Jackfork Sandstone

The Jackfork Sandstone, also referred to as the Jackfork Group, is a geologic formation associated with the Ouachita Fold and Thrust Belt exposed in western Arkansas and southeastern Oklahoma.[2] It is named for Jackfork Mountain in Pittsburg and Pushmataha counties, Oklahoma.[2][3]

Jackfork Sandstone
Stratigraphic range: Pennsylvanian
Quartz from the Jackfork Sandstone
Type	Formation
Underlies	Johns Valley Shale
Overlies	Stanley Shale
Thickness	3,500 to 6,000 feet
Lithology
Primary	Sandstone
Other	Shale, conglomerate
Location
Region	Ouachita Mountains
Country	United States
Type section
Named for	Jackfork Mountain, Pittsburg and Pushmataha Counties, Oklahoma[1]
Named by	J. A. Taff, 1902

The Jackfork Sandstone is a thin- to massive-bedded, fine- to coarse-grained, brown, tan, or gray quartzitic sandstone with subordinate brown, silty sandstone and dark gray shale.[2] It outcrops from Pulaski County, Arkansas in the east to Atoka County, Oklahoma in the west, a distance of over 200 miles. It is highly weather-resistant, resulting in a continuous chain of prominent ridges, including Rich Mountain, the second highest natural point in the Ouachita Mountains.