Optical dating and sedimentary record from the terrace depositional profile of the Warta River (Central Poland)

Results of OSL dating and sedimentary studies from the profile of the low alluvial terrace of the middle Warta River are presented. The samples were dated using the single-aliquot regenera-tive method. Dating was used to establish a timing of the Weichselian Late Glacial events in the river valley environment. Stable conditions on the floodplain are expressed by the deposition of organic-rich series radiocarbon dated at 12 900-12 600 cal BP and 11 600-10 770 cal BP. Samples for OSL dating were collected from the mineral material deposited during the intensification of flood events during the Weichselian decline. The results obtained for the alluvia range from 12.78 ± 0.62 ka b2k to 14.33 ± 0.74 ka b2k. Sedimentological criteria allowed to distinguish between particular flood events. Overestimation of OSL ages is probably a result of rapidity of environmental changes in that time.     

Mississippian monumentality in the Yazoo Basin: recent investigations at the Carson site (22CO505), northwestern Mississippi

Investigations at the Carson site (22CO505), located in Coahoma County, Mississippi, have uncovered data on the development of a large Mississippian mound center dating to the period from A.D. 1200 through European contact. Recent sediment coring, excavation, artifact analyses, and radiocarbon and optically stimulated luminescence (OSL) dating shed light on earthworks and household structures at Carson, and on Mississippian culture in the Yazoo Basin more generally. Sediment coring demonstrates a laterally transgressing Mississippi River system deposited coarse sandy ridges and clay-filled swales underneath a surface horizon comprised of variously coarse to medium-fine sediment originating from generalized overbank flooding. In some instances, flood-borne sediments were found on mound flanks, indicating that at times river-based flooding may have interrupted mound construction. Sediment coring and trench excavation also demonstrate that Carson’s Mound D was built in four stages, with Stages II and III comprising the major stages of earth moving. Excavations on the mound summit reveal evidence of several superimposed structures that were burned in place and likely used for the production of stone, shell, and wooden craft items, perhaps related to Mississippi Ideational Interaction Sphere (MIIS) paraphernalia. Here we describe recent investigations at Carson and present preliminary findings; forthcoming publications will emphasize strategies of power, monumentality, craft production, and Mississippian exchange systems.     

Roman mining on Exmoor: a geomorphological approach at Anstey's Combe,Dulverton

Abstract

A survey of valley fills in south-facing combes (headwater valleys) along the south side of the Exmoor massif revealed an anomalously deep infill in one valley. This infill of up to 5 m depth had been gullied revealing a complex stratigraphy. Studies of the stratigraphy, clast orientation and shape suggested several accumulation episodes under different environmental conditions commencing in a periglacial climatic regime. Later units included sandy silts which can be dated using optically stimulated luminescence (OSL) of quartz grains. The OSL dates, indicate that the inter-gravel silts accumulated in two periods, the Romano-British period and the 16th–17th centuries AD. A survey of the very small valley catchment revealed a linear trench of a type associated with early iron mining. Given the anomalously high volume of accumulated sediment from such a small catchment and evidence of mining on the slope above the site, the geomorphic mechanism is almost certainly the downslope transport of mining debris from the slope to the valley floor. This study suggests that the systematic survey of headwater valleys in metalliferous uplands may be one way of locating areas of early mining activity and that such deposits could provide a chronology of working and abandonment.     

NEW CHRONOLOGICAL EVIDENCE FOR THE MIDDLE TO UPPER PALAEOLITHIC TRANSITION IN THE CZECH REPUBLIC AND SLOVAKIA: NEW OPTICALLY STIMULATED LUMINESCENCE DATING RESULTS

We report new optically stimulated luminescence (OSL) dates from the Central European sites of K?lna, Stránská skála, Bohunice, Vedrovice V, Vedrovice Ia, Moravský Krumlov IV and Dzeravá skala, which date to the Middle–Upper Palaeolithic transition period. There are important unresolved questions surrounding the timing of archaeological events during this crucial period in European prehistory. Archaeological layers from this time period are at the limits of the ¹⁴C method and most of these sites lack good chronology. The results of this dating project suggest that some parts of the current chronological framework may need to be revised. Although in many cases our OSL results are broadly consistent with previous dates obtained by ¹⁴C, in other cases they reveal unexpected surprises. One OSL result from K?lna opens up the possibility that Neanderthals may have survived in this part of Europe past the 30 ka bp mark as has been argued for several Neanderthal sites in southern Europe. The large Szeletian assemblage recovered from Vedrovice V may be significantly older than previously thought, which undermines the idea that the Szeletian culture is exclusively an Early Upper Palaeolithic industry. More dating research is needed to confirm the more controversial results of this research.     

Still Bay and serrated points from Umhlatuzana Rock Shelter,Kwazulu-Natal,South Africa

Umhlatuzana Rock Shelter is a long-sequence Middle and Later Stone Age site in KwaZulu-Natal, South Africa. Jonathan Kaplan excavated the site and analysed the material in the 1980s as a rescue project. For many years thereafter the collection remained untouched, partly because of doubts raised about the stratigraphic integrity of the site. Using single-grain OSL dating we show that post-depositional mixing of sediment was restricted to time-specific, small-scale events. The OSL ages obtained for the Howiesons Poort and pre-Howiesons Poort are comparable to those of other southern African sites with unambiguous Howiesons Poort and Still Bay Industries. Based on morphological and other characteristics, we reason that the Still Bay is represented at Umhlatuzana, and announce the presence of a serrated point assemblage closely associated in time with the Still Bay points.     

An improved OSL chronology for the Still Bay layers at Blombos Cave,South Africa: further tests of single-grain dating procedures and a re-evaluation of the timing of the Still Bay industry across southern Africa

This paper presents a series of new single-grain optically stimulated luminescence (OSL) ages for the Still Bay at Blombos Cave, South Africa, and compares them to previously published OSL, thermoluminescence (TL) and electron-spin resonance (ESR) ages for this site. Details are provided about the measurement and analytical procedures, including a discussion of the characteristics of the OSL signals of individual quartz grains. This forms the basis for further investigations into the sensitivity of the equivalent dose (D_e) estimates to a range of different analytical approaches, including changes in the size of the test dose, the choice of signal integration interval, the subtraction of an appropriate background, and isolation of the most light-sensitive (‘fast’) component of quartz OSL. We also report the results of an inter-operator test of D_e determination using seven new samples from Blombos Cave, and demonstrate the reproducibility of results obtained for two samples that had been dated previously at another laboratory and were measured and analysed again in this study. Together, these tests validate the robustness of the Blombos Cave single-grain OSL age estimates to a variety of alternative OSL dating procedures. We have incorporated, for the first time, these ages for Blombos Cave into a data set of all single-grain OSL ages for Still Bay and Howieson's Poort sites across southern Africa, and have used a statistical model to re-evaluate the timing and duration of the Still Bay industry. We calculate the most plausible start and end dates of the Still Bay as 72.2 ka and 71.3 ka, respectively – amounting to a duration of 0.9 ka – and estimate (with conventional 95% confidence) that this industry began no earlier than 75.5 ka, ended no later than 67.8 ka and lasted no longer than 6.6 ka.     

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).     

The use of OSL dating in unstructured sands: the archaeology and chronology of the Hutton Sands at Canteen Kopje (Northern Cape Province, South Africa)

Archaeological research at the site of Canteen Kopje, Northern Cape Province, South Africa, has focused on the rich Earlier Stone Age assemblages recovered from the Younger Vaal Gravels. This paper presents the results of excavation and optically stimulated luminescence (OSL) dating of the overlying Hutton Sands. We discuss the evidence for colonial period interaction between diamond miners and indigenous groups at the site, as well as the presence of an earlier phase of terminal Middle Stone Age/early Later Stone Age occupation. The OSL analyses demonstrate the potential distortion of OSL ages due to substantial bioturbation and its effect on the dating of archaeological sites situated in unconsolidated sands.     

Estimating the number of components in an OSL decay curve using the Bayesian Information Criterion

The optically stimulated luminescence (OSL) decay curve is assumed to consist of a number of first-order exponential components. Improper estimation of the number of components leads to under-or over-fitting of the curve under consideration. Hence, correct estimation of the number of components is important to accurately analyze an OSL decay curve. In this study, we investigated the possibility of using the Bayesian Information Criterion to estimate the optimal number of components in an OSL decay curve. We tested the reliability of this method using several hundred measured decay curves and three simulation scenarios. Our results demonstrate that the quality of the identification can be influenced by several factors: the measurement time and the number of channels; the variability of the decay constants; and the signal-to-noise ratios of a decaying component. The results also suggest that the Bayesian Information Criterion has great potential to estimate the number of components in an OSL decay curve with a moderate to high signal-to-noise ratio.     

Chronostratigraphy of an Eroding Complex Atlantic Round House,Baile Sear,Scotland

A high-resolution chronostratigraphy has been established for an eroding Atlantic round house at Sloc Sàbhaidh (North Uist, Scotland), combining detailed OSL profiling and dating of sediments encompassing the main bracketing events associated with the monument, radiocarbon AMS dates on bone recovered from excavated features and fills within it, and TL dates on pottery and burnt clay. Concordant OSL and radiocarbon evidence place construction of the wheelhouse in the first to second centuries AD, contemporary with dates from the primary occupation. Beneath the wheelhouse, clay deposits containing burnt material, attest to cultural activity in vicinity to the monument in the preceding second to first centuries BC. At a later date, the southern wall collapsed, was rebuilt, and the interior spaces to the monument re-structured. The chronology for the later horizons identified from the sediment luminescence dates extends to the second half of the first millennium AD, which goes beyond the range of the radiocarbon dates obtained. The data from ceramics encompass both periods. The juxtaposition of the dating evidence is discussed relative to short and longer chronologies for this Iron Age monument. Corollaries of this research are the implications that based on the long chronology, some of the ecofacts (bone) appear to be residual, and that the temporal duration of Hebridean Coarse Ware may extend into the second half of the first millennium AD.     

OPTICAL DATING OF GRANITIC STONE SURFACES*

A novel luminescence methodology for dating surfaces of granitoid rocks is presented, with encouraging results for archaeological stone structures. It is based on the zeroing of the latent signal of optically stimulated luminescence (OSL) in feldspar and quartz grains of the stone surface during exposure to daylight. When after bleaching the surface is shielded from light, the OSL signal builds up again, such that its intensity provides an age for the event of the last exposure to light. This event could be the construction or the destruction of stone structures or, for example, sedimentary deposition of granitic boulders, such as in fan deposits. The experimental approach utilizes a high spatial resolution detection technique (HR‐OSL) for OSL of minerals that are left in their original petrological context; that is, without any mineral separation. With this approach, steep gradients in microdosimetry at the surface and at grain boundaries become important and are discussed in detail. The new dating technique is successfully applied to a stone wall of the medieval castle of Lindenfels in southwestern Germany and the pre‐Columbian Nasca lines (geoglyphs) around Palpa in southern Peru.     

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.     

New radiometric ages for the Early Upper Palaeolithic type locality of Brno-Bohunice (Czech Republic): comparison of OSL,IRSL, TL and C dating results

New radiometric data are reported from the recent excavation of the type locality of the Early Upper Palaeolithic entity of the Bohunician. Recently obtained radiocarbon (¹⁴C) data on charcoal are compared with new Optically Stimulated Luminescence (OSL) dating of sediment. OSL ages were determined on sediment from the archaeological occupation at Brno-Bohunice, as well as from the over- and underlying loessic sediments. Multiple techniques were applied, which all gave congruent results. While a dual protocol (post IR-OSL) failed the quality criteria tests, ages were obtained by Multiple-Aliquot-Additive-Dose (MAAD) on polymineral material and Single-Aliquot-Regeneration (SAR) on fine grain quartz extract as well as on polymineral material. Fading tests show significant loss of Infrared Stimulated Luminescence (IRSL) after storage for 3 and 12 months for one sample, but little or no fading for others. The resulting (uncorrected) age estimates are smaller than those on quartz by OSL methods. The latter are considered to be more reliable estimates of the sedimentation age of these deposits. The measured OSL doses do not show a simple distribution and the lowest 5% was used for age calculation to represent the most likely sedimentation age. The quartz from the loess overlying the archaeological layer is OSL dated to 30.9 ± 3.1 ka, while the sediment for the paleosol which contains the archaeological layer gave an age of 58.7 ± 5.8 ka. The attribution of this paleosol to the Hengelo interstadial is therefore questionable. However, if the Hengelo interstadial is correlated with the Dansgaard/Oeschger (D/O) event 12, statistical agreement within 2-σ is achieved. The OSL result for the archaeological layer is in accordance with a weighted average TL date on heated flint artifacts of 48.2 ± 1.9 ka from this layer as well as calibrated radiocarbon data (CalPal Hulu 2007) from nearby locations. However, radiocarbon data on charcoal samples obtained during excavation at Brno-Bohunice 2002 provide age estimates between 30 and 40 ka ¹⁴C-years, which translate to approximately (33) 35–44 ka on the calendric time scale according to the Hulu 2007 model. For the underlying loess a depositional age of 104.3 ± 10.6 ka was obtained by OSL. The presented OSL ages indicate that a simple correlation of soil sequences between sites within a region has to be verified by chronometric dating.     

Recent Excavation and Recording at the New Neolithic Rock Art Site of Vallée Aux Noirs,Buthiers (Seine‐et‐Marne,France)

Following the exceptional discovery of Neolithic engravings on a boulder at Vallée aux Noirs in the Fontainebleau forest, south of Paris, an excavation trench was opened in order to access the buried part of the decorated rock panel and explore the stratigraphic context of the artwork. A palaeosol was found two metres below the modern ground level, underneath multiple layers of sterile sandy soil forming a very compact sequence from which only one archaeological artefact was recovered – an Iron Age fibula (c.200–300 BC). Dating of the palaeosol was attempted through two different methods: AMS dates from charcoal suggest a significant span from the Early Bronze Age to the Iron Age, while two more consistent OSL dates point to formation of the palaeosol during the Late Neolithic (3500–3000 cal BC). The entire engraved rock surface (16 m²), including its buried part, was fully recorded. Four main semiotic groups were identified: a typical fifth‐millennium crook‐hafted axe with a ring, two boats with steering oars, and a central, very tall human figure dominating the composition from its 3.5‐metre height.     

内蒙古鄂尔多斯市乌兰木伦旧石器时代中期遗址

乌兰木伦遗址由邻近的第1、第2和第3地点组成。其中在第1地点获得了石制品2780件、动物化石3423件,并发现用火遗迹。遗址年代为距今7～3万年,属旧石器时代中期。遗址为原地埋藏,其石制品类型及工业组合与欧洲旧石器时代中期文化近似,动物化石则属于华北晚更新世的萨拉乌苏动物群。     

Dating the Ramat Saharonim Late Neolithic desert cult site

The Ramat Saharonim site, located in the central Negev desert, Israel, consists of four shrines in a shallow valley and 30 tumuli, aligned on two cuesta cliffs on the valley's sides. Previous assessments based on site surveys suggested a general chronological span from Late Neolithic period (ca. 5000–5500 BC) through the Early Bronze Age (third millennium BC). Excavations in one shrine and three tumuli revealed a well-constructed double wall at the shrine and seven primary adult burials in the three tumuli. Quartz from sediment samples post-dating the construction of the burials and shrine was dated by optically stimulated luminescence (OSL) using the single aliquot regenerative dose (SAR) protocol, and charcoal and leather samples were dated by ¹⁴C. The OSL results for a burial in one tumulus are 7500 ± 700 to 6000 ± 600 years. In a second tumulus, OSL ages of 2000 ± 200–1800 ± 170 years and a ¹⁴C age on leather of 390–200 BC (2340–2150 cal BP) imply that this burial is Nabatean and that the site was used also in the Hellenistic period. Two ¹⁴C ages on charcoal from the shrine give an age between 5280 and 4710 BC (7230–6660 cal BP). OSL single aliquot ages for sediment from the shrine are highly scattered and far too old (60,000 to 12,000 years). The unlikely old ages are due to insufficient resetting of the OSL signal of some of the quartz grains when sand was blown onto the site. Indeed, single grain measurements for six samples of sediment postdating the shrine show a very large range of grain ages, but with a distinct young population in all samples. Ages calculated from these young populations average 5400 ± 800, in better consistence with the ¹⁴C dates and confirming our supposition that only some of the transported grains were reset at the time of deposition. The combined OSL and ¹⁴C dating shows that the shrines and tumuli are contemporaneous and attributes the complex to the Late Neolithic. This has clear ramifications for our understanding of the period and the rise of desert pastoral societies.     

Preliminary results towards the equivalence of transformed continuous-wave Optically Stimulated Luminescence (CW-OSL) and linearly-modulated (LM-OSL) signals in quartz

The present paper presents a comparative experimental study of two commonly measured Optically Stimulated Luminescence (OSL) signals in quartz. The experimental study measures both the continuous wave OSL (CW-OSL) and the linearly modulated (LM-OSL) signals from the same quartz sample for a range of stimulation temperatures between 180 and 280°C, while the former is transformed to pseudo LM-OSL (ps LM-OSL). A computerized deconvolution curve analysis of the LM-OSL and ps LM-OSL signals was carried out, and the contributions of several OSL components to the initial OSL signal (0.1 s) were shown to be independent of the stimulation temperature used during the measurement. It was also found that the composite OSL (0.1 s) signal consists mainly of the first two OSL components present in the OSL curves. The equivalence of the ps LM-OSL (transformed CW-OSL) and of LM-OSL measurements was also examined by an appropriate choice of the experimental stimulation times, and of the stimulation power of the blue LEDs used during the measurement.     

Monitoring through replication: Design and evaluation of the monitoring reburial at the Laetoli trackway site

Abstract

How is it possible to monitor the condition of a site or artefact after it has been reburied? In the case of the reburial of the extremely fragile and remote site of Laetoli in Tanzania this problem was addressed by creating a replica reburial close to the site in 1995. The method and materials used to rebury the trackway are replicated in the monitoring trench, which thus provides a ‘window’ on the condition of the trackway. A series of samples and indicator objects of different materials placed in the trench are intended to provide an understanding of the burial environment over the long term. Additionally, triangular recesses with sharply defined edges were cut into the floor of the trench to allow determination of the mechanical stability of the tuff to deformation under the reburial overburden. The trench was lined with root-inhibiting Biobarrier® geotextile and then reburied in the same manner as the trackway; existing acacia trees at the edge of the trench were allowed to remain. In 1997 excavation of part of the trench was undertaken. Of particular interest was the fine detail of the topography of the floor of the trench and the effectiveness of the Biobarrier®. Geosynthetics showed no evidence of deterioration, but severe degradation of all wood samples without preservative chemical treatment and of indicator objects indicated a very aggressive environment. Many of the findings, such as survival or deterioration of the indicator objects, use of geosynthetics and the efficacy of Biobarrier®, have relevance to a broader understanding of buried environments.     

Chronology during the Bronze Age in the archaeological site Tell Qubr Abu al-‘Atiq, Syria

Archaeosediments are deposits with a direct or indirect anthropogenic component. They provide useful information about past human activities and interaction with the environment. When other materials, such as pottery, are present in archaeosediment layers, the combination of TL ages from pottery and OSL ages from sediments can provide complete data about the occupation and evolution of an archaeological setting. In Mesopotamia, tells are mounds formed by the debris of human occupation and the accumulation of muddy sediments mainly due to the decomposition of mud bricks in ancient towns. Many other materials such as pottery fragments, bones and charcoal can be found in the sediment layers. The combination of OSL, TL and radiocarbon ages can be very useful in the case of the Bronze Age Period in Syria, allowing the occupation sequence of such archaeological sites to be reconstructed. Tell Qubr Abu al-’Atiq, is located on the left bank of the Middle Euphrates River (Syria). The archaeological artefacts found in the sediment layers (pottery) collected during excavations in two areas of the site, indicated the occupation of the tell during the Early and Late Bronze Age by typological pottery classification. The radiocarbon ages of charcoal indicate that human occupation fits the archaeological hypothesis, providing an older and maximum occupation period between 2800 and 2300 BC and a younger period between 1400 and 900 BC. OSL dating of sediments shows ages younger than charcoal, while TL ages of pottery are generally older than sediment and charcoal ages. This can be explained as the different materials correspond to different events. The charcoal and pottery correspond to occupation periods, while sediments correspond to the further destruction of the site.     

Luminescence dating of prehistoric hearths in Northeast Qinghai Lake and its paleoclimatic implication

Archeological research has been trying to provide evidence relevant to understanding both the timing of and processes responsible for human colonization of the Qinghai-Tibetan Plateau (QTP). Hearth is one of the most extensive, important, and typical prehistoric humanity activity evidence on the QTP. However, there are a number of hearths lacking charcoal material because of the wind and water erosion. Fortunately, most of these hearths can be dated by luminescence dating on the remnant sediments around the hearth. In this study, 18 optically stimulated luminescence (OSL) samples from 14 hearths in Yandongtai site (YDT) and Bronze Wire site (BW) in the northeast of Qinghai Lake area were systematically dated. The OSL ages range from 6.8 ± 0.7 to 14.4 ± 1.2 ka. There is a good agreement between OSL dating results and charcoal ages during the last deglaciation period, which indicates that OSL method has great potential in dating hearth on QTP. Combined with the previous dating results from other hearths, the age of hearths concentrates in 11–13 ka BP, i.e., the Younger Dryas (YD) chronozone. The increased number of hearths indicates reinforced colonization in the Qinghai Lake area during YD cold event, implying that the cold climate during YD event was not severe enough to hinder the inhabitation of prehistoric humanity at an elevation of 3.2 km.