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1.
准确获得水成沉积物的年龄是第四纪年代学重要的前沿问题之一。随着释光技术的发展,水成沉积物释光测年在如下方面有新的进展:具体释光技术的选择、释光测量方法、测年矿物的种类、矿物的粒级和获得等效剂量的统计方法等。线性调整光释光技术能够提取光释光信号中衰退快的组分;单片再生法应用广泛;单颗粒技术在挑选沉积时晒退充分的颗粒方面具有一定的优势;水成沉积物中的石英比长石更易晒退;较多的实验表明水成沉积物中的粗颗粒比细颗粒更易晒退;获得等效剂量的统计模型很多,但尚无一种统计模型适用于所有样品。在此基础上探讨了水成沉积物释光测年在气候、构造运动、冰川进退历史和人类活动主导的土壤侵蚀量变化研究中的意义及今后的研究方向,为全面了解该领域的最新研究进展提供参考。 相似文献
2.
准确获得水成沉积物的年龄是第四纪年代学重要的前沿问题之一。随着释光技术的发展,水成沉积物释光测年在如下方面有新的进展：具体释光技术的选择、释光测量方法、测年矿物的种类、矿物的粒级和获得等效剂量的统计方法等。线性调整光释光技术能够提取光释光信号中衰退快的组分;单片再生法应用广泛;单颗粒技术在挑选沉积时晒退充分的颗粒方面具有一定的优势;水成沉积物中的石英比长石更易晒退;较多的实验表明水成沉积物中的粗颗粒比细颗粒更易晒退;获得等效剂量的统计模型很多,但尚无一种统计模型适用于所有样品。在此基础上探讨了水成沉积物释光测年在气候、构造运动、冰川进退历史和人类活动主导的土壤侵蚀量变化研究中的意义及今后的研究方向,为全面了解该领域的最新研究进展提供参考。 相似文献
3.
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。 相似文献
4.
断层崩积楔单片再生法光释光测年:以山西忻定盆地西田探槽为例 总被引：3，自引：0，他引：3
为了研究断层崩积楔各部位沉积物光释光信号晒退情况及崩积楔形成年龄,利用中颗粒石英(63~90μm)单片再生法(SAR)对山西忻定盆地西田探槽断层崩积楔3个部位的4个样品进行光释光(OSL)定年。选择一代表性样品(08-OSL-22)进行等效剂量(DE)、LN/TN、循环比率、回授率与预热温度的关系分析,结果表明预热温度260℃、预热时间10 s为样品最佳预热条件。4个样品的测片循环比率基本在0.9~1.1之间,回授率均小于5%,表明所采用的中颗粒SAR法流程可以很好地校正测量过程中产生的释光感量变化,其等效剂量可信。利用等效剂量分布直方图和累积频率图,发现古地形面和坡积物的样品晒退均匀,崩积层样品则较差。对于晒退较差的样品利用累积频率法得到其等效剂量,从而得到崩积楔的近似年龄。最后获得该期崩积楔的形成年龄为(27.09±0.71)ka。 相似文献
5.
近年来光释光测年在单颗粒技术上的研究取得了一系列重要进展,极大地提高了测年精度,为地质考古测年提供了更大的空间,研究者们对全球重要考古遗址点进行了详细的单颗粒测年,取得诸多考古新发现。单颗粒释光技术是在光释光单片技术上发展而来,对样品的单个石英或长石颗粒进行独立测试,基于单个颗粒测量结果,结合误差理论、统计学分析和样品地质沉积特征分析获得样品的准确年龄。本文结合大量地质考古样品的单颗粒测年数据,重点阐述了单颗粒释光测年技术的原理、发展历程、实验流程、筛选条件和年龄模型。单颗粒释光技术为地质考古的精确定年提供了可能性,尤其是对由于晒退不充分等原因导致的等效剂量分散的样品,如过度分散值(OD)高达20%甚至超过50%的地质考古样品,提供了新的方法和及时支持。通过开展释光测年信号分析,选择不同的单颗粒样品年龄模型分析,可以得到较为可靠的年龄,为诸多地质考古遗迹建立年代学框架。 相似文献
6.
7.
亚洲中部干旱区黄土释光测年研究进展及其问题 总被引：2，自引：2，他引：0
中亚干旱区广泛分布的黄土沉积为研究这一区域的大气粉尘、环境和气候演化提供了良好载体,而黄土年代学是气候环境研究的基础。近几十年来逐渐发展并日趋成熟的释光测年方法是建立黄土地层序列的重要手段。通过对中亚干旱区的测年进展(主要是释光测年)进行总结梳理,得到如下认识:(1)释光测年方法与14C测年方法比较,测年范围更广,测年材料易得,在此区域黄土框架的建立中有广泛适用性;(2)石英光释光单片再生法(SAR)能够用于建立中亚干旱区末次冰期以来黄土沉积的年代框架,但是需要考虑部分地区石英灵敏度偏低、不同粒径结果不一致等问题,这些问题的解决仍然需要更多的方法学的研究;(3)长石的两步法(pIRIR)与多步法(MET-pIRIR)已经基本克服了传统IRSL方法中信号的明显异常衰退现象,在此区域可以建立MIS 7以来的年代框架,长石的灵敏度高,可以用来测试石英灵敏度低而无法得出可靠年代的样品,其测年范围比石英更广,在具体的应用中需要根据样品灵敏度高低、年老程度等因素综合考虑来建立年代框架。 相似文献
8.
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。 相似文献
9.
沉积物光释光(OSL)测年方法按所用激发光源波长可分为绿光释光(GLSL)和红外释光(IAsL)两种技术。前者用波长514.5nm或514土15urn绿光束激发石英矿物产生释光信号进行测年;后者通常用波长800～950urn红外线束激发钾长石产生释光信号进行测年。对于同一个含有石英和钾长石碎屑矿物的沉积物样品,同时进行绿光释光和红外释光测年并对比其结果,也许可获得光释光测年可靠性的一种自检。为此,我们对郑州郎山黄土剖面中8个马兰黄土样品作了试验。每个样品都制备成细粒(4～11pm)组分约40个测片,分成4组(各为6,8,18和6个)分别作天然、天然加p剂量诱发、天然经90分钟阳光表回郎山马兰黄 相似文献
10.
晋豫间黄河峡谷黄土状沙丘的光释光年代学探讨 总被引：6，自引：6，他引：0
通过对风陵渡-三门峡晋豫间黄河峡谷的地貌考察和1:50000 地形图(1970年)的分析,初步查明了黄河南岸黄土状沙丘的分布特征.选取河南省灵宝市豫灵镇阌底约75m高的黄土状沙丘剖面进行了观测和取样.根据该剖面的粒度分布特点,选取中颗粒(40～90μm)石英进行了光释光(OSL)测年研究.采用简化SAR法测量样品的等效剂量(De),其中5个样品与SAR法测量的De值对比,结果在误差范围内一致.对阌底剖面自上而下19个样品运用简化SAR法做了OSL年龄测定,其中8个还进行了4～11μm细颗粒石英简易多测片再生法(SMAR)OSL测年,两个粒级石英的OSL年龄测定值在测量误差范围内一致.初步结果表明,晋豫间黄河峡谷阌底黄土状沙丘发育不晚于距今约5.5万年前,并延续到全新世初期,风沙堆积速率在3.2万年前后曾出现显著变化. 相似文献
11.
M. Frechen 《International Journal of Earth Sciences》1999,87(4):675-684
Loess/palaeosol sequences from the Loess plateau in China were investigated by combined infrared optically stimulated luminescence
(IRSL) and thermoluminescence (TL) dating techniques in order to study the luminescence properties of the loessic sediments
and to provide a direct chronological link for correlation and position of the last interglacial soil in Central Asia and
the Loess plateau in China. Sensitivity changes were found for all samples through artificial bleaching of the samples. The
greatest sensitivity changes, of up to 50%, were found for very old loess samples designated to be older than the Matu-yama/Brunhes
magnetic boundary and hence older than 788,000±1,800 years. The upper dating limit, as investigated by the very old loess
samples, ranges from 250,000 to 300,000 years, if the TL additive dose method is applied. The chronological position of the
last interglacial soil S1 at the section near Lanzhou indicates luminescence age estimates ranging from 82,000 to 75,000 years
for the marine-isotope stage 5 to 4 transition. However, the loess from below S1 yielded luminescence age estimates between
153,200±14,200 and 110,100±20,100 years for TL and IRSL additive dose methods, respectively. Thus, a direct correlation between
the S1 and the first intercalated pedocomplex PC1 in Central Asia is most likely.
Received: 31 March 1998 / Accepted: 25 October 1998 相似文献
12.
This paper reports the application of optically stimulated luminescence (OSL) dating to relatively coarse grains (100–200 μm) of quartz extracted from loess. Two approaches were tested – a multiple aliquot technique and a new single aliquot approach, which is especially suited to the dating of small quantities of such grains found in some loess. The results are compared with infra‐red stimulated luminescence and thermoluminescence (TL) measurements on the finer‐grained (4–11 μm) polymineral fraction and TL measurements on the relatively coarse grains of quartz. The advantages of the new single aliquot (OSL) approach are described and the iterating, computer‐controlled measurement procedure is given. The automated iterative single aliquot regeneration (AISAR) method corrects for changes in luminescence sensitivity during the measurement sequence by monitoring the response to a test dose. Some initial measurements are presented for the loess section at Zemechy, Czech Republic, and these show that the AISAR method gives more precise results than those using a multiple aliquot method. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
13.
《Quaternary Science Reviews》2003,22(2-4):407-421
Along the southeastern coastline of the Korean peninsula, well-developed marine terraces are found at various elevations. The ages of these terraces, and the time of deposition of the terrace sediments are important to our understanding of the geological history of this area during the Quaternary period, and represent a unique record of the regional tectonic activity. Previous efforts to establish a chronology using optically stimulated luminescence (OSL) methods have produced controversial results, particularly because of stratigraphic inconsistency and poor reproducibility. In this paper, the application of OSL dating based on the single-aliquot regenerative-dose (SAR) protocol for quartz is investigated. The dependence of equivalent dose on the preheat and cut-heat temperatures (thermal treatment of the regeneration and test-doses, respectively) are examined. Linearly modulated luminescence signals from chemically cleaned quartz samples are used to identify the presence of a thermally unstable component with a large optical cross-section (component A′), which in part affects the ability to correct for sensitivity changes during measurements, and thus the reliability of the equivalent dose estimates. In some samples, a higher heat treatment after the test-dose is shown to improve our ability to measure a dose given in the laboratory before any heat treatment (dose recovery test). This higher temperature treatment effectively removes component A′, and hence improves sensitivity correction. Furthermore, the samples were broadly divided into poorly sorted and well-sorted, based on field evidence. The poorly sorted samples contain friable, weathered gravel clasts, which is a likely post-depositional source of quartz grains. In general, these grains will not have been zeroed prior to deposition, and so the poorly sorted samples are rejected from further age studies. Results obtained from the well-sorted samples are reproducible at each sampling location, and give ages grouping broadly into 50–70 and 110–120 ka, but laterally discontinuous on a scale of tens of km. Our OSL results for the younger group are supported by radiocarbon ages from overlying terrestrial deposits. It is concluded that these results point to considerable tectonic activity in the southeast of Korea during the Late Pleistocene. 相似文献
14.
Loess sedimentation in Tibet: provenance,processes, and link with Quaternary glaciations 总被引：2，自引：0，他引：2
《Quaternary Science Reviews》2007,26(17-18):2265-2280
Well-preserved loess deposits are found on the foothills of mountains along the middle reaches of the Yarlung Zangbo River in southern Tibet. Optically stimulated luminescence (OSL) dating is used to determine loess ages by applying the single-aliquot regeneration technique. Geochemical, mineralogical, and granulometric measurements were carried out to allow a comparison between loess from Tibet and the Chinese Loess Plateau. Our results demonstrate that (i) the loess deposits have a basal age of 13–11 ka, suggesting they accumulated after the last deglaciation, (ii) loess in southern Tibet has a “glacial” origin, resulting from eolian sorting of glaciofluvial outwash deposits from braided river channels or alluvial fans by local near-surface winds, and (iii) the present loess in the interior of Tibet has accumulated since the last deglaciation when increased monsoonal circulation provided an increased vegetation cover that was sufficient for trapping eolian silt. The lack of full-glacial loess is either due to minimal vegetation cover or possibly due to the erosion of loess as glaciofluvial outwash during the beginning of each interglacial. Such processes would have been repeated during each glacial–interglacial cycle of the Quaternary. 相似文献
15.
In this paper, simple thermoluminescence (TL) dating procedures utilizing non‐diagnostic sherds from fluvial deposits are described. This approach may provide preliminary insights into the chronology of fluvial sequences in areas where transported ceramics are common, but alluvial chronologies are not well developed. Our method deviates from conventional TL‐ dating methods in that simple screening measurements are made from small, heavily abraded sherds, and dose rates are estimated rather than being measured from each sample. This results in rapid and inexpensive laboratory measurements, which can be used to support field surveys. The limitations in precision and accuracy relative to quantitative luminescence procedures are discussed. It is argued that the results can be used to estimate an approximate maximum age of alluvial deposition events. The approach is illustrated with results from a geoarchaeological survey in Cyprus. © 2005 Wiley Periodicals, Inc. 相似文献
16.
《Quaternary Science Reviews》2003,22(10-13):1131-1138
In this investigation we evaluate several proposed optically stimulated luminescence single-aliquot regeneration (OSL SAR) procedures to determine which technique has the greatest potential to yield accurate ages for samples collected from tuff-derived alluvial sediments within the narrow, sharply incised canyon systems of the Pajarito Plateau of northern New Mexico. The SAR data collection methods evaluated are: infrared-stimulated luminescence (IRSL), post-IR blue-OSL, IRSL with TL annealing cycles on polymineral fine-grains, and blue-OSL on quartz fine sand. A single-grain laser luminescence (SGLL) procedure for quartz sand is also evaluated. Age estimates obtained from these methods are compared with radiocarbon, soil PDI (profile development index), and IRSL multi-aliquot additive dose (MAAD) age constraints. Our results indicate that the modal De of quartz sand SGLL dose distributions yield ages that are consistent with radiocarbon and PDI age constraints for the tuff derived sediments in this investigation and appears to be the most promising method for studies in this area. Additionally, two fine-grained polymineral methods, IRSL SAR and traditional IRSL MAAD, produced ages that were generally in agreement with the SGLL ages and with available 14C and PDI age constraints. At the present stage of research, we advocate using quartz sand SGLL in conjunction with IRSL SAR or even IRSL MAAD for polymineral fine-grains to provide the most robust and reliable luminescence age data sets for tuff-derived sediments. 相似文献
17.
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. 相似文献
18.
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。 相似文献
19.
《Quaternary Science Reviews》2003,22(10-13):961-966
Luminescence dating of loess has generally been restricted to a maximum of 100–150 ka, due primarily to the anomalous fading behaviour of feldspar. Recent studies have shown that the far-red luminescence from feldspar does not suffer from anomalous fading, and as such may have the potential to extend the age range of the luminescence dating method. The purpose of the present project is to further develop luminescence dating techniques using red and far-red emissions to date loess older than 100–150 ka. We present results demonstrating the presence of a far-red (λ>665 nm) IRSL emission in Chinese loess, and describe a series of basic experiments which seek to characterise aspects of this emission. These include an examination of sensitivity change, and dose reconstruction tests via the employment of a modified single aliquot regeneration (SAR) protocol. It is demonstrated that (a) far-red IRSL can be observed from Chinese loess; (b) far-red IRSL signal is highly reproducible; and (c) a range of laboratory doses from 100 up to 600 Gy can be accurately recovered using a modified SAR procedure. 相似文献