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The AAPG/Datapages Combined Publications Database
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In 1961 and 1962, SCUBA divers examined nearshore sands off southeastern Virginia and collected surface samples and 52 short cores, 2 inches in diameter and up to 4 feet long. The samples were analyzed by standard laboratory procedures.
Two relict populations were recognized: (1) a coarse-grained (median about 1.5 phi) brown sand; and (2) a fine-grained (median about 3.3 phi) gray sand. The brown sand exists principally in linear ridges, whereas the gray sand occupies lower areas between ridges. The two sands are found interbedded in layers up to 10 cm. thick in cores taken from the landward side of a nearshore submarine ridge off False Cape. Though both sand populations have been derived from reworking of older Pleistocene deposits, both contain abundant Recent shell debris.
Ripples covered the bottom continuously from just outside the surf zone outward to the outer limit of effective wave action, which varied from a line about 3 miles offshore in water 28 feet deep after a period of calm weather, to a line more than 9 miles offshore in water 71 feet deep after a moderate storm. Long axes of all active ripples measured were parallel to shore in spite of a 90-degree divergence (NE to SE) in direction of wave approach. Farther offshore ripples occur only on submarine ridges.
Differential impregnation of longitudinally cut core surfaces with epoxy cement revealed numerous primary sedimentary structures, chiefly cross-laminae of both normal and oversteepened dip and burrow structures.
Four stations were occupied in the summers before and after the intense storm of March, 1962. Cores collected here illustrate the principle of shelf sedimentation generally attributed to Barrell (1917) but first propounded by H. C. Sorby (1857) that a slow average rate of vertical accretion is combined with evidence of rapid deposition of individual layers.
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