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Two sampling profiles were made from the high-tide line to 15 n. mi. seaward of Santa Rosa Island, Florida, to determine the beach-to-offshore sequence of a medium-high energy environment. Preliminary results are based on examination of sediment texture, zoologic collections, scuba observations, epoxy relief casts, X-ray radiographs, and submarine morphology.
A steep profile exists from the backshore to 400 m offshore in a water depth of 8 m. The substrate is composed of clean, well-sorted, white, medium- to fine-grained, crossbedded sand; bioturbation is negligible, and few species or individuals are found. Between 8 and 12 m water depths (horizontal distance of 1 n. mi.), the clean white sand is highly bioturbated, mud layers are present, and the number of benthic species and individuals is high. The seaward limit of this zone is the "relict-recent" boundary.
From approximately 1 to 7 n. mi. offshore (12-36 m water depth), the submarine topography is irregular. The substrate in this zone is composed of "relict," coarse, moderately well-sorted, brown to gray sand, which is crossbedded and bioturbated by heart urchins. Seaward of this zone to 12 n. mi. offshore (maximum depth of 25 m), sediment texture remains unchanged, but crossbedding and the distinct heart-urchin traces are replaced by complete bioturbation, and a second maximum in the number of species and individuals is found. The most seaward samples were taken at 14 to 15 n. mi. offshore in water depths of 32 and 34 m, where the bioturbation is low, and the coarse, clean sand is crossbedded.
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