Yorktown Formation

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.
The Yorktown was divided into members by Ward and Blackwelder. These are in ascending order: Sunken Meadow Member, Rushmere Member, Morgarts Beach Member, and Moore House Member. The uppermost Tunnels Mill Member is recognized in Maryland only.

Notable exposures

Type Section: Yorktown, Virginia on southwest side of York River, York County
Carters Grove Bluffs, north side of James River
Moore House Bluff, southwest side of York River, York County

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. Foraminiferal analyses suggests that this locality belongs the Early Pliocene-aged Sunken Meadow Member. 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. This locality was likely deposited in an bay, with older sediments being deposited at a depth of underwater, while younger sediments were deposited at a depth of underwater.
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.

Age

Hazel revised the age of the Yorktown from Miocene to Late Miocene to Early Pliocene using ostracod biostratigraphy. The age was revised by Gibson to extend into the Middle Pliocene based on foraminifera. Further biostratigraphic work with ostracods and foraminifera was completed by Cronin, which also summarized previous investigations. More recently, Spivey dated the Sunken Meadow Member to the Zanclean stage, about 4.8 to 3.8 million years ago, while Dowsett et al 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.

Fossils

Bivalves, including Glycymeris subovata, Chesapecten jeffersonius, Chesapecten madisonius, Mercenaria tridacnoides, Panopera reflexa, Chama, Ensis, Striarca and Noetia, Cerastoderma, Dosinia, Mulinia, Kuphus, Panope, and the oyster Ostrea
Gastropods, including Crucibulum, Calliostoma, Busycon, Turritella, and Crepidula
Foraminifera, including the biostratigraphic marker species Dentoglobigerina altispira, Sphaeroidinellopsis, and Globorotalia puncticulata
Scleractinian corals, including Septastrea marylandica, Paracyathus vaughani, and Astrangia lineata
Ostracods
Bryozoans
Barnacles, including Balanus
Worms
Sponges
Birds, including the large pelican Pelecanus schreiberi.
Whales, including the prehistoric sperm whale Scaldicetus.

Vertebrate paleobiota

As per the Paleobiology Database:

Cartilaginous fishes

Based on Purdy et al. :

Ray-finned fishes

Based on Purdy et al. :

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.
Lopholatilus	L. rayus		An extinct deepwater tilefish.
Lophius	L. cf. americanus		A monkfish, potentially the modern American anglerfish.
Makaira	M. indica		The modern black marlin.
Makaira	M. nigricans		The modern Atlantic blue marlin.
Makaira	M. purdyi		An extinct marlin.
Melanogrammus	M. cf. aeglefinus		A cod, potentially the modern haddock.
Merluccius	M. albidus		The modern offshore hake.
Merluccius	M. cf. bilinearis		A hake, the modern silver hake.
Merluccius	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.
Thunnus	T. sp.		A tuna.
Urophycis	U. tenuis		The modern white hake.
Xiphias	X. gladius		The modern swordfish.

Reptiles

Turtles

Based partly on Zug :

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.

Birds

Based on Olson & Rasmussen. 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.

Ciconiiformes

Odontopterygiformes

Charadriiformes

Mammals

Artiodactyls

Terrestrial artiodactyls

Cetaceans

Based on:

Genus	Species	Locality	Notes	Images
Aprixokogia	A. kelloggi
Auroracetus	A. bakerae		A pontoporiid dolphin. Type locality of genus and species.
Balaena	B. palaeatlantica		A relative of the bowhead whale. Type locality of species.
Balaena	?B. prisca		An alleged bowhead whale, but more likely a cetothere.
Balaena	B. ricei		A relative of the bowhead whale. Type locality of species.
Balaena	B. sp.
Balaenoptera	B. acutorostrata
Balaenoptera	B. borealina
Balaenotus	B. sp.
Balaenula	B. sp.
Bohaskaia	B. monodontoides		A monodontid. Type locality of genus and species.
Cetotheriinae indet.
Cetotherium	C. crassangulum
Cetotherium	C. polyporum
Delphinapterus	D. orcinus
Delphinapterus	D. sp.
Delphinidae indet.
Delphinus	D. sp.
Globicephala	G. sp.
Gricetoides	G. aurorae
Herpetocetus	H. sendaicus
Herpetocetus	H. transatlanticus
Isoninia	I. borealis		An iniid dolphin. Type locality of genus and species. Potentially from the Eastover Formation.
cf. Kogia	cf. K. breviceps		A kogiid reminiscent of the pygmy sperm whale.
Kogiidae indet.			A large kogiid of uncertain affinities.
cf. Kogiopsis	cf. K. floridana
Lagenorhynchus	L. harmatuki		A white-sided dolphin. Type locality of species.
Lagenorhynchus	L. sp.
Megaptera	M. sp.
Meherrinia	M. isoni		An iniid dolphin. Type locality of genus and species. Potentially from the Eastover Formation.
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
Orycterocetus	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
Stenella	S. sp.
Tursiops	T. sp.
Ziphius	Z. cavirostris