Acropora cervicornis community was reported killed during this abnormally cold event. 
These studies indicate that the temperature of subtropical bank and Bay waters is 
subjected to depression below 16°C accompanying the outbreak of unusually cold air. 
This superchilled water can have a residence time of days. The cooling process creates 
water masses that are out of density equilibrium with warmer ocean water. Offshelf 
movement of the cold, dense water occurs at particular sites, as shown by time-series 
satellite data. The absence of coral reefs opposite tidal passes in the Florida Keys is 
attributed to this process, which has probably limited development of the entire reef 
tract. 
1977 0 
Roberts, H. H., T. Whelan, and W. G. Smith (1977) Holocene sedimentation at Cape Sable, 
South Florida. Sedimentary Petrol. . 18:25-60. 
A regionally distinct mosaic of sedimentary environments including beaches and beach 
ridges which formed under relatively high-energy conditions through low energy, tide- 
dominated environments to quiescent inland lakes and ponds, exists at Cape Sable, south 
Florida. Environments of deposition from the sandy capes inland are: (1) shell beaches 
and beach ridges; (2) black mangrove mudflats; (3) ponded mudflats; (4) exposed 
mudflats; (5) Lake Ingraham; (6) coastal levees and supratidal plain; and (7) ephemeral 
ponds. With exception of the beaches and beach ridges, sediments of the other 
environments are dominantly calcareous muds and silts and represent a depositional 
history related to frequency of tidal inundation and storms. Of the three capes exposed 
roughly from northwest to southeast at Cape Sable, radiocarbon dating shows that 
Northwest Cape formed in the present position or possibly migrated to it 1980 ± 100 
years BP, while Middle Cape and East Cape data from 1610 ± 100 BP and 1230 ± 95 
years BP. Relict shorelines features, coastal levees, on the supratidal plain indicate an 
episode of coastal progradation which started 2280 ± 100 years BP and apparently 
ended about 1560 ± 80 years BP. The entire column of Holocene carbonate sediments in 
the cape area rests on a thin, intermittent basal peat which dates 4950 ± 120 years 
BP. Cores through the supratidal plain reveal a basal carbonate-mud sequence much like 
subtidal sediments of modern Florida Bay. This unit has a typical marine carbonate 
mineral suite, numerous shallow-marine mollusks, and an abundance of Thalassia root 
burrows. An intermediate unit characterized by marine-brackish carbonate sediments 
with algal laminations is overlain by massive aragonitic supratidal silts and silty clays. 
The entire sequence is capped by a dark, highly organic zone representative of the 
coastal levee and intervening algal-flat sediments. Trace quantities of dolomite and 
substantial amounts of low-Mg calcite found throughout the cores are considered to be 
of detrital origin. Localized surface concentrations of dolomite associated with the 
coastal levees may have a mixed in-situ and detrital origin. Investigation of the 
extractable organic matter in the intertidal facies of cores through the three prominent 
coastal levees indicates that diagenesis of organic matter has systematically occurred 
from the youngest to the oldest levee. Fatty alcohols and total hydrocarbons increase 
with time while fatty acids decrease. Partial decarboxylation and chemical reduction of 
fatty acids can occur within the time interval of 750 yrs between the oldest and 
youngest coastal levees. Geochemistry of interstitial water from the supratidal-plain 
cores indicated a general increase in chlorinity from the youngest to the oldest coastal 
levee. Chlorinity levels drop at the base of all three cores analyzed which may be 
related to fresher ground water influence from the Miami limestone. Ratios of Ca, Mg, 
and Sr to chloride are remarkably constant throughout the cores. Higher relative Sr ion 
concentration in the core from the intermediate coastal levees may indicate a subtle 
dissolution of aragonite. In general, evidence of diagenesis in these carbonate sediments 
is not readily apparent. 
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