in strontium. It is thought that part of the additional strontium has been derived from 
the Miami Oolite where it was liberated in the process of the inversion of aragonite to 
calcite, and that it has been transported into the keys and shoals by a process of ion 
diffusion. This interpretation is supported by the strong correlation between Sr and 
mean grain size which indicates that most of the Sr is concentrated in the finer sizes. 
While the overall concentration of Sr has been increased in the cores, there appears to 
be a start in the loss of Sr at the base of the cores. This is attributed to the beginning 
of the inversion of aragonite to calcite. The statistical tests for correlations show that 
there are a great number of weak interdependencies between the ten sediment 
properties studied. This indicates the extremely complex nature of the process of 
carbonate sedimentation. Two of the stronger linear are those which exist between Sr 
and mean grain size, and between standard deviation and mean grain size. The 
replacement of Ca +2 by Sr +2 in the finer grain sizes is possibly indicated by the 
correlation between Sr and mean grain size. The strong negative correlation between 
mean grain size and standard deviation indicates that the finer sediments are the best 
sorted. Since the finer grained materials are considered indicative of low energy 
conditions, good sorting, relatively speaking, appears to be the result of the lack of 
available energy. Higher energies enable greater than average accumulations of coarse 
shell material to be concentrated in the silts, and therefore cause poorer sorting of the 
resulting sediments. Thus the energy-sorting relationship in the carbonate sedimentary 
environment appears to be opposite to that in other detrital sedimentary environments 
where intermediate to high energies are needed for good sorting. The cores for this 
study were collected in 1960 from Pigeon Key, Pigeon Shoal, Bottle Key, Bottle Shoal, 
Stake Key, Stake Shoal, Crab Key, Crab Shoal, Captain Key and Captain Shoal. 
1960 0 
Lloyd, R. M. (1960) Shell chemistry of some Recent and Pleistocene mollusks and its 
environmental significance. Geol. Soc. Amer. Bull. . 71(12):1917. 
(DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE. ABSTRACT ONLY.) Florida Bay is 
used as a model to show how climatic, geographic, and hydrographic factors can 
influence the 18 0/ 16 0 and 13 C/ 12 C ratios and the Sr/Ca and Mg/Ca ratios of shallow- 
shelf marine waters. Some of the variations in water chemistry are reflected in 
variations in the chemistry of mollusk shells collected in the Bay. Geographic isolation 
and high evaporation in the Bay coupled with the influx of freshwater enriched in 18 0 
produce a gradient of increasing H 2 18 0 into the Bay. Dilution of the Bay water by Ca- 
rich freshwater lowers the Sr/Ca in the Bay. The gradient of H 2 1s O in the water is 
clearly reflected in a similar gradient in the carbonate oxygen of mollusk shells. The 
effect of temperature on the carbonate isotopic composition is inadequate to explain the 
variations. Sr/Ca ratios of shells vary but show no simple relationship to environment. 
A gradient of decreasing 13 C in shells going into the Bay is attributed to the 
equilibration of C0 2 derived by oxidation of organic debris in the sediment with the 
carbonate of the water. Analyses of mollusks from sediment cores show that the 
present environmental framework of Florida Bay has existed for the last 3700 yrs. 
Analysis of the fine-grained sediment of the Bay suggests that part of it is derived 
from the Florida mainland. Fossil mollusks from the Pleistocene Caloosahatchee 
formation were analyzed. The 18 0/ 16 0 ratios coupled with geological and faunal data 
indicate an environmental framework strikingly similar to the Florida Bay model. A 
landmass immediately west of the outcrop area is postulated for most of 
Caloosahatchee time. The carbon isotope and strontium data reveal little environmental 
information. 
156 
