Bureau of Mines in the mid- to late 1960's followed extensive exploratio by a minerals division of Shell Oil Company (Daly, 1969). Probably most of the rich relict gravel is only about 30 centimeters (1 foot) thick.? Investigations carried out by the U.S. The gold in the relict concentrations was as much as several mm in diameter, and averaged about 1 millimeter in diameter and 1 milligram in weight. They also found that lag gravel on top of the till contained as much as 2,500 ppb gold and that one-third of their samples of materials enriched by lag processes contained more than 600 ppb gold. Nelson and Hopkins (1972) reported that average offshore glacial till derived from this and possibly other glacial events contained 70 ppb of gold and that glacial outwash contained more. One interpretation is that productive placer deposits at Bangor Creek, Monument Creek, Boulder Creek, Glacier Creek, and Rock Creek were effectively cut off at the flood plain of Snake River by a glacier that occupied the main valley of the ancestral river. The gold in the auriferous glacial deposits was at least partly derived from gold-bearing alluvium in the ancestral Snake River. The offshore marine glacial deposits have been mapped by high-resolution seismic studies, first by Tagg and Greene (1973), then, using refined instruments and techniques, by Graul and others (1989). The glacial deposits are roughly centered on the projection of Snake River, before it makes an abrubt easterly turn to its present mouth. Gold also occurs in lag deposits formed from weakly auriferous glacial drift and outwash far from the modern beach deposits. There are potential complications with this interpretation, but these are beyond the scope of this summary.? Some of the offshore gold is derived from the abrasion platform immediately offshore of the modern beach. The origin of the deposits is complex and considered to be intimately related to the glacial history of the area (Hopkins and others, 1960). From mean lower low tide, the auriferous deposits extend seaward for about 2 miles. From about 1960 to 1991, and especially from 1987 to 1990, there has been significant exploration and gold production. Geologic Description = Gold occurs in offshore placer deposits off the coast of Nome, particularly from a point west of the mouth of the Nome River to near Penny River.

Dredge placer mining