As the oldest layer present in Sedona, the Red Wall Limestone is over 330 million years old. As the seas flowed over ancient Sedona they deposited ocean minerals that in turn are lithified into the Redwall Limestone that makes up the bottom of the visible red-rock formations in Sedona (DeMayo). This layer is relatively brown in color and because it was lithified at the bottom of the ocean, fossils have been known to be discovered embedded in the ancient rock. One interesting characteristic of the Redwall Limestone around the city of Sedona is the formation of sinkholes. This is said to be caused by the cave solutions in the Redwall Limestone that have collapsed under the weight of the sandstone above. There are, however, no caves that have been discovered in the Sedona region and this theory is mostly speculation based on the similarities between the limestone caves of the Grand Canyon Region (Arizona Ruins, “The Geology of Sedona”).
The Redwall Limestone
(Left) The Devil's Kitchen sinkhole located in the Red Wall Limestone layer of Sedona.