Keywords: Square butte.jpg en Northwest view of Square Butte a laccolith in the Adel Mountains Volcanic Field in west-central Montana From Stephen S Harlan Lawrence W Snee Mitchell W Reynolds Harald H Mehnert R G Schmidt Steve D Sheriff and Anthony J Irving 40Ar/39Ar and K-Ar Geochronology and Tectonic Significance of the Upper Cretaceous Adel Mountain Volcanics and Spatially Associated Tertiary Igneous Rocks Northwestern Montana Professional Paper 1696 U S Department of the Interior U S Geological Survey Reston Virginia 2005 http //pubs usgs gov/pp/2005/1696/pdf/PP1696 pdf U S Geological Survey 2005 Volcanic landforms in Montana Cretaceous volcanism PD-USGov Laccolith Adel Mountains Volcanic Field |