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Geologic Units: Siwash
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  • Usage in publication:
    • Siwash Formation
  • Modifications:
    • Named
  • Dominant lithology:
    • Tuff
  • AAPG geologic province:
    • Okanogan province
Publication:

Marjaniemi, D.K., and Robins, J.W., 1975, Uranium favorability of Tertiary sedimentary rocks of the western Okanogan Highlands and upper Columbia River Valley, Washington: Lucius Pitkin, Inc., 64 p., Prepared for the U.S. Energy Research and Development Administration


Summary:

Unit is named the Siwash Formation. Credited to Woodward (1936). Consists of gray and greenish-gray tuff and shale. Thickness is 350 m. Overlies andesite; underlies the Antoine Formation. Age is Tertiary (B1520)

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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