Evaluating Clay Microfabric Using Scanning Electron Microscopy and Digital Information Processing

Abstract

Several aspects related to the qualitative and quantitative evaluation of clay microfabric are presented. A digital image processing technique called gradient is used in evaluating clay micro-fabric from scanning electron micrographs. Details are given of three computer programs (histogram.c, average.c and ellipse.c) that provide for the quantitative analysis of the orientation of clay particles. The important aspects related to sample and surface preparation, digital image acquisition, and analysis are explained. Two natural clays, Pennsylvanian fire clay and Pleistocene varved glacial lake clay, considered in the analysis show well-defined preferred and random fabric. The polar histograms of the intensity gradient analysis for the two clays are compared at varying magnifications, and conclusions were drawn. The output data was conveniently reduced to a few parameters that indicate the strength and magnitude of a given orientation. The concept of fabric index is used to quantitativel...