Yorktown Formation

Yorktown Formation
Stratigraphic range: Early to Middle Pliocene, 4.8–3.15 Ma
↓
Outcrop of the Yorktown Formation at Carters Grove Bluffs along the James River
Typesedimentary
Unit ofChesapeake Group
Sub-unitsSunken Meadow Member, Rushmere Member, Morgarts Beach Member, Moore House Member, Tunnels Mill Member
UnderliesCroatan Formation
OverliesEastover Formation, Pungo River Formation
Lithology
PrimarySandstone, claystone
Othershells
Location
RegionAtlantic Coastal Plain of North America
ExtentMaryland, Virginia, North Carolina, South Carolina
Type section
Named forYorktown, Virginia
Named byClark 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.

Description

The Yorktown is composed largely of overconsolidated sand and clay with abundant calcareous shells, primarily bivalves.

Stratigraphy

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.

Notable exposures

Aurora mine

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]

Age

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]

Fossils

Vertebrate paleobiota

As per the Paleobiology Database:[16]

Cartilaginous fishes

Based on Purdy et al. (2001):[9]

Sharks

Genus Species Locality Notes Images
Alopias A. vulpinus The modern common thresher.
Carcharhinus C. leucas The modern bull shark.
C. macloti The modern hardnose shark.
Carcharodon C. carcharias The modern great white shark.
"C. xiphodon" A relative of the great white shark.
Carcharias C. taurus The modern sand tiger shark.
Chaenogaleus C. affinis A relative of the hooktooth shark.
Echinorhinus E. cf. blakei A bramble shark.
Galeocerdo G. cf. cuvier A tiger shark, potentially the modern tiger shark.
Hemipristis H. serra A relative of the snaggletooth shark.
Hexanchus H. sp. A sixgill shark.
Isistius I. sp. A cookiecutter shark.
Isurus I. oxyrinchus The modern shortfin mako shark.
Lamna L. sp. A relative of the porbeagle.
Megachasma M. sp. A relative of the megamouth shark.
Negaprion N. brevirostris The modern lemon shark.
Notorynchus N. cepedianus The modern broadnose sevengill shark.
Odontaspis O. cuspidata A relative of the smalltooth sand tiger.
Otodus O. megalodon A megatooth shark, the megalodon.
Paragaleus P. sp. A weasel shark.
Parotodus P. benedenii A lamniform shark of uncertain affinities.
Scyliorhinus S. sp. A catshark.
Sphyrna S. lewini The modern scalloped hammerhead.
S. zygaena The modern smooth hammerhead.
S. cf. media A hammerhead shark, potentially the modern scoophead.
Squalus S. sp. A dogfish.
Squatina S. sp. An angelshark.

Rays

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.

Ray-finned fishes

Based on Purdy et al. (2001):[9]

Genus Species Locality Notes Images
Acanthocybium A. solandri The modern wahoo.
Acipenser A. cf. oxyrhynchus A sturgeon, potentially the modern Atlantic sturgeon.
?Agonidae indet. A potential poacher of uncertain affinities.
Alosa A. cf. sapidissima A shad, potentially the modern American shad.
Aluterus A. sp. A filefish.
Ammodytes A. hexapterus The modern Arctic sand lance.
Anisotremus A. sp. A grunt.
Archosargus A. cf. probatocephalus A porgy, potentially the modern sheepshead.
Astroscopus A. sp. A stargazer.
Auxis A. sp. A frigate tuna.
Bagre B. sp. A sea catfish.
Brotula B. barbata The modern bearded brotula.
Caulolatilus C. cf. cyanops A deepwater tilefish, potentially the modern blackline tilefish.
Centropristis C. cf. striata A seabass, potentially the modern black sea bass.
Ceratoscopelus C. maderensis The modern Madeira lanternfish.
Chilomycterus C. schoepfi The modern striped burrfish.
Citharichthys C. sp. A sanddab.
Conger C. cf. oceanicus A conger eel, potentially the modern American conger.
Congridae indet. A conger eel of uncertain affinities.
Cynoscion C. cf. nebulosus A weakfish, potentially the modern spotted seatrout.
Diplectrum D. cf. formosum A sand perch, potentially the modern sand perch.
Epinephelus E. sp. A grouper.
Equetus E. cf. umbrosus A drumfish, potentially the modern cubbyu.
Gadus G. cf. morhua A cod, potentially the modern Atlantic cod.
Istiophorus I. platypterus The modern sailfish.
Kajikia K. albida The modern white marlin.
Kathetostoma K. sp. A stargazer.
Leiostomus L. sp. A relative of the spot.
Lagodon L. cf. rhomboides A porgy, potentially the modern pinfish.
Lopholatilus L. chamaeleonticeps The modern great northern tilefish.
L. rayus An extinct deepwater tilefish.
Lophius L. cf. americanus A monkfish, potentially the modern American anglerfish.
Makaira M. indica The modern black marlin.
M. nigricans The modern Atlantic blue marlin.
M. purdyi[17] An extinct marlin.
Melanogrammus M. cf. aeglefinus A cod, potentially the modern haddock.
Merluccius M. albidus The modern offshore hake.
M. cf. bilinearis A hake, the modern silver hake.
M. sp. A hake.
Merlangiogadus M. congatus An extinct gadid.
Micropogonias M. sp. A drumfish.
Mola M. chelonopsis An extinct ocean sunfish.
Mycteroperca M. sp. A grouper.
Ophidion O. grayi The modern blotched cusk-eel.
Opsanus O. tau The modern oyster toadfish.
Pagrus P. hyneus An extinct relative of the modern common seabream.
Paralichthys P. sp. A largetooth flounder.
Pleuronectidae indet. A righteye flounder of uncertain affinities.
Pogonias P. cf. cromis A drumfish, potentially the modern black drum.
Pomatomus P. saltatrix The modern bluefish.
Prionotus P. cf. evolans A searobin, potentially the modern striped searobin.
Pterothrissus P. sp. A gissu.
Sarda S. aff. sarda A bonito similar to the modern Atlantic bonito.
Sciaenidae indet. A drumfish of uncertain affinities.
Sciaenops S. ocellatus The modern red drum.
Scombridae indet. A mackerel of uncertain affinities.
Seriola S. sp. An amberjack.
Serranidae indet. A seabass of uncertain affinities.
Sphyraena S. cf. barracuda A barracuda, potentially the modern great barracuda.
Sphoeroides S. hyperostosus An extinct pufferfish.
Stenotomus S. cf. chrysops A porgy, potentially the modern scup.
Symphurus S. sp. A tonguefish.
Tautoga T. cf. onitis A wrasse, potentially the modern tautog.
Thunnus T. thynnus The modern Atlantic bluefin tuna.
T. sp. A tuna.
Urophycis U. tenuis The modern white hake.
Xiphias X. gladius The modern swordfish.

Reptiles

Turtles

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.

Crocodilians

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]

Birds

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]

Anseriformes

Genus Species Notes Images
Anas A. acuta A dabbling duck similar to the northern pintail.
A. platyrhynchos A dabbling duck similar to the mallard.
Anser A. cf. arizonae An extinct gray goose.
Anserini indet. A relative of gray geese.
Aythya A. aff. affinis A diving duck similar to the lesser scaup.
Branta B. aff. bernicla A black goose similar to the barnacle goose.
B. minuscula An extinct black goose.
Bucephala B. aff. albeola A diving duck similar to the bufflehead.
B. aff. clangula A diving duck similar to the common goldeneye.
Cygnus C. aff. columbianus A swan similar to the tundra swan.
Histrionicus H. aff. histrionicus A relative of the harlequin duck.
Mareca M. americana A dabbling duck similar to the American wigeon.
Melanitta M. aff. nigra A sea duck similar to the black scoter.
M. aff. perspicillata A sea duck similar to the surf scoter.
Mergus M. aff. serrator A sea duck similar to the common merganser.
Somateria S. sp. A sea duck similar to the common eider.
S. aff. mollissima
Spatula S. clypeata A dabbling duck similar to the northern shoveler.
S. discors A dabbling duck similar to the blue-winged teal.

Galliformes

Genus Species Notes Images
Meleagris M. sp. A turkey.

Phoenicopteriformes

Genus Species Notes Images
Phoenicopterus P. cf. floridanus An extinct flamingo.

Podicipediformes

Genus Species Notes Images
Podiceps P. aff. auritus A grebe similar to the horned grebe.

Gruiformes

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.

Columbiformes

Genus Species Notes Images
Ectopistes E. aff. migratorius A relative of the passenger pigeon.

Accipitriformes

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.

Ciconiiformes

Genus Species Notes Images
Ciconia C. sp. A stork.

Suliformes

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.

Pelecaniformes

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.

Procellariiformes

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.

Gaviiformes

Genus Species Notes Images
Gavia G. concinna An extinct loon.
G. fortis
G. howardae

Odontopterygiformes

Genus Species Notes Images
Pelagornis P. sp. 1. A pseudotooth bird.
P. sp. 2
Charadriiformes
Genus Species Notes Images
Aethiinae indet. An auk of uncertain affinities.
Alca A. ausonia An extinct auk related to the razorbill. Type locality of A. carolinensis, A. minor, and A. olsoni.[20]
A. carolinensis
A. minor
A. olsoni
A. aff. torda An auk similar to the razorbill.
A. sp.
Calidris C. aff. melanotos A sandpiper similar to the pectoral sandpiper.
Cerorhinca C. sp. An auk similar to the rhinoceros auklet.
Chroicocephalus C. aff. ridibundus A gull similar to the black-headed gull.
Fratercula F. aff. arctica A puffin similar to the Atlantic puffin.
F. aff. cirrhata A puffin similar to the tufted puffin.
Gallinago G. media A snipe similar to the great snipe.
Gelochelidon G. aff. nilotica A tern similar to the gull-billed tern.
Haematopus H. aff. palliatus An oystercatcher similar to the American oystercatcher.
H. aff. ostralegus An oystercatcher similar to the Eurasian oystercatcher.
H. sp. An oystercatcher.
Hydrocoloeus H. aff. minutus A gull similar to the little gull.
Larus L. aff. argentatus A gull similar to the herring gull.
L. aff. delawarensis A gull similar to the ring-billed gull.
L. sp. A gull
Leucophaeus L. aff. atricilla A gull similar to the laughing gull.
Numenius N. aff. borealis A curlew similar to the Eskimo curlew.
Pinguinus P. alfrednewtoni A large flightless auk related to the great auk. Type locality of species.
Pluvialis P. aff. squatarola A plover similar to the black-bellied plover.
Stercorarius S. aff. longicaudus A skua similar to the long-tailed jaeger.
S. aff. parasiticus A skua similar to the parasitic jaeger.
S. aff. pomarinus A skua similar to the pomarine jaeger.
S. sp. A skua.
Thalasseus T. aff. maximus A tern similar to the royal tern.
Tringa T. aff. ochropus A sandpiper similar to the green sandpiper.

Passeriformes

Genus Species Notes Images
Corvus C. aff. ossifragus A crow similar to the fish crow.

Mammals

Proboscideans

Genus Species Notes Images
Gomphotherium G. cf. euhypodon A gomphothere.
G. sp.

Xenarthrans

Genus Species Notes Images
Folivora indet. (=Phyllophaga indet) A ground sloth of uncertain affinities.

Carnivorans

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.

Perissodactyls

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.

Artiodactyls

Terrestrial artiodactyls
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.
Cetaceans

Based on:[24]

Genus Species Locality Notes Images
Aprixokogia A. kelloggi A kogiid sperm whale. Type locality of genus and species.[25]
Auroracetus A. bakerae A pontoporiid dolphin. Type locality of genus and species.[26]
Balaena B. palaeatlantica A relative of the bowhead whale. Type locality of species.[27]
?B. prisca An alleged bowhead whale, but more likely a cetothere.[27]
B. ricei A relative of the bowhead whale. Type locality of species.[27]
B. sp.
Balaenoptera B. acutorostrata The modern minke whale.
B. borealina A rorqual whale.
Balaenotus B. sp. A balaenid whale.
Balaenula B. sp. A balaenid whale.
Bohaskaia B. monodontoides A monodontid. Type locality of genus and species.[28]
Cetotheriinae indet. A cetothere.
Cetotherium C. crassangulum A cetothere.
C. polyporum
Delphinapterus D. orcinus A relative of the beluga whale.
D. sp.
Delphinidae indet. An oceanic dolphin.
Delphinus D. sp. A relative of the common dolphin.
Globicephala G. sp. A pilot whale.
Gricetoides G. aurorae An eschrichtiid relative of the gray whale. Type locality of genus and species.[29]
Herpetocetus H. sendaicus A cetothere.
H. transatlanticus
cf. Kogia cf. K. breviceps A kogiid reminiscent of the pygmy sperm whale.[30]
Kogiidae indet. A large kogiid of uncertain affinities.[30]
cf. Kogiopsis cf. K. floridana A kogiid.
Lagenorhynchus L. harmatuki A white-sided dolphin. Type locality of species.[31]
L. sp.
Megaptera M. sp. A relative of the humpback whale.
Mesoplodon M. longirostris A beaked whale.
Mesoteras M. kerrianus A baleen whale. Type locality of genus and species.
cf. Monodon M. sp. A potential relative of the narwhal.
Ninoziphius N. platyrostris A beaked whale.
Orycterocetus O. cornutidens A physeterid.
O. quadratidens
cf. Physeter cf. P. macrocephalus A physeterid, potentially the modern sperm whale.
Physeteridae indet. A physeterid.
cf. Physeterula cf. P. dubusi A physeterid.
cf. Plesiocetus cf. P. sp. A rorqual.
Pliopontos P. littoralis A pontoporiid dolphin.
Pseudorca P. sp A relative of the false killer whale.
cf. Pontoporia cf. P. sp. A pontoporiid dolphin.
cf. Scaldicetus cf S. sp. A physeterid.
Stenella S. rayi An oceanic dolphin.
S. sp.
Tursiops T. sp. A bottlenose dolphin.
Ziphius Z. cavirostris The modern Cuvier's beaked whale.
  • Coral growing on a Crepidula sp. (slipper snail) from the Yorktown Formation
    Coral growing on a Crepidula sp. (slipper snail) from the Yorktown Formation
  • Rushmere Member of the Yorktown Formation, with abundant Chama bivalves
    Rushmere Member of the Yorktown Formation, with abundant Chama bivalves
  • Sunken Meadow Member of the Yorktown Formation
    Sunken Meadow Member of the Yorktown Formation
  • Balanus sp. (barnacles) from Carters Grove Bluffs outcrop, growing on a bivalve
    Balanus sp. (barnacles) from Carters Grove Bluffs outcrop, growing on a bivalve

References

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  2. ^ Pineda-Salgado, G., Schaaf, P., Aguilar-Piña, M., Solís-Pichardo, G., Vega, F.J. (2016). "Contribución al alcance estratigráfico de la Formación Agueguexquite (Mioceno), Veracruz, México". Boletín de la Sociedad Geológica Mexicana. 68 (2): 187–197. Bibcode:2016BoSGM..68..375P. doi:10.18268/BSGM2016v68n2a2.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. ^ Ward, L.W., and Blackwelder, B.W., 1980, Stratigraphic revision of upper Miocene and lower Pliocene beds of the Chesapeake Group, middle Atlantic Coastal Plain, IN Contributions to stratigraphy: U.S. Geological Survey Bulletin, 1482-D, 61 p.
  4. ^ Post-impact Effects of the Eocene Chesapeake Bay Impact, Lower York-James Peninsula, Virginia, 31st Annual Meeting, Virginia Geological Field Conference Archived June 10, 2011, at the Wayback Machine, Williamsburg, Virginia, Oct. 19 and 20, 2001, G.H. Johnson et al. (fieldtrip guidebook)
  5. ^ Tran, Alexandria deRosset, Jennifer (2024-03-19). "Small but mighty: Aurora, North Carolina, is the fossil capital of the world". UNC Media Hub. Retrieved 2025-10-16.{{cite web}}: CS1 maint: multiple names: authors list (link)
  6. ^ a b Spivey, Whittney (2025-01-24). "Biofacies Analysis of Zanclean Sediments in Virginia: Unraveling the Past Through Benthic Foraminifera". Geosciences. 15 (2): 39. Bibcode:2025Geosc..15...39S. doi:10.3390/geosciences15020039. ISSN 2076-3263.
  7. ^ a b Zug, George R. (2001). "Turtles of the Lee Creek Mine (Pliocene: North Carolina)". Biodiversity Heritage Library. Retrieved 2025-10-18.
  8. ^ "PBDB". paleobiodb.org. Archived from the original on 2023-01-08. Retrieved 2025-10-25.
  9. ^ a b c Purdy, Robert W.; Schneider, Vincent P.; Applegate, Shelton P.; McLellan, Jack H.; Meyer, Robert L.; Slaughter, Bob H. (2001). "The Neogene Sharks, Rays, and Bony Fishes from Lee Creek Mine, Aurora, North Carolina". Biodiversity Heritage Library. Retrieved 2025-09-02.
  10. ^ Hazel, J.E., 1971, Ostracode biostratigraphy of the Yorktown Formation (upper Miocene and lower Pliocene) of Virginia and North Carolina: U.S. Geological Survey Professional Paper, 704, 13 p. https://pubs.er.usgs.gov/pubs/pp/pp704[dead link]
  11. ^ Gibson, T.G., 1983, Key Foraminifera from upper Oligocene to lower Pleistocene strata of the U.S. central Atlantic Coastal Plain, IN Ray, C.E., ed., Geology and paleontology of the Lee Creek Mine, North Carolina, I: Smithsonian Contributions to Paleobiology, no. 53, p. 355-454.
  12. ^ Cronin, T.M., 1991, Pliocene shallow water paleoceanography of the North Atlantic Ocean based on marine ostracodes: Quaternary Science Reviews, v. 10, p. 175-188.
  13. ^ Dowsett, Harry J.; Robinson, Marci M.; Foley, Kevin M.; Herbert, Timothy D. (2021-11-24). "The Yorktown Formation: Improved Stratigraphy, Chronology, and Paleoclimate Interpretations from the U.S. Mid-Atlantic Coastal Plain". Geosciences. 11 (12): 486. Bibcode:2021Geosc..11..486D. doi:10.3390/geosciences11120486. ISSN 2076-3263.
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allikas: https://en.wikipedia.org/wiki/Yorktown_Formation