The development and perpetuation of extensive coal-forming environments require establishment and maintenance of a delicate balance between certain geological and biological processes. Each plant community contributes its own peculiar assortment of source materials to the accumulating sediment, thus influencing the geochemistry of the environment. With and without the influence of geological factors, environmental areas change in size and shape as the result of the phenomenon of plant succession and migration. In swamps and marshes along low plain coasts, rate of subsidence, rate of influx of fresh water, and tide height have profound effects on the vegetation and, hence, on peat-forming environments. Interactions between biological and geological processes in swamps are readily seen in the swamp-marsh complex of southern Florida.
The southwestern coast of Florida is bordered by an ecological zone, here designated the Mangrove Fringe Complex. This includes a variety of environments ranging from small hammocks and natural levees to accretional offshore islands. The Mangrove Swamp environment occupies the greatest area in the Fringe Complex. Under the impact of a transgressing sea this environment has produced carbonaceous sediment that contains a high mineral content, is chemically distinct, and yields a pollen flora with large concentrations of Rhizophora but little Avicennia, in spite of the latter’s considerable representation in the vegetation.
The more inland Everglades Complex includes both marsh and swamp environments. The marsh environments yield either peat or marl, depending on small differences in water-table elevation. The swamp environments occur as circular, elliptical, or irregular areas, their form being related to the rate of ground-water flow. Various types of peat that contrast physically, chemically, and petrographically with the Mangrove Fringe sediments have been formed in these Everglades environments. Currently the latter are migrating over one another, and the environments of the Mangrove Fringe are transgressing over the suite of sediments formed in environments of the Everglades Complex.
