There are rive geologic formations that make up the southern portion of Florida:
Compressed of highly permeable light colored fossiliferous sands and pockets of quartz 150 feet thick. Named for the Tamiami Trail which follows the upper bedrock of the Big Cypress Swamp, and underlies the southern portion of the Everglades.
Found between the Tamiami Formation and Lake Okeechobee, and named for the river over it. It is much less permeable and the formation is highly calcitic and composed of sandy shell marl, clay, and sand. The water underneath the formation is typically very mineralized. Both formations developed during the Pliocene Epoch.
Shelly limestone, coquina, and sand compose the formation. This represents a former mangrove or salt marsh. The formation is much more permeable and filled with pocks and solution holes.
Miami Limestone (Miami Oolite) and Fort Thompson Formations
These to formations have the most influence on the Everglades. The Miami Limestone forms on the floor of the lower Everglades. It is made up of ooids (tiny formations of egg-shaped concentric shells and calcium carbonate that form around a single grain of sand). Originally, the Miami Limestone was named the Miami Oolite which comprises facies of ooids and fossilized bryozoan organisms. Due to its unique structure, it was some of the first material used in the housing in the early 20th-century in South Florida.
The rock is especially porous and stores water during the dry season in the Everglades. Consequently, the composition of this sedimentary formation affects the hydrology, plant life and wildlife above it. The Miami Limestone also acts as a dam between Fort Lauderdale and Coot Bay.
Under both formations lies the Biscayne Aquifer. This aquifer serves as the Miami metropolitan area’s fresh water source. Rainfall and stored water in the Everglades replenish the Biscayne Aquifer directly.