Museum volunteers digging for ammonites

Popping the concretion exposes the top half of the ammonite.

Ammonite with top and bottom halves of concretion
Ammonites: Click to enlarge
Stubborn ammonite being pried up; loaded truck bound for the Museum
After hearing the characteristic clink of the metal probe against a hard rock, the DMNS crew digs and brushes away the overlying sediment to expose a giant concretion. The fossil site near Kremmling occupies a gently sloping hill covered with sagebrush. Many of the concretions here are shallowly buried, so exposing one can be done in as little as 15 minutes.

Giant ammonites cause planes of weakness inside the concretions, and yearly freezing and thawing cycles cause cracks to form along these planes. All this makes the excavation process easier; a gentle tap with the crowbar is often all it takes to split apart the concretion and lift off the top like a manhole cover. But these ammonites are heavy, and getting them out of the ground is no small job. When the ammonite doesn't easily separate from the lower half of the concretion, the DMNS crew must pry up the entire nodule with crowbars.

In the August 1998 dig, Kirk Johnson, Emmett Evanoff, and Ray Troll were able to collect a dozen of these spectacular fossils. The DMNS crew carried the precious cargo to Big Blue, the Museum's premier fossil-collecting truck, and returned them to the Museum.


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