1. Map showing sand and gravel deposits in the Bigfork-Avon area, Flathead, Lake, Lewis and Clark, Missoula, and Powell counties, Montana Yale Public content 1995. 2002-06-01T04:00:00Z. 2002-06-01T04:00:00Z. Geological Survey (U.S.). The Survey ; U.S. Geological Survey Information Services [distributor]. English. Public. Montana, Avon Region, and Bigfork Region.