The Minturn Formation is a geologic formation in Colorado. It preserves fossils dating back to the Carboniferous period. Among the fossils preserved are of crinoids, spiriferid brachiopods, gastropods, and the spines and teeth of numerous sharks such as Petalodus

• http://en.wikipedia.org/wiki/Minturn Formation
• Page 174 - Barkmann, P. E., et al., 2016, South Park, Colorado: The interplay of tectonics and sedimentation creates one of Colorado's crown jewels: Geol. Socd Guide 44, p. 151-190.