Nocatee Member is a new name proposed here for sediments at the base of the Arcadia Formation of the Hawthorn Group in parts of southwest FL. Interval was previously referred to as the "sand and clay unit" of the Tampa Limestone (Wilson, 1977). Unit is subsurface only. Type core is designated in central DeSoto Co. where unit is 226 ft (69 m) thick. The Nocatee is a complexly interbedded sequence of quartz sands, clays, and carbonates containing variable percentages of phosphate. It is predominantly siliciclastic in the type core. Quartz sands are fine to coarse-grained, occasionally silty, clayey, and calcareous to dolomitic. Clay beds are common and variably quartz sandy, silty, phosphatic and calcareous to dolomitic. Limestone and dolostone are present in variable ratios. The Nocatee overlies strata currently assigned to the "Suwannee" Limestone. Contact appears gradational, but disconformity suggested by paleontology. Unit underlies the Tampa Member (rank reduced) throughout much of the area; elsewhere underlies undifferentiated Arcadia. Age of earliest Miocene is based completely on stratigraphic position. It is older than part of the Tampa, equivalent to part of the Tampa, and younger than the underlying Oligocene carbonates. Unit correlates with the lower part of the type Tampa Member, the lower part of the Penney Farms Formation (new name) of north FL, and the lower part of the Parachucla Formation of southeast GA.

Source: GNU records (USGS DDS-6; Reston GNULEX).

Nocatee Member of Arcadia Formation is used in this report following usage of Scott (1988). 87Sr/86Sr age estimates for Nocatee are late Oligocene (27.1 to 26.3 Ma).

Source: GNU records (USGS DDS-6; Reston GNULEX).