ESR dose response of Al center measured in quartz samples from the Yellow River (China): Implications for the dating of Upper Pleistocene sediment

The ESR dating method requires to describe the evolution of the ESR signal intensities vs. increasing gamma doses, then to extrapolate the equivalent dose of radiation received by the sample since its deposition using mathematical fitting. The function classically used to describe the growth curves of ESR aluminium signal in quartz was recently discussed and challenged for Lower Pleistocene sediments. In the present work, some alluvial sediments sampled in Upper Pleistocene fluvial terraces of the Yellow River system (China) permit us to test the application of another extrapolation function (linear + exponential) recently proposed for Lower Pleistocene sediments. The equivalent doses obtained here for the recent deposits of the Yellow River system and the corresponding ages are promising and indicate the potential of ESR to date quartz deposits from Upper Pleistocene times.     

A combined visual-geochemical approach to establishing provenance for pegmatite quartz artifacts

A technique for establishing source provenance for pegmatite quartz artifacts was developed using a quarry sample from the Churchill River basin of northern Manitoba and Saskatchewan. Secondary ion mass spectrometry (SIMS) was used to quantify Ti, Ge, Th, and U trace element concentrations and Pb isotope ratios, coupled with qualitative visual characteristics to distinguish between pegmatite quartz from different archaeologically exploited sources in the Churchill River basin region. The technique was also applied to a small sample of quartz artifacts recovered from sites in and around the study area in a preliminary attempt to assign or rule out raw material provenance to characterized sources.     

Changes in natural OSL sensitivity during single aliquot regeneration procedure and their implications for equivalent dose determination

Measurement of low temperature (90°C–120°C) Thermoluminescence (TL) sensitivity of natural quartz samples subjected to pre-heating and optical stimulation indicate that significant sensitivity changes can occur during measurement of the natural Optically Stimulated Luminescence (OSL). During the measurement of natural signal, the luminescence sensitivity of samples can change by 40%. The sensitivity changes both during the initial preheat and the measurement of natural OSL. The currently used version of Single Aliquot Regeneration (SAR) protocol measures and corrects for the sensitivity changes after preheat and readout of natural OSL. However, it does not take into account the changes in sensitivity during the readout of the natural signal. We therefore developed a correction procedure so that both the natural and the regenerated OSL intensities can be measured and plotted with the same sensitivity and suggest that in the absence of such a correction, a considerable fraction of the SAR based ages could have systematic errors. The correction for the sensitivity is based on the use of sensitivity of 110°C TL quartz peak, which is correlated to OSL signal (Murray and Roberts, 1998). The use of 110°C peak provides a reasonable measure of the changes in OSL sensitivity of quartz. A modified Natural Sensitivity Corrected-SAR (NSC-SAR) procedure, that comprises the measurement of, 1) the TL intensity of 110°C peak for a test dose on sample as received (i.e. natural sample) and, 2) the sensitivity of the 110°C peak of the same sample after the preheat and read out of the natural OSL, is proposed. This ratio, termed as Natural Correction Factor (NCF), then provides a way to correct for sensitivity changes. Results on samples from diverse depositional environments indicated that the NSC-SAR consistently (without exception) provided improved distribution in paleodoses i.e. a lower scatter compared to the standard SAR protocol. In addition, the use of this protocol also resolved anomalous cases where the intensity of natural OSL was significantly above the saturation intensity of the regenerated OSL. Implicitly, this study implies a caution on the use of palaeodoses obtained from single grains as such a correction is not possible in the currently used automated single grain OSL measurement systems. The only way now on will be to analyze aliquots with only a grain on them.     

Comparison of three K-feldspar luminescence dating methods for Holocene samples

The luminescence dating of the K-feldspar fraction is an alternative way for samples that cannot yield reasonable equivalent dose (D_e) from quartz fraction with very weak luminescence signal. For testing the reliability of the infrared stimulated luminescence (IRSL) dating of K-feldspar, luminescence dating was applied to quartz and K-feldspar fractions respectively for several Holocene samples in this study. K-feldspar apparent ages using routine single aliquot regenerative-dose (SAR) protocol, K-feldspar ages using g value correction method and ages from isochron dating method were compared with quartz ages. It is found that the g value correction method cannot give reliable ages due to the large errors induced during measurements. The isochron dating method is effective to the sample with problematically external dose rate. However, isochron dating may introduce a relatively greater error during grain sizes — D_e curve fitting, therefore this method could obtain low-resolution ages for Holocene samples. Even K-feldspar apparent age from routine SAR protocol is relatively younger by about 10% than the quartz age, it still could establish reasonable chronological framework for Holocene samples.     

Re-examining the Egyptian colonial encounter in Nubia through a compositional,mineralogical, and textural comparison of ceramics

Textural, mineralogical, and X-Ray fluorescence (XRF) analyses are used as a cost effective method to distinguish for the first time ancient Egyptian and Nubian-style ceramics found in Nubia. Textural and mineralogical data suggest that Nubian-style sherds are mixtures of sand, silt, and clay sediment that is generally finer grained and poorer in quartz than is the sediment mixture used to produce Egyptian-style pottery. Chemical data also establish a significant difference in the amount of chemical variation found within each style population, but nonetheless supports a considerable overlap in the possible provenance of both styles. Observations and data obtained during this study indicate that standardized, Egyptian-style manufacturing was introduced into Nubia under colonialism, without substantially altering the diversity of native methods of production.     

COMPOSITIONAL INHOMOGENEITY OF SEDIMENTS AND ITS POTENTIAL EFFECTS ON DOSE RATE ESTIMATION FOR ELECTRON SPIN RESONANCE DATING OF TOOTH ENAMEL

We present results of particle size and radioactivity analyses of sediment samples collected from five sites with different burial environments. The uranium, thorium and potassium concentrations in the five sample sets are shown to vary with particle size. The potential effects of the observed size-dependent variations on electron spin resonance (ESR) dating of tooth enamel are assessed using two hypothetical models. Our results show that any bias to relatively fine fractions could result in a significant overestimation of the total environmental dose rate, leading to an underestimation of the calculated ESR age.     

TOWARDS A QUANTITATIVE PETROGRAPHIC DATABASE OF KHMER STONE MATERIALS—KOH KER STYLE SCULPTURE

A comprehensive quantitative petrographic database of sandstones used by the Khmers for sculptural purposes would be a helpful tool for archaeologists, museum curators and others interested in pursuing research on early stone usage, geological source and provenance. Towards that end, this paper presents quantitative petrographic analysis of stone materials used in the production of some free‐standing sculptures and architectural elements in the Koh Ker style of the 10th century from the collections of the National Museum of Cambodia and The Metropolitan Museum of Art. These materials are compared to samples from the quarry of Thmâ Anlong near the foothills of the Phnom Kulen, Sieam Reap province. Primary and secondary detrital modes and key grain‐size parameters are used to identify three sandstone types. The free‐standing sculptures are carved from feldspathic arenite and feldspato‐lithic to litho‐feldspathic arenite. Finely carved lintels are worked from a quartz arenite, which is significantly richer in quartz grains and of a finer grain size. The geological source of the two other lithotypes will have to await detailed geological survey of the Koh Ker area accompanied by petrographic study of selected samples from documented quarries. The significance and potentiality of quantitative petrographic study of Khmer stone materials are shown in supporting and integrating archaeological investigations in South‐East Asia.     

Archeometric characterization of prehistoric grindstones from Milazzo Bronze Age settlement (Sicily,Italy)

The results of a petrographic and geochemical study carried out on archeological grindstones allow to provide new constraints on protohistoric commercial exchanges over the Mediterranean area. Eleven grindstones, discovered in an archeological site located in Milazzo (Messina, Sicily) and dated from the Early Bronze Age, have been investigated by geochemical and petrographic techniques. The raw materials are mainly volcanic rocks characterized by calc-alkaline and K-alkaline affinities with volcanic arc geochemical signature. Only one sample, made of basalt belonging to the Na-alkaline series, shows an intraplate signature. The comparison with the available literature data for similar rocks allowed constraining the volcanic origin of the exploited lavas. While the intraplate-type raw material came from Mt. Etna Volcano (Sicily), the arc-type volcanic rocks are mostly trachyandesites, basaltic andesites, and one rhyolite. Although most of them come from the Aeolian Arc, a provenance of some samples from the Aegean Arc cannot be excluded. This last region could represent the most probable provenance area for the rhyolite sample.     

Quartz recrystallization and fluid flow during contact metamorphism: a cathodoluminescence study

Cathodoluminescence (CL) images of quartz grains in the Appin Quartzite from the aureole of the Ballachulish Igneous Complex (Scotland) reveal a textural complexity that we interpret in the light of published models of the evolution of the contact aureole. Five distinct generations of quartz can be discriminated in CL. The oldest of these is a dark luminescing mottled quartz (Type 1 quartz) that occurs in the centres of pre‐existing grains, in samples collected from 210 m to 0.1 m from the contact. Dark mottled quartz is interpreted to be unrecrystallized material and has a regional metamorphic CL spectral signature. The onset of contact metamorphism resulted in grain growth visible in CL as a series of fine‐scale alternating bands of bright and dark luminescing material (Type 2 quartz), which we attribute to infiltration of repeated pulses of small amounts of H₂O along grain boundaries. Close to the intrusion, a subgrain‐scale network of intragranular, bright luminescing features could have resulted from either intragranular microcrack‐controlled infiltration of H₂O at high temperatures or intergranular cracking followed by grain growth (Type 3 quartz). Broad bands of bright material on grain boundaries in samples that are inferred to have undergone partial melting are interpreted as quartz crystallized from the melt phase (Type 4 quartz). The final stage in the textural development is marked by a series of aligned fractures, detected in CL by nonluminescing material (Type 5 quartz) and corresponding closely with trails of fluid inclusions. These fractures are interpreted as the pathways for late‐stage, low‐temperature, retrogressive fluids.     

A Study on Black‐Body Celadon Excavated in The Altar Guan and Literature Ge (Longquan Ge) Kilns by EDXRF

Samples of celadon were collected from the Altar Guan Kiln in Hangzhou, and from the Xiaomeizhen and Xikou Kilns, two subordinate kilns of the Longquan Kiln producing black‐body celadon called Literature Ge. Both the elemental contents in the sample bodies and the glaze were measured. The results reveal that the sample bodies contain fingerprint information for provenance, while this was lost in the glaze during the production process. The TiO₂, MnO and Rb₂O contained in the bodies are fingerprints to distinguish between celadons from the Xiaomeizhen and Xikou Kilns. In the Altar Guan Kiln, some low‐TiO₂ samples were found and their body colour is much lighter than some others, but they do not differ with regard to iron content. This indicates that both titanium and iron are indispensable for the blackness of the bodies: they may react to form some black minerals during the firing process. Ultimately, samples from the Literature Ge and Altar Guan Kilns differ in their body constituents. Principal component analysis reveals that the samples can be divided into two groups, corresponding to the two different areas.     

Luminescence characteristics and dose distributions for quartz and feldspar grains from Mumba rockshelter,Tanzania

Mumba rockshelter is a key archaeological site for the Middle and Later Stone Age occupation of East Africa, but its chronology has remained unresolved. We report the results of a dating study, focussing on the characterisation of the optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) properties of quartz- and potassium-rich feldspar grains. Quartz has previously proven troublesome for dating in East Africa. We identified five general types of quartz grain behaviour, based on the shapes of their OSL decay and dose–response curves. Dose recovery experiments and measurement of the natural samples revealed particular problems with quartz grains that had hyperbolic dose–response curves, low characteristic saturation doses and anomalously large changes in sensitivity between regenerative-dose cycles. The use of pulsed irradiation during measurement and standard and additional quality-assurance criteria during data analysis reduced the number of grains that suffered from these problems. We applied these procedures to individual grains of quartz from eight samples and, using appropriate statistical models, identified post-depositional mixing in three samples. The remaining samples had scattered equivalent-dose distributions typical of quartz grains that had received variable beta dose rates during burial. Stratigraphically consistent OSL ages were obtained for all but the deepest sample. Feldspar ages were estimated for the latter sample and three other samples, using the elevated temperature IRSL signal that exhibited low rates of anomalous fading. Fading-corrected feldspar ages for the latter three samples are consistent with their single-grain quartz ages, but single-grain dating is needed to address problems of post-depositional mixing.     

Multi-method luminescence investigations on quartz grains of different sizes extracted from a loess section in Southeast Romania interbedding the Campanian Ignimbrite ash layer

In this study we present luminescence investigations of four samples of loess bracketing the Campanian Ignimbrite/Y5 tephra at the Rasova-Valea cu Pietre site, on the eastern bank of the Danube River, southeastern Romania. Investigations involved SAR-OSL dating on aliquots of fine (4–11 μm) and medium-grained (63–90 μm) quartz, as well as single grain analyses on 125–180 μm quartz. Luminescence dating results coupled with glass-shard chemical fingerprinting assign the depositional age and origin of the ash layer to that of the Campanian Ignimbrite/Y5 tephra, dated elsewhere using ⁴⁰Ar/³⁹Ar to 39.28 ± 0.11 ka. Fine-grained (4–11 μm) quartz SAR-OSL analyses yielded ages of 44.4 ± 4.5 ka below the ash, and 41.4 ± 4.2 ka above the ash layer. Single grain analysis on coarse-grained quartz, however, demonstrates that coarse material from these samples exhibits low sensitivity and responds poorly to internal checks of the SAR protocol in comparison with the finer sediment. This observation highlights the need for more extensive investigations into the luminescence properties of quartz as well as into the origin of quartz contributions from different primary sources in the Lower Danube loess steppe.     

PROVENANCING AND ARCHAEOLOGY OF ROMAN MILLSTONES FROM SARDINIA (ITALY)

Summary. Sardinia was an important Roman settlement and trade centre between 238 BC–500 AD and is an ideal site for study of Roman trade. Study of Roman millstones in Sardinia shows that the commonest type is the Pompeian (hour-glass) mill (forty-eight stones studied), with smaller numbers of cylindrical hand querns (sixteen stones studied). Most of these millstones are composed of igneous rocks which include grey vesicular lavas of basic/intermediate composition and a distinctive reddish rhyolitic ignimbrite. There is historical and archaeological evidence for millstone manufacture at six localities in Sardinia. Visual and petrographic study and X-ray fluorescence analysis for major and trace elements of seventeen millstone samples, and fifty rock samples from potential source areas have been used to provenance the igneous rock millstones. The grey vesicular lava millstones have varied sources within the Tertiary-Recent volcanic rocks of Sardinia, while the millstones composed of rhyolitic ignimbrite are from a single source of Tertiary ignimbrite at Mulargia (central west Sardinia). A single hand mill from the north of Sardinia was imported probably from Agde in southern France, and is the only sample composed of non-local rock. Mulargia millstones were widely traded within the western Mediterranean and show a rapid decrease in frequency of occurrence with increasing distance from the source. Sardinia was therefore an important centre of Roman millstone production and a source of millstone trade during the period of Roman settlement.     

Examining quartz OSL age underestimation for loess samples from Luochuan in the Chinese Loess Plateau

When using quartz OSL to date loess samples from the Chinese Loess Plateau, it has been reported that the agreement between OSL ages and the independent ages is limited to the samples younger than ～70 ka with a corresponding D_e of ～230 Gy, and a sample with an expected age of 780 ka was dated to 107 ka, corresponding to 403 Gy. The growth curves of these samples do not saturate at doses of 700 Gy, and a linear growth part was observed for doses higher than 200 Gy. However, the maximum measured age of ～100 ka imply that the D_e determined using this linear part of a growth curve could be problematic, or that the quartz OSL signal is not as stable as previously thought and has a barrier age of ～100 ka. In the current study, we examine the reasons for the age underestimation. We examined the shape of growth curves, anomalous fading, thermal stability, etc. The results show that, for the loess samples examined, quartz OSL does not fade anomalously, and the barrier age of ～100 ka is due to the fact that the OSL signals are less thermally stable, the lifetime of 0.311 Ma at 20°C obtained is much smaller than those for quartz samples from other regions such as Australia (～100 Ma).     

Performance of different luminescence approaches for the dating of known-age glaciofluvial deposits from northern Switzerland

Luminescence properties of two samples taken from sand lenses in proglacial outwash de-posits of a piedmont glacier that reached the Swiss midlands during the Last Glacial Maximum are investigated in detail. Deconvolution of CW-OSL decay curves shows that the fast component dominates the OSL signal of quartz. The chemistry of single feldspar grains, in particular the K content in different grains, is determined using wavelength dispersive spectrometry (electron microprobe), revealing an average 12.9 wt.% K of the grains contributing to the IRSL signal. D _e distributions are investigated in order to gain insights into partial bleaching, and agreement is found for quartz OSL and feldspar IR₅₀ and pIRIR₂₂₅ ages for small aliquots and single grains when applying the Minimum Age Model. These ages are also consistent with independent age control. For one sample, ages determined using the Central Age Model result in highly overestimated ages for both feldspar and quartz.     

ESR dating of the Donggutuo Palaeolithic site in the Nihewan Basin, northern China

The fluvio-lacustrine sequences in the Nihewan Basin, northern China, provide important terrestrial archives about Palaeolithic settlements and, therefore, about early human occupation in high northern latitude in East Asia. Here we present detailed ESR dating of the Donggutuo Palaeolithic site, located in this basin. Four levels A, B, C and E of the Donggutuo archaeological layer yield ESR ages ranging from 1060±129 ka to 1171±132 ka with a mean of 1119±132 ka. The ages are consistent with the paleomagnetic data, which show that the Donggutuo Palaeolithic site lies just below the onset of the Jaramillo normal subchron (0.99–1.07 Ma). Furthermore, our results indicate that the reliable ESR dating range of bleached quartz using Ti-Li centre can be effectively extended to 1100 ka and the Ti-Li centre was zeroed before the last deposition, which requires improvement of the understanding of the bleaching mechanism conditions.     

Equivalent dose distributions from single grains of quartz at Sibudu,South Africa: context,causes and consequences for optical dating of archaeological deposits

Optical ages for 14 sediment samples collected from the post-Howiesons Poort, late Middle Stone Age (MSA) and final MSA deposits at Sibudu, KwaZulu-Natal, South Africa were reported in a companion paper (Jacobs, Z., Wintle, A.G., Duller, G.A.T., Roberts, R.G., Wadley, L. New ages for the post-Howiesons Poort, late and final Middle Stone Age at Sibudu, South Africa. Journal of Archaeological Science, 2008). These ages were based on equivalent dose (D_e) distributions that were overdispersed. In this paper, we investigate factors both internal and external to the grains that may contribute to such higher than expected overdispersion in single grain D_e values. Intrinsic factors accounted for some, but not all, of the observed scatter, and application of a set of rejection criteria filtered grains for which erroneous D_e values would otherwise be calculated. We investigated sediment mixing and differences in the beta dose received by individual grains in their burial environment as two likely reasons for the observed overdispersion. The scatter in D_e distributions for all the samples is best explained by grains that were deposited at the same time and which were well bleached, but that subsequently received a range of beta doses. A procedure is presented for adjusting the measured beta dose rate, and its associated error. We show that using a combination of single grain OSL measurements of D_e, the finite mixture model and adjustment of the beta dose rate, result in stratigraphically consistent ages. These ages are more consistent than the ages obtained from multiple grain aliquot D_e values and the average dose rates for each sample; the multiple grain ages are about 10% older, partly because of the variable dose rate and partly because these aliquots contained grains with undesirable OSL characteristics.     

Unglazed pottery from the masjed-i jom’e of Isfahan (Iran): technology and provenance

The masjed-i jom’e of Isfahan is one of the earliest mosques of Iran. Since 1970, Italian researchers performed an extensive archaeological investigation uncovering huge amounts of finds. This study aims at investigating the technological features and provenance of the unglazed pottery finds by using a minero-petrographic approach. Twenty-three samples of storage, table and cooking wares were selected based on the recurrence of typologically identifiable fragments and fabrics. Two bricks, seven production indicators (spacers, kiln furniture, slags) and a local clay were analysed for comparison. The production indicators and most of the pottery show high-CaO concentration. Thick-walled wares contain coarse sedimentary/metamorphic inclusions. Samples with thinner walls contain similar but fine/well-sorted inclusions. The mineralogy and microstructure indicate firing temperatures mainly ranging from 850 to 1000 °C. Low-CaO samples contain coarse sedimentary inclusions; in one sample, volcanic lithics are present. Firing temperatures range from about 800 to 950 °C, and the low-CaO character can be related to their specific function for cooking foods. One sample, found in older stratigraphic levels, differs for its peculiar calcitic temper and lower firing temperature. Local production of most samples was constrained by the composition of the inclusions compatible with the sediments of the Isfahan area. High-CaO pottery shows compositional affinity with production indicators, local clay and tiles produced in Isfahan during the Safavid period. Cooking ware usually contains local temper, with the exception of a sample with volcanic inclusions, for which a non-local provenance is supposed. No appropriate information is, however, available regarding the low-CaO clays used in the area.     

SEM-EDS characterization of western Mediterranean obsidians and the Neolithic site of A Fuata (Corsica)

During the Neolithic, obsidians of the Monte Arci (Sardinia) volcanic complex were by far more used in the northern Tyrrhenian area than those of the three other source-islands (Lipari, Palmarola, Pantelleria) in the western Mediterranean. It is shown that merely determinations of content for six major elements with a scanning electron microscope by energy dispersion spectrometry (SEM-EDS) are sufficient to distinguish the four types of Monte Arci obsidians. Because of the compositional similarities between these obsidian types, a multivariate analysis is recommended in provenance studies. Although SEM-EDS, electron microprobe-wavelength dispersion spectrometry (EMP-WDS) and particle induced X-ray emission (PIXE) give essentially concordant results in the determination of these six element contents, subtle technique-related biases prevent the combination of SEM-EDS, EMP-WDS and PIXE data on source samples for provenance purposes. An SEM-EDS test-study reveals the first occurrence of obsidians of Lipari for the A Fuata Middle to Late Neolithic site of NW Corsica (north of Sardinia), in addition to the usual Monte Arci obsidians. Similar to EMP-WDS, the SEM-EDS technique requires only millimeter-sized fragments.     

End‐Member Mixing Analysis (EMMA) Applied to Sediment Grain Size Distributions to Characterize Formational Processes of the Main Excavation Block,Unit 2, of the Rimrock Draw Rockshelter (35HA3855), Harney Basin,Eastern Oregon (USA)

End‐member mixing analysis (EMMA) was conducted on the grain size distributions (GSD) of 13 sediment samples collected from the main excavation block, Unit 2, of the Rimrock Draw Rockshelter, a deeply stratified, multi‐component Palaeoindian rockshelter in the Harney Basin of eastern Oregon, USA. EMMA confirmed the three stratigraphic units (SU) observed in the field and identified three sedimentary end‐members (EM) that account for 95.52% of Unit 2 site formation. EM 1 comprises 70.72% of the total measured grain‐size variation and represents fluvial deposition, correlating with the bottom stratigraphic unit, SU 3. EM 2 comprises an additional 17.74% of the total measured grain‐size variation and represents fluvially reworked aeolian deposition, correlating with the upper stratigraphic unit, SU 1. EM 3 comprises the remaining 7.06% of the total measured grain‐size variation and represents possibly a two‐component aeolian deposition of suspension and short‐term saltation, correlating with the middle unit, SU 2. The results presented demonstrate the ability of EMMA as a technique to (1) unbiasedly distinguish between the SUs identified in the field using only the measured grain size distributions, (2) provide genetically meaningful and quantitative grain‐size end‐members to identify multiple major depositional processes of site formation, and (3) provide a geologically meaningful interpretation of site formation that is capable of facilitating the formulation of more focused hypotheses regarding human and environment interactions at the site.