deposited on bedrock or freshwater peat about 4,000 yr ago. This sedimentary 
succession is thought to be the record of a marine inundation of the western margin of 
the extensive freshwater swamps (Everglades) of southern Florida. To map the extent 
of the submergence a stratigraphic study was made of piston core samples of 
unconsolidated sediments underlying waterways dissecting the coastal forest and intra¬ 
forest bays enclosed within it. These cores were primarily taken in the vicinity of 
Whitewater Bay and in the Ten Thousand Islands area. The latter region forms the 
northern end of approximately 50 nautical mi of swamps and coastal mangrove forest; 
this belt of paralic swamps is typically 1 - 3 mi broad, although it is as much as 10 mi 
wide in some areas. Whitewater Bay is situated at the southern terminus of these 
swamps. The sequence of transgressive sediments consists of a basal unit of 
autochthonous {in situ) fibrous peat, largely derived from mangrove and other rooted 
halopllylic plants, and an overlying allochthonous unit of peaty and calcareous shell 
debris (Whitewater Bay) or shelly quartz-rich sand and silt (Ten Thousand Islands 
area). Judging from radiocarbon dates, the basal peat unit began to form 3,000 - 3,400 
yr ago after cessation of calcitic mud formation. Within a period of a few hundred to a 
few thousand years formation of in situ fibrous peat in areas which are now waterways 
and intra-forest bays gave way to the deposition of shelly brackish-water and marine 
sediments of the upper member of the transgressive sequence. The environmental shift 
from freshwater to brackish-water and marine milieus came about in response to a 
more or less steady rise in sea level and marine inundation of former mainland paludal 
swamps. 
1964 0 
Scholl, D. W. (1964) Recent sedimentary record in mangrove swamps and rise in sea level 
over the southwest coast of Florida. Part 2. Mar. GeoL 2:343-64. 
[DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] Coastal mangrove swamps 
formed in the Whitewater Bay region of southwestern Florida about 3,000 yrs ago. 
Development of these swamps and the associated mangrove forest resulted from the 
landward penetration of marine water behind a rapidly constructed or pre-existing 
barrier (Cape Sable). Marine flooding took place over freshwater swamps. By about 
2,000 BP 1 - 2 ft of autochthonous {in situ) mangrove peat had accumulated on top of 
about I ft of freshwater calcitic mud. Continued submergence formed Whitewater Bay 
by destroying the mangrove forest that had deposited the peat. Destruction of the 
forest is recorded by the deposition of peaty shell debris on top of the peat. Farther to 
the north, in the Huston Bay complex region of the Ten Thousand Islands area, 
establishment of the coastal mangrove forest began about 3,500 BP. Mangrove swamps 
initially developed along stream and river banks as a result of the landward penetration 
of marine water. With continued submergence the swamps and mangrove forest spread 
onto inter-channel areas. Eventually, continued marine inundation caused destruction of 
near-channel portions of the forest, especially in backswamp areas. Killing of mangrove 
trees and erosion of peat adjacent to drainage channels aided in producing a chain of 
backswamp bays and connecting channels; the Huston Bay complex forms the northern 
end of this chain of waterways. The Ten Thousand Islands are chiefly mangrove-crested 
bars and shoals of shelly quartz sand. This archipelagic portion of the coastal mangrove 
forest was formed to a large extent by tidal currents and evidently was well developed 
by 3,000 BP. As emphasized in Part 1 of this work, radiocarbon dates on marine shells 
and on organic matter of freshwater calcitic mud can be regarded as reliable. 14C dates 
on the carbonate of calcitic mud, the tests of freshwater gastropods, and fibrous 
mangrove peat may be too old by about 400 yrs. Dates on these materials should 
presently be regarded as maximum values. The ages of brackish-water mollusks from 
the Huston Bay complex of the Ten Thousand Islands area are thought to be of little 
169 
