Using a continuous-flow centrifuge, the suspended sediment concentrations in Narragansett Bay and Rhode Island Sound were measured. An average of 3.17 milligrams of sediment per liter was found in the Bay and 1.83 milligrams per liter in the Sound. Most of the sediment entering the estuary from the tributaries was deposited near the head of the Bay, but a secondary depositional area was found near the center of the Bay in zones of weak and variable currents. The average rate of deposition for the entire bay during the fall months was 0.092 grams per square centimeter per year, and the net transport through the estuary was found to be 10 percent of the tributary sediment load, or 910 grams per second.

Abstract Although the study of Atlantic continental margin physiog- raphy (Plate la) started with lead-line sounding data centuries ago, it was the development and automation of precision echo sounding in the second quarter of the twentieth century that fostered modern investigation and interpretation (Veatch and Smith, 1939; Emery and Uchupi, 1972). Bottom samples ga- thered in the last four decades have strongly influenced the ex- planations for the development of submarine topography (Field and others, 1979; Hollister, 1973; Knebel, 1981; Milliman and others, 1972; Schlee and Pratt, 1970). High-resolution seismic profiling, side-scan sonar, bottom photography, current meters, and submersibles have allowed more detailed examination and interpretation of selected areas. Key recent articles cited in this chapter, from the vast literature about the Atlantic margin, pro- vide references for an up-to-date understanding of the major physiographic features of the shelf, slope, and rise. In addition, controversies and unresolved questions have been identified. For readers less familiar with the location of physiographic features discussed in the text, the map provided should be of considerable assistance. Because the nature of the shelf physiography and the proc- esses responsible for creating the submarine landforms differ markedly along the U.S. Atlantic shelf (Burk and Drake, 1974; Nairn and Stehli, 1974; Emery and Uchupi, 1972; and Uchupi, 1968), six areas are recognized. From north to south they are: 1) Gulf of Maine, 2) Georges Bank, 3) Southern New England,4) Mid-Atlantic from Rhode Island to Cape Hatteras, 5) South-Atlantic from Cape Hatteras to Southern Florida, and 6) the Bahamas. A seventh section introduces the recent literature on microtopography and related sediment transpont.