Geology,

“The drainage basin of the Tubutulik River is underlain by a large variety of rock types. The most significant feature, however, is a wide belt of granite along the western side of the area that is a continuation of the granite belt crossing the Kwiniuk River to the south. Of a total of 114 concentrates (samples 2966-2990, 2992-2998, and 3000-3002, 33004, 3081_ 41 contain between 0.01 and 0.02 percent equivalent uranium and 34 contain more than 0.02 percent equivalent uranium up to a maximum of about 0.1 percent equivalent uranium. The radioactivity of the concentrates from the Tubutulik River and its tributaries is confined entirely to samples in which at least part of the original material concentrated was derived from granitic rocks. In general, the equivalent uranium content of the concentrates increases as the streams are ascended to and within the granite.”

West, W.S., 1953, Reconnaissance for radioactive deposits in the Darby Mountains, Seward Peninsula, Alaska, 1948: U.S. Geological Survey Circular 300, 7 p.