Calvert Formation

Calvert Formation
Stratigraphic range:
Outcrops of the Calvert Formation at the Calvert Cliffs State Park
TypeFormation
Unit ofChesapeake Group
UnderliesChoptank Formation
OverliesOld Church Formation
Location
RegionMaryland, Virginia, Delaware
CountryUnited States
Type section
Named forCalvert County

The Calvert Formation is a geologic formation in Maryland, Virginia, and Delaware. It preserves fossils dating back to the early to middle Miocene epoch of the Neogene period, between 23 and 14 million years ago.[1] It is one of the three formations which make up the Calvert Cliffs, all of which are part of the Chesapeake Group.

Fossils

The Calvert Formation is extremely fossiliferous, although the most fossiliferous layers constitute a relative small section of it, dating to about 16 to 14.5 million years ago. Sediments under these layers are composed of either fine sand with few shells or (for the earliest layers) diatomite.[1] Some of the fossil species represented include the following:[2][3]

Chondrichthyes

Holocephalians

Genus Species Family Location Stratigraphic Position Material Notes Images
Edaphodon E. sp Callorhynchidae two well preserved mandibular plates Similar to E. sweeti
Ischyodus I.sp Callorhynchidae many tooth fragments occasional mandibular plates
Chimaera C. sp Cimaeridae

Elasmobranchii

Genus Species Location Family Stratigraphic Position Material Notes Images
Notorynchus N. primigenius Hexanchidae Similar to extant N. cepedianus but differs in distribution.
Hexanchus H. gigas Hexanchidae Far less common then N. primigenus
Echinorhinus E. blakei Echinorhinidae Teeth and bramble thorns One of the rarest sharks in the cliffs, prefers deeper waters
Squalus S. sp. 1

S. sp. 2

Squalidae Very rare Two forms of teeth, one (S.sp 2) similar to Squalus acanthias
Squatina S.sp Squatinidae Teeth and Dermal thorns
Rhincodon R. typus Rhincodonidae Very similar to modern R. typus
Carcharias C. cuspidatus

C. taurus C. reticulatus

odontaspididae

Rays and other cartilaginous fish

Bony fish

Cetaceans

Pinnipeds

Crocodilians

Invertebrates

Terrestrial mammals

Birds

See also

References

  1. ^ a b 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.
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