Pleistocene fluvial sediments,palaeontology and archaeology of the upper River Thames at Latton,Wiltshire, England     

S. G. Lewis  D. Maddy  C. Buckingham  G. R. Coope  M. H. Field  D. H. Keen  A. W. G. Pike  D. A. Roe  R. G. Scaife  K. Scott 《第四纪科学杂志》2006,21(2):181-205

Pleistocene fluvial sediments of the Northmoor Member of the Upper Thames Formation exposed at Latton, Wiltshire, record episodic deposition close to the Churn–Thames confluence possibly spanning the interval from Marine Isotope Stages (MIS) 7 to 2. The sequence is dominated by gravel facies, indicating deposition by a high‐energy, gravel‐bed river. A number of fine‐grained organic sediment bodies within the sequence have yielded palaeoenvironmental and biostratigraphical data from Mollusca, Coleoptera, vertebrates, pollen and plant macrofossils. The basal deposit (Facies Association A) contains faunal material indicating temperate conditions. Most of the palaeontological evidence including a distinctive small form of mammoth (Mammuthus cf. trogontherii), together with the U‐series age estimate of >147.4 ± 20 kyr suggest correlation with MIS 7. The overlying deposits (Facies Associations B and C) represent deposition under a range of climatic conditions. Two fine‐grained organic deposits occurred within Association B; one (Association Ba) in the northern part of the pit as a channel fill and the other (Association Bb) in its southern part as a scour‐fill deposit. The coleopteran assemblages from Ba, indicate that it accumulated under temperate oceanic conditions, while Bb, which also yielded a radiocarbon age estimate of 39 560 ± 780 ¹⁴C yr BP, was formed under much colder and more continental climatic conditions. The sequence is considered to represent deposition within an alluvial fan formed at the Churn–Thames confluence; a depositional scenario which may account for the juxtaposition of sediments and fossils of widely differing age within the same altitudinal range. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

A magnetotelluric survey on Manitoulin Island and Bruce Peninsula along GLIMPCE seismic line J: black shales mask the Grenville Front     

M. Mareschal  R. D. Kurtz  M. Chouteau  R. Chakridi 《Geophysical Journal International》1991,105(1):173-183

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黄河沉积物中稀土元素(REE)组成的粒度效应^*     

戴慧敏  鲍庆中  杨作升  王水利  宫传东  张泉  孙中任 《第四纪研究》2007,27(5):718-723

依据Stokes颗粒沉降原理将黄河利津水文站和汊河清八站的表层沉积物分别提取为<2μm,2~4μm,4~8μm,8~16μm,16~32μm和32~63μm的6个粒级,采用ICP-MS法对各个粒级沉积物的15个稀土元素进行测试。结果表明:黄河沉积物两个样品REE含量随粒度增大的变化趋势有细微差别,但总体随粒度大小呈"高—低—高"的不对称马鞍型分布,其中最高REE含量和最低REE含量分别位于<4μm的粘土粒级和4~16μm细粉砂粒级中; 各粒级沉积物经北美页岩标准化后,REE的配分模式一致,呈平缓的右倾型,相对富集轻稀土,明显的Eu正异常和Ce负异常。对各个粒级样品进行X射线衍射分析及体视镜下观测,石英含量随粒级增大而增加, 长石在8~16μm中含量最高,在16~32μm中,碳酸岩含量最高,随着粒级增大,重矿物含量逐渐增加,黄河沉积物REE随粒度的变化特征与粘土矿物对其吸附及流域碎屑沉积物不同粒级的矿物成分密切相关。  相似文献   

Application and evaluation of multiple-centres ESR dating of Pliocene-Quaternary fluvial sediments: A case study from the Zhoulao core from the Jianghan Basin,middle Yangtze River basin,China     

《Quaternary Geochronology》2022

Multiple-centres electron spin resonance (MC-ESR) dating of quartz grains has been commonly applied to fluvial and lacustrine deposits and can provide a precise chronological framework for depositional histories. However, the reliability of this method for quartz grains obtained from sediments of boreholes, which are usually deposited continuously and record information regarding basin evolution and climate change, has not yet been assessed. In this study, we have initially applied the MC-ESR dating method to borehole sediments from the Zhoulao core (ZLC), located in the depocenter of the Jianghan Basin, middle Yangtze River, China. Dating of quartz grains from the ZLC using MC-ESR yields estimated ages that are generally consistent with the established paleomagnetic chronological framework. For Middle Pleistocene samples (i.e., 0.7–0.3 Ma), the Ti–Li centre provides more accurate ages than those of Al centre, which are overestimated. For Early Pleistocene samples (i.e., 2.3–0.8 Ma), both the Al centre and Ti–Li centre give highly consistent estimate ages, indicating that this is a favorable dating range for MC-ESR. Overall, the Al centre shows promise for dating Pliocene samples, whereas the Ti–Li centre is more suitable for Middle-Early Pleistocene (2.3–0.3 Ma) sediments. In addition, the deposition rate of depth ＜170 m in the ZLC is greater than those of depth ＞170 m sediments; however, the specific tectonic, climatic, or geomorphic mechanism for this change in sedimentation rate is still unclear.  相似文献   

ESR chronology of the fluvial sequence of Cueva del Silo (Sierra de Atapuerca,Spain)     

《Quaternary Geochronology》2022

The Cueva del Silo is part of the lower karst level of the Cueva Mayor-Cueva del Silo karst system (Sierra de Atapuerca, Burgos, Spain), whose evolution has preserved an impressive archeo-paleoanthropological sequence since the Early Pleistocene. Cueva del Silo is remarkable for the presence of fluvial deposits that record the entry of the Arlanzón River water in the cave system, providing a key sequence to investigate the fluvio-karstic relationships that give rise to this endokarst system. In order to provide a chronological framework to these fluvial deposits, six sediment samples were dated by Electron Spin Resonance and 16 samples by paleomagnetism, collected from two outcrops: Galería de las Arenas and Sala del Caos. Our results provide maximum mean age of around 1600 ka and a minimum age of 916 ± 136 ka for the deposits in Sala del Caos. The younger date from Sala del Caos might represent the last fluvial input from Arlanzón River in the lower karst level. In contrast, ESR ages estimates of 1268 ± 133 ka and 1262 ± 108 ka were obtained for Galería de las Arenas sequence, which could indicate re-sedimentation processes from the intermediate karst level where similar ages were published. The annual dose might be wrongly assessed due to the re-sedimentation processes inside the karst, hence, ESR ages for these facies should be treated with extreme caution.  相似文献   

New chronological constraints on the Plio-Pleistocene uplift of the Guizhou Plateau,SE margin of the Tibetan Plateau     

《Quaternary Geochronology》2022

The Guizhou Plateau represents a geomorphic transition between the Tibetan Plateau and the Yangtze River Plain. It likely formed in response to the propagation of surface uplift in southeastern Tibet during India-Eurasia continental collision. However, the uplift history of the region is unclear largely due to a lack of datable material. The bedrock geology is dominated by carbonate rocks, which contains numerous multi-level caves in the main river valleys that are linked to the river incision history. Cosmogenic ²⁶Al and ¹⁰Be burial dating of sediments in caves and river terraces from the northwestern and southern plateau reveals the fluvial chronology and provides the first direct determination of long-term river incision rates. The caves and terraces on the Liuchong River in NW Guizhou yield burial ages of between 0.41 ± 0.12 Ma and 2.85 ± 0.21 Ma, indicating an average incision rate of 57 ± 3 m/Ma. Four level caves at Libo in southern Guizhou yield burial ages of between 0.56 ± 0.16 Ma and 3.54 (+0.25/-0.22) Ma, indicating slightly slower incision rate (47 ± 5 m/Ma). These new results imply that the high elevation of the Guizhou Plateau had developed before the Late Pliocene, and that surface uplift during the Late Cenozoic was largely uniform across the region.  相似文献   

Fluid-driven Hydrovolcanic Activity along Fracture Zones and near Seamounts: Evidence from Deep-sea Fe-rich Spherules,Central Indian Ocean Basin     

Ankeeta AMONKAR  Sridhar D. IYER  Elapavalooru V.S.S.K. BABU  Natarajan SHAILAJHA  Areef SARDAR  S. MANJU 《《地质学报》英文版》2021,95(5):1591-1603

An insight on occurrence of Fe-rich spherules from the Central Indian Ocean Basin (CIOB) provides an understanding of their distribution at a water depth of >5,000 m. In the present study, Fe-rich spherules are identified to occur in two different sediment types (i.e., siliceous and pelagic) and tectonic settings (i.e. near seamounts and fracture zones). These are single spheres or aggregates, of different sizes (63 to 390 μm) and show textural variability (smooth/quenched, brickwork, corkscrew, interlocking and dendritic). A comparative study based on physical morphology and chemical composition suggests a common mechanism of formation. The association of spherules with fracture zones (FZ) and seamounts signifies that morpho-tectonic features play an important role in fluid-driven hydrovolcanism. Based on the evidence and geologic conditions existing in the basin, we conclude that molten fuel-coolant interaction (MFCI) coupled with submarine hydrothermal exhalations could be an ideal mechanism for the formation of spherules and Fe-particles. The accretion of the spherules on the surface sediments could be a result of recent volcanic phenomena, while those occurring at different depths (280–355, and 460–475 cm-bsf) within the sediment core indicate two different episodes. The study provides a global implication in understanding fluid-driven magmatism in a deep-sea intraplate environment.  相似文献   

中国典型有机污染场地土层岩性和污染物特征分析   总被引：1，自引：0，他引：1  

朱辉  叶淑君  吴吉春  徐海珍 《地学前缘》2021,28(5):26-34

目前我国存在大量待修复场地,其分布具有一定的规律性和区域性,场地地层系统结构复杂、渗透性空间异质性显著,污染物种类复杂。总结场地典型土层结构和典型污染物有助于有针对性地开展修复技术的研发。为此,本文收集并整理了全国136处有机污染场地相关资料,对其地域性、地层及污染物特征总结如下:目前我国已经开展调查与修复的有机污染场地主要集中在京津冀和沪宁杭地区;有机污染场地土层基本都含有黏土等低渗透介质,而且都具有非均质性,其中67%场地土层有强非均质性;沪宁杭地区场地土层渗透性总体低于京津冀和辽中南地区,此外我国京津冀和辽中南地区场地调查深度(20.3 m)总体大于沪宁杭地区(12.8 m);我国有机污染场地地下水中最常见的有机污染物种类为氯代溶剂,依次为氯代烷烃类(场地数量占比84%)、氯代苯类(场地数量占比46%)和氯代烯烃类(场地数量占比33%);最常见的3种氯代溶剂依次为二氯乙烷、一氯苯和三氯甲烷。  相似文献   

湖泊沉积对地震动的响应特征与古地震序列重建     

李德文  李林林  马保起  张健 《地学前缘》2021,28(2):232-245

湖泊沉积因其对地震动的敏感而被认为是“天然地震仪”,湖泊沉积古地震研究有机会重建长时间尺度的地震(动)序列,对认识区域发震孕震环境和地震复发规律具有潜在优势,是当前古地震学研究的重要方向之一。本文旨在总结现今湖泊沉积古地震研究的主要进展、存在的问题和未来展望。首先通过与传统古地震研究关注的记录对比,扼要介绍了湖泊沉积地震动记录在形成和保存潜力、空间分布以及感应能力等方面的相对优势。然后从过程角度总结了湖泊沉积对地震动响应的主要机制,着重剖析了液化、流化和沉积物再悬浮等不同机制在控制因素、过程特点、响应阈值等方面的异同。再结合湖泊沉积对地震动响应的过程特点和研究现状,总结了不同类型的湖泊沉积地震动记录,对比分析了变形构造、块体运动堆积、浊流堆积和再悬浮沉积等4种类型记录的沉积学和动力学特征;对不同类型记录的古地震学含义和研究手段进行了梳理。再总结了地球物理勘探、结构构造和理化代理指标等现阶段流行的方法在不同尺度湖泊沉积古地震识别和古地震序列重建中的适用性和局限性,后者主要缘于湖泊沉积系统本身的复杂性和外部扰动过程的多样性。最后指出,当前湖泊沉积古地震研究面临的主要问题是缺乏普适性的响应模式、判别依据和甄别准则;今后工作应致力于对湖泊沉积地震动响应过程的深入理解,积极引进数字或试验模拟等理论工具与方法,从二维观察扩展到三维重建;数据解释力求宏观结合微观,由单一指标转向综合性组合式指标,为最终建立普适性的诊断指标和判别依据服务。  相似文献   

刘家峡水库表层沉积物微量元素地球化学特征   总被引：1，自引：1，他引：0       下载免费PDF全文

王建丰  雷天柱  张生银  张喜龙  陈文磊  樊海龙 《沉积与特提斯地质》2018,38(3):51-59

采用多元统计的方法对刘家峡水库表层沉积物中25种微量元素的含量、相关性、来源及控制因素进行了分析。结果显示:研究区表层沉积物中Sr、Zn、Zr和Ba的含量平均值超过了170μg/g,Cd、Mo和Tl的含量平均值都在1μg/g以下,其它元素含量平均值则在2. 01~104. 34μg/g。元素Cu、V、Co、Cr、Ni、Rb、Li、Cd、Be、Pb、Sc、As、Ga、Nb、Sn、Cs、Tl、Th和Al2O3等存在较为明显的相关性,且它们分布规律基本相似。因子分析表明,水库中微量元素分为3个主要来源,第一组分的元素分布受控于矿物岩石的自然风化剥蚀,其贡献率为63. 20%;第二组分的Zr和Ba主要受河流沉积物中元素的迁移和转化的影响,其贡献率为12. 51%;第三组分的Sr则主要受控于生物成因,其贡献率为9. 76%。另外,研究区重金属元素中,Zn和As含量远超过了全球页岩平均值,值得进一步的深入研究。  相似文献