| Yorktown Formation | |
|---|---|
| Stratigraphic range: Early to Middle Pliocene, | |
| Outcrop of the Yorktown Formation at Carters Grove Bluffs along the James River | |
| Type | sedimentary |
| Unit of | Chesapeake Group |
| Sub-units | Sunken Meadow Member, Rushmere Member, Morgarts Beach Member, Moore House Member, Tunnels Mill Member |
| Underlies | Croatan Formation |
| Overlies | Eastover Formation, Pungo River Formation |
| Lithology | |
| Primary | Sandstone, claystone |
| Other | shells |
| Location | |
| Region | Atlantic Coastal Plain of North America |
| Extent | Maryland, Virginia, North Carolina, South Carolina |
| Type section | |
| Named for | Yorktown, Virginia |
| Named by | Clark and Miller, 1906 [1] |
The Yorktown Formation is a mapped bedrock unit in the Coastal Plain of Maryland, Virginia, North Carolina and South Carolina. It is overconsolidated and highly fossiliferous.
The Yorktown is composed largely of overconsolidated sand and clay with abundant calcareous shells, primarily bivalves.
The Yorktown unconformably overlies the Miocene Eastover Formation, and conformably underlies the Pliocene Croatan Formation. [2]
The Yorktown was divided into members by Ward and Blackwelder (1980). These are in ascending order: Sunken Meadow Member, Rushmere Member, Morgarts Beach Member, and Moore House Member. [3] The uppermost Tunnels Mill Member is recognized in Maryland only.
The most diverse paleobiota of the Yorktown Formation has been recovered from the Aurora mine of Beaufort County, North Carolina, where it overlies the intensively-mined Pungo River Formation. As with the Pungo River Formation, this locality has become a prime target for fossil collecting, and some of the most notable fossils from both formations are displayed at the Aurora Fossil Museum. [5] Foraminiferal analyses suggests that this locality belongs the Early Pliocene-aged Sunken Meadow Member. [6] The Yorktown fauna at the Aurora mine is far more diverse than the Pungo River fauna from the same locality, as the Pungo River sediments are mechanically processed for their phosphorite, while the Yorktown sediments are discarded and are thus in better condition for study. [7] This locality was likely deposited in an bay, with older sediments being deposited at a depth of 80 to 100 metres (260 to 330 ft) underwater, while younger sediments were deposited at a depth of 30 metres (98 ft) underwater. [8]
Clear differences are seen in the paleoichthyofauna of the Pungo River Formation and the overlying Yorktown Formation at the Aurora mine, with the Pungo River fauna representing almost exclusively warm-water taxa, while the Yorktown fauna preserves both warm and cooler-water taxa. These fossils provide important evidence for the significant cooling of ocean temperatures between the Miocene and Pliocene. However, the invertebrate fauna from both time periods appears to have cool-temperate affinities. [9]
Hazel (1971) revised the age of the Yorktown from Miocene to Late Miocene to Early Pliocene using ostracod biostratigraphy. [10] The age was revised by Gibson (1983) to extend into the Middle Pliocene based on foraminifera. [11] Further biostratigraphic work with ostracods and foraminifera was completed by Cronin (1991), which also summarized previous investigations. [12] More recently, Spivey (2025) dated the Sunken Meadow Member to the Zanclean stage, about 4.8 to 3.8 million years ago [6] , while Dowsett et al (2001) dated the Rushmere and Morgarts Beach Members to the early-mid Piacenzian stage, about 3.3 to 3.15 million years ago. The deposition of these latter two members is thought to be linked to a marine transgression caused by the mid-Piacenzian warm period. [13]
As per the Paleobiology Database: [16]
Based on Purdy et al. (2001): [9]
| Genus | Species | Locality | Notes | Images |
|---|---|---|---|---|
| Aetobatus | A. sp. | An eagle ray. | | |
| Bathytoshia (=Dasyatis) | B. centroura | The modern roughtail stingray. | | |
| Mobula | M. sp. | A devil ray. | | |
| Pristis | P. cf. pectinatus | A sawfish, potentially the modern smalltooth sawfish. | | |
| Raja | R. sp. | A skate. | |
Based on Purdy et al. (2001): [9]
Based partly on Zug (2001): [7]
| Genus | Species | Locality | Notes | Images |
|---|---|---|---|---|
| Apalone | cf. A. sp. | A softshell turtle. | ||
| Caretta | C. patriciae | An extinct relative of the loggerhead sea turtle. | ||
| Chelonia | ?C.sp. | A potential relative of the green sea turtle. | ||
| Chrysemys | C. sp. | A painted turtle. | ||
| "Geochelone" | "G." sp. | A tortoise. | ||
| Lepidochelys | L. sp. | A Ridley sea turtle. | ||
| Procolpochelys | P. sp. | A sea turtle. | ||
| Psephophorus | P. sp. | A relative of the leatherback turtle. | ||
| Syllomus | S. aegyptiacus | A sea turtle. |
| Genus | Species | Locality | Notes | Images |
|---|---|---|---|---|
| Thecachampsa | T. antiqua [18] | Lee Creek Mine | A gavialoid crocodilian, one of the northernmost Pliocene records of the genus. [18] | |
Based on Olson & Rasmussen (2001). An extremely high diversity of fossil birds, primarily known from isolated but diagnostic limb bones, is known from the formation. All specimens were collected from the Lee Creek Mine. Most taxonomic assignments were based on rough similarity to living species, hence the "aff." suffix to indicate similarities, and are not intended to be meant as direct taxonomic assignments. [19]
| Genus | Species | Notes | Images |
|---|---|---|---|
| Meleagris | M. sp. | A turkey. |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Phoenicopterus | P. cf. floridanus | An extinct flamingo. |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Podiceps | P. aff. auritus | A grebe similar to the horned grebe. |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Antigone | A. aff. antigone | A crane similar to the sarus crane. | |
| Grus | G. aff. americana | A crane similar to the whooping crane. |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Ectopistes | E. aff. migratorius | A relative of the passenger pigeon. | |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Accipitridae indet. | A hawk of uncertain affinities. | ||
| Buteo | B. jamaicensis | A hawk similar to the red-tailed hawk. | |
| ?B. sp. | A hawk. | ||
| Cathartidae indet. | A New World vulture of uncertain affinities. | ||
| Neophrontops | ?N. sp. | An Old World vulture. | |
| Pandion | P. sp. | A relative of the osprey. |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Ciconia | C. sp. | A stork. |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Morus | M. avitus | An extinct gannet. | |
| M. atlanticus | |||
| M. peninsularis | |||
| M. loxostyla | |||
| M. sp. | |||
| Phalacrocorax | P. wetmorei | An extinct cormorant. | |
| P. sp. |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Ardea | A. aff. cinerea | A heron similar to the gray heron. | |
| Eudocimus | E. sp. | An ibis. | |
| Pelecanus | P. schreiberi | An extinct giant pelican, type locality of species. |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Ardenna | A. sp. | A shearwater. | |
| A. tenuirostris | A shearwater similar to the short-tailed shearwater. | ||
| A. gravis | A shearwater similar to the great shearwater. | ||
| ?Bulweria sp. | A petrel. | ||
| Calonectris | C. aff. diomedea | A shearwater similar to Scopoli's shearwater. | |
| C. borealis | A shearwater similar to Cory's shearwater. | ||
| C. krantzi | An extinct shearwater. | ||
| Pachyptila | P. sp. | A prion. | |
| Phoebastria | P. aff. albatrus | An albatross similar to the short-tailed albatross. | |
| P. aff. immutabilis | An albatross similar to the Laysan albatross. | ||
| P. nigripes | An albatross similar to the black-footed albatross. | ||
| P. rexularum | An extinct albatross. | ||
| P. anglica | An extinct albatross. | ||
| Procellaria | P. cf. parkinsoni | A petrel similar to the black petrel. | |
| P. cf. aequinoctialis | A petrel similar to the white-chinned petrel. | ||
| Pterodroma | P. lessonii | A petrel similar to the white-headed petrel. | |
| Pterodromoides | P. minoricensis | An extinct petrel. | |
| Puffinus | P. cf. puffinus | A shearwater similar to the Manx shearwater. | |
| P. aff. pacificoides | A shearwater similar to the Saint Helena shearwater. | ||
| P. lherminieri | A shearwater similar to the Sargasso shearwater. | ||
| P. sp. | A shearwater. | ||
| P. (Thyellodroma) sp. |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Gavia | G. concinna | An extinct loon. | |
| G. fortis | |||
| G. howardae |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Pelagornis | P. sp. 1. | A pseudotooth bird. | |
| P. sp. 2 |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Corvus | C. aff. ossifragus | A crow similar to the fish crow. |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Gomphotherium | G. cf. euhypodon | A gomphothere. | |
| G. sp. |
| Genus | Species | Notes | Images |
|---|---|---|---|
| Folivora indet. (=Phyllophaga indet) | A ground sloth of uncertain affinities. |
| Genus | Species | Locality | Notes | Images |
|---|---|---|---|---|
| Auroraphoca | A. atlantica | Lee Creek Mine | An earless seal. Type locality of genus and species. [21] | |
| Borophagus | B. cf. dudleyi | Lee Creek Mine | A bone-crushing dog. | |
| B. cf. orc | ||||
| B. sp. | ||||
| Callophoca | C. obscura | Lee Creek Mine, Meherrin River, Superior Stone Company Quarry | An earless seal. | |
| Felidae indet. | Lee Creek Mine | A cat of uncertain affinities. | ||
| Gryphoca | G. similis | Lee Creek Mine | An earless seal. | |
| Hadrokirus | H. novotini | Meherrin River | An earless seal. Type locality of species. [22] | |
| Homiphoca | ?H. capensis | Lee Creek Mine | A monachine earless seal. Type locality of H. murfreesi. [22] | |
| H. murfreesi | Meherrin River | |||
| Leptophoca | L. lenis | Meherrin River | An earless seal. Type locality of species. [22] | |
| Lobodontini indet. | Meherrin River | A relative of Antarctic seals, of uncertain affinities. [22] | ||
| Mesotaria | M. ambigua | Lee Creek Mine | An earless seal. | |
| Ontocetus | O. emmonsi | Multiple | An odobenid related to the walrus. Type locality for genus and species. | |
| Monachinae indet. | Lee Creek Mine | A monachine seal of uncertain affinities. | ||
| Paleophoca | P. nystii | Lee Creek Mine | An earless seal. | |
| Phocanella | P. pumila | Lee Creek Mine | An earless seal. Type locality of species. [22] | |
| Platyphoca | P. vulgaris | Lee Creek Mine | An earless seal. | |
| Sarcodectes | S. magnus | Lee Creek Mine, Meherrin River | An earless seal. Type locality of genus and species. [23] | |
| Ursidae indet. | Lee Creek Mine | A bear of uncertain affinities. | ||
| Virginiaphoca | V. magurai | Nottoway River | An earless seal. Type locality of genus and species. [21] |
| Genus | Species | Locality | Notes | Images |
|---|---|---|---|---|
| Nannippus | N. lenticularis | Lee Creek Mine | An equid. | |
| Neohipparion | N. eurystyle | An equid. | | |
| Pseudhipparion | P. simpsoni | An equid. | | |
| Rhinocerotidae indet. | A rhinoceros. | |||
| Tapirus | T. sp. | A tapir. | |
| Genus | Species | Locality | Notes | Images |
|---|---|---|---|---|
| Antilocapridae indet. | Lee Creek Mine | An antilocaprid of uncertain affinities. | ||
| Camelidae indet. | A camelid of uncertain affinities. | |||
| cf. Hemiauchenia | cf. H. sp. | A lamine camelid. | | |
| Kyptoceras | K. amatorum | A protoceratid. | | |
| Pediomeryx | P. sp. | A dromomerycid. | ||
| Ruminantia indet. | A ruminant of uncertain affinities. | |||
| Tayassuidae indet. | A peccary of uncertain affinities. |
Based on:
| Genus | Species | Locality | Notes | Images |
|---|---|---|---|---|
| Aprixokogia | A. kelloggi | |||
| Auroracetus | A. bakerae | A pontoporiid dolphin. Type locality of genus and species. [24] | ||
| Balaena | B. palaeatlantica | A relative of the bowhead whale. Type locality of species. [25] | ||
| ? B. prisca | An alleged bowhead whale, but more likely a cetothere. [25] | |||
| B. ricei | A relative of the bowhead whale. Type locality of species. [25] | |||
| B. sp. | ||||
| Balaenoptera | B. acutorostrata | |||
| B. borealina | ||||
| Balaenotus | B. sp. | |||
| Balaenula | B. sp. | |||
| Bohaskaia | B. monodontoides | A monodontid. Type locality of genus and species. [26] | ||
| Cetotheriinae indet. | ||||
| Cetotherium | C. crassangulum | |||
| C. polyporum | ||||
| Delphinapterus | D. orcinus | |||
| D. sp. | ||||
| Delphinidae indet. | ||||
| Delphinus | D. sp. | |||
| Globicephala | G. sp. | |||
| Gricetoides | G. aurorae | |||
| Herpetocetus | H. sendaicus | |||
| H. transatlanticus | ||||
| Isoninia | I. borealis | An iniid dolphin. Type locality of genus and species. Potentially from the Eastover Formation. [27] | ||
| cf. Kogia | cf. K. breviceps | A kogiid reminiscent of the pygmy sperm whale. [28] | ||
| Kogiidae indet. | A large kogiid of uncertain affinities. [28] | |||
| cf. Kogiopsis | cf. K. floridana | |||
| Lagenorhynchus | L. harmatuki | A white-sided dolphin. Type locality of species. [29] | ||
| L. sp. | ||||
| Megaptera | M. sp. | |||
| Meherrinia | M. isoni | An iniid dolphin. Type locality of genus and species. Potentially from the Eastover Formation. [27] | ||
| Mesoplodon | M. longirostris | |||
| Mesoteras | M. kerrianus | A baleen whale. Type locality of genus and species. | ||
| cf. Monodon | M. sp. | |||
| Ninoziphius | N. platyrostris | |||
| Orycterocetus | O. cornutidens | |||
| O. quadratidens | ||||
| cf. Physeter | cf. P. macrocephalus | A physeterid, potentially the modern sperm whale. | ||
| Physeteridae indet. | ||||
| cf. Physeterula | cf. P. dubusi | |||
| cf. Plesiocetus | cf. P. sp. | |||
| Pliopontos | P. littoralis | |||
| Pseudorca | P. sp | |||
| cf. Pontoporia | cf. P. sp. | |||
| cf. Scaldicetus | cf S. sp. | |||
| Stenella | S. rayi | |||
| S. sp. | ||||
| Tursiops | T. sp. | |||
| Ziphius | Z. cavirostris |
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