Abstract
Accumulations of the intertidal clam Donax variabilis (Say) have been recovered from the Cape Kennedy inner-shelf subbottom. Depth of the shell deposits correlates with a marked, widespread sonic horizon that underlies the entire central Florida inner shelf. Composition, texture, and radiocarbon ages of the shelf deposits correlate with available data on adjacent onshore beach ridges and with established sea-level curves.
The occurrence and location of these deposits are considered significant for four reasons: (1) accumulations of D. variabilis may provide a definitive marker in some areas for relict submerged beach deposits; (2) the restricted depth range of these mollusks makes them suitable for refining portions of the sea-level curve that are based on less well defined criteria; (3) shoals and ridges on the inner shelf have often been interpreted as relict barriers, yet off Cape Kennedy these present-day bottom morphologic features (shoals) appear to be unrelated to the relict beach deposits described herein. This suggests that modern shoal formation must be unrelated to relict strand topography; and (4) the rare occurrence of buried Strandline deposits on the shelf in the vicinity of Canaveral Peninsula, which is an area of well-documented beach-ridge accretion, suggests a large-scale planing or truncating of the surface by the last transgression, which has removed all but trace remnants of the previous Strandline morphology. In other shelf areas where beach ridge accretion has been less dominant, therefore, all traces of former strandlines may have been removed.
