The area of Florida is 58,666 square miles and the entire land area is covered by Coastal Plain sediments (Fig. no). Cenozoic and Mesozoic sedimentary rocks extend to depths ranging from approximately 2,800 feet in the northern part of the peninsula to more than 15,000 feet at its southern extremity; in west Florida the thickness of the Cenozoic and Mesozoic strata ranges from 8,450 feet in a well in Jackson County to an estimated 15,000 to 20,000 feet at the western boundary of the state. Buried Paleozoic strata that are possibly 2,500 feet thick occupy an area of approximately 20,000 square miles in the northern part of the peninsula. The total volume of the sedimentary deposits in Florida is estimated at more than 135,000 cubic miles.
The sedimentary rocks in Florida range in age from late Cambrian or early Ordovician to Recent, the larger part being of Cretaceous and Tertiary age. Crystalline rocks that are possibly pre-Cambrian were encountered in three wells in central Florida at depths ranging from 5,900 to 8,000 feet. The oldest rocks that crop out are limestones of late middle Eocene age exposed in an area in Levy and Dixie counties on the west coast of the peninsula. Significant regional unconformities are present in the subsurface at the top of the Paleozoic strata; at the base of the Lower Cretaceous throughout the greater part of the peninsula; at the base of the Upper Cretaceous on the Ocala uplift; and at the top of the Upper Cretaceous