- Usage in publication:
-
- Flowery Trail Granodiorite*
- Modifications:
-
- Named
- Dominant lithology:
-
- Granodiorite
- AAPG geologic province:
-
- Okanogan province
Summary:
Named for and type locality designated as roadcut exposures along Flowery Trail Road, especially near bottom of Chewelah Mountain ski lift [3 to 7 mi northeast of Chewelah, secs.1-4 T32N R41E] Stevens Co, WA. Average rock is medium-grained, hypidiomorphic-granular, hornblende-biotite granodiorite with color index range of 22-45. Dikes as much as 100 m long penetrate wallrock. Appears to have been mildly metamorphosed by muscovite quartz monzonite. Assigned "probable Mesozoic" age.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Flowery Trail Granodiorite*
- Modifications:
-
- Age modified
- Geochronologic dating
- AAPG geologic province:
-
- Okanogan province
Summary:
Description of unit more detailed than Clark and Miller (1968). Three Hornblende (H) - Biotite (B) pairs yield discordant ages:
1. (H) 194 +/- 7 Ma (B) 98 +/- 5 Ma
2. (H) 183 +/- 6 Ma (B) 84 +/- 3 Ma
3. (H) 143 +/- 5 Ma (B) 64 +/- 3 Ma
Samples along 3.3-mile line show consistent age loss in easterly direction; graphing the data, however, suggests "true age" probably not much greater than 195 Ma. Age revised to Late Triassic or Early Jurassic.
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 ([ ]).