in climate and water table. Figure 

 6 identifies the shoreline types 

 occurring along the mangrove coast 

 of the Everglades. These are parti- 

 cularly important zones to remember 

 since they more or less define the 

 forces that shape the southwest 

 coast environment. 



In the cape sector of Figure 6 

 the Holocene record is dominated 

 by interfingering beach, marl, and 

 peat. Behind the aggrading bar- 

 rier beach on the forefront of the 

 cape are hardwood hammocks, salt 

 marshes, salt barrens, and shallow 

 lakes which in places overlie a 

 continuous peat layer as much as 

 2.7 to 4 m (9 to 13 ft) thick 

 (Spackman et al. 1964, Smith 1968). 

 To the north of the cape sector 

 lies a dissected section of coast- 

 line known as the tidal scour sec- 

 tor. As mentioned earlier, the 

 mangrove forest and underlying peat 

 in this section of the coast are 

 being actively eroded and swept out 

 to sea. 



Recent sediments within White- 

 water Bay itself are gradational in 

 a northeast to southwest direction 

 going from predominantly fresh water 

 to predominantly brackish (Spackman 

 et al. 1964). Bedrock contours in 

 Whitewater Bay reveal a slight ridge 

 (2 m or 6 ft contour) just behind 

 the mouth of the slough entry sec- 

 tor. Islands in Whitewater Bay, 

 which vary from a few square yards 

 to many hectares in area, are gener- 

 ally steep, two-sided sequences of 

 peat overlying a thin veneer of 

 freshwater marl. Within the open 

 water of Whitewater Bay and espe- 

 cially in the mangrove ponds to the 

 northeast, a sediment called "liver 

 mud" (Davis 1940) abounds. This 

 jellolike sediment is believed to 

 result from the mixing of eroded 

 peat with freshwater marl brought in 

 by surface runoff. 



To the south of Whitewater Bay 

 toward Flamingo, recent sediments 

 form a slightly elevated bank of ma- 

 rine marl known as the Flamingo Marl 

 (Davis 1943). This bank is believed 

 to have been heaped upon the shore- 

 line by storm waves (Craighead and 

 Gilbert 1962). Figure 25 presents a 

 general profile of recent sediments 

 from Florida Bay at Flamingo, north 

 through Whitewater Bay. 



The slough entry sector of Fig- 

 ure 6 refers to the area where Shark 

 River Slough and Whitewater Bay 

 enter the Gulf of Mexico. Numerous 

 steeply sloping islands, often cov- 

 ered with straight boled red man- 

 groves 15 to 23 m (50 to 75 ft) 

 tall, dominate the coastline. The 

 islands, like those of Whitewater 

 Bay, are essentially blocks of peat 

 resting on bedrock or thin marl. 

 Occasionally, the upper half of the 

 block may be composed of carbona- 

 ceous mud. Island surfaces are com- 

 monly higher on their gulf or tidal 

 channel exposed sides, thus forming 

 a sort of marl levee. Sediments of 

 the levee are composed of calcareous 

 and siliceous muds which have been 

 heaped up by storms. Some of the 

 mud carries over the island margins 

 and mixes with the accumulating 

 organic matter to form the upper 

 carbonaceous mud layer of the peat 

 blocks. 



To the north of the slough 

 entry sector the coastline is rela- 

 tively smooth, and black mangroves 

 ( Avicennia germinans ) may extend all 

 the way to the shore. This is known 

 as the river sector portion of the 

 coast. Cross sections from cores at 

 the mouth of the Harney River show a 

 buried peat layer extending nearly 

 3.2 km (2 mi) out into the gulf 

 beneath surface marine sediments. 

 These cores provide very convincing 

 evidence of a transgressing sea 

 (Spackman et al. 1964). 



60 



