Usage:
Walnut Clay of Fredericksburg Group (AR*,OK*,TX*, and LA*-subsurface)
Walnut Formation of Fredericksburg Group (NM,TX*)
Walnut Marl of Fredericksburg Group (OK,TX)
Walnut Member of Goodland Limestone of Fredericksburg Group (recognized locally in northeast TX* and southeast OK)
Subunits:
(alphabetical): Bee Cave Member, Cedar Park Member, Keys Valley Marl Member.
Geologic age:
late Early Cretaceous (Albian)*
Type section, locality, area and/or origin of name:
Not designated. Named from their characteristic occurrence at Walnut [Walnut Springs], Bosque Co., TX (Hill, 1891).
AAPG geologic province:
Ouachita folded belt*
Arkla basin*
East Texas basin*
Strawn basin*
Llano uplift*
Kerr basin*
Permian basin*
South Oklahoma folded belt*
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 ([ ]).