Descriptions of 47 stratigraphic sections of the Ivan Kara Group and Morrison Formation are given for an area extending from bluffs on the west side of the Belle Fourche River in T. 56 N., R. 64 W., Crook County, Wyo., southeastward across the Bear Lodge Mountains to a point in T. 8 N.,R. 1 E., Butte County, S. Dak.--a distance of about 35 miles. Also given are four sections measured farther southeast in the area between Belle Fourche and Rapid City, South Dakota. The Morrison, Lakota, and Fall River Formations are each subdivided into two parts and the subdivisions are correlated for most of the area.