The Bureau of Mines is conducting a 4-year (1987-90) study to assess the mineral resources and mineral development potential of the Valdez Creek Mining District in south-central Alaska. This study is part of the Bureau's ongoing statewide mining district evaluation program. This report summarizes the Bureau's site-specific evaluations of two areas (Tyone and Peters Creek) of the district that were investigated to determine the bedrock sources of gold and PGM in the alluvial gravel of both areas. In the Tyone Creek area, grains of gold (up to 0.0212 Oz/yd3) and platinum-group minerals (PGM) were recovered from alluvium and weathered conglomerate of the Jurassic Naknek Formation and Tertiary age conglomerate using placer sampling techniques. Platinum and palladium were detected in the heavy mineral concentrates recovered from placer sampling the alluvium and the Naknek Formation and Tertiary conglomerates. In the Peters Creek area, grains of gold (up to 0.014 Oz/yd3) were recovered from the alluvium and Tertiary Sterling Formation conglomerate. The Bureau's evaluations indicated that drainage basins containing conglomerate are the most favorable targets for placer gold and PGM exploration, and that Tertiary conglomerate represents a high-volume, low-grade gold resource.