Bloyd Formation

The Bloyd Formation, or Bloyd Shale, is a geologic formation in Arkansas. It preserves fossils dating back to the Carboniferous period.

Bloyd Formation
Stratigraphic range: Pennsylvanian
Fossil from the Bloyd Formation
Type	Formation
Sub-units	Baldwin coal,[1] Brentwood Member, Dye Shale Member, Kessler Limestone Member, Parthenon Sandstone Member,[2] and Woolsey Member[3]
Underlies	Atoka Formation
Overlies	Hale Formation
Lithology
Primary	Shale
Other	Sandstone, limestone
Location
Region	Arkansas
Country	United States
Type section
Named for	Bloyd Mountain, Washington County, Arkansas[4]
Named by	Albert Homer Purdue

Stratigraphy

The Bloyd Formation conformably overlies the Hale Formation and unconformably underlies the Atoka Formation. Five formal and one informal members are recognized in the Bloyd Formation (in stratigraphic order):

• Kessler Limestone Member
• Dye Shale Member
• Parthenon Sandstone Member (also known as the "middle Bloyd sandstone")^[5]
• Woolsey Member
• Baldwin coal (an informal unit at the top of the Woolsey Member)
• Brentwood Limestone Member

In the eastern parts of the Ozarks in Arkansas, the Bloyd Formation becomes undifferentiated with the underlying Hale Formation and is called the Witts Springs Formation.

Paleontology

Brachiopods

Anthracospirifer A. newberryi[6] Antiquatonia A. coloradoensis[6] Hustedia H. brentwoodensis[6]

Linoproductus L. nodosus[6] Orthotetes[6] Rhynchopora R. magnicosta[6] Tesuquea T. formosa[6]

Bryozoans

Anisotrypa[7] Coscinotrypa C. fayettevillensis[7] C. gracilens[7] Fenestella F. morrowensis[7] F. serratula[7] F. venusta[7] Fistulipora[7] Glyptopora G. crassitoma[7] Lyropora[8] Matheropora M. triseriata[7]

Polypora P. anastomosa[7] P. constricta[7] P. elliptica[7] P. kesslerensis[7] P. magna[7] P. purduei[7] P. triseriata[7] P. washingtonensis[7] Phyllopora P. cribosa[7] Prismopora P. concava[7]

Rhombopora R. attenuata[7] R. lepidodendroides[7] R. snideri[7] R. tabulata[7] Septopora S. implexa[7] S. reversispina[7] Sulcoretepora S. brentwoodensis[7] S. sinuomarginata[7] Tabulipora T. tuberculata[7]

Cephalopods

Axinolobus A. modulus[9] A. quinni[9] Bisatoceras B. micromphalus[9] B. secundum[9] Boesites B. scotti[9] Branneroceras B. branneri[9] Cancelloceras[9] Cymoceras C. miseri[9] Diaboloceras D. neumeieri[9] Euloxoceras[10]

Gaitherites G. morrowensis[9] Gastrioceras G. adaense[9] G. araium[9] G. attenuatum[9] G. branneri[10] G. fittsi[10][9] Glaphyrites G. depressus[10] G. morrowensis[10] G. oblatus[10] Homoceratoides H. crancens[10] Liroceras[10] Metadimorphoceras M. subdivisum[9]

Mooreoceras M. normale[10] Perigrammoceras[10] Phaneroceras P. compressum[9] P. kesslerense[9] Proshumardites P. morrowanus[10][9] Pseudoparalegoceras P. compressum[10] P. kesslerense[10] Pseudopronorites P. arkansiensis[9] P. quinni[9] Pseudorthoceras P. knoxense[10]

Pygmaeoceras P. pygmaeum[10] P. solidum[10] Solenochilus[10] Stearoceras S. smithi[10] Stenopronorites S. arkansiensis[10] Syngastrioceras S. globosum[9] S. oblatum[9] Verneuilites V. pygmaeus[9] Wiedeyoceras W. smithi[9]

Conodonts

Adetognathus A. gigantus[11] A. lautus[11] Hibbardella[11] Idiognathodus I. sinuosis[11] Idiognathoides I. convexus[11] Ligonodina L. typa[11]

Metalonchodina[11] Neognathodus N. kunamai[11] Neoprioniodus[11] Spathognathodus S. minutus[11] Streptognathodus S. suberectus[11]

Crinoids

Affinocrinus A. grandis[12] A. progressus[12] Alcimocrinus A. girtyi[12] Allocatillocrinus A. rotundus[12] A. rotundus multibrachiatus[12] Anchicrinus A. planulatus[12] A. rugosus[12] Anobasicrinus A. braggsi[12] Arkacrinus A. constrictus[12] A. dubius[12] Atokacrinus A. tumulosus[12] Calycocrinus C. furnishi[12] C. symmetricus[12] Cibolocrinus C. circulus[12] C. regularis[12] C. spinosus[12] C. tumidus[12]

Cromyocrinus C. grandis[12] Dicromyocrinus D. optimus[12] D. subaplatus[12] Diphuicrinus D. croneisi[12] D. pentanodus[12] Endelocrinus E. matheri[12] Globacrocrinus G. pirum[12] Lassanocrinus L. daileyi[12] L. minutus[12] L. multinodus[12] L. nodus[12] L. strigosus[12] Lecythiocrinus L. asymmetricus[12] Megaliocrinus M. aplatus[12] M. exotericus[12] Metacromyocrinus M. gillumi[12] M. papulosus[12]

Metautharocrinus M. cockei[12] M. spinifer[12] Morrowocrinus M. fosteri[12] Palmerocrinus P. kesslerensis[12] Paracromyocrinus P. oklahomensis[12] Paradelocrinus P. aequabilis[12] Paragassizocrinus P. caliculus[12] P. magnus[12] Paramphicrinus P. magnus[12] Perimestocrinus P. pumilus[12] P. teneris[12] Phacelocrinus P. brevis[12] P. rosei[12] Planacrocrinus P. conicus[12] P. minutus[12]

Platyacrocrinus P. brentwoodensis[12] Platycrinites[12] Sciadiocrinus S. cascus[12] S. crassacanthus[12] Scytalocrinus S. crassibrachiatus[12] Stenopecrinus S. ornatus[12] Stereobrachicrinus S. pustulosus[12] Strongylocrinus S. hansoni[12] S. ornatus[12] Ulrichicrinus U. oklahoma[12] U. pentanodus[12]

Flora

• Archaeolithophyllum

A. missouiense^[13]

• Cuneiphycus

C. aliquantulus^[13]

• Donezella^[13]
• Eflugelia^[13]
• Girvanella^[8]

G. minuta^[13]

• Paraepimastopora^[13]
• Stachedoides

S. spissa^[13]

Foraminifera

Ammodiscus[8] Ammovertella[8] Archaediscus[8] Asteroarchaediscus A. rugosus[13] Biseriella[13] Calcitornella[13] C. adherens[13] Climacammina[8] Diplospahaerina D. inaequalis[13] Endothyra[8][13] Endothyranella[8] Eolasiodiscus E. donbassicus[13]

Eosigmoilina[8] Eostafella[8][13] Hemigordius H. harltoni[13] Millerella M. marblensis[8][13] M. pressa[13] Monotaxinoides M. transitorius[13] Neoarchaediscus[13] Palaeonubecularia[13] Paramillerella P. pinguis[8] Planoendothyra P. evoluta[13]

Plectogyra[8] Pseudoglomospira[13] Tetrataxis[8] T. maxima[13] Trepeilopsis[8] T. minima[13] Tuberatina[8] T. plana[13] Turrispiroides T. multivolutus[13]

Ostracods

• Amphissites

A. confluens^[14]

A. nodosus^[14]

A. rothi^[14]

• Bairdiolites^[15]
• Hollinella

H. bassleri^[14]

• Kegelites^[15]
• Kirkbya^[15]

K. bendensis^[14]

K. jolliffana^[14]

• Pseudoparaparchites^[15]

Sponges

• Haplistion

H. sphaericum^[16]

• Steioderma

S. hadra^[16]

• Virgaspongia

V. ichnata^[16]

Trace Fossils

• Conostichus

C. arkansanus^[17]

Incertae sedis

• Asphaltina

A. cordillerensis^[13]

• Clacisphaera

C. laevis^[13]

• Nostocites^[13]
• Osagia^[13]
• Proninella

P. strigosa^[13]

See also

• Paleontology portal

• List of fossiliferous stratigraphic units in Arkansas
• Paleontology in Arkansas