Choptank Formation

Choptank Formation
Choptank Formation
Stratigraphic range: Middle Miocene (Langhian to Tortonian) PreꞒ Ꞓ O S D C P T J K Pg N ↓
	Chesapecten nefrens, Choptank Formation
Type	Formation
Unit of	Chesapeake Group
Underlies	St. Marys Formation
Overlies	Calvert Formation
Location
Region	Virginia, Maryland
Country	United States
Type section
Named for	Choptank River

Last updated February 15, 2026

The Choptank Formation is a geologic formation in Virginia and Maryland. It preserves fossils dating from the mid-late Miocene of the Neogene period, from the latest Langhian to the early Tortonian (13.9 to 11 million years ago).^[1]

Fossils

The Choptank Formation is extremely fossiliferous. Some of the fossil species represented include the following:^[2]^[3]

Sharks

Rays and Other Cartilaginous Fish

Aetobatus arcuatus
Pteromyaleus sp.
Dasyatis rugosa
Dasyatis probsti
Pinthicus stenodon

Fish

Cetaceans

Pinnipeds

Crocodilians

Thecachampsa antiquus
Thecachampsa sericodon

Invertebrates

^[4]

Terrestrial Mammals

Cynarctus wangi
Gomphotherium calvertensis
Hipparion cf. phosphorum

References

↑ Carnevale, Giorgio; Godfrey, Stephen James (2018). "Miocene bony fishes from the Calvert, Choptank, St. Marys and Eastover Formations, Chesapeake Group, Maryland and Virginia". Smithsonian Contributions to Paleobiology (100).
↑ Godfrey, Stephen J., ed. (2018-09-25). "The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA". Smithsonian Contributions to Paleobiology (100): 2–274. doi: 10.5479/si.1943-6688.100 . ISSN 1943-6688.
↑ "Paleobiology Collections Search". collections.nmnh.si.edu. Retrieved 2020-08-14.
↑ "Collections". The Fossil Forum. Retrieved 2020-08-14.

Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database" . Retrieved 17 December 2021.

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[1] Carnevale, Giorgio; Godfrey, Stephen James (2018). "Miocene bony fishes from the Calvert, Choptank, St. Marys and Eastover Formations, Chesapeake Group, Maryland and Virginia". Smithsonian Contributions to Paleobiology (100).

[2] Godfrey, Stephen J., ed. (2018-09-25). "The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA". Smithsonian Contributions to Paleobiology (100): 2–274. doi: 10.5479/si.1943-6688.100 . ISSN 1943-6688.

[3] "Paleobiology Collections Search". collections.nmnh.si.edu. Retrieved 2020-08-14.

[4] "Collections". The Fossil Forum. Retrieved 2020-08-14.

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