Pelecypoda from the lower Fox Hills Formation (Upper Cretaceous) of Emmons County, North Dakota
Date of Award
Master of Science (MS)
F.D. Holland, Jr
The Fox Hills Formation in Emmons County, North Dakota, consists of 250-350 feet of medium to fine grained sand and sandstone with some shale interbeds. In Emmons County, the four members, Trail City, Timer Lake, Bullhead(?), and Colgate are not as distinct lithologically as they are in the areas from which they were described; thus, the unit has been subdivided into a lower part consisting of crossbedded sand and sandstone with calcareous, fossiliferous concretions and an upper part consisting of interbeds of buff sand and chocolate shale.
The gradational change from Pierre Shale lithology to the sands of the overlying Fox Hills Formation have resulted in several different definitions of the contact. The most consistent criterion for defining the contact in Emmons County is a zone of jaresite below the lowest fossiliferous concretion layer. The base of the jaresite zone has been arbitrarily selected as the division between the two formations.
Twenty-two species of pelecypoda were identified from the concretions of the lower part of the formation. The concretions were probably formed as clay boulders along the strand line of the Fox Hills Sea and were later transported to their site of deposition further offshore. The entire formation represents the shoreline and nearshore facies of the regressive Upper Cretaceous seaway.
Feldmann, Rodney M., "Pelecypoda from the lower Fox Hills Formation (Upper Cretaceous) of Emmons County, North Dakota" (1963). Theses and Dissertations. 90.