Rainbow Basin Natural Area is located about eight miles north of the city of Barstow, CA in the Calico Peaks Range. I have included a click-able map at the bottom of this post, it will take you to an interactive Google map for easy driving instructions.
The scenic loop drive is along a well maintained dirt road that is suitable for most passenger vehicles, including a standard car (please be aware that this status can change at any time, especially after heavy rain – when in doubt contact the Barstow BLM Field Office at (760) 252-6000 for current conditions). The loop should NOT be driven by motorhomes or vehicles towing a trailer, there are some narrow sections with tight turns, and I’m positive that you wouldn’t like the fee associated with getting towed out of the desert.
Rainbow Basin is very special to me, it was one of the first places that I had visited in the desert, in my earliest desert years. I didn’t have a Jeep back then, but rather a low to the ground car – which limited my access to many places.
After dozens of times saying that I needed to return, I finally did in October of this year – and I found it exactly as I had remembered it. It’s colorful and unusual rock formations, are nearly unrivaled – with only a few locations in the Mojave Desert that can truly challenge it’s uniqueness and beauty.
To the average person, Rainbow Basin will likely be seen as colorful rocks, and unusual formations – and that is perfectly fine, because that is exactly what it is – only on steroids.
From a geological standpoint, there is a larger story to be told. That story begins 145-66 millions years ago, during the Cretaceous period. A Batholith, or rather rock that formed from cooled magma was formed under much of the western Mojave Desert. This batholith, in the Cenozoic era (66-0 million years ago) became exposed around this area, and bending downward, forming Rainbow Basin. Further compression, uplift, and finally extension left these sedimentary formations deeply folded, the most prominent fold being the Barstow Syncline (a fold with younger layers closer to the center of the structure). These same stresses also produced several faults in the Rainbow Basin area.
The thick sedimentary layers can be divided into three distinct formations. The lowest is called the Jackhammer Formation, and it is composed of layers of sandstone, siltstone, limestone, and conglomerate, all probably dating to the early Miocene Epoch.
Above this is the Pickhandle Formation. The sediments making up this formation are mostly of volcanic origin – tuff, rhyolite and andesite, indicating that they were laid down during a period of active volcanism. That time was probably during the early Miocene.
The highest of the three formations is the Barstow Formation, which is made up of layers of conglomerate, limestone, sandstone, and shale. This formation dates to the middle to late Miocene and it contains one of the largest Cenozoic fossil assemblages in North America. Most of the sediment that makes up the layers in this formation was stream-laid, but there is a white layer of rhyolitic tuff near the top.
Finally, on top of everything else, is a relatively thin layer of fanglomerate (alluvial fan deposits) laid down during the late Pleistocene. Differential erosion of rocks of different hardness finished the job of sculpting the formations into the fantastic shapes that can be seen in Rainbow Basin today.
The fossils that are found in Rainbow Basin are unique, and include several species of animals that can no longer be found in California, this includes camels, horses, mastodons, and flamingos. Scientists believe that these fossils are from the Barstovian Land Mammal age, or 16,300,000 to 13,600,000 years before present.
When visiting Rainbow Basin, I highly recommend not only driving the loop, but also hiking the canyons contained within. There are plenty of pull-offs that allow for a short stroll or a longer hike to see the various formations up-close. If you are lucky, you just may find a fossil or two (please do not remove fossils – leave them for others to enjoy).
Drive Rainbow Basin from the comfort of your home: