Date of Award
Master of Science (MS)
The Hell Creek Formation (Upper Cretaceous) in southwestern North Dakota consists of lagoonal and floodplain deposits and contains abundant concretions and nodules. Representative specimens of the concretions and nodules and their corresponding enclosing sediments were analyzed by thin section and by quantitative and qualitative x-ray diffraction methods.
Fourteen types of concretions and three types of nodules, classified according to shape and composition, have thus been defined. Concretionary types include calcareous sandstone lenses, “logs”, and irregular masses; sideritic sandstone lenses and irregular masses; calcareous and sideritic lignitic sandstone lenses; bone-cored rounded masses; coprolite-cored masses; jarosite bodies; pyrite spheres; baritic sandstone lenses; and cone-in-cone masses. The nodular types include siderite masses and lenses and iron oxide spheres. Moving groundwater solutions, in many cases acccmpanied by locally reducing conditions resulting from the accumulation of organic materials, have apparently been important factors in the formation of many of the concretionary bodies. Precipitation and dewatering of gels is the most probable mechanism responsible for the formation of the various types of nodules.
Groenwold, Gerald H., "Concretions and nodules in the Hell Creek Formation, southwestern North Dakota" (1971). Theses and Dissertations. 112.