Navy Oil Unit Party 4, during the summer field season of 1949, examined the surface geology of the area of the Okpikruak and Kiruktagiak Rivers. The party consisted of six men: two geologists, two field assistants, a weasel mechanic, and a cook. Three weasels were used for transportation in the field.
The area covered is bounded on the west by the Okpikruak River, on the east by the Chandler River, and on the south by the north front of the Brooks Range. Tuktu Bluff on the Chandler River and its westward extension forms the northern boundary. The area is drained by the Chandler, Kiruktagiak, Ayiyak, Okokmilaga, and Okpikruak Rivers.
The objectives of this summer's work was the geologic mapping and stratigraphic study of the rocks that crop out in this area. All outcrops were visited and the geology was plotted on vertical and trimetrogon oblique aerial photographs. Altitudes were established by an altimeter traverse.
Parts of this area had been investigated previously by members of the Navy Oil Unit. During the summer of 1945 George Gryc, E. J. Webber, and Karl Stefansson visited outcrops along the. Chandler and Kiruktagiak Rivers and in the vicinity of Castle Mountain.
In the same year L. A. Warner and C. E. Kirschner examined outcrops along the Okpikruak River in conjunction with their survey of the Klink and Colville Rivers. R. L. Detterman included detailed stratigraphic studies of cutbanks near the confluence of the Kiruktagiak and Chandler Rivers in his geological mapping of the lower Chandler during the summer of 1948.
