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1.
文章利用高分辨率激光粒度仪MS2000对我国典型地区5种沉积类型滑坡的滑带(面)土和滑坡细粒堆积物的粒度多组分分布特征进行了系统、深入研究,总结了不同沉积类型滑坡滑带(面)土与滑坡堆积物的粒度多组分分布特征及差异性,其对于认识滑坡的成因机制具有重要的理论和实践意义。研究认为:(1)不同沉积类型的滑坡滑带(面)土和滑坡堆积物的粒度一般含有4个组分,其分别为风成的细、中、粗粒组分和水成的悬浮组分; (2)不同地区不同沉积类型的滑坡其滑带(面)土粒度与滑坡堆积物的粒度多组分具有不同的分布特征; (3)同一地区滑坡的滑带(面)土与滑坡堆积物的粒度多组分分布特征有较大差异,主要受控于滑坡本身的形成演化过程。 相似文献
2.
The elimination of grain size's effect is vital to analyze the chemical weathering history of eolian deposits. In this study, the relationship between chemical weathering and grain-size distribution of eolian deposits are analyzed and a new approach was developed to eliminate the effect of grain size in evaluation of chemical weathering. It was concluded (1) the effect of grain size to major elemental abundances (MEA) can be eliminated by deducting the grain size-led offset from measured major elemental abundances. (2) The effect of grain size to MEA intensified from south to north in Chinese loess plateau as chemical weathering weakened. The effect of grain size to MEA did not change the whole evolution trend of MEA in time series. (3) The similarity between median size and MMEA indicated the effect level of grain size to MEA. (4) The effect of chemical weathering to grain-size distribution is neglectable for loess–paleosol formation. (5) Usually, the effect of grain size to chemical weathering index is more remarkable in interglacial periods than in glacial period. 相似文献
3.
根据长江三角洲ZK01孔的粒度资料,从粒度参数、斜体图、概率累积曲线和频率分布曲线等对末次盛冰期以来的沉积物粒度特征进行了详细分析,并结合沉积物的岩性、沉积构造和有孔虫的分布特点,探讨了该区末次盛冰期以来的沉积环境演化。分析表明,ZK01孔末次盛冰期以来,沉积物自下而上可分为5段:河床沉积物以砂和砾质砂为主,粒度概率累积曲线为以跳跃总体为主的两段式;河漫滩相为砂质和黏土互层,概率累积曲线呈以悬浮总体为主的具过渡的两段式,频率分布曲线为双峰或多峰式;河口湾沉积物的粒度参数变化显著,在C-M图上表现为粗细分异明显的两类,对应两种两段式累积曲线,频率分布曲线亦有单峰和双峰式两类;浅海相主要为淤泥质黏土,粒度参数较稳定,概率累积曲线为一段式,几乎均为悬浮总体;三角洲沉积物以细砂和粉砂为主,概率累积曲线为以跳跃总体为主的具过渡的两段式。研究区该时期依次经历了河床、河漫滩、河口湾、浅海和三角洲等5种沉积环境。 相似文献
4.
通过留山盆地上三叠统概率累积曲线、粒度参数和C-M图解等分析,沉积物粒度特征主要反映了扇三角洲泥石流、水下分流河道和河口坝沉积。下部太山庙组显示了水流由强至弱,搬运能力逐渐减小的过程;上部太子山组显示出水流不稳,流速交替多变的特点。粒度特征也显示了紊流作用的强烈影响,而紊流作用的产生可能与快速水流以及较高的悬浮颗粒含量有关。 相似文献
5.
Variations in magnetostratigraphy, pedostratigraphy, grain size and magnetic susceptibility of the loess deposits near Beijing have been studied at two sections. The sections are about 400 km east of the main loess deposits in China, have a maximum thickness of 100 m and extend back to 1.1 Ma. The sequence consists of 14 loess–palaeosol couplets (S0‐S14), which correlate well with sequences in the Loess Plateau. Susceptibility records from the sites near Beijing are comparable to the Xifeng, Luochuan and Baoji sections located in the middle part of the Loess Plateau; however, the down‐core variations in the grain size in the Upper Lishi Formation exhibit some differences. The median grain size increases by about 25–30 µm from L4 to L2, with the sandy grains (>63 µm) increasing from 10–20 wt% to 40–50 wt% . This implies that the depositional environment of the dust sources in the Beijing loess section is different in some aspects from the Loess Plateau. The Beijing loess may have had a different dust source than the Loess Plateau. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
6.
The origin of the Tertiary ‘red clay’ underlying the Pleistocene loess in the Chinese Loess Plateau remains controversial, although several lines of evidence have suggested a wind‐blown origin. This study examines the particle‐size parameters of the late Miocene and Pliocene ‘red clay’ by comparing it with those of the late Pleistocene loess. The particle‐size distribution of a total of 15 339 loess and 6394 ‘red clay’ samples taken from 12 loess sections along a north–south transect and two ‘red clay’ sequences at Lingtai and Jingchuan was systematically analysed. The median grain size, skewness and kurtosis of the late Pleistocene loess all show a systematic southward change and are principally influenced by distance from source region. The spatial and temporal differentiation of dust deposits is expressed in a skewness–kurtosis–median grain size ternary diagram, from which the distance to the source region can be inferred. The particle‐size characteristics of the Tertiary ‘red clay’ sediments are very similar to those of the palaeosols within the late Pleistocene loess deposits, suggesting an aeolian origin for the ‘red clay’. Based on the comparison of ‘red clay’ and loess in the ternary diagrams, it is inferred that the source–sink distance was greater in the Neogene than in the last and penultimate interglacials, and that the dust source region in north‐western China underwent a progressive expansion during the period from at least 7·0 Ma to the present. 相似文献
7.
BRIAN J. WILLIS 《Sedimentology》1989,36(5):757-766
Quantitative determination of palaeochannel geometry and hydraulics from point bar deposits requires an understanding of the interaction between channel-bend migration, temporal and spatial variation of point bar geometry and facies, and outcrop orientation. This interaction is modelled with the aid of a computer program which predicts three-dimensional (3-D) geometry and grain size variation of point bars. Synthetic deposits are produced for the cases of down-valley bend migration and/or increase in channel-bend sinuosity. Two-dimensional (2-D) cross-sections in varying orientations across these simulated deposits display lateral-accretion bedset surface geometry, and variation in mean bedset grain size and local palaeocurrent orientation. Most cross-sections show point bar deposits thickening away from the meander-belt axis due to a lateral progression from thinner bend-exit deposits to thicker bend-apex deposits (caused by down-valley channel translation), and/or due to a progression from thinner low sinuosity deposits to thicker high sinuosity deposits caused by channel bend expansion. In association with this lateral thickening, bedset surfaces become steeper and more convex upwards while the variation in mean grain size up bedsets commonly increases. Down-valley point bar translation allows preservation only of deposits formed downstream of the band apex, and produces characteristic fining upwards sequences. Marked lateral and vertical variations in palaeocurrent directions due to varying channel orientation relative to a given cross-section are also predicted. These results indicate a need in palaeochannel reconstructions, for a more detailed examination of 3-D variations in bedset surface geometry, palaeocurrent orientation and grain size distribution within and between bedsets of laterally accreted sediment. 相似文献
8.
兰州风尘沉积的粒度分布模式及其古气候意义 总被引：21，自引：5，他引：16
通过对兰州不同气候背景下形成的风尘沉积 1 80个样品详细的粒度分析,建立了该地区风尘沉积的粒度分布基本模式。发现研究区风尘沉积具有以下特征:(1 )沉积物分选差,主要由粒径 >4Φ的颗粒组成,平均6.4Φ (2 )粒级构成为极细砂 2.6 %、粉砂 77.8%、粘土 1 9.6 %,属粉质重亚粘土或典型黄土 (3)频率曲线为单峰、极正偏类型,且具有粗头短促、中间宽大和细尾拉长的特点 (4)短期悬浮颗粒与长期悬浮颗粒大致呈对等配比。这些特征同时也为兰州现代尘暴沉积物所具备,因而可视为该地区风尘沉积的一个基本诊断模式搬运方式。颗粒粒径 <5.5 0Φ的含量指标 (GSP1)和 4.5 0～ 6.5 0Φ的含量指标 (GSP2 )可分别作为冰期-间冰期尺度和冰段-间冰段尺度东亚冬季风演化和沙尘暴强弱程度的基本判据。 相似文献
9.
A coupled hydrostatic and morph-dynamic model COMCOT-SED was used to investigate the morphological change in Lhok Nga bay during the 2004 Indian Ocean tsunami, and the coupled model predicted the thickness of tsunami deposits in agreement with the measured ones. The relationship between the characteristics of tsunami deposit and flow hydrodynamics was discussed in details. Phenomena such as landward thinning in deposit thickness, landward fining in grain size, and fining upwards in grain size are commonly used to identify tsunami deposits and were examined in this case study. We also discussed the effects of sediment supplies and the constraints that can be put on the earthquake parameters using the information derived from tsunami deposits. This study shows that the model presented in this paper is capable of simulating extreme tsunami events (tsunami wave height ~30?m) in a large domain and that forward models of tsunami sediment transport can be a promising tool to help tsunami geologists understand tsunami deposits. 相似文献
10.
Through an analysis of their coarse-grain composition (>63 μm), pumice-rich sandy layers from deep sea cores were identified as shelf-derived turbidites rather than deposits due to ash rain or drifting pumice. A comparison of median sizes of individual grain types and total samples yielded significant vertical and horizontal sorting trends, which allowed apparently unrelated samples from different cores to be grouped into proximal and distal parts of one turbidite type. A discrimination of samples belonging to unrelated turbidite layers was also possible. In addition, whatever the grain size, planktonic molluscs and foraminifera have Md-diameters 1·1–2·75 times larger than those of pumice. Weathered shallow-water skeletals have Md-diameters approximately equal to pumice, whereas those of augite and hornblende are 1·25–2·3 times smaller. This results in a different proportion of components in proximal and distal turbidite samples. The Md-values of planktonic foraminifera reach their upper natural limit at 250–350 μm. 相似文献
11.
冰期向间冰期转换或现代全球气候变暖等背景下,冰川一旦退缩就会引发基岩和冰碛边坡失稳,甚至冰川泥石流等冰消后（paraglacial）地表过程;因此,该过程成为驱动原冰川作用区及其下游谷地地貌演化的重要因子。然而,冰消后过程时空变化特征及其驱动因子等相关研究,目前仍面临两方面问题：其一,各种冰消后沉积、冰碛等混杂堆积间判别的手段缺乏;其二,冰消后过程对下游谷地演化影响的关注不足。为此,本文以典型海洋型冰川作用区——贡嘎山东坡的冰碛和冰消后沉积为研究对象,并结合两处大陆型冰川冰碛,探讨了粒度和石英颗粒表面形态特征两个指标区分上述混杂堆积的有效性。结果表明,各种冰消后沉积物继承了源区冰碛的很多特征,但也呈现出一定独特性,指示出这两个指标综合对比的方法能实现各类冰消后沉积、冰碛的有效判别;同时,鉴于冰川性质、冰川作用期次和岩性等因素都可能影响源区冰碛的粒度和石英颗粒表面形态,以这两个指标判别时应限于同区域,避免选用沉积物的共性特征。基于贡嘎山东坡冰碛、各种冰消后沉积物与磨西台地不同层位粒度与石英颗粒表面形态的对比和聚类分析,确认台地底部和中部可能分别为MIS3冰碛与MIS3以来的泥石流沉积,上部则可能为河流沉积或河流改造过的冰川泥石流沉积。磨西谷地冰消后过程堆积和暴露时代,指示出强烈冰消后过程使得磨西河谷地末次冰期向全新世转换时一直在堆积,甚至持续到约6~7 ka前后才停止,之后转为侵蚀下切。 相似文献
12.
对河北平原中部保定西伯章厚20.74 m的剖面进行实测,系统采集粒度和光释光（OSL）样品进行分析,以期获得其沉积特征及环境演变信息。光释光测年显示该剖面为102~8.69 ka的沉积,时代属于晚更新世到早全新世。岩性和粒度分析表明该剖面为曲流河冲积沉积,可以进一步划分为河道沉积和河漫滩沉积。河道沉积以含云母碎片的中粗砂为主,发育斜层理,频率曲线以正偏双峰频率曲线为主,分选中等到较差,概率累积曲线以跳跃组分为主的两段式为主。河漫滩沉积以黏土质粉砂为主,含保存良好的腹足类化石和钙质结核,频率曲线以负偏双峰为主,分选差,概率累积曲线以悬浮组分占比大的两段式为主。C-M图显示该剖面以均匀悬浮沉积为主,属典型曲流河沉积。实测剖面与黄土剖面对比分析显示西伯章剖面可以分为三个阶段,下部20.74~16.14 m为末次间冰期晚期沉积,气候温暖湿润,以粉砂质沉积为主;中部16.14~3.18 m为末次冰期沉积,气候干冷,沉积物显示细—粗—细的特征,与末次冰期早冰阶—间冰阶—盛冰阶一一对应;上部3.18~0.2 m为冰后期沉积,与末次间冰期晚期沉积环境类似,以黏土和黏土质粉砂沉积为主。粒度成因分析揭示了河北平原中部保定凹陷区晚第四纪沉积环境主要为河流冲积环境,粒度阶段性分布特征是晚第四纪以来冰期-间冰期气候的物质响应。 相似文献
13.
A Study of Occurrences of Ag in Pb-Zn-Cu Ore Deposits in China 总被引：2，自引：0，他引：2
WANG JingchunBeijing Institute of Geology for Mineral Resources State Bureau of Nonferrous Metals Industry Andingmenwai Beijing 《《地质学报》英文版》2000,74(3):516-520
A systematic study of occurrences of silver in 156 Pb-Zn-Cu ore deposits indicates that silver mainly occurs in nonferrous metal ore deposits in forms of association and paragenesis. It occurs mainly as independent minerals in nature and occasionally as ion adsorption, isomorphous or amorphous silver minerals. Nearly 190 silver minerals have been discovered in China. Their shapes, constituents, textures, grain sizes, embedded types, distribution patterns, mineral assemblages and metallogenic series suggest that these characteristics are closely related to geneses of deposits and dependent of ore-forming conditions. Pb, Zn and Cu sulphides are the main carrier minerals of silver. The partition of silver in ore is constrained by the mineralization intensity, grain size and embedded form of silver minerals and mineral assemblages. 相似文献
14.
罗布泊全新世沉积特征及其环境意义 总被引：1，自引：0，他引：1
罗布泊西湖属开阔湖盆,上世纪30年代其面积达1900km2,但湖心剖面粒度分析的结果表明,其粒度组成与一般开阔湖盆有着显著的不同:沉积物常具黄色与灰色互层结构,层理清晰,黄色层的粒度组成中常含较多粗颗粒砂,灰与黄色层的混合样是以粉砂黏土为主,同时含有一定量的中、细砂,甚至粗砂。根据与风成砂和尘暴沉积的粒度组成对比,可知这种沉积特征与现代尘暴沉积有很大的相似性,因而表明风尘是罗布泊沉积的重要物源,并可据此来恢复10000a以来本区尘暴作用的强弱变化。 相似文献
15.
Breakage models and particle analyses have been widely used as tools for describing and interpreting various deposits and
providing parameters for assessing the particle-size distribution of the deposits. Debris flows can be seen as a two-phase
rheological fluid with a clay-fluid composition, and debris-flow deposits comprise mud, silt, sand, and boulders, with grain
sizes ranging from less than one μm to more than several meters. As a consequence, according to fractal theory, the particles
in debris-flow deposits have self-similarity in geometrical shape and scale invariance in size. In this paper, the fractal
dimensions of particles in various debris-flow deposits are calculated and corresponding fractal features are determined based
on fractal-statistical theory. The aims of the study are: to provide a quantitative grain parameter that reflects both the
grain composition and grain-size distribution in debris-flow deposits; to compare the fractal dimensions of grains in different
types of debris-flow deposits and the degree of self-organization of debris flows; as well as to discuss the geological implications
of fractal dimensions and fractal features of particles in debris-flow deposits. 相似文献
16.
冰筏沉积(ice-rafted deposits)作为一种古气候、古地理再造的有效记录,在欧洲和北美已有许多研究,而在我国研究较少。本文为作者在查阅国外有关冰筏沉积文献基础上,对冰筏沉积做一综述,以期引起广大沉积学同行的注意。一、冰筏沉积的研究历史及现状对冰川作用的研究,始于1840年,地质学家们在试图解释覆盖于北欧、英格兰及北美等地的巨厚大陆冰川时开始了冰川作用的研究,提出了冰川作用的理论。冰筏作用是冰川作用中的一种特殊类型。早在1842年,英国地质学家Cnarles Darwin在研究Tierra del Fuego东部地区冰川时就认识到其中的冰筏沉积,并且总结了冰筏形成的两种作用,即入海的冰 相似文献
17.
介绍了美国卡林型金矿的地质特征及分布特点,从赋矿地层及含矿岩性、控矿构造、围岩蚀变、矿物组合、元素共生组合、金的赋存状态和粒度、金银比值及其他方面详细阐述了甘肃省舟曲—文县一带卡林型金矿地质特征,总结了卡林型金矿的找矿标志,通过与美国卡林型金矿的类比指出了该区具有金矿找矿的巨大潜力。 相似文献
18.
我国主要金红石矿床金红石自然颗粒产状及粒度特征 总被引：4，自引：3，他引：1
我国已知主要金红石矿床有江苏东海榴辉岩型、湖北大阜山榴闪岩型、豫陕交界处八庙—青山角闪片岩型、陕西凤凰尖千枚岩型及山西碾子沟直闪 (片 )岩型 5个 ,前 4者为变质成因 ,后者为变质蚀变成因。变质型矿床 ,金红石自然颗粒主要为单晶、粒度较细、分布均匀 ,随着变质温压降低、粒度有明显变小趋势 ;变质蚀变型矿床 ,金红石自然颗粒主要为集合体、粒度粗、局部富集。其成因前者为变质过程是没有水参与的“干变”及变质温压的改变 ;后者蚀变过程是有水参与的“湿变” ,并且其环境为金红石提供了充分的生长空间。 相似文献
19.
根据钻井岩心、铸体薄片、扫描电镜、测录井资料及分析化验资料,对柴达木盆地北缘西段平台地区古近系路乐河组地层岩心的沉积构造、粒度特征、沉积序列等进行详细研究,分析平台地区古近系路乐河组的沉积相类型及演化过程。研究表明,平台地区路乐河组主要受近源沉积控制,沉积了一套以砾岩、含砾粗砂岩、泥质粉砂岩和泥岩为主的粗粒碎屑岩,发育槽状交错层理和板状交错层理,成分成熟度和结构成熟度较差。粒度概率累积曲线显示碎屑颗粒沉积物主要由悬浮组分和跳跃组分组成,表明水动力条件较强,以河流相沉积为主。沉积微相类型以河床亚相的河床滞留和心滩沉积为主,其次为河漫亚相的河漫滩沉积和泛滥平原沉积。沉积相的研究清楚展示出平台地区古近纪早期路乐河组的沉积特征和演化规律,为该地区下一步油气勘探工作提供可靠的地质依据。 相似文献
20.
原生矿床中金的主要性状有自然金与金的碲化物，自然金可分为“明金”和“微细粒金”，“明金”的次生作用，使金的成色得到提高，粒度更大，往往有利于残坡积型砂金矿床的形成，“微细粒金”的次生作用，常形成卡林型氧化金矿或红土型金矿和铁帽型金矿，显然，以“明金”为主的矿床及金的重砂异常区，不存在找红土型金矿的可能，应寻找脉金矿床，而在有低值金的重砂异常叠加的化探Au异常区，有望找到中小型红土型金矿床。 相似文献