Date of Award
Bachelor of Science (BS)
Dr. Nels Forsman
Volcanic tuffs of Cretaceous age are found sandwiched in many outcrops in southwestern North Dakota. The lateral extent of many of these tuffs has been mapped, but distinguishing discrete tuffs is a work in progress. This report looks at two tuffs found along the Cannonball River south of Bismarck.
The Breien Tuff was collected in southeastern Morton County and the Cannonball Tuff was collected in northwestern Sioux County, but research had not yet been done to determine whether these two tuffs are distinct, or if one is merely an extension of the other. The proximity of the two sample sites allows the possibility that the Breien Tuff may be an extension of the Cannonball Tuff.
In order to distinguish the tuffs multiple comparative and analytical tests must be performed on both tuffs. Conclusions were made about the possible distinction or correlation of the Cannonball and Breien Tuffs using grain size analysis, x-ray diffraction, magnetic separation, and grain mount petrographic analysis.
The Breien and Cannonball Tuffs have few different properties when examined by the unaided eye. By the methods available for this research, insufficient evidence was found to show that the Cannonball Tuff and Breien Tuff were from the same depositional episode. However, further analytical tests of the two tuffs could determine the distinctness of these two tuffs. Scanning electron microscopy, as well as trace element and glass grain chemical analysis are some methods that could further the fingerprinting of these tuffs.
Worden, Anna K., "Comparison of Breien and Canonball Volcanic Tuffs in Southern North Dakota" (2007). Undergraduate Theses and Senior Projects. 95.