- Usage in publication:
-
- Pony Group*
- Modifications:
-
- Age modified
- Overview
- AAPG geologic province:
-
- Northern Rocky Mountain region
Summary:
Exposed near Pony in northeastern part of Tobacco Root Range, Madison Co, MT, in Northern Rocky Mountain region. Rocks assigned to Pony are thought to be part of the same sequence as those called Cherry Creek Group in western part of Ruby Range and on east flank of Gravelly Range. Is assigned an Archean age in this report. Previously assigned to Precambrian. Evidence shows that Cherry Creek and Pony Groups were affected by dynamothermal metamorphism about 2,750 m.y. ago.
Source: GNU records (USGS DDS-6; Denver 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 ([ ]).