SubscribeAvailable Now
View from Window Rock. Photo by Kasey Cordell

Stone Stories: Untangling CNM’s Geology

CNM’s rock layers present a pictorial history of our planet. Use this Bill Nye–style guide to discern the difference between Jurassic (old) and Triassic (really old) stone—and to learn where to see the ancient layers.

 •  

 

Illustration by Brad Cuzen

1. Dakota sandstone | 113 million to 95 million years old*

Dakota sandstone holds deposits from the massive inland sea that existed here about the time bees and flowering plants entered the fossil record.
See It: Atop Black Ridge, on the west side of the monument

2. Burro Canyon formation | 119 million to 97 million years old

Cream-colored and flecked with green shale, the Burro Canyon layer contains petrified wood and the occasional dino bone.
See It: Also on Black Ridge

3. Morrison formation | 161 million to 144 million years old

When archaeologists go fossil hunting, they home in on the terra-cotta-colored Morrison formation, which represents the era when dinosaurs proliferated.
See It: At Highland View, which offers an excellent vantage of CNM’s layers, including the plateau-topping Morrison formation on the other side of the canyon

4. Wanakah formation | 169 million to 163 million years old

This thin line of green and red rock was laid down when the Centennial State was full of mud flats, pterosaurs, and Plesiosaurus (a Loch Ness monster–like creature).
See It: Above the section of Rim Rock Drive at Artists Point

5. Entrada sandstone | 170 million years old

The salmon-hued Entrada sandstone is composed of the remnants of sand dunes that blew over from an inland sea in Utah right around the time salamanders and Stegosaurus showed up on the planet.
See It: At eye level in walls lining the Alcove Nature Trail near the visitor center

6. Kayenta formation | 192 million to 190 million years old

This lighter, yellow-orange rock is relatively resistant to erosion and serves as a protective caprock to many of CNM’s formations. Created when Colorado had a much wetter environment, Kayenta sandstone often has smile shapes in it—the ghosts of ancient streams.
See It: Capping many of the park’s cliffs and buttes

7. Wingate sandstone | 206 million to 192 million years old

Wingate sandstone provides the monument with much of its color and shape: Burnt orange in hue, it’s made up of former sand dunes, hence its vulnerability to erosion. Wind, water, and weather chew through the relatively soft stone, creating arches, windows, and monoliths when sections wear away. See It: Comprising many of the sheer cliffs, like those visible at Fruita Canyon View

8. Chinle formation | 220 million to 206 million years old

The brick red rock at the base of many of the monument’s cliffs was formed by sediment deposits in ancient floodplains when Colorado was prime umbrella-drink territory. Sadly, there were no cabana attendants—or any humans, for that matter—back when our state sat close to the equator.
See It: Where the road cuts through Fruita Canyon

9. Precambrian era | 1.8 billion to 1.72 billion years old†

The gray exposures in the bottom of many canyons have a convoluted story. What started as sedimentary rock has been eroded, melted by volcanic activity, and crunched between continents. It also served as the base of an ancient mountain range, which gradually eroded.
See It: At the bottom of Columbus Canyon, visible at Cold Shivers Point

*Dates reflect the years that are visible in CNM’s rock layers.

†The missing 1.5 billion years of rock record here is called the Great Unconformity. It’s a geologic mystery mashed up by erosion and tectonics.

What We're Reading

Newsletters

Keep me up to date on the latest trends and happenings around Denver. 5280 has a newsletter for everyone.

Sign Up