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Map showing publication footprint
  • Usage in publication:
    • Amchitka formation*
  • Modifications:
    • Named
  • Dominant lithology:
    • Breccia
    • Tuff
  • AAPG geologic province:
    • Aleutian Islands province
    • Alaska Southwestern region
Publication:

Powers, H.A., Coats, R.R., and Nelson, W.H., 1960, Geology and submarine physiography of Amchitka Island, Alaska, IN Investigations of Alaskan volcanoes: U.S. Geological Survey Bulletin, 1028-P, p. P521-P554, (incl. geologic map, scale 1:200,000)


Summary:

Makes up northern part of western third and most of eastern fourth of island and small isolated exposures at and west of Cyril Cove. Consists of water-laid beds of volcanic breccia, thin-bedded fine-grained tuff and pillow lavas, andesitic to latitic in composition. Rock is mottled dull yellowish-brown and olive-green to blue-green with streaks of white. Is perhaps several thousand feet thick. Geologic age is unknown but is as old as early Tertiary; overlying Banjo Point formation (new) is early middle Tertiary age.
Type section: exposures along south coast from South Bight westward to Long. 179 deg. 18 min. E., Amchitka Island, Aleutian Islands, southwestern AK.

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


Map showing publication footprint
  • Usage in publication:
    • Amchitka Formation*
  • Modifications:
    • Areal extent
    • Age modified
  • AAPG geologic province:
    • Aleutian Islands province
    • Alaska Southwestern region
Publication:

Carr, W.J., Quinlivan, W.D., and Gard, L.M., Jr., 1970, Age and stratigraphic relations of Amchitka, Banjo Point, and Chitka Point Formations, Amchitka Island, Aleutian Islands, Alaska, IN Cohee, G.V., Bates, R.G., and Wright, W.B., Changes in stratigraphic nomenclature by the U.S. Geological Survey, 1969: U.S. Geological Survey Bulletin, 1324-A, p. A16-A22.


Summary:

Amchitka Formation of Powers and others (1960) is geographically restricted to eastern part of Amchitka Island. Rocks in northwestern part are assigned to Chitka Point Formation; these rocks are petrographically like and stratigraphically continuous with Chitka Point Formation. Amchitka Formation is informally divided into: (1) older breccia and (2) pillow lavas and breccias of Kirilof Point which are separately shown on geologic sketch map. Assigned early Tertiary age on basis of stratigraphic relations.

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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