This layer averages about 545 million years old and is composed of medium-grained and coarse-grained sandstone. Ripple marks formed by ocean waves of an early Cambrian sea are common in the upper layer. The Tapeats is similar to the Redwall in that it forms a barrier between upper and lower reaches of the Canyon that can only be traversed where a fault has caused its collapse. The color of this layer is dark brown and it contains fossils of trilobites. brachiopods, and trilobite trails.
 
Grand Canyon Rock Layers
 

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