ABSTRACT
The middle Miocene (Langhian and Serravallian Ages), the late Miocene (Tortonian and Messinian Ages), and the early Pliocene (Zanclean Age) were all times of chaotic climatic conditions, with long, mild spells separated by severe cold periods. During the late Langhian, and also during the exceptionally severe cold time and sea level drop of the early Serravallian, the entire Everglades area was emergent. Feeding on the rich phytoplankton resources, the oyster bioherms grew to massive proportions. Presaging the deltas that formed in subsequent subseas, large amounts of clay minerals were pouring into the Okeechobean basin at the specific time, being discharged from rivers draining into the central lagoon. Typically, the Port Charlotte contains abundant well-preserved molluscan bioclasts, predominantly large scallops, oysters, and muricid gastropods, which make up the greatest part of the carbonate fraction. Dolosilts are occasionally present, but make up only a minor fraction of some facies.
