75 million years ago, the Choteau-Augusta area was part of a broad coastal plain. The nascent Rocky Mountains lay to the west, and the eastern part of the plain was bounded by the Interior Seaway.
Originally uploaded in Integrating Research and Education:Montana Geoheritage Project:Montana-Yellowstone Geologic Field Guide Database.
Image 179436 is a 953 by 1418 pixel JPEG
Uploaded: Mar5 18