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  • Usage in publication:
    • Omak Lake Granodiorite*
  • Modifications:
    • Named
    • Geochronologic dating
  • Dominant lithology:
    • Granodiorite
  • AAPG geologic province:
    • Okanogan province
Publication:

Goodge, J.W., and Hansen, V.L., 1994, Geologic map of the Omak Lake 15-minute quadrangle, Okanogan County, Washington: U.S. Geological Survey Geologic Quadrangle Map, GQ-1726, 1 sheet, 20 p., scale 1:62,500


Summary:

Named for exposures at Omak Lake. Type locality designated as exposures in roadcuts along west side of Omak Lake Road, about 9 mi south of Omak along west shore of Omak Lake, sec.3 and E/2 sec.4 T32N R27E, Omak Lake 15' quad, Okanogan Co, WA. Consists of coarse-grained porphyritic granodiorite that contains pink to gray K-feldspar megacrysts. Intrudes Salmon Creek Schists and Gneisses. K-Ar determination on biotite from unit yielded 53.4 +/-1.3 Ma (Atwater and Rinehart, 1984). Provisionally assigned Cretaceous or Eocene 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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