In the foothills there are typical canyons, as along the Platte forks, and in the northern edge of the sand-hills Those of the upper Republican are the largest, those of the Bad Lands are the most peculiar; and the Niobrara tributary system is the most developed.
The upper course of the Niobrara above the Keya Paha is in a narrow gorge.
At Niobrara, in Knox county, a well 656 ft.
Its groups include the Dakota formation, characterized by a very peculiar rusty sandstone, and the Benton, both of which are rather widely accessible and heavy; the Niobrara; the Pierre shales, which apparently underlie about three-quarters of the state in a deep and heavy bed; and, in the extreme west, the Laramie.
There are almost no Cretaceous outcrops except on the streams, especially the Niobrara, Republican and Platte rivers - and in the Bad Lands.