Stratigraphic framework of coal beds underlying the northeastern part of the Fort Peck Indian Reservation, Montana

The area of investigation is located in the northeast part of the Fort Peck Indian Reservation (fig. 1) on the western flank of the Williston Basin.  It covers about 450 square miles and is made up of parts of Daniels, Sheridan, and Roosevelt counties.  Exploratory drilling for coal and logging of seismograph drill holes in 1978-1981 were done with the support of the Branch of Indian Affairs as part of the U.S. Geological Survey's program to assess coal resources in the reservation (Hardie and Arndt, 1981; Ardnt, Hardie, and Kehn, 1982).  From the data generated, selected seismic and coal exploration logs were used in this report to show the stratigraphic framework of lower Fort Union coal beds (fig. 3) and local variations (fig. 2) with particular reference to the Timber Coulee coal zone.