Character and distribution of hybrid sediment gravity flow deposits from the outer Forties Fan, Palaeocene Central North Sea, UKCS

Seven categories of event bed (1–7) are recognised in cores from hydrocarbon fields in the outer part of the Palaeocene Forties Fan, a large mixed sand-mud, deep-water fan system in the UK and Norwegian Central North Sea. Bed Types 1, 6 and 7 resemble conventional high-density turbidite, debrite and low-density turbidite, respectively. However the cores are dominated by distinctive hybrid event beds (Types 2–5; 81% by thickness) that comprise an erosively-based graded and structureless and/or banded sandstone overlain by an argillaceous sandstone or sandy-mudstone unit containing mudstone-clasts and common carbonaceous fragments. Many of the hybrid beds are capped by a thin laminated sandstone–mudstone couplet (the deposit of a dilute wake behind the head of the turbidity current). Different types of hybrid event bed Types are defined on the basis of the ratio of sandier lower part to upper argillaceous part of the bed, and the internal structure, particularly the presence of banding. Although the argillaceous and clast-rich upper divisions could reflect post-depositional mixing, sand injection or substrate deformation, they can be shown to be dominantly primary depositional features and record both a temporal (and by implication) spatial change from turbidite to debrite deposition beneath rheologically complex hybrid flows. Where banding occurs between lower sandy and upper argillaceous divisions, the flow may have passed through a transitional flow regime. Significantly, the often soft-sediment sheared and partly sand-injected argillaceous divisions are present in cores both close to and remote from salt diapirs and hence are not a local product of remobilisation around salt-cored topography. Lateral correlations between wells establish that sandy hybrid beds (Types 2, 3S) pass down-dip and laterally into packages dominated by muddier hybrid beds (Types 3M, 4) over relatively short distances (several km). Type 5 beds have minimal or no lower sandier divisions, implying that the debritic component outran the sandier component of the flow. The Forties hybrid beds are thought to record flow transformations affecting fluidal flows following erosion and bulking with mudstone clasts and clays that suppressed near-bed turbulence and induced a change to plastic flow. Hybrid beds dominate the muddier parts of sandying-upward, muddying-upward and sandying to muddying-upward successions, interpreted to record splay growth and abandonment, overall fan progradation, and local non-uniformity effects that either delayed or promoted the onset of flow transformations. The dominance of hybrid event beds in the outer Forties Fan may reflect very rapid delivery of sand to the basin, an uneven substrate that promoted flow non-uniformity, tilting as a consequence of source area uplift and extensive inner-fan erosion to create deep fan valleys. This combination of factors could have promoted erosion and bulking, and hence transformations leading to the predominance of hybrid beds in the outer parts of the fan.     

Multiple flow direction algorithms for runoff modelling in grid based elevation models: An empirical evaluation

When pathways for groundwater flow are defined in grid based elevation models, the grid structure creates some obstacles as it only allows for eight flow directions. Earlier algorithms have used arbitrarily designed flow distributions, which have resulted in either too diverging or too converging flow patterns. This study defines a computationally simple distribution function, where the converging nature (x) can be altered. A material of reference flow distributions was produced through simulation in four elevation models. The distribution function was tested for different values on x, against the reference. The results show a stable correlation pattern between the tested function and the reference. Optimum values on x were found, which suggest that the flow distribution from a grid cell should be weighted with the slope gradient raised to the power of 4–6.     

Quality assessment of linear data

This paper presents methods to evaluate the geometric quality of spatial data. Firstly, a point‐based method is presented, adapting conventional assessment methods whereby common points between datasets are compared. In our approach, initial matches are established automatically and refined further through interactive editing. Second, a line‐based method which uses correspondences between line segments is proposed. Here, the geometry of line segments in vector is transformed into a set of rasterized values so that their combination at each pixel can restore their original vector geometry. Matching is performed on rasterized line segments and their matching lengths and displacements are measured. Experimental results show that the line‐based approach proposed is efficient to evaluate the geometric quality of spatial data without requirements of topological relationships among line features.     

SHORT COMMUNICATION USE OF A LINEAR FUNCTION OF SEVERAL VARIABLES IN SIMPLEX OPTIMIZATION AS A PROCEDURE FOR ASSESSING ANALYTICAL VERSATILITY IN FIA

A linear response function RF=C_H R_H+C_T(1-R_T)(R_H=peak height,used as a measure of‘sensitivity’,and R_T=analysis time,1-R_T,used as a measure of sampling rate)was used to optimize aFIA system for the determination of nitrite in water with respect to four experimental parameters(twotube lengths and two flow rates)by a Simplex procedure.The weights C_H and C_T placed on R_H and R_Twere systematically varied to cover their allowed range and the system obtained in each optimizationexperiment was implemented and evaluated by determining the following analytical parameters:reproducibility,limit of detection and sampling rate,It was found that these depend very markedly onthe weights used in the response function.Hence the use of a linear function for optimization provides auseful procedure for assessing the versatility of the experimental technique and for choosing the systemsfor its implementation in different practical situations.     

Cosmological Models With Negative Constant Deceleration Parameter In Lyra Geometry

Bermann [Nuovo Cimento B (1983), 74, 182] presented a law of variation of Hubble’s parameter that yields constant deceleration parameter models of the Universe. In this paper, we study some cosmological models with negative constant deceleration parameter within the framework of Lyra geometry. PACS Nos: 98.80 cq, 04.20 jb, 04.50     

云南东川市泥石流及其防治管理

本文全面概述了东川泥石流的灾害历史和危害现状，系统阐述了自５０年代以来的泥石流防治工程技术和管理办法，并且总结了防治工作的成功经验。     

Reducing the grid orientation dependence of flow routing on square-grid digital elevation models

Topographical parameters derived from digital elevation models by employing flow routing algorithms may depend on the orientation of the square grid. Grid orientation dependence results from the insufficient isotropy of square grid and affects the flow directions and subsequent calculations based on flow routing. In this article, a systematic approach for analysing the rotational invariance of flow accumulation calculations is presented and applied. Computed flow accumulation maps are found to depend strongly on the grid orientation, especially if flow routing methods with low dispersion are used. It is also shown that isotropy of flow routing algorithms can be significantly improved by introducing a numerical parameter resulting in adjustable weighting for cardinal and diagonal directions in flow routing. The actual value of this parameter depends on the used flow routing method.     

昆明市东川城区后山泥石流灾害修复措施

东川城区后山构造发育、地震频繁、山体失稳、地形高差悬殊和雨量集中且暴雨强度大等，是导致本区泥石流频繁而猛烈的根本原因。人类不合理的经济活动则对本区泥石流的发生发展起着重要的加剧、恶化作用。对东川城区后山泥石流的治理必须采用软件和硬件两大措施相结合的综合治理办法，并对治理过的泥石流沟加强管理力度。     

湄洲湾中央深槽及白牛浅滩的成因探讨

通过流场和地形特征的分析，研究湄洲湾中央深槽及白牛浅滩的形成机理。从湾顶延伸至口外的中央深槽，在半岛、岛屿和岬角控制下，由潮流塑造而成，但发育过程各段不尽相同，有涨潮流作用为主、落潮流作用为主和涨落潮流共同作用的三种类型。白牛浅滩的地貌形态，似沙嘴，如沙脊，又像独立的堆积体，形成模式与众不同，是湄洲湾中一个特殊的浅滩。