Usage:
Estill Shale of Crab Orchard Group (KY*,OH*)
Estill Shale Member of Alger Shale of Crab Orchard Group (KY*-local)
Geologic age:
early Silurian (Llandovery)*
Type section, locality, area and/or origin of name:
Exposures northeast of Estill Springs, just north of Irvine, Estill Co., KY (Foerste, 1935).
AAPG geologic province:
Cincinnati arch*
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 ([ ]).