Fractal dimensions of diamictic particle-size distributions: Simulations and evaluation

It has been proposed that deformation tills have fractal particle-size distributions, reflecting scale-invariant debris-comminution processes. Numerical simulations, however, show that fractal dimensions (m) typical of deformation tills can be produced by the mixing of Gaussian parent populations, analogous to the mechanical mixing of coarse-, medium- and fine-grained sorted sediments. The simulated distributions have high r(2) values (>0.98) and narrow 95% confidence limits, indicating that fractal analysis cannot distinguish diamictons that have been created by shearing from those formed by other mechanisms, such as the mixing of preexisting sediments. The fractal dimensions of diamictons reflect the relative amounts of coarse and fine material in the distribution, but are not uniquely diagnostic of particular genetic processes.