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1.
哈尔滨黄山黄土是东北地区黄土沉积的典型代表,其成因研究是恢复东北地区古气候和古环境的基础.为探讨松嫩平原地区中更新世晚期黄土成因问题,对具代表性的哈尔滨黄山黄土剖面进行系统、高分辨率的粒度和磁化率特征分析,并与哈尔滨现代沙尘沉降物、黄土高原典型黄土-古土壤、现代河流沉积物及大连市滨海黄土粒度特征进行对比.结果显示:黄山黄土粉砂级(10~50 μm)颗粒和黏土颗粒(＜5 μm)的平均含量分别是43.86%(主众数粒组)和23.40%(次众数粒组);各粒度参数的平均值为:分选系数标准偏差σ=1.83、平均粒径Mz=6.25φ、中值粒径Md=5.89φ、偏度SK=0.21、峰态KG=0.86、中值粒径Kd=2.01;粒度频率曲线以双峰态分布为主,且主峰突出;岩性三角投影图、粒度象(C-M图、L-M图、A-M图)投影图及粒度参数(Mz-σ、Mz-SK、Mz-KG)散点投影图与风成沉积物基本一致,但与河流沉积物差异明显;判别函数Y＜0.基于以上粒度特征分析表明哈尔滨黄山黄土为典型的风成成因. 相似文献
2.
对成都平原区内5个代表性的第四系剖面上的成都粘土进行了系统的粒度分析。结果表明,成都粘土以粉砂颗粒（5～50μm）为主,平均粒径约为7．1—7．3φ（7．4—6．6μm）,缺少粗尾,〉63μm颗粒的含量很少,以细颗粒物质为主,呈双峰分布。其粒度分布及粒度参数特征与北方黄土及甘孜黄土非常相似,而与河流相沉积物有很大差异,表明成都粘土属于风成堆积。根据光释光测年（OSL）结果,成都平原区的成都粘土是晚更新世中期至晚期末次冰期堆积物,其物质主体是远源的。 相似文献
3.
哈尔滨荒山黄土位于欧亚黄土带的最东端,毗邻亚洲大陆干旱带的东部边缘,对它的成因机制研究有助于我们深层次理解松嫩平原地貌-气候-粉尘堆积的耦合关系。然而,目前荒山黄土成因还存在认识上的不统一。我们通过野外观察及对哈尔滨荒山钻井岩芯进行粒度、元素地球化学组成和磁化率分析,进而探讨荒山黄土的成因机制。结果表明:荒山黄土的粒度组成以粗粉砂级(16～63μm)为主,粒度参数特征(平均粒径、中值粒径、标准偏差、偏度和峰态)、粒度像特征(C-M、A-M和L-M)、判别式函数及Kd值对荒山黄土风成成因的指示不明显; L1-L5黄土的元素地球化学组成也没有与受流水改造的L5次生黄土和黄土-古土壤序列下伏的河湖相沉积(荒山组)区分开;荒山黄土-古土壤序列的磁化率呈现出周期性高低变化的特征,与黄土高原典型风成黄土剖面具有较好的一致性;结合野外观察,荒山黄土具有均一沉积和垂直节理发育等风成黄土典型特征。本文运用整合的方法确定哈尔滨荒山黄土为风积成因。黄土的粒度和地球化学指标作为黄土成因机制的替代性指标存在一定的局限性,在实际应用中应当结合野外观察和磁化率等其他替代性指标共同使用,才能够从中提取正确的成因机制信息。 相似文献
4.
"巫山黄土"粒度特征及其对成因的指示 总被引：2，自引：1，他引：1
为了探讨"巫山黄土"的成因, 对剖面样品进行了粒度分析.结果表明: "巫山黄土"主要由 < 50 μm的颗粒组成, ＞50 μm的砂级以上颗粒平均含量为16.9%;作为风尘"基本粒组"的10~50 μm的粗粉砂平均含量达43.1%, 为众数粒组; 5~10 μm的细粉砂颗粒含量平均为14.5%;＜5 μm的粘土颗粒含量平均为25.5%, 为次众数粒组.粒度参数、频率曲线与典型风尘沉积物相似, 显示为典型的风积成因; 粒度参数的C-M、L-M、A-M图等粒度象分析及结构参数散点图与现代河流沉积物差别明显, 而与长江中下游分布的下蜀土却基本一致.判别分析结果绝大部分为负值, 显示了风积成因为主、个别层位受到水流作用改造的成因特征. 相似文献
5.
Geochemical, mineralogical and sedimentological studies on the Taklimakan Desert sands 总被引：7，自引：0，他引：7
Major-element composition, mineral composition and grain-size distribution have been studied for Quaternary aeolian sediments from the Taklimakan Desert, north-western China, together with the variation of chemical and mineralogical compositions of different grain-size fractions. Aeolian sediments from the Taklimakan Desert have higher ratios of feldspar/quartz and calcite/quartz, finer grain size, poorer roundness of quartz and feldspar grains and lower abundances of frosted quartz, than found in aeolian sediments from other deserts such as the Saudi Arabian Desert. In spite of these immature mineralogical and sedimentological features, the aeolian sediments from the Taklimakan Desert show low regional variations in major-element and mineral compositions and are homogenized. These observations confirm that two processes, glacial activity within surrounding mountains and aeolian activity at the Tarim Basin, are important in the homogenization of the Taklimakan Desert sands. Taklimakan Desert sediments are constantly and effectively supplied from basement rocks in the surrounding mountains by glacial erosion. The supplied sediments are further homogenized by aeolian activity in the desert and are partly blown away, serving as the source of Chinese aeolian loess. Compositional differences are observed between loess (mainly 10–40 μm particles) and the <45 μm fraction of the Taklimakan Desert sediments, as well as between loess and whole rock of the Taklimakan Desert sediments. These observations provide constraints for precise modelling of loess formation, and for assessment of the chemical composition of the upper continental crust based on the chemical composition of aeolian loess. 相似文献
6.
地表松散沉积物中不同粒级的颗粒蕴含着不同的信息,这种差异与其物质来源、搬运和沉积过程中的分选作用以及沉积后的风化作用等有关。因此,可根据沉积物中不同粒级颗粒地球化学特征与矿物组成的差异,进行沉积物物源追踪或沉积环境重建。选择青藏高原在气候和地貌方面具有典型意义的柴达木盆地、错那湖、雅鲁藏布江流域作为研究区,分别采集了这几个地区的沙丘沙、黄土、湖积物、冲积物、洪积物、残坡积物等地表松散沉积物样品,用干筛法将沉积物样品分为两个部分,粗颗粒部分粒径范围为≥75~500 μm,细颗粒部分粒径<75 μm。对上述粗、细颗粒分别进行稀土与微量元素、Sr-Nd同位素、轻矿物组成的实验室分析测试,并对沉积物中粗、细颗粒的测试结果采用古典多维尺度方法进行相似性分析。结果表明：青藏高原松散沉积物中粗、细颗粒在轻矿物组成、微量和稀土元素含量、稀土特征、元素参数等方面存在差异;细颗粒部分蕴含了更多的环境信息,富含容易受化学风化影响的黏土矿物以及硬度较小、容易被磨蚀的方解石等矿物。在物源示踪中不同气候区的沉积物细颗粒不宜进行直接比较,应根据样品的粒度分布情况优先选择合适的粗颗粒组分进行物源示踪。 相似文献
7.
对青海湖沉积物进行物质来源进行聚类分析, 并对周边风成黄土与现代湖泊表层沉积物进行粒度分析, 在此基础上, 以青海湖周边典型风成黄土作为风成组分端元, 以青海湖表层沉积物作为水成组分端元, 首次利用已知端元的粒度分布特征对青海湖沉积物中典型粒度分布进行拟合, 进而估算了其中风成和水成组分的比例。结果表明, 青海湖沉积物粒度分布特征可分为三大类:1.水成组分占主导; 2.风成组分占主导(风成黄土主导); 3.两者以不同比例混合。希望此方法能成为未来湖泊沉积物中不同组分的定量判据和古环境的解读提供新途径。 相似文献
8.
乌鲁木齐河流域的黄土研究 总被引：8，自引：1，他引：8
本文较详细地论述了乌鲁木齐河流域的黄土,对部分黄土样品进行了粒度分析和矿物鉴定,利用14C和热释光方法做了年龄测定,指出这个地区的黄土大部分是在晚更新世中晚期干旱、寒冷的气候条件下形成的,与马兰黄土相当,有一些后来受流水改造成为次生黄土。分布在河源末次冰期冰碛上的黄土主要形成于全新世,属于天山“托木尔型”黄土。 相似文献
9.
长江三角洲第一硬质黏土层成因是长期争论的问题。对上海市青浦区第一硬质黏土层全样粒度多元统计分析,并与南京周家山下蜀黄土、长江悬浮颗粒物对比,探索长江三角洲第一硬质黏土层成因。第一硬质黏土层机械颗粒组成均一,频率曲线呈正偏态、中等或尖锐峰形的双峰分布,频率累积曲线呈"S"型分布,具有风成沉积特性。粒度特征分析为沉积环境判别提供沉积学证据时,综合运用多元统计分析可以使分析结果更准确。聚类分析将硬黏土与典型风成沉积物下蜀黄土粒度分布归为一类,长江悬浮颗粒物单独为一类,表明硬黏土与下蜀黄土成因一致。下蜀黄土与长江悬浮颗粒物粒度参数判别函数,将绝大部分硬黏土样品判定为风成沉积。粒级—标准偏差曲线结合现代风场,显示硬黏土粒度特征存在高空西风和低空西北季风两个主控因子。表明长江三角洲第一硬质黏土层是由西风和西北季风控制的风成成因堆积物。 相似文献
10.
Baotian Pan Qingyu Guan Hongshan Gao Dongsheng Guan Fenliang Liu Zongmeng Li Huai Su 《Boreas: An International Journal of Quaternary Research》2014,43(1):121-131
The grain size of the loess‐like sediment in the Jinsha River Valley is essentially similar to that of typical loess, and it differs from that of the fluvial sediment in the Jinsha River area. We conclude that the loess‐like sediment is of aeolian origin, as is the loess of the Chinese Loess Plateau. The geochemical characteristics of the loess‐like sediment are similar to those of dammed lake and fluvial sediments in the same area, which is significantly different from those of the typical loess in NW China. The geochemical characteristics show that the loess‐like sediment originated from proximal materials. Combined with the grain‐size distribution pattern of the aeolian deposits, we suggest that the loess‐like sediment of the Jinsha River Valley originated from the dammed lake and fluvial sediments that accumulated in the valley. The local mountain‐valley wind circulation (especially the valley wind in winter and spring) provided the transport force for the loess‐like sediment. The presentation of the loess‐like sediment may indicate the appearance of the grassland and forest steppe and the beginning of the dry‐hot valley phenomenon. 相似文献
11.
东北平原东部天恒山钻孔的粒度特征及其对地层划分的指示 总被引：2，自引：2，他引：0
东北平原东部荒山剖面是我国东北地区的第四纪典型剖面,但针对该剖面的地层划分和成因的研究尚存在不同看法,对其开展详细的粒度特征研究有望对该剖面的地层划分和地层成因提供进一步的认识。通过天恒山（THS）钻孔对该区地层进行高分辨率的粒度特征研究,并与黄土高原典型黄土进行对比。研究结果显示哈尔滨组地层平均粒径、中值粒径以及粒级百分含量等大幅度波动,呈现黄土-古土壤地层旋回变化特征,黄土层粒度粗,古土壤层粒度细,与黄土高原典型第四纪黄土的粒度特征一致。荒山组地层则呈现小幅度波动,沉积动力较稳定。哈尔滨组和荒山组的粒度频率分布、C-M图及粒度参数（平均粒径、标准偏差、偏度、峰度）等特征均存在显著差别,指示二者的沉积动力过程明显不同。基于以上粒度特征,结合沉积相特征和已有划分方法,THS钻孔中-晚更新世地层自上而下可划分为哈尔滨组和荒山组,并将哈尔滨组地层判定为风成堆积,将荒山组地层判定为河湖相沉积。 相似文献
12.
The geochemical characteristics of an approximately 6‐m‐long sediment core collected from the Jeongokri archaeological site (Hantan River, Korea) were examined to determine the provenance of the sediments and to reconstruct the palaeoenvironment of the study area during the Late Pleistocene (200–127 ka). The core sediments were subdivided into two parts based on grain size: an upper (0–380 cm depth) and lower part (>380 cm depth). The lower part was deposited primarily by fluvial processes during an interglacial period [marine isotope stage (MIS) 7] with warm and humid conditions. Conversely, the upper part was mainly deposited by aeolian processes during a cold and dry glacial period (MIS 6). Geochemical characteristics, represented by major, trace and rare earth element (REE) compositions, and textures of the Jeongokri core sediments show distinct differences between the upper and lower parts. The mineralogy and major, trace and REE compositions indicate that the influence of felsic source rocks (e.g. granite) was dominant in the lower sediments, which were derived from the Hantan River. In contrast, increased quartz content and the very fine and homogeneous grain size in the upper sediments indicate an aeolian origin. REE ratios and distribution patterns, and geochemical signatures indicate that these sediments were derived predominantly from Chinese loess deposits and partially from local sediments from the Korean Peninsula; the possible source area of the upper sediments is the northern part of the Yellow Sea basin. The Yellow Sea basin, having mixed geochemical signatures between Chinese loess and Korean‐derived sediments, was exposed because of low sea levels during MIS 6. The exposed Yellow Sea basin was located in the path of winter‐monsoon winds, which may have carried a great deal of airborne sediments from the basin to the Jeongokri area. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
13.
Grain‐size data from different climatic zones across the Chinese Loess Plateau show that the loess generally contains an ultrafine component, which has a consistent modal grain size of ca 0·37 μm and a variable proportion of 4 to 10%. The variation of the ultrafine component through a loess section is characterized by a high proportion and fine grain size in palaeosols, and by a low proportion and coarse grain size in loess layers. Its proportional content in a stratum roughly increases from north‐west to south‐east across the Loess Plateau. Quantitative X‐ray diffraction analysis indicates that the ultrafine component is composed mainly of clay minerals (ca 70%), which are mostly illite (ca 80%), and with significant amounts of kaolinite (ca 8%) and chlorite (ca 2%). The temporal and spatial variations of the ultrafine component, and the degree of illite crystallinity, suggest that this component in aeolian sediments is linked closely to the process of pedogenesis. Weakly altered loess on the north‐western margin of the Loess Plateau contains considerable amounts of detrital clay minerals derived from the aeolian source areas. Results from a loess section with a basal age of 7·6 Ma in the central Loess Plateau show that the ultrafine component increased from 7·6 to 5 Ma, and progressively decreased thereafter. This trend was punctuated by two abrupt changes at 2·6 and 0·6 Ma. These variations reflect to a considerable extent the history of pedogenesis during the Late Cenozoic. 相似文献
14.
Comparison of laser grain size analysis with pipette and sieve analysis: a solution for the underestimation of the clay fraction 总被引：54，自引：1，他引：54
Classically, the grain size of soil and sediment samples is determined by the sieve method for the coarse fractions and by the pipette method, based on the ‘Stokes’ sedimentation rates, for the fine fractions. Results from the two methods are compared with results from laser diffraction size analysis, which is based on the forward scattering of monochromatic coherent light. From a point of view of laboratory efficiency, the laser sizing technique is far superior. Accuracy and reproducibility are shown by measurements on certified materials. It appears that laser grain size measurements of certified materials correspond very well with the certificated measurements. Tests were also done on a set of randomly selected sediments of fluvial, aeolian and lacustrine origin. Except for the (<2 μm) clay fraction, there is a coarsening of the mean diameter of one to two size classes (0.25 ?), caused by the non-sphericity of the particles. The platy form of the clay particles induces considerable differences (eight size classes) between pipette and laser measurements: the <2 μm grain size, defined by the pipette method corresponds with a grain size of 8 μm defined by the Laser Particle Sizer for the studied sediments. Using a higher grain size level for the clay fraction, when laser analysis is applied, enables workers in the geological and environmental field to compare classical pipette analysis with a laser sizing technique. 相似文献
15.
Junhuai Yang Dunsheng Xia Fuyuan Gao Shuyuan Wang Zixuan Chen Jia Jia Shengli Yang Zhiyong Ling 《地球科学进展》1986,35(8):863-877
The Yarlung Zangbo River is located in the southern Tibetan Plateau. Loess since the geological history and modern aeolian sand dunes are widely developed in the basin, bearing rich information on the aeolian processes and environmental evolution. In this work, we reviewed the main research progress of aeolian deposits in the Yarlung Zangbo River basin in recent years, and discussed the distribution characteristics, accumulation age, sediment characteristics and provenance and the possible formation mechanism of aeolian deposits and the history of aeolian activity. The results show that loess is mainly developed on the river’s terraces and some of the hilltops, and mostly formed since the last glacial maximum and mainly developed since Marine Isotope Stage 1 (about 14 ka BP), while aeolian sand deposit is mainly developed in the river’s wide valley, with relatively short accumulation time. The sediment particles mainly underwent mechanical transport and physical weathering, but chemical weathering was weak. Although the physical and chemical properties of sediments show some spatial changes, there still exist obvious local characteristics, which are closely related to the nearby surface sediments. Under the background of aeolian source, the local-source genesis of loess is generally recognized. The surface loose material at the bottom of valley is main material source of aeolian deposits. The evolution of aeolian activity is relatively complex. In addition to the regional climate change, the local environment is also an important factor affecting the aeolian activity and its regional difference. Based on the previous studies, we suggest that the systematic study on the physical and chemical properties of aeolian sediments, climate change since the Holocene and the impact of dust emission on human living environment should be strengthened in the future research. 相似文献
16.
17.
本文分析研究了昆仑山北坡克里雅河流域风成物质的粒度特征。该流域四大地貌景观带的地表沉积物表层样品的机械组成差别明显,黄土的粒度组成以粉砂为主,比我国黄河中游地区的黄土粗得多,亚砂土的主要成分为微砂,沙漠地区以细砂为主。除戈壁带以"非地"形式出现以外,由沙漠中心向南至昆仑山,在西北风和东北风的作用下,风成物质的粒度由粗变细。流域出露的黄土主要是在晚更新世和全新世沉积的。 相似文献
18.
第四纪网纹红土的类型与网纹化作用 总被引：1，自引：0，他引：1
第四纪网纹红土在中国南方红土发育区内广泛分布,具有特殊的结构,是第四纪红粘土的重要组成部分,按照质地网纹红土可分为均质类网纹红土和非均质类网纹红土。测试结果显示:（1）均质类网纹红土的粒度组成以粉砂（5～50 μm）和粘粒（<5 μm）为优势粒级,砂（>50 μm）含量很小,不足3%;粒度频率曲线多数呈单峰正偏形态,众数峰值位于5.5～6.5之间,部分呈双峰形态,两个峰值分别位于6和8附近;CIA值较高（84.31%～89.26%）,ba值较低（0.19～0.30）;稀土元素平均含量和分布模式与风尘沉积相似,87Sr/86Sr值与佳县上新世红粘土接近;εNd（0）介于-10.54～-12.66之间,表明物质源区基本稳定;均质类网纹红土的理化特征体现了风成沉积的特性和风化成土作用的显著影响,可称之为加积型网纹红土。（2）非均质类网纹红土发育自冲洪积相、坡积相沉积物或基岩风化壳红土,土体粉砂含量明显减少,多小于50%,砂含量大大增加,>50 μm和>250 μm粒级的离散系数较高,指示了显著的非均质特征;CIA值多数大于84%,化学元素和风化指标的离散系数多小于10%,显示其经历了较为强烈和稳定的风化作用。第四纪网纹红土的形成先后经历了风化成土过程和网纹化过程,南方红土区在网纹红土发育期内具有整体湿润的气候条件。 相似文献
19.
对于黄土高原粉尘物质的来源以及沙漠和河流对粉尘的贡献,仍未达成一致的认识。本研究以毛乌素东神木市石峁剖面为研究对象,利用碎屑锆石年龄谱,对末次冰消期以来的风成粉尘堆积和河流沉积物展开源区分析,并使用逆蒙特卡罗模型进行物源的定量计算。结果显示,粒径分布和阴极发光(CL)图像显示石峁黄土为典型风成沉积。其粗颗粒碎屑锆石(>40 μm)年龄峰值集中在190~300 Ma、300~600 Ma、1700~1900 Ma和2300~2600 Ma,年龄谱显示近源(局地基岩碎屑)、中源(黄河河沙)和远源(阿拉善地区沙漠)均有贡献; 定量计算表明,三者分别贡献71%、21%和8%的风成粗颗粒。中、近源中,黄河及其支流侵蚀基岩后搬运沉积的漫滩物质成为粉尘输移的中转站,为黄土的形成提供了主要的物源。光释光测年结果表明,石峁剖面河流沉积物及其上覆的黄土物质分别形成于倒数第2次冰消期和末次冰消期,两者之间的沉积间断可能指示了末次冰期至冰消期的侵蚀事件,导致了河滩物质暴露,从而形成了潜在的局地尘源。这些结果表明,包括黄河干支流在内的河流系统对黄土粉尘有重要的物源贡献。 相似文献
20.
The loamy ?brickearth’? deposits overlying coarse cold climate Kempton Park, Lynch Hill and Taplow Gravels of the R. Thames in west London are dated by thermoluminescence and mineralogical comparisons with loesses of three known ages. Although much of the ?brickearth’? resembles loess, it often contains more sand or clay than typical loess, and the mineralogical studies suggest that even the coarse silt (16–63 μm) fraction is rarely similar in composition to any known English loess. The thermoluminescence measurements suggest that most of the ?brickearth’? on the Taplow and Lynch Hill Gravels was deposited in the late Devensian, whereas that on the Park Gravel is mainly Flandrian. It is suggested that the latter is mainly floodloam, whereas the earlier ?brickearth’? is a mixed aeolian sediment derived from various local sources in and close to the Thames Valley. 相似文献