贵州省麦岗水库沉积物磁性特征及其与粒度的关系

对贵州省麦岗水库沉积物环境磁性特征的研究表明,亚铁磁性矿物主导了沉积物矿物磁性特征,但同时也存在反铁磁性矿物等其他矿物,超顺磁颗粒在沉积物中广泛存在.在所选矿物磁性参数中,χlf、χfd、SOFT与粒度不相关;χARM、SIRM、F300与粒度相关,但相关系数不高;χARM/χlf、χARM/SIRM和粒度显著相关,可以作为粒度的代用指标.研究结果显示,磁性参数确实可以作为粒度的代用指标.但对比研究表明,在不同沉积环境,甚至相似沉积环境的沉积物中,矿物磁性参数和粒度的关系可能不同,在特定沉积环境中,利用磁性参数作为粒度的代用指标应该在充分研究的基础上进行,使研究结果更为可靠.     

New statistical methods for the comparison and characterization of particle shape

This paper presents novel methods for robust statistical testing of particle shape data. Shape (the relative lengths of three orthogonal axes) is a key property of sedimentary particles, providing information on provenance, transport history and depositional environment. However, the usefulness of shape data, including the ability to make robust comparisons between samples, has been constrained by the absence of a satisfactory definition of the mean shape for a sample of particles. Such a definition is proposed and used to develop confidence regions for the population mean shape using both parametric (theoretical) and computational (bootstrap) methods. These techniques are based on a transform that permits multivariate statistical methods for the analysis of compositional data to be extended to shape. These techniques are validated with reference to a dataset of 169 clast samples and found to perform well. A statistical test on the mean – using the multivariate extension of Student's t-test, Hotelling's T² – is presented. The benefits of the methods presented are demonstrated with reference to a case study. © 2019 John Wiley & Sons, Ltd.     

Anisotropy Effects on Microseismic Event Location

Seismic anisotropy in sedimentary environments is significant—microseismic waveforms often show strong shear-wave splitting, with differences reaching 40% between horizontally and vertically-polarized shear-wave velocities. Failure to account for this anisotropy is shown to result in large microseismic event location errors. A method is presented here for determining the five elastic parameters of a homogeneous, vertical transverse-isotropic (VTI) model from calibration shot data. The method can also use data from mining-induced seismic events, which are then simultaneously located. This simple model provides a good fit to arrival times from coal-environment data, and results in dramatic shifts in interpreted event locations.     

Testing a statistical curve‐fitting procedure for quantifying sediment populations within multi‐modal particle‐size distributions

This paper describes a series of tests designed to evaluate the capacity of a personal computer (PC) based statistical curve‐fitting program called MIX to quantify composite populations within multi‐modal particle‐size distributions. Three natural soil samples were analysed by a Coulter Multisizer, and their particle‐size distributions analysed using MIX software to identify the modes, standard deviations and proportions of their composite populations. The particle‐size distributions of the three natural soil samples were then numerically combined in equal proportions using a spreadsheet program to create synthetic particle‐size distributions of known populations. MIX was then tested on the synthetic particle‐size distributions to see if the modes and proportions it identified were similar to those modes and proportions known to characterize the synthetic particle‐size distributions. The main outcome is that MIX can very accurately describe the modal particle size and proportions of the major composite populations within a particle‐size distribution. However MIX has difficulty in identifying small populations (those contributing <10 per cent of a total particle‐size distribution), particularly when they are located in the central sections of particle‐size distributions, overlain by larger populations, or when positioned in the fine tails of distributions. Despite these minor shortcomings, MIX is a valuable tool for the examination and interpretation of particle‐size data. Copyright © 2005 John Wiley & Sons, Ltd.     

Fully Automated Objective-Based Method for Master Recession Curve Separation

The fully automated objective-based method for master recession curve (MRC) separation was developed by using Microsoft Excel spreadsheet and Visual Basic for Applications (VBA) code. The core of the program code is used to construct an MRC by using the adapted matching strip method (Posavec et al. 2006). Criteria for separating the MRC into two or three segments are determined from the flow-duration curve and are represented as the probable range of percent of flow rate duration. Successive separations are performed automatically on two and three MRCs using sets of percent of flow rate duration from selected ranges and an optimal separation model scenario, having the highest average coefficient of determination R², is selected as the most appropriate one. The resulting separated master recession curves are presented graphically, whereas the statistics are presented numerically, all in separate sheets. Examples of field data obtained from two springs in Istria, Croatia, are used to illustrate its application. The freely available Excel spreadsheet and VBA program ensures the ease of use and applicability for larger data sets.     

玉溪盆地三维速度结构建模

本文以玉溪盆地为例,提出了一种包含数据预处理、模型建立、模型修正和模型检验的建模方法.基于各类数据间不同的可信度,给出了消除各类数据间速度偏差的折减函数.为避免以往模型修正过程中对地震波形数据的依赖以及对地脉动H/V谱进行模拟等复杂问题,本文提出了一种改进的模型修正方法,即根据基阶瑞雷波H/V谱与实测地脉动H/V谱形状变化相似的原则,对模型进行修正.修正依据为:在玉溪盆地中,单个地脉动测点所在位置处的地下速度结构中各沉积层面的深度均增加约15 m时,由该点的地下速度结构得到的基阶瑞雷波H/V谱的波峰周期和波谷周期均增加约0.1 s,且二者分别由盆地内沉积层的深层和浅层的速度结构所控制.由于地脉动数据的获取较方便,因此该模型修正方法具有广泛的适用性,由该方法修正后的玉溪盆地三维速度结构模型经检验具有较高的准确度.      

华北地区剪切波速与深度之间统计关系的通用模型特征研究

剪切波速是区别土动力学和静力学的重要参数,其影响因素包括土层埋深、颗粒形状、颗粒比重、压缩模量、孔隙比、含水率和密度等,其中土层埋深对剪切波速的变化影响较大。本文搜集整理了华北地区10个城市的928个钻孔共10703个测点的剪切波速与土层埋深之间的经验统计关系,探讨华北地区剪切波速随深度变化的特征,并从岩性条件、沉积环境等方面分析其原因。通过对比分析,给出了华北地区黏性土和砂类土剪切波速随深度变化的最佳拟合经验统计关系,并进行实例验证,所得结果可为缺乏数据的区域提供一定参考。     

A revised approach to discriminating sediment transport histories in glacigenic sediments in a temperate alpine environment: a case study from Fox Glacier,New Zealand

Clast shape measurements have developed into a standard method for reconstructing the transport histories of sediments in glacial environments. The majority of studies use the ‘RA‐C₄₀’ covariance approach, with some researchers routinely including clasts of varying lithologies within their samples. The corollary is that variable lithological properties may control clast form and roundness, rather than debris‐transport mechanisms. Despite this, the role of lithology on clast shape in glacial environments has rarely been analysed. Furthermore, some studies have reported difficulties in using the RA‐C₄₀ co‐variance plot in discriminating clasts that have undergone subglacial transport, and clasts that have been modified by fluvial activity. Results from a glacierized valley in a temperate alpine setting indicate that detailed analysis of clast shape where samples are of uniform lithology, although time consuming, is a useful tool in the investigation of deposits in glaciated environments. Copyright © 2012 John Wiley & Sons, Ltd.     

Optical dating and lithic microwaste—Archaeological applications

Lithic microwaste (<1 mm in maximum dimensions) is produced during lithic tools and rock engraving manufacture. For tools or rocks containing quartz, small particles persist as microwaste initially on the ground surface but later at least some particles are incorporated into sedimentary deposits associated with the occupation site. If microwaste is distinguished from naturally occurring sediments, then optical dating of microwaste or its surrounding sediment would provide a mechanism for establishing a terminus-ante-et-post-quem for archaeological deposits. Identification of microwaste is undertaken by comparing the shape of microwaste particles with those from surface sediments, taking particular note of angularity and irregular shapes; and by analysing quartz grain surface morphologies. On the basis of surface features identified on experimental microwaste, particles identified as microwaste are separated from the sedimentary grains. Scanning electron microscopy and light microscopy are used to determine surface differences between pedogenic grains and anthropogenic material from archaeological deposits. Single-grain OSL dating technique is then employed for age determinations for particles identified as microwaste. It has been noted in previous research that microwaste particles may lie within or close to the age boundaries of the surrounding sediments but not necessarily where larger lithic material is found. Microwaste is incorporated into sediment and is not subjected to the same degree of movement as larger lithic waste and stone tools within the deposit. The advantage of dating microwaste directly by OSL is that it removes ambiguity about archaeological association. Archaeological events can be dated directly and correlated with sediment ages from surrounding environments, regardless of post-depositional processes. Sand grains surrounding artefacts are dated, usually leaving open the question of the association of the artefact to the sedimentary level, as the artefact may have been displaced from its original depositional level.     

Grain size characteristics of surface sediment and its response to the dynamic sedimentary environment in Qiantang Estuary,China

The composition and grain size characteristics of sediment in estuarine and coastal environments provide important information on the material source, hydrodynamic environment, environmental events,etc. However, few studies have focused on the sediment characteristics of the entire Qiantang Estuary,particularly, on the correlation between hydrodynamics and sediment properties. Through systematic sampling of the surface sediment in a large area of the Qiantang Estuary, the spatial distribution ch...     

Heat as a groundwater tracer in shallow and deep heterogeneous media: Analytical solution,spreadsheet tool,and field applications

Groundwater flow advects heat, and thus, the deviation of subsurface temperatures from an expected conduction‐dominated regime can be analysed to estimate vertical water fluxes. A number of analytical approaches have been proposed for using heat as a groundwater tracer, and these have typically assumed a homogeneous medium. However, heterogeneous thermal properties are ubiquitous in subsurface environments, both at the scale of geologic strata and at finer scales in streambeds. Herein, we apply the analytical solution of Shan and Bodvarsson ( 2004 ), developed for estimating vertical water fluxes in layered systems, in 2 new environments distinct from previous vadose zone applications. The utility of the solution for studying groundwater‐surface water exchange is demonstrated using temperature data collected from an upwelling streambed with sediment layers, and a simple sensitivity analysis using these data indicates the solution is relatively robust. Also, a deeper temperature profile recorded in a borehole in South Australia is analysed to estimate deeper water fluxes. The analytical solution is able to match observed thermal gradients, including the change in slope at sediment interfaces. Results indicate that not accounting for layering can yield errors in the magnitude and even direction of the inferred Darcy fluxes. A simple automated spreadsheet tool (Flux‐LM) is presented to allow users to input temperature and layer data and solve the inverse problem to estimate groundwater flux rates from shallow (e.g., <1 m) or deep (e.g., up to 100 m) profiles. The solution is not transient, and thus, it should be cautiously applied where diel signals propagate or in deeper zones where multi‐decadal surface signals have disturbed subsurface thermal regimes.     

The effects of particle breakage and abrasion—from simulated fluvial transport,on phosphorus sorption by two soils

Phosphorus sorption studies were carried out on particle size fractions of soils collected from the walls of gullies through a granitic and a sedimentary soil, as well as on particle size classes derived from breakage and abrasion of the 500 to 1400 μm components of these soils. Sorption of phosphorus by the particle size classes of the sedimentary soil was much greater than those of the granite soil, and this also applied to the particles derived from breakage and abrasion. For the original sedimentary soil, sorption of phosphorus by the particle size components was strongly associated with the iron content and less strongly associated with the aluminium content and this also applied to the particles derived from breakage and abrasion. For the granitic soil these relationships were much less precise. A period of vigorous mixing, after 165 hours of gentle mixing, caused release of a proportion of the sorbed phosphorus from all particle sizes of the original granitic soil and for most of the breakage/abrasion derived particles. The released phosphorus was re‐sorbed during a subsequent 48 hour period of settling. Relationships were evident between labile P and sorbed P for the particle size classes of the soils and treatments tested. Because particle size, lithology of the transported sediments and flow dynamics affect the distribution of phosphorus between water and sediments, they can also be expected to effect bio‐availability of phosphorus. Particle breakage and abrasion during sediment transport is another factor likely to influence the bio‐availability of P. Copyright © 1999 John Wiley & Sons, Ltd.     

Sedimentary environment and development controls of the hydrocarbon source beds:Middle and Upper Proterozoic in northern North China

Problem on development control of marine source bed hold in Chinese petroleum industry progression. The Hongshuizhuang Formation,Tieling Formation and Xiamaling Formation in the Middle and Upper Proterozoic are important hydrocarbon source beds in northern North China, and investigation of their sedimentary environments and the controls has great significance for petroleum exploration in North China. Based on sedimentology (sequence stratigraphy), palaeoecology, sedimentary geochemistry, and sedimentary palaeogeography, their development pattern is discussed. All these studies indicate that the development controls of the hydrocarbon source beds include a favorite palaeogeographic location, exceeding propagation of biomes in low and middle latitudes, anoxic environments, enrichment of phosphorus element and the adsorption of clay minerals during the preservation of organic matter in the marine carbonates.     

Differentiating depositional environments and maturity of crude oils using GC-AED benzothiophenic spectra

Organosulfur compounds of crude oils and light oils (condensates), collected from ten Chinese petroleumbearing basins and representing different sedimentary environments, were analyzed and identified using a newly-developed GC-AED technique. The results show that the distributions of organosulfur compounds of crude oils from different sedimentary environments are of obvious difference. The crude oils from marine carbonates are rich in organosulfur compounds and those from the source rocks in an ocean-land interchanging facies and a littoral facies have a high abundance of organosulfur compounds, while no or less organosulfur compounds of crude oils from a fresh-water lacustrine facies and a swamp facies were detected in the detectable abundance range of the instrument. This analysis gives a new effective method for oil-source correlation. We also tried to relate the various parameters of benzothiophenic compounds of crude oils with the methane carbon isotope of associated natural gases to discuss the thermoevolutionary degree of crude oils and natural gases.     

Establishing the sediment stratigraphy of reservoirs in the southern Pennines,UK

Abstract

Reservoirs in the southern Pennines have been investigated to determine their potential for reconstructing a history of atmospheric pollution. A selection procedure has been used to identify sites with the best chance of obtaining a usable sedimentary record prior to sample collection. Five reservoirs were selected for core collection and sediment analysis using magnetic susceptibility (χlf), particle size, spheroidal carbonaceous particle (SCP) analysis and radiometric dating. Analysis reveals that largely undisturbed sedimentary records exist in the deepest zones of these reservoirs, thus reservoir sediments represent a valuable resource for investigating pollution histories in the southern Pennines.     

Detection ranges and uncertainty of passive Radio Frequency Identification (RFID) transponders for sediment tracking in gravel rivers and coastal environments

Since the earliest use of this technology, a growing number of researchers have employed passive Radio Frequency Identification (RFID) transponders to track sediment transport in gravel rivers and coastal environments. RFID transponders are advantageous because they are inexpensive, durable and use unique codes that allow sediment particle mobility and displacement to be assessed on a clast‐by‐clast basis. Despite these advantages, this technology is in need of a rigorous error and detection analysis. Many studies work with a precision of ~1 m, which is insufficient for some applications, and signal shadowing can occur due to clustering of tagged particles. Information on in‐field performance is also incomplete with respect to burial and submergence, especially for different transponders and antennae combinations. The objectives of this study are to qualify and quantify the factors that influence the detection zone of RFID tracers including antenna type, transponder size, transponder orientation, burial depth, submergence and clustering. Results of this study show that the detection zone is complex in shape due to a set of lobes in the detection field and provide a better understanding of transponder detection shape for different RFID transponder/antenna combinations. This study highlights a strong influence of clustering and submergence, but no significant effect of burial. Finally we propose standard operating procedures for tagging and tracking in rivers and coastal environments. Copyright © 2014 John Wiley & Sons, Ltd.     

A study of pore geometry effects on anisotropy in hydraulic permeability using the lattice-Boltzmann method

We hypothesize that anisotropy in soil properties arises from pore-scale heterogeneity caused by the alignment of aspherical soil particles. We developed a method to predict the permeability tensor from particle shape and packing structure. Digital geometry maps were created for the pore space in regular cubic and random packs of particles with various aspect ratios using a numerical packing algorithm. The lattice-Boltzmann method was used to simulate saturated flow through these packs, and the effect of particle shape and degree of alignment on the permeability tensor was characterized. Results show that the degree of anisotropy in permeability depends not only upon particle shape and alignment, but also on the three-dimensional structure of the pack. In random packs, more oblate particles and higher degrees of particle alignment lead to reduced permeability perpendicular to the direction of particle alignment compared to the direction parallel to particle alignment.     

MET-IRSL used to track pre-depositional sediment transport history

This paper explores a series of single grain MET-IRSL (multiple elevated temperature infra-red stimulated luminescence) determinations undertaken in order to assess the potential of this approach, developed over the last decade and previously applied to a range of applications, in determining how eroded material moves through environments. Three different approaches are explored here, namely: i) an assessment of the potential to use the technique for improving the robustness of IRSL or P-IR-IRSL age estimates by identifying only well-bleached grains, ii) a means to characterise patterns of grain transport within a catchment using a newly established parameter, the “burial-bleach ratio”, and iii) a novel proxy that responds to changes in light availability through time, here referred to as palaeophotochronometry. For the second approach that we explore, a direct comparison of the MET-IRSL results from several sites with particle size analysis (PSA) data for the same sediment is included. This comparison highlights striking similarities between dispersal of single grain (SG) MET-IRSL burial-bleach ratio data and PSA distributions for some samples, suggesting that we may be able to place a timescale on the acquisition of this fundamental sedimentary characteristic. Common to these three SG MET-IRSL approaches is the importance of characterising and interpreting the previous bleaching records for individual grains.