An image analysis procedure for recognising and measuring bedding in seemingly homogeneous rocks

This paper introduces a new procedure - the cube procedure - by which bedding can be recognised and its attitude measured in rocks that appear in the field to be homogeneous. This procedure can be of particular help in collecting basic field mapping data from sedimentary rocks, especially in areas in which outcrop quality is poor. The cube procedure uses image analysis to recognise anisotropy in a rock's fabric, then takes that anisotropy as a surrogate for bedding. The following workflow is involved: (1) take oriented cores from the outcrop being studied; (2) cut oriented cubes from these cores; (3) make digitised images of the faces of these cubes; (4) calculate autocorrelation functions (ACFs) from these images, using the ACF tessellation technique; (5) threshold these ACFs, then fit ellipses to the ACF outlines; (6) calculate the mean orientation of the major axes of the ellipses on each cube face - this serves as an estimate of the bedding trace orientation on that face; and (7) obtain the 3D orientation of bedding for each cube by combining the bedding trace orientations from all the pairwise combinations of mutually perpendicular faces. A test of the cube procedure at an outcrop for which the attitude of bedding is already known shows that it can provide excellent quantitative estimates of bedding attitude. (c) 2012 Elsevier B.V. All rights reserved.