El Paso Mountains

Lying to the north of the Garlock fault, the El Paso Mountains form a portion of the northern border of the Mojave Desert. Three plant communities are present, with most of the area in grassland or creosote bush scrub; Larrea tridentata is the dominant in the latter, with the Joshua tree, Yucca brevifolia, common. In portions of the area, mesquite scrub with mesquite, Prosopis glandulosa var. torreyana, arrowscale, Atriplex phyllostegia, and Mormon tea, Ephedra viridis, is the major community.

The rare Camissonia kernensis ssp. kernensis occurs here. Other plants of note are Cymopterus deserticola and Hemizonia arida.

There are numerous desert animals, with the desert iguana, Dipsosaurus dorsalis, desert tortoise, Gopherus agassizi, cactus wren, Campylorhynchus brunneicapillus, and the Merriam kangaroo rat, Dipodomys merriami, among the more conspicuous. The rare Mojave ground squirrel, Citellus mohavensis, inhabits the area.

Geologically, this region includes a wide spectrum of rock types and ages, ranging from possible Pre-Cambrian metamorphics and Paleozoic sedimentaries to Recent alluvium. Of note are the nonmarine sedimentary formations, the Goler, which may date to the Paleocene, and the Ricardo of the early Pliocene. In the former, the earliest known mammalian fossils in the State have been unearthed. They include a multituberculate and several species of condylarths. Additionally, leaf imprints of several tropical or subtropical plant species such as tree ferns, magnolias, sapota, and various broad-leafed evergreens have been recovered.

The Ricardo formation has yielded a large and varied terrestrial fauna including four horses, Hipparion, Neohipparion, Pliohippus and Hypohippus, a rhinoceros, Aphelops, three camels, Megatylopus, Procamelus and Pliauchenia, a four-tusked mastodon, Gomphoterium, oreodonts, various rodents, the pronghorns, Sphenophalos and Merycodus, a dog-bear, Hadrocyon, and a true dog, Tomarctus. Petrified wood and other fossils reveal a flora which included live oak, pinyon pine, cypress, acacia, palm and locust.

Integrity: Sheep grazing, limited mining activity and off-road-vehicle use have had an impact on portions of the area but much of it is virtually undisturbed. A major portion of this area has been proposed for a special management area.

Use: Research, educational, observational, light recreation. There is some private land in the area.

Ref: McKenna, M. C. 1960. A Continental Paleocene vertebrate fauna from California. Amer. Mus. Nov. No. 2024, pp. 1-20.

May 1977