Date of Award
Master of Science (MS)
F.D. Holland, Jr
The Deadwood formation includes all of the pre-Winnipeg sedimentary rocks of North Dakota which range in thickness from an erosional edge in the subsurface of northeastern North Dakota to at least 1,000 feet in northwestern North Dakota. It is composed of sandstone, shale, and carbonate of Late Cambrian to Early Crdovician age. Facies relationships are not entirely clear, but sedimentation appears to have been continuous from Late Cambrian to Early Crdovician in the Williston Basin. Conodonts from the upper part of the Deadwood formation in northwestern North Dakota are brownish-black, mostly simple cone types and suggest an Early Drdovician age for this part of the Deadwood formation in that area.
The Winnipeg formation consists of sandstone, shale, and siltstone which range in thickness from an erosional edge in the subsurface of southeastern North Dakota to maximum of 357 feet in northwestern North Dakota. The Winnipeg lies unconformably on the Deadwood formation except in northwestern North Dakota where it may rest conformably on the Deadwood formation and in northeastern North Dakota where it lies nonconformably on Precambrian rocks.
The Winnipeg formation is divided into three members which are, in ascending order: 1) Black Island member, composed of clean, quartzose sandstone; 2) Icebox member, composed of greenish gray, non-calcareous shale; and 3) Roughlock member, composed of calcareous siltstone, very fine grained sandstone, and shale. Condent faunes of the Winnipeg formation indicate those the Black Island member is probably Chasyan, the Icebox member is Blackriveran to lower Trentonian and the Roughlock member is Trentonian.
Carlson, Clarence G., "Stratigraphy of the Winnipeg and Deadwood Formations in North Dakota" (1960). Theses and Dissertations. 50.