By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
The Kuskokwim region, which includes the country drained by the Kuskokwim River, is roughly 400 miles long and 75 to 100 miles wide extending from the mouth of the Kuskokwim River, in southwest Alaska, to the northwest slopes of the Alaska Range, in south-central Alaska. Important gold-producing districts are Georgetown, Goodnews Bay, McKinley, and Tuluksak-Aniak.
The area southwest of the town of Aniak is underlain predominantly by Quaternary sands and gravels, but the more mountainous regions east and northeast of Aniak are underlain by bedded rocks that range in age from Ordovician(?) to Tertiary (Cady and others, 1955, pi. 1). Only parts of the region have been geologically studied in any detail; much of it remains to be mapped.
The Kuskokwim River, particularly its lower reaches, was penetrated first by Russians who in 1829 began exploring the area and later established trading posts along the river (Cady and others, 1955, p. 3-4). The first report of gold in this region was by Spurr (1900, p. 259-261) who, in 1898, noted that gold was present both in veins and in stream gravels at various points along the Kuskokwim. These reports were of mere occurrences rather than of bonanza deposits; thus prospectors were reluctant to enter this relatively unknown region. It was not until 1908 that the first gold was produced (Smith, 1933, table facing p. 96). Placers have been the principal producers from this region, yielding substantially even in the 1950's. Production from 1908 through 1959 totaled 640,084 ounces, of which only 41,598 ounces was from lode mines.
The Georgetown district, between lat 62Â°00' and 62Â°15/ N. and long 157Â°15' and 158Â°15' W., includes the upper reaches of the George River and Crooked Creek, tributaries of the Kuskokwim River.
Production data are incomplete but they indicate that the district has produced somewhat less than $300,000 in gold (about 14,500 ounces), chiefly from placers along Donlin and Julian Creeks which, respectively, are branches of Crooked Creek and the George River (Cady and others, 1955, p. 117-119). The placers were known as early as 1909, and mining began about a year later (Cady and others, 1955, p. 118). This early production either was unrecorded or was combined with some other district, as 1917 is listed as the first year of production. No gold production was reported from this district from the end of World War II through 1959. The low gold content of the deposits required that large volumes of gravel be handledâ€”this was successfully accomplished by hydraulic methods.
The bedrock consists of interbedded graywacke and shale of the Kuskokwim Group of Cretaceous age into which sheets, dikes, and sills of albite rhyolite are intruded. Quartz veins containing small amounts of gold are at or near the contacts of the intrusives with the enclosing sedimentary rocks. These veins no doubt were the source of the gold in the placers (Cady and others, 1955, p. 116-117). Bench gravels, buried channels, and the deposits of existing streams contain concentrations of placer gold (Cady and others, 1955, p. 116).
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