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  • Usage in publication:
    • Gibraltar Lake Tuff*
  • Modifications:
    • Named
  • Dominant lithology:
    • Tuff
  • AAPG geologic province:
    • Alaska Peninsula province
    • Alaska Southwestern region
Publication:

Detterman, R.L., and Reed, B.L., 1980, Stratigraphy, structure, and economic geology of the Iliamna quadrangle, Alaska, IN Geology of the Iliamna quadrangle, Alaska: U.S. Geological Survey Bulletin, 1368-B, p. B1-B86, (incl. geologic map, scale 1:250,000)


Summary:

Named for Gibraltar Lake which is near type. Type locality at exposures on mountain west of Emerald Lake, south of Iliamna Lake, Iliamna quad, Alaska Peninsula, AK. Consists of rhyolitic crystal and lithic tuff. Informal lower welded tuff member is light-gray to tan color with thickness of 300 to 730 m. Upper ash-flow tuff member is light-gray to white color with thickness of 30 to 182 m. Unconformably overlies older Tertiary volcanic rocks; locally unconformably underlies Intricate Basalt (new). Is Oligocene(?) to Pliocene(?) age.

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


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).

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