Computer analysis of orientation data in structural geology

Three-dimensional orientation data can be simplified by transforming them to refer to axes related to the symmetry of the distribution. Three uncorrelated scalar variates are generated by the transformation. Each of the scalar variates generally has direct geological significance. Each variate can be described by the usual statistical parameters. Thus, the orientation, tightness, asymmetry, shape and size can be measured statistically; first in the direction of greatest buckling; second, parallel to the fold axis. The degree to which a fold is cylindrical or conical in form can be estimated by a least-squares method. A Fortran IV program has been written to perform the computations. A consideration of the spatial variation of the parameters allows various types of folding to be discriminated quantitatively, and permits the testing of hypotheses of the origin of folding.