1. Sedimentologic and stratigraphic framework of the upper part of the Fort Union Formation, western Powder River Basin, Wyoming Yale Public content 1987. 2002-06-01T04:00:00Z. 2002-06-01T04:00:00Z. Geological Survey (U.S.). The Survey ; For sale by Branch of Distribution. English. Public. Powder River Watershed (Wyo. and Mont.). Tertiary.