Named for Getmuna Creek in central Kuskokwim region, southwestern AK. Occupies elongate area of about 15 sq mi north of Horn Mountains across middle course of Getmuna Creek, southwestern tributary of Crooked Creek. Rhyolitic tuff comprises major part of unit though some albite rhyolite lava crops out in small tract about 3 sq mi at southwest end of outcrop area. Lava is light purplish brown weathering to buff. Tuff is mottled with contrasting light and dark shades weathering to buff. Group is at least 500 ft thick with maximum of 1500 ft. Is believed to cover folded and dissected Kuskokwim group (new) and to postdate Iditarod basalt (new). Is probably older and extends beneath Holokuk basalt (new) since the basalt contains fragments apparently from Getmuna flows. Is probably early Tertiary(?) age. Its upper age limit is probably Miocene(?). Geologic map of central Kuskokwim region shows Eocene(?), Oligocene(?), and Miocene(?) age.

Source: GNU records (USGS DDS-6; Menlo GNULEX).