Entrada Sandstone is found in Wyoming, Colorado, New Mexico, Arizona, and Utah. It’s believed this formation was deposited during the Jurassic Period sometime between 180 and 140 million years ago, as tidal mudflats, sand dunes and beaches.
It’s an interesting formation which in places is known to contain dinosaur footprints. One of these spots is Utah. I didn’t have time to stop to see them this time, but it’s now on my bucket list.