Exploring Montana’s Rocky Mountain Front

STORY AND PHOTOS BY AMY GRISAK

Wagner Basin looking toward the Bob Marshall.

Kids love anything that looks like seashells even if they have to climb thousands of feet to find them.

Frankly, adults do too! Spotting the distinct fossil of a horned clam or brachiopod during a nature hike makes trudging uphill worth the effort. And while it’s enjoyable to simply find them, delving into how they formed adds a new layer of delight.

Six years ago, Bill Hansen, a friend and geologist, opened my eyes to the geological wonderment of the Rocky Mountain front in Central Montana as he led my kids on a school field trip. I have since visited the area numerous times. This region, particularly on the plains just beyond the mountains, is well-known in paleontological circles as where Maiasaura peeblesorum, the “good mother lizard,” was discovered by Marion Branvold, owner of the Trex Agate Shop in Bynum in 1977. After she showed her finds to paleontologist Jack Horner the following year, he and his team discovered multiple nests and specimens, ultimately naming the area “Egg Mountain.” While evidence of dinosaurs remains within the Two Medicine Formation stretching onto the plains, the mountains hold older treasures.

Sea creatures in the area originated up to 350-million years ago when a shallow tropical ocean covered this entire region…it was a vastly different world during this time. The North American plate was slightly south of the equator and Montana was a warm, humid environment.”