Bright Angel Shale

Bright Angel Shale Stratigraphic range: Middle Cambrian
Muav Limestone-(dk or lt gray, brown, or orange-red subcliff at base of Redwall Limestone cliff) and Bright Angel Shale (greenish slope-former), resting on Tapeats Sandstone (short, dp brown vertical cliff) (Tapeats forms the "Tonto Platform"), inner canyon, Granite Gorge. (The 3 units–Muav, Bright Angel, and Tapeats, are easily seen below the red-stained Redwall Limestone (550 ft thick))
Type	Geological formation
Unit of	Tonto Group
Underlies	Muav Limestone
Overlies	Tapeats Sandstone
Thickness	500 feet (150 m) at its maximum
Lithology
Primary	micaceous siltstone and shale
Other	sandstone and glauconitic sandstone
Location
Region	northern Arizona, southeast California, southern Nevada, and southcentral Utah
Country	United States of America
Type section
Named for	Bright Angel Canyon, Bright Angel quadrangle, Coconino Co., Arizona
Named by	Noble (1914)

The Cambrian Bright Angel Shale is the middle member of the 3-member Tonto Group. It is about 500 feet (152 m) thick at its maximum. It is a nonresistant slope-forming unit. The Bright Angel Shale consists of green and purple-red, siltstone and shale which is interbedded with red-brown to brown sandstone that is similar in lithology to the underlying Tapeats. The Bright Angel Shale underlies and interfingers with Muav Limestone. The Bright Angel Shale is located in the lower elevations of the Grand Canyon, Arizona.

The units of the Tonto Group: