ABSTRACT

Marine foreshore and dune sands from New Jersey are distinguished by comparing settling velocities of two or more minerals of differing densities that occur together.

Good environmental separation is obtained by plotting delta values (defined as log median settling velocity of the selected mineral minus log median velocity of associated quartz) against log median quartz velocity. A straight line drawn on such a scatter diagram containing delta values for hornblende from 48 dune and marine beach samples properly classified all but four samples. The technique requires neither paired sampling of adjacent environments nor statistical evaluation of groups of samples. The parameter should respond immediately to the depositional processes that are operating, and should therefore reflect the environment immediately responsible for deposition.

Heavy minerals from marine beach and dune sands settle in water more slowly than would normally be predicted by equivalence with the associated quartz. This seeming anomaly is attributed to the difficulty of entraining small (heavy mineral) grains--a difficulty that must be compensated by a higher ratio of fluid drag to grain mass.