Testing the applicability of standardised growth curves (SGCs) for OSL signals of quartz grains from the Yangtze Delta,China     

《Quaternary Geochronology》2022

The standardised growth curve (SGC) technique has the potential to save instrument time for equivalent dose (D_e) determination when applying single-aliquot regenerative-dose (SAR) protocol during optically stimulated luminescence (OSL) measurements. In this study, we test the applicability of two commonly used SGC procedures for OSL signals of quartz grains from aqueous deposits of the Yangtze Delta in China, which have been reported for weak luminescence signals and suffering from partial bleaching. Multiple silt-sized and sand-sized fractions of quartz samples from eight cores are used to construct SGCs by test dose standardisation (TD-SGC) and least-squares normalisation (LS-SGC), respectively. Three strategies, i.e. region-specific (SGC_R), region with core-specific (SGC_R + C) and core-specific (SGC_C), are adopted to categorise these normalised data into different SGC datasets. The large variability of dose response signals is substantially reduced by the SGC procedures for most of these datasets. Hence, common SGCs for a variety of samples from the Yangtze Delta can be established, irrespective of their distinctive particle sizes and luminescence characteristics. The D_e values are then estimated using both TD-SGC and LS-SGC procedures for samples from a specific core. Comparing to the full SAR protocol, the TD-SGC procedure roughly gives reproducible D_e estimates lower than ∼100 Gy while the LS-SGC procedure derives generally consistent D_e estimates of up to ∼230 Gy. Although LS-SGC_C and LS-SGC_R + C procedures replicate the most consistent D_e values, the LS-SGC_R procedure performs better in efficiency with a slightly less accuracy. In addition to careful comparison of LS-SGC and full SAR procedures, we suggest that a synchronous ratio derived by the chosen regenerative dose and its response signal for re-normalisation can be used to predict the LS-SGC D_e reliability on samples from similar sedimentary environments.  相似文献   

热力剥离破碎岩石试验     

孙瑞民  赵秀绍  汤凤林  М.А.ЕМЕЛИН 《地质科技情报》2006,25(4):96-100

在莫斯科国立地质勘探大学实验室对热力剥离碎岩方法进行的试验研究表明,不同类型岩石(岩浆岩、沉积岩、变质岩)的抗拉强度均随加热温度的升高而降低,且降低幅度较大,因此钻进速度明显提高.岩石破碎的形式与温度有关,当温度为500～600 K时破碎是在组成岩石的矿物颗粒(晶粒)内部进行的;当温度超过600 K时,破碎是在矿物颗粒间进行的.技术比较先进并有发展前景的加热升温方法是火焰喷射法、电子束法、等离子法和激光法.影响热力钻进发展的主要问题是没有合适的加热升温装置和碎岩工具,建议对此进行研究和开发.  相似文献   

A comparative analysis of four kinds of polysaccharides purified from Furcellaria lumbricalis     

Yu Guangli  Yang Bo  Ren Weina  Zhao Xia  Zhang Junzeng  Barrow Colin 《中国海洋大学学报(英文版)》2007,6(1):16-20

Four kinds of polysaccharides (FA, FB, FC and FD) were extracted and purified from a red alga Furcellaria lumbricalis. Their monosaccharide composition, average molecular mass and structural feature were determined by gas chromatography (GC), high performance gel permeation chromatography (HPGPC) and Fourier transform infrared spectroscopy (FTIR), respectively. The results showed that FA and FB were composed of galactose (Gal), 3,6-anhydro-galactose (AnG) and 4-sulfated-galactose (G4S), which were structurally similar to β-carrageenan and κ-carrageenan. FC was composed of sulfated galactose and small amount of AnG, indicating that it was a hybrid-sulfated galactan. FD was composed of α-1,4-glucose and belonged to floridean starch. The respective yields of FA, FB, FC and FD were 4.84%, 33.74%, 8.76% and 13.5%, and the corresponding were 537 kD, 432 kD, 513 kD and 51 kD respectively. Owning to its high content (>60%) of polysaccharide, F. lumbricalis will be a good source of marine sulfated polysaccharide and shows its potential utilization in food and medicine.  相似文献   

A Bayesian hierarchical age model for optical dating of single grains of quartz     

《Quaternary Geochronology》2023

In optical dating, the last time that a sample of sediment was exposed to sunlight is determined by dividing its equivalent dose (D_e) by the dose rate. For single-grain dating, the sample D_e is based on the statistical analysis of the distribution of D_e values estimated for individual grains, whereas the dose rate is usually determined from measurements of the environmental radioactivity of the bulk sample, together with allowances for radiation sources internal to the grains and cosmic rays. Conventionally, the D_e and dose rate are measured and analysed separately to produce an estimate of the depositional age of a sample, but this approach may result in loss of information because distributions of single-grain D_e values are influenced by several factors. Existing statistical models do not incorporate all the key information contributing to age estimation, such as the pattern and scale of dispersion of single-grain D_e values and dose rates, the associated measurement uncertainties, the effect of natural variability among grains, and the outlier probabilities of D_e and dose rate estimates. Here we propose an empirical Bayesian hierarchical age model (BHAM) for optical dating of quartz samples that incorporates the above information to estimate their depositional ages. The BHAM is based on the implementation of standardised growth curve and L_nT_n methods to integrate information on the full distribution of single-grain D_e values, sources of measurement uncertainty, beta-dose heterogeneity (observed or modelled), and detection of outliers. We present the results of validation tests using data sets of optically stimulated luminescence measurements and dose rates obtained for quartz samples dated previously from Denisova Cave (Russia) and for simulated samples. We conclude that the BHAM represents a robust and flexible approach to dealing with data for single grains of quartz within a Bayesian hierarchical framework and is suitable for application to sediments deposited in a variety of depositional settings.  相似文献   

青藏高原可可西里库赛湖年纹层石英颗粒表面形态特征研究     

陈钰  刘兴起 《湖泊科学》2016,28(5):1123-1133

湖泊是风成沉积的理想载体,利用扫描电镜分析石英砂的表面微结构特征,可以用于判断石英颗粒被风或水流搬运的相对距离和湖泊的水动力条件,从而判断其沉积环境与演化历史.库赛湖位于青藏高原北部可可西里地区,是青海省沙尘天气频发的地区之一,为进一步证实库赛湖年纹层粗颗粒层的风成成因,以库赛湖沉积年纹层为研究对象,结合青藏高原北部典型沙丘沉积、库赛湖冰面风成沉积、典型河流沉积和库赛湖湖滨相水成粗颗粒沉积样品,利用扫描电镜对上述沉积物石英颗粒表面特征进行观察研究,并统计35种特征的出现频率.结果表明:库赛湖地区典型风成物石英颗粒表面具有圆形轮廓、中低浮雕、翻板、新月型撞击坑、球根状边缘、直形阶梯、弓形阶梯、碟形坑等微形貌特征;典型水成物石英颗粒表面具有V型撞击坑、小型和中型贝壳状断口、少量溶蚀坑等微形貌特征;库赛湖年纹层粗颗粒层石英颗粒表面具有圆形轮廓、低浮雕、翻板、新月形撞击坑、球根状边缘、碟形坑等明显风成特征,与研究区风成物的石英颗粒表面特征相似,而与研究区典型水成物的石英颗粒表面特征差别很大.因此,库赛湖年纹层中的粗颗粒层是由风成作用形成的.  相似文献   

叠合盆地储层油气包裹体GOI成因与应用探讨——以准噶尔盆地莫索湾地区为例   总被引：1，自引：0，他引：1  

谢小敏 曹剑胡文瑄  张义杰王绪龙  张越迁唐勇 《地质学报》2007,81(6):834-842

在准噶尔盆地莫索湾地区选取了5口具有不同油气显示级别的典型探井,通过对48块岩心样品作精细的储层油气包裹体GOI组成分析,尝试探讨了在复杂油气充注情况下,叠合盆地油气包裹体GOI组成的成因。结果表明,含油气流体的充注强度是主因。但由于油气成藏的多期复合、油气水界面的多期变迁,决定了我们在研究过程中不可以直接借鉴文献中提出的1%和5%等指标来判断油气水层,而是应该结合地质背景,首先仔细分析其成因,再深入讨论应用。文中利用GOI对莫索湾地区的油气运移进行了讨论,取得了良好效果,表明其在叠合盆地油气运移研究中具有一定应用前景。  相似文献   

Exploring the potential of luminescence methods for dating Alpine rock glaciers     

《Quaternary Geochronology》2013

Rock glaciers contain valuable information about the spatial and temporal distribution of permafrost. The wide distribution of these landforms in high mountains promotes them as useful archives for the deciphering of the environmental conditions during their formation and evolution. However, age constraints are needed to unravel the palaeoclimatic context of rock glaciers, but numerical dating is difficult. Here, we present a case study assessing the potential of luminescence techniques (OSL, IRSL) to date the inner sand-rich layer of active rock glaciers. We focus on the signal properties and the resetting of the signal prior to deposition by investigating single grains. While most quartz shows low signal intensities and problematic luminescence characteristics, K-feldspar exhibits much brighter and well-performing signals. Most signals from plagioclases do not show suitable properties. Luminescence signals far below saturation indicate distinct but differential bleaching. The finite mixture model was used to determine the prominent populations in the equivalent dose distributions. The luminescence ages represent travel times of grains since incorporation into the rock glacier and hence, minimum ages of rock glacier formation. Luminescence ages between 3 ka and 8 ka for three rock glaciers from the Upper Engadine and Albula region (Swiss Alps) agree well with independent age estimates from relative and semi-quantitative approaches. Therefore, luminescence seems to have the potential of revealing age constraints about processes related to the formation of rock glaciers, but further investigations are required for solving some of the problems remaining and reducing the dating uncertainties.  相似文献   

Millimeter and Submillimeter Emissions from Galactic and Extragalactic Photodissociation Regions     

Abdul Qaiyum 《Astrophysics and Space Science》2006,305(1):1-10

The galactic and Extragalactic photodissociation regions are primarily heated by photoelectrons ejected from the surface of interstellar dust grains by Far-ultraviolet (FUV) photons. But there is no direct mechanism to measure the photoelectric heating efficiency. To understand the role of dust grains in processing the Interstellar Radiation Field (ISRF) and heating the gas, we compare the intensities I _CII, I _CO and I _FIR for (² P _3/2→² P _1/2) & (J = 1→ 0) line emission of CII & CO at 158 μm & 2.6 mm and integrated far-infrared from number of photodissociation regions, HII regions, planetary nebulae, reflection nebulae and high latitude translucent clouds (HLCs). It is found that I _CII is linearly correlated with I _FIR. In the cold medium where cloud is exposed to weak radiations temperature is low and most of the cooling is due to [CII] emissions. As a result the ratio of I _CII/I _FIR provide indirect method to evaluate the photoelectric heating efficiency. For the neutral cold medium it is evaluated to be ∼0.028. The FUV radiation field G ₀ are estimated through the model calculation of I _CII and I _CO for different galactic and photodissociation regions. The intensity of FIR radiation I _FIR are well represented as 1.23×10⁻⁴ G ₀(ergs cm⁻² s⁻¹ sr⁻¹) almost same as estimated for HLCs by Ingalls et al (2002). Hydrogen density for each source has also been estimated.  相似文献   

Crystalline silicates in comets: How did they form?     

Joseph A. Nuth III  Natasha M. Johnson 《Icarus》2006,180(1):243-250

Two processes have been proposed to explain observations of crystalline silicate minerals in comets and in protostellar sources, both of which rely on the thermal annealing of amorphous grains. First, high temperatures generated by nebular shock processes can rapidly produce crystalline magnesium silicate grains and will simultaneously produce a population of crystalline iron silicates whose average grain size is ∼10-15% that of the magnesium silicate minerals. Second, exposure of amorphous silicate grains to hot nebular environments can produce crystalline magnesium silicates that might then be transported outward to regions of comet formation. At the higher temperatures required for annealing amorphous iron silicates to crystallinity the evaporative lifetime of the grains is much shorter than a single orbital period where such temperatures are found in the nebula. Thermal annealing is therefore unable to produce crystalline iron silicate grains for inclusion into comets unless such grains are very quickly transported away from the hot inner nebula. It follows that observation of pure crystalline magnesium silicate minerals in comets or protostars is a direct measure of the importance of simple thermal annealing of grains in the innermost regions of protostellar nebulae followed by dust and gas transport to the outer nebula. The presence of crystalline iron silicates would signal the action of transient processes such as shock heating that can produce crystalline iron, magnesium and mixed iron-magnesium silicate minerals. These different scenarios result in very different predictions for the organic content of protostellar systems.  相似文献   

Variations of some heavy minerals in recent beach sands     

A. B. Vistelius  M. E. Demina 《Mathematical Geology》1982,14(2):161-187

The influence of shape, size, and specific gravity of mineral grains on the variation of the content of these minerals in beach sands has been investigated for fixed conditions of sedimentation on the beaches of the Baltic Sea and Michigan Lake. The coefficient of variation was used as a measure of the variance. Linear models tested by the analysis of variance were applied and revealed that the shape of grains and the combined effect of the size and specific gravity are responsible for the main part of the variation.  相似文献