Multiple approaches to date Japanese marker tephras using optical and ESR methods

The present study aimed to test reliability of luminescence and electron spin resonance (ESR) methods to date tephra. We investigated on three Japanese marker tephras, Ikeda-ko (6.4 ka), Aira-Tn (30 ka) and Aira-Iwato (45–50 ka). A systematic studies were performed using different minerals (quartz and feldspar), different grain fractions (75–250 and 250–500 μm), different luminescence and ESR signals, like optically stimulated luminescence (OSL) of quartz, infrared stimulated luminescence (IRSL) of feldspar, including recently developed least faded post infrared IRSL (pIR-IRSL), and ESR signals from paramagnetic centers Al and Ti–Li of quartz. Ages obtained using pIR-IRSL signal of plagioclase with preheat of 320 °C, 60 s and stimulation at 300 °C are consistent with the reference ages. High dose detection range (up to ∼600 Gy) and accurate age estimation enable pIR-IRSL of feldspar a promising methodology to date quaternary tephra. ESR ages from quartz are grossly correlated with the reference ages but large deviation and large associated errors are observed, possibly due to either low signal to noise ratio or heterogenous dose response of different aliquot in multiple aliquot additive dose (MAAD) approach.     

Quartz luminescence dating of Anglian Stage (MIS 12) fluvial sediments: Comparison of SAR age estimates to the terrace chronology of the Middle Thames valley,UK

Quartz optically stimulated luminescence (OSL) is increasingly being used to constrain the depositional age of fluvial and glaciofluvial sequences over orbital (Milankovitch) timescales within the British Isles. Few of these previous studies have had any age control; however there is some evidence that OSL ages based on the single aliquot regenerative dose (SAR) protocol may be subject to systematic age underestimation as samples approach saturation. In this study, the age of 12 luminescence samples from a chronologically well-constrained site dating to 450 ka from the Thames terrace sequence, southern Britain, was measured using SAR in order to test the performance of the method close to its upper age limit. The characteristics, dose response and thermal stability of the OSL signal in these samples were assessed by investigating equivalent dose (D_e) as a function of stimulation time and component-resolved pulse annealing. Despite the fact that the samples are dominated by the quartz fast component, these results showed that both the medium and slow components have lower stabilities than the fast component, but with the unstable medium component most affecting the initial part of the OSL signal used in dating. Based on isolating the fast component either through curve fitting or eliminating the medium component using the early background subtraction method, OSL ages up to 450 Gy were found to compare well with the expected age of the site of 450 ± 23 ka. In contrast, a systematic age underestimation of 10% was manifested at lower doses when using the initial part of the OSL signal, contaminated by the medium component. These results suggest that the early background subtraction method should be used when dating in the non-linear part of the growth curve as it provides a better separation of thermally unstable signals and represents a more convenient approach than curve fitting in well-behaved samples.     

Luminescence dating of quartz from ironstones of the Xingu River,Eastern Amazonia

This study reports on the first investigation into the potential of quartz luminescence dating to establish formation ages of ferruginous duricrust deposits (ironstones) of the Xingu River in Eastern Amazonia, Brazil. The studied ironstones comprise sand and gravel cemented by goethite (FeO(OH)), occurring as sandstones and conglomerates in the riverbed of the Xingu River, a major tributary of the Amazon River. The Xingu ironstones have a cavernous morphology and give origin to particular habitat for benthic biota in an area that hosts the largest rapids in Amazonia. So far, the Xingu ironstones have uncertain formation ages and their sedimentary origin is still poorly understood. In this way, seven samples of ironstones distributed along the lower Xingu River were collected for optically stimulated luminescence (OSL) dating of their detrital quartz sand grains. Additionally, the organic content of some samples was dated by radiocarbon (¹⁴C) for comparison with quartz OSL ages. The luminescence ages of the sand-sized quartz grains extracted from the ironstones were obtained from medium (100–300 grains) and small (10–20 grains) aliquots using the single aliquot regenerative-dose (SAR) protocol. Equivalent doses (D_e) distributions have varied overdispersion (OD) both for medium size aliquots (OD = 19–58 %) and small size aliquots (OD = 29–76 %). No significant trend was observed between D_e and aliquot size. The studied ironstones grow over the riverbed, but stay below or above water throughout the year due to the seasonal water level variation of the Xingu River. However, the effect of water saturation in dose rates is reduced due to relatively low porosity of ironstones. Water saturated dose rates (dry sample dose rates) range from 2.70 ± 0.21 (2.79 ± 0.22) Gy/ka to 12.34 ± 0.97 (13.26 ± 1.12) Gy/ka, which are relatively high when compared to values reported for Brazilian sandy sediments elsewhere (∼1 Gy/ka). Samples with high overdispersion (>40 %) are mainly attributed to mixing of grains trapped in different time periods by goethite cementation. The obtained OSL ages for water saturated (dry) samples range from 3.4 ± 0.3 (3.3 ± 0.4) ka to 59.6 ± 6.0 (58.1 ± 6.4) ka, using D_e determined from medium size aliquots and dose response curves fitted by an exponential plus linear function. Radiocarbon ages of the bulk organic matter extracted from selected ironstone varied from ca. 4 cal ka BP to ca. 23 cal ka BP. Significant differences were observed between OSL and radiocarbon ages, suggesting asynchronous trapping of organic matter and detrital quartz within the ironstone matrix. These late Pleistocene to Holocene ages indicate that ironstones of the Xingu River result from an active surface geochemical system able to precipitate goethite and cement detrital sediments under transport. The obtained ages and differences between OSL and radiocarbon ages point out that the ironstones have multiphase and spatially heterogeneous growth across the Xingu riverbed. Our results also expand the application of luminescence dating to different sedimentary deposits.     

A multi-method approach to dating middle and late Quaternary high relative sea-level events on NW Svalbard – A case study

Waxing and waning ice sheets and changing sea levels have been interpreted from the Quaternary stratigraphic record at Leinstranda, Brøggerhalvøya in NW Svalbard. We have identified seven high relative sea-level events, related to glacio-isostatic loading, and separated by at least four glacial events. To establish a chronology for the high sea-level events (interstadials and interglacials) and the intervening glaciations, we have used three different absolute dating methods: optically stimulated luminescence (OSL) of shallow marine deposits, and electron spin resonance (ESR) and radiocarbon (AMS-¹⁴C) dating of fossils contained in these sediments. Of the absolute dating methods, OSL has provided the stratigraphically most consistent dataset and which also matches a biostratigraphically inferred interglacial. The ESR ages of mollusc shells suffer from low precision due to unusually large uranium content in most dated shell samples, which in turn is most likely a result of significant recent uranium enrichment of the sediments. Most radiocarbon ages are non-finite. The results show that the high relative sea-level events range in age from the Saalian sensu lato (≥Marine Isotope Stage, MIS, 6) to the early Holocene (MIS 1), and include events OSL-dated to 185 ± 8 ka, 129 ± 10 ka, 99 ± 8 ka and 36 ± 3 ka. The methods used by us and by previous investigators of the same site are compared and assessed, and sources of error, accuracy and precision of ages are discussed.     

Luminescence dating of a hearth from the archaeological site of Jiangxigou in the Qinghai Lake area of the northeastern Qinghai-Tibetan Plateau

Archeological research over the past several years has started to provide evidence relevant to understanding both the timing of and processes for human colonization of the high Qinghai-Tibetan Plateau. Much of this research has been in the Qinghai Lake area and the Qaidam Basin in the northeastern Qinghai-Tibetan Plateau. However, chronological data are still limited. Recently, a hearth was discovered in the Jiangxigou site in the south of the Qinghai Lake area, which was likely used by prehistoric hunters. The site is in the mouth of a canyon approximately 4.5 km from Qinghai Lake. Previous ages in this site are based on ¹⁴C dating only. The current study provides additional OSL dates for the hearth. The ages of four OSL samples bracketing the hearth range from 12.9 ± 0.9 to 14.4 ± 1.0 ka, but standard deviations overlap extensively and they likely represent the same age. The OSL ages show that by about 14.3 ± 1.0 ka prehistoric peoples were living in the Qinghai Lake area.     

Radiometric dating of Meipu hominin site in China by coupled ESR/U-series and cosmogenic 26Al/10Be burial dating methods

The Three Gorges and Western Hubei area in the geographic central part of China was a potential migration corridor for early hominin and mammals linking South and North China during the Pleistocene period. Some key early hominin sites are known in this region where limestone cave and fissure sites are numerous but difficult to date as beyond the dating range of OSL and mass spectrometry U-series method. Here, we report radiometric dating study for such a hominin site, Meipu (Hubei Province), by coupled ESR and U-series dating of nine fossil teeth and cosmogenic ²⁶Al/¹⁰Be burial dating of one quartz sediment. The burial age calculated by simple burial model (573 ± 266 ka) gives a minimum age constraint of the sediment. The fossil dating provided two main age groups at 541 ± 48 ka and 849 ± 39 ka, the older age group is in agreement with the U-series age (>630 ka) of the flowstone overlying the fossil layer and the paleomagnetic data which placed the Brunhes-Matuyama boundary in the fossil layer. The reason of this age difference is probably caused by the U-content discrepancy in the enamel of the dated fossil samples. This study exhibits the limitation of ESR/U-series fossil dating and the importance of using multiple dating approach when it is possible in order to identify the problematic ages.     

Feldspar multi-elevated-temperature post-IR IRSL dating of the Wulanmulun Paleolithic site and its implication

The Wulanmulun site found in 2010 is an important Paleolithic site in Ordos (China), from which lots of stone and bone artifacts and mammalian fossils have been recovered. It was previously dated by radiocarbon and optically stimulated luminescence (OSL) techniques on quartz. To further confirm the reliability of the chronology constructed based on OSL ages and test the applicability of the recently developed pIRIR procedure on sediments from northern China, twenty-four sediment samples (including eolian, lacustrine and fluvio-eolian sands) from the site were determined using the multi-elevated-temperature post-IR IRSL (MET-pIRIR or pIRIR) procedure on potassium feldspar. The results show that the studied samples have two MET-pIRIR D_e preheat plateaus (280–320 and 340–360 °C), and the bleaching rates of the luminescence signals are associated with sample ages and stimulation temperatures. All the pIRIR ages (7–155 ka) corrected for anomalous fading and residual dose obtained after solar bleaching for 15 h are larger than the corresponding quartz OSL ages (4–66 ka) previously determined, even for the young eolian samples (<10 ka). But the corrected IRSL(50 °C) ages (6–85 ka) are broadly consistent with the quartz ages. It appears that the IRSL(50 °C) ages are more reliable, although this contradicts the previously results obtained by other people. On the other hand, we also obtained an extended age plateau between the stimulation temperatures of 50 and 290 °C in the plot of age versus stimulation temperature (A-T plot) by subtracting different residual doses obtained after different bleaching times. The reliability of the plateau ages requires further investigation. For the sediment samples from this site, quartz should be more suitable for dating than K-feldspar, and the quartz OSL ages of 50–65 ka for its cultural layer should be reliable.     

A targeted drilling and dating campaign to identify Stone Age archaeological sites before excavation in west coast southern Africa

Here we present the results of a targeted drilling campaign that facilitated a geochronological study with coarse sampling resolution inside a new cave site, Simons Cave, on the west coast of southern Africa. A combination of radiocarbon (¹⁴C) dating and optically stimulated luminescence (OSL) dating was used as a range-finder. Results confirmed preservation of Holocene and late Pleistocene sediments up to 133 ± 35 ka, overlapping with the ages of Middle Stone Age (MSA) occupations of the broader west coast region. A subsequent, systematic test-excavation at the site then embarked on a second geochronological study with a higher sampling resolution. Ultimately, the comparative study confirmed the potential of Simons Cave as a new site for the exploration of hominin occupation through the later Pleistocene and Holocene, yet raised several issues concerning the direct comparability of information deriving from drilled sediment cores and actual archaeological excavation.     

OSL dating of individual quartz ‘supergrains’ from the Ancient Middle Palaeolithic site of Cuesta de la Bajada,Spain

Dose saturation represents a fundamental limitation for obtaining finite optically stimulated luminescence (OSL) quartz ages over Middle Pleistocene timescales. Single-grain OSL studies typically reveal significant intra- and inter-sample variability in quartz dose saturation properties at the individual grain level. This enhanced variability may offer the potential to obtain extended-range chronologies exceeding the traditional upper age limits of multiple-grain OSL dating. However, there have been relatively few detailed assessments of single-grain OSL properties over high dose ranges. In this study we investigate extended-range single-grain OSL dating potential at Cuesta de la Bajada, one of the most important Ancient Middle Palaeolithic sites in the Iberian Peninsula. The quartz samples from this site exhibit exceptional dose saturation properties and contain significant populations of individual ‘supergrains’ with bright OSL signals, very high characteristic saturation dose (D₀) limits of 200 to >600 Gy, and dose-response curves that closely conform to single saturating exponential functions. Assessments of OSL signal composition and the ability to successfully recover a known laboratory dose of 470 Gy support the potential for obtaining high equivalent dose (D_e) values with reasonable fitting uncertainties. A series of novel sensitivity tests are used to assess potential biases in supergrain D_e estimation over high dose ranges related to (i) thermally transferred signal contributions, (ii) choice of dose-response curve fitting function, and (iii) insufficient dose saturation properties of individual grains. The single-grain D_e values obtained using the standard quality assurance criteria and novel sensitivity tests are consistent at 2σ, and are in agreement with quartz Ti-centre ages obtained on two of three paired electron spin resonance (ESR) samples collected from Cuesta de la Bajada. These comparisons support the suitability of our single-grain OSL results and suggest there may be good potential for using quartz supergrains to establish extended-range chronologies at some Middle Pleistocene sites. Comparisons with other single-grain OSL studies across the Iberian central plains suggest that favourable dose saturation properties may be influenced by regional-scale geological controls. The importance of undertaking single-grain OSL dating at Cuesta de la Bajada is also demonstrated by the results of synthetic aliquot experiments, which reveal multiple-grain age offsets of 60–170 ka when unsuitable grain types are inadvertently included in the final age calculations. The single-grain OSL results indicate that the main archaeological horizon at Cuesta de la Bajada (unit CB3) accumulated between 264 ± 22 and 293 ± 24 ka. These ages are consistent with the chronologies of other key early Middle Palaeolithic sites in the region (Ambrona AS6 and Gran Dolina TD10) and indicate that the Ancient Middle Palaeolithic techno-complex likely spread across Iberia from at least Marine Isotope Stage 9 onwards.     

Optical dating of a hyperconcentrated flow deposit on a Yellow River terrace in Hukou,Shaanxi, China

A sand layer, interpreted as a hyperconcentrated flow deposit, was found interbedded between loess on a Yellow River terrace in Hukou, Shaanxi, China. The site is known as the Longwangchan Palaeolithic site. The deposits from the terrace were dated using optically stimulated luminescence (OSL). Two samples from the sand layer were dated to 30 ± 2 and 33 ± 3 ka using coarse-grained (CG) quartz, and to 82 ± 7 and 94 ± 5 ka using fine-grained (FG) quartz, respectively. The CG quartz OSL ages are believed to be reliable on the basis of the OSL ages of the bracketing loess samples. The overestimation of the FG quartz OSL ages of the sand samples is explained in terms of hyperconcentrated flow processes during sediment transport and deposition. The large difference between the CG and FG quartz OSL ages of the sand samples helps to better understand the formation of the hyperconcentrated flow deposit. The hyperconcentrated flow deposit in this study indicates an extreme river flood occurring at ～30 ka in this area. In addition, the stone artifacts found in the lower loess layer overlying the bedrock of the terrace were dated to ～47 ka.     

ESR/U-series dating of Eemian human occupations of Northern France

Palaeolithic sites associated with the Eemian Interglacial (MIS 5e) are very rare in NW Europe, and especially in Northern France, where their preservation is restricted to very specific geological contexts, in association with carbonated tufa (Caours) or peat deposits (Waziers). In order to check the reliability of ESR/U-series method to date teeth recovered from archaeological levels in such specific geological environments, teeth were sampled on these two Middle Palaeolithic sites and systematic in situ dosimetry was performed using portable gamma spectrometer. The ESR/U-series ages obtained on the Caours site are very homogeneous allowing the calculation of a mean age equal to 125 ± 11 ka, in agreement with the geological age, mammal's association and other available geochronological data (U-series on tufa carbonate, TL on burnt flints, OSL on sediments), despite a relatively heterogeneous dosimetric environment (gamma dose rate ranging between ca 200–450 μGy/a). At Waziers, reducing (water logging) environment linked to the peat leads to very specific U-series data of the analysed teeth (U content lower than 0.1 ppm in all the dental tissues, evidence of leaching in some tissues), but the mean ESR/U-series age, 129 ± 4 ka, is also in agreement with the available geological and palaeoenvironmental data indicating that the dated teeth were associated with Late Glacial deposits prior to the climatic interglacial optimum. These two case studies then confirm the reliability of ESR/U-series method to date with good reliability and accuracy the archaeological levels linked to such relatively short climatic events (ca 10 ka).     

Optical dating of flowstone and silty carbonate-rich sediments from Panxian Dadong Cave,Guizhou, southwestern China

Panxian Dadong Cave located in the western Guizhou is a very important Paleolithic site in China. At this site bone and stone artifacts, human teeth and mammalian fossils (known as Ailuropoda-Stegodon fauna) were found, and the site was previously dated to 120–300 ka using ESR/uranium-series methods. In this study, we successfully extracted fine quartz grains from flowstone and silty carbonate-rich sediments in the excavated area. The quartz extracts displayed excellent luminescence properties, and satisfied the SAR (single-aliquot regenerative dose method) acceptance criteria. The sensitivity-corrected OSL signals are not saturated at a dose up to about 1400 Gy. The cultural unit was OSL dated to 190–300 ka, corresponding to MISs 7–8. The flowstone deposits overlying the cultural unit were determined to be 13–190 ka and the silty carbonate-rich sediments underlying the cultural unit to be 300–360 ka. The optical ages are in general agreement with the coupled ESR/U-series and U-series ages.     

OSL-dating the Quaternary landscape evolution in the Vértes Hills forelands (Hungary)

Fluvial, colluvial, and aeolian sediments were dated by optically stimulated luminescence (OSL) on quartz to improve the chronological framework for Quaternary sedimentation and landscape evolution in the forelands of the Vértes Hills (central Hungary). The separated quartz was suitable for age determination based on an OSL SAR protocol. Most samples have asymmetric equivalent dose distributions and OSL ages were calculated by the mean, central, and minimum D_e values. Considering geomorphology and earlier age data from the area, the central D_e values seem most appropriate for age calculation. A fan on the geomorphological level QV in the western foreland of the Vértes Hills was deposited 79–75 (±8) ka ago. In the south-eastern foreland an alluvial fan on level QIIb is at most 42 ± 4 ka old. Fluvial incision and aggradation occurred 16–10 (±1) ka ago on the geomorphic surface QIIa. Loess is 14 ± 1 ka old, and slope sedimentation was active 11–9 (±1) ka ago. Our OSL data demonstrate that in the north-western foreland of the Vértes Hills wind remained an important agent after the last glacial times, into the early Holocene (9–8 ± 1 ka) and was able to accumulate large aeolian dunes.     

On the interest of using the multiple center approach in ESR dating of optically bleached quartz grains: Some examples from the Early Pleistocene terraces of the Alcanadre River (Ebro basin,Spain)

The present work reports the first numerical ages obtained for the two highest fluvial terraces (Qt1 and Qt2) of the Alcanadre River system (Northeastern Spain) representing the earliest remnants of Quaternary morphosedimentary fluvial activity in the Ebro basin. ESR dating method was applied to optically bleached quartz grains and both the Al and Ti centers were measured, in accordance with the Multiple Center approach. The results are overall in good agreement with the existing preliminary chronostratigraphic framework and our interpretation indicate that terraces Qt1 and Qt2 have an ESR age of 1276 ± 104 ka and 817 ± 68 ka, respectively. These data provide some chronological insights on the beginning of the fluvial sedimentary processes in a scenario of incision maintained over Quaternary in the Ebro Basin. These are among the first numerical ages obtained for such high terraces in the Iberian Peninsula.Our results demonstrate the interest of using the Multiple Center approach in ESR dating of quartz, since the two centers provide complementary information, i.e. an independent dose control. The overall apparent consistency between the ESR age estimates and the existing preliminary chronostratigraphic framework may be considered as an empirical evidence that the Ti–Li center may actually work for Early Pleistocene deposits, whereas the Ti–H center shows some clear limitations instead. Finally, these results demonstrate the interest of using ESR method to date Early Pleistocene fluvial terraces that are usually beyond the time range covered by the OSL dating method.     

Age comparison by luminescence using quartz and feldspar on core HPQK01 from the Pearl River delta in China

Reliable chronology is critical for reconstructing estuarine delta process. In this study, detailed chronological framework has been performed on a core HPQK01 (52 m in depth) from the central Pearl River delta (PRD) of China. Both quartz OSL and feldspar post-IR IRSL (pIRIR) methods for late Pleistocene sediments, as well as radiocarbon dating for Holocene sediments, were applied to date the core. Results show that quartz OSL ages range from 125 ± 18 ka to 58 ± 6 ka, and that all of them were minimum ages due to the OSL signal saturation. Feldspar pIR₂₀₀IR₂₉₀ protocol shows some overestimation in dose recovery test, with the recovered to the given ratio of 1.2, while a ratio of around 1 was obtained for feldspar pIR₅₀IR₂₅₀ signals. Robust ages have been obtained from feldspar fading corrected pIR₅₀IR₂₅₀ dating with ages ranging from 150 ± 17 ka to 98 ± 12 ka. AMS ¹⁴C results suggest that subtidal-intertidal zone was deposited during the middle Holocene from 8.21 ± 0.19 cal ka BP to 4.99 ± 0.25 cal ka BP. The sedimentology of core HPQK01 record two marine transgressive-regressive cycles. Based on the dating results, the lower fluvial sediment unit (T2) could be correlated to marine isotope stage (MIS) 6, and the lower marine unit (M2) was deposited during MIS 5. A sedimentary hiatus occurred with age range of from MIS 4 to MIS 2. Since middle Holocene, another marine stratum (M1) has been accumulated. Overall, our findings suggest that feldspar pIRIR dating method has the potential to establish the Quaternary chronostratigraphic framework of the PRD for samples with ages within 150 ka.     

Luminescence dating of a megaflood event on a terrace of the Jinsha River,China

The numerical dating of megaflood sediments is a worldwide challenge, a fact that has impeded a full understanding of Late Quaternary dam-outburst flood processes that occurred along the river courses of the Tibetan Plateau. Optically stimulated luminescence (OSL) dating has been widely used on such sediments. Due to their short transportation distances prior to deposition, the OSL signals of megaflood sediments are often partially bleached, resulting in age overestimations. Here, we report on a comparison of OSL ages obtained using both quartz (4–11 μm FG; 90–125, 180–250 μm CG) and K-feldspar (180–250 μm CG) extracted from sediments taken from the Binghong-Bingnong Neolithic-Bronze Age site on the second Jinshan River terrace (T2), in Yunnan Province, southwestern China. Contrary to previous experience suggesting that CG fractions are usually better bleached than FG fractions prior to deposition, our results showed that the OSL ages for the FG quartz fraction were generally younger than those for the CG fraction. This would suggest that the two fractions may have come from different sources, and may have been subject to different geomorphological processes prior to deposition. FG quartz fractions may be suitable to define the maximum age of sediments located in alpine gorge regions. CG quartz fractions can be used by applying the minimum age model (MAM) to select relatively well-bleached grains yielded ages close to the ‘true’ burial ages of the sediments. The results showed that the post-IR IRSL₂₂₅ ages of single grain K-feldspar were overestimated by > 3 ka, suggesting K-feldspar may not be suitable dating material for megaflood sediments <30 ka. The OSL dates suggest that the T2 terrace was formed ∼8.4 ka, that aeolian sediments were deposited during ∼2.6–1.5 ka, and that the megaflood event occurred after ∼1.5 ka.     

Evaluating OSL-SAR protocols for dating quartz grains from the loess in Ili Basin,Central Asia

Late Pleistocene records of loess deposition are a critical archive for understanding terrestrial paleoenvironment changes in Central Asia. The age of loess is not well known for the deserts regions and surrounding high plateaus in Central Asia. Previous studies have shown that there remains a disparity between ages for loess deposition by luminescence and ¹⁴C dating. This study evaluates the potential of optically stimulated luminescence (OSL) to date a loess sequence resting on fluvial sands in the east Ili Basin, Central Asia. The single-aliquot regenerative-dose (SAR) protocol on coarse grain quartz was employed for equivalent dose determinations. The basal fluvial sand returned a secure OSL age, with low overdispersion value in equivalent doses (19 ± 2%) of ca. 36 ka and provides a close, but maximum age estimate (within 5 ka) on the initiation of loess deposition. However, the loess yielded high overdispersion values for equivalent doses and age reversals, coincident with diffuse paleosols; indicating that pedoturbation with loess deposition may be a dominant process. OSL ages between ca. 45 and 14 ka calculated using a maximum age model and OSL ages from other sites in the Basin suggests that the latest major period of loess deposition was between 70 and 10 ka ago. A future hypothesis to test based on these analyses is that there may be three periods of heightened loess deposition at ca. 45, 35 to 19 and 14 ka, when desert source areas to the west were particularly dry.     

The earliest prehistoric pottery in the Qinghai-Tibetan Plateau and its archaeological implications

Remains of prehistoric human activity in the Qinghai-Tibetan Plateau (QTP) were often found exposed in the surface due to strong erosion. Thus, archaeological sites containing continuous and integral cultural remains within stratigraphic layers are rare in the plateau. The Jiangxigou site, located in the south of Qinghai Lake basin and in the northeastern margin of the plateau, are such a site with ages ranging from the early to late Holocene, i.e. from the Paleolithic to the Neolithic. Our excavation disclosed remains including more than 700 pieces of microliths, 14 pottery pieces, and other cultural relics. The oldest pottery fragments were found at the depth of 75 cm in the section, and in particular, a painted pottery piece was found at the depth of 61 cm. In this study, both luminescence (TL and OSL) and radiocarbon dating were employed to establish the chronology for these remains. Two pieces of pottery were dated using thermoluminescence (TL), another two pieces of pottery were dated by OSL, and three charcoal samples by AMS ¹⁴C. TL age of pottery piece P14 from the depth of 75 cm is 7.06 ± 0.51 ka, making it the earliest pottery in the Tibetan Plateau. The AMS ¹⁴C age of charcoals from the same depth of 75 cm is 6805 ± 95 Cal a BP, in agreement with TL age of P14. OSL age of pottery P12 from the depth of 60–70 cm is 6.50 ± 0.47 ka, and OSL age of pottery P9 from 54 cm is 4.97 ± 0.25 ka. Thus, the age of the painted pottery piece at the depth of 61 cm should be ∼5.50 ka by interpolation, making it the earliest painted pottery in the QTP. The pottery P14 has many common features similar to that of the Yangshao culture in China. We suggest that, before 7 ka, hunters using microlithic had been living in the northeastern margin of the QTP. Since 7 ka, these native microlithic hunters had been affected by the Neolithic Yangshao culture from the Loess Plateau, which was characterized by well-developed pottery. Agricultural growers migrated from the lower elevation of the Loess Plateau to the east of the QTP, leading to profound cultural exchanges with highland native microlithic hunters.     

OSL chronology and accumulation rate of the Nakdong deltaic sediments,southeastern Korean Peninsula

Optically stimulated luminescence (OSL) dating was performed on Late Quaternary deltaic sequences from a 55-m-long core sampled from the Nakdong River estuary, Korea. OSL ages obtained from chemically separated fine (4–11 μm) and coarse (90–212 μm) quartz grains ranged from 29.4 ± 2.6 to 0.4 ± 0.04 ka, revealing clear consistency between the grain-size fractions. The D_e values from the standardized growth curve (SGC) are consistent with those from the single-aliquot regenerative-dose (SAR) procedure, which suggests that the SGC is valid for the Nakdong deltaic sediments. The ¹⁴C ages of shells and wood fragments ranged from 11 to 2.9 ka, demonstrating reasonable agreement with the OSL ages, within the error range. However, the limited number and random sampling interval of the ¹⁴C age data (10 ages) result in a simple linear and exponential trend in the depth–age curve. In contrast, OSL ages obtained by high-resolution sampling show down-section variations in the depth–age curve, indicating the occurrence of rapid changes in sedimentation rate. It is suggested that the high-sampling-resolution OSL ages provide a more realistic and detailed depth–age curve and sedimentation rate. The Nakdong deltaic sediments were divided into five units based on sedimentation rate. The lowest (unit 5) shows a break in sedimentation between the last glacial maximum (LGM) and the Holocene. The sedimentation rate increased in units 4 and 3, presumably corresponding to the early to middle Holocene sea level rise and high stand. Unit 2 shows a gradually decreasing sedimentation rate following the regression of the shoreline, until about 2 ka. The progradation of the Nakdong River delta resulted in the rapid accumulation of unit 1 during the last 2000 years.     

Luminescence dating of baked earth and sediments from the Qujialing archaeological site,China

The Qujialing site is a representative Neolithic archaeological site in the middle reaches of the Yangtze River, China. Absence of suitable material for radiocarbon dating in this region makes the timing of the similar sites difficult. Here we applied optically stimulated luminescence (OSL–SAR) and thermoluminescence (TL–SAR) techniques to date the archaeological and natural deposits from the Qujialing site with known age, testing the techniques on samples at archaeological sites in this region. The results showed that the luminescence properties of quartz from sediment and baked earth samples are very similar. The quartz OSL ages obtained for a sediment sample and a baked earth sample from the cultural layer are 5.4 ± 0.3 and 5.1 ± 0.3 ka, respectively. The quartz TL age of the baked earth sample is 5.6 ± 0.5 ka. These dates are consistent with the calibrated radiocarbon ages (4.9 ± 0.1 and 5.1 ± 0.1 ka cal BP (±1σ)) of the two charcoal samples from the cultural layer at a nearby locality, and are also in agreement with the age of Qujialing culture period. The results indicate that the OSL dating techniques can be applied to date similar archaeological sites in the middle reaches of the Yangtze River, China.