Date of Award
Master of Arts (MA)
F.D. Holland, Jr
More than 1500 thin-sections from 73 wells in the North Dakota part of the Williston Basin were searched for their foraminiferal content. This thin-section survey of the Bottineau, Tilston, Frobisher-Alida, and Ratcliffe intervals yielded more than 700 identifiable foraminifers assigned to 26 species.
Most of the Madison foraminifers of the Williston Basin can be placed in one of two superfamilies, the Tournayellac1a and the Endothyracea. The Bottineau and T11ston intervals yielded more specimens from the superfamily Tournayellacea while the Frobisher-Alida and Ratcliffe intervals yielded more specimens from the superfamily Endothyracea.
The foraminifers occurred in irregular stratigraphic zones The Bottineau and Tilston intervals each had two zones of foraminiferal occurrences. The foraminifers of these intervals were found only in the north-central part of North Dakota in Bott1neau, Renville, and Pierce counties. The lower one-half of the Frobisher-Alida interval yielded no identifiable foraminifers. With the exception of NDGS well 4097 in Ward county, all identifiable foraminifers were found along the Nesson anticline. The Ratcliffe interval yielded foraminifers from the lower one-half of the interval and had a greater geographic distribution than any of the other intervals
Mississippian foraminifers from the North Dakota part of the Williston Basin were applied to the biozonation scheme of Mamet and Skipp. Foraminifers found in the Bottineau interval are characteristic of Biozone 7 and are of early Osagean age. Foraminifers found in the Tilston interval are characteristic of Biozone 8 and are middle Osagean in age. Biozone 9 was not recognized in the North Dakota part of the Williston Basin. The upper one-half of the Frobisher-Alida interval and the lower part of the Ratcliffe interval contain foraminifers from Biozone 10 that is earliest Meramecian in age. Biozone 11 was not recognized in this study but may exist because some of the species found in the Ratcliffe interval may belong to either Biozone 10 or Biozone 11.
The Mississippian foraminiferal fauna in North Dakota has many similarities with faunas from the Mississippian rocks of the Western Cordillera. It is often less diverse than those faunas reported from the western United States and Canada but is useful for biostratigraphic zonation.
Eylands, Kurt E., "Foraminiferida of the Madison Group (Mississippian) of the Williston Basin, North Dakota" (1989). Theses and Dissertations. 85.