Massive, coarse-grained, light-gray porphyritic quartz monzonite (Detterman and Reed, 1980; Nelson and others, 1983) is associated spatially with the Alaska-Aleutian Range batholith in the Iliamna and Lake Clark quadrangles. K/Ar ages range from 85.5 to 75.6 Ma (Reed and Lanphere, 1972). In northern Tyonek quadrangle, fine- to medium-grained pink monzonite or syenite intrudes sedimentary rocks of unit Kfy and contains primary pyroxene and has yielded a concordant U/Pb zircon age of 80.3±0.1 Ma (P.J. Haeussler, USGS, unpub. data). Pluton is distinctive in being more potassium-feldspar-rich and quartz-poor than other granitic rocks in the region. Unit also includes undated plutons in the Talkeetna Mountains quadrangle. In the west-central Dillingham quadrangle an unusual highly potassic coarse-grained biotite-pyroxene granite or syenite yielded an 40Ar/39Ar age of 84.49 Ma; this pluton is similar to other potassium-rich rocks in the Dillingham area (see unit TKg) except for age