- Usage in publication:
-
- Gilchrist shale
- Modifications:
-
- Original reference
- Dominant lithology:
-
- Shale
- AAPG geologic province:
-
- Illinois basin
Summary:
Pg. 49, 73, 83, 88, 122, 142. Gilchrist shale in Pottsville formation. Blue-gray to greenish shale, micaceous in some beds; plant impressions irregularly distributed. Thickness 20 to 100+ feet. Complete thickness is penetrated by coal-test boring near Gilchrist, in sec. 17, T. 14 N., R. 2 W., Greene Township, Mercer County, northwestern Illinois, whence name. Well exposed in pits of Hydraulic Press Brick Co. at Shale City and of NW Clay Mfg. Co. at Griffin. Lies 6 to 13+/- feet below top of Pottsville, or base of Colchester coal, in Alexis quadrangle. Age is Pennsylvanian.
Source: US geologic names lexicon (USGS Bull. 896, p. 818-819).
- Usage in publication:
-
- Gilchrist shale
- Modifications:
-
- Revised
- AAPG geologic province:
-
- Illinois basin
Summary:
Pg. 84. Gilchrist shale in Carbondale formation, a little below Colchester (No. 2) coal. Age is Pennsylvanian.
Source: US geologic names lexicon (USGS Bull. 1200, p. 1506).
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 ([ ]).