Beacon Slope are part of the Gulf-Atlantic 

 rollinq plain, while the lower coastal 

 lowlands are part of the Gulf-Atlantic 

 Coastal Flats (H, M. Leitman et al. l^^S?). 

 The drainaqe system contains streams of 

 various types, which range from first- 

 order ravine streams (Means 1*^77) to the 

 hiqher order low-qradient, meanderinq 

 types. The latter contain hiqh orqanic 

 acid levels in the flatwoods or are 

 calcareous and clear in the Marianna 

 Lowlands karst plain. Extensive lake 

 systems are lacking in the valley; 

 Ocheesee Pond is located in an abandoned 

 bed of the Apalachicola River, and two 

 other natural lakes (Lake Wimico, Dean 

 Lake) occur in the basin. The upper river 

 region, cutting through Miocene sediments, 

 has a flood plain 1.^-3 km (O.P-l.q mi) 

 wide. This floodplain widens to 3-5 km 

 (1.9-3.1 mi) along middle portions of the 

 river, with the lower river having the 

 widest floodplain (7 km; 4.4 mi). The 

 upstream tidal influence in the floodplain 

 does not extend above km 40 (mi PS). The 

 Chipola River joins the Apalachicola at km 

 45 (river mi ?8). The delta is about 16 

 km (in mi) wide and is surrounded by a 

 broad marsh. 



The previously described geological 

 processes have led to hiqh physical 

 diversity of the land forms in the 

 Apalachicola basin. "Steepheads" or 

 amphitheatre-shaped valley heads with very 

 steep walls (Means 1^77) occur in small 

 drainages that dissect the eastern 

 escarpment between Bristol and Torreya 

 State Park within a narrow east-to-west 

 alignment through the Florida panhandle. 

 These constant environments are important 

 habitats for various species. The 

 Apalachicola Ravines (Figure 7) (Hubbell 

 et al. 1956) are drainages that form 

 another unique habitat associated with the 

 river basin. These ravines include small- 

 order stream bottoms and steep valley 

 slopes; the vegetation qrades upward from 

 hydric plant communities near the bottom 

 to xeric vegetation at the top of small 

 divides between ravines. The Marianna 

 lowlands form a karst plain containing 

 more vadose (i.e., above water table) cave 

 ecosystems than any other part of the 

 coastal plain (Means 1977). The 

 Aoalachicola lowlands, a flatwoods region 

 with little relief, is a low, sliahtlv 

 inclined plain with extensive swamplands. 



The eastern portion of the Aoalachicola 

 lowlands contains parts of the Tate's Hell 

 Swamp, which is undergoing extensive 

 changes due to forestry operations. The 

 western lowlands are part of a cattle 

 ranch and farming operation. The Western 

 Red Hills are separated from the other 

 natural areas by the Chipola River valley. 

 This area is high in elevation but not as 

 deeply dissected as the Apalachicola 

 Ravines. Grand Ridge (Figure 7) is a 

 wedge-shaped area bounded by the Chipola 

 and Apalachicola Rivers. While originally 

 part of the same upland mass that extended 

 from the Apalachicola Ravines westward. 

 Grand Ridge has been eroded. This area is 

 associated with springs, caves, and 

 troglodyte (i.e., subterranean) fauna. 

 The river bottomlands represent a 

 floodplain habitat characterized by the 

 river channel, sloughs, swamps and 

 backwaters, and the periodically flooded 

 lowlands. Many springs and aquatic cave 

 systems empty directly into the river 

 bottomlands. 



?.1.4, Barrier Islands 



At the mouth of the Apalachicola 

 River is a well developed barrier-island 

 system composed of three islands (St. 

 Vincent, St. George, Dog) (Figure 3). 

 These islands roughly parallel the 

 coastline and are characterized bv sets of 

 sand dunes of differing geological ages. 

 While the shore system is based on dunes 

 that date back some 3000 to 6000 years, 

 the barrier islands are no older than 3000 

 years. They consist of quartz sand that 

 has been transported from the southern 

 Appalachian Piedmont by the river system 

 and that currently rests on an eroded 

 Pleistocene surface (Zeh 1980). On St. 

 Vincent Island, for example, qently 

 curvinq lines of beach ridges (Figure 8) 

 up to 1 m (3 ft) hiqh serve as the base 

 for small dunes; such ridqes represent the 

 geological history of sand deposition in 

 the region, with the oldest (northernmost) 

 ridqes indicatinq where sea level achieved 

 its earliest position. 



St. Georqe Island is about 48 km (30 

 mi) lonq and averaqes less than 0.5 km 

 (1/3 mi) in width. It consists of ?,Q73 

 ha (7,340 acres) of land and 486 ha (1,?00 

 acres) of marshes. The medium to fine 

 grain sands provide for relatively poor 



10 



