K: Keystone Thrust
Keystone Thrust is the name for a prominent geologic fault in Red Rock Canyon. Faults are fractures in the Earth’s crust that occur from the movement of rock layers.
The Keystone Thrust is one of a series of faults that formed an estimated 65 million years ago, near the end of the Mesozoic geologic era – about the same time that the dinosaurs went extinct. At this time, the Pacific plate began moving under the North American plate. This caused compressional forces to push up older limestone rock layers over younger sandstone rock layers. At Red Rock Canyon, this is visible as grayish carbonate or limestone layers over red- and buff-colored sandstone.
This feature runs north & south for 13 miles along State Route 159, and curves at La Madre Mountain. It is one of the best examples of thrust faulting there is because you can stand along it with one foot on the younger sandstone rock layer and the other foot on the older limestone rock layer.