Blakely Sandstone

The Blakely Sandstone is a Middle Ordovician geologic formation in the Ouachita Mountains of Arkansas and Oklahoma. First described in 1892,[3] 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 meeting,[4] but later redefined and renamed the unit as the Ouachita Shale.[5] He again renamed the unit to the Blakely Sandstone in a letter to Edward Oscar Ulrich, to which Ulrich used in a 1911 publication, becoming the first reference using this name.[2] Ulrich assigned the Blakely Mountain in Garland County, Arkansas as the type locality, but did not designate a stratotype. As of 2017, a reference section for this unit has yet to be designated.

Blakely Sandstone Stratigraphic range: Ordovician
Blakely Sandstone (Coleman Quartz Mine, Arkansas)
Type	Formation
Unit of	none
Sub-units	none
Underlies	Womble Shale
Overlies	Mazarn Shale
Thickness	up to 700 feet[1]
Lithology
Primary	Sandstone
Location
Region	Arkansas, Oklahoma
Country	United States
Type section
Named for	Blakely Mountain, Garland County, Arkansas
Named by	Albert Homer Purdue[2]