Potassium-argon ages of basement rocks from St. George Island, Alaska

St. George Island is one of the Pribilof Islands which lie between 56°35' and 57°11' N. lat. in the Bering Sea, 350 km north of the Aleutian chain. The islands are situated near the margin of the continental platform that underlies most of the northern half of the Bering Sea (fig. 1). The islands are made up mostly of olivine basalt and basanite flows, pillow breccias, pyroclastic deposits, sills and dikes, most of which are nepheline normative (Barth, 1956). The volcanic rocks are late Pliocene to Holocene in age (Cox and others, 1966; D. M. Hopkins and M. L. Silberman, unpub. data) and are interbedded with marine sand and gravel, glacially derived sediments, frost breccia, and windblown sand and silt.