Grand Traverse Bay occupies a drowned preglacial river valley and is separated from Lake Michigan by a shallow sill. The surface sediment of the bay is largely calcareous mud with a high content of organic carbon. The trace-element concentration of acid-peroxide extracts from the sediment is a function of the mean grain size; the higher trace-element concentrations are found in extracts prepared from the finer grained surface sediment.
Fine grain sizes, high organic carbon content, and high trace-element content are found to be similar in surface sediment from the central trough of the East Bay and from three stations in the lower West Bay, an area in which the sedimentation is influenced by the Boardman River. Regression equations that treat mean grain size, expressed in phi units, as the independent variable have been developed; these equations can be used to estimate trace-element content of acid-peroxide extracts prepared from surface sediment. The regression equations show that sediment being deposited in the Boardman plume area of the lower West Bay, compared to surface sediment in other parts of the bay, is enriched in Cu, Fe, Mn, Zn, and organic carbon.