Red Rock Canyon
Just a 20 minute drive out of Las Vegas is Red Rock canyon, part of the enormous Mojave desert. While we were visiting Las Vegas we spent the afternoon here walking and admiring the beauty of the landscape.
The Red Rock Canyon landscape has been created through a complex history of marine and prehistoric dune deposits, severe faulting, and subsequent erosion. For much of the past 600 million years, this area was submerged beneath a deep ocean basin, filled with an abundance of primitive marine life. As these organisms died, they left behind deposits of shells and skeletons more than 9000ft thick that were eventually compressed into limestone and similar carbonate rocks.
Around 225 million years ago, crustal movements slowly raised the seabed causing deposition of mud and sand into the shallower waters by stream action. From this activity, shales and mudstones were formed. Large isolated bodies of water evaporated leaving behind layers of salt and gypsum in some areas. Exposure of sediments to the atmosphere allowed some of the minerals to oxidize, resulting in red and orange coloured rocks.
Major climate changes occurring about 180 million years ago created a vast desert area throughout the southwest. A giant dunefield stretched from this area eastwards towards Colorado, and windblown sand piled more than half a mile deep in some spots. These constantly shifting dunes were buried by other sediments and eventually cemented into crossbedded and colourful sandstones. Locally this formation is called Aztec Sandstone and forms the Calico Hills and the prominent Red Rock escarpment. Altered and concentrated iron minerals in the rocks are responsible for the reddish hues.
The most significant geologic feature of Red Rock Canyon is the Keystone Thrust Fault that began to develop 65 million years ago. A thrust fault is a fracture in the earth’s crust resulting from compression that drives one crustal plate over the top of another. Thus the oldest rocks, once at the bottom end up directly above the youngest rocks. At Red Rock Canyon the grey carbonate rocks of the ancient ocean have been thrust over the tan and red sandstone of younger deserts.
Below are a selection of photographs from my visit there.