The Anastasia Formation is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

deposited in

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, a ...

during the

Late Pleistocene The Late Pleistocene is an unofficial age in the international geologic timescale in chronostratigraphy, also known as Upper Pleistocene from a stratigraphic perspective. It is intended to be the fourth division of the Pleistocene Epoch within ...

epoch.

Age

Period : Quaternary

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 by ...

Pleistocene The Pleistocene ( , often referred to as the '' Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed ...

~2.558 to 0.012

mya Mya may refer to: Brands and product names * Mya (program), an intelligent personal assistant created by Motorola * Mya (TV channel), an Italian Television channel * Midwest Young Artists, a comprehensive youth music program Codes * Burmese ...

, calculates to a period of
Faunal stage:

Blancan The Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 4,750,000 to 1,806,000 years BP, a period of .Rancholabrean The Rancholabrean North American Land Mammal Age on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from less than 240,000 years to 11,000 years BP, a ...

Location

Anastasia Formation overlies the Atlantic Coastal Ridge along the coast from St. John's County southward to

Palm Beach County Palm Beach County is a county located in the southeastern part of Florida and lies directly north of Broward County and Miami-Dade County. The county had a population of 1,492,191 as of the 2020 census, making it the third-most populous count ...

and extends inland as far as 20 miles (32 kilometers) in St. Lucie and Martin County. Blowing Rocks Preserve in southern Martin County is an exposed outcropping along the beach.http://sofia.usgs.gov/publications/reports/mgs_lovejoy1998/ USGS Publications, Classic Exposures of the Anastasia Formation in Martin and Palm Beach Counties, Florida. A second outcropping is seen at

Washington Oaks Gardens State Park Washington Oaks Gardens State Park is a Florida State Park located near Palm Coast, Florida, along A1A. The park is most famous for its formal gardens, but it also preserves the original habitat of a northeast Florida barrier island. Ecolo ...

in northern Flagler County, south of St. Augustine.

History

The Anastasia Formation was named by E. H. Sellards in 1912.

Coquina Coquina () is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically sorted fragments of the shells of mollusks, trilobites, brachiopods, or other invertebrates. The term ''coquina'' ...

obtained from this formation on

Anastasia Island Anastasia Island is a barrier island located off the northeast Atlantic coast of Florida in the United States. It sits east of St. Augustine, running north–south in a slightly southeastern direction to Matanzas Inlet. The island is about lon ...

was used to construct

Castillo de San Marcos The Castillo de San Marcos (Spanish for "St. Mark's Castle") is the oldest masonry fort in the continental United States; it is located on the western shore of Matanzas Bay in the city of St. Augustine, Florida. It was designed by the Spanish ...

during the late 17th century; a local material, it was relatively easy to quarry and proved to be effective for absorbing

cannon A cannon is a large-caliber gun classified as a type of artillery, which usually launches a projectile using explosive chemical propellant. Gunpowder ("black powder") was the primary propellant before the invention of smokeless powder duri ...

damage. This formation is an integral part of the surficial aquifer system. Formed through multicyclic deposition the formation contains at least two disconformities, and two detectable ages. The formation registers in the late Pleistocene with oldest samples aging at 110,000 YBP based on radiometric dating (U²³⁴/Th²³⁰).

Composition

The Anastasia Formation is composed of

quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...

sands and

calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scra ...

coquina Coquina () is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically sorted fragments of the shells of mollusks, trilobites, brachiopods, or other invertebrates. The term ''coquina'' ...

, with sporadic instances of fossil debris. Coloration of the formation varies from a light grey tone to a soft orange-brown. The formation is soft to moderately hard

composed of whole and fragmented

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is es ...

shells within sand often cemented by sparry

.USGS Publications, Lithostratigraphic Units, Tertiary System, Pleistocene Series
/ref> Sands occur as fossil-bearing light gray to tan as well as orange-brown, unconsolidated to moderately indurated. Fossils consist of both vertebral and invertebral species most of which are still present in the current epoch. Poriferans,

bryozoans Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a l ...

mollusks Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

arthropods Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, oft ...

, and

echinoderms An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the ...

have all been seen and recorded within the formation. Vertebrate taxa include

cetacean Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...

testudines Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked ...

, perissodactyla, and selachimorpha. Most fossils are highly fragmented with greatest preservation seen in the Blowing Rocks Preserve in Martin County, and regions north of Palm Beach.

Bioturbation Bioturbation is defined as the reworking of soils and sediments by animals or plants. It includes burrowing, ingestion, and defecation of sediment grains. Bioturbating activities have a profound effect on the environment and are thought to be a pr ...

is also seen in Palm Beach, Martin and Flagler counties. Large and small fossilized burrows formed by invertebrate species are seen in Palm Beach and Martin Counties whereas Flagler County sees large borings formed and fossilized around trees previously present in the area. The Formation is seen as a relevant portion of the Biscayne Aquifer. It is also an integral part of the surficial aquifer system in northern portions of Florida.

References

{{reflist Geologic formations of Florida Quaternary geologic formations Limestone formations Shallow marine deposits Paleontology in Florida