OSL dating of flood sediments in the North China Plain

Luminescence dating of glacial deposits near the eastern Himalayan syntaxis using different grain-size fractions

OSL dating of coastal sediments from the southwestern Korean Peninsula: A comparison of different size fractions of quartz

Optically stimulated luminescence (OSL) dating has gained increased use in dating deltatic deposits, however, its application can be hindered by the problem of incomplete bleaching. To address this limitation, we test the single-grain OSL method for the first time in the Yangtze River delta. A total of eight OSL and 14 AMS 14C samples were obtained from a 50.8m long sediment core from the incised valley of the delta. Quartz extracted from eight OSL samples from the core was first measured with small multi-grain aliquots using medium- (45–63μm) and coarse-grained (90–125μm or 150–180μm) fractions to test the internal consistency of their respective ages. The results showed that four of five medium-grained quartz samples appeared to be well bleached. In contrast, the coarse-grained quartz samples revealed poor bleaching, except for two samples from the delta front facies. Five coarse-grained quartz OSL samples were further analyzed using a single-grain OSL technique. Only 0.5–0.7% of the grains passed the rejection criteria. Single-grain OSL dating is appropriate for age determination of coarse-grained sediments which have been affected by incomplete bleaching. However, it consumes a lot of instrument time. Central and minimum age models (CAM and MAM) were used to calculate the burial age of the samples; MAM ages fit best in the stratigraphic sequence. Small aliquots are recommended as effective in identifying incomplete bleaching for medium- or coarse-grained quartz. A comparison of AMS 14C dates and OSL ages shows that 14C values are 1–3ka older than OSL ages. According to the OSL ages, core SD experienced rapid accumulation 10–8ka and in the last 2ka. The former is linked to rapid sea-level rise in early Holocene, while the latter is primarily due to the migration of depo-center towards the core site, rather than entirely increased sediment delivery caused by human activities.

Flood events in the lower reaches of the Yellow River: OSL and radiocarbon dating on the Anshang site

Optically stimulated luminescence (OSL) dating of polymineral fine-grained loess samples collected from the southern Loess Plateau of China was conducted using the single-aliquot regenerative-dose (SAR) protocol. A ‘Double-SAR’ procedure in which aliquots are subjected to both infrared (IR) and blue stimulations was used, and two sets of equivalent dose (D e ) determinations were produced. These doses are assumed to be predominantly related to the feldspathic and quartz fine grain populations, respectively. The results revealed that the OSL ages estimated by infrared stimulated luminescence (IRSL) signals and those estimated by [post-IR] stimulated luminescence ([post-IR] OSL) signals disagreed. Specifically, the ages estimated using the IRSL signals were smaller than those estimated using [post-IR] OSL signals. The results of an anomalous fading test of the two types of OSL signals revealed that the [post-IR] OSL signals from the etched sub-sample (by H2SiF6 and HF) and the un-etched sub-sample did not fade significantly. However, the IRSL signals from the un-etched sub-sample showed obvious signs of fading. These findings indicate that the lower age estimated by IRSL is due to the anomalous fading of feldspar IR signals in the polymineral fine grains. For samples collected from greater than 100 cm, the estimates of their OSL ages using two types of luminescence signals generally agreed with their pre-estimated ages, especially those of the [post-IR] OSL signals. However, for the three samples that were collected from a depth of less than 100 cm, their OSL ages were remarkably underestimated, possibly due to the enhanced human activity (such as soil cultivation) that has occurred in the region since 3000 a B.P.

이 논문에서는 경주시 양남면에 분포하는 해발고도 약 45 m의 수렴단층 노두 해안단구 퇴적층의 형성시기를 추정하기 위하여, 퇴적층을 구성하고 있는 석영에 대한 단일입자 OSL(Single Grain Optically Stimulated Luminescence) 연대측정을 실시하였다. 실험에 사용된 총 1200개의 석영입자 중, 93개의 입자가 연대측정에 적합한 OSL 신호특성을 보였으며, 이들의 등가선량은 50-610 Gy까지 넓은 분포를 보인다. 이 자료를 중심연대모델(Central Age Model)과 최소연대모델(Minimum Age Model)을 이용하여 분석하면, 각각 <TEX>$83{\pm}4ka$</TEX>와 <TEX>$60^{+3}{_{-7}}ka$</TEX>의 연대가 도출되지만, 이들 연대는 MIS 5a시기로 보고된 기존의 제2해안단구의 OSL 연대와 층서적으로 불일치한다. 단일입자 OSL 분석결과들을 혼합연대모델(Finite Mixture Model)에 적용하면, 분석된 입자들 중 <TEX>$6{\pm}4%$</TEX>의 석영입자가 MIS 7의 퇴적시기 <TEX>$194{\pm}24ka$</TEX>)를 지시함을 알 수 있다. 결론적으로, 수렴단층 노두 해안단구 퇴적층이 MIS 7 시기에 형성되었을 가능성을 배제할 수 없으며, 이 퇴적층은 일반적으로 적용되는 다입자 OSL(multiple grain OSL) 연대측정법을 적용하기에 적합하지 않은 시료로 판단된다. In this paper, we report new OSL ages of the marine terrace sediments at Suryum fault site, using single grains of quartz, and briefly discuss their chronological implications on the timing of terrace formation along the southeastern coast of Korea. Of 1200 grains measured, 93 quartz grains were found to have OSL properties suitable for dating, the equivalent dose (<TEX>$D_e$</TEX>) values of which varied significantly, ranging from 50 Gy to 610 Gy with the overdispersion of <TEX>$30{\pm}4%$</TEX>. Applied to the Central Age Model (CAM) and Minimum Age Model (MAM), these quartz grains showed the OSL ages of <TEX>$83{\pm}4ka$</TEX> and <TEX>$60^{+3}{_{-7}}ka$</TEX>, respectively, both of which are stratigraphically inconsistent with the previously reported OSL ages of lower <TEX>$2^{nd}$</TEX> terrace (MIS 5a; ~80 ka). However, Finite Mixture Model (FMM) revealed that a small fraction of the measured quartz grains (<TEX>$6{\pm}4%$</TEX>) were of the ages (<TEX>$194{\pm}24ka$</TEX>) corresponding to MIS 7. Conclusively, based on single grain OSL ages, it would be prudent not to exclude the possibility that the marine terrace sediments at Suryum fault site have formed during MIS 7. Further, our single grain OSL ages imply that multiple grain(single aliquot) OSL dating methods are not applicable to the marine sediments at Suryum fault site.

OSL and radiocarbon dating of flood deposits and its paleoclimatic and archaeological implications in the Yihe River Basin, East China

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

Assessment of diagnostic tests for evaluating the reliability of SAR D e values from polymineral and quartz fine grains

This study explores the use of several different techniques to isolate and determine the age of lithic microdebitage in relation to archaeological deposits and associated sediments. Quartz microdebitage was identified on the basis of surface features and roundness index by applying scanning electron microscopy (SEM) and optical stereomicroscopy to archaeological sediments. Characteristics of the quartz microdebitage were compared with quartz grains from the same sedimentary layer. The observation of diagnostic features on quartz grains made it possible to discriminate between microdebitage and sedimentary background. Â This investigation has established that microdebitage particles under 500&microm diameter are not easily resolved under optical stereomicroscopy, requiring the aid of SEM to discern between microdebitage and sedimentary quartz. It was also ascertained that no adverse effects on the optically stimulated luminescence (OSL) signal are measurable after exposure to SEM, provided that the electron beam is kept at, or under, 10keV. Â Sedimentary material previously excavated from the Jinmium rockshelter (Northern Territory) and Mushroom Rock West (Queensland) was used to determine the age of quartz microdebitage from the archaeological layers by applying the OSL dating technique. The microdebitage OSL signal behaves similarly to that of sedimentary quartz grains, and is subject to the same problems. The OSL single-aliquot regenerative-dose protocol (SAR) was successfully applied to the age determination of microdebitage. The modifications used for the dose rate (due to particle size and shape) and for the calibration of the beta source (due to particle size) did not produce any inconsistencies or anomalous results. Â In the investigation of two archaeologically relevant sediment layers from the Jinmium rockshelter deposit, the minimum OSL age at 68cm for the microdebitage was estimated as 4100-900 years (12,600-4000 years using the central age model estimate, with 73% over-dispersion on the palaeodose), and, for the sedimentary material, a central age model of 5300-800 years (with a minimum age model estimate of 1900-400 years, and 78% over-dispersion). At 115cm in the deposit, the OSL central age model estimate for the microdebitage is 10,200-1100 years, with a minimum age model of 4500-600 years (and an over-dispersion of 56%). Â In the case study of Mushroom Rock West rockshelter, the OSL central age model estimate for microdebitage at 268cm is 21,200-3100 years (with a minimum age model estimate of 10,500-5200 years, and 60% over-dispersion), compared to a central age model estimate for the sedimentary quartz grains of 31,500-3100 years (with a minimum age model estimate of 11,100-1500 years, and 67% over-dispersion). At 441cm, the microdebitage yielded an OSL age of 27,400-2200 years. This sample of microdebitage produced the lowest over-dispersion (0.1%) on the palaeodose of any of the samples analysed, lending confidence to the accuracy of the palaeodose determination. The sedimentary quartz from the same sample produced an OSL minimum age model estimate of 33,500-5600 years (and a central age model estimate of 46,900-3400 years). Relationships between microdebitage and sediment OSL ages are discussed. Â Direct OSL dating of the unheated quartz derived from the manufacture of lithic tools now provides an alternative to the reliance on sedimentary quartz as the primary source information regarding the age of archaeological deposits. This knowledge may be applied also to archaeological sediments previously excavated, for identifying episodes of lithic manufacture in temporal relation to other evidence of cultural activity. The ages of the two archaeological sites analysed differ widely, and this difference was also represented in the ages obtained from the microdebitage. None of the OSL age determinations of microdebitage was found to be unrealistically outside the boundaries of pre-existing age control. This is one indication of the validity of the novel experimental approach applied.

古湖岸堤是湖面波动的地貌证据,可以用来重建古湖泊演化.古湖岸堤沉积物的准确测年是应用此地貌学证据重建湖泊演化的关键.以我国兴凯湖最低一级湖岸堤——大湖岗为研究对象,采用石英小片技术,应用单片再生剂量法(SAR)对大湖岗2个不同位置的剖面风成砂质沉积物(共13个样品)进行了光释光(OSL)测年.样品石英组分的光释光衰减曲线特征表明,样品的释光信号以快组分为主,预热坪和实验室剂量恢复实验结果表明,SAR法可以用来测量兴凯湖古湖岸堤样品的等效剂量.通过分析样品等效剂量分布情况和比较3种年龄模型(平均值模型、中值模型和最小值模型),认为大湖岗湖滨砂质沉积物在沉积埋藏前石英光释光信号晒退完全,获得的OSL年龄是可信的.年代结果表明,大湖岗采自不同位置的2个剖面的年代范围一致,且各个剖面中所有年代均随地层顺序变化;另外,2个样品的OSL年龄与同层位的炭屑样品的¹⁴C年代结果在误差范围内一致,进一步表明OSL测年技术可以获得可靠的兴凯湖岸堤沉积物的年龄.尽管与前人使用热释光(TL)测年方法研究大湖岗形成年代有较大差别,本文认为兴凯湖最低一级古湖岸堤——大湖岗形成于距今约1.24-0.50 ka.;Positions of lake shoreline ridges are indicative of the fluctuations in lake level and can be used for reconstruction of palaeolake evolution history. Reliable and accurate chronology is necessary for using lake shoreline ridge sediments to infer lake geomorphologic variations. This paper selected the Dahugang (DHG) shoreline ridge of Lake Xingkai (Northeast China) to demonstrate the potential of optically stimulated luminescence (OSL) dating technique in sandy shoreline sediments. Thirteen sedimentary samples were collected from two profiles (DHG1 and DHG2) of DHG shoreline ridge. Using single-aliquot regenerative dose (SAR) procedure, equivalent dose (D_e) of all samples was measured in small aliquot. The OSL signals of our samples decay very quickly, indicating that the OSL signal is dominated by fast component; preheat plateau tests and dose recovery tests were carried out to select suitable preheat temperature (220℃) for SAR procedure measurement. We analyzed the distributions of D_e for each sample, and compared the D_es derived from three models (Mean age model, Central age model, and Minimum age model). The results suggested that the sandy sediments from DHG shoreline ridge were well bleached prior to deposition and they are appropriate for OSL dating. The resultant OSL ages are stratigraphically ordered at each of the profiles of DHG1 and DHG2, and both have shown that the DHG shoreline was likely to be formed during~1.24-0.50 ka. Furthermore, the robustness and reliability of our OSL ages are validated by two ¹⁴C ages of charcoals. Although our results seem different from previous researches we propose that the DHG shoreline ridge in the Lake Xingkai was formed at around 1.24-0.50 ka based on the present OSL dating results.

When applying luminescence dating to sediment deposited in aquatic environments, a key issue for accurate age determination is resetting of acquired luminescence in sediment by surface exposure (bleaching) before burial. The time needed for bleaching is known to vary among the signals used in three methods: optically stimulated luminescence (OSL), infrared stimulated luminescence (IRSL), and post-infrared IRSL (pIRIR). A comparison of luminescence ages from these different signals is therefore useful to assess whether a sample was fully bleached before burial. In a comparison of OSL, IRSL50/225 and pIRIR225 ages of eight samples of fine-grained sediment from a 294-cm-long sediment core from Lake Yogo, a small-catchment lake in central Japan, the IRSL50/225 and pIRIR225 ages were much older than the OSL ages. The IRSL50/225 residual signals were close to zero, and the difference between pIRIR225 and OSL signals was much larger than the pIRIR225 residual signals. Thus, IRSL50/225 and pIRIR225 signals were not completely bleached, which we attribute to the short sediment transport distance in this small catchment. Five corrected bulk radiocarbon (14C) ages agreed with the OSL ages, except for two intervals in which OSL ages were about 500 and 1,900 years older than the corrected 14C ages. These discrepancies are attributable to incomplete bleaching related to sediment transport, whereas the rest of the OSL ages show no evidence of incomplete bleaching. This study shows that even in samples in which the pIRIR225 and IRSL50/225 signals are not well-bleached, OSL dating yields accurate age estimates because of the faster bleaching rate.

Inter-comparison of optically stimulated luminescence (OSL) ages between different fractions of Holocene deposits from the Yangtze delta and its environmental implications

Quartz OSL and TL dating of pottery, burnt clay, and sediment from Beicun archaeological site, China

Optically stimulated luminescence (OSL) dating is an important method for determining the ages of late Quaternary sediments. However, partial bleaching of quartz in fluvial sediments remains a challenge, with debates on grain-size effects in different sedimentary environments. The aim of this paper is to explore the bleaching degree and its influencing factors of different grain-size quartz in fluvial sediments from the Yanchi section in the Daluze area, North China Plain. According to sedimentological methods and grain size analysis, lacustrine and fluvial layers were identified, and the ages of sediments were determined by OSL and 14C methods. The key findings are as follows: (1) Fine-grained quartz can be better bleached than coarse/medium-grained quartz for early–middle Holocene fluvial sediments. (2) The OSL method can yield reliable ages for early–middle Holocene fluvial sediments, while it overestimates these for late Holocene fluvial sediments. This probably results from variations in sediment sources and hydrodynamic conditions. (3) The dating results show that there are three fluvial activity periods in the Daluze area: 10.8~10.2 ka, 5.3~4.7 ka, and after 1 ka. This paper provides a reliable chronological framework for the evolution of regional sedimentary environments and offers references for luminescence dating of fluvial sediments in similar environments.