Usage:
Riddle Formation of Myrtle Group (OR*)
Geologic age:
Late Jurassic to Early Cretaceous*
Type section, locality, area and/or origin of name:
Type section: about 10 mi east of Riddle along South Umpqua River from 0.5 to 1 mi above mouth of Days Creek in E/2 sec. 16 and W/2 sec. 15, T. 30 N., R. 4 W., Douglas Co., southwestern OR. Named from town of Riddle. Well exposed in valley of South Umpqua River and its tributaries, Days Creek, Cow Creek, and Myrtle Creek, in Days Creek, Canyonville, Roseburg, and Dutchman Butte quadrangles (Imlay and others, 1959).
AAPG geologic province:
Western Columbia 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 ([ ]).