Hawthorn Group | |
---|---|
Stratigraphic range: Miocene | |
Type | Group |
Sub-units | (See text) |
Overlies | Ocala Limestone |
Thickness | > 330 feet |
Location | |
Region | Southeastern United States |
Country | United States |
Type section | |
Named for | Hawthorne, Florida |
Named by | L.C. Johnson, 1887 |
The Hawthorn Group (also Hawthorne Group, previously called Hawthorn(e) Formation) [a] 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 rich assemblages of Neogene vertebrate fossils.
The Waldo Formation was described by L.C. Johnson of the United States Geological Survey in 1887. It was later included in the Hawthorne Beds, named for Hawthorne, Florida, where its phosphate-rich rock was quarried and processed for use as fertilizer. The Hawthrone Beds were later renamed the Hawthorne Formation. Late in the 20th century the Hawthorn Formation was redesignated as the Hawthorn Group consisting of several formations. [3]
The Hawthorn Group is the widest spread stratigraphic unit of Miocene age in the southeastern United States, making up almost the entire thickness of Miocene strata over the area in which it occurs. The Hawthorn group has complex bedding, primarily consisting of clay, silt and sand. Stratigraphy varies, but the group usually consist of three main zones, a lower calcareous zone, a middle clastic zone, and an upper mixed zone of clastic and carbonate rocks. Phosphate deposits are found throughout the Hawthorn group, but particularly in the lower zone, where beds of dolomite and dolomitic limestone are found. Hawthorn Group deposits are mined for phosphate in central Florida. [4]
The Hawthorn group was deposited on a continental shelf. It is predominantly siliciclastic, consisting primarily of fine-to medium-grained quartz sand. Clay is also a component, interstitially and in beds. Other common components of Hawthorn units include phosphate, palygorskite, sepiolite, chert, and dolomite or dolostone. [5]
Period : Neogene
Epoch : Earliest Miocene (Aquitanian) to early Miocene (Burdigalian) in the eastern Florida panhandle, to middle Miocene (Serravallian) in northern Florida, Georgia, and South Carolina, and to earliest Pliocene (Zanclean) in southern Florida, ~23 to ~3.6 mya a period of 19.4 million years [6]
North American land mammal age : Late Arikareean through early Blancan [7]
The Hawthorn Group includes several geologic formations found in southeastern South Carolina, the coastal plain of Georgia, and much of the Florida Peninsula.The Hawthorn Group extends from southeastern South Carolina through the coastal plain of Georgia and the Florida Peninsula to south Florida.
In Florida, the Hawthorn Group encompasses in part the counties of Gilchrist, Levy, Dixie, Citrus, Sumter, Alachua and Marion County. The Hawthorn is also present below undifferentiated sediments (TQu) as well as the Tamiami Formation from Polk County south through Highlands, Glades, Hendry, Dade, Collier, and Monroe County at depths ranging from mean sea level near Polk to below 600 meters in Monroe Co. [8] The Hawthorn overlies Ocala Limestone [9]
The Alachua Formation may have resulted from the weathering of Hawthorn Group sediments, intermixed with Pliocene deposits. Scott does not consider it to be part of the Hawthorn Group. [22]
Reptiles
Birds
Mammals
Fish
The Torreya Formation is a Miocene geologic formation with an outcrop in North Florida. It is within the Hawthorn Group.
The Gulf Trough, also known as the Suwanee Straits, is an ancient geologic feature of Florida present during the Paleogene period. A strong marine current, similar to the Gulf Stream, scoured the trough from southwest to northeast.
The Haile Quarry or Haile sites are an Early Miocene and Pleistocene assemblage of vertebrate fossils located in the Haile quarries, Alachua County, northern Florida. The assemblage was discovered during phosphate mining, which began in the late 1940s. Haile sites are found in the Alachua Formation. Two sites within the Ocala Limestone yielded Upper Eocene Valvatida and mollusks.
The Leon County paleontological sites are assemblages of Early Miocene invertebrates and vertebrates of Leon County, Florida, United States.
The Gadsden County paleontological sites are assemblages of Early Miocene invertebrates and vertebrates occurring in Gadsden County, Florida, United States.
The Coosawhatchie Formation is a Miocene geologic formation with an outcrop in North Florida. It is within the Hawthorn Group.
The Arcadia Formation is an Early Miocene geologic formation in Florida, United States. It is part of the Hawthorn Group.
The Ocala Platform or Ocala Uplift is a geologic feature, a structural high, and a northwest-trending uplift paralleling the Peninsular Arch along the west coast of Florida.
The Chipola Formation is a Late Oligocene to Early Miocene geologic formation in the Florida Panhandle and member of the Alum Bluff Group.
The Peace River Formation is a Late Oligocene to Early Miocene geologic formation in the west-central Florida peninsula.
The Choctaw Sea was a Cenozoic eutropical subsea, which along with the Okeechobean Sea, occupied the eastern Gulf of Mexico basin system bounding Florida.
The Okeechobean Sea was a Cenozoic eutropical subsea, which along with the Choctaw Sea, occupied the eastern Gulf of Mexico basin system bounding Florida.
The Tamiami Formation is a Late Miocene to Pliocene geologic formation in the southwest Florida peninsula.
The Polk County paleontological sites are assemblages of Early Miocene to Late Pleistocene vertebrates occurring in Polk County, Florida, United States.
The Alum Bluff Group is a geologic group in the states of Georgia, Florida, and Alabama. It preserves fossils dating back to the Neogene period.
The Marks Head Formation is a geologic formation within the Hawthorn Group, located in southeastern Georgia and northern Florida. It preserves fossils dating back to the Burdigalian stage of the Miocene period.
The Parachucla Formation is a geologic formation in the southeastern United States. It preserves fossils from the Aquitanian stage of the early Miocene period. The formation is included in the Hawthorn Group. An exposure at the northern end of the formation has produced fossils estimated to be 19.4 to 20.5 Million years ago (Ma). Another exposure at the southern end of the formation has produced fossils estimated to be 23.9 to 24.7 Ma.
The Bone Valley Formation is a geologic formation in Florida. It is sometimes classified as the upper member of the Peace River Formation of the Hawthorn Group. It contains economically important phosphorite deposits that are mined in west-central Florida, as well as rich assemblages of vertebrate fossils.
In 2015, 27.6 million metric tons of marketable phosphate rock, or phosphorite, was mined in the United States, making the US the world's third-largest producer, after China and Morocco. The phosphate mining industry employed 2,200 people. The value of phosphate rock mined was US$2.2 billion.
Dioplotherium is an extinct genus of mammal known from Neogene deposits in the Southeastern United States.
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