THE DETERMINATION OF THE DIRECTION OF TRANSPORT OF FLUVIATILE ARENITES BY ORIENTATION ANALYSES OF THE DETRITAL MICA

A simple method of determining the strike and dip of the AB planes of mica flakes in etched slides of arenaceous sediments by means of a universal stage mounted on a stereomicroscope is described. The polar stereograms constructed from such measurements in fluviatile sandstones show monoclinic symmetry due to up-current imbrication which compares well with the orientation of plant fossils, current bedding structures and the general current pattern. An angular discordance exists between these features and the direction of sole marks. An example is given of how analyses of the orientation and imbrication of mica flakes can assist in the solution of sedimentation problems of coalfield geology.