Matthias Krbetschek

Radiometric dating of the type-site for Homo heidelbergensis at Mauer, Germany

The Mauer mandible, holotype of Homo heidelbergensis, was found in 1907 in fluvial sands deposited by the Neckar River 10 km southeast of Heidelberg, Germany. The fossil is an important key to understanding early human occupation of Europe north of the Alps. Given the associated mammal fauna and the geological context, the find layer has been placed in the early Middle Pleistocene, but confirmatory chronometric evidence has hitherto been missing. Here we show that two independent techniques, the combined electron spin resonance/U-series method used with mammal teeth and infrared radiofluorescence applied to sand grains, date the type-site of Homo heidelbergensis at Mauer to 609 ± 40 ka. This result demonstrates that the mandible is the oldest hominin fossil reported to date from central and northern Europe and raises questions concerning the phyletic relationship of Homo heidelbergensis to more ancient populations documented from southern Europe and in Africa. We address the paleoanthropological significance of the Mauer jaw in light of this dating evidence.

High-Resolution Cathodoluminescence Studies of Feldspar Minerals

Feldspars are the most important rock-forming minerals occurring in igneous, metamorphic and sedimentary rocks. Cathodoluminescence (CL) of feldspars is an important tool in interpreting genetic conditions of rock formation and alteration (Marshall 1988). Furthermore, feldspars are widely used as dosimeters in dating geological and archaeological materials by thermally or optically stimulated luminescence (TL, OSL).

The age of the Lower Paleolithic occupation at Schöningen

Thermoluminescence (TL) data are presented for eight samples of heated flint collected at the archaeological site of Schöningen 13/I-1 (Cycle I), for which a Holsteinian age is suggested by palynology of stratigraphically similar positions within a cyclic sedimentological model for the Quaternary sequence of Schöningen. Although the fire responsible for the zeroing of the TL-signal cannot be unequivocally attributed to human activities, any time difference between a natural fire and the human occupation is negligible for a site of this antiquity. The weighted mean age of 321 ± 16 ka places the last heating of the flints nominally in the age range of Marine Isotope Stages (MIS) 10 to 8. By inference this data would suggest an attribution of the Holsteinian to MIS 9 and may also serve as a maximum age estimate for the spear site of Schöningen 13/II-4 (Cycle II). Considering the chronometric data available and following an alternative sedimentological model the age of these two sites at Schöningen can be considered as belonging to the same climatic cycle. This suggests an attribution to MIS 9, and by inference provides an age estimate of 337-300 ka for the oldest spears in human history.

A fully automated multi-spectral radioluminescence reading system for geochronometry and dosimetry

Following the recent development of a new solid state luminescence dating technique for geochronometry that uses the infrared radiofluorescence (IR-RF) at 1.43 eV (865 nm) of potassium feldspars, an automated radioluminescence (RL) measurement instrument was designed and built. The instrument is based on a commercial Daybreak 1100 automated TL reader system, widely used in thermoluminescence (TL) dating. It was re-designed and highly modified to adapt it to the physical and methodological needs of the IR-RF dating technique and other RL dosimetry applications. This new system holds up to 10 samples, has an integrated bleaching and irradiation unit, and measures the radiofluorescence (RF) (excitation using 10 137 Cs sources, each 5 MBq activity) as well as phosphorescence eects. All technical requirements for the measurement of optically excited luminescence were implemented in order to investigate the defect structure of luminescent materials. Because of the broad wavelength range and the high sensitivity of the photomultiplier detector used, the system is suitable for a great many luminescent materials, natural and synthetic. This paper summarises the technical features and performance criteria of the system. Furthermore, a calibration method and the dosimetric concepts, using the blue RF emission of Al2O3:C at 415 nm for the source dose rate estimation with low calibation errors is described in detail. Finally, examples of IR-RF dating results on Quaternary sediments as well as of other RF measurements and their physical interpretation using dierent RF emissions are presented.

Infrared radiofluorescence (IR-RF) dating of middle pleistocene fluvial archives of the Heidelberg Basin (Southwest Germany)

The infrared radiofluorescence (IR-RF) dating technique was applied to eight fluvial samples that were collected from two sediment cores at the Heidelberg Basin located near Viernheim and Ludwigshafen in southwest Germany. Based on the IR-RF derived ages of the samples it was possible to establish a chronological framework for the Mid-Pleistocene fluvial deposits of the Heidelberg Basin. The results allow us to distinguish between four main periods of aggradation. The lowermost sample taken from 100 m core depth lead to an IR-RF age of 643 ± 28 ka pointing to a Cromerian period of aggradation (OIS 17–16). For the Elsterian it is now possible to distinguish between two aggradation periods, one occurring during the Lower Elsterian period (OIS 15) and a second during the Upper Elsterian period (OIS 12–11). For the so called Upper interlayer (or “Oberer Zwischenhorizont” — a layer of organic-rich and finer-grained deposits), the IR-RF results point to a deposition age of around 300 ka, with samples taken directly on top and out of this layer yielding IR-RF ages of 288 ± 19 ka and 302 ± 19 ka, respectively. Hence, the measured IR-RF ages clearly point to a deposition during the Lower Saalian period (OIS 9–8) whereas earlier studies assumed a Cromerian age for the sediments of the Upper Interlayer based on pollen records and also mollusc fauna. The new IR-RF dataset indicates that significant hiatuses are present within the fluvial sediment successions. In particular the Eemian and Upper Saalian deposits are missing in this part of the northern Upper Rhine Graben, as the 300 ka deposits are directly overlain by Weichselian fluvial sediments. It is obvious that time periods of increased fluvial aggradation were interrupted by time periods of almost no aggradation or erosion which should have been mainly triggered by phases of increased and decreased subsidence of the Heidelberg Basin.

DATING ARCHAEOMETALLURGICAL SLAGS USING THERMOLUMINESCENCE

Thermoluminescence has a great potential for dating archaeometallurgical slags, because the smelting process leads to a well-defined resetting of the ‘luminescence clock’. However, the complex compositions of slags have unpleasant consequences for TL measurements if the bulk slag substance is used. To overcome this problem, quartz has been separated out of slag matrices by chemical and physical procedures. The TL measurements were carried out on this defined mineral phase. This method was tested with seven slag samples from different locations and ages. In most cases, the TL ages determined show good agreement with reference data.

Spectral investigation of the thermoluminescence of heated flint (silex)

Abstract Test measurements to determine the sufficient heating of silex (flint) artifacts from prehistoric sites for TL dating revealed a large variation of TL-characteristics. To determine TL-emission wavelengths suitable for dating, the spectra of several samples from different geological origin were measured. A dominant emission in the orange band was found, consisting of three peaks centred around 90–130°C, 190 and 270°C or only a broad single peak at around 250°C. Two UV peaks appear at 100–190°C and around 360°C. At the latter temperature a blue emission occurs as well. Simulation experiments of prehistoric fires for various temperatures were performed. In contrast to the blue emission the UV emission around 360°C shows slight fading and/or bleaching. The blue band also requires slightly lower temperatures for complete resetting than the UV–TL. Furthermore, this blue-TL emission is less light sensitive, especially for red laboratory light, making sample preparation much more convenient. Sufficiently heated silex samples can easily be detected by the position of the high temperature TL-peak at about 360°C and a Gaussian-like shape of the blue peak, and of course by the plateau test. The observed TL-variation of heated archaeological silex might be due to the different genesis of the material, but it can also be attributed to different degrees of ancient heating.

Feldspar flotation as a quartz-purification method in cosmogenic nuclide dating: A case study of fluvial sediments from the Pamir

Graphical abstract

Gamma-Irradiation Dependency of EPR and TL-Spectra of Quartz

Paramagnetic defects formed during experimental γ-irradiation with various dose (70 to 1.5 × 107 Gy, 60Co) in well documented polycrystalline quartz samples from tin-tungsten ore veins, gneiss and granite were investigated by X-band continuous-wave electron paramagnetic resonance spectroscopy at temperatures from 20–295 K. On the same samples spectrally resolved thermoluminescence measurements were carried out (temperature range 50–350 °C, heating rate 2 K/s; wavelength region 200–800 nm) to examine the relationships between the radiation dose, the EPR signal intensity and the thermoluminescence spectra to link the EPR-spectra to the centres responsible for the thermoluminescence peaks in natural quartz. The present study concerns mainly the analysis of the paramagnetic centres [AlO4]0 and [TiO4−/Li+]0. The investigation of the relationship between the EPR intensity of paramagnetic centres and the γ-irradiation dose shows an increase of the EPR intensity with values related to the impurity content. Different centres reveal different saturation behaviour but independent from concentration. The [AlO4]0 centres show saturation at about 1 × 106 Gy and the [TiO4−/Li+]0 centres already after irradiation with 5 × 103 Gy with radiogenic annealing at higher irradiation dose. From the irradiation behaviour the [TiO4−/Li+]0 centre is suggested as electron traps for the TL peaks at 150–200 °C/330–340 nm, 200 °C/510 nm and 280 °C/470–510 nm, whereas oxygen-vacancy-centres for the first peak and the [AlO4]0-centres for the other peaks are working as recombination sites.

A luminescence study for dating archaeometallurgical slagspaper

Abstract A reliable direct dating method for archaeometallurgic slag has not yet been achieved. Nevertheless, in archaeological and environmental research information about the age of slag deposits is urgently needed. Metallurgical slag consists of many components. Artificial secondary minerals, for example fayalit, olivine and glass phases are the dominant parts. In many cases primary minerals, called relicts, are also components of slag. Quartz, baryte and fluorite are examples. Such a complex composition leads to large difficulties in paleodose determination if the bulk slag substance is used. On the other hand, slag has a complicated microdosimetry caused by great differences between the individual mineral phases and the possibility of inhomogeneous radionuclide distribution. To overcome these problems in luminescence dating defined phases of the slag have been separated by special chemical and physical procedures. Quartz and glass fractions were investigated by thermoluminescence (TL) and radioluminescence (RL)-spectrometry. Alpha-autoradiography using Kodak LR-115 foil was carried out to get information about the distribution of radionuclides.