Sources of Aragonite Needle Muds

An argument in favor of direct precipitation of the muds stems from the study of Broecker and Takahashi (1966). They show a decrease in the removal rate of carbonate ion with decreasing supersaturation of the water on the Great Bahama Bank. This correlation would not necessarily occur if the source of the needles were algae. The more recent work of Morse et al. (1984) also shows this trend. There are, however, two problems with this conclusion. The first is that Morse et al. (1984) found a continued strong removal of carbonate ion from the water in the inner part of the bank where whitings are not observed and clear water is present. The second is that nutrient availability is likely to decrease with increasing age of 

COMPOSITION AND SOURCE OF SHOAL-WATER CARBONATE SEDIMENTS 

We will not attempt to review the occurrence and general characteristics of odlites here, because this has been done by several authors (e.g., Milliman, 1974 Bathurst, 1975 Fabricius, 1977 Simone, 1981) however, to quote Cayeux (as translated by Bathurst, 1975), it is remarkable that so large a body of writing should contain so small a measure of achievement. Instead, we will concentrate on the major hypotheses for ooid formation and summarize the chemical characteristics of odids and experimental studies aimed at determining their processes of formation. 

Hypotheses for the formation of odids There are three primary classes of hypotheses for the processes responsible for the existence of odids. They are based on bacterial-mechanical, algal, or chemical mechanisms for odid formation. Some investigators have made hybrid models involving more than one of these mechanisms. Because the previously cited papers cover the literature up to about 1980, we will only present these hypotheses in a general manner and not attempt to reference the large number of papers relevant to the topic. 

Sorby (1879) put forth one of the earliest non-biological hypotheses for the mechanism of odid formation. His basic idea was that odids with a concentric structure form by a process similar to that which forms a snowball. In his model, an organic coating is biologically deposited (the infamous mucilagenous slime ) on 

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