ABSTRACT

Heavy and light minerals in beach, dune and offshore sands from Lake Erie exhibit a systematic divergence from hydraulic equilibrium; as grain size increases, the heavy: light settling velocity ratio decreases, a condition which can be predicted from pickup equations, and is therefore a hydrodynamic rather than a source phenomenon. Also, the concentration of heavies is positively correlated with the heavy: light velocity ratio. This relationship is explained by a rolling and saltation model, in which larger, lighter grains are most easily removed, leaving behind smaller heavy and light minerals of about the same size but different settling velocities. Analyses of modern sands and Paleozoic sandstones show the latter to exhibit the greatest divergence from hydraulic equilibrium and to ave the lowest heavy mineral concentration, a phenomenon attributed to extensive reworking and recycling.