The Coosawhatchie Formation is a 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...

 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...

 with an 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...

 in North Florida

North Florida

North Florida refers to the northernmost part of the U.S. state of Florida, including some counties that border the state of Georgia. It also borders the Big Bend with Madison County and Taylor County to the east and the Central Florida region to its south....

. It is within the Hawthorn Group

Hawthorn Group

The Hawthorn Group is a Late Oligocene to Pliocene grouping of several geologic formations and members in North Florida, United States.The Hawthorn Group was originally called the Waldo Formation in 1887 by L. C...

.

Age

Period: Neogene

Neogene

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...

 ~23.03 to 5.33 mya, calculates to a period of

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...

Location

The Coosawhatchie Formation is located on the eastern flank 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...

 near southern Columbia County

Columbia County, Florida

Columbia County is a county located in the U.S. state of Florida. As of 2000, the population was 56,513. The U.S. Census Bureau 2005 estimate for the county is 64,040 . Its county seat is Lake City, Florida....

 and southern 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....

. It extends south-southeast and is present in Alachua

Alachua County, Florida

Alachua County is a county located in the U.S. state of Florida. The U.S. Census Bureau 2006 estimate for the county is 227,120. Its county seat is Gainesville, Florida. Alachua County is the home of the University of Florida and is also known for its diverse culture, local music, and artisans...

, Marion

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....

, Sumter

Sumter County, Florida

Sumter County is a county located in the state of Florida, United States. As of the 2000 Census, the population was 53,345. The 2006 Census estimate puts its population at 68,768 . Its county seat is Bushnell, Florida and the largest incorporated municipality is Wildwood, Florida. The Villages,...

, and Lake County

Lake County, Florida

Lake County is a county located in the state of Florida, United States. As of the 2000 Census, the population was 210,528. The Census Bureau estimated the population in 2008 to be 307,243. Its county seat is Tavares...

. It is exposed or lies beneath a thin overburden

Overburden

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'...

.

Lithography

The Coosawhatchie Formation varies in color from a light gray to olive gray. It is poorly consolidated, variably clayey and 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...

 containing sand which occasionally contain a dolomitic component but rarely is it dominated with 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...

 or limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

.

Silicified nodules are often present in the sediments and may contain 20% or more 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...

. The permeability factor of the Coosawhatchie sediments is generally low, forming 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.

Members

Charlton Member outcrops in just one location, that being northern Nassau County, Florida

Nassau County, Florida

Nassau County is a county located in the state of Florida. As of 2000, the population was 57,663. The U.S. Census Bureau 2008 estimate for the county was 69,835. Its county seat is Fernandina Beach, Florida....

 near and along the St. Mary's River

St. Marys River (Florida/Georgia)

The St. Marys River is a river in the southeastern United States. It is named after the Irish Saint Mary. From near its source in the Okefenokee Swamp, to its mouth at the Atlantic Ocean, it forms a portion of the border between the U.S. states of Georgia and Florida...

. Here it consists primarily of light gray to greenish gray, poorly to moderately consolidated, dolostone bearing to calcareous

Calcareous

Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...

, silty, sandy, with few 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....

beds.