Rainbow Basin

Rainbow Basin sits in the Calico Peaks range of the Mojave Desert, about 8 miles north of Barstow in San Bernardino County, California. It rests on a quartz monzonite batholith dating to the late Jurassic or Cretaceous, above which lie three younger sedimentary units, the sandstone-siltstone-limestone-conglomerate Jackhammer Formation, the volcanic tuff, rhyolite and andesite of the Pickhandle Formation, and the conglomerate, limestone, sandstone and shale of the Barstow Formation. During the Cenozoic the buried batholith was exposed and bent downward under regional compression, forming a basin, and further compression, uplift and extension folded the sedimentary layers above it into the prominent Barstow Syncline along with several faults. A distinctive white band of rhyolitic tuff marks the upper Barstow Formation, and differential erosion of the varied rock types has sculpted the folded layers into the basin's striking badlands shapes and colors. This entity documents Rainbow Basin specifically as a geological formation.