West Mojave Plan FEIR/S - Desert Managers Group

In the southern area, fossils of late Arikareean and early Hemingfordian fauna areseparated by a tuff dated at 21 million years. This is one of the best calibrations of the boundarybetween currently known mammal ages. To the north near Afton Canyon, fossils are mainly ofHemingfordian age. This area is one of the most important regions in the Mojave Desert forbiostratigraphy and geologic history. It provides one of the best single reference areas for thelate Arikareean to late Hemingfordian interval in California and would form a secure base withwhich to evaluate the geological history of this part of the Mojave Desert (Woodburne 1978:62-63).Southwest of Crucero, Rancholabrean age mammal remains were observed inconglomerates and sandstones (Woodburne 1978:65).Daggett Ridge, about 4 miles southwest of Daggett, consists of a few hundred feet offine-grained sandstone and siltstone and a thin, lower bed of gray sandstone that produces bonechips. This Miocene deposit contains small camels, a cervoid, and a horse. These remains dateto about the middle of the Hemingfordian and could contribute significantly to an understandingof the little known faunas of this age in the Mojave (Woodburne 1978:66).The Calico Mountain range east of Barstow contains the Jackhammer, Pickhandle, andBarstow Formations (Woodburn 1978:67). Fossil vertebrates have been found in the CalicoMountains in the Barstow Formation, which is approximately 3,000 feet thick. The primaryspecimen is of the grazing-browsing horse (Merychippus intermontanus). Insect-bearing nodulesalso occur. The Calico Range has definite potential to yield fossils, but much of it is located onprivate land with limited access (Woodburne 1978:67-68).The Mud Hills, about 8 miles north of Barstow, contains outcrops of Jackhammer,Pickhandle, and Barstow Formations. The Barstow Formation, named for the Barstow fossilbeds, is a non-marine, late Miocene age geologic unit derived from stream and lake depositedsediments in a basin subject to periodic volcanic ash fall and dust (Woodburne 1978:69; Savage,Downs, and Poe 1954:48). Deposition occurred about 15 million years ago. Many fossils occurin strata of mud mixed with volcanic ash. These strata often erode out as green and dark brownlayers.Fresh-water shells are abundant, but sabel palm is the only identified plant. Variousinstitutions in the United States have collected a large number of mammal bones. Grazingbrowsinghorses (Merychippus) and camelids appear to be the most abundant. Many othermammal species have been described, including browsing horses (Hypohippus), dog-bears(Hemicyon), pronghorns, peccaries, chipmunks, field mice, rabbits, dogs, sabre cats, true cats,mastodons, large oreodonts (Brachycrus), and shrews. Two hawks, several ducks, a gull, aflamingo-like bird (Megapaloelodus), and a quail-like bird (Cyrtonyx) have been identified. Thecharacteristics of the flora and fauna (called “Barstovian” fauna) suggest that grassland wasavailable as well as vegetation similar to that of northern Mexico (Woodburn 1978:71; Savage,Downs, and Poe 1954:48). An overview of Barstovian Fauna is presented in Table 3-66.Chapter 3 3-291