Usage:
/Mud Lake Gray Shale Member of /Antrim Formation of /Antrim Group (MI)
[Conflicts with several articles in nomenclature guidelines (NACSN, 1983, 2005, 2021). Considered an invalid name. Not used by the USGS.]
Geologic age:
Devonian
Type section, locality, area and/or origin of name:
Origin of name and type locality not stated by authors (Dellapenna and others [abs.], 1991).
AAPG geologic province:
Michigan basin
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 ([ ]).