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1.
具有良好重现性的石英热释光信号除了用于近地表的考古及地质事件定年以外,还能反映一定地质时间范围内的环境温度变化规律.本文利用砂岩中石英矿物的热释光信号,采用传统热释光分析和等温热释光方法,以东营凹陷中央背斜带钻孔岩芯为例,探讨对沉积盆地热体制信息的指示意义.研究表明：（1）钻孔中不同埋深位置的石英矿物,其自然热释光发光曲线有规律变化,与所对应的环境地层温度以及热释光发光动力学相符,即随着沉积地层埋深增加、埋藏温度上升与埋藏时间加大,其热释光发光曲线整体向高温方向移动,而发光强度明显减小;（2）石英热释光多片增加分析方法以及等温热释光分析方法所获得的表征年龄彼此印证,通过表征年龄的换算,定性或半定量获得描述沉积盆地热演化史的环境古温度变化的一个等效参数——表征温度,该表征温度能够表征沉积盆地一定地层范围内,一段埋藏历史的古温度变化历史.石英热释光信号是沉积盆地热史分析中一种潜在的古温标,对于石英热释光表征年龄与表征温度地质意义的诠释,仍需要更多的研究事例加以佐证. 相似文献
2.
The Mississippi and Missouri river valleys in the midcontinental United States contain extensive loess-paleosol sequences that are used to constrain the timing of expansion and retreat of the Laurentide Ice Sheet. Previous studies have been unsuccessful in producing finite ages for sediments older than ∼150 ka due to saturation of luminescence emissions. The thermally transferred optically stimulated luminescence (TT-OSL) dating technique is tested on the fine-grained (4–11 μm) quartz fraction of these loess deposits because the TT-OSL signal has been shown to grow with high (kGy) radiation doses. The TT-OSL signal continued to increase with radiation dose above 900 Gy. The optical and thermal stabilities of this TT-OSL signal are evaluated. Equivalent dose values are highly sensitive to preheat temperatures. Recycling ratios, zero-dose response values, and dose recovery tests all yield acceptable values for samples with burial doses >∼200 Gy. The apparent TT-OSL ages for the Roxana Silt (∼52–63 ka), Teneriffe Silt (∼66 ka), and Loveland Silt (∼133–192 ka) agree at 1σ level with previously published TL and IRSL ages derived from the same samples. For the oldest unit, the Crowley's Ridge Silt, TT-OSL ages (∼167–200 ka) are younger than IRSL or TL ages by ∼20%. This is interpreted as underestimation related to TT-OSL signal contamination, which can be avoided by isolating the fast component of the TT-OSL. Preliminary fast component TT-OSL ages for the Crowley's Ridge Silt (∼197–241 ka) favor deposition during marine oxygen-isotope stage (MIS) 7 or 8, contrary to a previous inference of a MIS 12 deposition. 相似文献
3.
In this study, fine-grain quartz was used for luminescence dating for lava baked samples from different sites in Datong. Optical stimulated luminescence (OSL), thermal transferred OSL (TT-OSL)/recuperated OSL (Re-OSL) and thermoluminescence (TL) dating protocols were applied. For these samples, the OSL signals saturate at about 300–400 Gy, which limits their age to less than 100 ka based on their ambient dose rates. The TT-OSL/Re-OSL method has poor dose recovery. TL dating gives reliable results, and multiple-aliquot regenerative-dose TL method with sensitivity change correction based on the 325 °C TL peak of a test dose can be applied for samples up to 400 ka. The results indicate that the ages of the volcanoes in Datong are from 380 ka to 84 ka. The volcanic activity started earlier in the southeast area than those in the northwest part, which is consist with the literature data. 相似文献
4.
《Quaternary Geochronology》2008,3(1-2):114-136
We present chronological constraints on a suite of permanently frozen fluvial deposits which contain ancient DNA (aDNA) from the Taimyr Peninsula of north-central Siberia. The luminescence phenomenology of these samples is first discussed, focusing on the optically stimulated luminescence (OSL) decay curve characteristics, thermoluminescence (TL) properties, and signal compositions of quartz from these previously unstudied deposits. Secondly, we assess the suitability of these samples for OSL dating and present the OSL chronologies obtained using both single-grain and multi-grain equivalent dose (De) measurements. The results of our analyses reveal a large amount of inter-aliquot variability in OSL decay curve shape that is directly related to differences in the size of the 280 °C TL peak and the associated slowly bleached ‘S2’ OSL component. Longer OSL stimulation durations are adopted in the De measurement procedure to prevent the progressive build-up of slowly bleached signal components throughout successive single-aliquot regenerative-dose (SAR) measurement cycles. The use of low preheat temperatures in the SAR procedure also reduces the deleterious effects of these slowly bleached signal components. The resultant single-grain and multi-grain OSL chronologies obtained using this approach are stratigraphically consistent and are in close agreement with independently established 14C ages at our sites. The findings of this research reveal the potential of OSL dating as a means of providing a reliable chronometric framework for sedimentary aDNA records in permafrost environments. 相似文献
5.
The present study aimed to test reliability of luminescence and electron spin resonance (ESR) methods to date tephra. We investigated on three Japanese marker tephras, Ikeda-ko (6.4 ka), Aira-Tn (30 ka) and Aira-Iwato (45–50 ka). A systematic studies were performed using different minerals (quartz and feldspar), different grain fractions (75–250 and 250–500 μm), different luminescence and ESR signals, like optically stimulated luminescence (OSL) of quartz, infrared stimulated luminescence (IRSL) of feldspar, including recently developed least faded post infrared IRSL (pIR-IRSL), and ESR signals from paramagnetic centers Al and Ti–Li of quartz. Ages obtained using pIR-IRSL signal of plagioclase with preheat of 320 °C, 60 s and stimulation at 300 °C are consistent with the reference ages. High dose detection range (up to ∼600 Gy) and accurate age estimation enable pIR-IRSL of feldspar a promising methodology to date quaternary tephra. ESR ages from quartz are grossly correlated with the reference ages but large deviation and large associated errors are observed, possibly due to either low signal to noise ratio or heterogenous dose response of different aliquot in multiple aliquot additive dose (MAAD) approach. 相似文献
6.
Optically stimulated luminescence (OSL) thermochronometry is an emerging application, whose capability to record sub-Million-year thermal histories is of increasing interest to a growing number of subdisciplines of Quaternary research. However, several recent studies have encountered difficulties both in extraction of OSL signals from bedrock quartz, and in their thermochronometric interpretation, thus highlighting the need for a methodological benchmark. Here, we investigate the characteristic OSL signals from quartz samples across all major types of bedrock and covering a wide range of chemical purities. High ratios of infrared to blue stimulated luminescence (IRSL/BLSL), an insensitive ‘fast’ OSL component, and anomalously short recombination lifetimes seen in time-resolved luminescence (TR-OSL), are often encountered in quartz from crystalline (magmatic and metamorphic) bedrock, and may hamper successful OSL dating. Furthermore, even when the desirable signal is present, its concentration might be indistinguishable from its environmental steady-state prediction, thus preventing its conversion to a cooling or heating history. We explore the saturation properties and the thermal activation parameters of various OSL signals in quartz to outline the capabilities and limitations for their use in low-temperature thermochronometry. 相似文献
7.
R.M. Bailey 《Quaternary Geochronology》2010,5(5):559-568
The usual practice in optical dating is to derive an equivalent dose (De) (and hence age) from integration of the initial part of the measured optically stimulated luminescence (OSL) signal. This ‘bulk’ OSL signal is known to comprise several semi-independent components, each of which decays at different rates during measurement, and thus contributes a different proportion to the bulk signal as measurement time progresses. Data are presented here which show a strong dependence of De on the bulk signal integration interval, with reduced De for later signal integration intervals resulting from lower medium component De values. This dependence leads to two problems: (i) deciding which signal integral to choose, and (ii) the possibility that all bulk signals will provide systematic age underestimation due to medium component signal contributions. Isolating the fast component of the bulk OSL signal provides a solution to both problems and several methods of achieving this are assessed; an efficient new method is described which is incorporated in to standard single-aliquot regenerative-dose measurement sequences. This method involves the direct measurement of the fast-component signal using infrared (830 nm) stimulation of quartz at 160 °C, prior to the standard bulk OSL measurement with 470 nm stimulation. It is shown that the measured quartz infrared stimulated luminescence signals resolve pure fast-component signals and provide De estimates consistent with those from signal deconvolution. This approach can only be applied to samples with relatively bright luminescence emissions, but in these cases is expected to provide a more robust estimate of palaeodose. 相似文献
8.
Unlike the well-studied optically stimulated luminescence (OSL) signal of (macrocrystalline) quartz, not much is known about OSL from natural amorphous and microcrystalline silicon dioxide. These materials – generally termed “silex” – were widely used for prehistoric tool production, and thermoluminescence (TL) is routinely applied do date the firing event of heated specimens. This study presents data on basic OSL characteristics of silex such as signal composition and component-resolved thermal stability as well as the applicability of OSL for dating of burnt lithic tools.Fitting of LM-OSL curves yielded similar components (mostly five) as observed for quartz, with the photoionization cross-sections being in the same order of magnitude for both materials. Three different methods (LM-OSL pulse annealing, short-shine pulse annealing as well as the varying heating rate method) were applied to study the thermal stability of components and allowed calculating trap parameters E and s, and hence the electron retention lifetime. Only the most light-sensitive (“fast-like”) component proved to be of sufficient thermal stability for dating applications, as evidenced from coherent experimental results. All other components already diminished at preheating temperatures > 200 °C. Pulse annealing measurements further indicate that electron populations sampled by OSL and those responsible for the ca. 380 °C TL-“dating peak” are not identical. Dose recovery tests applying an OSL-SAR protocol with “hot bleach” in between the regeneration cycles showed good reproducibility of a known dose if only the initial OSL signal (ca. 0–0.5 s at 90% LED power) is used. Finally, obtained OSL-SAR and TL ages based on the blue TL emission are in agreement within errors for two Middle Paleolithic archeological samples showing a “fast-like” component. These results verify the experimental findings of sufficient long-term stability of the initial OSL signal. Since not all silex specimens deliver a bright and stable OSL signal, optical ages of suitable samples may serve as an additional internal check for the paleodose estimate rather than substituting TL as a standard technique for dating of heated silex. 相似文献
9.
Quartz optically stimulated luminescence (OSL) dating is widely used to determine the time of deposition and burial of Late Quaternary sediments. Application of the method is usually limited to the past 150,000 years due to early saturation of the OSL signal. Here we explore the potential to date Quaternary sediments using the violet (402 nm) stimulated luminescence (VSL) signal of quartz. We develop and test a new post-blue VSL single aliquot regenerative dose dating protocol, and demonstrate that the VSL signal originates from a deep trap at about 1.9 eV with a thermal lifetime of 1011 years at 10 °C, and that this trap is bleachable by sunlight. The VSL signal grows with dose to ∼6400 Gy, a factor ∼20 higher than the conventional quartz OSL signal, and with the proposed protocol we recover a known dose of 1000 Gy in three out of four samples. The potential of the VSL protocol for dating Quaternary sediments is highlighted by its successful application to a suite of geological samples ranging in age between 13 and 330 ka. Based on our investigations, we propose that the VSL protocol has the potential to extend the quartz dating range to cover the full Quaternary. 相似文献
10.
OSL dating of sediments from deserts in northern China 总被引：2，自引：0，他引：2
Aeolian samples from deserts in northern China were studied using the optically stimulated luminescence (OSL) of quartz and potassium (K) feldspar separates. K-feldspar has shown advantages over quartz for dating samples younger than 100 years, due to its more homogeneous equivalent dose (De) values, higher internal dose rate and higher luminescence sensitivity to dose. Without additional measurements, the luminescence characteristics of quartz obtained in De determination procedures can be used to reveal the source material and/or quartz thermal history for the deserts in northern China. The results indicated that the duration of paleosol formation in desert areas reflects regional paleoenvironments. 相似文献
11.
Dating of quartz by optically stimulated luminescence (OSL) has been revolutionized with introduction of the test dose (TD) in development of a measurement sequence known as the single-aliquot regenerative-dose (SAR), whereby a valid sensitivity correction for the luminescence signal is provided in the measurement cycle. However, the size of the TD used in the SAR protocol remains controversial. Previous studies show that the TD has little effect on the equivalent dose (De) for young samples in luminescence dating in which the applicability of different deposits varies greatly in different regions. However, detailed studies are lacking on how TD size affects SAR–OSL results of samples with a relatively high De range. In this study, typical loess samples with high De values (∼60 Gy–∼250 Gy) from the eastern Tibetan Plateau were selected to investigate the effects of variation in TD size on the quartz SAR–OSL protocol. Dose recovery tests show that a known dose could be recovered successfully by applying different TDs. Test dose size has an effect on shapes of regenerated dose–response curves (DRCs) and has different influences on Des and characteristic saturation doses for quartz samples with a high dose range. A TD size of 20%–30% De is a good compromise for Tibetan loess with De of ∼60–120 Gy in the quartz SAR protocol, and a TD size larger than 30% should be considered for samples with a larger De. The results of this study highlight the importance of TD size in the SAR–OSL protocol for quartz samples with a high dose range. 相似文献
12.
This paper reports on the first investigations into the potential of luminescence dating to establish a chronological framework for fluvial processes in the Tisa River Valley in Vojvodina, N Serbia. A total of 18 samples were collected from a terrace exposure near Mužlja, which comprised non-fluvial deposits at the top and fluvial deposits at the base. The luminescence characteristics of sand-sized quartz and potassium feldspar grains were investigated using a single-aliquot regenerative dose (SAR) protocol. The quartz separates exhibit a complex behaviour, making this dosimeter less suited for optical dating. Investigations into the behaviour of infrared stimulated luminescence (IRSL) measured at 50 °C (IR50) from K-rich feldspar extracts showed that preheating in excess of 60 s at 225 °C leads to significant sensitivity changes. The effect of IR stimulation on the thermoluminescence (TL) signal and that of preheating on IRSL intensity were examined; the results are inconclusive with respect to thermal stability, but are not inconsistent with the idea that the data do not reflect depletion of an electron trap. The IR50-signal measured after a preheat of 60 s at 115 °C behaves well in the SAR protocol, although it suffers from anomalous fading. Assuming that the signal is thermally stable, the fading-corrected ages suggest that deposition occurred during the end of the Late Pleniglacial and the early Late Glacial, which is consistent with geological expectations. Our observations demonstrate that IRSL dating of feldspar holds potential for establishing a chronology of fluvial dynamics of the Tisa River in N Serbia. Further methodological investigations are desirable; however, as issues relating to the stability and resetting of the IRSL signal remain to be resolved. 相似文献
13.
Although the OSL signal sourced from quartz is expected to be more stable and bleached more rapidly than the IRSL signal sourced from feldspar in a general sense, the former is much less investigated than the latter for rock surface related luminescence dating. It is mainly due to the difficulty in isolating quartz-dominated OSL signals from rock slices, and the low sensitivity and non-fast component dominated OSL signals for quartz in most of rocks. In merit of the sub-conduction band transition of trapped electrons of feldspar under both green light stimulation and IR stimulation at elevated temperature (Jain and Ankjӕrgaard, 2011), it is expected that the contribution of feldspars to the green light stimulated luminescence could be substantially reduced by a prior IR stimulation at elevated temperature. Meanwhile, more fast-component dominated quartz OSL signal (if there is any) could be obtained by green light stimulation (Bailey et al., 2011). Therefore, in this study, we investigated the feasibility of using the post-IR pulsed green stimulation, which is performed at 25 °C (PGLSL25) following two IR stimulations (IR50IR225), to isolate the quartz-dominated OSL signals from rock slices of granite cobbles for burial dating. The decay characteristics of stimulation curve, characteristic saturation dose and thermal stability of the pIR50IR225 PGLSL25 signal suggest that this signal is quartz-dominated, but still not fast-component dominated. We tentatively validated the equivalent dose (De) measurement protocol by dose recovery experiment. The luminescence-depth profiles show that the bleaching depths of pIR50IR225 PGLSL25 signals are slightly smaller than or close to that of the IR50 signals, while they are much shallower for the pIR50IR225 signals. The pIR50IR225 PGLSL25 procedure enables multiple De values determined from luminescence signals, with different bleachabilities and stabilities, from both feldspars and quartz in one measurement, which is of potential for buried age dating of cobbles. 相似文献
14.
Zhixiong Shen Barbara Mauz Andreas Lang Jan Bloemendal John Dearing 《Quaternary Geochronology》2007,2(1-4):150-154
Optically stimulated luminescence of fine silt quartz was investigated to establish chronologies for lake sediments from the British Isles. Feldspar contamination and its potential effects on equivalent dose (De) determination were examined. A new feldspar contamination test based on the thermal quenching of quartz OSL and thermal assistance of feldspar OSL identified feldspar contamination in samples being treated for 20 min in 20% hydrofluoric acid. Feldspar component monitoring based on the post-IR OSL/OSL ratio was not sufficiently sensitive to monitor a feldspar component, but is a good indicator whether a standard SAR procedure can be applied successfully, despite the presence of feldspar. Based on these results we used a modified SAR protocol including a 100 s IRSL stimulation at 50 °C before OSL readout. This protocol could overcome any malign effects of feldspar even for a feldspar bearing polymineral sub-sample. 相似文献
15.
One of the most important foundations of luminescence dating is the assumption that the growth of the luminescence signal in nature can be reproduced under laboratory conditions by performing irradiations with a calibrated beta or gamma source. When optically stimulated luminescence (OSL) of quartz with a dominant fast component is measured using the single aliquot regenerative dose (SAR) protocol, laboratory dose response curves that display continuing growth at high doses are increasingly reported in literature. In this study we investigate fine (4–11 μm) and coarse (63–90 μm) quartz extracted from 25 samples taken from L1, S1 and L2 units from the loess-palaeosol section at Costineşti in Romania. Our results indicate that the growth of the OSL signal in nature does not correspond to the laboratory generated laboratory dose response curve. The growth of the signal in nature is consistent with a single saturating exponential function, with the signal of coarse grains starting to saturate at 100–200 Gy, and for fine grains at 200–300 Gy, respectively. Laboratory dose response curves continue to grow for high doses (>300 Gy) for both quartz fractions. The differences observed between the natural and the laboratory dose response for the two quartz fractions are believed to be a cause for the different chronologies previously reported using the two grain sizes of quartz on Romanian loess. In addition, we have applied the single aliquot regeneration and added dose (SARA) procedure to both fine and coarse grains from the youngest sample. Our findings question the reliability of obtaining high equivalent doses for quartz samples displaying laboratory dose response curves obtained by the SAR protocol for which a single saturating exponential model does not describe the data. 相似文献
16.
When measuring samples from southern Peru, we discovered an age offset between feldspar infrared-stimulated luminescence (IRSL) and quartz optically stimulated luminescence (OSL) ages. This age offset was not only found in these particular samples but was also observed in samples from a range of geographical localities. Extensive analysis revealed that it is actually the quartz age that underestimates the true depositional age, and this is due to a very weak fast component combined with other thermally unstable OSL signal components. We discuss properties of these poorly behaving samples and how to detect such samples prior to the OSL single-aliquot regenerative-dose (SAR) measurement. Finally, existing approaches to improve equivalent dose (De) determination are discussed for samples from southern Peru. 相似文献
17.
We simulated the variability in measured quartz optically stimulated luminescence (OSL) signals and dose response curves (DRCs) caused by measurement uncertainties, including counting statistics and instrumental irreproducibility. We find that these measurement errors can give rise to large variations in the observed luminescence signal and contribute to among-aliquot or among-grain scatter in DRCs and equivalent dose (De) values. Different measurement systems (i.e., luminescence readers) may have different counting statistics properties and, hence, may exhibit differing extents of variation in the observed OSL signal, even for the same sample. Our simulation shows that the random measurement uncertainties may result in some grains or aliquots being ‘saturated’ (that is, the measured natural signal is consistent with, or lies above, the saturation level of the measured DRC) and that the rejection of these ‘saturated’ grains may result in a truncated De distribution, with De underestimation for samples with natural doses close to saturation (e.g., twice the characteristic saturation dose, D0). We propose a new method to deal with this underestimation problem, in which standardised growth curves (SGCs) are established and the weighted-mean natural signal (Ln/Tn) from all measured grains is projected on to the corresponding SGCs to determine De. Our simulation results show that this method can produce reliable De estimates up to 5D0, which is far beyond the conventional limit of ∼2D0 using the standard SAR procedure. 相似文献
18.
The success of optically stimulated luminescence (OSL) dating relies to a large extent on suitable characteristics of the analysed mineral, in this case quartz. Previous OSL dating of Quaternary sediments in Scandinavia has shown that quartz characteristics vary widely across the region, resulting in dating studies with varied success. The aim of this study is to provide an overview of quartz luminescence characteristics in Sweden and Norway, evaluate their effect on dating results and discuss the underlying causes of their variability.A qualitative assessment of luminescence signal characteristics of quartz from Late Quaternary sediment deposits, from a range of geological and geographical settings, has been made by re-analysing data from samples previously dated at the Lund Luminescence Laboratory, Sweden. This allowed a general characterisation of signals and a study of the relationship of these properties to dating result ‘quality’. To quantify the results, selected samples were further analysed with single-grain measurements and with small aliquots.The results show that the average luminescence signal from quartz is fairly dim but dominated by a fast signal component and changes little during measurement. Dose determination precision is ∼4% for 8-mm aliquots and ∼6% for 2-mm aliquots. However, the luminescence signal characteristics have a spatial variation across Sweden and Norway, which appears to correlate with large-scale bedrock units. In areas of sedimentary bedrock outside the Scandinavian mountains and within the Blekinge-Bornholm province, the quartz is brighter and has a stronger fast signal component, while in the Caledonian orogenic belt, the signal is very weak and lacks a fast component. These differences lead to a range in precision of doses, from ∼2% to >40% (for doses in the order of 5–400 Gy), and in the number of rejected aliquots (0–100%) depending on location, but also implies that quartz luminescence can be used as a provenance indicator in part of Sweden and Norway. 相似文献
19.
Luminescence dating has become a key tool in studies of the Quaternary. The typically stable luminescence response of quartz grains and the absence of a significant internal dose, make quartz minerals the preferred dosimeter for monitoring the burial dose in sediments. Unfortunately, the reliability of conventional OSL (optically stimulated luminescence) dating, based on blue stimulation, can be compromised when the luminescence decay is not dominated by a rapidly decaying and stable part of the luminescence signal (i.e. the fast component). On the other hand, standard methods in luminescence dating are limited to ages of a few hundred kiloyears. In this study, violet stimulated luminescence (VSL) has been used as a means to overcome both problems, applied to a series of colluvial deposits in the Atacama Desert, Chile. Quartz from this region, characterized by poor blue-OSL response, showed a reproducible and stable VSL signal capable of recovering given doses up to ∼500 Gy and a saturation dose twice as high as conventional OSL. The VSL response from these samples has been studied in detail and the estimated ages have been compared with an already established chronology for the same site, based on IRSL of potassium feldspar single grains. Results agree for the dose range of the profile studied, ∼100–250 Gy, equivalent to ages of 29–79 ka confirming the suitability of VSL for dating sedimentary quartz with unreliable blue-OSL response and to extend the age range of conventional OSL dating. 相似文献
20.
S.C. Packman B. Mauz D.-D. Rousseau P. Antoine J. Rossignol A. Lang 《Quaternary Geochronology》2007,2(1-4):39-44
Six samples were collected from a section of Peoria Loess in Eustis, North America, for optically stimulated luminescence (OSL) dating of quartz, and all except one (LV90) produced narrow dose distributions. A comparative study was conducted on this sample and on a ‘well-behaved’ sample (LV91), involving other dating methods and examination of the quartz OSL. These investigations revealed differences in the quartz OSL growth with dose, OSL response to thermal treatments and the range of components within the OSL signals. An ultra-fast component was found in LV90 that displayed a higher rate of sensitivity change than the fast component and this had a malign influence on the determination of the equivalent dose. The distinctive luminescence characteristics of LV90 imply either a change in wind dynamics and/or the source area for the silt. 相似文献