The Red Rock Canyon National Conservation Area is located just a few miles west of Las Vegas and encompasses 195,819 acres within the Mojave Desert. Red Rock Canyon is an area of world wide geologic interest.
Many experienced and amateur geologists alike who visit Red Rock are amazed by the rock formations, natural beauty, and the vivid colors of the rocks. The forces of nature that have formed such a visual display have taken millions of years to create the masterpiece that is now known as Red Rock Canyon National Conservation Area. We invite you to explore and view the geological features that make this area unique.
The great sandstone cliffs at Red Rock, thousands of feet high, are made up of the Aztec Sandstone
. This formation, about 180 – 190 million years old, is comprised of lithified sand dunes that formed in a vast desert that covered a large part of the southwestern United States during the Jurassic time. Lithification is the process of changing unconsolidated sediment into sedimentary rock. Massive cross-bedding, typical of aeolian (wind) deposits, is a result of the shifting wind direction across the Jurassic dune field, and is seen in the Aztec Sandstone rock outcrops.
The red color of some of the outcrops of the Aztec Sandstone is due to presence of iron oxide or hematite. Exposure to the elements caused iron minerals to oxidize or “rust,” resulting in red, orange, and brown-colored rocks. Areas where the rock is buff in color may be places where the iron has been leached out by subsurface water, or where the iron oxide was never deposited.
Red spots in the Aztec Sandstone are iron concretions, where subsurface water has precipitated iron oxide around a nucleus in the sandstone. These concretions are more resistant to erosion than the surrounding sandstone, and weather into little balls known as Indian or Moqui Marbles.
More than 500 million years ago Red Rock Canyon NCA was at the bottom of an ocean basin. Mostly limestone (and dolomite) accumulated in this ocean basin for over 250 million years during the Paleozoic Era. The limestones contain the fossils of sea life that flourished during that time. Thousands of feet of the gray Paleozoic limestones are exposed at LaMadre Mountain to the northwest of the Scenic Loop Drive.
The tracks of small bipedal (two-footed) therapod (meat-eating) dinosaurs have been found in the Aztec Sandstone at Red Rock Canyon in three different places. The small animal tracks made by proto-mammals, early mammals, and arachnids (spiders and scorpions) were also found. Paleontologists are still researching these sites.
Keystone Thrust Fault
As you look at the escarpment to the west you see older gray Paleozoic limestone resting on top of the younger buff and red Jurassic sandstone. This is a result of the Keystone Thrust Fault. Near the end of the Mesozoic Era, about 65 million years ago, the oceanic plate began “subducting” (moving beneath) the western edge of the North American Plate. This resulted in the intrusion of the Sierra Nevada granite batholith, which set up compressional forces in the Earth’s crust that caused the older limestone to be thrust east up and over the younger sandstone. The limestone cap served to protect the weaker sandstone from erosion for millions of years, eventually eroding back to its present location. The compressional thrust faulting at the end of the Mesozoic Era can be traced all the way up into Canada. However, the best exposure of the thrust faulting is here in the Red Rock Canyon NCA.