IMAGE-ANALYSIS OF PETROGRAPHIC TEXTURES AND FABRICS USING SEMIVARIANCE

Many subjective descriptive terms such as 'smooth', 'coarse' and 'anisotropic' are routinely used to convey properties of textures and fabrics, but these aspects of geological objects are not easily quantifiable. The use of directional semivariograms of image greylevels is assessed for this purpose. These quantify anisotropy of 'coarseness/fineness' by using semivariogram ranges, and 'roughness/smoothness' by using semivariogram sill values. These can be summarized by ellipses derived from semivariograms ranges and directions. The method will find applications in analysis of rock thin sections as well as analysis of surface texture of grains and microfossils.