You’re sure to find gold along with many other colors at this obscure national landmark near Barstow, CA.
You never heard of Rainbow Basin Natural Area? Me neither until one of my fellow explorers turned me on to it. It’s located just 8 miles north of Barstow, CA which just happened to be on my way to Joshua Tree from my parents house.
It wasn’t as colorful as I imagined a place called RAINBOW Basin would be but its muted color palette, amazing geological formations and lovely layout was well worth the trip.
A very girthy JT on the road to RBNA.
The Rainbow Basin has been designated a National Natural Landmark and is in the Bureau of Land Management managed Rainbow Basin Natural Area.
It is accessible to the public via Irwin Road from Barstow to an unpaved one-way loop road through the colorful basin. The dirt road is a little ruddy in places but still safe for 2WD vehicles.
The basin is notable for: the fantastic and beautiful shapes of its rock formations: its fossil beds, which have provided scientists with valuable information about life during the middle Miocene epoch, between 12 and 16 million years ago; and to the northeast the Calico Early Man Site.
Underneath Rainbow Basin is the massive batholith that lies below much of the western Mojave. Made from a type of rock called quartz monzonite, this batholith dates to either the Cretaceous, or possibly the late Jurassic period. Early in the Cenozoic Era this batholith was exposed in the area surrounding Rainbow Basin and bent downward as it underwent compression, to form a basin.
The narrow road through these incredible formations help create an amazing frame as you slowly drive through absorbing the beauty that appears after every hill or turn.
The majority of the fossil beds in Rainbow Basin are found within the sedimentary rocks of the Barstow Formation. They include many animals not found in California today, including camels, horses, mastodons, and flamingos.
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. Above this is the Pickhandle Formation. The sediments making up this formation are mostly of volcanic origin – tuff, rhyolite and andesite. The highest of the three formations is the Barstow Formation, which is made up of layers of conglomerate, limestone, sandstone, and shale.
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.