The Alum Bluff Group is a

geologic group In geology, a group is a lithostratigraphic unit consisting of a series of related formations that have been classified together to form a group. Formations are the fundamental unit of stratigraphy. Groups may sometimes be combined into superg ...

in the states of

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 ...

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

, and

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

. It preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

dating back to the

Neogene The Neogene ( ,) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period million years ago. It is the second period of th ...

period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

Age

Period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

Epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...

Late Oligocene The Chattian is, in the geologic timescale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...

Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...

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 conven ...

Chattian The Chattian is, in the geologic timescale, the younger of two ages or upper of two stages of the Oligocene Epoch/Series. It spans the time between . The Chattian is preceded by the Rupelian and is followed by the Aquitanian (the lowest stage ...

through

Hemphillian The Hemphillian North American Stage on the geologic timescale is a North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 10,300,000 to 4,900,000 years BP. It is usually considered t ...

~23.03–5.33 mya, calculates to a period of

Location

The Alum Bluff Group replaces the

Hawthorn Group The Hawthorn Group (also Hawthorne Group, previously called Hawthorn(e) Formation) is a stratigraphic unit of Miocene age in South Carolina, Georgia, and Florida, in the United States. It is known for its phosphate rock resources, and for its ric ...

west of 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 ...

with occurrences in

Bay A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a ''gulf'', ''sea'', ''sound'', or ''bight''. A ''cove'' is a small, ci ...

Calhoun John C. Calhoun (1782–1850) was the 7th vice president of the United States. Calhoun can also refer to: Surname * Calhoun (surname) Inhabited places in the United States *Calhoun, Georgia * Calhoun, Illinois *Calhoun, Kentucky * Calhoun, Louis ...

Holmes Holmes may refer to: People and fictional characters * Holmes (surname), a list of people and fictional characters ** Sherlock Holmes, a fictional detective * Holmes (given name), a list of people * Gordon Holmes, a penname used by Louis Trac ...

Jackson Jackson may refer to: Places Australia * Jackson, Queensland, a town in the Maranoa Region * Jackson North, Queensland, a locality in the Maranoa Region * Jackson South, Queensland, a locality in the Maranoa Region * Jackson oil field in Durham, ...

Liberty Liberty is the state of being free within society from oppressive restrictions imposed by authority on one's way of life, behavior, or political views. The concept of liberty can vary depending on perspective and context. In the Constitutional ...

, Okaloosa,

Walton Walton may refer to: People * Walton (given name) * Walton (surname) * Susana, Lady Walton (1926–2010), Argentine writer Places Canada * Walton, Nova Scotia, a community ** Walton River (Nova Scotia) *Walton, Ontario, a hamlet United Kingd ...

, and

Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...

counties. It is younger than the Torreya Formation to the east based on superpositioning. The Alum Bluff Group

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth and other terrestrial planets. Features Outcrops do not cover the majority of the Earth's land surface because in most p ...

s beneath a thin

overburden In mining, overburden (also called waste or spoil) is the material that lies above an area that lends itself to economical exploitation, such as the rock, soil, and ecosystem that lies above a coal seam or ore body. Overburden is distinct from tai ...

in the western panhandle from river valleys in Okloosa County eastward to western Jackson County.

Lithology

The group is composed of

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is usually defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural ...

s and shell beds. These vary from fossil bearing sandy clays to sands, clays, and

carbonate A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...

beds absent of fossil content with

glauconite Glauconite is an iron potassium phyllosilicate ( mica group) mineral of characteristic green color which is very friable and has very low weathering resistance. It crystallizes with a monoclinic geometry. Its name is derived from the Greek ...

and phosphate

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as ''perfect basal cleavage''. Mica is co ...

which is common. The coloration is from cream to olive gray with mottled reddish brown in the weathered sections. The sands are soft and very fine to coarse with sporadic

gravel Gravel () is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentation, sedimentary and erosion, erosive geological processes; it is also produced in large quantities commercially as crushed stone. Gr ...

while carbonate lenses are quite hard. Permeability of the sediments are generally low and are part of the intermediate confining unit/aquifer system.

Subdivision

The Alum Bluff Group are defined by the stratigraphic position and

mollusks Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The num ...

contained within. The group includes: * Chipola Formation * Oak Grove Sand * Shoal River Formation * Choctawhatchee Formation * Jackson Bluff Formation The Alum Bluff Group has a

residuum on Miocene {{Short pages monitor