Scenic Drive Stop 3

Old uranium mines can be seen near the base of the cliffs just past the entrance to Grand Wash Road.

NPS / E. Van Ness

Here, the Chinle Formation begins with a hard yellowish-gray layer called Shinarump Conglomerate. Why don’t you see this layer at the entrance to the Scenic Drive? This rock was deposited by rushing braided rivers carrying stones and pebbles. Where rivers flowed, the Shinarump exists. Where the land stayed dry, it does not. Scan this layer for several entrances to the Oyler Uranium Mine, used as early as 1904. Ultimately, little uranium was found here, but radiation can create health and safety hazards. Do not enter abandoned mines. Read the wayside panel for more information about uranium mining.

Above the Shinarump Conglomerate is a gray-green layer within the Chinle Formation. The southwest is sometimes known as red rock country for good reason. Most of the rocks here are stained red because they were created in oxygen-rich environments and contain oxidized iron, or rust. What created that striking gray-green color? Imagine standing in a tropical swamp 215 million years ago, surrounded by primitive trees and giant ferns. The humid air is thick in your throat. The water is murky and contains ash from distant volcanoes. The stagnant bog lacks oxygen and results in today’s greenish color. As the Chinle Formation ascends to the base of the sheer cliff wall, it transitions in color to orange and burgundy, showing the return of oxygen-rich rivers.