The northern Florida continental shelf is a submerged coastal-plain surface ranging in width from 15 mi (25 km) off Cape Canaveral to 68 mi (110 km) near Georgia. Study of more than 1,134 n. mi. (2,100 km) of high-resolution seismic-reflection profiles, nearly 200 vibratory cores, and four borings, from the inner shelf at -15 to -100 ft (-5 to -30 m) MLW, provides some insight into the Neogene evolution of this sector of the Atlantic shelf. Seismic-reflection profiles of the shallow subbottom to 500 ft (152 m) below the sea floor show six distinct reflection units and five prominent reflectors of regional significance. The lower two units rise southward to a truncated high off the Daytona Beach area. The overlying units apparently were unaffected and antedate the middle t late Miocene formation of this structure. Samples of the upper four reflection units show that the lowest is composed of compact greenish-gray mud; overlying units are dominantly quartz sand. Correlations with onshore stratigraphic data indicate that the lowest (unsampled) unit probably corresponds to the Floridan artesian aquifer which is composed largely of Eocene and Miocene strata. Overlying units consist of Miocene and Pliocene strata.

The uppermost reflection unit contains thin and discontinuous Quaternary deposits on a Pliocene surface that is exposed or within 15 ft (5 m) of the sea floor over much of the inner shelf. Surficial Holocene deposits are believed to have been derived largely by substrate erosion of the quartz-rich Tertiary strata underlying the inner shelf at shallow depth. Modern nearshore and shelf processes now are redistributing the finer fraction of the relict Holocene transgressive deposits.