Spearfish Formation

Unit Name: Spearfish Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Permian - Triassic (299 - 199.6 ma)
Province/Territory: Montana; Nebraska; North Dakota; South Dakota; Wyoming

Originator: Darton, N.H., 1899.

Type Locality:

Spearfish, South Dakota, on the northern flank of the Black Hills of south Dakota and Wyoming.

Distribution:

The red-bed facies comprising this formation is continuous from Wyoming, where it is equated with the Chugwater Formation, northeast into the Williston Basin of North Dakota, Saskatchewan and Manitoba. However, only the upper portion may be present in Canada, represented by the lower members of the Watrous and Amaranth formations. Thickness of the Spearfish ranges from more than 260 m (886 ft) in northeastern Wyoming to 225 m (738 ft) in North Dakota to less than 100 m (328 ft) in Saskatchewan and Manitoba.

Lithology:

In the type region consists of red shale, siltstone and sandstone, with thick beds of gypsum near the base. Rests with sharp contact on the Permian Minnekahta Limestone and is overlain unconformably by the Jurassic Sundance Formation. In the subsurface of the Williston Basin of North Dakota the formation is divided into 3 members: the Belfield, Pine Salt and Saude.

Relationship:

Unconformably overlies beds ranging from the Middle Permian in Wyoming to Mississippian and Upper Devonian in Saskatchewan. The name Spearfish has not come into general usage in Canada.

Other Citations:

Bluemle, Anderson and Carlson, 1981; Darton, 1899; Francis, 1956; McLachlan, 1972; Robinson, Mapel and Bergendahl, 1964.

References:

Darton, N.H., 1899. Jurassic formations of the Black Hills of SOuth Dakota: Geological Society of America Bulletin, v. 10, p. 383-396.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: J.E. Christopher
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 06 Apr 2009