These layers average about 825 to 1,000 million years old and are composed of the following:

• Sixtymile Formation

  This tan colored layer is composed primarily of sandstone with some small sections of shale.

• Kwagunt Formation

  This layer is composed primarily of shale and mudstone with some limestone. In the area of Carbon Butte the lower layer also contains a large section of reddish sandstone. The shales within this layer are black and the mudstones range from red to purple. Fossils to be found in this layer are those of stromatolites, the oldest fossils to be found anywhere in the Grand Canyon.

• Galeros Formaton

  This layer is composed of interbedded sandstone, limestone and shale. The color is primarily greenish with some of the shales ranging from red to purple. Fossil stromatolites also exist in this layer.

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