THE SHAPE OF ROCK PARTICLES, A CRITICAL-REVIEW
THE SHAPE OF ROCK PARTICLES, A CRITICAL-REVIEW
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DOI：
10.1111/j.1365-3091.1980.tb01179.x
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发表时间：
1980-01-01
期刊：
影响因子：
3.5
通讯作者：
BARRETT, PJ
中科院分区：
文献类型：
--
作者：
BARRETT, PJ
试图区分岩石颗粒形状的各个方面，并通过分析和经验考虑来发现描述这些方面的最合适的参数。岩石颗粒的形状可以用三个独立的属性来表示：形状（整体形状），圆度（大尺度光滑度）和表面纹理。这些形成了观测尺度和对地质过程的响应的三层层次结构。形状可以由通常测量的三个正交轴中的两个独立测量来表示。在常用于二元图的四对独立测量中，两个球度/形状因子对似乎比简单的轴比更有效的鉴别器。在这两个指标中，最理想的一对是最大投影球度和扁长指数，这两个指标在研究范围内均显示算术正态分布。一个独立于三个正交轴的形式度量，以及从它们导出的度量，是李氏的棱角度度量。圆度有三种类型的测量，那些估计角落的平均圆度，那些基于最尖锐的角落，和颗粒轮廓的凸度的测量。虽然每种类型测量不同的方面，但它们并不是相互独立的。只详细考虑角的圆度。由于平均或最尖锐的角落措施本身都不是更客观或更量化的，目的应该决定哪一个更合适。在平均圆度的视觉比较图中，Krumbein的最好。修正的温特沃斯圆度是最令人满意的估计圆度从最尖锐的角落。不应使用Cailleux圆度指数，因为它包括圆度和形状方面。形状是一个很难用来解决沉积学问题的参数。即使是最好的常用程序也受到观察主观性和低鉴别力的限制。由于大量的自然变量及其相互作用，从源物质和过程的角度对颗粒形状进行非生物学解释总是很困难的。对于古老的沉积物，只有从精心计划的研究或相当不寻常的地质情况中，才能期望得到令人满意的结果。
An attempt was made to distinguish aspects of the shape of rock particles, and to discover by analysis and empirical considerations the most appropriate parameters for describing these aspects. The shape of a rock particle can be expressed in terms of three independent properties: form (overall shape), roundness (large‐scale smoothness) and surface texture. These form a three‐tiered hierarchy of observational scale, and of response to geological processes. Form can be represented by only two independent measures from the three orthogonal axes normally measured. Of the four pairs of independent measures commonly used for bivariate plots, the two sphericity/shape factor pairs appear to be more efficient discriminators than simple axial ratios. Of the two, the most desirable pair is the maximum projection sphericity and oblate‐prolate index for both measures show an arithmetic normal distribution for the range investigated. A measure of form that is independent of the three orthogonal axes, and measures derived from them, is the angularity measure of Lees. Roundness has measures of three types, those estimating average roundness of corners, those based on the sharpest corner, and a measure of convexity in the particle outline. Although each type measures a different aspect, they are not independent of each other. Only roundness from corners is considered in detail. As neither average nor sharpest corner measures are inherently more objective or more quantitative, purpose should determine which is more appropriate. Of the visual comparison charts for average roundness, Krumbein's appears best. The Modified Wentworth roundness is the most satisfactory for estimating roundness from the sharpest corner. The Cailleux Roundness index should not be used because it includes aspects of roundness and form. Shape is a difficult parameter to use for solving sedimentological problems. Even the best of the commonly used procedures are limited by observational subjectivity and a low discriminating power. Unambiguous interpretation of particle shape in terms of source material and processes will always be made difficult by the large number of natural variables and their interactions. For ancient sediments satisfactory results can be expected only from carefully planned studies or rather unusual geological situations.