Seven generalized sedimentary-facies types were defined for a unified comparison of core data from the entire study area. All seven color-coded facies for the entire study are shown in the Explanation below. However, not all facies necessarily are present on each transect. Core photographs present individual cores cut into 1-m sections from top (upper left) to bottom (lower right). Discrepancies in core length between the photographs and the diagrams are due to compaction during the coring process. Offshore cores (left) are aligned at core tops. Core locations were chosen to sample thicker Holocene sections and to aid in identifying pre-Holocene stratigraphy. Core elevations were determined from water depth and tide tables. The datum for the barrier-transect cores is the mean lowest low water (MLLW). Core photographs are shown for USGS-95-47 (shelf) and TRI-4 (Long Key).

Offshore cores along transect 5 are among the longest of any recovered in the study area. Cores generally contained a surface layer of well-sorted quartz sand interpreted to represent deposition under open marine conditions. Beneath the surficial quartz-sand units are mud and muddy sand containing numerous burrows and lagoonal foraminiferal assemblages. These units are interpreted to represent back-barrier environments during the Holocene transgression. Many cores also contain a white, fluidized Pleistocene lime mud, probably deposited in a low-energy, restricted environment. This lime mud facies typically occurs in depressions associated with pre-Quaternary solution features or possible late Pleistocene channels. Several offshore cores penetrated to Miocene limestone.

Cores from the landward side of Boca Ciega Bay and in Bear Creek include the organic, muddy sand facies that is interpreted to represent a vegetated paralic environment. Radiocarbon dates from two of these cores were 3,140 and 4,220 YBP, similar to dates in this unit from other locations within the study area. In addition, samples from this unit taken from core TRI-6 located at the mouth of Bear Creek gave dates of 11,780 YBP at the base of the unit at an elevation of -4.3 m and 7,930 YBP at the top of the unit, an elevation of -3.2 m (FitzGerald, 1995). These dates straddle the Pleistocene-Holocene boundary at 10,000 years ago, and suggest continuous deposition across this sequence boundary. These strata are interpreted to represent an eolian strandplain system that was significantly above sea level at the time of accumulation.