The region is classified as a single mining district.
The region is dominated by the Aleutian Range, a series of northeast-trending ridges 1,000—4,000 feet in altitude surmounted locally by volcanoes up to 9,372 feet high. Northwestward, the range merges with a low sand- and gravel-mantled plain that has local relief of 50—250 feet.
Geologically, the Alaska Peninsula region consists of two main belts that extend for most of its length. The northwestern belt is as much as 35 miles wide near the Ugashik Lakes but is absent on the western end of Unimak Island; it is predominantly uncon¬solidated Quaternary silt, sand, and gravel. The southeastern belt is made up mainly of Mesozoic and Cenozoic sedimentary and volcanic rocks and Tertiary granitic plutons (Burk, 1965). A single exposure of Permian sedimentary rocks is near Puale Bay (Hanson, 1957); some of the volcanic rocks also may be of Per¬mian age. The entire Alaska Peninsula was glaciated during the Pleistocene Epoch but is now ice free except for some of the high¬est peaks. The region is generally free of permafrost. Several of the volcanoes that surmount the Aleutian Range have been active within the past few years.
Lodes in the Alaska Peninsula region (Berg and Cobb, 1967, p. 5—7, fig. 1; Cobb, 1970b) contain gold, silver, copper, lead, and zinc. Only those on Unga Island have been worked commercially; ore worth about $2 million, chiefly in gold and silver from the Apollo mine, was produced between 1891 and 1904.
The only placer deposit in the Alaska Peninsula region for which there is a production record is an auriferous beach on Popof Island (4, fig. 1), where about 580 ounces of gold was taken out with rockers in 1904 and 1905 from a belt about three-quarters of a mile long. All gold recovered was below midtide level and most was found around large boulders near the low-tide line. Small-scale mining was reported in each of several years before World War I, but there is no record of more recent activity. The source of the gold probably is nearby lodes in intensely altered andesite. Brooks (1912, p. 37) reported beach mining on Unga Island in 1911 but did not identify where on the island or give any idea of the success of the venture.
Titaniferous magnetite and ilmenite are widespread in beach sands along the shores of Bristol Bay (Berryhill, 1963). Berryhill collected samples containing as much as 100 pounds of iron per cubic yard (calculated as content of material in place) from Mof¬fett Point (1, fig. 1), Nelson Lagoon (2), Port Moller (3), and Port Heiden (5). The titania (Ti02) content was generally less than 25 pounds per cubic yard. A few samples contained traces of fine