Bedrock geologic map of the Big Hurrah-Council-Bluff area, Southern Seward Peninsula, Alaska

Bedrock geologic map of the Big Hurrah-Council-Bluff area, Southern Seward Peninsula, Alaska, Report of Investigation 2024-7, presents bedrock geologic mapping from the blueschist-facies-metamorphosed, Late Proterozoic to Devonian Nome Complex was conducted by the Alaska Division of Geological & Geophysical Surveys (DGGS) on southern Seward Peninsula, Alaska. This map, covering portions of the Solomon C-4, C-5, D-4, D-5, and the southern Bendeleben A-4 quadrangles, includes new mapping by DGGS in the summer of 2006 and incorporates previous mapping conducted by DGGS in 2003 and 2004. Surficial geologic mapping was also conducted in the area. This 595-square-mile, 1:50,000-scale, bedrock geologic map coincides with portions of the DGGS Council airborne magnetic and resistivity survey. The geophysical survey and geologic map are part of the State of Alaska's Airborne Geophysical/Geological Mineral Inventory program, focusing on enhancing public knowledge of Alaska's geology and mineral districts. More than 1 million ounces of placer gold have been extracted from the map area since the turn of the century, with most production derived from the Casadepaga and Solomon rivers and Ophir Creek. Widespread low-sulfide, gold-bearing quartz veins of Cretaceous age were the primary lode source for the placer gold. Approximately 27,000 ounces of gold were produced from low-sulfide quartz veins at the Big Hurrah lode gold mine between 1903 and 1907. Other notable lode gold prospects in the map area include Silver (Flynn), West Creek, and an unnamed prospect at the head of Albion Creek. The Bluff area along Norton Sound has both lode gold and mercury prospects. The map area contains numerous occurrences of silicified marble with anomalous geochemistry of uncertain age and genetic origin. Various lithologies of the Layered sequence subdivision of the Nome Complex, primarily the Mixed unit, have the potential to host sedimentary exhalative (SEDEX) mineralization of Late Devonian to possibly Mississippian(?) age, as found elsewhere on the Seward Peninsula. The complete report, geodatabase, and ESRI fonts and style files are available from the Alaska Division of Geological & Geophysical Surveys website: http://doi.org/10.14509/31308.

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Organization: State of Alaska