Okeechobean Sea
Encyclopedia
The Okeechobean Sea was a Cenozoic
eutropical subsea
, which along with the Choctaw Sea
, occupied the eastern Gulf of Mexico
basin system bounding Florida.
of southern Early Oligocene Florida
. It occupied southern Florida from what is now Tampa, Florida
to the Kissimmee River
and to Martin County
on the east and southward across the Everglades
to the tip of Florida. The Okeechobean (including its subseas) survived until the Pleistocene
making it the longest-lived paleosea in eastern North America.
The Okeechobean Sea was divided further in to two groups of a combined 10 subsea
s based upon marine fauna. These subseas were named:
The Dade Subsea was named for Dade County, Florida fossil reefs and is contemporary with the Bainbridge Subsea of North Florida. It is the last platform created from carbonate deposits and the predecessor of the recent Florida peninsula. It was formed out of the meteor
impacts and tsunami
s of the colder Eocene
. By the mid Rupelian, the global climate warms and Florida consists of just Orange Island
, a somewhat long island with coral reef
s extending as far north as Alabama and Georgia forming the Salt Mountain formation and Flint River Formation respectively. Along its west coast lay the Pasco Reef System. separated from the mainland by the Gulf Trough
or Suwannee Strait also with coral reefs. Orange Island lay just 150 km (93.2 mi) from Georgia. Two deep carbonate features will eventually become the substructure of the Everglades
.
Basilosaurus cetoides
and Zygorhiza
, early toothed whales, as well as Protosiren
, an extinct ancestor of the Manatee
, inhabit these waters and are the earliest mammal fossils uncovered with specimens from Citrus County
in dolomite
dating to ~40—37 Ma. and Marion County, Florida
dating from 37.2—33.9 Ma.
The Tampa Subsea was named for the Tampa, Florida
and reef system. It is contemporary with the Chattahoochee Subsea in the Florida Panhandle
. During this period, Orange Island grew in size toward the west and north while the Gulf Trough or Suwannee Strait narrowed and became shallower. On Orange Island's western side, upwelling
systems were taking place with a system of lagoons and coral islands not unlike the Florida Keys
evolving. In what would become the Everglades, the carbonate banks grew and the area became shallower.
The Gulf Trough closed between Georgia and Florida forming the complete peninsula allowing southward movement of Florida's first land mammals such as the early canids Enhydrocyon
, Osbornodon
, and Phlaocyon
preying upon the proto-horse Miohippus
, deer-like Hypertragulidae
, and the extinct camel, Nothokemas
. The fossil record shows that land animals entered the newly formed peninsula with the earliest land mammals unearthed in Hernando, County
dating from ~24.8 Ma.
The Arcadia Subsea was named after the Arcadia Formation
and is contemporary with the Chipola Subsea to the north in the panhandle. During this period, the Florida peninsula
forms as the Gulf Trough closes in the north and fills with mangrove forests. South of what was Orange Island and is now the peninsula's tip, was a deep water lagoon with many banks made of oyster bars and coral reefs. The largest bank was located on its southwest. Also by this time, phytoplankton
blooms along the western coast poured in to the Arcadia Subsea. The Middle Miocene Climatic Optimum of ~16 Ma. carbon dioxide
and a climate change increases, warming the planet. The Middle Miocene disruption
, an extinction of many mammal genera
begins.
The Arcadia begins to regress with a very short dry period lasting possibly 1 million years. During this time the Middle Miocene Disruption continues. Forests slowly draw in massive amounts of carbon dioxide
, gradually lowering the level of atmospheric CO2 to approximately 100 ppmv.
Metaxytherium floridanum
a form of manatee
, and Long beaked dolphin (Pomatodelphis) swam this subsea.
The fossil of Mesoplodon longirostris is found on the Miami Terrace dating to ~15.97—11.61 Ma.
The Polk Subsea was named for the rich fossil beds of Polk County, Florida
and contemporary with the Walton Subsea. During this rather short period of time of 400,000 years, the peninsula's southwestern edge develops a shallow yet broad lagoon system. Near western DeSoto County
, erosion creates water-filled sinkhole
s and rivers with sediments from this erosion enhancing the carbonate bank on the southwest and producing large oyster bioherms along the seaward side of the lagoon system as well as banks to the south. The upwelling of nutrients and phytoplankton of the Arcadia Subsea continued and increased eventually flooding the lagoon system and Okeechobee Basin and contributing to the building of the Peace River Formation
.
Sperm Whale
(Kogiopsis floridana), 9.1—9.0 Ma. Fossil specimen found in the Amalgamated Phosphate Mine; Brewster Phosphate Mine, Polk County, Florida.
The Charlotte Subsea was named for the fossil beds found in Charlotte County, Florida
. A rather short-lived subsea, during this period the rivers and lakes of the DeSoto Plain
are complete and produce vast quantities of sediment deposited in the Okeechobee Basin. The banks on the western side of the Charlotte Subsea force material southward producing the DeSoto Delta. This delta filled in approximately 50% of the western Okeechobee Basin producing a platform.
Fossils of the Beaked whale, River dolphin
, and a form of toothed whale (Kentriodontidae) dating to ~7.9—7.8 Ma. are uncovered in Polk County.
The Murdock Subsea was named after Murdock Station Formation and followed the worldwide cooling and sea level lowering of the Messinian stage. This period is the last one of delta creation upwelling and one of fast erosion in Florida with sediments quite rapidly flowing in to the Everglades area creating what is known as the Immokolee Delta. The Okeechobean flooded again creating the Murdock Subsea and covering the Immokolee Delta which disbursed its sediments further south in to the glades. What remained was a long deep water feature on the eastern side of the Murdock. Upwelling with plankton blooms continued along the west coast supporting well as oysters and similar animals.
Balaenoptera floridana
and Delphinidae were found in Lee County
. and Bone Valley Formation.
The Tamiami Subsea is named after the Tamiami Formation
. This period is marked by a warming climate and one in which produced tropical conditions in Florida. Upwelling of cooler, nutrient rich water halted and the Okeechobee Basin returned to evolving through carbonate sedimentation with both Immokolee and DeSoto deltas now were covered and looking similar to the Bahama Banks
.
During the Tamiami Subsea's creation, the basin of the Everglades was encompassed by the Everglades Pseudoatoll
. This feature's north side supported mangrove jungles and estuaries extending to the mainland and Kissimmee Embayment. The east, west, and south were created by reefs and islands of over 100 species of coral which grew atop the Hawthornian oyster and barnacle
bars. The Nashua Lagoon System extends along the entire east coast of Florida.
The Caloosahatchee Subsea was named for the Caloosahatchee Formation. During this period, the Tamiami Psedoatoll feature of islands and reefs became wider and the marine environment was shallower and more of a connected lagoon system. The west and south of the Okeechobean was covered with mangrove.
During the late Calabrian, ~1.8 Ma.—780,000 years ago, temperatures plunged to that or possibly colder than the Messinian
-Zanclean
with the Caloosahatchee basin rising and filling with rock and mineral deposits. All of the paleoseas experienced mass extinction of endemic species.
The Loxahatchee Subsea was named after the Loxahatchee Formation. The Pre-Illinoian began as a general warming from the frigid late Calabrian stage yet contained several ice ages and interglacial
s of its own. During the Nebraskan glaciation, the Loxahatchee Subsea then consisted of a freshwater
lake
called Lake Immokolee filled with calcarenite charaphyte
s and siliclastic material from what would eventually be the Kissimmee River
. It was approximately four times the size of Lake Okeechobee and existed until the next interglacial.
The Okeechobean Sea experienced the last deposits of sediments allowing the Loxahatchee Subsea as well as the Kissimmee Valley and Okeechobee Plain to fill and become 50% covered with mangrove forests. This new Loxahatchee Subsea was filled with mangrove islands. The mangrove islands of southwest Florida are reduced to coastal swamps. On the eastern side of the new Loxahatchee Subsea, reefs became wide islands covered with pines and palmettos with deep water surrounding them. A lagoon was created on the east with warmer water than surrounding water creating a refuge for corals and mollusks which became extinct along the eastern U.S. coastline.
In the west, Immokolee Island had been created from banks and reefs. To the east lay Miccosukee Island south of where Lake Okeechobee is currently. The Tomeu Islands were near future western Palm Beach County
All three islands were covered with pine
and palmetto
forests. Flanking the Tomeu Islands on the west was the Capeletti Reef Tract. The southeastern and Atlantic facing part of the peninsula supported the Miami and Palm Beach Archipelagos. Connected and to the south of that and what would be the future Florida Keys
was the Monroe Reef Tract.
The Belle Glade Subsea was named after Belle Glade, Florida
and lasted ~300,000 to 75,000 years ago, a period of ~. During this time the Okeechobean Sea locality was much shallower than previous. Geologic features were greatly enlarged compared with the aforementioned Loxahatchee Subsea. Islands and mangrove
forests filled 75% of the Okeechobean basin.
The Lake Worth Subsea was named for Lake Worth Formation and lasted from ~300,000—75,000 years ago, a period of . The eastern lagoon of Okeechobean Sea had filled in with sands, quartz, and carbonates. A series of keys extended along the continental shelf
to almost Key West
. Oolite
was created behind reef sections from pounding seas originating off of Africa
due to a submerged Bahamas Bank.
The Lake Worth Subsea was the last flooding stage of this area. It regressed during the Wisconsin Ice Age
and infilled to become a shallow basin creating the Everglades
.
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...
eutropical subsea
Eutropical subsea
A Eutropical subsea is a low-latitude, circumequatorial body of water within a eutropical, that is genuinely tropical rather than sub-tropical ecozone. It is applied to marine waters considered truly tropical, in which the temperature does not drop below 20 degrees Celsius...
, which along with the Choctaw Sea
Choctaw Sea
The Choctaw Sea was a Cenozoic eutropical subsea, which along with the Okeechobean Sea, occupied the eastern Gulf of Mexico basin system bounding Florida.-Location:The Choctaw Sea was named for the Choctaw or Choctawhatchee River of northern Oligocene Florida...
, occupied the eastern Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
basin system bounding Florida.
Location
The Okeechobean Sea was a named for Lake OkeechobeeLake Okeechobee
Lake Okeechobee , locally referred to as The Lake or The Big O, is the largest freshwater lake in the state of Florida. It is the seventh largest freshwater lake in the United States and the second largest freshwater lake contained entirely within the lower 48 states...
of southern Early Oligocene Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
. It occupied southern Florida from what is now Tampa, Florida
Tampa, Florida
Tampa is a city in the U.S. state of Florida. It serves as the county seat for Hillsborough County. Tampa is located on the west coast of Florida. The population of Tampa in 2010 was 335,709....
to the Kissimmee River
Kissimmee River
The Kissimmee River is a river in south-central Florida, United States.-Course:The Kissimmee River arises in Osceola County as the outflow from East Lake Tohopekaliga, passing through Lake Tohopekaliga, Lake Cypress, Lake Hatchineha and Lake Kissimmee...
and to Martin County
Martin County, Florida
Martin County is a county in the U.S. state of Florida. As of 2000, the population was 126,731. The U.S. Census Bureau 2008 estimate for the county is 138,660. Its county seat is Stuart, Florida.- History :...
on the east and southward across the Everglades
Everglades
The Everglades are subtropical wetlands in the southern portion of the U.S. state of Florida, comprising the southern half of a large watershed. The system begins near Orlando with the Kissimmee River, which discharges into the vast but shallow Lake Okeechobee...
to the tip of Florida. The Okeechobean (including its subseas) survived until the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
making it the longest-lived paleosea in eastern North America.
The Okeechobean Sea was divided further in to two groups of a combined 10 subsea
Subsea
Subsea is a general term frequently used to refer to equipment, technology, and methods employed in marine biology, undersea geology, offshore oil and gas developments, underwater mining, and offshore wind power industries.- Oil and gas :...
s based upon marine fauna. These subseas were named:
- Dade Subsea
- Tampa Subsea
- Arcadia Subsea
- Murdock Subsea
- Tamiami Subsea
- Charlotte Subsea
- Caloosahathee Subsea
- Laxahatchee Subsea
- Lake Worth Subsea
- Belle Glade Subsea
Dade Subsea
- PeriodSeries (stratigraphy)Series are subdivisions of rock layers made based on the age of the rock and corresponding to the dating system unit called an epoch, both being formally defined international conventions of the geological timescale. A series is therefore a sequence of rock depositions defining a...
: OligoceneOligoceneThe Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
(complete). - Geologic stage: RupelianRupelianThe Rupelian is, in the geologic timescale, the older of two ages or the lower of two stages of the Oligocene epoch/series. It spans the time between and . It is preceded by the Priabonian stage and is followed by the Chattian stage....
through early ChattianChattianThe Chattian is, in the geologic timescale, the youngest of two ages or upper of two stages of the Oligocene epoch/series. It spans the time between and . The Chattian is preceded by the Rupelian and is followed by the Aquitanian .-Stratigraphic definition:The Chattian was introduced by Austrian...
. ~33.9—28.4 Ma., approximately ~. - Animal age: OrellanOrellanThe Orellan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 33,900,000 to 33,300,000 years BP, a period of . It is usually considered to fall within the Early Oligocene...
through GeringianGeringianThe Geringian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 30,800,000 to 26,300,000 years BP, a period of . It is usually considered to fall within the Oligocene epoch...
. ~33.9—26.3 Ma. - Post-Dade dry period: ~28.0—23 Ma. A moderate icehouse climate followed by an ice age lasting most of the Chattian ~28.4—23.03 Ma.
The Dade Subsea was named for Dade County, Florida fossil reefs and is contemporary with the Bainbridge Subsea of North Florida. It is the last platform created from carbonate deposits and the predecessor of the recent Florida peninsula. It was formed out of the meteor
METEOR
METEOR is a metric for the evaluation of machine translation output. The metric is based on the harmonic mean of unigram precision and recall, with recall weighted higher than precision...
impacts and tsunami
Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...
s of the colder Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
. By the mid Rupelian, the global climate warms and Florida consists of just Orange Island
Orange Island (Florida)
Orange Island is the earliest emergent landmass of Florida dating from the middle Rupelian ~33.9—28.4 Ma. geologic stage of the Early Oligocene epoch and named for Orange County, Florida, United States of America.-Location:...
, a somewhat long island with coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
s extending as far north as Alabama and Georgia forming the Salt Mountain formation and Flint River Formation respectively. Along its west coast lay the Pasco Reef System. separated from the mainland by the Gulf Trough
Gulf Trough
The Gulf Trough, also known as the Suwanee Straits, is an ancient geologic feature of Florida present during the Paleogene...
or Suwannee Strait also with coral reefs. Orange Island lay just 150 km (93.2 mi) from Georgia. Two deep carbonate features will eventually become the substructure of the Everglades
Everglades
The Everglades are subtropical wetlands in the southern portion of the U.S. state of Florida, comprising the southern half of a large watershed. The system begins near Orlando with the Kissimmee River, which discharges into the vast but shallow Lake Okeechobee...
.
Basilosaurus cetoides
Basilosaurus
Basilosaurus is a genus of cetacean that lived from in the Late Eocene. Its fossilized remains were first discovered in the southern United States . The American fossils were initially believed to be some sort of reptile, hence the suffix -"saurus", but later found to be a marine mammal...
and Zygorhiza
Zygorhiza
Zygorhiza kochii is an extinct species of cetacean.Zygorhiza was a smaller, less elongated, 6 m long relative of the famous Basilosaurus. Its bodily proportions were similar to those of modern whales, although, unlike modern species, it had a distinct neck, and flippers which could be moved at...
, early toothed whales, as well as Protosiren
Protosiren
Protosiren is an extinct early genus of the order Sirenia. Protosiren existed throughout the Lutetian and Bartonian stages of the Middle Eocene. Its geographic distribution was intercontinental: fossils have been found in the United States , Egypt, France, Hungary, India, and Pakistan...
, an extinct ancestor of the Manatee
Manatee
Manatees are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows...
, inhabit these waters and are the earliest mammal fossils uncovered with specimens from Citrus County
Citrus County, Florida
Citrus County is a county located in the U.S. state of Florida. As of 2000, the population was 118,085. The U.S. Census Bureau 2008 estimate for the county was 141,416 . Its county seat is Inverness, Florida...
in dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
dating to ~40—37 Ma. and Marion County, Florida
Marion County, Florida
Marion County is a county located in the U.S. state of Florida. The U.S. Census Bureau 2006 estimate for the county is 316,183. Its county seat is Ocala....
dating from 37.2—33.9 Ma.
Tampa Subsea
- Period: Late Oligocene—Early MioceneEarly MioceneThe Early Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Aquitanian and Burdigalian stages....
. - Geologic stage: ChattianChattianThe Chattian is, in the geologic timescale, the youngest of two ages or upper of two stages of the Oligocene epoch/series. It spans the time between and . The Chattian is preceded by the Rupelian and is followed by the Aquitanian .-Stratigraphic definition:The Chattian was introduced by Austrian...
through early Aquitanian stage of the Miocene ~28.4—23.03 Ma., approximately . - Animal age: ArikareeanArikareeanThe Arikareean North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 30,600,000 to 20,800,000 years BP, a period of . It is usually considered to overlap the Oligocene and Miocene epochs...
. ~30.8—20.6 Ma. - Post-Tampa dry period: Late Aquitanian through early Burdigian ~23.0—20.5 Ma.
The Tampa Subsea was named for the Tampa, Florida
Tampa, Florida
Tampa is a city in the U.S. state of Florida. It serves as the county seat for Hillsborough County. Tampa is located on the west coast of Florida. The population of Tampa in 2010 was 335,709....
and reef system. It is contemporary with the Chattahoochee Subsea in the Florida Panhandle
Florida Panhandle
The Florida Panhandle, an informal, unofficial term for the northwestern part of Florida, is a strip of land roughly 200 miles long and 50 to 100 miles wide , lying between Alabama on the north and the west, Georgia also on the north, and the Gulf of Mexico to the south. Its eastern boundary is...
. During this period, Orange Island grew in size toward the west and north while the Gulf Trough or Suwannee Strait narrowed and became shallower. On Orange Island's western side, upwelling
Upwelling
Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water. The increased availability in upwelling regions results in high levels of primary...
systems were taking place with a system of lagoons and coral islands not unlike the Florida Keys
Florida Keys
The Florida Keys are a coral archipelago in southeast United States. They begin at the southeastern tip of the Florida peninsula, about south of Miami, and extend in a gentle arc south-southwest and then westward to Key West, the westernmost of the inhabited islands, and on to the uninhabited Dry...
evolving. In what would become the Everglades, the carbonate banks grew and the area became shallower.
The Gulf Trough closed between Georgia and Florida forming the complete peninsula allowing southward movement of Florida's first land mammals such as the early canids Enhydrocyon
Enhydrocyon
Enhydrocyon is an extinct genus of bone crushing dog which inhabited North America exclusively during the Oligocene living from around 28.7—22.0 Ma and existed for approximately ....
, Osbornodon
Osbornodon
Osbornodon is an extinct genus of bone-crushing canid that were endemic to North America and which lived from the Orellan age of the Early Oligocene to Early Miocene epoch 33.9—15.97 Ma and existed for approximately ....
, and Phlaocyon
Phlaocyon
Phlaocyon is an extinct genus of the Borophaginae and a terrestrial canine which inhabited most of North America during the Whitneyan stage of the Early Oligocene through Late Hemingfordian stage of the Early Miocene epoch 33.3—16.3 Mya existing for approximately .-Taxonomy:Phlaocyon was about in...
preying upon the proto-horse Miohippus
Miohippus
Miohippus was a genus of prehistoric horse existing longer than most Equidae. Miohippus lived in what is now North America during the Oligocene approximately 32-25 million years ago. While descending genera of this species lived during the Miocene period, the Miohippus was a horse of the Oligocene...
, deer-like Hypertragulidae
Hypertragulidae
Hypertragulidae is an extinct family of even-toed ungulates , endemic to North America, Europe, and Asia during the Eocene through Miocene, living 46.2—13.6 Ma, existing for approximately ....
, and the extinct camel, Nothokemas
Nothokemas
Nothokemas is an extinct genus of terrestrial herbivore the family Camelidae, endemic to North America from the Oligocene through Miocene 30.8— 20.430 mya, existing for approximately .-Taxonomy:...
. The fossil record shows that land animals entered the newly formed peninsula with the earliest land mammals unearthed in Hernando, County
Hernando County, Florida
Hernando County is a county located in the U.S. state of Florida. As of 2000, the population was 130,802. The U.S. Census Bureau 2006 estimate for the county is 165,409 . Its county seat is Brooksville, Florida. The majority of the county's population is in Spring Hill, west portion of Hernando...
dating from ~24.8 Ma.
Arcadia Subsea
- Period: Miocene.
- Geologic stage: BurdigalianBurdigalianThe Burdigalian is, in the geologic timescale, an age or stage in the early Miocene. It spans the time between 20.43 ± 0.05 Ma and 15.97 ± 0.05 Ma...
through early SerravallianSerravallianThe Serravallian is in the geologic timescale an age or a stage in the middle Miocene epoch/series, that spans the time between 13.65 ± 0.05 Ma and 11.608 ± 0.005 Ma...
stages ~20.43—13.6 Ma., approximately . - Animal age: Hemingfordian through BarstovianBarstovianThe Barstovian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 16,300,000 to 13,600,000 years BP, a period of . It is usually considered to overlap the Langhian and Serravallian...
~20.3—13.6 Ma. - Post-Arcadia dry period:' Early SerravallianSerravallianThe Serravallian is in the geologic timescale an age or a stage in the middle Miocene epoch/series, that spans the time between 13.65 ± 0.05 Ma and 11.608 ± 0.005 Ma...
~13.65—12.0 Ma.
The Arcadia Subsea was named after the Arcadia Formation
Arcadia Formation
The Arcadia Formation and its sub-unit, the Tampa Member, are Late Oligocene geologic formations in North Florida, United States. It is part of the Hawthorn Group.-Age:Period: Paleogene to Neogene...
and is contemporary with the Chipola Subsea to the north in the panhandle. During this period, the Florida peninsula
Peninsula
A peninsula is a piece of land that is bordered by water on three sides but connected to mainland. In many Germanic and Celtic languages and also in Baltic, Slavic and Hungarian, peninsulas are called "half-islands"....
forms as the Gulf Trough closes in the north and fills with mangrove forests. South of what was Orange Island and is now the peninsula's tip, was a deep water lagoon with many banks made of oyster bars and coral reefs. The largest bank was located on its southwest. Also by this time, phytoplankton
Phytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...
blooms along the western coast poured in to the Arcadia Subsea. The Middle Miocene Climatic Optimum of ~16 Ma. carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
and a climate change increases, warming the planet. The Middle Miocene disruption
Middle Miocene disruption
The term Middle Miocene disruption, alternatively the Middle Miocene extinction or Middle Miocene extinction peak, refers to a wave of extinctions of terrestrial and aquatic life forms that occurred around the middle of the Miocene Epoch, c...
, an extinction of many mammal genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
begins.
The Arcadia begins to regress with a very short dry period lasting possibly 1 million years. During this time the Middle Miocene Disruption continues. Forests slowly draw in massive amounts of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
, gradually lowering the level of atmospheric CO2 to approximately 100 ppmv.
Metaxytherium floridanum
Metaxytherium
Metaxytherium is an extinct genus of dugong that lived from the Miocene to the Pleistocene. Its remains have been found in Africa, Asia, Europe, North America, and South America.- Sources :*Manatees and Dugongs of the World by Jeff Ripple...
a form of manatee
Manatee
Manatees are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows...
, and Long beaked dolphin (Pomatodelphis) swam this subsea.
The fossil of Mesoplodon longirostris is found on the Miami Terrace dating to ~15.97—11.61 Ma.
Polk Subsea
- Period: Middle Miocene.
- Geologic stage: Late Serravallian through early TortonianTortonianThe Tortonian is in the geologic timescale an age or stage of the late Miocene that spans the time between 11.608 ± 0.005 Ma and 7.246 ± 0.005 Ma . It follows the Serravallian and is followed by the Messinian....
~12.00—11.6 Ma., approximately . - Animal age: ClarendonianClarendonianThe Clarendonian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 13,600,000 to 10,300,000 years BP, a period of . It is usually considered to overlap the Serravallian of the Middle...
~13.6—10.3 Ma through HemphillianHemphillianThe Hemphillian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 10,300,000 to 4,900,000 years BP, a period of . It is usually considered to overlap the Tortonian epoch of the Late...
~10.3—4.9 Ma. - Post-Polk dry period: Early Tortonian, approximately ~11.6—9.0 Ma.
The Polk Subsea was named for the rich fossil beds of Polk County, Florida
Polk County, Florida
Polk County is located in central Florida between the Tampa Bay and Greater Orlando metropolitan areas. The county was established by the state government in 1861 on the eve of the American Civil War and named after former United States president James K. Polk. The county seat is Bartow and its...
and contemporary with the Walton Subsea. During this rather short period of time of 400,000 years, the peninsula's southwestern edge develops a shallow yet broad lagoon system. Near western DeSoto County
DeSoto County, Florida
DeSoto County is a county located in the U.S. state of Florida. As of 2000, the population was 32,209. The U.S. Census Bureau 2005 estimate for the county is 35,406 . Its county seat is Arcadia, Florida. The county comprises the Arcadia, Florida Micropolitan Statistical Area.- History :DeSoto...
, erosion creates water-filled sinkhole
Sinkhole
A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural depression or hole in the Earth's surface caused by karst processes — the chemical dissolution of carbonate rocks or suffosion processes for example in sandstone...
s and rivers with sediments from this erosion enhancing the carbonate bank on the southwest and producing large oyster bioherms along the seaward side of the lagoon system as well as banks to the south. The upwelling of nutrients and phytoplankton of the Arcadia Subsea continued and increased eventually flooding the lagoon system and Okeechobee Basin and contributing to the building of the Peace River Formation
Peace River Formation
The Peace River Formation is a stratigraphical unit of middle Albian age in the Western Canadian Sedimentary Basin.It takes the name from the Peace River, and was first described on the banks of the river, downstream from the Smoky River confluence to the mouth of the Notikewin River by McConnell...
.
Sperm Whale
Sperm Whale
The sperm whale, Physeter macrocephalus, is a marine mammal species, order Cetacea, a toothed whale having the largest brain of any animal. The name comes from the milky-white waxy substance, spermaceti, found in the animal's head. The sperm whale is the only living member of genus Physeter...
(Kogiopsis floridana), 9.1—9.0 Ma. Fossil specimen found in the Amalgamated Phosphate Mine; Brewster Phosphate Mine, Polk County, Florida.
Charlotte Subsea
- Period: Late Miocene.
- Geologic stage: Late Tortonian through early MessinianMessinianThe 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 5.332 ± 0.005 Ma...
~8.0—6.0 Ma. ± (500,000 years either side), approximately . - Animal age: HemphillianHemphillianThe Hemphillian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 10,300,000 to 4,900,000 years BP, a period of . It is usually considered to overlap the Tortonian epoch of the Late...
~10.3—4.9 Ma. - Post-Charlotte dry period: The late Messinian through ZancleanZancleanThe Zanclean is the lowest stage or earliest age on the geologic time scale of the Pliocene. It spans the time between 5.332 and 3.6 Ma ± 0.005 Ma . It is preceded by the Messinian age of the Miocene epoch, and followed by the Piacenzian age....
~5.332—3.6 Ma. experienced a somewhat long dry period. A major event was the Messinian salinity crisisMessinian salinity crisisThe Messinian Salinity Crisis, also referred to as the Messinian Event, and in its latest stage as the Lago Mare event, was a geological event during which the Mediterranean Sea went into a cycle of partly or nearly complete desiccation throughout the latter part of the Messinian age of the Miocene...
or dry Mediterranean. It was replenished with the Zanclean floodZanclean floodThe Zanclean flood is a flood theorized to have refilled the Mediterranean Sea 5.33 million years ago, at the beginning of the Zanclean age, between the Miocene and Pliocene, which ended the Messinian salinity crisis...
which raised the worldwide sea level 10 meters or 33 feet.
The Charlotte Subsea was named for the fossil beds found in Charlotte County, Florida
Charlotte County, Florida
Charlotte County is a county located in the U.S. state of Florida. As of 2000, the population was 141,627. In 2005, the population of the MSA was 154,030.The U.S. Census Bureau 2007 estimate for the county was 152,814...
. A rather short-lived subsea, during this period the rivers and lakes of the DeSoto Plain
DeSoto Plain
The DeSoto Plain is a major geologic feature of Florida formed during the Miocene epoch and named for DeSoto County, Florida, United States.The DeSoto is an old prairie or grassland at elevations of 70 to 100 feet bounded by the lower elevation Okeechobee Plain on the east...
are complete and produce vast quantities of sediment deposited in the Okeechobee Basin. The banks on the western side of the Charlotte Subsea force material southward producing the DeSoto Delta. This delta filled in approximately 50% of the western Okeechobee Basin producing a platform.
Fossils of the Beaked whale, River dolphin
Iniidae
Iniidae is a family of river dolphins containing one living and three extinct genera.-Taxonomy:The family was described by John Edward Gray in 1846.Current classifications include a single living genera, Inia, with one species and three subspecies...
, and a form of toothed whale (Kentriodontidae) dating to ~7.9—7.8 Ma. are uncovered in Polk County.
Murdock Subsea
- Period: Early to mid Pliocene.
- Geologic stage: Early ZancleanZancleanThe Zanclean is the lowest stage or earliest age on the geologic time scale of the Pliocene. It spans the time between 5.332 and 3.6 Ma ± 0.005 Ma . It is preceded by the Messinian age of the Miocene epoch, and followed by the Piacenzian age....
. ~5.332—3.6 Ma., approximately . - Animal age: Late HemphillianHemphillianThe Hemphillian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 10,300,000 to 4,900,000 years BP, a period of . It is usually considered to overlap the Tortonian epoch of the Late...
through late BlancanBlancanThe Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 4,750,000 to 1,808,000 years BP, a period of .. It is usually considered to start in the early-mid Pliocene epoch and end...
~4.9—1.8 Ma. - Post-Murdock dry period: Piacenzian through Halocene ~2.588 Ma. —present. The Northern HemisphereNorthern HemisphereThe Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...
is in a full ice age which begins to retreat around 11,000 years ago.
The Murdock Subsea was named after Murdock Station Formation and followed the worldwide cooling and sea level lowering of the Messinian stage. This period is the last one of delta creation upwelling and one of fast erosion in Florida with sediments quite rapidly flowing in to the Everglades area creating what is known as the Immokolee Delta. The Okeechobean flooded again creating the Murdock Subsea and covering the Immokolee Delta which disbursed its sediments further south in to the glades. What remained was a long deep water feature on the eastern side of the Murdock. Upwelling with plankton blooms continued along the west coast supporting well as oysters and similar animals.
Balaenoptera floridana
Balaenoptera
Balaenoptera is a genus of Balaenopteridae, the Rorqual whales, and contains eight species. The species Balaenoptera omurai was published in 2003...
and Delphinidae were found in Lee County
Lee County, Florida
Lee County is a county located in the U.S. state of Florida. Located in southwest Florida, the principal cities in the county are Fort Myers and Cape Coral...
. and Bone Valley Formation.
Tamiami Subsea
- Period: Pliocene.
- Geologic stage: Late ZancleanZancleanThe Zanclean is the lowest stage or earliest age on the geologic time scale of the Pliocene. It spans the time between 5.332 and 3.6 Ma ± 0.005 Ma . It is preceded by the Messinian age of the Miocene epoch, and followed by the Piacenzian age....
through late PiacenzianPiacenzianThe Piacenzian is in the international geologic timescale the upper stage or latest age of the Pliocene. It spans the time between 3.6 ± 0.005 Ma and 2.588 ± 0.005 Ma...
, ~3.6—2.588 Ma., approximately . - Animal age: BlancanBlancanThe Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 4,750,000 to 1,808,000 years BP, a period of .. It is usually considered to start in the early-mid Pliocene epoch and end...
- Post-Tamiami dry period: The Northern Hemisphere moves in to Wisconsin Ice AgeLast Glacial MaximumThe Last Glacial Maximum refers to a period in the Earth's climate history when ice sheets were at their maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of the last glacial period. During this time, vast ice sheets covered much of North America, northern Europe and...
.
The Tamiami Subsea is named after the Tamiami Formation
Tamiami Formation
The Tamiami Formation is a Late Miocene to Pliocene geologic formation in the southwest Florida peninsula.-Age:Period: NeogeneEpoch: Late Miocene to Pliocene...
. This period is marked by a warming climate and one in which produced tropical conditions in Florida. Upwelling of cooler, nutrient rich water halted and the Okeechobee Basin returned to evolving through carbonate sedimentation with both Immokolee and DeSoto deltas now were covered and looking similar to the Bahama Banks
Bahama Banks
The Bahama Banks are the submerged carbonate platforms that make up much of the Bahama Archipelago. The term is usually applied in referring to either the Great Bahama Bank around Andros Island, or the Little Bahama Bank of Grand Bahama Island and Great Abaco, which are the largest of the...
.
During the Tamiami Subsea's creation, the basin of the Everglades was encompassed by the Everglades Pseudoatoll
Everglades Pseudoatoll
The Everglades Pseudoatoll was a major geomorphic feature of southern Florida during the Pliocene epoch.-Origin:The Everglades Pseudoatoll began its growth during the early Eocene as a paleodepression possibly created by an asteroid impact upon the carbonate Florida Platform at the southern part...
. This feature's north side supported mangrove jungles and estuaries extending to the mainland and Kissimmee Embayment. The east, west, and south were created by reefs and islands of over 100 species of coral which grew atop the Hawthornian oyster and barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
bars. The Nashua Lagoon System extends along the entire east coast of Florida.
Caloosahatchee Subsea
- Period: PliocenePlioceneThe Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
to PleistocenePleistoceneThe Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
. - Geologic stage: Late PiacenzianPiacenzianThe Piacenzian is in the international geologic timescale the upper stage or latest age of the Pliocene. It spans the time between 3.6 ± 0.005 Ma and 2.588 ± 0.005 Ma...
~2.8 Ma. to late Calabrian ~780,000, approximately . - Animal age: BlancanBlancanThe Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 4,750,000 to 1,808,000 years BP, a period of .. It is usually considered to start in the early-mid Pliocene epoch and end...
to IrvingtonianIrvingtonianThe Irvingtonian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 1,800,000 to 300,000 years BP, a period of . It is usually considered to overlap the Lower Pleistocene and Middle...
~4.9 Ma.—240,000 years ago.
The Caloosahatchee Subsea was named for the Caloosahatchee Formation. During this period, the Tamiami Psedoatoll feature of islands and reefs became wider and the marine environment was shallower and more of a connected lagoon system. The west and south of the Okeechobean was covered with mangrove.
During the late Calabrian, ~1.8 Ma.—780,000 years ago, temperatures plunged to that or possibly colder than the Messinian
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 5.332 ± 0.005 Ma...
-Zanclean
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 and 3.6 Ma ± 0.005 Ma . It is preceded by the Messinian age of the Miocene epoch, and followed by the Piacenzian age....
with the Caloosahatchee basin rising and filling with rock and mineral deposits. All of the paleoseas experienced mass extinction of endemic species.
Loxahatchee Subsea
- Period: Pleistocene.
- Geologic stage: Pre-Illinoian ~2.427—1.816 Ma., approximately .
- Animal age: BlancanBlancanThe Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 4,750,000 to 1,808,000 years BP, a period of .. It is usually considered to start in the early-mid Pliocene epoch and end...
~4.9—1.8 Ma. - Post-Loxahatchee dry period: Pre-Illinoian ~1.8 Ma.—302,000 years ago.
The Loxahatchee Subsea was named after the Loxahatchee Formation. The Pre-Illinoian began as a general warming from the frigid late Calabrian stage yet contained several ice ages and interglacial
Interglacial
An Interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age...
s of its own. During the Nebraskan glaciation, the Loxahatchee Subsea then consisted of a freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
called Lake Immokolee filled with calcarenite charaphyte
Calcarenite
thumb|250px|The [[Pietra di Bismantova]] in central [[Italy]] is an example of calcarenite formation.Calcarenite is a type of limestone that is composed predominately, more than 50 percent, of detrital sand-size , carbonate grains...
s and siliclastic material from what would eventually be the Kissimmee River
Kissimmee River
The Kissimmee River is a river in south-central Florida, United States.-Course:The Kissimmee River arises in Osceola County as the outflow from East Lake Tohopekaliga, passing through Lake Tohopekaliga, Lake Cypress, Lake Hatchineha and Lake Kissimmee...
. It was approximately four times the size of Lake Okeechobee and existed until the next interglacial.
The Okeechobean Sea experienced the last deposits of sediments allowing the Loxahatchee Subsea as well as the Kissimmee Valley and Okeechobee Plain to fill and become 50% covered with mangrove forests. This new Loxahatchee Subsea was filled with mangrove islands. The mangrove islands of southwest Florida are reduced to coastal swamps. On the eastern side of the new Loxahatchee Subsea, reefs became wide islands covered with pines and palmettos with deep water surrounding them. A lagoon was created on the east with warmer water than surrounding water creating a refuge for corals and mollusks which became extinct along the eastern U.S. coastline.
In the west, Immokolee Island had been created from banks and reefs. To the east lay Miccosukee Island south of where Lake Okeechobee is currently. The Tomeu Islands were near future western Palm Beach County
Palm Beach County, Florida
Palm Beach County is the largest county in the state of Florida in total area, and third in population. As of 2010, the county's estimated population was 1,320,134, making it the twenty-eighth most populous in the United States...
All three islands were covered with pine
Pine
Pines are trees in the genus Pinus ,in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Etymology:...
and palmetto
Palmetto
-Botany:Members of several genera of small palms:*the genus Sabal of the Arecaceae family**Dwarf Palmetto**Sabal palmetto*Saw Palmetto, Serenoa repens*Silver saw palmetto, Acoelorraphe wrightii-Place names:United States...
forests. Flanking the Tomeu Islands on the west was the Capeletti Reef Tract. The southeastern and Atlantic facing part of the peninsula supported the Miami and Palm Beach Archipelagos. Connected and to the south of that and what would be the future Florida Keys
Florida Keys
The Florida Keys are a coral archipelago in southeast United States. They begin at the southeastern tip of the Florida peninsula, about south of Miami, and extend in a gentle arc south-southwest and then westward to Key West, the westernmost of the inhabited islands, and on to the uninhabited Dry...
was the Monroe Reef Tract.
Belle Glade Subsea
- Period: Pleistocene.
- Geologic stage: Illinoian ~300,000—75,000 years ago.
- Animal age: IrvingtonianIrvingtonianThe Irvingtonian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 1,800,000 to 300,000 years BP, a period of . It is usually considered to overlap the Lower Pleistocene and Middle...
to RancholabreanRancholabreanThe Rancholabrean North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from less than 240,000 years to 11,000 years BP, a period of . It is usually considered to overlap the Middle Pleistocene...
~1.8 Ma.—11,000 years ago. - Post-Belle Glade dry period: Illinoian glaciation. ~300,000—130,000 years ago.
The Belle Glade Subsea was named after Belle Glade, Florida
Belle Glade, Florida
Belle Glade is a city in Palm Beach County, Florida on the southeastern shore of Lake Okeechobee. The population was 14,906 at the 2000 census. According to the U.S Census estimates of 2007, the city had a population of 16,739....
and lasted ~300,000 to 75,000 years ago, a period of ~. During this time the Okeechobean Sea locality was much shallower than previous. Geologic features were greatly enlarged compared with the aforementioned Loxahatchee Subsea. Islands and mangrove
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
forests filled 75% of the Okeechobean basin.
Lake Worth Subsea
- Period: Pleistocene.
- Geologic stage: Late Sangamonian through late Illinoian ~300,000—75,000 years ago.
- Animal age: IrvingtonianIrvingtonianThe Irvingtonian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 1,800,000 to 300,000 years BP, a period of . It is usually considered to overlap the Lower Pleistocene and Middle...
to RancholabreanRancholabreanThe Rancholabrean North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from less than 240,000 years to 11,000 years BP, a period of . It is usually considered to overlap the Middle Pleistocene...
~1.8 Ma.—11,000 years ago. - Post-Lake Worth dry period: Wisconsin glaciation, ~110,000—9,700 years ago.
The Lake Worth Subsea was named for Lake Worth Formation and lasted from ~300,000—75,000 years ago, a period of . The eastern lagoon of Okeechobean Sea had filled in with sands, quartz, and carbonates. A series of keys extended along the continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
to almost Key West
Key West
Key West is an island in the Straits of Florida on the North American continent at the southernmost tip of the Florida Keys. Key West is home to the southernmost point in the Continental United States; the island is about from Cuba....
. Oolite
Oolite
Oolite is a sedimentary rock formed from ooids, spherical grains composed of concentric layers. The name derives from the Hellenic word òoion for egg. Strictly, oolites consist of ooids of diameter 0.25–2 mm; rocks composed of ooids larger than 2 mm are called pisolites...
was created behind reef sections from pounding seas originating off of Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
due to a submerged Bahamas Bank.
The Lake Worth Subsea was the last flooding stage of this area. It regressed during the Wisconsin Ice Age
Last Glacial Maximum
The Last Glacial Maximum refers to a period in the Earth's climate history when ice sheets were at their maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of the last glacial period. During this time, vast ice sheets covered much of North America, northern Europe and...
and infilled to become a shallow basin creating the Everglades
Everglades
The Everglades are subtropical wetlands in the southern portion of the U.S. state of Florida, comprising the southern half of a large watershed. The system begins near Orlando with the Kissimmee River, which discharges into the vast but shallow Lake Okeechobee...
.