St. Marks Formation
Encyclopedia
The St. Marks Formation is a Miocene
geologic formation
in the eastern Florida Panhandle
.
Epoch
: Miocene
~23.03 to 5.33 mya, calculates to a period of
Faunal stage
: Arikareean
through Hemphillian
, southern Leon
and southern Jefferson County, Florida
on the northwestern flank of the Ocala Platform
and along with Suwannee Limestone
and Ocala Limestone
makes up the upper part of the Floridan Aquifer
in the eastern panhandle.
.
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...
in the eastern 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...
.
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...
~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 St. Marks Formation is exposed in WakullaWakulla County, Florida
Wakulla County is a county located in the U.S. state of Florida. As of 2000, the population was 22,863. The U.S. Census Bureau 2005 estimate for the county was 28,212 people...
, southern Leon
Leon County, Florida
Leon County is a county located in the state of Florida, named after the Spanish explorer Juan Ponce de León. At the 2010 Census, the population was 275,487. The county seat of Leon County is Tallahassee which also serves as the state capital. The county seat is home to two of Florida's major...
and southern Jefferson County, Florida
Jefferson County, Florida
Jefferson County is a county located in the U.S. state of Florida. As of 2000, the population is 12,902. The U.S. Census Bureau 2005 estimate for the county is 14,490 . Its county seat is Monticello, Florida....
on the northwestern 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...
and along with Suwannee Limestone
Suwannee Limestone
The Suwanee Limestone is an Early Oligocene geologic formation of exposed limestones in North Florida, United States.-Age:Period: PaleogeneEpoch: Early Oligocene...
and Ocala Limestone
Ocala Limestone
The Ocala Limestone is a late Eocene geologic formation of exposed limestones near Ocala, Marion County, Florida.-Age:Period: PaleogeneEpoch: Late EoceneFaunal stage: Late Clarkforkian through early Orellan...
makes up the upper part of the Floridan Aquifer
Floridan Aquifer
The Floridan Aquifer is a portion of the principal artesian aquifer that extends into Florida and is composed of carbonate rock and located beneath the coastal regions of the Southeastern United States and is one of the world's most productive aquifers. It is under all of Florida as well as ...
in the eastern panhandle.
Composition
The St. Marks Formation consists of a white to yellowish gray, poorly to moderately hard, sandy, fossil bearing rock in molds and casts within packstone to wackestoneWackestone
Wackestone is a matrix-supported carbonate rock that contains over 10% allochems in a carbonate mud matrix. This is part of the Dunham classification of carbonate rocks. In the other widely used classification due to Folk, an equivalent description would be, for example, an oopelmicrite, where the...
.