Deadwood Formation

Deadwood Formation Stratigraphic range: Late Cambrian to Early Ordovician PreЄ Є O S D C P T J K Pg N
The Deadwood Formation at Fallingrock cliff in Dark Canyon in the Black Hills, South Dakota.
Type	Formation
Underlies	Red River Formation, Winnipeg Formation, Englewood Formation, or Elk Point Group
Overlies	Precambrian rocks, or Earlie and Pika Formations
Lithology
Primary	Sandstone
Other	Conglomerate, shale, limestone
Location
Region	Williston Basin and Western Canada Sedimentary Basin
Country	United States  Canada
Type section
Named for	Deadwood, South Dakota
Named by	Darton, N.H. and Paige, S. (1925)

The Deadwood Formation is a geologic formation of the Williston Basin and Western Canada Sedimentary Basin. It is present in parts of North and South Dakota and Montana in the United States, and in parts of Alberta, Saskatchewan, and southwestern corner of Manitoba in Canada. It is of Late Cambrian to Early Ordovician age and was named for exposures in Whitewood Creek near Deadwood, South Dakota. It is a significant aquifer in some areas, and its conglomerates yielded significant quantities of gold in the Black Hills of South Dakota.

It preserves trace fossils such as Skolithos, and remains of Late Cambrian trilobites and brachiopods, as well as Ordovician fossils.

At the type locality in the Black Hills of South Dakota and in many other areas, the Deadwood Formation rests unconformably on Precambrian metamorphic rocks that were exposed to a long period of erosion prior to the deposition of the formation. In western Montana, western Saskatchewan and Alberta it overlies the Middle Cambrian rocks of the Earlie Formation or the Pika Formation.