The Miami Limestone, originally called Miami Oolite, is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...

of limestone in southeastern

Florida Florida is a U.S. state, state located in the Southeastern United States, Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia (U.S. state), Geo ...

. Miami Limestone forms the Atlantic Coastal Ridge in southeastern Florida, near the coast in Palm Beach, Broward and Miami Dade counties. It also lies under the eastern (Miami-Dade County) part of the

Everglades The Everglades is a natural region of tropical wetlands in the southern portion of the U.S. state of Florida, comprising the southern half of a large drainage basin within the Neotropical realm. The system begins near Orlando with the K ...

Florida Bay Florida Bay is the bay located between the southern end of the Florida mainland (the Florida Everglades) and the Florida Keys in the United States. It is a large, shallow estuary that while connected to the Gulf of Mexico, has limited exchange of ...

, and the lower

Florida Keys The Florida Keys are a coral cay archipelago located off the southern coast of Florida, forming the southernmost part of the continental United States. They begin at the southeastern coast of the Florida peninsula, about south of Miami, and ...

from Big Pine Key to the Marquesas Keys. Mitchell-Tapping also states that a component of the Miami Limestone extends under the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United St ...

north to a point 112 kilometers west of

Tampa Tampa () is a city on the Gulf Coast of the U.S. state of Florida. The city's borders include the north shore of Tampa Bay and the east shore of Old Tampa Bay. Tampa is the largest city in the Tampa Bay area and the seat of Hillsborough Cou ...

. The part of the Miami Limestone forming the Atlantic Coastal Ridge and the lower Florida Keys is an oolitic

grainstone Under the Dunham classification (Dunham, 1962) system of limestones, a grainstone is defined as a grain-supported carbonate rock Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are ...

which includes fossils of corals, echinoids,

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is es ...

s, and algae. The oolitic formation in the lower Florida Keys has less quartz sand and fewer fossils than does the oolitic formation on the mainland. Based on those differences, Mitchel-Tapping divided the Miami Limestone into the Fort Dallas oolite on the mainland and under northern Florida Bay, and the Key West oolite, under southern Florida Bay and the lower Florida Keys. The fossils in the formation underlying the Everglades, which does not include any

ooid Ooids are small (commonly ≤2 mm in diameter), spheroidal, "coated" (layered) sedimentary grains, usually composed of calcium carbonate, but sometimes made up of iron- or phosphate-based minerals. Ooids usually form on the sea floor, mo ...

s, consists primarily of a single bryozoan species, '' Schizoporella floridana''. The Miami Limestone was deposited during the Sangamon interglacial, when southern Florida was under a shallow sea. Falling sea levels during the

Wisconsin glaciation The Wisconsin Glacial Episode, also called the Wisconsin glaciation, was the most recent glacial period of the North American ice sheet complex. This advance included the Cordilleran Ice Sheet, which nucleated in the northern North American Cord ...

exposed the formation to air and rain, and rainwater percolating through the deposits replaced

aragonite Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including prec ...

with

calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scrat ...

and formed an indurated rock.

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* Geologic formations of Florida {{Florida-geologic-formation-stub

See also

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