The Choctaw Sea was a

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

eutropical subsea, which along with the Okeechobean Sea, occupied the eastern

Gulf of Mexico basin The formation of the Gulf of Mexico, an oceanic rift basin located between North America and the Yucatan Block, was preceded by the breakup of the Supercontinent Pangaea in the Late-Triassic, weakening the lithosphere. Rifting between the North ...

system bounding Florida.

Location

The Choctaw Sea was named for the Choctaw or

Choctawhatchee River The Choctawhatchee River is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National Map , accessed 15 April 2011 river in the southern United States, flowing through southeast Alabama and the Panhandle o ...

of northern

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

. It occupied most of the

Florida Panhandle The Florida panhandle (also known as West Florida and Northwest Florida) is the northwestern part of the U.S. state of Florida. It is a Salient (geography), salient roughly long, bordered by Alabama on the west and north, Georgia (U.S. state ...

including the river deltas of the

Apalachicola River The Apalachicola River is a river, approximately long, in the state of Florida. The river's large drainage basin, watershed, known as the ACF River Basin, Apalachicola, Chattahoochee and Flint (ACF) River Basin, drains an area of approximately ...

, and

Ochlockonee River The Ochlockonee River ( ) is a fast running river, except where it has been dammed to form Lake Talquin in Florida, originating in Georgia and flowing for before terminating in Florida. Background The name is from the Hitchiti language wor ...

. At its maximum coverage it encompassed an area as far north as the city of

Bainbridge Bainbridge may refer to: People *Bainbridge (name) Places * Bainbridge Township (disambiguation) United States * Bainbridge Island, Alaska * Bainbridge, Georgia * Bainbridge, Indiana * Bainbridge (town), New York ** Bainbridge (village), New Yo ...

Southwest Georgia Southwest Georgia is a fourteen-county region in the U.S. state of Georgia, bordering Alabama and Florida. Colloquially referred to as SOWEGA, the region is anchored by Albany—its most populous city and the region's sole metropolitan statistica ...

and as far to the southeast as

Taylor County, Florida Taylor County is a county located in the Big Bend region in the northern part of the U.S. state of Florida. As of the 2020 census, the population was 21,796. Its county seat is Perry. The county hosts the annual Florida Forest Festival and ...

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

The Choctaw Sea was divided further into two groups of three sub-seas based upon marine fauna. These sub-seas were named: *Bainbridge Subsea *Chattahoochie Subsea *Chipola Subsea *Walton Subsea *Alaqua Subsea *Jackson Subsea

Subseas

Bainbridge Subsea

Period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

. * Geologic stage:

Rupelian The Rupelian is, in the geologic timescale, the older of two age (geology), ages or the lower of two stage (stratigraphy), stages of the Oligocene epoch (geology), Epoch/series (stratigraphy), Series. It spans the time between . It is preceded b ...

through early

Chattian The Chattian is, in the geologic timescale, the younger of two ages or upper of two stages of the Oligocene Epoch/Series. It spans the time between . The Chattian is preceded by the Rupelian and is followed by the Aquitanian (the lowest stage ...

. ~33.9—28.4 Ma (beginning approximately ). * Animal age:

Orellan The Orellan is a North American Land Mammal Age typically set from around 33,700,000 to 32,000,000 years BP, a period of . The Orellan is preceded by the Chadronian and followed by the Whitneyan NALMA stages. Relative to global geological chronolo ...

through

Geringian The Geringian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 30,800,000 to 26,300,000 years BP, a period of . It is usuall ...

. ~33.9—26.3 Ma. *Post-Bainbridge dry period: Chattian ~28.4—23.03 Ma. Florida Early Miocene

The Bainbridge Subsea was named for the fossil beds of

Bainbridge, Georgia Bainbridge is a city in Decatur County, Georgia, United States. The city is the county seat of Decatur County. As of the 2020 census, the city had a population of 14,468, up from 12,697 at the 2010 census. It is the principal city of the ...

and is the oldest subsea. This period spanned the existence of the

Gulf Trough The Gulf Trough, also known as the Suwanee Straits, is an ancient geologic feature of Florida present during the Paleogene period. A strong marine current, similar to the Gulf Stream, scoured the trough from southwest to northeast. History During ...

between Georgia and Florida's

Orange Island Orange Island was a rock band based out of the town Clinton, Massachusetts. Orange Island formed in 1996 when cousins Charles Young and Brendan Dickhaut started writing music together and had David Chouinard playing bass guitar. After writing song ...

. It was a warm but cooling climate, moving towards an ice age. The

Suwannee Limestone The Suwannee Limestone is an Early Oligocene geologic formation of exposed limestones in North Florida, United States. Description Suwannee Limestone is found in the peninsula carbonate outcroppings on the northwestern, northeastern and southw ...

was established during this time. ''

Basilosaurus cetoides ''Basilosaurus'' (meaning "king lizard") is a genus of large, predatory, prehistoric archaeocete whale from the late Eocene, approximately 41.3 to 33.9 million years ago (mya). First described in 1834, it was the first archaeocete and prehistor ...

'' and ''

Zygorhiza ''Zygorhiza'' ("Yoke-Root") is an extinct genus of basilosaurid early whale known from the Late Eocene (Priabonian, 38–34 Ma) of Louisiana, Alabama, and Mississippi, United States, and the Bartonian (43–37 Ma on the New Zealand geologic tim ...

'', early toothed whales, as well as ''

Protosiren ''Protosiren'' is an extinct early genus of the order Sirenia. ''Protosiren'' existed throughout the Lutetian to Priabonian stages of the Middle Eocene. Fossils have been found in the far-flung locations like the United States (South Carolina, N ...

'', an extinct ancestor of the

Manatee Manatees (, family (biology), family Trichechidae, genus ''Trichechus'') are large, fully aquatic, mostly herbivory, herbivorous marine mammals sometimes known as sea cows. There are three accepted living species of Trichechidae, representing t ...

, inhabit these waters and are the earliest mammal fossils uncovered with specimens from

Citrus County Citrus County is a county located on the northwest central coast of the U.S. state of Florida. As of the 2020 census, the population was 153,843. Its county seat is Inverness, and its largest community is Homosassa Springs. Citrus County com ...

in dolomite ~40—37 Ma. and

Marion County, Florida Marion County is a county located in the North Central region of the U.S. state of Florida. As of the 2020 United States census, the population was 375,908. Its county seat is Ocala. Marion County comprises the Ocala, Florida Metropolitan S ...

dating from 37.2—33.9 Ma.

Chattahoochee Subsea

*Period:

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

. *Geologic stage: Late

through early

Aquitanian Aquitanian may refer to: *Aquitanian (stage), a geological age, the first stage of the Miocene Epoch *Aquitanian language, an ancient language spoken in the region later known as Gascony *Aquitani (or Aquitanians), were a people living in what is n ...

~28.4—23.03 Ma., approximately . *Animal age:

Arikareean The Arikareean North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 30,600,000 to 20,800,000 years BP, a period of . It is usuall ...

. ~30.8—20.6 Ma. *Post-Chattahoochee dry period: Late Aquitanian through early Burdigian ~23.0—20.5 Ma. Chipola Subsea Florida Burdigalian-Langhian

The Chattahoochee Subsea was named for the Chattahoochee Formation which formed during the rise in sea level. The Chattahoochie Subsea was much smaller in size than the Bainbridge and during the filling of the Chattahoochee, the

St. Marks Formation The St. Marks Formation is a Miocene geologic formation in the eastern Florida Panhandle. Age Period (geology), Period: Neogene Epoch (geology), Epoch: Miocene ~23.03 to 5.33 Mya (unit), mya, calculates to a period of Faunal stage: Arikareean th ...

of limestone and sand was established. The Gulf Trough closed between Georgia and Florida forming the complete Florida

peninsula A peninsula is a landform that extends from a mainland and is only connected to land on one side. Peninsulas exist on each continent. The largest peninsula in the world is the Arabian Peninsula. Etymology The word ''peninsula'' derives , . T ...

allowing land animals to move southward. The fossil record shows that land animals entered the newly formed peninsula ~24.8 Ma.

Chipola Subsea

*Period: Miocene. *Stage: Early

Burdigalian The Burdigalian is, in the geologic timescale, an age (geology), age or stage (stratigraphy), stage in the early Miocene. It spans the time between 20.43 ± 0.05 annum, Ma and 15.97 ± 0.05 Ma (million years ago). Preceded by the Aquitanian (sta ...

through the late

Langhian The Langhian is, in the ICS geologic timescale, an age or stage in the middle Miocene Epoch/Series. It spans the time between 15.97 ± 0.05 Ma and 13.65 ± 0.05 Ma (million years ago) during the Middle Miocene.GeoWhen (2007) The Langhian was ...

~20.43—15.97 Ma., approximately . *Animal age:

Hemingfordian The Hemingfordian on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 20,600,000 to 16,300,000 years BP. It is usually considered to overlap the lates ...

through

Barstovian The Barstovian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 16,300,000 to 13,600,000 years BP, a period of . It is usua ...

~20.3—13.6 Ma. *Post-Chipola dry period: Early

Serravallian The Serravallian is, in the geologic timescale, an List of time periods, age or a stage (stratigraphy), stage in the middle Miocene epoch (geology), Epoch/series (stratigraphy), Series, which spans the time between 13.82 annum, Ma and 11.63 Ma (m ...

~13.65—12.0 Ma. The Chipola Subsea was named after the

Chipola Formation The Chipola Formation is a Late Oligocene to Early Miocene geologic formation in the Florida Panhandle and member of the Alum Bluff Group. Age Period: Neogene Epoch: Early Miocene to Middle Miocene Faunal stage: Aqitanian ~18.9 to 18.3 mya, cal ...

and was formerly known as the Chipola Sea. It was created by rising sea level flooding the area once again. The Torreya Formation, a geologic formation extending from Gadsden to Hamilton County was established during this period. A somewhat narrow land bridge exists with a width from Madison County to

Duval County, Florida Duval County ( ), officially the City of Jacksonville and Duval County, is a County (United States), county in the First Coast, northeastern part of the U.S. state of Florida. As of the 2020 United States census, 2020 census, its population was ...

extending into Georgia. The

Middle Miocene Disruption The Middle Miocene Climatic Transition (MMCT) was a relatively steady period of climatic cooling that occurred around the middle of the Miocene, roughly 14 million years ago (Ma), during the Langhian stage, and resulted in the growth of ice sheet ...

, an extinction of many mammal

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

begins. A very short dry period follows the Chipola lasting possibly 1 million years. During the time the Middle Miocene Disruption continues. Forests slowly draw in massive amounts of

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

, gradually lowering the level of atmospheric from 650 ppmv down to around 100 ppmv.

Walton Subsea

*Period: Miocene. *Geologic stage: Early Serravallian through early

Tortonian The Tortonian is in the geologic time scale an age or stage of the late Miocene that spans the time between 11.608 ± 0.005 Ma and 7.246 ± 0.005 Ma (million years ago). It follows the Serravallian and is followed by the Messinian. The Tort ...

~12.00—7.2 Ma., approximately . *Animal age:

Clarendonian The Clarendonian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 13,600,000 to 9,000,000 years BP, a period of . It is us ...

~13.6—10.3 Ma through

Hemphillian The Hemphillian North American Stage on the geologic timescale is a North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 10,300,000 to 4,900,000 years BP. It is usually considered t ...

~10.3—4.9 Ma. *Post-Walton dry period: Early Tortonian ~10.0—9.0 Ma. The Walton Subsea was named for the fossil beds of Walton County.

Alaqua Subsea

*Period: Miocene. *Geologic time period: Mid Tortonian through mid

Messinian The Messinian is in the geologic timescale the last age or uppermost stage of the Miocene. It spans the time between 7.246 ± 0.005 Ma and 5.333 ± 0.005 Ma (million years ago). It follows the Tortonian and is followed by the Zanclean, the fir ...

~7.246—5.332 Ma., approximately . *Animal age:

~10.3—4.9 Ma. Jackson Subsea Florida Pliocene-Pleistocene

*Post-Alaqua dry period: The late Messinian through

Zanclean The Zanclean is the lowest stage or earliest age on the geologic time scale of the Pliocene. It spans the time between 5.332 ± 0.005 Ma (million years ago) and 3.6 ± 0.005 Ma. It is preceded by the Messinian Age of the Miocene Epoch, and f ...

~5.332—3.6 Ma. The Alaqua Subsea was named for the fossil beds found along Alaqua Creek, Walton County. The period of time after the Alaqua experienced a somewhat long dry period. A major event was the

Messinian salinity crisis In the Messinian salinity crisis (also referred to as the Messinian event, and in its latest stage as the Lago Mare event) the Mediterranean Sea went into a cycle of partial or nearly complete desiccation (drying-up) throughout the latter part of ...

or dry Mediterranean. It was replenished with the

Zanclean flood The Zanclean flood or Zanclean deluge is theorized to have refilled the Mediterranean Sea 5.33 million years ago. This flooding ended the Messinian salinity crisis and reconnected the Mediterranean Sea to the Atlantic Ocean, although it i ...

which raised the world-wide sea level 10 meters or 33 feet.When the Mediterranean dried up.

Jackson Subsea

*Period:

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

. *Geologic time period:

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 2.58 Ma (million years ago). T ...

through

Blancan The Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 4,750,000 to 1,806,000 years BP, a period of .Blancan The Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 4,750,000 to 1,806,000 years BP, a period of .Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

~2.588 Ma. —present. The

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

is in a full ice age with its final retreat around 11,000 years ago. The Jackson Subsea was named after the Jackson Bluff Formation and formerly called the "Jackson Sea." It was created during the rise in sea level during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Wisconsin ice age begins.

References

* Petuch, Edward J., Cenozoic Seas: The View from Eastern North America, Taylor & Francis Group, 2003, , {{ISBN, 978-0-8493-1632-6 Geology of Florida Natural history of Florida