U. S. Geological Survey Navy Oil Unit Party I examined the surface geology of the area of the upper Utukok River and east fork of the Kokolik River from June 28 to September 3, 1950. The party consisted of six men: E. G. Sable and M. D. Mangus, geologists; C. L. Hummel and F. H. Shannon, field assistants; R. D. Gerard, cook; and L. E. Hall, weasel mechanic. Three weasels were used for transportation in the field.
The area examined approximates 1,000 square miles and is in the extreme southwest corner of Naval Petroleum Reserve No. 4. It is bounded on the west by Iligluruk Creek (east fork of the Kokolik) and on the east by Driftwood Creek. With the exception of Driftwood Creek, major streams were ascended to their headwaters in the De Long Mountains. A traverse southward over the Utukok-Kugururok Rivers divide was successfully completed, providing a "tie-in" with the work of Navy Oil Unit Party 7. Several traverses were made 8 miles north of the Driftwood anticline and to the west fork of the Colville River.
The objectives of this part of the summer's work were (1) the geologic mapping and stratigraphic study of the rocks exposed in this area, and (2) measurement of stratigraphic thicknesses of sediments older than those exposed in the Driftwood anticline. Geology was plotted on vertical and trimetrogon oblique aerial photographs. Altitudes were established by altimeter traverses.
The northern part of this area was previously investigated by members of the Navy Oil Unit. In 1947 R. M. Thompson and W. L. Barksdale1/ visited outcrops along the Utukok River, and in 1949 R. M. Chapman and E. G. Sable2/ examined exposures along the Kokolik River. (See fig. 1, index map.)
