- Usage in publication:
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- Loomis granodiorite
- Modifications:
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- Named
- Dominant lithology:
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- Granodiorite
- AAPG geologic province:
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- Okanogan province
Summary:
Loomis granodiorite. Name proposed for unit in /Toats Coulee magma series [informal] (new). Mapped in area northwest, west, and southwest of Loomis in Toats Coulee region, Okanogan Range, Washington. Described as light-gray, medium-grained granodiorite with euhedral hornblende crystals and secondary biotite. Age is Late Triassic, based on radiometric (K-Ar, hornblende) age of 194 +/-6 Ma (citing Rinehart and Fox [1972]). [Age is Early Jurassic, based on 1983 DNAG Geologic Time Scale and 1986 USGS Geologic Time Chart.]
Type area: near town of Loomis, Okanogan Co., WA.
["Toats Coulee magma series" considered informal. Term "Series" is applied formally only to chronostratigraphic units (ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). US geologic names lexicon (USGS Bull. 1520, p. 185) lists Loomis Granodiorite of Toats Coulee Group (explanation not given).]
Source: GNU records (USGS DDS-6; Menlo GNULEX); US geologic names lexicon (USGS Bull. 1520, p. 185).
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 ([ ]).