Type Locality:

Whitewood Creek, below Deadwood, South Dakota.

Distribution:

The Deadwood ranges from 1 m (3 ft) in the southern Black Hills of South Dakota to 150 m (492 ft) in the northern Black Hills to 270 m (886 ft) in the centre of the Williston Basin in North Dakota. It thins to zero eastwards, being absent in northeastern North Dakota and most of eastern Saskatchewan. It is present in the extreme southwestern corner of Manitoba, where it may reach 30 m (98 ft). Westwards it extends with general thickening throughout Saskatchewan and Montana to the Saskatchewan-Alberta border, where it exceeds 300 m (984 ft). Beyond it thins towards the mountain front. In the north the formation reaches almost to 55 deg N.

Lithology:

In the type area, according to Butler et al. (1955) the Deadwood consists of a basal conglomerate and buff sandstone 9 m (30 ft) thick, overlain by grey-green, thin bedded shale with limestone interbeds 79 m (260 ft) thick and topped by red-brown, very glauconitic quartz sandstone, usually thin-bedded, with random partings of green shale and Scolithos borings 40 m (130 ft) thick, for a total thickness of approximately 128 m (420 ft). In the centre of the Williston Basin Lefever et al. (1987) reported a thickness of more than 270 m (886 ft), recognized six members and described the formation as follows: "... largely of siliciclastic rocks, principally quartz arenites, quartz wackes, and siltstones, and lesser amounts of carbonate rocks, with textures from mudstones to grainstones."

Relationship:

At the type locality and throughout the Williston Basin the Deadwood Formation unconformably overlies Precambrian basement. In western Saskatchewan, western Montana and Alberta it overlies Middle Cambrian rocks of the Earlie Formation or of the Pika Formation (where that formation can be identified). In the Williston basin area the formation is overlain centrally by the Winnipeg Formation, and peripherally by the Red River Formation. In the type area the Ordovician Whitewood Formation (Red River) overlies it; in the central and Southern Black Hills it is overlain by the Mississippian Englewood Formation. In Alberta it is overlain by Devonian strata of the Elk Point Group.

History:

Darton (1901) first used the term without formal definition, as Jaggar (1901) had been expected to describe the type section.

Other Citations:

Butler et al., 1955; Carlson, 1960; Darton, 1901; Darton and Paige, 1925; Jaggar, 1901; Lefever et al., 1987; Paterson, 1988.