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National Geologic Map Database

Geologic Unit: Placid

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 ([ ]).