The unit records the gradual opening and expansion of the Greenhorn Cycle of the Western Interior Seaway, and as such is lithologically identical to the Graneros Shale Formation (that is, it is the same formation under a different name).[2]
^"Geologic Unit: Belle Fourche". National Geologic Database. Geolex — Unit Summary. United States Geological Survey. Retrieved 2018-06-29.
^Donald E. Hattin (1965). "KGS--Graneros Shale in Central Kansas--Stratigraphy". Kansas Geological Survey Bulletin (178). Kansas Geological Survey: Stratigraphy / Graneros Shale / Name and Definition. Retrieved September 6, 2021. The lithologic equivalent of the Graneros in the Black Hills and surrounding areas is the Belle Fourche Shale. Considerable similarity exists between these two formations, and, if the name Graneros is to be perpetuated in the Black Hills region, it would be best used to replace the name Belle Fourche over which the former has priority.