Thermoluminescence dating of coarse-grain quartz from the Malan loess at Zhaitang section, China

Thermoluminescence (TL) ages were obtained for five loess samples taken from the Zhaitang section near Beijing, China, using the coarse-grain quartz technique. The paleodose values have been determined by the method of total sample bleaching and regeneration of the TL growth curve. The method appears to be suitable for the age determination of loess samples up to about 150,000 yr where the annual dose-rate values are of the order 3–4 mGy/yr. This limit is a function of the total accumulated dose. The ages are in good agreement with those obtained by a fine-grain TL technique and are consistent with geological and geomagnetostratigraphic evidence.     

TL dating of loess in China

TL ages of 56 loess samples collected from Xinjiang and the middle reaches of the Yellow River were determined by using fine-grained quartz and man-made light source bleaching techniques.The results indicate that :1.The well-preserved loess sections in Xinjiang began depositing 400000 a ago.The loess/paleosol series may be comparable with that observed in the middle reaches of the Yellow River but the depositing time was probably delayed by 30000-50000a.2.The bottom boundary age of the Malan loess varies from one place to another.The TL dates can be divided into two group:70000-130000 a and 30000-50000 a.The TL data are con-sistent with the appearance of two warmer climate periods since the Pleistocene,indicating obvious regional differences in stratigraphic development of loess,i.e.,paleosol occurred in the warm climate period in the same location,but loess was deposited in other locations.The initial age of loess deposition tends to become older from west to east and from south to north .In contrast ,the cold cli-matic belt showed an opposite trend.The TL ages of loess provide strong evidence for the Quaternary stratigraphy throughout geological times and the shift tendency of climatic belt.3.The depositing rate of the Malan loess along the middle reaches of the Yellow River varies from place to place but the TL age shows a linear relationship with the depositing thickness.The de-positing rate of loess in the north is higher than that in the south,suggesting that loess materials are derived from desert areas of northern China.     

Morphoscopy and morphometry of quartz grains from loess and buried soil layers

A complex method is suggested for the study of surfaces of sand grains. With this method, middle- and late Pleistocene loess-palaeosol sequences of the Russian Plain, Dnieper Basin, were studied. Surface texture of grains pointed to a dry and cold climate for their formation. During deposition of loess layers predominantly aeolian and cryogenic processes formed the grain surfaces. During interglacial and interstadial periods chemical weathering dominated.     

Towards single grain ESR dating of sedimentary quartz: first results

In optically stimulated luminescence dating, apparent ages of individual grains are thought to reflect a wide distribution of initial bleaching levels in hard to bleach sediments. Although having a larger age range (up to 1 Ma and beyond), this approach has not been used yet in electron spin resonance (ESR) dating. Here we report on the first results of ESR measurements on single sedimentary quartz grains. Initial bleaching levels are evaluated for two different River Meuse deposits in Limburg, NE Belgium. Measurements were done with a Q-band ESR spectrometer on transparent quartz grains of sufficiently large diameter (0.5–0.7 mm). Single crystal ESR properties were used to identify different ESR active centres. In about 50% of the selected grains an Al and/or Ti–Li signal was detected and the latter has been selected for further measurements. Artificial bleaching experiments show a strong signal decrease with UV light exposure. After gamma-ray irradiation, a number of different signal intensity vs. artificial dose curves could be observed: exponential growth, exponential saturation, linear, with inflexion points, and unclear ones. Many grains show increasing ESR signals with doses up to 1000 Gy, suggesting that the age range could be extended over 1 Ma, covering the Middle Pleistocene and part of the Early Pleistocene. Accumulated doses of individual grains were calculated using the additive dose method. The results show a large dose distribution of individual grains for both deposits. It is concluded that insufficiently bleached grains can be detected using single grain ESR measurements of sedimentary quartz in a fluvial environment.     

江西新余第四纪冲积物石英的电子自旋共振年龄测定结果

新余市南英地区第四纪冲积物发育齐全,属侵蚀阶地保存（图１）,由老到新划分为赣县组、进贤组、莲塘组和联圩组。最近对各组底部砾石层填隙物分别进行了石英粉砂的电子自旋共振（ＥＳＲ）年龄测定。１岩石地层单位简介（１）赣县组（Ｑｐｇ）：原称赣县砾石层,系陈国达、刘辉泗于１９３９年创立的,创名地是赣县江口镇三团。本组下部为灰白色砾石层;中部为桔红色含砾粉砂;上部为桔黄色粘土。下与老第图１新余市南英袁河Ⅰ至Ⅳ级阶地地貌剖面图Ｆｉｇ．１ＧｅｏｍｏｒｐｈｏｌｏｇｉｃａｌｐｒｏｆｉｌｅｏｆｔｅｒｒａｃｅｓＩｔｏＩＶ…     

ESR dating of quaternary tephra from Mt. Osore-zan using Al and Ti centres in quartz

Quaternary tephra of Mt. Osore-zan was dated by electron spin resonance. Quartz grains were separated from the tephra and ESR signals of Al and Ti centres were measured at 77 K. The signals of Al and Ti centres which have a complicated hyperfine structure were simplified by using wider field modulations width (5 gauss) than usually used (0.5–1 gauss). The influence of 5 gauss modulation width on the measurement of the signal intensity of Al and Ti centres was investigated. The intensity of the signal increases linearly with gamma irradiation and total doses obtained were 178 to 273 Gy and ESR ages were 0.19 to 0.32 Ma. These ages agree with the estimated age of about 0.3 Ma from the correlation of volcanic ash and terrace level.     

石英ESR测年法在第四纪陆相沉积物测年中的应用

电子自旋共振（ESR）测年法是近40年来逐步发展起来的第四纪年代学方法。由于它的测年范围宽、测年物质种类多等优点,特别是对于老于20万年的早中更新世没有火山灰等定年物质的样品,有着特殊的优势,引起了第四纪研究者的关注。近年来,随着对ESR法基本原理认识的深入和实验技术的提高,在测年信号心的热稳定性、晒退回零特性、辐射剂量-信号增长特性、测年可靠性等方面的研究均取得了较大进展。本文结合国内外在ESR法基础原理、测年应用等成果,简要回顾了ESR法的历史发展,以及不同信号心在第四纪地质研究中的成功应用。     

Fracturing mode analysis and relative age dating of faults by surface textures of quartz grains from fault gouges

Surface textures of quartz grains taken from about 250 samples of fault gouges in faults ranging in length from several metres to several tens of metres with the faults extending several tens to several hundreds of kilometres in length, are examined by means of the scanning electron microscope and are categorized into four groups from I to IV, based on the smoothness of the surface, degree of undulation and development of cavities, as mentioned in a previous paper. Based on surface features of quartz grains from faults the geological age of movement of which is known, the groups I to IV are tentatively related to the age of formation of quartz grains and the period of formation of surface textures. This correlation makes it clear that quartz-grain surface textures are an important clue to dating a relative age of faulting. River patterns, striations, granular fracture surfaces, and dimple-like textures are observed to appear on less corroded surfaces of quartz grains from fault gouges. Fractographic analysis of these surfaces of quartz grains should be a clue to revealing the mode of fracture of the fault movement which released the quartz grains into the fault gouge.     

Fatigue effects in quartz sand grains

Particles of quartz sand from a stream draining granite were found to exhibit noteworthy effects of fatigue. Both repeated static loading and collective movement in water weakened the particles markedly. This weakening must have significance in nature, where repeated stressing occurs in many environments, particularly in soils and during bed-load motion in both air and water. Tectonic movements may also create fatigue effects in sand grains. Fatigue effects appear also to be sufficiently pronounced to be significant in some industrial processes involving the use of sand.     

中国北方沙漠石英δ18O值的初步测定与分析

石英是岩石、沉积物中最常见的矿物之一,它的化学性质稳定,硬度大。在风化剥蚀、搬运、沉积和埋藏条件下,石英中氧同位素与外界环境氧同位素交换非常弱,即石英的δ¹⁸O值基本保持不变。因此,石英δ¹⁸O值被应用于气溶胶、黄土-古土壤堆积序列、日本和夏威夷土壤、深海沉积物的物源区的研究中。但是用石英δ¹⁸O值来探讨沙漠物源的报道尚不多,笔者在此选择位于内蒙古西部的巴丹吉林沙漠为重点研究区,对比分析浑善达克沙地、呼伦贝尔沙地、非洲南部的卡拉哈里沙漠沙丘沙石英δ¹⁸O值,试图探讨沙漠石英δ¹⁸O值与粒径、物源的关系。石英δ¹⁸O值分析测定的实验步骤如下^[1～3]:1)从每个     

Glacially crushed quartz grains in loess as indicators of long-distance transport from major European ice centers during the Pleistocene

Detailed mineralogical analysis of the fine and very fine sand fractions (63–250) in the Dreihausen Loess Sequence shows the presence of numerous glacially crushed grains, including a significant amout of quartz. Previous theories regarding the origin of loesses in central Germany held that all sediments were derived locally, following short-distance transport from nearby sandstone outcrops. New data presented here show that many quartz and feldspar grains were glacially crushed, weathered, crushed again, transported, and emplaced by aeolian processes at Dreihausen. Crushing features observed are compatible with transport in both continental and alpine glaciers; some clasts show the effects of abrasion by both water and ice transport, while others are partly rounded presumably by fluvial and/or aeolian processes. Stronger palewind systems during the Pleistocene presumably contributed to the transport and emplacement of glacial grains from ice centers in both the Alps and the Baltic areas, and also possibly from the Rhine Basin.     

Electron irradiation damage in natural quartz grains

The effect of electron irradiation on defects in natural quartz grains has been studied using strong-beam and weak-beam transmission electron microscopy (TEM) techniques. Damage is visible soon after the sample is exposed to the electron beam. The defect centers grow with increased irradiation, but the density of centers is independent of electron dose. Dislocation images also widen during irradiation; the rate of widening is independent of Burgers vector and dislocation nodes widen without constriction. Both of these observations indicate that the widening of dislocation images is related to vitrification of the material in the vicinity of the dislocations rather than irradiation-assisted separation of partial dislocations. This interpretation is supported by observations on grain boundaries.     

Description and ESR dating of the Holsteinian interglaciation

The classical region of the Holsteinian interglacial is in the vicinity of Hamburg and the Lower Elbe. It is defined on the basis of pollen and is clearly distinguishable from the Eemian interglacial (Hallik, 1960; Müller, 1974). The Holsteinian interglacial is represented by a sequence of sediments up to 100 m in thickness. These consist of limnic, fluvial, and marine beds and show a transgression up to the height of present sea-level.Twenty-seven molluscs from Holsteinian deposits were used for ESR dating. The ages show that the Holsteinian may be correlated with stage 7 of the deep sea record V28-238 (Shackleton and Opdyke, 1973).     

TL dating of malan loess in gansu province

TL dating technique is of great advantage for determining the initial time of storing energy (T₀) in an object to be analyzed. The sample is required to have undergone at least one thermal event, permitting all the residual storage to release. As a result, TL dating technique has found wide application in geochronology of pottery. The determination of T₀ of loess is mainly based on the fact that fine particles of which loess is composed will lose their storage in the process of transportation by wind. In our experiment TL dating technique was adopted to determine the ages of fine quartz grains, and the results were corrected for those of shine-fading experiment. TL dating of Malan loess specimens from Mt. Gaolanshan, Liugouhe near Lanzhou, Mt. Qijiadashan in Jingning and Baichaoyuan in Huining gave the age values of 2.6±0.1, 3.6±0,3. 4.7±0.5 and 10.0±0.6×10⁴ yr, respectively. The values indicate that the Malan loess began depositing in Late Pleisotocene, but the initial time and acumulation rate are different under different morphological conditions from place to place.     

Luminescence sensitivities of quartz grains from eolian deposits in northern China and their implications for provenance

The thermoluminescence (TL) and optically stimulated luminescence (OSL) sensitivities of quartz grains from deserts and loess–red clay sequences are used to trace eolian provenances in northern China. Our results indicate that the 110°C TL peak and OSL sensitivities of quartz grains show differences among Chinese deserts, which can be subdivided into four groups according to the spatial variations of luminescence sensitivities. Such differences are related mostly to the regional difference in rock types of mountains surrounding or adjacent to the deserts. We also examine the possible provenance changes between the Quaternary loess and the Tertiary eolian red clay, and the results indicate that the luminescence sensitivity of Tertiary red clay is higher than that of Quaternary loess (L1, L15, and L33), implying source materials of the eolian deposits changed relative to those of the Quaternary.     

Chronology and the upper dating limit for loess samples from Luochuan section in the Chinese Loess Plateau using quartz OSL SAR protocol

Luminescence dating of loess older than 100 ka has long been a challenge. It has been recently reported that, using optically stimulated luminescence (OSL) of fine-grained quartz (4–11 μm) extracted from loess, the range of luminescence dating could be pushed to 0.6 Ma with OSL ages being in agreement with independent ages [Watanuki, T., Murray, A.S., Tsukamoto, S., 2005. Quartz and polymineral luminescence dating of Japanese loess over the last 0.6 Ma: comparison with an independent chronology. Earth and Planetary Science Letters 240, 774–789]. The aim of this study is to provide a luminescence chronology (20 samples) for the standard Luochuan loess section, and to further examine the upper limit of quartz OSL dating for Chinese loess. The growth curve does not saturate at 700 Gy, and should allow reliable equivalent dose (D_e) determination up to at least 400 Gy. However, when compared with independent chronological control, the D_e that could be treated as reliable is less than 230 Gy (corresponding to 70 ka in age for Chinese loess), and the D_e larger than 230 Gy should be underestimated. Ages for samples from the lower part of palaeosol S1 are severely underestimated, with the maximum age of 95 ka for a sample from the bottom of this palaeosol, much younger than the expected age of 128 ka. The maximum D_e obtained for sample L9/M, collected from loess layer L9 which is below the Matuyama–Brunhes (B/M) boundary whose age is 780 ka, is only 403 Gy which corresponds to an age of 107 ka. The cause of underestimation is not yet clear. The previous results by Watunuki et al. (2005) on the extension of OSL dating of loess to 0.6 Ma is not confirmed. When evaluating the validity of OSL ages in S1, another possibility is to question the already established chronological frame for Luochuan section, which is based on the hypothesis of continuous dust deposition. The assumption of an erosion hiatus between L2 and S1 could make the OSL ages look reasonable. However, if this is the case, then it is difficult to explain why the age of sample L9/M is only 107 ka which could be treated as a saturation age, while the OSL can provide a correct age for loess as old as 94.9 ka for sample LC22 collected from the bottom of S1. Much work is required to clarify these confusions.     

Characterization of an ESR geochronological dating center in flints

A study of the ESR signal complex in flints was used to examine its origin within the mineral. One component of the ESR spectrum, known to be a trapped hole, was confirmed to be a structural defect of the silica fraction of flint. The relationship of this center to that seen in natural quartz and glass is discussed. The defect has importance for geochronological direct-dating as it is shown to anneal and regenerate in a systematic manner in flints.     

不同气候带花岗岩母质发育的土壤中石英颗粒形态特征研究

石英颗粒形态特征已被广泛用于土壤风化和侵蚀与古气候重建的研究。我国花岗岩空间分布极为广泛,气候、植被与土地利用多种多样,其发育土壤中的石英颗粒形态必然也存在差异。本研究选取了我国5类气候带下的花岗岩母质发育的典型土壤的表层样品,利用扫描电镜分析石英颗粒形态特征,旨在进一步揭示气候对石英颗粒风化的影响。结果表明：1）石英颗粒形态特征具有明显的规律性,表现为随着纬度的降低,石英颗粒的圆化程度及溶蚀程度均有所增强,机械特征发育减弱。2）基于石英颗粒形态特征建立的半定量特征统计指标更好地表现出了显著的地带性差异,其与地理纬度之间具有显著的相关性,也进一步证明了气候因子对石英颗粒形态特征的影响。

     

ESR测年技术在第四纪冰川年代学中的研究综述

近些年,宇宙成因核素暴露年代、光释光和放射性碳埋藏年代等方法在第四纪冰碛物的年代测定中已经取得显著进展.但对于第四纪冰川沉积物10万年甚至百万年以上的冰碛物样品的埋藏年代和暴露年代,由于方法自身问题或沉积物后期地质地貌过程的改造,使上述方法存在定年方面的挑战.而电子自旋共振（ESR）广泛的测年范围,使其在第四纪样品的测年中发挥着不可替代的作用.目前,石英ESR信号的衰退特征已有许多研究进展,但是对于冰碛物中的ESR信号的研究还很少.ESR测年方法由于缺乏测年机理的研究,西方学者和国内一些测年学者对这种方法的定年存有疑虑.因此,我们在典型冰川区开展对冰碛物中石英砂ESR信号变化的机理研究,得到人工研磨可以使ESR信号强度下降到原来值的53%~69%,但并不能使ESR信号完全归零.如果在以后的研究中能够找出这些残留信号值大小,并予以扣除,将会大大提高ESR冰碛物测年精度.在今后的研究中应探求其测年机理,提高测试样品的石英纯度,增强ESR测年信号的精度,使这种方法成为冰碛物交叉测年中独立可信的测年方法之一,为第四纪冰川研究中的老冰碛物的定年提供准确的年代依据.     

Optical dating studies of quartz and feldspar sediment extracts

Continuing developmental work into optical dating has led to some clarification of the optical behaviour of quartz and feldspar sediment extracts. We have verified the key assumption intrinsic to the method — that the optical signal is zeroed completely upon exposure to daylight. We also show that the rate of zeroing in optical dating is much more rapid than it is in TL dating.Studies concerned with the extraction of the thermally stable signal from laboratory-irradiated samples showed that problems may arise from medium-to-high-temperature preheating of young samples. Optical alternatives to thermal stabilization were tested using dye and krypton lasers. Using a krypton laser we have succeeded in obtaining an equivalent dose of 0.0 ± 0.7 Gy for the quartz from a modern intertidal sand, and an average dose of 120 ± 22 Gy for the feldspar extract of a 70 ka sand unit. Both were obtained using six wavelengths, from the infrared to the violet, and no dependence on wavelength was found. We found that the photon energies of infrared and deep red light can stimulate luminescence in unirradiated quartz and feldspar extracts of sediments. This was not expected, and suggests that the process of trap emptying is more complex than we had envisioned, but implies a far greater than expected degree of technical flexibility for the optical dating method.