believed to represent tidal-bar deposits. Another discrete oolitic tidal-bar belt was 
formed in the area now occupied by the lower Florida Keys. In contrast to the northern 
tidal-bar belt, these oolitic deposits are essentially quartz free and contain less mud 
(predominantly grainstone). In the area between the two tidal-bar belts of Q5 age, a 
highly coraline facies is found similar to those developed during Q3 and Q4 deposition. 
The environment of deposition favored for this coralline facies, as well as those of Q3 
and Q4 age, is that of a migrating sand-shoal-patch-reef complex. This migrating shoal 
may have been initiated at a paleotopographic break in slope on the outer shelf margin 
and does not require a seaward barrier reef for its inception. Pelletal packstone and 
grainstone accumulated in sheltered water behind the sand-shoal-patch-reef complex 
and the oolite bars. These sediments are usually highly burrowed and contain miliolids, 
peneroplids and Schizoporella. Considered as a whole, the Pleistocene record of South 
Florida may be thought of as simple infilling of pre-Pleistocene paleotopography during 
repeated marine transgressions, modified by subaerial exposure and the production of 
discontinuity surfaces during low sea-level stands. 
1977 0 
Rosenfeld, J. K. (1977) Nitrogen diagenesis in nearshore anoxic sediments. Ph. D. 
Dissertation. Yale University, New Haven, CT. 200 pp. 
[DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] Nitrogen is the limiting nutrient 
in the marine coastal environment and one of the major processes affecting its 
distribution is exchange across the sediment-water interface. Therefore, it is 
important to understand the chemistry of hydrogen compounds in sediments. In anoxic 
sediments, the most important processes of nitrogen diagenesis are the decomposition 
of nitrogen-containing organic compounds and the subsequent production of ammonium. 
Changes in the distribution and nature of ammonium and organic nitrogen occur with 
depth in the sediment column and the extent of the change is controlled by the 
geochemical environment of the sediments. In order to better understand the anoxic 
portion of the sedimentary nitrogen cycle, diagenetic changes have been studied in 
different sediment systems (clays vs. carbonates, organic-rich vs. organic poor) and in 
sediments of similar mineralogy, which exhibit different chemical properties (for 
example, different amounts of sulfate reduction). Sediment cores were taken in Long 
Island Sound, Florida Bay, and Pettaquamscutt River, Rl, and changes in the nitrogen 
chemistry, of both the intertidal water and the sediment solids, were measured. 
Ammonium production was found to be related to sulfate production, although once all 
the sulfate is reduced, ammonium is still produced by other process of organic matter 
decomposition. In addition, in Long Island Sound sediments, nitrate reduction is 
generally complete by a depth of 3 cm. Organic nitrogen decreases with depth in the 
sediment column and is utilized preferentially relative to organic carbon. Similarly, 
amino acids and amino sugars are utilized preferentially during diagenesis relative to 
total organic nitrogen. However, the individual acidic and neutral amino acids appear to 
be utilized equally during this stage of organic matter decomposition. Comparison of the 
results from the different cores has pointed out the important role bioturbation plays in 
controlling the chemistry of both the interstitial water and the sediment solids. In the 
laboratory, the processes of ammonium and amino acid adsorption, organic matter 
decomposition, and ammonium diffusion in natural sediments have been studied. There 
appears to be a 'dynamic equilibrium' between the amounts of dissolved, exchangeable, 
and fixed ammonium found in sediments. In Long Island Sound sediments, more than half 
of the ammonium produced by organic matter decomposition is adsorbed by the 
sediment, while the rest is dissolved in the interstitial water. The proportion of amino 
acids adsorbed by sediments is greater than the proportion of ammonium adsorbed and 
in clay sediments, the organic matter, rather than the clay minerals, is responsible for 
most of the ammonium and amino acid adsorption. The organic matter decomposition 
experiments have shown that the rates of sulfate reduction and ammonium and 
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