Leon County Pleistocene coastal terraces and shorelines were the geologic result of warming and cooling periods in what is now

Leon County, Florida Leon County () is a County (United States), county in the Florida Panhandle, Panhandle of the U.S. state of Florida. It was named after the Spanish explorer Juan Ponce de León. As of the 2020 United States census, 2020 census, the population w ...

during the

Pleistocene epoch 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 ...

Overview

Repeated growth and retreat of the North American glacial sheet resulted in fluctuations of sea level over several thousand years. Florida submerged and emerged several times leaving behind established terraces assigned by mineral deposits and maximum sea level relative to the current

mean sea level A mean is a quantity representing the "center" of a collection of numbers and is intermediate to the extreme values of the set of numbers. There are several kinds of means (or "measures of central tendency") in mathematics, especially in statist ...

. These

marine terrace A raised beach, coastal terrace,Pinter, N (2010): 'Coastal Terraces, Sealevel, and Active Tectonics' (educational exercise), from 2/04/2011or perched coastline is a relatively flat, horizontal or gently inclined surface of marine origin,Pir ...

s and shorelines were named by various geologists, verified and mapped by the

USGS The United States Geological Survey (USGS), founded as the Geological Survey, is an government agency, agency of the United States Department of the Interior, U.S. Department of the Interior whose work spans the disciplines of biology, geograp ...

. Each glacial retreat caused sea level to rise less than the previous warming event, giving an extremely accurate depiction of the appearance of Florida. Leon County was studied in detail by C. W. Hendry and C. Sproul in 1966.

Hazelhurst

The Hazelhurst terrace and shoreline (formerly the Brandywine) was assigned by C. W. Cooke and includes Vernon's Coastwise delta plain and MacNeil's high

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Gadsden in particular had a very large land mass not only created by rising and lowering sea levels, but from depositions from 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 ...

on Gadsden's west side. Leon County remained completely submerged.

Coharie

The Coharie terrace and shoreline was applied by C. W. Cook in 1931 and was named for the

Great Coharie Creek Great may refer to: Descriptions or measurements * Great, a relative measurement in physical space, see Size * Greatness, being divine, majestic, superior, majestic, or transcendent People * List of people known as "the Great" * Artel Great (bo ...

, a tributary of the Black River in

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

. It is associated with a Pre-Illinoian interglacial and was the third rise in sea level during the Early Pleistocene glacial retreat and left behind dry land in the form of six distinct islands. The Coharie is defined by sediments at above current mean sea level. In Florida the Coharie is included with the Sunderland terrace in USGS mapping. Okefenokee Leon County Florida

One ancient island appeared in the extreme northwest portion of the county near the junction of Meridian Road and County Road 12. The second island was located in the general vicinity of U.S. 319 and Sunnyhill Road just south of the Florida/

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

border. The third of the northern islands of the Coharie was located in extreme northeast portion of the county and overlapping the county line between Leon and Jefferson County. To the south lay 3 more islands. The first was located generally north and near

Elinor Klapp-Phipps Park Elinor Klapp-Phipps Park is an open natural park located in northern Tallahassee, Florida, United States and operated by the City Of Tallahassee. The property is owned by Northwest Florida Water Management District. History The land was original ...

and surrounding area. The second and largest covered the area where most of

Tallahassee Tallahassee ( ) is the capital city of the U.S. state of Florida. It is the county seat of and the only incorporated municipality in Leon County. Tallahassee became the capital of Florida, then the Florida Territory, in 1824. In 2024, the est ...

is today. It extended from near

Interstate 10 Interstate 10 (I-10) is the southernmost transcontinental highway in the Interstate Highway System of the United States. It is the fourth-longest Interstate in the country at , following I-90, I-80, and I-40. It was part of the origina ...

in the north to the capitol complex in the south, to just east of State Road 263. The third island was to the west and encompassed an area near Arvah Branch including I-10, U.S. 90, and north to Miccosukee Road.

Okefenokee

The Okefenokee terrace and shoreline was assigned by MacNeil in 1950 and named after

Okefenokee Swamp The Okefenokee Swamp is a shallow, 438,000-acre (177,000 ha), peat-filled wetland straddling the Georgia (U.S. state), Georgia–Florida line in the United States. A majority of the swamp is protected by the Okefenokee National Wildlife Ref ...

. It includes deposits of the Sunderland terrace assigned by Cooke. It is associated with a

Pre-Illinoian The Pre-Illinoian Stage is used by Quaternary geologists for the early and middle Pleistocene glacial and interglacial periods of geologic time in North America from ~2.5–0.2 Ma (million years ago). North America As the oldest stage in ...

interglacial (Yarmouthian) and was the third rise in sea level during the Early Pleistocene glacial retreat. The Okefenokee is defined by sediments at above current mean sea level. The dry land mass left behind can best be described as an oddly shaped

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 ...

overlaying the islands of the Coharie as well as added land that is connected to adjacent peninsulas in other counties. Wicomico Leon County Florida

During the forming of the Okefenokee, the

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 ...

began to take shape as did rivers in other counties in Florida. The large inlet in the northeastern part of the county left the land capable of supporting a more recognizable

Lake Iamonia Lake Iamonia is a large, subtropical prairie lake in northern Leon County, Florida, United States, created during the Pleistocene epoch. History Forming Iamonia Lake Iamonia's base was established during the Early Pleistocene through submergen ...

. Eastern Leon had a large inlet reaching as far as the northeastern portion of the county. The

Cody Scarp The Cody Scarp or Cody Escarpment is located in north and north central Florida United States. It is a relict scarp and ancient persistent topographical feature formed from an ancient early Pleistocene shorelines of ~1.8 million to 10,000 years ...

is the remnant of the Okefenokee. What would become

Lake Lafayette Lake Lafayette is a Prairie Lake, prairie lake located in the coastal lowland in eastern Tallahassee, Leon County, Florida with U.S. Route 27 in Florida, US 27 / State Road 20 (Florida), State Road 20 running close on its south side. History P ...

is a Pleistocene river delta with the lake's eastern section accessing the sea.

Wicomico

The Wicomico terrace and shoreline was assigned by Cooke and is named for the Wicomico River in

St. Mary's County, Maryland St. Mary's County, established in 1637, is a county located in the U.S. state of Maryland. As of the 2020 census, the population was 113,777. Its county seat is Leonardtown. The name is in honor of Mary, the mother of Jesus. St. Mary's Count ...

and

Charles County, Maryland Charles County is a county located in the U.S. state of Maryland. As of the 2020 United States census, the population was 166,617. The county seat is La Plata. The county was named for Charles Calvert (1637–1715), third Baron Baltimore. T ...

. The Wicomico is associated with the

Sangamonian Stage The Sangamonian Stage (or Sangamon interglacial) is the term used in North America to designate the Last Interglacial (130,000-115,000 years ago) and depending on definition, part of the early Last Glacial Period, corresponding to Marine Isotope S ...

between 75,000 and 125,000 years ago. and was the fourth rise in sea level during the Early Pleistocene glacial retreat. The Wicomico is defined by sediments located at above current mean sea level. The Wicomico is well developed in northeastern and extreme northwestern Florida. At this time the county is mostly dry except for the southern coastline. The

is a shoreline of the Wicomico as well as the aforementioned Okefenokee. The Ocklochonee River empties into a large, wide estuary or inlet leading to the sea. The ground for what will be the Tallahassee Regional Airport remains underwater.

Penholoway

The Penholoway terrace and shoreline was assigned by Cooke and named after Penholoway Creek in

Wayne County, Georgia Wayne County is a county located in the southeastern part of the U.S. state of Georgia. As of the 2020 census, the population was 30,144. The county seat is Jesup. Wayne County comprises the Jesup, Georgia micropolitan statistical area. ...

and is associated with the Sangamonian Stage. The Penholoway is defined by sediments located at above current mean sea level. The seaward boundary is generally better defined than the landward boundary. In Leon County, the Penholoway is a reduction of the Wicomico.Volusuia County, Florida Natural History

Talbot

The Talbot terrace and shoreline was assigned by Cooke and named for

Talbot County, Maryland Talbot County is a county located in the U.S. state of Maryland. As of the 2020 census, the population was 37,526. Its county seat is Easton. The county was named for Lady Grace Talbot, the wife of Sir Robert Talbot, an Anglo- Irish statesma ...

. The Talbot is associated with the Sangamonian Stage. The Talbot is defined by sediments located at above current mean sea level. In Leon County the Talbot existed along the Leon/

Wakulla County Wakulla County is a county located in the Big Bend region in the northern portion of the U.S. state of Florida. As of the 2020 census, the population was 33,764. Its county seat is Crawfordville. Wakulla County is part of the Tallahassee, Flo ...

line. The Talbot is not well developed in Florida as it is in Maryland and other states. However, within Florida, the Talbot is better developed in Leon as well as Bay County, Wakulla, and Walton County.

References

{{reflist
USGS Terrace and shoreline map of Florida.
Natural history of Florida Pleistocene Geography of Leon County, Florida