Usage:
Tonto Group (AZ*, and NV-local)
Subunits:
(alphabetical) --all in AZ*: Bright Angel Shale, Muav Limestone, Tapeats Sandstone.
Geologic age:
Cambrian, Early*
Cambrian, Middle*
Type section, locality, area and/or origin of name:
Exposures in the Grand Cañon of the Colorado. Floors the valleys that contain the headwaters of Big Williams Fork of the Colorado and of the Verde and Tonto Creek, tributaries of the Salt River [Coconino and Mohave Cos.], northwestern AZ (Gilbert, 1874, 1875).
[Proposed principal reference locality]: Blacktail Canyon, along the Colorado River at mile 120.2, btw. Conquistador and Stephen Aisles, western Grand Canyon, Lat. 36 deg. 14 min. 25 sec. N., Long. 112 deg. 28 min. 21 sec. W., [Explorers Monument 7.5-min quadrangle (1988 ed.), Coconino Co., Grand Canyon National Park, northern AZ]. Colorado River mile 0 at Lees Ferry, [Glen Canyon National Recreation Area, Lees Ferry 7.5-min quadrangle (1985 ed.), Coconino Co., northern AZ] (Rose, 2011).
AAPG geologic province:
Plateau sedimentary province*
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 ([ ]).