Vol. 6] Baker: Cenozoic History of the Mohave Desert. 



339 



THE ROSAMOND SERIES OF UPPER MIOCENE AGE 



DEFINITION AND DISTRIBUTION OF THE SERIES 

 Hershey gave the name Rosamond Series in 1902° to a suc- 

 cession of rocks which he characterized as being mainly rhyolitie 

 in composition. The type locality is north and northwest of 

 Rosamond station on the Southern Pacific railway, near the 

 north side of Antelope Valley, and mainly to the west of the 

 railroad between Rosamond station and the town of Mohave. 

 His type section, comprising 1650 feet of strata, is given as 

 follows, beginning with the base: 



Type Section of the Rosamond Series near Rosamond Station 



Thickness. 



Granite. 



1. Coarse and fine white sandstone, composed of granite debris and 



rhyolitie tuff, thin-bedded, regularly stratified and dipping 

 westerly at angles of 10° to 20° 500 ft. 



2. Bright, light red, stratified sandstone containing granite debris, 



some cobbles and boulders (water worn) of granite and many 

 angular and subangular fragments of white tuff 50 



3. Light yellow tuff mainly of rhyolite with an occasional pebble of 



granite; roughly stratified and dipping southerly 200 



4. Massive dark red lava (apparently rhyolite) ; varies much in thick- 



ness, averaging about 100 



5. Light greenish and yellow rhyolite tuff, coarse in layers; contains 



abundant and large angular fragments of the underlying red 

 lava and an occasional pebble and small boulder of granite ; 

 roughly stratified and dips southerly 10° to 30° 400 



6. White rhyolite, brecciated in layers 300 



7. Light brown coarse sandstone ; much granite debris and rhyolite ; 



occurs in limited patches capping knolls 100 



Hershey finds the series in a low mountain four miles west 

 and one mile north of Rosamond, and at Willow Springs Moun- 

 tain, two miles farther northwest. The latter mountain he 

 regards as the site of one of the rhyolite volcanoes. 



This volcanic belt seems to be represented in isolated patches along 

 a line trending nearly due west along the northern border of Antelope 

 Valley to its extreme western end. The purple and white lavas occur- 

 ring in patches faulted down into the granite along the southern base of 



oAm. Geol., vol. 29, pp. 365-370, 1902. 



