. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography ALLOCHTHONOUS PATTERNS O F SE DI M E N T A TI O N 335. 76° OO'W % ; GRAVEL :â :â :â :â coarse sand : : (INSET: + ) â¡ MEDIUM SAND (INSET: *1 FINE SAND (INSET: *) 75° 29 W xxvxxv VERY FINE tt SAND (INSET: *) FIGURE 2 5. Grain-size distribution on a portion of the Virginia Beach massif, and adjacent shelf valley. 2. Material moving as bed load (over the coarser basal deposits) mainly well sorted sand and in places first-
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography ALLOCHTHONOUS PATTERNS O F SE DI M E N T A TI O N 335. 76° OO'W % ; GRAVEL :â :â :â :â coarse sand : : (INSET: + ) â¡ MEDIUM SAND (INSET: *1 FINE SAND (INSET: *) 75° 29 W xxvxxv VERY FINE tt SAND (INSET: *) FIGURE 2 5. Grain-size distribution on a portion of the Virginia Beach massif, and adjacent shelf valley. 2. Material moving as bed load (over the coarser basal deposits) mainly well sorted sand and in places first-cycle calcareous sand. 3. Present sea-level deposits (category 2 sediment having come to permanent rest) consisting of large sheets to small patches, which range from gravel and shell gravel to sand and calcareous sands, muddy sands, and mud. The implication is that of a shelf surface moving toward a state of equilibrium with its tidal regime. The degree of adjustment appears to be greater than in the case of the North American Atlantic Shelf, in that there is less preservation of nearshore depositional patterns. As a consequence of the intensity of the hydraulic climate, there is less on shelf storage (category 3) and more material in transit. Locally, sand ridges similar to those of the Middle Atlantic Bight do occur. Like those of the Middle Atlantic Bight, they tend to be grouped in discrete fields. In some cases, it is possible to infer that these ridge fields are in fact shoal retreat massifs, generated by the retreat of a near shore depositional center during the course of the Holocene transgression (Swift, 1975). The clearest case may be made for the Norfolk Banks (Houbolt, 1968; Caston and Stride, 1970; Caston, 1972); see Fig. 28. Here a series of offshore sand ridges may be traced into a modern nearshore generating zone (Robinson, 1966; see Chapter 14, Fig. 39) where sand is packaged by the specialized tidal regime of the shoreface into shapes hydrodynamical
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