the vicinity of Whitewater Bay and in the Ten Thousand Islands area. The lat- 

 ter region forms the northern end of approximately 50 nautical miles of swamps 

 and coastal mangrove forest; this belt of paralic swamps is typically 

 1-3 miles broad, although it is as much as 10 miles 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 halophilic 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 years ago after cessation of calcitic mud 

 formation. Within a period of a few hundred to a thousand years formation of 

 in situ fibrous peat in area 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 

 fresh-water 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 . 



Based on the age and elevation of fibrous peat overlying bedrock and 

 fresh-water calcitic sediment, the rise in sea- level across southwestern 

 Florida 3,000-4,000 B.P. stood 9-11 ft. lower; about 3,000 B.P. it stood only 

 4.5 ft. lower. Since ca. 3,000 B.P. sea-level has risen to its present 

 elevation at a steadily diminishing rate. This is interpreted from the rate 

 of clastic sedimentation during the last three millennia in areas near the 

 seaward edge of the swamps. 



Because much geologic and geomorphic evidence attests to the tectonic 

 stability of peninsular Florida since the last interglacial stage, the rise in 

 sea-level is regarded as eustatic in cause and related to post-Valderan melt- 

 ing of continental ice masses. Sea-level has evidently not stood appreciably 

 higher than its present position during the last 5,000 years. This means that 

 the + 10 ft. Silver Bluff shoreline recognized along the eastern coast of the 

 United States, and its equivalent mapped elsewhere in the world, is not a 

 Recent age but probably of Sangamon (last interglacial) or mid-Wisconsinan 

 age . (Author) . 



311 SCHOLL, D. W., and STUVIER, M. 1967. "Recent Submergence of Southern 

 Florida: A Comparison With Adjacent Coasts and Other Eustatic Data," 

 Geological Society of America . Bulletin 78, pp 437-454. 



Submergence data gathered in southern Florida indicate that approxi- 

 mately 4400 years ago (in terms of radiocarbon years) sea-level was about 4 m 

 lower than today's level. Between 4400 and 3500 B.P., sea-level rose at a 

 rate close to 30 cm/100 years (1.0 ft/century). About 3500 B.P., when sea- 

 level stood 1.6 m below its contemporary position, the rate of rise diminished 

 by a factor of five; since 1700 B.P., the rate of rise has averaged only about 

 3 cm/100 year (0.1 ft/century). Because a considerable body of evidence 

 points to the probable tectonic stability of southern Florida in recent time, 

 the recorded submergence is regarded as a measure of an eustatic change in 

 sea-level . 



The Florida submergence curve shows that sea- level has risen more or 

 less steadily to its present level during the last 4400 year. This differs 



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