Paleoshorelines, reefs, and a rising sea: South Florida, USA

The porous limestone bedrock, thin sediment cover, and tectonic stability of the Florida Platform during the past 15 ka BP provide an exceptionally suitable setting for reconstruction of paleoshorelines and onshore projection of future shorelines in a rising-sea scenario. Paleoshorelines for 8, 6, 4 and 2 ka BP show that 1) a series of limestone islands formed, then drowned, along the outer platform; 2) a distinct trough, called Hawk Channel, separated the outer islands from shore; 3) the lower Keys flooded earlier and more rapidly than the rest of the Keys; and 4) Florida Bay and tidal passes through the middle Keys into the bay developed within the past 4 ka BP. Projection of future shorelines onto land shows that most land forming the Florida Keys would flood in a rise of 1 to 2 m and that a rise of little more than 5 m would submerge all land. Offshore reefs would die, while nearshore reefs would shift landward as the mainland shoreline migrated northward. -from Authors