The Du Noir area includes about 250 square miles in the northwestern part of the Wind River Basin, Fremont County, Wyoming. It is bounded on the south by the Wind River and Warm Spring Creek, which flow along the northeast flank of the Wind River Mountains, and on the north by the steep scarps of the southern margin of the Absaroka Mountains. Rugged mountainous terrain dominates both the southwest and northern portions of the mapped area while badland topography and deeply dissected upland surfaces characterize the central part. One of the most significant physiographic and structural features of the region is a belt of folded and faulted Paleozoic and Mesozoic rocks, referred to as the Washakie Range, which lies along the southern margin of the Absaroka Mountains. These highlands, attaining elevations of es much as 10,000 feet, were buried by Tertiary volcanic debris and subsequently partly exhumed as the Wind River Basin was reexcavated by Wind River and its tributaries.
The sedimentary rocks exposed in the Du Noir area are more than 12,500 feet thick and range in age from Cambrian to Recent. All systems, with the exception of the Silurian, are represented. Precambrian granite and granite gneiss are present in both the Wind River and Washakie Ranges.
