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Fayetteville Shale

Fayetteville Shale
Stratigraphic range: Carboniferous: Mississippian (Serpukhovian)[1]
Outcrop of the lower Fayetteville Shale in northern Arkansas
Type	Geological formation
Sub-units	Wedington Sandstone Member
Underlies	Pitkin Limestone,[2] Hale Formation[3]
Overlies	Ruddell Shale, Batesville Sandstone[2] Moorefield Shale[3]
Area	Arkansas and Oklahoma[4]
Thickness	50 to 500 feet (15 to 152 m)
Lithology
Primary	Shale
Other	Sandstone, limestone
Location
Region	Arkansas
Country	United States
Extent	50 miles (80 km)
Type section
Named for	Fayetteville, Washington County, Arkansas
Named by	Frederick Willard Simonds[5][6]
The Fayetteville formation runs widespread across Arkansas

Wikimedia Commons has media related to Fayetteville Shale.

The Fayetteville Shale is a geologic formationofMississippian age (354–323 million years ago) composed of tight shale within the Arkoma BasinofArkansas and Oklahoma.^[4][7] It is named for the city of Fayetteville, Arkansas, and requires hydraulic fracturing to release the natural gas contained within.

Nomenclature[edit]

Named by Frederick Willard Simonds in 1891, Simonds recognized what is now the Fayetteville Shale as three separate formations overlying the now abandoned Wyman Sandstone: the Fayetteville Shale, the Batesville Sandstone, and the Marshall Shale.^[6] In 1904, the name "Fayetteville Shale" replaced all three of these names. The Fayetteville Shale that Simonds recognized is now considered as the lower Fayetteville Shale. Simonds' Batesville Sandstone was found to be the same as the Wyman Sandstone, and replaced the name "Wyman Sandstone", while Simonds' Batesville Sandstone became known as the "Wedington Sandstone Member" presumably after Wedington Mountain. The name Marshall Shale was abandoned and is now known as the upper Fayetteville Shale.^[8]

Natural gas[edit]

The formation holds natural gas in a fine-grained rock matrix which requires hydraulic fracturing to release the gas.^[9] This process became cost-effective in some shales such as the Fayetteville after years of experimentation in the Barnett ShaleinNorth Texas, especially when combined with horizontal drilling.

The Fayetteville Shale play began in July 2004 by Southwestern Energy Company in north-central Arkansas with the Thomas #1-9 vertical well in Conway County, Arkansas.^[10] In February 2005, Southwestern Energy drilled the first horizontal well, the Seeco-Vaughan #4-22H, also in Conway County.^[11]

The US Energy Information Administration estimated that the 5,853 square miles (15,160 km²) shale play held 13,240 billion cubic ft (375 billion cubic meters) of unproved, technically recoverable gas.^[7] The average well was estimated to produce 1.3 billion cubic feet of gas.^[12] As of 2018, new drilling in the Fayetteville Shale had ceased and almost 1/5 of wells were abandoned.^[13]

Paleontology[edit]

Flora[edit]

Because the Fayetteville Formation is a marine unit, most of the plants found in the black shales must have been washed into the Carboniferous sea from a landmass. However one unit within the formation, the Weddington Sandstone Member, is a series of river deposited sand beds. Fossil plants from this unit were probably deposited closer to their source.

A. minima^[14]

• Ankyropteris^[15]
• Archaeocalamites

A. fayettevillensis^[14]

A. gracilentus^[14]

A. umbralis^[14]

A. wedingtonensis^[14]

• Bothrodendron^[14]
• Carpolithus

C. inquirenda^[14]

• Cardiopteris

C. hirta^[14]

• Chlamidostachys

C. chesterianus^[14]

• Lepidocystis

L. chesterensis^[14]

• Lepidodendron ^[15]

L. henbesti^[14]

L. occidentale^[14]

L. purduei^[14]

L. wedingtonense^[14]

• Lepidophloios ^[15]
• Lepidophyllum

L. sagittatum^[14]

• Lepidostrobus

L. occidentalis^[14]

• Lepidostrous ^[15]
• Lyginopteris

L. royalii^[16]

• Medullosa ^[15]
• Neuropteris^[14]
• Pachytesta ^[15]
• Rhacopteris^[14]
• Rhynchogonium ^[15]

R. fayettevillense^[14]

• Rhynochosperma

R. quinnii ^[17]

• Sphenopteris

S. (Palmatopteris) erectiloba^[14]

S. (Calymmatotheca) mississippiana^[14]

• Stigmaria

S. arkansana^[14]

S. wedingtonensis^[14]

• Tivena

T. arkansana^[18]

Fauna[edit]

Vertebrates[edit]

• Carcharopsis wortheni^[19]
• "Cobelodus" (remains now attributed to Ozarcus) ^[20]
• Cosmoselachus mehlingi^[21]
• Ozarcus mapesae^[22]

Echinoderms[edit]

• A. planus^[23]

• Childonocrinus trinodus^[23]
• Cymbiocrinus gravis^[23]
• Dasciocrinus aulicus^[23]
• Heliosocrinus aftonensis^[23]
• Intermediacrinus modernus^[23]
• Linocrinus^[23]
• Mantikosocrinus castus^[23]
• Onchyocrinus^[24]
• Onychocrinus pulaskiensis^[23]
• Ophiurocrinus hebdenensis^[23]
• Pentremites platybasis^[25]

• P. pulchellus^[25]

• Phacelocrinus^[23]
• Phanocrinus ^[26]

• P. alexanderi^[23]
• P. cylindricus^[23]
• P. formosus^[23]

• Scytalocrinus aftonensis^[23]
• Taxocrinus cestriensis ^[24][23]

• T. whitefieldi.^[24]

• Ulrichicrinus chesterensis^[23]

Cephalopods[edit]

• Cluthoceras pisiforme ^[27]

• Cravenoceras fayettevillae ^[28][27]

• Cravenoceras lineolatum ^[27]

• Dombarites mapesi ^[27]
• Eurmorphoceras plummeri ^[28][27]
• Fayettevillea planorbis ^[27]
• Girtyoceras ^[29]
• Goniatites granosus ^[28][27]
• Lusitanites subcircularis ^[27]
• Metadimorphoceras wiswellense ^[27]
• Neoglyphioceras crebriliratum ^[27]
• Paracravenoceras ozarkense ^[28][27]
• Paradimorphoceras ^[28]
• Pronorites baconi ^[27]
• Rayonnoceras solidiforme ^[28]
• Tumulites varians ^[28][27]

Corals[edit]

• Amplexus expansus ^[30]
• Michelinia meekana ^[4]
• Palaecris carinata ^[4]

Bivalves[edit]

• Aviculopecten squamula ^[31]

• Aviculopecten jennyi ^[31]
• Aviculopecten multilineatus ^[31]
• Aviculopecten morrowensis ^[31]
• Aviculopecten inspeciosus ^[31]

• Canyella peculiaris ^[31]
• Cardiomorpha inflata ^[31]
• Conocardium peculiare ^[31]
• Cypricardia fayettevillensis ^[31]
• Cyprecardella sublata ^[31]
• Edmondia equilateralis ^[31]
• Palaeoneilo sera ^[31]
• Phestia stevensiana ^[31]
• Solenamorpha nitida ^[31]
• Sphenotus branneri ^[31]

• Sphenotus washingtonensis ^[31]
• Sphenotus dubius ^[31]
• Sphenotus meslerianus ^[31]

Brachiopods[edit]

• Adairia adairensis^[1]
• Inflatia gracilis^[1]

• Inflatia cherokeensis^[1]
• Inflatia pusilla^[1]
• Inflatia inflata^[1]

• Orthotetes protensus^[32]

• Orthotetes subglobosus^[32]

Gastropods[edit]

• Euconospira disjuncta ^[33]
• Mourlonia lativittata ^[33]
• Patellilabia laevigata ^[33]
• Platyceras subelegans ^[33]

• Platyceras compressum ^[33]

• Sinuitina venata ^[33]
• Trepospira discus ^[33]

Arthropods[edit]

• Amphissites^[34]
• Bairdia^[34]
• Cyrtoproetus kerhini^[35]
• Kirkbya ^[34]
• Geisina^[34]
• Glyptopleura^[34]
• Graphiadactyllis^[34]
• Orthobairdia^[34]
• Paladin murconatus ^[36]
• Paraparchites
• Roundyella^[34]
• Sansabella^[34]
• Serenida^[34]

Ostracods[edit]

• Cavellina^[37]
• Kegelites^[37]
• Sargentina^[37]

Bryozoans[edit]

Foraminifera[edit]

• Earlandia^[39]
• Eosigmoilina rugosa^[39]

Trace Fossils[edit]

• Cruziana^[40]
• Planolites^[40]
• Teichichnus^[40]

References[edit]