Name applied in this report to a dove-gray claystone near the top of the Van Bibber shale member (new), upper member of South Platte formation (new), upper formation of Dakota group. Considered to be an informal name for a local bed in the Van Bibber, and not known outside of Douglas Co., CO Denver basin. The Helmer is distinctive, subconchoidal to blocky fracture and can vary from silty claystone to flint clay. Is of commercial grade and thickness (8-10 ft) in the Helmer Mine (source of geographic name) where it overlies and underlies unnamed sandstones of the Van Bibber. Section in Helmer Mine in center of W-1/2, E-1/2, SW-1/4 sec. 13, T7S, R69W, Kassler quad measured [but no type designated]. Columnar section and geologic map show Van Bibber and South Platte respectively, but not the Helmer. Cretaceous age.

Source: GNU records (USGS DDS-6; Denver GNULEX).