Kremmling, CO - Sept, 2005
Marine Invertebrate Fossils
 of the Pierre Shale Formation, Colorado

The Cretaceous Pierre Shale Formation is found in numerous areas of Colorado and other western states. 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

Inoceramus clam

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).
[Created 09/12/2005]
[Last Updated: 9/25/2005]