王兆夺
, 黄春长, 杨红瑾, 庞奖励, 查小春, 周亚利
陕西师范大学地理科学与旅游学院, 陕西 西安 710119; 陕西师范大学/地理学国家级实验教学示范中心, 陕西 西安 710119
Wang Zhaoduo, Huang Chunchang, Yang Hongjin, Pang Jiangli, Zha Xiaochun, Zhou Yali
中图分类号: F129.9
文献标识码: A
文章编号: 1000-0690（2018）05-0818-09
通讯作者:
收稿日期: 2017-06-2
修回日期: 2017-11-4
网络出版日期: 2018-05-10
版权声明: 2018 《地理科学》编辑部 本文是开放获取期刊文献，在以下情况下可以自由使用：学术研究、学术交流、科研教学等，但不允许用于商业目的.
基金资助:
作者简介:
作者简介：王兆夺（1984-）, 男,甘肃会宁人, 博士研究生, 研究方向为资源开发与环境演变。E-mail：joedonwang@163.com
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摘要
在宁夏长城塬完整的晚更新世-全新世黄土-古土壤剖面(长城塬剖面)进行高分辨率采样,对125个样品的粒度数据做了粒度端元分析,并对各端元组分含量在地层深度尺度上做了小波分析。结果认为：端元分析法可以把代
关键词：
Abstract
This article makes End Member analysis on grain-size data collected from high resolution 125 samples based on typical Late Pleistocene-Holocene Loess-Paleosol profile (CCY profile) in Changchengyuan, Ningxia Province, and do the wavelet analysis for the End Members components on the axis in depth. The research result shows that four End Members can be separated from the sediment grain sizes in CCY profile. And the EM1 may indicate dust from far source under the high-altitude airflow controlled by westerly belt. The EM2 may indicate dynamic strength of sedimentation under the influence of weathering and pedogenesis. The EM3 may represents the eluviation dynamic characteristic. The EM4 may indicates the northwest monsoons typical eolian loess under the influence of component characteristics. According to the wavelet analysis, it can be concluded that the component content of each dynamic of End Member has periodic variation at different depths, which indicates that the corresponding time scale of the paleomonsoon variation has periodic characteristics, and also indicates that the sedimentary profile has been in a continuous and uninterrupted sedimentary state, and the sedimentary dynamic processes are recorded completely. Each End Member component has different periodic characteristics on different depth (time) scales.
Keywords：
黄土高原在沉积的过程中比较完整地记载着全球气候变化信息,在黄土研究中,以杰出的第四纪地质学家刘东生先生为代表的科学家做了大量工作[1,2,3,4,5,6],其工作被学术界普遍肯定。黄土沉积序列对反演第四纪以来亚洲季风演变具有十分重要的指示意义,和冰川、深海沉积物一起被称为全球气候变化的三大信息载体。沉积物的粒度特征是沉积学研究中最常规的指标之一,它蕴含着沉积物的沉积作用,沉积动力以及沉积环境[7]。由于沉积物在沉积的过程中往往是多种沉积动力、物源、以及次生作用综合作用的结果,所以把代表不同沉积动力的粒级组分分离出来,更有利于研究各动力的变化过程。在粒度分析工作中,随着高分辨率激光粒度仪的出现,可以精细地统计微米级体积百分含量,Weltje提出了端元分析方法[8],对沉积物混合组分能够有效地分离鉴别,前人在海洋以及湖泊沉积物中端元分析方法得到了应用[9,10,11,12,13],但在黄土-古土壤的研究上应用得较少。长城塬剖面是黄河中游地段一条较为典型的全新世黄土-古土壤剖面,之前就沉积物地球化学元素和土壤微结构特征做了工作[14,15],对其沉积物粒度的研究尚未开展。由于黄土粒度全样亦是多动力组合的结果,所以粒度全样在判断古气候上具有复杂性和不确定性[16],鉴于此,针对宁夏长城塬黄土-古土壤沉积剖面对其粒度数据应用端元分析方法和小波分析进行研究,旨在进一步通过沉积物在形成过程中受到的各沉积动力因素来探讨黄土高原中部地区沉积动力和物源演化特征。
长城塬（CCY）剖面（106°46′43.9″E,35°52′0.8″N）位于黄土高原北部的宁夏回族自治区固原市的长城塬塬面上,海拔在1 650~1 700 m之间,长城塬剖面位于六盘山东麓（图1a）,属于温带半干旱大陆性季风气候,年平均气温为7.4℃~8.4℃,年降水量350~550 mm,研究剖面风尘堆积和成壤时期地面比较稳定,黄土连续堆积,形成较深厚的地层,保存了比较完整的古季风气候变化信息。根据中国风资料分析[17],研究区明显地表现出冬季主要受到西北季风、西风带西风的影响,而夏季主要受到东南及南季风的作用（图1b）。对长城塬剖面0~250 cm深,按2 cm间距连续采样,获得样品125个。通过对本剖面野外观测、室内测试和地层对比,认为属于完整的晚更新-全新世黄土-古土壤剖面[14,15]（图2）。
图1 长城塬黄土古土壤剖面位置（a）和周边1961~1970年最高频率风向特征（b）注：b图中数字为风向概率。
Fig.1 The site of the Changchengyuan (CCY) profile (a) and the most frequency wind(b) in study area from 1961 to 1970
图2 长城塬剖面及地层描述
Fig.2 The picture of CCY profile and the sedimentary descriptions
对采集回来的样品使用激光粒度仪分析,获得数据系列之后,应用沉积物粒度端元分析模型软件进行分析。端元分析方法早期由Weltje提出,认为沉积物由不同的物质来源或者由不同的搬运动力经过组分混合而成,根据一组沉积物粒级数据进行了分析计算,然后把不同动力作用下的各端元组分分离出来[8],Paterson在此基础上运用Matlab软件进行了改进,本文采用的是Paterson改进的端元分析模型[18]。运行Matlab端元计算程序(AnalySize Software),导入粒级数据在假设端元数为1~10基础上,对粒度数据进行Nonparametric EMA计算,在端元数增大的情况下,粒级复相关系数R2逐渐接近于1（R2达到0.8以上说明端元数基本满足拟合的要求）和角度偏差变小的平衡拟合（角度偏差逐渐变小,说明随着端元数的增大,数据拟合得越好,大于4就不需要再分更多端元）,由此可见可以拟合4个端元组分（EM1、EM2、EM3和EM4）,通过对拟合出4端元数的沉积特征进行分析（图3）,认为划分出4个端元可以满足分析要求,所以本文选择4个端元对该组粒度数据进行分析。
图3 长城塬剖面端元数线性相关和角度离差
Fig.3 Linear correlation and angular deviation of end members in CCY profile
小波分析,也被称为小波变换,是傅里叶变换进一步发展,近年来应用越来越广泛的方法。基于傅里叶变化在短时间尺度频谱分析上的局限性,法国地球物理工程师Morlet提出了小波分析,小波是一个衰减的波形信号,在变换的区间内波动存在且其均值为零,它是一种时间上和频率上可同时改变的时频局部化分析方法,在低频部分具有较高的频率分辨率和较低的时间分辨率,在高频部分具有较高的时间分辨率和较低的频率分辨率,很适合函数信号中携带的瞬态异常现象,被誉为信号分析的“数学显微镜”[19]。小波变换公式如下：
式中
变换过程中采用低通和高通滤波器,求取低频系数a1和高频系数d1,然后再分解a1为a2和d2,再分解a2为a3和d3,如此类推,然后再对低频系数和高频系数进行重构高频信号d3,d2,d1和低频信号a3,分别得到不同频率的周期旋回[19]。笔者采用Matlab软件中自带小波分析工具,对数据信号进行小波分析,旨在分离出信号数据变化分别在不同深度（时间）尺度上的旋回变化特征。
根据沉积物各粒径范围对应的体积百分含量,各沉积单元所有样品的算术平均值,绘制沉积物粒度频率分布曲线。可以看出曲线形态差异很小,基本是重合的（图4a）,结合谢帕德三角分类,判断出长城塬剖面沉积物属于黏土质粉砂,接近粉砂特征（图4b）。研究剖面属于典型的黄土-古土壤剖面,在黄土-古土壤沉积以及沉积后成壤改造的过程中,往往是多种因素综合作用的结果,这样在综合动力作用的情况下所形成的混合沉积物,给根据沉积物粒度反演沉积动力过程造成了一定的困难。基于端元分析方法能够根据沉积物样品总体频率特征有效地提取不同端元组分,对研究各动力特征具有明显的优势。由此,本文采用端元分析方法,对六盘山东麓晚更新世-全新世黄土沉积物粒度做端元划分,并对各端元组分含量在以相应深度尺度上的变化频率关系做进一步的小波分析。
图4 长城塬剖面黄土古土壤沉积物粒度频率曲线（a）谢帕德三角分类（b）
Fig.4 The grain size frequency curves of loess-palaosol sediment in the CCY profile(a) and Triangle diagram of Shephard(b)
通过对长城塬剖面沉积物粒度端元分析,对所分离出的4个端元做粒级频率曲线,从粒级频率曲线图可以看出（图5）,各端元曲线均呈现单峰细尾,分别具有不同的形态特征。据此,结合其它因素来判断在最大可能性的情况下,各曲线所代表的沉积学动力背景特征。
图5 长城塬剖面各端元粒度频率分布曲线
Fig.5 Grain size frequency distribution curves of each end member in the CCY profile
从各端元曲线特征来看,端元组分的平均粒径,从端元1到端元4,其依次增大;端元组分的分选系数都较大,分选性均较差,端元2分选性最差,端元1次之;它们的偏度系数和峰度值,端元4最大,端元1次之,4个端元的最主要组分均为粉砂质组分（图5,表1）。进一步就研究剖面中各端元组分含量、磁化率以及地球化学指标在深度上的对比分析（图6,表2）。从端元组分含量上可以看出,端元2与端元4在深度上呈现出相反变化趋势,端元2和端元3在TS与L0地层中均含量较低,在下部地层中表现出相反的变化特征,端元1和端元4组分含量总体上在各地层中变化特征较为接近,而在L1地层中差异较大。从磁化率和地球化学指标上看,端元2与磁化率和Rb/Sr值在深度变化上有明显地相对应关系,而端元3与淋溶系数[（CaO+K 2O+Na2O）/Al2O3]呈现出基本一致的对应关系,与残积系数[（Al2O3 +Fe2O3）/（CaO+MgO+Na2O）]呈现出相反的对应关系。各端元含量从各地层单位的组合上来看,端元1在近地表的TS和L0地层中较多,在下部地层S0、Lt和L1中明显贫化,端元2组分在S0中明显较其它层位富集,端元3组分含量在上部地层TS、L0和S0中均很低,而在下部地层Lt和L1中明显依次增多,端元4和端元2呈现出基本相反的变化特征（图6）。
图6 宁夏长城塬黄土古土壤剖面沉积物粒度、磁化率、地球化学指数垂向上变化特征
Fig.6 Changes in particle-size distribution, magnetic susceptibility and geochemical index in the Holocene loess palaeosol at the CCY site of Ningxia
表1 长城塬剖面各端元曲线参数特征
Table 1 The end member parameteres characteristic of CCY profile
| 平均粒径（Mz） | 分选系数（σ） | 偏度（Sk） | 峰度（Kg） | |
|---|---|---|---|---|
| EM1 | 8.92 | 4.42 | -0.37 | 1.06 |
| EM2 | 10.48 | 4.60 | -0.29 | 0.92 |
| EM3 | 14.68 | 3.49 | -0.26 | 0.97 |
| EM4 | 19.27 | 3.83 | -0.49 | 1.36 |
表2 长城塬（CCY）剖面沉积物中各端元组分含量、磁化率以及地球化学指标
Table 2 The end membercontents, magnetic susceptibility and geochemical index in sediment of CCY profile
| 深度 (cm) | EM1 (%) | EM2 (%) | EM3 (%) | EM4 (%) | 磁化率 （Xlf） | 地化指标 | 备注 | ||
|---|---|---|---|---|---|---|---|---|---|
| Rb/Sr | 淋溶系数 | 残积系数 | |||||||
| 0~20 | 39.28 | 7.70 | 6.88 | 46.13 | 69.6 | 0.48 | 1.04 | 1.32 | TS均值 |
| 20~54 | 29.68 | 14.72 | 5.44 | 50.16 | 71.6 | 0.47 | 1.07 | 1.29 | L0均值 |
| 54~150 | 17.80 | 47.73 | 9.63 | 24.85 | 79.0 | 0.51 | 1.04 | 1.34 | S0均值 |
| 150~190 | 17.14 | 25.18 | 39.89 | 17.80 | 57.1 | 0.44 | 1.21 | 1.13 | Lt均值 |
| 190~250 | 7.70 | 15.49 | 49.39 | 27.42 | 46.7 | 0.39 | 1.17 | 1.16 | L1均值 |
综合上述分析,可以认为端元2比较明显地指示了对已有的风成沉积物进行风化以及成壤改造作用,使得矿物颗粒总体变小,分选变差;端元3则可能代表了晚更新世以来平均降雨量作用下的淋溶作用,端元组分含量和淋溶作用为反相关;端元4和端元1曲线在深度变化形态上具有相似性,结合前人研究认识[20, 21],我们认为二者均代表了黄土沙尘暴沉积的原始动力组分,其中端元1表现为峰度较低,风选较差的细粒度组分,并考虑到属于物源较远,搬运动力减弱的情况下沉积,所以它可能代表了西风带控制的由高空气流搬运的远源粉尘;而端元4符合峰度较高,分选较好的粗粒组分特征,则可能代表了东亚冬季风动力条件下,通过沙尘暴的形式从西北荒漠中搬运而来的粗颗粒组分（图6）。
本剖面地层中150 cm以下为晚更新世马兰黄土层L1和全新世过渡型黄土层Lt,总体上其各端元均有分布,但以端元3和端元4为主要组分,端元3可达50%以上,端元4次之,而端元1和端元2组分较少,此现象说明相比较上部地层,L1黄土层中风化成壤改造作用及淋溶作用均很弱;在150~54 cm的深度上端元2为最主要组分,可达50%以上,端元1和端元4次之,端元3很少,说明在8 500~3 100 a BP的全新世大暖期,东亚夏季风加强,古土壤化作用强烈,降雨量较多,淋溶作用亦很强;L0和TS地层中,从端元组合来判断,东亚冬季风作用加强,夏季风减弱,风化成壤及淋溶作用均明显减弱。整个剖面上各端元的综合特征来看,各端元组分呈锯齿状耦合变化能够灵敏地指示出晚更新世以来气候变化背景驱动下各动力一直处于不停地变化过程中,各动力组分决定了沉积物的组合特征（图6）。
基于端元分析,进一步对各端元组分含量以深度为变量做小波分析,通过Matlab小波分析工具箱中离散小波分析（Wavelet1-D/dmey/Level3）进行小波变换。结果显示,可以把各端元信号强度分离为低频信号和高频信号（s=a3+d3+d2+d1,s为各端元百分含量信号强度,a为低频信号,d为高频信号）,各端元组分含量在剖面深度上呈现出旋回准周期特征,且不同的频率尺度上具有不同的旋回准周期。端元1从a3低频长期尺度上呈现1.5个准周期旋回,未来可能会转为减弱,短期尺度上呈现6.5个准周期旋回,未来可能继续减弱;在d高频上可以分为d3、d2和d1这3个尺度,d3尺度上呈现出11个准周期旋回,d2尺度上呈现出24个准周期旋回,d1尺度上呈现出46个准周期旋回。端元2在a3低频长期尺度上呈现1个准周期,未来可能会转为增强,短期尺度上呈现5个准周期旋回,未来可能会持续减弱;在d高频上,d3尺度上呈现出13个准周期旋回,d2尺度上呈现出25个准周期旋回,d1呈现出44个准周期旋回。端元3在a3低频长期尺度上呈现1个准周期旋回,未来可能会转为增强,短期尺度上呈现6个准周期旋回,未来可能也会转为增强;在d高频尺度上,d3尺度上呈现出13个准周期旋回,d2尺度上呈现出26个准周期旋回,d1尺度上呈现出44个准周期旋回。端元4在a3低频长期尺度上呈现1.5个准周期旋回,未来可能会持续减弱,在短期尺度上呈现出5.5个准周期旋回,未来可能会转为增强;在d高频上,d3尺度上呈现出13个准周期旋回,d2尺度上呈现出25个准周期旋回,d1尺度上呈现出47个准周期旋回（图7）。
图7 宁夏长城塬黄土古土壤剖面各端元不同尺度强弱旋回特征
Fig.7 The characteristic about cycle in different scales for end members loess palaeosol at the CCY site of Ningxia
由于黄土在沉积的过程中受到了多种动力作用的影响,所以全样粒度在判断古气候上存在着复杂性[16],人们往往采用“中值粒径”[22],“粗细颗粒比值”[23],“粗颗粒含量” [24]等,另外,张小曳等[25]提出以大于20 μm的粒度组成作为冬季风强度替代性指标要优于全样的中值粒径,可以用小于1 μm的粒级的含量作为东亚夏季风替代性指标。但是上述划分均存在人为经验性,在不同区域上由于样品本身的属性其差异性难免,为了避免人为划分引起的不确定性,从样品本身属性的统计学意义上考虑,本文尝试采用端元分析方法来对各不同动力进行分离识别。
综上分析,应用端元分析,能够细致地鉴别出各沉积动力组分,从而很好地判别晚更新世以来黄土-古土壤剖面沉积组分变化特征。由于各端元组分在深度上的变化特征反演出各动力强弱的变化过程,这些动力是在相应区域内气候背景作用下所驱动,所以指示着气候变化信息。通过对各端元组分做进一步的小波分析,结果可以认为自晚更新世以来,各端元动力呈现出不同尺度上的周期性变化特点。我们在低频尺度上按照长期和短期两个尺度进行周期划分,通过周期性判断,可以明显地识别出各沉积端元动力目前所处的状态和未来可能的变化趋势,由于考虑到采样分辨率,样品的选取和测量过程中存在的随机误差和系统误差,所以高频域内旋回变化存在着偶然因素,可能并不能客观地反映出真实的变化特征,需要就同一个剖面采取多组不同分辨率的样品进行对比判断,有待进一步做工作对比验证。
1） 长城塬剖面沉积粒度组分分为4个端元：认为端元1可能代表了西风带控制下的高空气流搬运的远源粉尘沉积物;端元2比较明显地代表了沉积物在沉积之后受到的风化成壤的古土壤化作用影响;端元3则似乎代表了沉积物沉积之后,随着降雨量变化特征下的淋溶作用;端元4则可能代表了东亚冬季风作用下的动力组分特征,其物源为从西北沙漠源搬运来的沙尘暴沉积物,属于典型原始的风成黄土粗颗粒组分。
2） 通过对各端元曲线进行小波分析,认为不同的深度尺度上具有周期或准周期性特点。在晚更新世以来,研究地点没有明显的沉积间断（从采用分辨率角度看）,地层序列表现出比较完整序列的情况下,其沉积作用在各沉积动力以及改造动力的影响下进行,由此我们认为代表不同沉积动力和改造动力的各端元组分的变化能够有效地反映出古季风气候信息。
3） 各端元组分含量在深度尺度的周期旋回划分上,高频信号的变化,可能受到采样分辨率和样品随机性误差等多因素影响,所以高频信号分析结果仅仅作为参考,对于各端元信号强弱的变化,主要应考虑低频尺度上的强弱变化。通过本文研究,认为低频信号更为可靠恰当,能够很好地表现出周期性变化,并且可以判断未来可能的趋势。
The authors have declared that no competing interests exist.
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250万年以来的37个气候旋回 [J].
<正> 第四纪气候演化的重要特征为冰期与间冰期的交替旋迴。自70年代早期以来,四次冰期的经典模式逐渐被多重冰期的概念所替代。然而,第四纪气候到底经历了多少次冷暖旋迴,至今仍然是一个亟待解决的重要问题。
37 climate cycle since 2.5 million years .
<正> 第四纪气候演化的重要特征为冰期与间冰期的交替旋迴。自70年代早期以来,四次冰期的经典模式逐渐被多重冰期的概念所替代。然而,第四纪气候到底经历了多少次冷暖旋迴,至今仍然是一个亟待解决的重要问题。
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最近2.5Ma以来黄土高原风尘化学组成的变化与亚洲内陆的化学风化 [J].https://doi.org/10.3321/j.issn:1006-9267.2001.02.007 URL [本文引用: 1] 摘要
系统地分析了陕西洛川黄土-古土壤剖面中酸不溶相的主要元素, 微量元素和Sr同位素组成, 发现一些具有特征的地球化学参数(如化学风化指数CIA, Na/K, Rb/Sr和87Sr/86Sr)在剖面中呈规律性的分布和演化. 研究表明来源于亚洲内陆广大区域的黄土粉尘与上部陆壳相比明显地具有经受过Na, Ca化学风化的组成特点; 2.5 Ma以来黄土源区的化学风化呈逐步减弱的趋势, 并与同一时期全球冰量逐步增长的趋势相吻合; 因此第四纪以来亚洲内陆地区的干旱化现象可能是全球气候变化的区域响应.
The change of loess plateau dusty chemical composition and the chemical weathering over the Asian inland in recently 2.5 Ma years .https://doi.org/10.3321/j.issn:1006-9267.2001.02.007 URL [本文引用: 1] 摘要
系统地分析了陕西洛川黄土-古土壤剖面中酸不溶相的主要元素, 微量元素和Sr同位素组成, 发现一些具有特征的地球化学参数(如化学风化指数CIA, Na/K, Rb/Sr和87Sr/86Sr)在剖面中呈规律性的分布和演化. 研究表明来源于亚洲内陆广大区域的黄土粉尘与上部陆壳相比明显地具有经受过Na, Ca化学风化的组成特点; 2.5 Ma以来黄土源区的化学风化呈逐步减弱的趋势, 并与同一时期全球冰量逐步增长的趋势相吻合; 因此第四纪以来亚洲内陆地区的干旱化现象可能是全球气候变化的区域响应.
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The long-term paleomonsoon variation recorded by the loess-paleosol sequence in central China [J].https://doi.org/10.1016/1040-6182(90)90042-3 URL [本文引用: 1] 摘要
The loess-paleosol sequence in Central China during the last 2.5 Ma is a good record of the Asian monsoon variation, which could be considered as the concrete realization of global paleoclimatic cycles. The geological and biological evidence of the loess-paleosol sequence indicates that the loess was mainly the dust deposits transported by the northerly wind of winter monsoons and also suffered to some extent from pedogenesis caused by weakened summer monsoons, and that the paleosol accreted by the rather slow dust accumulation was closely related to strengthened summer monsoons. An alternating occurrence of loess and paleosol in the Luochuan section implies the variation history of warm-humid climate with a summer monsoon dominance and cold-dry climate with a winter monsoon dominance. The magnetic susceptibility of loess and paleosol can be regarded as a proxy index of Asian monsoon variation. An analysis of the susceptibility curve and structure characters of Luochuan section shows that the Asian monsoon circulation was strengthened from Early Pleistocene to Late Pleistocene, and the 500 ka BP point and 1200 ka BP point seem to be a threshold and a turning point respectively in terms of the long-term paleomonsoon variation in Asia.
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Magnetic susceptibility evidence of monsoon variation on the Loess Plateau of central China during the last 130,000 years [J].https://doi.org/10.1016/0033-5894(91)90015-W URL [本文引用: 1] 摘要
The magnetic susceptibility of loess and paleosols in central China represents a proxy climate index closely related to past changes of precipitation and vegetation, and thus to summer monsoon intensity. Time series of magnetic susceptibility constructed for three loess-paleosol sequences in the southern part of the Chinese Loess Plateau document the history of summer monsoon variation during the last 130,000 yr. They correlate closely with the oxygen isotope record of stages 1 to 5 in deep-sea sediments. Soils were forming during intervals of strong summer monsoon, whereas loess units were deposited at times of reduced monsoon intensity. The Chinese loess-paleosol sequence can thus be viewed as a proxy record of Asian monsoon variability extending over the last 2.5 myr.
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基于表层沉积物粒度特征的鸭绿江口沉积环境分析 [J].https://doi.org/10.11759/hykx20121118002 URL [本文引用: 1] 摘要
To explore the resources and sedimentary environment of sediment in different areas of the Yalu River Estuary, 43 surface sediment samples obtained from different zone of the Yalu River Estuary were tested and analyzed. Through the computation of average grain size, sorting coefficient and other grain size parameters, distribution of grain size parameters of surface sediment was obtained and analyzed. The result showed that the sorts of surface sediment in the Yalu River Estuary are mainly sand, silty sand, sandy silt and a small amount of clayey silt, the distribution of sand is more widely than others. The resource of surface sediment has the properties of diversity and space difference. The sand transported by river is the primary source, together with the surface sediment’s movement to land of the shallow sea. The sediment in the downstream of the Yalu River comes from the river transport, the sediment in the middle branch channel, western branch channel and Liaodong shoal of the Yalu River comes from the river’s transport and the movement to land of the surface sediment in shallow sea. The sedimentary environment in different areas is diverse and it is influenced by the Yalu River’s runoff and the tides and waves of seas. The result of this study can provide evidence for the investigation to the Yalu River Estuary’s system evolutions.
Analyses of sedimentary environment according to the characteristics of grain size in surface sediment in the Yalu River Estuary .https://doi.org/10.11759/hykx20121118002 URL [本文引用: 1] 摘要
To explore the resources and sedimentary environment of sediment in different areas of the Yalu River Estuary, 43 surface sediment samples obtained from different zone of the Yalu River Estuary were tested and analyzed. Through the computation of average grain size, sorting coefficient and other grain size parameters, distribution of grain size parameters of surface sediment was obtained and analyzed. The result showed that the sorts of surface sediment in the Yalu River Estuary are mainly sand, silty sand, sandy silt and a small amount of clayey silt, the distribution of sand is more widely than others. The resource of surface sediment has the properties of diversity and space difference. The sand transported by river is the primary source, together with the surface sediment’s movement to land of the shallow sea. The sediment in the downstream of the Yalu River comes from the river transport, the sediment in the middle branch channel, western branch channel and Liaodong shoal of the Yalu River comes from the river’s transport and the movement to land of the surface sediment in shallow sea. The sedimentary environment in different areas is diverse and it is influenced by the Yalu River’s runoff and the tides and waves of seas. The result of this study can provide evidence for the investigation to the Yalu River Estuary’s system evolutions.
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End-member modeling of compositional data: Numerical-statistical algorithms for solving the explicit mixing problem [J]. |
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Coarse-grained and fine-grained turbidite systems as end member models: applicability and dangers [J].https://doi.org/10.1016/S0264-8172(99)00020-3 URL [本文引用: 1] 摘要
Submarine fan/turbidite systems can have any net-to-gross percentage. Prior to developing a model that best represents the deposits under investigation, the earth scientist should have an adequate understanding of the major external parameters that influence the transport and deposition of sediment. Tectonics influence the sediment source area and its overall distance to the shoreline, shelf width and basin morphology. The sand/clay ratio and size range dictate how far sediment can be transported. Climate influences erosion, transport and diagenesis. Relative sea-level fluctuations impact the transport from coast to basin. Using those parameters and two end-members—coarse-grained and fine-grained—an applicable model can be developed that best characterizes the fan under consideration.
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An end-member algorithm for deciphering modern detrital processes from lake sediments of Lake Donggi Cona, NE Tibetan Plateau, China [J].https://doi.org/10.1016/j.sedgeo.2011.09.014 URL [本文引用: 1] 摘要
Deciphering significant sedimentological processes from a set of sediment samples is an important step in reconstructing environmental changes. One approach going beyond classical methods is the unmixing of grain-size distributions. This paper presents a flexible end-member modelling algorithm that is based on eigenspace analysis and considers inherent uncertainties. It has been applied to the detrital grain-size components of lacustrine surface sediment samples of Lake Donggi Cona, Qinghai Province, China. It allows up to five grain-size end-members to be characterised and quantified in an optimal model. An end-member with a major mode in the clay domain accounts for 34% of variance within the grain-size data set. It may represent sedimentation of suspension load from linear and laminar runoff during heavy precipitation events in summer. Three end-members in the fine sand to medium silt domains make up 60% of lacustrine sedimentation. They may represent local to remote aeolian processes that peak in wintertime. A multimodal end-member explaining the remaining 6% of variance may represent further fluvial and littoral dynamics or random fluctuations and measurement errors. Several model runs of different scaling and numbers of end-members provided a suitable way to determine uncertainties inherent to the model. A comparison of 12 different model runs and their respective uncertainties yielded a distinct model of robust end-members. The clay and medium silt end-members are robust features of detrital sedimentation within Lake Donggi Cona. They alone explain 54.4% of total variance in the data. However, no spatial pattern or relation to water depth is found for any of the grain-size end-members. Thus, when past detrital sedimentation at Lake Donggi Cona is reconstructed, a special focus should be on the robust features attributed to aeolian and suspension-related sedimentation processes as well as on effective sediment mixing processes impeding a distinct correlation between grain size and spatial attributes. Further applications of the end-member modelling algorithm to other depositional environments are encouraged to demonstrate its universal applicability.
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Characterisation of transport processes and sedimentary deposits by statistical end-member mixing analysis of terrestrial sediments in the Donggi Cona lake catchment, NE Tibetan Plateau [J].https://doi.org/10.1016/j.sedgeo.2012.09.006 URL [本文引用: 1] 摘要
78 End-member mixing analysis of grain-size data from 912 Tibet Plateau samples. 78 Unmixing of grain-size distributions allows parameterization of large datasets. 78 EMMA resulted in 3 aeolian end-members: fine sand, medium sand and loess sediments. 78 Sediment characteristics relate to source material and indicate transport pathways. 78 EMMA reveals the distribution of dominant transport process regions.
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Lower Rhine historical flood magnitudes of the last 450 years reproduced from grain-size measurements of flood deposits using End Member Modelling [J].https://doi.org/10.1016/j.catena.2014.12.004 URL [本文引用: 1] 摘要
61Channel-fills and scour hole fills act as archives for palaeoflood chronologies.61The coarsest part of flood beds holds information on flood magnitudes.61The coarse tail of grain-size distributions correlates best with flood magnitudes.61Discharge-deposition relations allow for palaeoflood magnitude reconstructions.
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南黄海表层沉积物粒度端元反演及其对沉积动力环境的指示意义 [J].End member inversion of surface sediment grain size in the South Yellow Sea and its implications for dynamic sedimentary environments. Science China: |
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宁夏长城塬全新世黄土-土壤元素地球化学特征研究 [J].
Through the analysis of macro- and micro-elements and their variations with XRF at the CCY loess-soil site, Ningxia Hui Autonomous Region, we obtain a number of geochemical parameters. There is a good comparison between these chemical parameters and magnetic susceptibility, frequency dependent susceptibility, which indicates that during the paleosol formation, the climate was warm and humid with abundant precipitation and greater eluviation, while during the loess accumulation, the climate was relatively cold and arid with weak pedogenesis. And the variation of elements can indirectly reflect the change of climate and pedogenic environment during the process of loess chemical weathering. Through the research of the activities of elements in CCY profile, it was found that Holocene loess in CCY only experienced primary process of chemical weathering characterized by leaching of Ca, Na, and not reached the secondary process characterized by leaching of K.
Geochemical characteristics of Holocene Loess-Soil profile on Changchengyuan Loess Table land of Ningxia .
Through the analysis of macro- and micro-elements and their variations with XRF at the CCY loess-soil site, Ningxia Hui Autonomous Region, we obtain a number of geochemical parameters. There is a good comparison between these chemical parameters and magnetic susceptibility, frequency dependent susceptibility, which indicates that during the paleosol formation, the climate was warm and humid with abundant precipitation and greater eluviation, while during the loess accumulation, the climate was relatively cold and arid with weak pedogenesis. And the variation of elements can indirectly reflect the change of climate and pedogenic environment during the process of loess chemical weathering. Through the research of the activities of elements in CCY profile, it was found that Holocene loess in CCY only experienced primary process of chemical weathering characterized by leaching of Ca, Na, and not reached the secondary process characterized by leaching of K.
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宁夏长城塬全新世黄土-古土壤序列微形态特征及意义 [J].
<FONT face=Verdana>利用偏光显微镜对宁夏长城塬全新世黄土-古土壤序列(CCY)的微形态特征进行了详细观察和分析。结果表明,S0层的粗颗粒形态参数（如C/F(10 μm)、面积、周长、等圆直径等）以及土壤形成物、孔隙、微垒结等微形态指标明显区别与黄土层L层,其中C/F(10 μm)值在全剖面中达到最小值,孔隙度达到最大值,残积黏土铁染程度最强烈,指示出古土壤S0层受到的风化作用较为强烈,成壤强度较强。同时,微形态变化能够与磁化率、CaCO3、粒度含量变化进行良好的对比;通过对比得出C/F(10 μm)值、孔隙度、土壤形成物存在形式也可作为指示气候变化的一个重要指标。</FONT>
Significance of micro-moephological features of the Holocene loess-paleosol profile in loess plateau .
<FONT face=Verdana>利用偏光显微镜对宁夏长城塬全新世黄土-古土壤序列(CCY)的微形态特征进行了详细观察和分析。结果表明,S0层的粗颗粒形态参数（如C/F(10 μm)、面积、周长、等圆直径等）以及土壤形成物、孔隙、微垒结等微形态指标明显区别与黄土层L层,其中C/F(10 μm)值在全剖面中达到最小值,孔隙度达到最大值,残积黏土铁染程度最强烈,指示出古土壤S0层受到的风化作用较为强烈,成壤强度较强。同时,微形态变化能够与磁化率、CaCO3、粒度含量变化进行良好的对比;通过对比得出C/F(10 μm)值、孔隙度、土壤形成物存在形式也可作为指示气候变化的一个重要指标。</FONT>
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洛川黄土粒度组成的古气候意义 [J].
<p><正>中国黄土堆积记录了第四纪东亚古季风气候变迁历史<sup>[1]</sup>,黄土古土壤的粒度作为季风气候变化的替代性指标得到了广泛应用<sup>[2-7]</sup>.除了从黄土中分离的石英粒度可作为较好的冬季风强度指标外,在黄土全样粒度指标的选用上还存在着不确定性,现在常用到的就有“中值粒径”、“粗细颗粒比值”<sup>[4,5]</sup>、“粗颗粒含量”<sup>[6,7]</sup>等多种,究竟哪一个粒度指标可以作为较敏感的古气候变化代用指标是值得深入研究的.本文以倒数第2次间冰期(S2)以来洛川黄土堆积为例探讨这个问题.</p>
Paleoclimate significance of grain size composition of Luochuan loess .
<p><正>中国黄土堆积记录了第四纪东亚古季风气候变迁历史<sup>[1]</sup>,黄土古土壤的粒度作为季风气候变化的替代性指标得到了广泛应用<sup>[2-7]</sup>.除了从黄土中分离的石英粒度可作为较好的冬季风强度指标外,在黄土全样粒度指标的选用上还存在着不确定性,现在常用到的就有“中值粒径”、“粗细颗粒比值”<sup>[4,5]</sup>、“粗颗粒含量”<sup>[6,7]</sup>等多种,究竟哪一个粒度指标可以作为较敏感的古气候变化代用指标是值得深入研究的.本文以倒数第2次间冰期(S2)以来洛川黄土堆积为例探讨这个问题.</p>
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中国风资料1961-1970 [M].from 1961 to 1970 . |
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New methods for unmixing sediment grain size data [J].https://doi.org/10.1002/2015GC006070 URL [本文引用: 1] 摘要
Grain size distribution (GSD) data are widely used in Earth sciences and although large data sets are regularly generated, detailed numerical analyses are not routine. Unmixing GSDs into components can help understand sediment provenance and depositional regimes/processes. End-member analysis (EMA), which fits one set of end-members to a given data set, is a powerful way to unmix GSDs into geologically meaningful parts. EMA estimates end-members based on covariability within a data set and can be considered as a nonparametric approach. Available EMA algorithms, however, either produce suboptimal solutions or are time consuming. We introduce unmixing algorithms inspired by hyperspectral image analysis that can be applied to GSD data and which provide an improvement over current techniques. Nonparametric EMA is often unable to identify unimodal grain size subpopulations that correspond to single sediment sources. An alternative approach is single-specimen unmixing (SSU), which unmixes individual GSDs into unimodal parametric distributions (e.g., lognormal). We demonstrate that the inherent nonuniqueness of SSU solutions renders this approach unviable for estimating underlying mixing processes. To overcome this, we develop a new algorithm to perform parametric EMA, whereby an entire data set can be unmixed into unimodal parametric end-members (e.g., Weibull distributions). This makes it easier to identify individual grain size subpopulations in highly mixed data sets. To aid investigators in applying these methods, all of the new algorithms are available in AnalySize, which is GUI software for processing and unmixing grain size data.
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Bimodal grain-size distribution of Chinese loess, and its palaeoclimatic implications [J].https://doi.org/10.1016/S0341-8162(03)00109-7 URL Magsci [本文引用: 1] 摘要
Grain-size analysis indicates that Chinese loess generally shows a bimodal distribution with a coarse and a fine component. The coarse component, comprising the main part of the loess, has pronounced kurtosis and is well sorted, which is interpreted to be the product of dust storms generated by low-altitude northwesterly winds. Its grain-size reflects the strength of the low-altitude circulation in the dust seasons of the year, and its percentage provides an indicator of the source area aridity and the frequency of dust storms. Conversely, the fine component has a wide grain-size range and is poorly sorted. Sedimentary illustrations based on the grain-size distribution characteristics of bulk samples and of detrital quartz suggest that the fine component probably represents the background dust load of the atmosphere and is mainly transported by high-altitude westerly airstreams. Its grain-size provides an estimate of the westerly air stream intensity. The coarse and fine components of a loess sample can be mathematically separated by fitting a designated mathematical distribution function to the measured grain-size data, and this procedure constitutes an approach for reconstructing the palaeowind system of Northern China.
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| [21] |
黄土高原西部地区黄土粒度的环境指示意义 [J].
通常把>30μm颗粒含量作为冬季风的替代指标。对黄土高原西部地区的兰州九州台剖面、西宁土巷道剖面粒度主成分和聚类分析表明: >40μm颗粒的含量是黄土高原西部地区更为敏感的古冬季风替代指标, <2μm颗粒的含量的变化所指示的古气候意义可能与黄土高原中部地区不同。
Environmental significance of grain size of Loess-paleosol sequence in western part of Chinese Loess Plateau .
通常把>30μm颗粒含量作为冬季风的替代指标。对黄土高原西部地区的兰州九州台剖面、西宁土巷道剖面粒度主成分和聚类分析表明: >40μm颗粒的含量是黄土高原西部地区更为敏感的古冬季风替代指标, <2μm颗粒的含量的变化所指示的古气候意义可能与黄土高原中部地区不同。
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| [22] |
Variation of winter monsoon intensity on the Loess Plateau, Central China during the Last 130, 000 Years [J]. |
| [23] |
Towards an orbital time scale for Chinese loess deposits [J].https://doi.org/10.1016/0277-3791(94)90124-4 URL [本文引用: 1] 摘要
In this study, we analyzed the grain size of the Baoji loess-soil sequence at 10 cm intervals. Results show that grain size variations are very sensitive to loess-soil alternations, with loess units being much coarser than soils. Such a change in loess-soil grains is interpreted as the result of the glacial-interglacial cyclic variations in the intensity of the winter monsoon winds out of Siberia. The grain size record is thus employed as a proxy indicator of the winter monsoon circulation and tuned to the orbital records calculated recently by Berger and Loutre (1991) under the control of major magnetic reversals. The tuning is independent of any correlation with O signals in the deep-sea sediments. The resulting grain size time scale is tightly constrained, as suggested by the following facts: (1) the filtered obliquity and precession components from the grain size data on the orbital time scale closely match the theoretical orbital records; (2) ages of the major magnetic reversals estimated from the grain size time scale are in good agreement with the {K}/{Ar}-dated ages; (3) there is close coherence between the Baoji grain size time series and the orbital variations at the orbital frequency bands over the entire 0-2.5 Ma period; and (4) the grain size record on the orbital time scale shows a close similarity to the orbitally-tuned DSDP Site 607 and ODP Site 677 O records. Examination of time-dependent characteristics of the grain size record suggests that there are two major shifts of dominant periodicities in the long-term monsoonal cycles, one occurring at about 0.8 Ma BP and the other around 1.7 Ma BP.
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| [24] |
Correlation between climate events in the North Atlantic and China during the last glaciation [J].https://doi.org/10.1038/375305a0 URL [本文引用: 1] 摘要
Presents a correlation between climate events in the North Atlantic and China during the last glaciation. Examination of grain-size sediments from Chinese loess and intercalated accretionary palaeosols; Evidence of similar climate signals.
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| [25] |
中国内陆大气颗粒物的搬运、沉积及反映的气候变化-Ⅰ.现代大气气溶胶 [J].Climatic change reflection by transport of particulate matter, deposition in China inland - I. Modern atmospheric aerosols . |
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