ABSTRACT

The carbonate fraction of over 1,000 samples from the Atlantic continental shelf off the southern United States was investigated. The main purpose of this study is to determine the usefulness of the carbonate fraction in determining various aspects of shelf history in a so-called "non-carbonate" area. "Particle characteristics" of the carbonate fraction are emphasized. These include determination of the degree of particle rounding, percent fragmental, percent blackened, and percent of worn versus fresh components.

The abundance of CaCO₃, is mainly a function of the amount of dilution by terrigenous materials from Piedmont rivers. Calcium carbonate is least abundant on the Georgia shelf and increases greatly to the south and slightly to the north. The abundance of black shells, oolites, and shallow water fauna over large portions of the shelf attest to a shallow-water origin of much of the shelf surficial material. The abundance of worn and broken shells reflects the low rate of sedimentation in this area. Much of the present-day shelf sediment cover was deposited in the nearshore zone of the last transgressing sea but the sediment was not derived from the beach environment itself, as indicated by particle roundness considerations. The areal distribution of certain carbonate fraction arameters can be interpreted as linear patterns paralleling the present shorelines. These may reflect ancient shorelines.