Date of Award
Doctor of Philosophy (PhD)
This paper is a discussion of the surface stratigraphy and petrology of the Hell Creek Formation in North Dakota and eastern Montana. Principal area of study included the Missouri Valley south of Bismarck, North Dakota; the Little Missouri Valley in Slope and Bowman Counties, southwestern North Dakota; the Yellowstone Valley near Glendive, Dawson County, Montana; and the type area of the Hell Creek Formation on Hell Creek and East Hell Creek, Garfield County, Montana on the south shore of the Fort Peck Reservoir.
Two and one-half summers were spent in the field measuring 72 stratigraphic sections, correlating between the measured sections, collecting petrographic samples and fossils from the Hell Creek Formation and associated formations. Laboratory studies included heavy mineral analyses, preparation and study of petrographic thin sections, and the identification of the fossils collected.
The Hell Creek Formation was found to be divisible into 8 members, 7 of which are new. In central North Dakota (from oldest to youngest) the Crowgheat Member, the Breien Member (named prior to this paper), the Fort Rice Member, the Guff Member, and the Pretty Butte Member were recognized. In southwestern North Dakota (from oldest to youngest) the Little Beaver Creek Member, the Marmarth Member, the Bacon Creek Member, the Huff Member and the Pretty Butte Member were defined. In eastern Montana a set of sandstones at the base of the formation was recognized as a possible ninth member but was not named. The Pretty Butte and Huff Members appear to be present over all of western and central North Dakota as well as eastern Montana. The other members have only local importance.
The top of the Hell Creek Formation is considered a time line as a result of the studies of the fossils (particularly dinosaurs) and bentonites. The base of the Hell Creek Formation was found to become progressively younger in an eastward direction. No conformity was found at the top of the formation. The base of the formation was found to be vertically and horizontally gradational with the Fox Hills Sandstone in the east and to lie unconformably upon the Fox Hills Sandstone in the west.
The Hell Creek Formation may be visualized as the subaerial top-set beds of a giant delta stretching eastward from the Rocky Mountain Point into the Fox Hills-Cannonball Sea at the close of the Cretaceous time. Laterally equivalent marine top-set beds of this delta are the Fox Hills Formation. Fore-set and bottom-set beds are represented by the Pierre Shale.
The climate during Hell Creek times in North Dakota was warm, temperate, summer-moist with probably no frosts as indicated by such plants as Metasequoia, Cercidiphyllum, Ficus, and Magnolia, and by such animals as dinosaurs, crocodiles, and alligators. The early Paleocene climate appears to have changed little if any from the preceding Hell Creek climate since there is a continuation of such plant genera as Cercidiphyllum and Metasequoia and such animals as crocodiles, into the Cenozoic Era.
Frye, Charles I., "The Hell Creek Formation in North Dakota" (1967). Theses and Dissertations. 101.