ⓘ Bright Angel Shale. The Cambrian Bright Angel Shale is the middle layer of the three member Tonto Group geologic feature. It is about 500 feet thick at its maxi ..

                                     

ⓘ Bright Angel Shale

The Cambrian Bright Angel Shale is the middle layer of the three member Tonto Group geologic feature. It is about 500 feet 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 Bright Angel Shale preserves fossils dating back to the Cambrian Period.

The three units of the Tonto Group and the colorful Bright Angel Shale are easily identified as a geological sequence beneath the tall cliffs of the Redwall Limestone the Redwall sits upon a short resistant cliff of Muav Limestone; the Tonto Group is also easily seen beside Granite Gorge of the Colorado River and the Vishnu Basement Rocks The units of the Tonto Group:

  • Redwall Limestone
  • Bright Angel Shale
  • Tonto Group ~544-505 Ma
  • Muav Limestone
  • Temple Butte Formation, Devonian-409-363 Ma, channel deposits upon Muav Limestone
  • Tapeats Sandstone