Quartz sands, clayey sands and clays of Plio-Pleistocene age (5.3 ma-30 ka) overlie the Hawthorn Group and occur as a surface veneer ~10 m (33 ft) thick or as elongate ridges that may be over 30 m (98 ft) thick. The ridges are expressions of relict shorelines created during Pleistocene interglacial periods (Cooke, 1945; White, 1970). These ridges and related features that developed during the Plio-Pleistocene sea-level cycles form the current physiography of the Floridan Peninsula (Fig. 7). This physiography is highly perforated by karst terrain.

Faulting within the deeper sediments of Florida have long been a source of controversy (Scott, 1997). Faulting occurred during the late Oligocene to early Miocene and again through the Pliocene to early Pleistocene. Williams and others (1977) suggest the movement created the Ocala Uplift (Fig. 6). Pirkle and Brooks (1959a) believe the uplift was a pre-Hawthorn Group occurrence. Opdyke and others (1984) suggest uplift was due to isostatic rebound in response to loss of the carbonate load by dissolution processes, they reported that at least 12 x 108 cubic meters (4 x 1010 cubic feet) per year of limestone are lost from peninsular Florida. This loss, over a period of 38 ka years could result in a rebound of 33 m (108 ft). A deeper and older (early Cenozoic, 60 ma) feature, the Peninsular Arch, has also caused faulting and fractures. The associated weakening of the rocks provides optimum conditions for dissolution and formation of karst.

The term “fault” as used in this report refers to vertical displacement or discontinuities occuring at a specific site. Primarily, these are faults resulting from sediment slumping into a sinkhole depression, or tension faults. No large scale faults that can be mapped regionally and reflect a tectonic origin were identified.

From the surface geology and physiographic regions, Scott (1988) delineated physiographic provinces for the peninsula. Provinces included in the study are shown below (Fig. 8).