Elk Basin is a valley on the border of Montana and Wyoming in the United States. It is an active oil field with hundreds of derricks operating in it. Geologically, it is a breached anticline formed by a deep subsurface thrust fault. Most of the rocks at the surface are Cretaceous in age, including the Lance Formation, Meeteetse Formation, Mesaverde Formation, Cody Shale, and Frontier Formation.^[1]

As the rock strata in the basin are mostly exposed and relatively easy to identify, Elk Basin has long been used as a place for geology students to learn to practice geologic mapping. Often mapping classes are supported by the Yellowstone Bighorn Research Association,^[2] located in Red Lodge, Montana.