ABSTRACT

Most theories on the origin of sandy barrier islands are statements that they migrated to the positions where they are now observed. These theories do not explain origins, but only displacements. Many sand barriers were clearly not the product of displacement, hence we need an explanation for birth in situ. Theories based on drowning do not apply to many sandy barriers.

A small sea level drop (e.g., a few feet) would be ample to convert a suitable shoal to a stable sub-aerial island. If there were an abundant nearby supply of sand, this island nucleus would then expand in area.

Several such small sea level drops are now known from middle-to-late Holocene time. Many sandy barrier islands in the study areas date from shortly after the mean sea level high at 2,500-2,800 B.P. A few are earlier than 3,000 B.P., a few are later than 1,500. But island nuclei are relatively common on wide barriers that formed more recently than 3,000 B.P.