In October 1969 beaches and water tables were investigated after 5 months of 
adequate rainfall in the Cape Sable complex. In April 1971 a similar study was made 
after 5 months of extreme drought in the Florida Everglades, when water tables were 
lowered and flattened enough to permit widespread saltwater intrusion. Much of the 
beach rock and cemented water-table rock under the beaches had been eroded by high- 
energy waves, probably of Hurricane Laurie (1969) or various local storms. Slabs of 
the eroded beach rock were tossed up on the beaches, and if sufficiently indurated, 
became incorporated into the deposits. No evidence of subsequent cementation was 
observed. On East and Northwest Capes the ground water had been replaced by stagnant 
seawater. On Middle Cape the water table was lowered, but a salinity gradient and 
some potable ground water were present in 1971. The Cape Sable region is isolated 
from mainland surface runoff by extensive areas of lakes and waterways with 
seawater salinities, and from subsurface flow of ground water by a thick section of 
compact marl and compressed peat. Accumulation of ground water depends on local 
rainfall, and its volume varies with size and permeability of catchment areas. The 
conclusions of this study are applicable to many other coastal areas and may be useful 
in assessing their population and survival potentialities. 
1969 - 1971 
Charlton, D. S. (1981) The characterization and evolution of carbonate tidal deltas, upper 
Florida Keys. Ph. D. Dissertation. University of Wisconsin, Madison, Wl. 421 pp. 
South Florida was inundated by the last sea-level rise, initiating tidal exchange between 
Florida Bay and the open ocean at bedrock lows along the Florida Keys. Carbonate tidal 
deltas, composed of mangrove peat and carbonate sediments, formed during the last 
5000 yrs seaward and bayward of tidal channels at Snake Creek, Whale Harbor and 
Tavernier Creek. The carbonate tidal delta system at Snake Creek was the focus of this 
study. Six surface depositional zones of the Snake Creek bayside delta and their 
diagnostic elements recognized in cores, representing environmental gradients from 
most restricted circulation to more open marine conditions, are: (1) BLACK MANGROVE 
ZONE (Cerithidea scalariformis, dolomitic crusts); (2) RED MANGROVE ZONE (peat); (3) 
RESTRICTED POND ZONE ( Anomalocardia auberiana ); (4) OPEN MUD FLATS ZONE 
(Anomalocardia auberiana ); (5) TIDAL DELTA FRONT ZONE ( Turbo castaneus, Tegula 
fasciata, Porites)] and (6) FLORIDA BAY ZONE ( Codakia orbicularis, coarse molluscan 
packstone). Cutting across these zones is the (7) MAJOR CHANNELS ZONE. Snake Creek 
delta provides a microcosm of regional gradients from the Everglades, across Florida 
Bay, to Hawk Channel. This zonation and a similar approach for ocean-side tidal deltas 
were used to interpret Holocene cores along nine cross sections at Snake Creek, Whale 
Harbor and Tavernier Creek. Cores within the proximal bay-side tidal delta plain 
commonly show deepening-upward, transgressive, sequences (subaerial erosional 
surface -> basal peat -> marine carbonates with Thalassia) followed by a shallowing- 
upward, regressive, sequence (carbonates with Thalassia -> peat and red mangroves -> 
carbonates and black mangroves). Mangrove peats are present in proximal cores only. 
Distal bay-side delta cores, composed entirely of carbonates, show a deepening- 
upward, transgressive, sequence (subaerial erosional surface -> coarse basal marine 
carbonates) followed by a shallowing-upward, regressive, sequence (Florida Bay Zone 
-> Delta Front Zone -> Open Mud Flats Zone) representing progradation. Bay-side deltas 
differ from ocean-side deltas because of restricted circulation, greater turbidity and 
lower energy conditions. Ocean-side tidal deltas underwent transgression followed by 
regression. Distal ocean-side cores coarsen upward with decreases in Thalassia roots 
and increases in Porites and Goniolithon due to rising sea level, increasing energy, plus 
upward growth and progradation. Proximal ocean-side cores exhibit fining-upward 
sequences with upward increases in Thalassia roots as buildup and progradation cause 
progressive sheltering of the inner delta. Both bay-side and ocean-side tidal deltas 
record two-phase transgressive/regressive sequences similar to those interpreted for 
195 
