OPEN-FILE REPORT 92


 The Suwannee Limestone underlies the Perry Karst/San Pedro Bay in this area. In the San
Pedro Bay, a clay layer up to five feet (1.5 meters) thick overlies the limestone, providing
confinement to the Floridan aquifer system (FAS) (Copeland, 1982). Plio-Pleistocene sediments
cover the entire area, and the unit is poorly to very poorly drained. Recharge to the FAS is low to
moderate in San Pedro Bay, while recharge to the FAS may be moderate to high along the transition
from San Pedro Bay to the Perry Karst.

 Woodville Karst Plain

 The Woodville Karst Plain, which has very common karst features, springs, disappearing
streams (swallets), and resurgent streams, extends from Wakulla and Leon Counties southward to
the Taylor-Dixie County line (Figure 3 on OFMS 99-03). Elevations, in general, range from sea
level to approximately 50 feet (15.2 meters) above MSL. A number of rivers and streams traverse
the Woodville Karst Plain, including the St. Marks, Aucilla, Wacissa, and Econfina Rivers. Relief
is very low over the entire area and drainage is poor, resulting in vast swamps. Sand dunes occur in
various portions of the karst plain. An impressive dune field lies in the south-central portion of the
study area, with dune crest elevations exceeding 65 feet (19.8 meters) above MSL.
 Tertiary carbonates underlie the entire area beneath a thin siliciclastic cover. The Lower
Oligocene Suwannee Limestone underlies the karst plain in Taylor and Jefferson Counties. The
Lower Miocene St. Marks Formation occurs in one small area along the central-west edge of the
map area in the headwaters of the Wacissa River. Springs, swallets and river rises commonly occur
in this area (Scott et al., 2004).

Tifton Upland District

 The Tifton Upland occurs from the Apalachicola River on the west to northwestern
Hamilton County between the Alapaha and Withlacoochee Rivers and extends into Georgia
(Figure 3 on OFMS 99-03). Topographically, the upland is characterized by broad, undulating hills
with a well developed dendritic drainage pattern. Elevations range from less than 100 feet (30.5
meters) above MSL in the major stream and river valleys and in the swamps of the eastern portion
of the district, to 300 feet (91.4 meters) above MSL on the hilltops. Elevations decrease toward the
southern limit of the district. Within the study area, elevations range from approximately 40 feet
(12.2 meters) to nearly 230 feet (70.1 meters) above MSL. Where the uplands make the transition to
the Ocala Karst District, the boundary is marked by the Cody Scarp at elevations ranging from
approximately 50 feet (15.2 meters) to 125 feet (38.1 meters) above MSL. Within the study area, the
Tifton Upland District is subdivided into the Madison Hills and the Tallahassee Hills.
 Siliciclastic sediments belonging to the Hawthorn Group and the Miccosukee Formation
underlie the Tifton Upland in the map area. The Miocene Hawthorn Group occurs as the near-
surface unit in the lower lying areas, while the Pliocene Miccosukee Formation forms the hilltops
within the map area. Sinkholes occur in this district but are much less abundant than in the Ocala
Karst District. Karst features are more common in the Madison Hills than in the Tallahassee Hills.

 Madison Hills

 The Madison Hills extend from the eastern end of the Tallahassee Hills in central Jefferson
County, eastward to eastern Madison County on the west side of the Withlacoochee River. Within