Bacteria may play an important role in the precipitation of carbonates, as the consequence of their metabolic activity which alters the physicochemical environment toward increased alkalinity (Monty, 1995). Several mechanisms exist to explain the occurrence of micrite in sedimentary environments, either aerobic or anaerobic, and micrite particles might be generated in-situ by chemical and microbiological precipitation (Monty, 1995). One of these involves the presence of microbial mats, consisting of a "constructional" community of bacteria, along with bacteria involved in the degradation of these organisms (Chafetz and Buczynski, 1992). The occasional occurrence of iron oxides lining the cavity walls suggests that the environment in which micrite 2 precipitated was oxic. Microbes that could survive under these cavity-dwelling conditions possibly relied on a complex heterotrophic or chemotrophic system.