Abstract

Tertiary continental sedimentary rocks of the Kootznahoo Formation are a potential host for uranium in the southern part of the Admiralty trough in southeastern Alaska. An outcrop area on the southwest coast of Zarembo Island and one at California Bay on the north coast of Prince of Wales Island were studied for this report. In these areas, the Kootznahoo consists of arkose, arkosic conglomerate, siltstone, mudstone, and coal. Some of the conglomerate and sandstone contains carbonaceous fragments that may have provided a chemically reducing environment enabling the precipitation of uranium. Slight epigenetic enrichment was found in outcrops of conglomerate, sandstone, and coal. Sandstone contained as much as 17.7 parts per million uranium, and coal contained as much as 27.7 parts per million. A uranium source was not identified, but rhyolitic and dacitic intrusive and extrusive rocks and alkaline granite in the area are anomalously high in uranium. No significant airborne radioactive anomalies have been found in the area.