黄土细粒样品红外释光与绿光释光测年对比研究

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。     

甘肃巴谢剖面黄土-古土壤的光释光测年研究

光释光（OSL）测年是测定第四纪沉积物年龄的一种新技术。它通过单色光束激发使晶体中储存的电离辐射能释放出来。与热释光（TL）测年相比，OSL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。本文用细颗粒光释光技术对甘肃巴谢剖面的黄土-古土壤进行了测定，其测年结果与14C测年结果相吻合。这表明，光释光是一项极潜力的年代学技术。     

晚第四纪湖泊演化光释光测年

在过去的20年里,光释光（optically stimulated luminescence,简称OSL）测年技术发展迅速,已经被广泛应用于第四纪沉积物的测年研究中。近年来,以OSL技术为主要定年手段,利用其测年范围大、测年材料（石英和长石）丰富且易于提取等优势,在我国干旱/半干旱区（腾格里沙漠古湖、内蒙古黄旗海等湖泊）开展了一系列晚第四纪湖泊演化和古气候环境变化的研究工作。高水位湖相阶地的OSL测年结果表明,晚更新世高湖面事件发生时间在MIS 5阶段甚至更老,对基于14C数据建立的“MIS 3a大湖期”假说的年代框架提出了质疑;通过东北兴凯湖晚第四纪连续湖泊沉积物的高分辨率OSL和14C测年对比研究,从年代学机理上揭示晚更新世高湖面的年代学争论主要源自14C技术测定较老样品时的局限性,14C测年手段及易造成老于30000年的沉积物年龄的低估;来自青藏高原东北缘的秦王川盆地和东北地区兴凯湖湖岸的风成沉积也记录了MIS 3a阶段可能不存在气候湿润和高湖面事件;另外,通过对白碱湖古湖岸堤的OSL测年,建立了湖面波动过程和全新世区域湿度变化历史,揭示了季风边缘区早中全新世湿润期和中晚全新世以来逐渐干旱化的气候环境变化过程。综上所述,相较于传统的14C技术,OSL测年技术在湖泊沉积物的应用中具有诸多优势和潜力。尽管如此,OSL测年方法在实际应用过程中会遭遇一些会影响测年结果的潜在的技术问题。因而本文也从石英组分的长石污染、沉积物沉积前OSL信号的曝光程度、铀系不平衡和含水量以及宇宙射线对剂量率的动态影响等多方面,综述了水成沉积释光研究中面临的具体问题,并提出了初步解决方案和建议。     

第四纪沉积物光释光测年中等效剂量测定方法的对比研究

准确地测定碎屑矿物沉积后吸收的等效剂量第四纪沉积物释光测年中最关键的一环。用光释光测年技术对几年全新世坡积物,古土地和黄土等样品中的石英,长石等碎屑矿物进行了测定等效剂量的对比研究。     

郑州邙山马兰黄土的光释光(OSL)测年初步研究

对郑州市西北邙山黄土塬赵下峪(34°58'N,113°22'E)剖面上部马兰黄土(厚约87m)不同层位的24个样品作了细颗粒(4-11μm)组分红外释光(IRSL)测年,其中8个样品同时进行了细颗粒组分绿光释光(GLSL)测年。样品的IRSL和GLSL信号强度都在Daybreak1100TL/OSL检测系统中测量。该系统的本底计数为70-80光子/秒。被检测的IRSL和GLSL波长分别为340-480nm和340±25nm;激发光束波长分别为880±80nm和514±14nm,功率为18mW和15-16mW。所有样品的等效剂量都用再生释光法测定;环境剂量率是通过测定样品的铀、钍和钾含量,按Aitken(1985)的转换系数确定的,考虑了含水量的影响及宇宙射线的贡献。从这批样品的光释光测年结果可得以下初步认识:
(1)8个样品细颗粒组分的IRSL和GLSL测定的等效剂量和年龄值,除1个样品外,都在1-2σ范围内一致。这可能提供了沉积物光释光测年可靠性的一种自检方法。(2)邙山剖面马兰黄土不同层位段的沉积速率变化十分显著,从0.4m/ka到5.6m/ka,并与剖面上质量磁化率测定值的变化大致相吻合。该剖面马兰黄土至少有4个快速堆积层(沉积速率>3m/ka),其磁化率低而变化小;3个缓慢堆积层(沉积速率<0.5m/ka),其磁化率大或变化显著,它们之间有一系列过渡层。(3)邙山马兰黄土大体可三分即上部(L_1-1)埋深2.7-27.5m,中部(L_1-2)埋深27.5-57.9m)和下部(L_1-3)埋深57.9-87.9m。它们的形成年代分别为10.8-36.2ka B P,36.2-70.3ka B P和70.3-80.2ka B P。较详细的黄土-古土壤序列年代表将在文中讨论      

浑善达克沙地的光释光测年研究

光释光测年技术以光可以使在半导体结晶固体中被俘获到光敏陷阱中的电子释放出来这一原理为依据,以样品在被覆盖前,它们的光释光信号都已经晒退回零为假设前提进行测年的。而风成沉积物是最符合这一假设的,所以光释光测年对于风成沉积物非常适合。本文对采自浑善达克沙地样品中的石英粗颗粒进行光释光测年,试图重建沙地的古环境演化过程。本文研究的样品分别采自浑善达克沙地的中部SG点(42°40'N,115°57'E)和东部YS点(43°14'N,116°49'E)。采样时,先挖大约30cm深,然后用锤子将金属小筒打入,拔出后,小筒用黑色塑料和胶带封死。到实验室后,小筒顶端大约1cm厚的样品用来测量     

汉江上游安康东段古洪水事件光释光测年研究

通过对汉江上游河谷广泛的野外考察,结合粒度和磁化率分析,证明汉江上游安康东段阶地剖面夹有两层典型的古洪水滞流沉积层,其记录了两期古洪水事件。选择该河段LSC两个剖面进行系统采样,对其进行了年代学和沉积学研究。应用单片再生法（SAR）光释光测年技术,获得其光释光年龄值,结合地层对比,确定这两期古洪水事件分别发生在距今13050~12270 a（对应BL+AL事件向着YD气候恶化事件转折阶段）和发生在距今1000~900 a左右,相当于我国历史上的北宋时代后期（A.D. 1000~1100）。通过与国内外多种高分辨率气候变化记录的对比分析,揭示了古洪水事件的发生与气候恶化转折时期,季风气候格局突变、气候波动不稳定、降水变率增大有密切关系,这对汉江上游水资源综合开发利用以及防洪减灾有着重要的意义。     

光释光测年中石英样品提纯方法的改进

为了解决光释光前处理中遇到的传统方法无法获得满足纯度石英的问题,通过大量对比实验,结合玻璃工艺中石英分离研究成果,最后获得了新的石英提纯流程,与传统方法相比,新方法通过化学分离避免了密度变化对石英长石分离的影响,从而解决了斜长石和岩屑在传统的重液分离中无法剔除的问题,新方法能够获得满足纯度要求和量要求的石英,同时,新方法比传统方法实验室工作效率更高。     

亮绿SF-过氧化氢体系催化动力学光度法测定痕量钒

在硫酸介质中,痕量钒(Ⅴ)能明显催化过氧化氢氧化亮绿SF褪色,通过研究该反应的最佳实验条件和动力学参数,建立了测定痕量钒的新催化动力学光度法。该方法选择性强、操作简便、快速,其线性范围为0.0~40ng/mL,检出限为5.2ng/L。方法用于水样及茶叶中痕量钒(Ⅴ)的测定,结果满意。     

Metamerism Appreciation of Jadeite-Jade Green under the Standard Light Sources D65, A and CWF

We tested 288 pieces of the polished cabochon jadeite-jade with high quality green and smooth surfaces using the colorimeter Color i5 based on the CIE 1976 L~*a~*b~* uniform color space. The color changes after alternating three CIE standard light sources D_(65),A and CWF were compared,and the degree of metamerism was evaluated. The results show that the CIE standard light sources D_(65),A and CWF increase the chroma of green and turn bluish green into vivid green,which are similar or to nearly colorless and transparent glass-like samples with fine textures. When the three light sources were individually alternated,the lightness of the jadeite-jades showed little change,but the tone changed significantly. Metamerism occurred only in 3 pairs among the 16 samples that were selected by cluster analysis for quality,and the metamerism colors were highly consistent of L~*D_(65)∈(43.47,46.75),C~*D_(65)∈(65.20,68.80) and ho~*D_(65)∈(138.10,140.23). We can conclude that the jadeite-jade green gradually turns to blue when the color temperature of the light source increases. But when considering both the light sources and the samples,D_(65) is more suitable to be the light source of jadeite-jade green when compared with the light sources CWF and A. Compared with the CIE standard green and high chroma green,high-quality jadeite-jade green has a slight yellow tone,low lightness and high chroma. The special metamerism index decreased to 1 when the light source alternated among D_(65),A and CWF. Therefore,the color of jadeite-jade green might be slightly influenced by alternating of the light sources.     

北京平谷山前河流阶地发育序列、形成时代及地质意义

河流阶地是研究河流演化、构造运动的良好载体, 虽然北京地区第四纪地质研究程度较高, 但北京东部地区对河流阶地的相关研究资料较少。本文以北京平谷燕山山前发育的泃河、黄松峪石河、将军关石河为研究对象, 通过野外地质调查、光释光测年技术（OSL）详细划分了上述河流阶地的发育序列, 在此基础上讨论了部分河流阶地的形成时代、阶地成因及河流阶地对燕山隆升的响应等地质问题, 认为泃河南岸发育有3级阶地, 北岸发育2级阶地;黄松峪石河最多发育有6级阶地;将军关石河发育有5级阶地。将军关石河至晚形成于中更新世晚期（161. 7±7. 7 ka BP）, 黄松峪石河至晚形成于晚更新世早期（121. 2±5. 4~100. 3±4. 1 ka BP）, 泃河至晚形成于晚更新世中期（79. 4±3. 3~70. 8±3. 4 ka BP）。泃河、黄松峪石河、将军关石河各级阶地的形成受到了古气候变化和燕山隆升的双重影响, 平谷地区燕山在中更新世晚期以来, 一直处于隆升的状态, 晚更新世早期时隆升速率达到最大, 可达0. 24~0. 34 mm/a, 晚更新世中期时隆升速率降低, 0. 18~0. 24 mm/a。以上成果对研究北京东部河流阶地发育特征、形成时代具有重要参考价值, 也为中更新世晚期以来燕山的隆升提供了新的证据。     

单颗粒释光测年技术及其在地质考古中的应用研究进展

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。     

Age and Provenance of Loess deposits on the Northern Flank of Tianshan Mountain

Abstract: The distribution, optically stimulated luminescence dating and granulometric properties suggest that the loess on the northern flank of Tian Shan should be divided into two types. One which is like mantle and is named type A, is located on the windward slopes and dated to about 54.5±5.73?Ka. The other, called type B, lies flatly on the terraces of the rivers or low hills and penetrated 30.8±2.05?Ka ago. Here we study the origin and the age of two types of loess, and a model of loess formation is proposed. The dust was entrained from the Gobi Desert located to the north of Tian Shan by the monsoon from Mongolia, obstructed by the high mountains and deposited on the windward slopes of the mountains. The rivers and flows then transported the aeolian loess to low terraces and piedmont alluvial plains.     

Optically stimulated luminescence ages of the Hengyu site and their implications for anthropogenic activities in the Fuzhou Basin,South China

The chronologies of few Neolithic sites in the lower reaches of the Min River of China have been well investigated for the middle to late Holocene. In this study, the Hengyu Neolithic site in Fujian Province, South China, which has significant archaeological remains, was dated using blue‐stimulated optically stimulated luminescence (OSL) and accelerator mass spectrometry radiocarbon (AMS¹⁴C) techniques. The results, comprising nine OSL and three AMS¹⁴C ages through the Neolithic sequence, provide new evidence towards understanding the relationship between environmental evolution and human activities in the middle to late Holocene in the Fuzhou Basin and coastal areas of South China. The ages of the site deposits vary from 6.83 to 1.67 ka and can be divided into two main phases: the Keqiutou–Tanshishan culture period and the Bronze culture period. In contrast, the persistent periods of ancient human activities at the Hengyu site seem to correspond to regional sea‐level changes and the East Asian winter monsoon as a secondary factor, which can affect human activities through sea‐level impacts. The warm and high sea level conditions provided a liveable environment for the ancient humans of Fujian and even South China. The ages of two building column bases are linked to the early stage of the Han dynasty, suggesting a potentially favourable habitation environment; that is, ancient humans occupied and settled this area for the long term within this time period, which is consistent with sea‐level changes and palynology records. Copyright © 2019 John Wiley & Sons, Ltd.     

Initiation and Development of the Late Cenozoic Uplift of Daluo Mountains, Northeastern Margin of the Tibetan Plateau

Daluo Mountains lie at front of the arcuate tectonic belt at the northeastern margin of the Tibetan Plateau, and are the landform boundary zone between the active Tibetan Plateau and the stable North China Craton. Studying of the late Cenozoic uplift evolution of Daluo Mountains is important for understanding the expansion mechanism of the northeastern margin of the Tibetan Plateau and its influence on the western North China Craton. In this study, the late Cenozoic uplift of Daluo Mountains is constructed from the development of the late Cenozoic alluvial fan around Daluo Mountains. The entire sedimentary sequence and framework of the fan was revealed by the newly obtained drilling core data. The cosmogenic nuclide, optically stimulated luminescence, and detrital zircon U-Pb dating results provide new evidences for discussion about the initial timing of the late Cenozoic uplift of Daluo Mountains and the key stages of uplift during the Pleistocene. The late Cenozoic alluvial fan at front of Daluo Mountains overlies a set of fluvial-facies strata; therefore, development of the alluvial-fan marks the start of late Cenozoic uplift of Daluo Mountains. The timing of this event can be constrained to ~4.64 Ma. Two extensive gravel layers (dated to ca. 0.76–0.6 Ma and ~0.05 Ma) developed during the Pleistocene, indicating two episodes of considerable uplift. This study provides a new time scale for the uplift and expansion of the arcuate tectonic belt at the northeastern margin of the Tibetan Plateau.