Usage:
Grassy Mountain Ignimbrite of /Butler Hill Group of /St. Francois Mountains Volcanic Supergroup (MO-recognized locally in St. Francois Mountains area)
[Name Butler Hill applied concurrently to two different units in same area; preempted by Butler Hill Granite by Tolman and Robertson (1969); name St. Francois Mountains applied concurrently to two different units in same area; a [supergroup] name combines a geographic name with the term ["supergroup,"] and no lithic designation is included (see ACSN, 1970; NACSN, 1983, 2005, 2021).]
Geologic age:
Mesoproterozoic
Type section, locality, area and/or origin of name:
Typical exposures located on Grassy Mountain, Iron Co., MO. Named from Grassy Mountain (Sides, 1976).
AAPG geologic province:
Midcontinent region
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 ([ ]).