ABSTRACT

The concept of fabric shape provides a powerful means of visualizing and analyzing data on sedimentary fabric. The shape of a fabric is defined in terms of the ratios between eigenvalues S₁ S₂, and S₃, derived using the orientation tensor method. A continuum of all possible orthorhombic fabric shapes can be clearly represented on equilateral ternary diagrams originally developed for the presentation of particle-shape data. Two indices are of particular value in scaling these diagrams: fabric isotropy (I = S₃/S₁)and fabric elongation (E = 1-(S₂/S₁)). Together, these indices uniquely define the shape of any orthorhombic fabric, and provide a rational and quantitative basis for reconstructing depositional and de ormational processes. Equilateral ternary diagrams provide a more versatile and powerful basis for analyzing fabric data than other eigenvalue diagrams now in use. Use of the diagrams in reconstructing processes of sediment transport and deposition is illustrated using fabric data from subglacial tills and a variety of slope deposits.