Usage:
Tornillo Group (TX)
Tornillo Formation of Chilicotal Group (TX)
Tornillo Clay (TX*)
Subunits:
GROUP STATUS (alphabetical): Aguja Formation, Black Peaks Formation, Hannold Hill Formation, Javelina Formation.
FORMATION STATUS (alphabetical): Big Yellow Sandstone Member, Black Peaks Member, Hannold Hill Member, Javelina Member.
Geologic age:
Late Cretaceous*
Type section, locality, area and/or origin of name:
Not designated. Named from exposures along Tornillo Creek, southern Brewster Co., TX (Udden, 1907).
AAPG geologic province:
Permian 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 ([ ]).