Like the Rocky Glades, this 

 area is distinguished from Shark 

 River Slough by subtle differences 

 in hydrology (hydroperiod) and geol- 

 ogy. In this area the Miami Lime- 

 stone all but disappears while the 

 Fort Thompson Formation, a bedrock 

 feature of the Everglades trough, is 

 gradually encroached upon by a thin 

 veneer of Pamlico sands of late 

 Pleistocene age (Cooke 1945). 

 Farther northwest, the dissected 

 Tamiami formation of the earlier 

 Miocene age lies exposed at the sur- 

 face, only thinly covered by more 

 recent strata (Schroeder and Klein 

 1954, McCoy 1962). 



Coastal Swamps and Lagoons 



To the southwest of these three 

 areas lies the low mangrove and salt 

 marsh dominated zone referred to by 

 Puri and Vernon (1964) as the retic- 

 ulate coastal swamps. These coastal 

 swamps and lagoons extend from the 

 upland limit of periodic saltwater 

 influence to the Gulf of Mexico, a 

 distance of about 16 to 40 km (10 to 

 25 mi). Prominent features that 

 delineate the area are: 



(1) the salt marshes which lie 

 relatively upland; 



(2) the mangrove forests which 

 grow in vast wetland ex- 

 panses and along the shore- 

 lines; and 



(3) the "back bays" or lagoons. 

 The back bays represent a 

 distinct physiographic fea- 

 ture of the area which be- 

 comes more prominent as one 

 moves north along the coast. 



The coastal swamps and lagoons 

 receive the major bulk of surface 

 runoff from the Everglades. When 

 sea level was lower, prior to the 

 recent Flandrian sea level rise of 

 the Holocene epoch, the area inun- 

 dated by freshwater was relatively 

 larger than it is today. As surface 

 waters flowed over this area, dif- 

 ferential solution of the less re- 



sistant bedrock limestone resultec 

 in the formation of freshwater chan- 

 nels. The freshwater runoff also 

 influenced the relative preponder- 

 ance of various peat and/or marl 

 forming environments. 



As sea level subsequently rose 

 to its present level, the more sus- 

 ceptible areas of underlying peat 

 eroded and oxidized leaving anasto- 

 mosing lagoons and "back bays" 

 (Spackman et al. 1964, White 1970). 

 The area is now characterized by 

 fluctuating fresh and saltwater 

 conditions. 



The largest and most conspic- 

 uous of these lagoons is Whitewater 

 Bay. Along its northern boundary 

 the drainage pattern into Whitewater 

 Bay distinctly follows numerous 

 southeasterly trending channels such 

 as the Watson River, North River, 

 and Robertson River. Throughout the 

 bay are numerous islands whose 

 southwest/northeast orientation sug- 

 gest historical erosion of their 

 underlying marl along relict fresh- 

 water channels. To the southeast 

 the bay is confined by a degenerate 

 extension of the Atlantic Coastal 

 Ridge that terminates in the "Cape 

 Sable High" (White 1970). Prior to 

 construction of the Buttonwood 

 Canal, which directly connects 

 Whitewater Bay with Florida Bay, 

 flushing was toward the northwest. 

 The Joe River, which runs parallel 

 to the axis of the bay on its south- 

 western boundary, reflects this re- 

 cent drainage pattern. Both White- 

 water Bay and the Shark River Slough 

 flush to the Gulf of Mexico in the 

 vicinity of Ponce de Leon Bay. 



Where the main thrust of the 

 lower Everglades drainage enters the 

 gulf, conditions are less favorable 

 for the formation of lagoons or back 

 bays (White 1970). Consequently, 

 there is a wide area of coastline 

 north of Whitewater Bay in which 



15 



