Explanation: core logs and sedimentary facies
	gravel (> 60% gravel)
	gravelly sand (< 3% mud and 25-60% gravel)
	sand (< 3% mud and < 25% gravel)
	muddy sand (3-50% mud)
	mud (> 50% mud)
	Pleistocene facies
	Miocene (limestone and blue-green clay)

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-95-45, an offshore sand ridge, and IR-4 that penetrates the barrier island.

Offshore vibracore retrieval verified that much of the area contains less than 2 m of sediment. All cores contain a surface layer dominated by quartz sand. The surface layers are interpreted to be of open-marine origin. Although the vibracores penetrated to bedrock, there is often little indication of a bedrock reflector seen in the seismic data (see above and at left). A poor impedance contrast between well-sorted shelf sand and the underlying exposure surface appears to be responsible for the lack of a well-defined seismic boundary at the base of the Holocene section.

The expanded coastal cross section reveals a thin wedge of Holocene back-barrier and beach-ridge/dune deposits that have onlapped the steeply rising Miocene limestone and Pleistocene facies of the mainland. Dredging for the Intracoastal Waterway has increased the depth of the back-barrier channel. On cross sections where cores do not penetrate to bedrock, the control is based on probe-rod data.