1. Thickness, percent sand, and configuration of shallow hydrogeologic units in the Powder River Basin, Montana and Wyoming [cartographic material] Yale Public content 1981. 2015-07-01T20:16:57Z. 2015-07-14T22:10:28Z. Lewis, Barney D. U.S. Geological Survey. English. cartographic image. Public. Powder River Basin (Wyo. and Mont.).