Peace River Formation (Florida)
Encyclopedia
The Peace River Formation is a Late Oligocene to Early Miocene
geologic formation
in the west-central Florida
peninsula.
Epoch
: Miocene
to Pliocene
Faunal stage
: Arikareean
through Hemphillian
~23.03—4.9 mya, calculates to a period of
from Hillsborough County
to Charlotte County
on the southern part of the Ocala Platform
. extending into the Okeechobee Basin. It is widespread in Florida and part of the intermediate confining aquifer
system.
s, clay
s and carbonate
s which are interbedded. The sands are light gray to olive gray and poorly consolidated. They are clay-like with some dolostone
with a very fine to medium grained phosphate
component. Carbonates are usually light gray to yellowish dolostone found in outcrop
pings. The dolostones are soft to hard with variably sandy, clay-like, phosphate components with opaline
chert
often found. The phosphate content is enough to warrant mining.
Three sequences of sediment deposition were defined in 1998. Five lithofacies
were identified in 2000 (upper part of the formation).
in Hillsborough, Polk County
, and Hardee County
. (Webb & Crissinger). It is consistently clastic with sand-sized grains and larger grains of phosphate
in a mixture of quartz sand, silt
and clay
. The consolidation is poor and colors range from white, light brown and yellowish gray to olive gray and blue green.
Early Miocene
The Early Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Aquitanian and Burdigalian stages....
geologic formation
Geologic formation
A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...
in the west-central 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...
peninsula.
Age
Period: NeogeneNeogene
The Neogene is a geologic period and system in the International Commission on Stratigraphy Geologic Timescale starting 23.03 ± 0.05 million years ago and ending 2.588 million years ago...
Epoch
Epoch (geology)
An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...
: Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
to Pliocene
Pliocene
The 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...
Faunal stage
Faunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
: Arikareean
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 , 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...
through Hemphillian
Hemphillian
The 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...
~23.03—4.9 mya, calculates to a period of
Location
The Peace River Formation appears as an outcropping or is beneath a thin overburdenOverburden
Overburden is the material that lies above an area of economic or scientific interest in mining and archaeology; most commonly the rock, soil, and ecosystem that lies above a coal seam or ore body. It is also known as 'waste' or 'spoil'...
from Hillsborough County
Hillsborough County, Florida
As of the census of 2000, there were 998,948 people, 391,357 households, and 255,164 families residing in the county. The population density was 951 people per square mile . There were 425,962 housing units at an average density of 405 per square mile...
to Charlotte County
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...
on the southern part of the Ocala Platform
Ocala Platform
The Ocala Platform or Ocala Uplift is a geologic formation, a structural high, and a northwest-trending uplift paralleling the Peninsular Arch along the west coast.-Age:Period: NeogeneEpoch: Early Late Oligocene through Pliocene...
. extending into the Okeechobee Basin. It is widespread in Florida and part of the intermediate confining aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
system.
Lithography
The formation is composed of sandSand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
s, clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
s and carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
s which are interbedded. The sands are light gray to olive gray and poorly consolidated. They are clay-like with some dolostone
Dolostone
Dolostone or dolomite rock is a sedimentary carbonate rock that contains a high percentage of the mineral dolomite. In old U.S.G.S. publications it was referred to as magnesian limestone. Most dolostone formed as a magnesium replacement of limestone or lime mud prior to lithification. It is...
with a very fine to medium grained phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
component. Carbonates are usually light gray to yellowish dolostone found in outcrop
Outcrop
An outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. -Features:Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial deposits are covered by a mantle of soil and vegetation and cannot be...
pings. The dolostones are soft to hard with variably sandy, clay-like, phosphate components with opaline
Opaline
The opalines are a small group of peculiar protists, currently assigned to the family Opalinidae, in the order Slopalinida. Their name is derived from the opalescent appearance of these microscopic organisms when illuminated with full sunlight...
chert
Chert
Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...
often found. The phosphate content is enough to warrant mining.
Three sequences of sediment deposition were defined in 1998. Five lithofacies
Lithofacies
Lithofacies may refer to:* A mappable subdivision of a designated stratigraphic unit, distinguished from adjacent subdivisions on the basis of lithology; a facies characterized by particular lithologic features....
were identified in 2000 (upper part of the formation).
- Diatomaceous mudstoneMudstoneMudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
. - TerrigenousTerrigenousIn oceanography, terrigenous sediments are those derived from the erosion of rocks on land; that is, that are derived from terrestrial environments. Consisting of sand, mud, and silt carried to sea by rivers, their composition is usually related to their source rocks; deposition of these sediments...
mudstone. - Clay-rich quartz sand.
- Quartz sand.
- Pelecypod-rich quartz sand or sandstoneSandstoneSandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
.
Fossils
- Mollusks occur as reworked casts, molds, and limited original shell material.
- Silicified coralCoralCorals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
s - VertebrateVertebrateVertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s - WoodWoodWood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
Members
The Bone Valley Member is a subunit of the Peace River Formation (originally the Bone Valley Formation) and occurs in a limited area on the southern part of the Ocala PlatformOcala Platform
The Ocala Platform or Ocala Uplift is a geologic formation, a structural high, and a northwest-trending uplift paralleling the Peninsular Arch along the west coast.-Age:Period: NeogeneEpoch: Early Late Oligocene through Pliocene...
in Hillsborough, Polk County
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 Hardee County
Hardee County, Florida
Hardee County is a county located in the U.S. state of Florida. As of 2000, the population was 26,938. The U.S. Census Bureau 2005 estimate for the county is 28,286 . Its county seat is Wauchula, Florida. The county comprises the Wauchula, Florida, Micropolitan Statistical Area.- History :It...
. (Webb & Crissinger). It is consistently clastic with sand-sized grains and larger grains of phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
in a mixture of quartz sand, silt
Silt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
and clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
. The consolidation is poor and colors range from white, light brown and yellowish gray to olive gray and blue green.
See also
- Hardee County, Florida paleontological sites
- Hillsborough County, Florida paleontological sites
- Charlotte County, Florida paleontological sites
- Polk County, Florida paleontological sitesPolk County, Florida paleontological sitesThe Polk County paleontological sites are assemblages of Early Miocene to Late Pleistocene vertebrates occurring in Polk County, Florida, United States.-Age:Era: Neogene...
Further reading
- Berkenkotter, Richard D, Application of statistical analysis in evaluating bedded deposits of variable thickness—Florida phosphate data (United States. Bureau of Mines. Report of investigations, U.S. Dept. of the Interior, Bureau of Mines (1964)