Integrated stratigraphic cross section combining line-drawn interpretation of seismic data, ground-truthed by coring, with a coastal cross section based on vibracores. At point D the line of section is offset to point E1 to pick up the seismic control crossing the bay. Cores in the offshore transect have low cross-shelf correlation potential because they sample different ridge deposits as shown by side-scan sonar imagery and bathymetry data. Offshore sediment thickness reaching over 3 m contrasts with the thinner (<2 m) section nearshore. Over 7 m of Holocene sediment comprises the barrier-island section at this location - reflecting a thicker lower section of channel fill that once occupied this location. In spite of this potential channel erosion, a 2- to 3-m rise in the bedrock relief below Longboat Key at this location suggests that antecedent topography of the bedrock surface may play a key role in barrier-island location and the presence of a wide bay environment landward of the island. Offshore, a relatively flat unconformity between Holocene sediments and the deformed Miocene bedrock suggests little or no antecedent bedrock control on the offshore pattern of sandbody morphologies.
