|Quadrangle map, 1:250,000-scale||YA|
|Quadrangle map, 1:63,360-scale||D-5|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||Logan Beach is within Yakutat Bay, immediately south of Logan Bluffs; it extends about 2 miles north and 3 miles south of cited coordinate location which is in section 21, T. 24 S., R. 34 E., of the Copper River Meridian. The locality is number 3 of Cobb (1972).|
Logan beach is a wave-cut beach formed from gravelly terrace deposits of glacial material which form the bluffs behind the beach. The bedrock on the upland hills to the east of the deposit consists of graywacke and argillite of the Yakutat Group of Jurassic and Cretaceous age (MacKevett and Plafker, 1970). At the beach, gold occurred in thin transient deposits enriched in garnet or magnetite; the beach placer was derived by winnowing wave-action on weakly auriferous glacial gravels.
The placer could also contain reworked materials brought down from the Jura-Cretaceous bedrock. MacKevett and Plafker (1970, pl. 1) report anomalous amounts of molybdenum (3 to 10 ppm) in two stream sediment samples from the Logan Beach. Molybdenum is commonly enriched in organic shales as well as granitic rocks, but its source in the bedrock behind the Logan Beach is unknown.Reimnitz and Plafker (1976, pl. I) reported 0.010 ppm gold in one sample from the beach.
|Geologic map unit||(-139.593694276043, 59.8196962855753)|
|Mineral deposit model||Placer Au (Cox and Singer, 1986; model 39a).|
|Mineral deposit model number||39a|
|Age of mineralization||Holocene|
|Workings or exploration||Surface workings, rockers and sluices. The occurrence is one of the first placers discovered in the Yakutat quadrangle (Tarr, 1906; Tarr and Butler, 1909).|
|Indication of production||Yes; small|
|Production notes||The beach had a very limited production, with a maximum of a few hundred ounces of gold.|
Additional commentsThe Logan beach placer is within the Russell Fiord Wilderness area of Tongass National Forest.
Cobb, E.H., 1972, Metallic mineral resources map of the Yakutat quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-408, 1 sheet, scale 1:250,000.
MacKevett, E.M., Jr., and Plafker, G., 1970, Geochemical and geophysical reconnaissance of parts of the Yakutat and Mount St. Elias quadrangles, Alaska: U.S. Geological Survey Bulletin 1312-L, p. L1-L12 p.
Reimnitz, Erk, and Plafker, George, 1976, Marine gold placers along the Gulf of Alaska margin: U.S. Geological Survey Bulletin 1415, 16 p., 1 plate.
Tarr, R.S., 1906, The Yakutat Bay region in Brooks, A.H., Report on Progress of Investigations of Mineral Resources of Alaska in 1905: U.S. Geological Survey Bulletin 284, p. 61-64.
Tarr, R.S., and Butler, B.S., 1909, Area geology, in Tarr, R.S., and Butler, B.S., The Yakutat Bay region, Alaska: U.S. Geological Survey Professional Paper 64, p. 145-178.
|Reporters||C. C. Hawley (Hawley Resource Group)|
|Last report date||4/15/1999|