The Blakely Sandstone is a Middle

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

in the

Ouachita Mountains The Ouachita Mountains (), simply referred to as the Ouachitas, are a mountain range in western Arkansas and southeastern Oklahoma. They are formed by a thick succession of highly deformed Paleozoic strata constituting the Ouachita Fold and Thru ...

Arkansas Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the Osage ...

and

Oklahoma Oklahoma (; Choctaw language, Choctaw: ; chr, ᎣᎧᎳᎰᎹ, ''Okalahoma'' ) is a U.S. state, state in the South Central United States, South Central region of the United States, bordered by Texas on the south and west, Kansas on the nor ...

. First described in 1892, this unit was not named until 1909 by Albert Homer Purdue in his study of the Ouachita Mountains of Arkansas. Purdue had initially named this unit the Caddo Shale at a 1907

Geological Society of America The Geological Society of America (GSA) is a nonprofit organization dedicated to the advancement of the geosciences. History The society was founded in Ithaca, New York, in 1888 by Alexander Winchell, John J. Stevenson, Charles H. Hitchco ...

meeting, but later redefined and renamed the unit as the Ouachita Shale. He again renamed the unit to the Blakely Sandstone in a letter to

Edward Oscar Ulrich Edward Oscar Ulrich (1 February 1857, in Covington, Kentucky – 22 February 1944, in Washington, D.C.) was an invertebrate paleontologist specializing in the study of Paleozoic fossils. Biography Ulrich was educated at Wallace College and the O ...

, to which Ulrich used in a 1911 publication, becoming the first reference using this name. Ulrich assigned the Blakely Mountain in Garland County, Arkansas as the type locality, but did not designate a

stratotype A stratotype or type section in geology is the physical location or outcrop of a particular reference exposure of a stratigraphic sequence or stratigraphic boundary. If the stratigraphic unit is layered, it is called a stratotype, whereas the stan ...

. As of 2017, a reference section for this unit has yet to be designated.

Paleofauna

Conodont Conodonts (Greek ''kōnos'', "cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, which ...
s

* ''

Cordylodus ''Cordylodus'' is an extinct genus of conodonts in the family of Cordylodontidae. Use in stratigraphy It is suggested that ''Cordylodus andresi'' can be a marker of the Cambrian Stage 10. Distribution Fossils of ''Cordylodus'' have been fo ...

'' : ''C. horridus'' * '' Hisiodella'' : ''H. holodentata'' * '' Leptochirognathus'' : ''L. quadratus'' * '' Paraprioniodus'' : ''P. costatus'' * ''

Periodon ''Periodon'' is a genus of conodonts which existed in what is now Canada, Iran, Argentina, China, Russia, and the United States during the Ordovician Period. It was described by Hadding in 1913, and the type species is ''P. aculeatus''. Species ...

'' : ''P. aculeatus'' * '' Spinodus''

Graptolites Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian (Miaolingian, Wuliuan) through the L ...

* '' Dichograptus'' * ''

Didymograptus ''Didymograptus'' is an extinct genus of graptolites with four rows of cups. They lived during the Middle Ordovician, to Late Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The ...

'' : ''D. euodes'' : ''D. manus'' : ''D. spinosus'' * '' Glossograptus'' : ''G. echinatus'' : ''G. horridus'' * ''

Phyllograptus ''Phyllograptus'' is a graptolite genus of the order Graptoloidea, in the family Phyllograptidae. Fossils of this genus have been found in the Early Ordovician (475-473 million years ago), in the sediments of Australia, Bolivia, Canada, Chile, ...

'' * ''

Tetragraptus ''Tetragraptus'' is an extinct genus of graptolites from the Ordovician period. Species * ''T. akzharensis'' * '' T. approximatus'' * '' T. fruticosus'' * ''T. insuetus'' Distribution Fossils of ''Tetragraptus'' have been found in Argentin ...

References

Ordovician geology of Oklahoma Ordovician Arkansas Ordovician southern paleotropical deposits {{US-geologic-formation-stub

Paleofauna

Conodont Conodonts (Greek ''kōnos'', "cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, which ...s

Graptolites Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian (Miaolingian, Wuliuan) through the L ...

See also

References

Conodont Conodonts (Greek ''kōnos'', "cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, which ...
s