A robust feldspar luminescence dating method for Middle and Late Pleistocene sediments

Luminescence dating is used extensively to provide absolute chronologies for Late Pleistocene sediments. Nowadays, most optical dates are based on quartz optically stimulated luminescence (OSL). However, the application of this signal is usually limited to the last ～100 ka because of saturation of the quartz luminescence signal with dose. In contrast, the feldspar infrared stimulated luminescence (IRSL) dose–response curve grows to much higher doses; this has the potential to extend the datable age range by a factor of 4–5 compared with quartz OSL. However, it has been known for several decades that this IRSL signal is unstable, and this instability often gives rise to significant age underestimation. Here we test against independent age control the recently developed feldspar post‐IR IRSL approach to the dating of sediments, which appears to avoid signal instability. A physical model explaining our observations is discussed, and the method is shown to be accurate back to 600 ka. The post‐IR IRSL signal is reduced by exposure to daylight more slowly than that from quartz and low‐temperature IRSL, preventing its general application to young (e.g. Holocene) sediments. Nevertheless, this new approach is widely applicable (feldspar of appropriate luminescence behaviour is even more ubiquitous than quartz). These characteristics make this a method of great importance for the dating of Middle and Late Pleistocene deposits.     

甘肃玉门地区第四纪晚期构造阶地的红外释光测年

光释光（ＯＳＬ）测年是近几年从热释光（ＴＬ）测年基础工起来的测定第四纪沉积物年龄的一种新技术，其原理与ＴＬ测年类似。不同的是：ＯＳＬ是单色光束激发品体中储存的电离辐射能使其以光的形式释放出来。当用近红外线束作为激光光源时称之为红外释光测年。与ＴＬ测年相比，ＩＳＬ测年可以不考虑残留的ＯＳＬ信号，而且测量具有简便，迅速且准确等优点。本文用细颗粒红外释放技术对玉门地区的构造阶地进行了年龄测定，初步结果表     

Optically stimulated luminescence dating of fluvial deposits: a review

Optically Stimulated Luminescence (OSL) dating allows age determination of sediments deposited during the last glacial-interglacial cycle. This relatively new technique therefore enables chronological frameworks to be established for fluvial deposits that often cannot be dated by other means. The OSL signal of quartz and feldspar minerals is reset by light exposure during fluvial transport, and builds up as a result of ionizing radiation after burial of the minerals. Incomplete resetting of the OSL signal because of inadequate light exposure in the fluvial environment can result in age overestimations, especially for relatively young samples. Methods used for the detection of incomplete resetting, or poor bleaching, are reviewed. It is argued that technique s measuring the OSL signal from small subsamples (aliquots) are most promising for detecting poor bleaching and for obtaining the true age for a sample in which not all grains had their OSL signal completely removed at deposition. Quartz should be the mineral of choice, because it has been shown to yield the most reliable results and because its OSL signal is more rapidly reset than that of feldspar. Aliquot size should be small, with aliquots ideally consisting of a single grain of quartz for samples in which the majority of grains are poorly bleached. Using single-aliquot dating of coarse-grain quartz, age offsets between zero and a few thousand years have been found for modern fluvial deposits. The validity of single-aliquot quartz OSL dating has been demonstrated by application to known-age samples, but for the older age range (>˜13 ka) further proof of the accuracy of the method is essential. The application of quartz OSL dating to investigations of fluvial deposits opens a new realm of possibilities to be explored, as is highlighted by some examples of geological applications.     

旧石器遗址强烈化学风化沉积物细粒混合矿物的光释光信号特征及其测年应用

从湖南省北部赤山岛枫树嘴旧石器遗址剖面第2、第3和第4考古层位采集的3个沉积物样品中提取的细粒混合矿物,尝试对其红外释光(IRSL)信号进行研究。实验表明,虽然长石IRSL信号很弱,但仍可以测得信噪比足够高的红外激发后高温红外激发释光(post-IR IRSL)信号。与此同时,样品存在明显的红外激发后蓝光释光(post-IR OSL)信号,并且样品的IRSL与post-IR OSL信号均以快组分为主,这为该地区沉积物利用长石光释光信号定年提供了新的可能。鉴于长石IRSL信号较弱,根据剂量恢复实验结果,本研究采用post-IR IRSL SAR法(50℃红外激发后270℃高温红外激发,pIRIR270℃)进行等效剂量测量,同时也应用post-IR OSL SAR法定年进行比较。实验结果表明,细粒混合矿物的pIRIR270℃等效剂量分别为418.8±13.2 Gy、562.3±18.2 Gy和694.8±17.9 Gy,相对应的post-IR OSL SAR等效剂量结果为345.0±29.4 Gy、409.6±33.7 Gy和424.7±32.2 Gy。假设强烈化学风化未对沉积物的剂量率造成很大影响,基于长石pIRIR270℃信号的释光年龄为89±6 ka、118±8 ka和152±9 ka,比前人所得的石英OSL SAR法年龄老30%~55%(约20~55 ka)。通过对比不同测量条件下获得的等效剂量值来评估长石IRSL信号是否存在晒退问题,没有发现长石post-IR IRSL信号存在晒退不完全的证据。根据本研究post-IR IRSL SAR法测年结果,赤山岛枫树嘴旧石器遗址似阿舍利技术类型的石器出现在倒数第二次冰期(MIS 6)后期至末次间冰期(MIS 5)前期,比湖南道县福岩洞现代人类牙齿化石年龄(80~120 ka)稍老。作为似阿舍利技术石器制造者的赤山岛古人与福岩洞现代人的关系将是我国旧石器时代考古学和古人类学研究的一个重要课题。     

Stability of fine‐grained TT‐OSL and post‐IR IRSL signals from a c. 1 Ma sequence of aeolian and lacustrine deposits from the Nihewan Basin (northern China)

We tested the suitability of the fine‐grained quartz (4–11 μm) Optical Stimulated Luminescence (OSL) and thermally‐transferred OSL (TT‐OSL), and the fine‐grained polymineral (4–11 μm) post‐infrared IRSL (post‐IR IRSL or pIRIR) signals for dating samples from aeolian‐lacustrine deposits from the Xiaochangliang archaeological profile in the Nihewan Basin, China; these deposits include material from the Jaramillo subchron (c. 1.0 Ma). In the upper aeolian section, the OSL and pIRIR₂₉₀ ages are consistent with each other, and show that the upper 8.8 m was deposited between c. 0.3 and c. 140 ka. The luminescence ages indicate a major discontinuity in deposition between the aeolian and the older lacustrine deposits. Below this hiatus at 9.4 m (i.e. in the lacustrine sediments) all three signals are found to be in field saturation (no further systematic increase in burial dose with depth) despite the TT‐OSL signal (apparent mean burial dose ~880 Gy) being well below saturation on the laboratory growth curve. This is in contrast to the pIRIR₂₉₀ signal, which saturates in the field at a level consistent with laboratory saturation. This results in a practical upper limit to the measured burial dose of ~900 Gy (2D₀). Thus for the TT‐OSL and pIRIR₂₉₀ signals, the upper limits for dating lacustrine deposits are <260 ka and c. 240 ka, respectively. These results have major implications for the appropriate future application of these signals. The ages of our lacustrine samples cannot be regarded as necessarily accurate ones; nevertheless, these ages provide the first long series absolute chronology for study of local palaeolithic and geomorphic evolution history aside from the magnetostratigraphical results available before this research.     

Luminescence evidence for two Middle Pleistocene interglacial events at Tourville, northwestern France

The infrared stimulated luminescence (IRSL) dating method is applied to alkali feldspar coarse grains from the two distinct Middle Pleistocene interglacial estuarine deposits of Tourville, located along the Seine Valley. The upper deposit (unit D), previously dated at 200 ka by ESR on in situ shells and correlated with a stage 7 high sea-level stand (186–245 ka), yields a measured IRSL age of 176 ± 21 ka. The lower deposit (unit B) assigned to a distinctly older high sea-level event (stage 9: 303–339 ka) yields a measured IRSL age of 273 ± 28 ka. The nearby stage 7 raised beach of Sangatte, in Northwestern France, previously dated by TL on quartz (229 ± 18 ka) yields a measured IRSL age of 186 ± 19 ka. These IRSL age estimates systematically underestimate the expected geological ages. This could be due to the long-term fading or instability of the luminescence signal in alkali feldspars. The correction for long-term fading has been tested on these samples. At Tourville, it yields corrected IRSL ages of 196 ± 23ka and 314 ± 32ka, for the upper and lower units respectively and, at Sangatte, a corrected IRSL age of 206 ± 20 ka. These corrected IRSL age estimates are in better agreement with the expected geological ages. This study demonstrates the potential of the feldspar luminescence dating method to provide chronological information on Middle Pleistocene interglacial estuarine sediments within the North Sea-English Channel Basin.     

Chronology of desert margin in western India using improved luminescence dating protocols

The present study provides improved chronology for the desert margin fluvial sediments of semi-arid region located in the Mahi river basin, western India. The sequence has preserved a near-continuous record of climate change since the Last Interglacial. An earlier attempt of dating based on feldspar IRSL chronology shows a combined effect of anomalous fading and unbleached components resulting in age inversions. The present work tries to explore the possibility of using blue light stimulated luminescence (BLSL) of quartz, infra-red stimulated luminescence (IRSL) of feldspar and the newly developed methodologies, like natural correction factor based single aliquot regeneration (NCF-SAR) protocol and decision making schemes based on distribution of doses and beta heterogeneity concept for luminescence dating of sediments. Observations suggest that quartz suffered from significant sensitivity changes during natural signal measurement and partial bleaching. A combination of NCF-SAR protocol and sample specific equivalent dose computation helped in arriving at better age estimate for present samples. The study also compares the criteria for the selection of different age models that are used at present. The age of the alluvial sequence is now bracketed between 10 ka (upper aeolian unit) and 75 ka (lowermost fluvial unit).     

Understanding processes of sediment bleaching in glacial settings using a portable OSL reader

Analysis of a high‐resolution suite of modern glacial sediments from Jostedalen, southern Norway, using a portable optically stimulated luminescence (OSL) reader, provides insights into the processes of sediment bleaching in glacial environments at the catchment scale. High‐magnitude, low‐frequency processes result in the least effective sediment bleaching, whereas low‐magnitude, high‐frequency events provide greater bleaching opportunities. Changes in sediment bleaching can also be identified at the scale of individual bar features: tails of braid‐bars and side‐attached bar deposits have the lowest portable reader signal intensities, as well as the smallest conventional OSL residual doses. In addition to improving our understanding of the processes of sediment bleaching, portable reader investigations can also facilitate more rapid and comprehensive modern analogue investigations, which are commonly used to confirm that the OSL signals of modern glacial sediments are well bleached.     

Bleaching of the post‐IR IRSL signal: new insights for feldspar luminescence dating

Post‐infrared (pIR) stimulated luminescence dating of sedimentary feldspar largely avoids the effects of anomalous fading that affect conventional infrared stimulated luminescence (IRSL) dating. However, optical resetting of pIR signals is more difficult than resetting the conventional IRSL signal, which may undermine the crucial assumption that pIR signals were effectively bleached upon deposition and burial of sediment grains. In this study, we quantify the bleaching properties of several pIR signals on various samples using laboratory‐simulated bleaching in full sunlight and water‐attenuated sunlight. Our data show that bleaching is most efficient under full spectrum conditions for all pIR signals and that pIR signals measured at elevated temperature are increasingly harder to bleach than IR and pIR signals measured at low temperature (e.g. IR at 50°C). All bleaching curves exhibit a very slow and steady decrease, indicating that a fixed un‐bleachable residual level cannot be reached within the 11 days of solar simulator exposure undertaken here. We show that the magnitude of a laboratory‐determined residual dose depends on the adopted bleaching protocol and cannot be used as a proxy for the dose that remains in the sample at the time of burial (remnant dose). Our data emphasize the importance of finding a balance between sufficient signal stability and a minimized contribution of a remnant dose when using pIR procedures for feldspar luminescence dating.     

Luminescence dating of lacustrine sediments from Tangra Yumco (southern Tibetan Plateau) using post‐IR IRSL signals from polymineral grains

Radiocarbon dating of bulk organic matter is the most commonly used method for establishing chronologies of lake sediments for palaeoclimate reconstructions on the Tibetan Plateau. However, this method is likely to be problematic because the dated material often suffers from old carbon contamination. Recently, advances in luminescence‐based chronological techniques have provided new options for dating lacustrine sediments. In the current study, we tested for the first time the applicability of a new post‐IR IRSL (pIRIR) measurement protocol for dating fine‐grained polymineral material from a deep‐lake sediment core from the central part of Tangra Yumco, on the southern Tibetan Plateau. Our results show that: (i) radioactive disequilibria in the uranium decay chain were observed in the studied lake sediments, and thus taken into account for dose rate calculation by using a dynamic modelling approach; (ii) the suitability and robustness of the pIRIR protocol measured at 150°C (pIRIR₁₅₀) for our samples are confirmed by a set of luminescence characteristic tests as well as the agreement with an independent age control; (iii) turbidite deposition partly caused an insufficient resetting of luminescence signals and thus apparent overestimation in luminescence dating; (iv) compared with the luminescence‐based age‐depth model, the ¹⁴C ages of bulk organic matter from the studied core generally yielded an age difference of ～2 ka, which is attributed to hardwater reservoir effects in Tangra Yumco. This study highlights the need for multi‐dating approaches of lake sedimentary archives on the Tibetan Plateau.     

Advances and Issues in Luminescence Dating of Loess Deposits in Arid Central Asia

High-resolution loess deposits are widely distributed in Arid Central Asia (ACA) and provide important records associated with dust transportation, paleoenvironmental and paleoclimatic evolution. The chronology is the foundation of the research into loess deposits as an environmental archive. In recent decades, the gradually developed optical dating method has been increasingly matured and become an important approach to establishing the loess-paleosol sequences. Here, we summarized and discussed previous work on loess chronology mainly based on optical dating approach in ACA. The following understandings have been listed: ① In comparison with optical dating method, the suitable material for ¹⁴C dating is uncommon in ACA. However, the dating range of luminescence dating is more extensive, and the dating materials are accessible. Thus, the optical dating is widely applicable in the establishment of loess framework in this area. ② Until now, the quartz Single Aliquot Regeneration (SAR) method can be applied to the establishment of loess-paleosol sequence since last glacial period. But several issues remain unaddressed. For example, the Optically Stimulated Luminescence (OSL) signal sensitivity of quartz grains are low in some areas. Furthermore, the results of OSL dating of different grain sizes within a single sample are inconsistent in some areas. The solution of these problems still requires more methodological research. ③ The post-IR IRSL (pIRIR) and multiple elevated temperature stimulation (MET-pIRIR) protoCols of feldspar have basically overcome the anomalous fading issue in the traditional IRSL dating process. In ACA, the framework since MIS 7 can be established with K-feldspar luminescence dating method. Compared with quartz luminescence characteristics, the K-feldspar luminescence signals are more sensitive and exhibit a high saturation level. In specific applications, it is necessary to establish the age frame according to the luminescence sensitivity, the age of samples or other factors.     

Paper I – Optically stimulated luminescence (OSL) dating of perennially frozen deposits in north‐central Siberia: OSL characteristics of quartz grains and methodological considerations regarding their suitability for dating

Arnold, L. J. & Roberts, R. G. 2011: Paper I – Optically stimulated luminescence (OSL) dating of perennially frozen deposits in north?central Siberia: OSL characteristics of quartz grains and methodological considerations regarding their suitability for dating. Boreas, Vol. 40, pp. 389–416. 10.1111/j.1502‐3885.2011.00209.x. ISSN 0300?9483. Optically stimulated luminescence (OSL) dating of coarse‐grained quartz is increasingly being used as the main chronological tool in late Quaternary palaeoenvironmental reconstructions of Siberia. However, relatively little information has been published on the suitability of OSL dating for the various types of perennially frozen sediments found in this region. Here we provide a systematic examination of the quartz luminescence characteristics of 21 perennially frozen samples from the Taimyr Peninsula and adjacent coastal lowlands of north‐central Siberia, and discuss their implications for the reliability of single‐grain and multi‐grain OSL chronologies in such contexts. The results of this study suggest that the quartz luminescence characteristics of these samples are, in principle, favourable for OSL dating but, in practice, require that a series of validation checks are made of the chosen experimental conditions. If these tests are satisfied, then reliable OSL chronologies should be obtained for sedimentary deposits in this region. Importantly, however, the single‐grain and multi‐grain aliquot equivalent dose (D_e) distribution characteristics for our samples reveal that there are advantages in targeting certain types of depositional settings for OSL dating studies of Siberian sediments. We also show that samples from the same depositional settings, and even from the same sites, do not necessarily display similar D_e distribution characteristics. The latter complication favours the use of single‐grain analysis to unravel the bleaching and burial histories of young (mid‐ to late Holocene) sediments in these Arctic environments.     

OSL dating of a Holocene loess-paleosol sequence in the southern Loess Plateau,China

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.     

南京市区埋藏古河道沉积物的年代

埋藏古河道沉积物年代学框架的建立对于探讨当地水系演变过程、重建气候演化历史具有重要意义。本文用光释光(OSL)测年中的简单多片再生法(SMAR)和单片再生法(SAR)对南京市区汉府街埋藏古河道堆积物钻孔样品进行了光释光测年,对岩芯中含有的植物碎片进行了AMS 14C测年。光释光等效剂量(De)的预热坪实验表明,在 200～260℃的预热温度范围内均能获得基本一致的De值,并得到了剂量恢复实验支持。样品的光释光年龄和树轮校正的AMS 14C年龄吻合,结果显示N06S6孔秦淮河古河道沉积是不连续的,主要堆积于6.6ka至7.9ka期间和14ka至15ka期间。末次冰盛期期间,秦淮河下切形成深达至少42m的古河谷。     

Fluvial system response to Late Devensian (Weichselian) aridity,Baston, Lincolnshire,England

Little is known about the impact of Late Devensian (Weichselian) aridity on lowland British landscapes, largely because they lack the widespread coversand deposits of the adjacent continent. The concentration of large interformational ice‐wedge casts in the upper part of many Devensian fluvial sequences suggests that fluvial activity may have decreased considerably during this time. The development of optically stimulated luminescence (OSL) dating enables this period of ice‐wedge cast formation to be constrained for the first time in eastern England, where a marked horizon of ice‐wedge casts is found between two distinctive dateable facies associations. Contrasts between this horizon and adjacent sediments show clear changes in environment and fluvial system behaviour in response to changing water supply, in line with palaeontological evidence. In addition to providing chronological control on the period of ice‐wedge formation, the study shows good agreement of the radiocarbon and OSL dating techniques during the Middle and Late Devensian, with direct comparison of these techniques beyond 15 000 yr for the first time in Britain. It is suggested that aridity during the Late Devensian forced a significant decrease in fluvial activity compared with preceding and following periods, initiating a system with low peak flows and widespread permafrost development. Copyright © 2004 John Wiley & Sons, Ltd.     

Infrared stimulated luminescence dating of an Eemian (MIS 5e) site in Denmark using K‐feldspar

Buylaert, J.‐P., Huot, S., Murray, A.S. & Van den haute, P.: Infrared stimulated luminescence dating of an Eemian (MIS 5e) site in Denmark using K‐feldspar. Boreas, 10.1111/j.1502‐3885.2010.00156.x. ISSN 0300‐9483. Infrared stimulated luminescence (IRSL) dating of K‐feldspars may be an alternative to quartz optically stimulated luminescence (OSL) dating when the quartz OSL signal is too close to saturation or when the quartz luminescence characteristics are unsuitable. In this paper, Eemian (MIS 5e) coastal marine sands exposed in a cliff section on the coast of southern Jutland (Denmark) are used to test the accuracy and precision of IRSL dating using K‐feldspars. This material has been used previously to test quartz OSL dating ( Murray & Funder 2003 ): a small systematic underestimation of <10% compared to the expected age of ～130 ka was reported. In our study, a single‐aliquot regenerative‐dose (SAR) IRSL protocol is used to determine values of equivalent dose (D_e) and the corresponding fading rates (g values). A significant age underestimation (of up to ～35%) is observed; this is attributed to anomalous fading. Using a single site‐average fading rate of 3.66 ± 0.09%/decade to correct the IRSL ages for all samples provides good agreement between the average fading‐corrected K‐feldspar age (119 ± 6 ka) and the independent age control (132–125 ka). This is despite the reservations of Huntley & Lamothe (2001) that their fading correction method is not expected to work on samples older than ～20–50 ka. This fading‐corrected feldspar result is not significantly different from the overall revised quartz age (114 ± 7 ka) also presented here. We conclude that fading‐corrected IRSL ages measured using K‐feldspar may be both precise and accurate over a greater age range than might be otherwise expected.     

Residual luminescence in modern debris flow deposits from western Taiwan: A single grain approach

In an active fold-and-thrust belt, sediment is commonly transported in the form of debris and colluviums, and the ages of such deposits can be important for seismic hazard assessment. These sediments are mainly transported by high concentration flows that travel very short distances before burial, and therefore have very few opportunities for daylight exposure and bleaching, which limits the application of luminescence dating in such environments. Luminescence studies on modern debris flow deposits and channel sediments in central Taiwan indicate a mixed population of bleached and unbleached grains. The well bleached grains constitute a small proportion of the sediments and could only be identified using the single grain dating technique; doing single aliquot analysis may result in overestimation of the age of such sediments by 3–25 ka. The data reveal that outwash sediments are better bleached than debris flow sediments. Our results show that quartz that has experienced partial resetting can be used for luminescence dating only through the use of the single grain technique.     

Fluvial aggradation phases in the Upper Rhine Graben—new insights by quartz OSL dating

The Upper Rhine Graben (URG) is characterized by a thickness of up to 500 m of unconsolidated Quaternary sediments, providing excellent records of the Rhine river system and its responses to tectonic and climatic changes. The most complete Quaternary sequence of fluvial and limnic-fluvial deposits is found in the Heidelberg Basin, due to its long-term subsidence since the mid-Eocene. The aim of this study is to provide a chronological framework using optically stimulated luminescence (OSL) dating of aeolian and fluvial sands derived from the upper 33 m of a sediment core, which was drilled into the Heidelberg Basin infill close to the village of Viernheim, Germany. The OSL ages demonstrate that the dated fluvial sediments were deposited during the last glacial period (Weichselian) and that there were at least three aggradation periods during this episode. The coversands that cap the sequence were emplaced during the early Holocene.     

冰川沉积释光测年： 采样策略与测试选择

释光测年是可对冰川地貌进行直接定年的一种测年技术,已被广泛应用于冰川沉积测年中,推动了第四纪冰川研究的深入发展。但冰川沉积释光测年还没有达到标准化的程度,实际应用中仍有不少问题需要探究,其中最受关注的是冰川沉积物释光信号晒退不完全的问题,即样品在埋藏前因曝光机会有限导致信号没有归零或仅部分归零。冰川沉积释光信号晒退程度与地貌部位和沉积环境密切相关。冰川沉积释光采样需注意几个方面：（1）详细的地貌学和沉积学调查及对采样点的选择;（2）较适合释光测年的冰水沉积和冰缘风成沉积采集及其与冰川作用期次的联系;（3）冰碛夹层中的冰水砂透镜体的选取;（4）冰碛垄采样时垂直与水平方向上的考量;（5）岩石释光测年的发展使砾石成为当前第四纪冰川释光测年采样的一种选择。室内进行释光等效剂量测试时,也有几个关键的选择：（1）粗颗粒石英光释光测年是末次冰期以来冰川作用的首选方法;（2）如果样品年代老于石英测年上限,或者石英不适合测试,则可考虑钾长石后红外高温释光测年方法;（3）单颗粒、小测片和岩石释光埋藏测年技术可以鉴别样品的晒退情况,是目前最适合冰川沉积释光测年的几种选择;（4）如有条件,尝试用不同矿物、不同粒径、不同方法进行测试对比和交叉检验。要获得第四纪冰川释光测年的最佳年代学结果,地貌学、沉积学和年代学的结合是非常必要的。     

Is X‐ray core scanning non‐destructive? Assessing the implications for optically stimulated luminescence (OSL) dating of sediments

Optically stimulated luminescence (OSL) dating is widely used to date clastic deposits, including those collected by coring. X‐ray scanning of cores has become popular because of the rapidly acquired, high‐resolution information it gives about optical, radiographic and elemental variations. Additionally, X‐ray scanning is widely viewed as a non‐destructive method. However, such instruments use an intense X‐ray beam that irradiates the split core to enable both X‐radiographic and X‐ray fluorescence (XRF) analysis. This irradiation will influence the optically stimulated luminescence signal in the sediments. This study determines the radiation dose delivered to sediments in a core during an X‐ray scan, and assesses the implications for studies wishing to combine X‐ray scanning and OSL dating. Copyright © 2009 John Wiley & Sons, Ltd.