Contact (red arrow) between the underlying marine shales of the Bearpaw Formation and the coastal Horseshoe Canyon Formation.
A ridge capped by a sandstone bed of the Fox Hills Formation west of Limon, Colorado
Bearpaw shale being excavated to recover ammonites for ammolite production.
A specimen of Placenticeras ammolite from the Bearpaw Formation.

In its eastern extents, the formation is underlain by the marine Pierre Shale in the United States and by the equivalent Bearpaw Formation in Canada, while in western ranges in Montana and Wyoming it overlies the Lewis Shale.

- Fox Hills Formation

It is overlain by the Horseshoe Canyon Formation in central Alberta; by the Blood Reserve Formation and the St. Mary River Formation in southern Alberta; by the Eastend Formation in southern Saskatchewan; and by the Fox Hills Formation in Montana.

- Bearpaw Formation
Contact (red arrow) between the underlying marine shales of the Bearpaw Formation and the coastal Horseshoe Canyon Formation.

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A broken concretion with fossils inside; Late Cretaceous Pierre Shale near Ekalaka, Montana

Pierre Shale

Geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from Pembina Valley in Canada to New Mexico.

Geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from Pembina Valley in Canada to New Mexico.

A broken concretion with fossils inside; Late Cretaceous Pierre Shale near Ekalaka, Montana

It is correlative with other marine shales that occur farther west, such as the Bearpaw Shale, Mancos Shale and the Lewis Shale.

The Pierre is overlain by marginal marine deposits of the Fox Hills Formation.