|The Cretaceous Pierre Shale Formation is
found in numerous areas of Colorado and other western states.
Paleocurrents.com has pages devoted to the Pierre Shale exposed
at Baculite Mesa near Pueblo, CO (east of mountains at 5000 feet - 1524
meters). However, the following covers fossils found in the
Pierre Shale of the Colorado mountains near Kremmling, CO (7900 feet - 2400 meters). The Bureau of Land Management (BLM) has designated a site as a Research Natural Area
(RNA) which is off-limits to collecting of any kind. Within the
RNA, there are remains of giant ammonites measuring 2-3 feet (61-91 cm)
in diameter. The actual specimens have been removed and reside in
museums such as the Denver Museum of Nature & Science.
The fossils shown below, including the image link, were all collected outside the BLM RNA site. The BLM has plans to incorporate more of this land into the RNA, but it is presently open to collecting under the laws governing the BLM.
Ammonite, Jeletzkytes nodosus, male
Ammonite, Jeletzkytes nodosus
Ammonite, Placenticeras costatum
I haven't identified all the fossils you will see in the Images link below. If you notice any errors in identification, please contact Steve Wagner.
Notes & References:
(1) Ammonites and the Other Cephalopods of the Pierre Seaway, by Neal L. Larson, Steven D. Jorgenson, Robert A. Farrar, and Peter L. Larson (Geoscience Press, Tucson, AZ, 1997).