Date of Award
Bachelor of Science (BS)
Dr. John R. Reid
Concretions occur as fairly continuous horizons in the Trail City Member of the Fox Hills Formation. These horizons are used as stratigraphic markers for correlation of the formation.
Two general types of concretions are found. The first is sandstone which occurs either as spherical or lenticular shaped forms. The other type has a hard blue-gray limestone core and is usually spherical in shape. Although both types may contain fossils, the unfossiliferous concretion is more abundant.
The concretions were formed either by accretion of material from the sediment, and from connate and ground waters; or by rolling, in the same manner as an armored mud ball form.
Mathison, David J., "Corrections from the Fox Hills Formation Trail City Member" (1964). Undergraduate Theses and Senior Projects. 47.