. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography CONSTRUCTIONAL SHELF TOPOGRAPHY, DIAMOND SHOALS, NORTH CAROLINA 303 torn sediment reflects the distribution of first-order topographic elements. The map of mean sand sire (Fig. 6) indicates that seaward flanks of sand ridges tend to be composed of fine-grained sand; crests and landward flanks tend to be composed of medium-grained sand. Swales are more variable, containing fine to very coarse sand. Bottom photographs (C and D in Fig. 7) indicate that
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography CONSTRUCTIONAL SHELF TOPOGRAPHY, DIAMOND SHOALS, NORTH CAROLINA 303 torn sediment reflects the distribution of first-order topographic elements. The map of mean sand sire (Fig. 6) indicates that seaward flanks of sand ridges tend to be composed of fine-grained sand; crests and landward flanks tend to be composed of medium-grained sand. Swales are more variable, containing fine to very coarse sand. Bottom photographs (C and D in Fig. 7) indicate that outcrops of stiff clay, or clay veneered with fine gravel, also occur in the swales. Sidescan records (Figs. 8, 9B) indicate that sand in swales tends to occur in elongate ribbons, separated by strips of coarser sand, gravel, or clay outcrop. These coarse strips strongly reflect sound and ap- pear as dark bands on the sidescan records. In the inner part of the study area, zones of mottled bottom occur (Figs. 8, 9A). The "mottles'" appear to be patches of coarser sand several metres in diameter. In some areas they appear to be degraded megarip- ples. Elsewhere their origin is uncenain. A plot of graphic standard deviation against graphic mean (Inman parameters â Inman, 1952) reveals a crudely sinusoidal 30 I . SWELl WAVES 4/ 10 scatter (Fig. 10); see Folk and Ward (1957) and Inman (1949) for discussions of the origin of such a pattern. Three grain-size provinces may be distinguished in Figure lOA. Poorly sorted, fine and very fine sands occur on the Franklin Terrace. Fine sand occurs south of the ridges, whereas medium- and coarse-grained sand occurs on the shelf edge to the northeast of the ridges. Sand in the ridge-and-swale topography forms a scatter that overlaps with the coarse- and fine-grained shelf provinces. When plotted by themselves, coarse, poorly sorted landward flank sands are clearly dis- tinguished from fine, well-sorted seaward flank sands (Fig. lOB)
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