post-IR Infrared Stimulated Luminescence Research Articles

Technical note: Darkroom lighting for luminescence dating laboratory

Abstract. An optimal lighting setting for the darkroom laboratory is fundamental for the accuracy of luminescence dating results. Here, we present the lighting setting implemented in the new Luminescence Dating Research Laboratory at Stony Brook University, USA. In this study, we performed spectral measurements on different light sources and filters. Then, we measured the optically stimulated luminescence (OSL) signal of quartz and the infrared stimulated luminescence (IRSL) at 50 ∘C (IR50) as well as post-IR IRSL at 290 ∘C (pIR-IR290) signal of potassium (K)-rich feldspar samples exposed to various light sources and durations. Our ambient lighting is provided by ceiling fixtures, each equipped with a single orange light-emitted diode (LED). In addition, our task-oriented lighting, mounted below each wall-mounted cabinet and inside the fume hoods, is equipped with a dimmable orange LED stripline. The ambient lighting, delivering 0.4 lx at the sample position, induced a loss of less than 5 % (on average) in the quartz OSL dose after 24 h of exposure and up to 5 % (on average) in the IR50 dose for the K-rich feldspar samples, with no measurable effect on their pIR-IR290 dose. The fume hood lighting, delivering 1.1 lx at the sample position, induced a dose loss of less than 5 % in quartz OSL and K-rich feldspar IR50 doses after 24 h of exposure, with no measurable effect on their pIR-IR290 dose. As light exposure during sample preparation is usually less than 24 h, we conclude that our lighting setting is suitable for luminescence dating darkrooms; it is simple, inexpensive to build, and durable.

Multi-method study of the Middle Pleistocene loess–palaeosol sequence of Köndringen, SW Germany

Abstract. Loess–palaeosol sequences (LPSs) remain poorly investigated in the southern part of the Upper Rhine Graben but represent an important element to understand the environmental context controlling sediment dynamics in the area. A multi-method approach applied to the LPS at Köndringen reveals that its formation occurred during several glacial–interglacial cycles. Field observations, as well as colour, grain size, magnetic susceptibility, organic carbon, and carbonate content measured in three profiles at 5 cm resolution, provide detailed stratigraphical information. Only minor parts of the LPS are made up of loess sediment, whereas the major parts are polygenetic palaeosols and pedosediments of varying development that are partly intersected, testifying to a complex local geomorphic evolution. The geochronological framework is based on 10 cm resolution infrared-stimulated luminescence (IRSL) screening combined with 18 multi-elevated-temperature post-IR IRSL ages. The luminescence ages indicate that two polygenetic, truncated Luvisols formed during marine isotope stages (MISs) 9(–7?) and MIS 5e, whereas unaltered loess units correspond to the last glacial (MISs 5d–2) and MIS 8. The channel-like structure containing the two truncated Luvisols cuts into > 2 m thick pedosediments apparently deposited during MIS 12. At the bottom of the LPS, a horizon with massive carbonate concretions (loess dolls) occurs, which may correspond to at least one older interglacial.

The bleaching limits of IRSL signals at various stimulation temperatures and their potential inference of the pre-burial light exposure duration

Infrared Stimulated Luminescence (IRSL) techniques are being increasingly used for dating sedimentary feldspars in the middle to late Quaternary. By employing several subsequent stimulations at increasing temperatures, a series of post-IR IRSL (pIRIR) signals with different characteristics (stability and bleachability) can be obtained for an individual sample. It has been experimentally demonstrated that higher-temperature pIRIR signals are more stable, but they tend to exhibit larger residual doses up to few tens of Gy, potentially causing severe age overestimation in young samples. In this study we conducted comprehensive bleaching experiments of IRSL and pIRIR signals using a loess sample from China, and demonstrated that non-bleachable components in the IR (and possibly pIRIR) signals do exist. The level of such non-bleachable signal shows clearly positive correlation with preheat/stimulation temperature, which further supports the notion that lower temperature pIRIR are advantageous to date young samples and sediments especially from difficult-to-bleach environments. These results display a potential in constrain the pre-burial light exposure history of sediment utilizing multiple feldspar post-IR IRSL (pIRIR) signals. For the studied loess sample, we infer that prior to its last burial, the sample has received an equivalent of >264 h exposure to the SOL2 simulator (more than 2,000 h of natural daylight).

Coarse-grained K-rich feldspar and fine-grained polymineral IRSL dating of loess-palaeosol from the Chinese Loess Plateau: A comparison

In this study, the characteristics of infrared stimulated luminescence (IRSL) signals from coarse-grained (63–100 μm, CG) K-feldspar and fine-grained (4–11 μm, FG) polymineral fractions was compared using the Chinese loess/palaeosol samples from the Luochuan profile. The pIRIR 50, 225 and pIRIR 200, 290 protocols (pIRIR: post-IR IRSL. The subscript shows stimulation temperatures for the IR and pIRIR signals) were used. Natural signal intensities of eleven samples were used to construct the natural dose-response curve (DRC) for each signal. The laboratory and simulated-natural DRCs for each signal from the CG K-feldspar and FG polymineral fractions were constructed and were compared with the natural DRC. The natural DRCs were broadly consistent for the two pIRIR and the IR 200 signals for both fractions. The characteristic saturation dose ( D 0 ) of the natural DRCs for the pIRIR signals from the CG K-feldspar tended to be smaller than those from the FG polymineral fraction. Conversely, the D 0 s of the laboratory DRCs for all the signals from the CG K-feldspar were larger than those from the FG polymineral fraction. The ratio of simulated-natural DRC over natural DRC (N sim /N) was able to successfully determine the fading over- or under-correction tendencies for different signals and dose regions.

Testing the accuracy of OSL and pIR IRSL dating of young geoarchaeological sediments in coastal Peru

Luminescence dating of late Quaternary sediments in Peru is challenging, especially on the Peruvian coast. Earlier studies have shown that quartz grains often exhibit a thermally unstable, medium signal that caused the underestimation of Optically Stimulated Luminescence (OSL) ages. InfraRed Stimulated Luminescence (IRSL) dating has shown to produce more reliable ages, depending, amongst other factors, on the age model (Central or Minimum Age Model), and the IRSL signal. IRSL dating of geoarchaeological sediments has, however, hardly been carried out, let along validated, against an independent age dataset. This dating approach is, nonetheless, the only promising way to date the geological substrate in which many of Peru's archaeological sites are buried. Peru contains some of the oldest and most important archaeological heritage sites, yet not much is known of the environmental context in which many of its early civilizations prospered. A better understanding of which luminescence method works best could therefore help in a better understanding of the geological-stratigraphical context of many of Peru's sites. To investigate this matter more fully, we compared the luminescence dating results of seven sediment samples from the top layer of the Lima alluvial fan and from geoarchaeological layers of the Maranga Complex (San Miguel, Lima), with an independent dataset of sixteen 14 C ages. Our results showed that the quartz OSL ages always underestimated the expected ages due to a signal dominated by medium and slow components, and that the post-IR IRSL 225 (pIR IRSL 225 ) and IRSL 50 ages of K-feldspars, on basis of the Central Age Model (CAM), always overestimated the expected ages. The Minimum Age Model (MAM) on the other hand, correctly predicted the expected ages for the early Holocene, Lima alluvial fan sediments using the pIR IRSL 225 signal of K-feldspars, and the late Holocene, geoarchaeological ages using the IRSL 50 signal.

Luminescence dating of Holocene sediment cores from a wave-dominated and mountainous river delta in central Vietnam

Sediments of river deltas provide valuable records of past coastal environments. Optically-stimulated luminescence (OSL) dating has become an alternative to radiocarbon dating for constraining the sediment chronology in large deltas that allow for sufficient sunlight bleaching of sediments during the fluvial transport. However, its applicability to smaller deltas with mountainous riverine systems has not been confirmed yet. To check this, we examine multiple signals from two Holocene sediment cores in the wave-dominated Thu Bon River delta in central Vietnam. Two cores were collected, respectively, 3.9 km and 1.2 km inland from the present shoreline and both show a >-25-m thick succession of coarsening-upward mud to sand deposits. Coarse grains (180–250 μm in diameter) of quartz and K-feldspar, and fine grains (4–11 μm in diameter) of quartz and polymineral were extracted from the upper and lower parts of the cores for multi-grain measurements of quartz OSL, and of feldspar infrared-stimulated luminescence (IRSL) at 50 °C (IR50) and post-IR IRSL at 175 °C (pIRIR175) to determine burial ages. In addition, facies analysis and radiocarbon dating were conducted. The landward core consists of transgressive to early regressive estuarine and prodelta facies, which is overlain by a sandy beach-shoreface facies. The seaward core consists of a relatively simple shallowing-upward succession from muddy prodelta facies to sandy beach-shoreface facies. All luminescence ages except for pIRIR175 of fine grains are mostly consistent with the radiocarbon ages. Instead, pIRIR175 ages of fine grains are significantly overestimated with variable offsets. OSL and IR50 of fine grains provide reasonable age estimates, as these grains were likely well bleached during the transport even along a short and steep mountainous river. Consistent age estimates of all signals from sand indicate that sand was well-bleached in the beach and shoreface owing to the frequent sediment reworking by waves and currents. These results support the hypothesis that luminescence dating is applicable to Holocene wave-dominated deltas and reiterate that comparing different luminescence signals is an effective way to check reliability of the age estimates in environments where the sunlight bleaching is not ensured.

Luminescence dating reveals a rapid response to climate change of fluvial terrace formation along the Ani River, northeastern Japan, during the last glacial period

Fluvial terraces along the middle reaches of many Japanese rivers were formed during the last glacial period as a result of changes in sediment discharge related to cooler temperatures and/or reduced water discharge because of lower precipitation. The influence of climate change on these fluvial terraces is not yet fully understood because most previous studies lacked detailed reconstructions of the chronology of terrace development. This study provides a detailed luminescence chronology of fluvial terrace deposits along the Ani River, northeastern Honshu, Japan, and compares that chronology to paleoclimatic records. Eight samples for luminescence dating were obtained from an outcrop of terrace deposits (∼10 m thick) in the Ani River valley. The fading-corrected infrared stimulated luminescence (IRSL) ages are consistent with the fading-corrected post-IR IRSL ages for some samples, which suggests that fading corrections were effective despite the higher fading rates of the IRSL signal. However, for the other samples, the post-IR IRSL ages are significantly older than the fading-corrected IRSL ages due to incomplete bleaching. The pulsed IRSL signals are close to field saturation for older samples, which might have resulted in a greater variation of the ages. Fading-corrected IRSL ages demonstrate periods of rapid aggradation during 105–90 ka and 75–60 ka. Comparison of terrace development with paleoclimatic records indicates that the two periods of fluvial deposition correspond to decreases in precipitation caused by weakened East Asian summer monsoon precipitation and possibly decreases in temperature. The results of this study show that the Ani River responded rapidly to climate change on a time scale of a few tens of thousands of years during the last glacial period.

Luminescence dating of cobbles from Pleistocene fluvial terrace deposits of the Ara River, Japan

Constraining the ages of fluvial terraces is essential to understanding fluvial responses to climate and sea-level changes and estimating uplift/incision. Luminescence dating of sand or silt grains from fluvial terrace deposits in Japan is difficult because sand layers are often absent from gravelly deposits, quartz grains are typically dominated by medium/slow components and/or contaminated by feldspars, and short transport distances and short residence times in riverbeds result in poor bleaching of luminescence signals. Luminescence dating of cobbles may overcome these difficulties, but few studies have applied this technique to fluvial terrace deposits. Here, we examine the utility of luminescence dating applied to three granodiorite cobbles from a late Pleistocene fluvial terrace deposit of the Ara River, Japan. We investigated variations of the infrared stimulated luminescence (IRSL) and post-IR IRSL signals with depth in each cobble. The IRSL and post-IR IRSL signals generally increase with depth, indicating that the cobbles were not completely bleached before deposition. Nonetheless, the IRSL ages of the cobble surfaces (19–17 ka) are consistent with the age of a tephra layer (16–15 ka) at the base of loess deposits overlying the terrace. In contrast, IRSL ages of sand-sized feldspar grains overestimate the depositional age because of incomplete bleaching, whereas silt-sized quartz grains greatly underestimate the depositional age, likely because of the thermal instability of the medium component. Our results demonstrate that luminescence dating of cobbles could provide a better understanding of fluvial systems in which luminescence dating of sand grains is difficult.

Residual Dose of K-Feldspar post-IR Irsl of Beach-Shoreface Sands at Kujukuri, Eastern Japan

Abstract We assessed the residual dose of K-feldspar grains from modern and Holocene beach–shoreface sands at Kujukuri, eastern Japan. Samples from the modern foreshore and shoreface (to 34 m depth) show residual doses <0.2 Gy for infrared-stimulated luminescence (IR)50 measured during post-IR infrared-stimulated luminescence (pIRIR)50/150, equivalent to potential burial age overestimation of only several decades for given dose rates. Residual doses of 1–3 Gy are retained by pIRIR50/150, equivalent to 400–1,300 years; pIRIR50/290 residual doses are up to 30 Gy, suggesting possible overestimation by >10,000 years. Residual doses of Holocene sands were also assessed by comparison with radiocarbon ages, revealing consistent results with modern sands. The pIRIR50/290 results show no pronounced correlation of residual dose with water depth, except for a few samples from <5 m depth with residual doses several tens of per cent lower than those of deeper sands, suggesting that most samples were not fully bleached and that sustained subaerial sunlight bleaching diminishes the difficult-to-bleach component. Compared to the uncertainties associated with other factors, such as the fading correction, the residual doses of IR50 and pIRIR50/150 are negligible for samples older than late and early Holocene, respectively. In contrast, the residual dose of pIRIR50/290 may lead to critical age overestimation of Late Pleistocene deposits if the residual dose is not properly corrected.

Exploring the use of a low temperature preheat in IRSL dating of feldspar in Beringian archaeological contexts

A new luminescence dating protocol was developed to circumvent the problem of thermal transfer and poor thermal stability of Infrared Stimulated Luminescence (IRSL) of samples from late glacial loess sediments in Central Alaska, USA. This new protocol is proposed as an alternative to routine procedures for which scattered and erratic results were obtained using standard IRSL and post-IR IRSL protocols on loess samples from the McDonald Creek archaeological site.The difficulty to date Alaskan loess has been acknowledged in the past, but the reasons for this phenomenon have not been clearly identified. This difficulty is even greater for young samples, as shown in this study. It is suggested here that the particular mineralogical composition of the Central Alaskan loess can be related to problematic luminescence behaviour.To overcome problematic results, we developed a Low Preheat IRSL (LPH-IRSL) protocol. This protocol is minimally affected by the presence of other minerals than K-feldspars in the samples, such as albite, muscovite and clinochlorite, which can be very difficult to eliminate during the preparation steps prior to IRSL measurements. Dose recovery experiments and multiple other tests indicate that a protocol with low preheat temperature yields the best results in this specific context. Thermally transferred luminescence induced during the measurement is kept at a minimal level. Consequently, considering independent age controls available from radiocarbon, equivalent doses are successfully determined, their distribution is narrow, and the g-value has low scatter. This protocol has great potential for dating polymineral samples, whether it is silt-sized sediments like loess, fine-grained like clay and micro-samples like art pieces, common in archaeological contexts.The chronological results obtained for this project suggest a human occupation of the area during the Late Pleistocene to mid-Holocene period, which is in excellent agreement with preliminary radiocarbon chronology obtained during site testing and also with the regional archaeological framework.

Review of the Post-IR IRSL Dating Protocols of K-Feldspar.

Compared to quartz, the infrared stimulated luminescence (IRSL) of K-feldspar saturates at higher dose, which has great potential for extending the dating limit. However, dating applications with K-feldspar has been hampered due to anomalous fading of the IRSL signal. The post-IR IRSL (pIRIR) signal of K-feldspar stimulated at a higher temperature after a prior low-temperature IR stimulation has significantly lower fading rate. Different dating protocols have been proposed with the pIRIR signals and successful dating applications have been made. In this study, we review the development of various pIRIR dating protocols, and compare their performance in estimating the equivalent dose (De). Standard growth curves (SGCs) of the pIRIR signals of K-feldspar are introduced. Single-grain K-feldspar pIRIR dating is presented and the existing problems are discussed.

Luminescence dating of sediments from central Atacama Desert, northern Chile

Abstract This study examines the feasibility of applying luminescence dating methods to quartz and potassium feldspar (K-feldspar) grains from Quaternary continental deposits of the Mejillones Peninsula and Coastal Cordillera in Central Atacama, northern Chile. Sediment burial ages were calculated using single-aliquot regenerative-dose (SAR) protocols applied to the optically stimulated luminescence (OSL) signal of quartz as well as infrared stimulated luminescence (IRSL) and post-infrared infrared stimulated luminescence (post-IR IRSL) signals of K-feldspar. Considering that the target sedimentary deposits comprise the Late Pleistocene age range, K-feldspar grains were dated using fading-corrected IRSL signals measured at 50 °C (IR50) and post-IR IRSL measured at 225 °C (pIRIR225) to minimize the potential effect of residual doses on calculated ages. The results of the analytical procedures indicate that quartz grains extracted from the studied sediments present a very weak or even no fast OSL component. The combination of a low OSL sensitivity, signal instability and equivalent dose distributions with high overdispersion (>40% for most samples) hinder reliable age estimation using quartz aliquots. Bleaching test results show that the IR50 signal from K-feldspar aliquots is well reset after 20–24 h of light exposure, while the pIRIR225 signal may present residual doses corresponding to between 10 and 15% of the natural signal. IR50 fading rates are ∼6–7%/decade for most studied samples, with exception of one sample which yielded a g-value of 18.77 ± 2.06%/decade. Fading rates for the pIRIR225 signal yielded variable results among sampling sites, with g-values ranging between 0.70 ± 0.24 and 6.77 ± 1.05%/decade. The dating results point out that quartz OSL ages are largely underestimated in relation to K-feldspar fading-corrected IR50 and pIRIR225 ages. Fading-corrected pIRIR225 K-feldspar ages indicate that the alluvial sedimentation in the downthrown block of an active normal fault in Mejillones Peninsula occurred between 163.4 ± 18.4 ka and 87.4 ± 6.6 ka. K-feldspar ages also allow to constrain the age of fault scarp degradation and fault reactivation in two main branches of the Atacama Fault System. In the Naguayan Fault, pIRIR225 ages indicate that faulting occurred after 21.4 ± 3.2 ka while in the Salar del Carmen Fault, faulting is recorded after 14.7 ± 1.0 ka.

Methodological studies on integration time interval's selection for the luminescence ages using quartz and feldspar minerals; sediments collected from Sakarya, Turkey

In this study, two different equivalent dose protocols using Infrared stimulated luminescence (IRSL), namely post IR (pIRIR) and Multi-Elevated temperature post IRSL (MET-pIRIR) were applied to geological samples collected from terrace staircases formed along the Sakarya River, western Anatolia, Eastern Marmara Region, Turkey. Methodological aspects were studied, as the IRSL signal, which is measured at elevated temperatures, yields unusual shape, consisting of an initial increasing part which is followed by the well-known decaying shape. Therefore, according to signal shape, instead of de-convolving the IRSL signals, equivalent dose estimations were performed using different time integration intervals of the emission. The results constitute of two groups, yielding equivalent dose values, in the range between 55 and 110 Gy for selected samples. Since de-convolution of the IRSL signals is both time consuming as well as difficult, mostly due to the presence of tunneling localized transitions, the selection of the appropriate/optimum time integration interval was discussed. The outcomes of this study indicate that IR stimulations at higher temperatures ranging from 200 to 250 °C are useful for feldspar dating, providing that initial increasing part will be eliminated. The thermal activation energy of that unusual part of the signal was calculated around 0.035 ± 0.005 eV using Arrhenius plot, indicating that it may arise from phonon lattice interactions.

Constraining the timing of palaeosol development in Iranian arid environments using OSL dating

Abstract The ages of palaeosols in arid environments in Iran are constrained using the optically stimulated luminescence (OSL) signal from quartz. The luminescence properties of quartz OSL and K-feldspar infrared stimulated luminescence (IRSL) at 50 °C (IR50) and post-IR IRSL at 290 °C (pIRIR290) signals are compared to investigate the degree of bleaching of quartz OSL in individual samples at the time of deposition. A comparison between the quartz OSL and K-feldspar IR50 ages shows that 12 out of 15 samples were probably well-bleached prior to deposition. The 17 OSL ages constrain at least four broad phases of sediment deposition and soil formation on the central Iranian plateau: (i) prior to, and (ii) during, mid/late MIS 5 (at Isfahan and Lar), (iii) MIS 3 (at Bam, Mahan and probably Isfahan) and (iv) MIS 1 (at Rayen and Jiroft). In summary, there is no convincing evidence for palaeosol formation during MIS 4 and MIS 2; however pedogenesis does appear to have taken place during all other marine isotope stages over the last full glacial-interglacial cycle.

Post-IR IRSL dating of K-feldspar from last interglacial marine terrace deposits on the Kamikita coastal plain, northeastern Japan

To establish a suitable luminescence dating protocol for marine terrace deposits in Japan, we tested the applicability of K-feldspar post-infrared (IR) infrared stimulated luminescence (IRSL) (pIRIR) dating using a marine isotope stage (MIS) 5e terrace deposit from the Kamikita coastal plain (NE Japan), where independent age control from a tephra is available. One of the most commonly used pIRIR signals, measured at 290°C with the first IR stimulation temperature at 50°C (pIRIR<sub>50/290</sub>), faded with a mean g<sub>2days</sub> value of 1.94 ± 0.19%/decade. In contrast, the pIRIR signal with a higher first IR stimulation temperature of 200°C (pIRIR<sub>200/290</sub>) had a much lower fading rate (g<sub>2days</sub> = 0.16 ± 0.49%/decade). The average fading-uncorrected and -corrected pIRIR<sub>200/290</sub> ages of MIS 5e subtidal sediments obtained from two sampling sites were 126 ± 3 ka and 132 ± 2 ka, which is in good agreement with the independent age control. We conclude that is it is now possible to use pIRIR protocol to estimate the ages of not only marine terraces formed during MIS 5 substages (5a, 5c) but also of older marine terraces, for which age evidence is limited.

Quartz and K-feldspar luminescence dating of sedimentation in the North Bohai coastal area (NE China) since the late pleistocene

In this study, luminescence dating of core sediments from the North Bohai Coast (China) was applied to provide a high-resolution chronological constraint, on a better understanding of the Holocene marine-terrestrial interaction. The studied sedimentary sequence contains a terrigenous deposit, a transgressive deposit and a prograding deltaic succession; all are believed to have formed during the late Pleistocene. To establish a reliable luminescence chronology, the luminescence signals of ten samples were investigated in order to quantify the degree of bleaching. This approach involved the use of quartz OSL, K-feldspar infrared stimulated luminescence (IRSL) and post-IR IRSL (pIRIR) ages. The resulting data were then compared with radiocarbon ages. The quartz OSL signals were well-bleached for all the samples, and the feldspar pIRIR150 and pIRIR225 signals yielded reliable ages for the pre-Holocene deposits but overestimated ages for late Holocene deposits (<1000 years). Radiocarbon data appeared to slightly overestimate the age of the young Holocene samples, therefore the chronological framework was established using quartz OSL ages. The early-mid Holocene transgressive deposits are relatively thin, which was attributed to the low-gradient relief and weak riverine fluvial input. Rapid deltaic progradation with high sedimentation rates over the last millennia, was revealed by the quartz OSL age results. This was supported by historical records for this section of the coastline. Episodic deposition around 700 years ago most likely triggered by frequent flooding events, was highlighted by the clustered OSL ages. While the sediment increment was 2.7 × 104 m3 a−1 for the period of ∼6–1 ka, this increased considerably to 9.1 × 106 m3 a−1 during the rapid progradation of the last millennium. The increase appears related to winter monsoon enhancement and human activity during the last 1000 years.

Quartz OSL and K-feldspar post-IR IRSL dating of sand accumulation in the Lower Liao Plain (Liaoning, NE China)

The timing of the formation of extensively distributed sand dunes in the Bohai coastal area and its forcing factors are poorly understood. In this study, the chronology of a well-preserved sand dune located in Panjin Forest Park (PJ) in the Lower Liao Plain (LLP) is investigated using quartz optically stimulated luminescence (OSL) and K-feldspar postinfrared (IR) infrared stimulated luminescence (IRSL) (pIRIR) dating. For the pIRIR measurements, the combination of preheating at 180°C and pIRIR stimulation at 150°C (pIRIR&lt;sub&gt;150&lt;/sub&gt;) is exploited. The quartz results show that the sand dune accumulated from &lt;i&gt;c&lt;/i&gt;. 120 a (1890 AD) to c. 70 a (1940 AD) before present, and the underlying sandy soil sediments deposited from &lt;i&gt;c&lt;/i&gt;. 5.0 ka to &lt;i&gt;c&lt;/i&gt;. 0.13 ka as marsh sediment after the sea level highstand since the mid-Holocene. From the evidence in historical coastline records, the PJ sand dune is an inland sand dune and not a coastal sand dune. Based on further information of climate and temperature change after the Little Ice Age (LIA) and human activity in northeastern China, we conclude that the PJ sand dune accumulation was very likely impacted by the immigrants and land reclamation at the end of Qing dynasty. The fading corrected IR&lt;sub&gt;50&lt;/sub&gt; ages, the apparent and fading corrected pIRIR&lt;sub&gt;150&lt;/sub&gt; ages are consistent with quartz ages for two sandy soil samples but overestimate those for six sand samples. The overestimation of the feldspar ages is derived from the residual signal which has not been bleached before burial. The offset obtained from the difference between the quartz OSL and the feldspar pIRIR&lt;sub&gt;150&lt;/sub&gt; ages are ~20–160 a (predicted residual dose: ~0.08–0.60 Gy), whereas the measured residual dose after bleaching 4 h in a solar simulator yielded age overestimation of ~10–40 a (~0.05–0.16 Gy). The age discrepancy calculated from the predicted residual was larger than those obtained from the laboratory measured residuals. We conclude that the pIRIR&lt;sub&gt;150&lt;/sub&gt; of aeolian sediment is applicable for samples older than ~1000 years where the effect of the residual dose become negligible.

New luminescence dating results based on polymineral fine grains from the Middle and Upper Palaeolithic site of La Ferrassie (Dordogne, SW France)

Abstract In this study we compare different infrared stimulated luminescence (IRSL) signals for dating archaeological deposits. The IRSL and the more recently developed post-IR IRSL (pIR-IR) methods were investigated using polymineral fine grains extracted from the Middle and Upper Palaeolithic western excavation area in the site of La Ferrassie (Dordogne, SW France). The IRSL data measured at 50 °C (IR 50 ) are compared to those obtained with the elevated pIR-IR signals measured for two stimulation temperatures, 225 °C (pIR-IR 225 ) and 290 °C (pIR-IR 290 ). The signals are documented in terms of bleaching and fading rates. In addition, comparisons of the IR 50 ages corrected either with the H + L method (Huntley and Lamothe, 2001) or with the dose rate correction method (DRC, Lamothe et al. , 2003) are presented. Results show that the polymineral fine grains give a reasonable estimate of the burial age of the samples. The IR 50 and pIR-IR 225 provide the most reliable ages when they are corrected using the DRC method (because of saturation effects). The polymineral ages are then compared with the previously obtained ages on K-feldspar coarse grains, quartz OSL (Guerin et al. , 2015) and radiocarbon ages with the aim of accessing information on the depositional processes. It appears that further comparison of polymineral fine grains to coarse grains is beneficial to evaluate bleaching. Moreover, the polymineral results either confirm or refine the chronology of the La Ferrassie sequence proposed by Guerin et al. (2015), that is, the Mousterian layers range from marine isotope stage (MIS) 5 to the middle of MIS 3. In particular, i) the base of Layer 3 is pushed back to the end of MIS 4 or beginning MIS 3 and ii) the chronological attribution of Layers 4 and 5 is confirmed as MIS 3. Finally, the chronology of the Aurignacian layer (Layer 7) is strengthened by all the feldspars results.

Luminescence dating of interglacial coastal depositional systems: Recent developments and future avenues of research

Luminescence dating offers new opportunities to explore the evolution of Quaternary marine coastal facies and landforms. This review highlights the main advances in luminescence geochronology of interglacial coastal sediments through the analysis of 547 luminescence ages, most of which were published during the last decade. The majority of these reported luminescence investigations have been carried out along passive margin coasts. Since the turn of the century, the discovery of a normalization procedure known as Single Aliquot Regeneration (SAR) has drastically reduced data scatter and improved precision, with the consequence that quartz SAR optically-stimulated luminescence OSL has become the dating protocol of choice for the Last Interglacial (LIG) period. A more complex technique, known as thermally-transferred OSL (TT-OSL), is presumably proposed for dating older interglacials of the Mid-Pleistocene and beyond. Feldspar luminescence is increasingly being applied to dating Pleistocene sea level high stands due to a much higher dose saturation level than quartz OSL. The use of feldspar IRSL (Infrared-stimulated luminescence) is limited by the occurrence of variable, but ubiquitous anomalous fading (AF). Following the advent of AF-correction methods, several Middle Pleistocene sites have been amenable to dating, albeit with significant related uncertainties. Recently, new protocols involving the measurement of post-IR IRSL at elevated temperatures have yielded relatively coherent ages for interglacial sediments up to ca. 300 ka. Quartz OSL/TT-OSL, AF-corrected IRSL, and post-IR IRSL ages are generally correlated with periods of sea level high stands. A few ages are reported from the early and middle part of the Middle Pleistocene, as MIS11, 9 and more commonly MIS7 high stands are documented in strongly uplifting active margin coasts. However, by far the most obvious age peak corresponds to the end of the LIG. The MIS5e shoreline is probably the most studied and luminescence-dated coastal feature of all, as the chronology of the sea level markers is crucial to assess global eustatic sea level variations through the course of the last interglacial. Nevertheless, the observed abundance of young (100–120 ka) luminescence ages for presumed MIS5e sediments may underline methodological issues, and/or reflect the higher preservation potential of late regressive sequences. On the other hand, the occurrence of geographically distant reports of MIS5a high stand might reflect a true eustatic origin for this event. Age analysis supports the impression of general reliability of luminescence for the timing of former sea level high stands. There is a clear need to address issues in dose rate variability, in the phenomenology of fading in feldspar, and in the behaviour of luminescence growth with dose, both in laboratory and natural conditions. These could be addressed and properly evaluated by dating different minerals, as multiple or single grains, with consequent variable internal dose rates. More robust practices in the application of luminescence dating techniques could eventually constrain the age uncertainties to no better than 2–3%. Therefore, the strength of luminescence as a dating tool is more in terms of its extended age range and the ubiquity of datable material.

Thermoluminescence signal in K-feldspar grains: Revisited

Recent work has shown that infrared stimulated luminescence (IRSL) signals in sedimentary coarse-grain K-feldspars are derived mainly from high temperature thermoluminescence (TL) peaks around 400°C, and the fading components of the IRSL signal can be preferentially removed by prior IR stimulation at relatively low temperature. Considering the complexity of TL signal for very old samples, we may choose non-fading components from K-feldspar TL signals using the combination of optical and thermal activation methods. This paper examines a protocol of post-IR isothermal TL (i.e. pIRITL) signal for sedimentary coarse-grain K-feldspars, which results from isothermal TL measurements following elevated temperature IR bleaching. We show that a sum of two exponential decay functions can fit well to the pIRITL decay curves, and both the holding temperature for isothermal TL measurements and the prior elevated temperature IR bleaching can affect greatly the fast components of pIRITL signal. The dose response ranges of pIRITL signal are wider than those of post-IR IRSL signals, but the relative high residual pIRITL signal means that it is not appropriate for dating young samples. It is expected that one isothermal TL signal for K-feldspar measured at ~400°C following IR bleaching at 290°C (i.e. pIRITL400) is useful for dating very old samples.