Morphometry of gibber gravel at Mt Sturt,New South Wales

Mt Sturt is a duricrusted residual, from which particles of silcrete are discharged on to flanking slopes and surrounding pediments. Dimensional analysis of the particles yields log‐normal curves, bimodal on the crest but unimodal elsewhere, with an orderly downslope decrease in median dimensions. The rate of decrease appears insufficient to reduce the particles to sand size within conceivable limits of pediment length. Analysis of shape indices gives normal distributions with no significant down‐slope change of index, except for the roundness index which tends to assume distributions of the Poisson type and to increase in value downslope. The general correspondence between observed distributions and theoretical curves is close, although it seems likely that gilgai can disturb to some extent the distribution of dimensions in particular samples.