Gradient-Particle Size Relations on Quartz Monzonite Debris Slopes in the Mojave Desert

The mean size $$\bar{D}$$ of particles mantling quartz monzonite debris slopes in the Mojave Desert is found to be correlated with slope gradient 5, but the $$S-\bar{D}$$ relation is shown to vary from one debris slope to another as a result of differences in joint spacing and mode of weathering of the underlying quartz monzonite. Unlike debris slopes developed on closely jointed and/or mechanically weak rocks, which we have previously shown to be adjusted to present-day hydraulic processes, those developed on quartz monzonite are only partly adjusted. The degree of adjustment of any part of a debris slope varies inversely with gradient and joint spacing. The correlations between S and $$\bar{D}$$ are due to $$\bar{D}$$ decreasing as debris slopes become better adjusted and to debris slopes becoming better adjusted at lower gradients.