Shallow Marine Microbial Carbonate Deposits

Abstract

In normal marine, shallow, subtidal carbonate settings, microbial communities that stabilize sediment to some degree are invariably present and typically are composed of a large variety of organisms, including invertebrates that disrupt the community. These diverse communities do not commonly form mats with a distinctive fabric. Only in settings where some environmental condition favors the growth of a small number of species will a microbial mat develop and construct a biosedimentary deposit with a distinctive fabric. Subtidal conditions that will restrict diversity include chemical extremes and frequent sediment movement. In intertidal settings, desiccation-related factors keep diversity low, enabling microbes to flourish. Dramatic microbial community zonations can develop as a result of competitive exclusion and adaptation. Lithification of some mats results from complex biogeochemical processes and is poorly understood.