discovered in 1000–2400 m depth between 5° N and 40° S by means of minimum thermometers in the years 1873–1876 by the research ships Challenger and Gazelle, as A. Merz has pointed out in 1922. In the present paper it is shown that the inaccuracies of the old temperature series are usually smaller than the amount of inversion and that the first interpreters have already been on the right way in explaining this phenomenon. However these results were not acknowledged on account of general (but only partly justified) doubts in the measuring accuracy of maximum and minimum thermometers. Only in 1911 the South Atlantic temperature inversion has been rediscovered in the western part of the ocean by Brennecke on board the polar ship Deutschland by means of exact reversing therm ometers, and its extension has been pursued to its utmost ends throughout the southern and tropic Atlantic by the oceanographers of Meteor in 1925–27. In 1936 the author has discussed the phenomenon in his treatise on the oceanic stratosphere in the Meteor work. In Fig. 1 and 2 of the following paper new charts of the regional distribution of the amount of inversion are given as based on the serial observations of Challenger — Gazelle and Meteor, which on the whole agree with each other and — divergently from Merz — show that in vast regions of the eastern part of the South Atlantic there is no inversion (or isothermal layer). From the Meteor series which are arranged very close together a remarkably close relation between inversion and bottom relief is derived. Moreover in the amount of the inversion the greater intensity of deep sea circulation in the western South Atlantic with its slight extensions towards the east is recognized, another verification of the results obtained by Defant and the author in the Meteor work. The spatial representation of the inversion is completed by charts of the temperature and topography of its boundary layers (Fig. 4 and 5). By aid of repeat series of the Meteor expedition (Station 197 and 241) it is pointed out that the depth of the inversion is rising and sinking in accordance with the semi-diurnal internal tide and that the amplitude of this vertical wave, amounting to ±60 or ±25 m, is remarkably great (Fig. 7 and 8). Besides these short-period variations there is some indication that the inversion is also undergoing long-period (seasonal) and aperiodic pulsations.

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Hierzu Tafel 6 mit Abbildung 2

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Herrn Prof. Dr. Dr. h. c. Georg Tischler (Universität Kiel) zum 70. Geburtstag.     

Multi-objective fitting of concentration-discharge relationships

Concentration–discharge ($C–Q$) relationships are widely used to assess the link between hydrological and biogeochemical processes at the catchment scale. $C–Q$ relationships are mainly calibrated using mono-objective methods to represent, either concentrations or discharge-weighted concentrations (i.e., load). Based on its wide use in hydrological modelling, we test a multi-objective calibration for the $C–Q$ relationship parameters, using both concentration and load, and compare it to a mono-objective calibration applied on either concentrations or load. This work is carried out on a high-frequency dataset (ORACLE-Orgeval Observatory, France). Our findings show that the multi-objective calibration yield a better representation of $C–Q$ relationships parameters during the high and low-flow events. The multi-objective calibration can be used for all forms of $C–Q$ relationships and avoids issues of under-representation of dilution processes characterized by high-discharge, low-concentration periods.