The Everglades Pseudoatoll (also called a

pseudo-atoll A pseudo-atoll, like an atoll, is an island that encircles a lagoon, either partially or completely. A pseudo-atoll differs from an atoll as established by several authorities, such as how it is formed (not by subsidence, nor by coral). It is consi ...

) was a major

geomorphic Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or n ...

feature of

southern Florida South Florida is the southernmost region of the U.S. state of Florida. It is one of Florida's three most commonly referred to directional regions; the other two are Central Florida and North Florida. South Florida is the southernmost part of th ...

during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

as a paleodepression possibly created by an

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

impact upon the

carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...

Florida Platform at the southern part of what is now

Everglades National Park Everglades National Park is an American national park that protects the southern twenty percent of the original Everglades in Florida. The park is the largest tropical wilderness in the United States and the largest wilderness of any kind east ...

. The pseudo-atoll is surrounded by a raised rim. Its growth as a

reef A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock out ...

system and pseudo-atoll began during the

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

reaching its maximum size of north to south during the

Piacenzian The Piacenzian is in the international geologic time scale the upper stage (stratigraphy), stage or latest age (geology), age of the Pliocene. It spans the time between 3.6 ± 0.005 year#SI prefix multipliers, Ma and 2.588 ± 0.005 Ma (million yea ...

of the late

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Okeechobean Sea, not unlike South Pacific atolls surrounded by a central lagoon. The west side was more developed than the east and south, as was the remainder of the west side. On the western side of this pseudo-atoll lay the Immokalee Reef Tract and chain of islands called the Immokalee Archipelago. The large Hendry Platform lay behind the reef on the east.

Mangrove A mangrove is a shrub or tree that grows in coastal saline water, saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evoluti ...

forests extended southwesterly of the pseudo-atoll along what would be the southwestern Florida coast. To the northwest was the Myakka Lagoon System, a tropical

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

of brackish water. On the east the lay the Miami-Palm Beach Reef Tract with narrow back reef. Between the west and east was the wide and very deep 100-meter (330 ft) lagoon known as the Loxahatchee Trough. The northern part of the pseudo-atoll was the Kissimmee Embayment which was lined with

mud flat Mudflats or mud flats, also known as tidal flats or, in Ireland, slob or slobs, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A global analysis published in 2019 suggested that tidal fl ...

s and jungles of mangrove.

Chronology

The pseudo-atoll's chronology is developed from deposition of a variety of community organisms. The oldest are the early

communities of shallow

intertidal The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of Marine habitat, habitats with var ...

muddy-sand ''

Mercenaria ''Mercenaria'' is a genus of edible saltwater clams, marine bivalve molluscs in the family Veneridae, the Venus clams. The genus ''Mercenaria'' includes the quahogs, consisting of ''Mercenaria mercenaria'', the northern quahog or hard clam, an ...

tridacnoides'' community of clam species, the deep lagoon ''

Nodipecten ''Nodipecten'' is a genus of large scallops, marine bivalve molluscs in the family Pectinidae Scallop () is a common name that encompasses various species of marine bivalve mollusks in the taxonomic family Pectinidae, the scallops. Howev ...

peedeensis'' community of

scallop Scallop () is a common name that encompasses various species of marine bivalve mollusks in the taxonomic family Pectinidae, the scallops. However, the common name "scallop" is also sometimes applied to species in other closely related families ...

s, the shallow lagoon '' Apicula buckinghamensis'' community of tower shell snails, and lagoon coral ''Phyllangia blakei'' community. The second time period is mid-Piacenzian and contains the shallow muddy intertidal ''

Strombus ''Strombus'' is a genus of medium to large sea snails, marine gastropod molluscs in the family Strombidae, which comprises the true conchs and their immediate relatives. The genus ''Strombus'' was named by Swedish Naturalist Carl Linnaeus in 175 ...

floridanus'' (conch) communities, shallow lagoon tower shell snail '' Apicula gladeensis'' community, lagoon scallop ''

floridensis'' community, and the shallow lagoon ''Hyotissa meridionalis'' community of foam

oyster Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not al ...

s. The third time period is the late Piacenzian and contained wave-action related coral zones of open ocean to sheltered basin. The communities are the high energy open ocean ''

Pocillopora ''Pocillopora'' is a genus of stony corals in the family Pocilloporidae occurring in the Pacific and Indian Oceans.Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townville, Australia. They are commonly called c ...

crassoramosa'' community of the coral reef crest. The back reef ''

Dichocoenia ''Dichocoenia'' is a monotypic genus of stony coral in the family Meandrinidae. It is represented by a single species, ''Dichocoenia stokesii'', which is commonly known as pineapple coral, elliptical star coral, or pancake star coral. It is found ...

tuberosa'' community of coral, the low energy back reef ''

Isophyllia ''Isophyllia'' is a genus of stony coral in the subfamily Mussinae of the family Mussidae. Characteristics ''Isophyllia'' is a colonial coral. Budding is always intracalicular, occurring inside the oral disc of the polyp, within the whorl of te ...

desotonsis'' community of coral, the sheltered back reef ''

Stylophora The stylophorans are an extinct, possibly polyphyletic group allied to the Paleozoic Era echinoderms, comprising the prehistoric cornutes and mitrates. It is synonymous with the subphylum Calcichordata. Their unusual appearances have led to a va ...

affinis'' community, and sheltered reef lagoon ''Antillia bilobata'' community of coral. The fourth was during the maximum development of the Myakka Lagoon System estuary and included the mudflat mangrove forests of the '' Pyrazisinus scalinus'' community, and the shallow and muddy lagoon clam beds of the '' Mulinia sapotilla'' community. Later the shallow lagoon mussel shoals of the '' Perna conradiana'' community and shallow lagoon '' Chama emmonsii'' community. The Kissimmee Embayment contained the shallow mangrove forests and mudflat '' Pyrazisinus kissimmeesis'' community of sea snails and sand flats and

turtle grass ''Thalassia testudinum'', commonly known as turtlegrass, is a species of Marine (ocean), marine seagrass. It forms meadows in shallow sandy or muddy locations in the Caribbean Sea and the Gulf of Mexico. Turtle grass and other seagrasses form sea ...

of the '' Siphocypraea kissimmeesis'' community.

References

*Petuch, Edward J. (December 29, 2003). ''Cenozoic Seas: The View from Eastern North America'',

CRC Press The CRC Press, LLC is an American publishing group that specializes in producing technical books. Many of their books relate to engineering, science and mathematics. Their scope also includes books on business, forensics and information tec ...

; 1st edition. {{ISBN, 0-8493-1632-4 Geology of Florida Natural history of Florida Everglades Atolls