Usage:
Placid Shale Member of Brad Formation of Canyon Group (TX*)
Placid Shale of Canyon Group (TX)
Placid Formation (TX)
Subunits:
Merriman Limestone [unranked] (TX).
Geologic age:
Late Pennsylvanian (Missourian)*
Type section, locality, area and/or origin of name:
Named from town of Placid in McCulloch Co., TX, which is situated on the outcrop (Plummer and Moore, 1922).
AAPG geologic province:
Llano uplift*
Bend arch*
Fort Worth syncline
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 ([ ]).