Tertiary volcanic and hypabyssal rocks in the Ugashik quadrangle: A section in Geological Survey research 1981

Potassium-argon dating of volcanic and hypabyssal rocks from the Ugashik quadrangle by F. H. Wilson and Nora Shew indicates that these rocks fall into the same two age groupings as those of the Chignik and Sutwik Island quadrangles to the south. Rocks of late Eocene to earliest Miocene and latest Miocene to Holocene age are found in both areas. Preliminary mapping by R. L. Detterman, J. E. Case, and F. H. Wilson indicates a major break in the trend to the west. This offset occurs in the vicinity of Wide and Puale Bays.