446 



University of California Publications in Geology [Vol. ll 



the Rosamond as described by him was accumulated mainly "under 

 the same conditions of desert aggradation as operate in the region at 

 the present day." As is suggested in the following discussion (p. 450) 

 the writer considers that during deposition of the Barstow beds 

 the climate may have been considerably more humid than at the 

 present time. 



The Barstow syncline section was divided by Baker into the follow- 

 ing five members : 



1. Fossiliferous tuff member (uppermost division). 



2. Eesistant breccia member. 



3. Fine ashy and shaly tuff member. 



4. Tuff-breccia member. 



5. Basal breccia member (lowest division). 



The five divisions in the Barstow syncline were considered by 

 Baker to represent to some extent local conditions, the number of 

 members being possibly increased or diminished at other localities in 



N 10 



Fig. 2. North and south section through the middle of the minor axis of the 

 Barstow syncline. Length of section is approximately three miles. (1) Basin 

 alluvium. (2) Basic andcsite or acid basalt. (3) Basal breccia member. (4) 

 Fine ashy and shaly tuff member. (5) Eesistant breccia member. (6) Upper- 

 most beds of fossiliferous tuff member. (7) Coarse granodiorite breccia, sep- 

 arated from (8) by an unconformity. (8) Tuff-breccia member. (9) Grano- 

 diorite. (10) Unconformable mantle of alluvial debris, dipping toward basin. 

 (After Baker.) 



this area. It is perhaps desirable to give a distinct formation name 

 to each of the five divisions, but a more intimate knowledge of the 

 geology of this region must be obtained before the divisions are all 

 recognized as representing more than local phases of the series. A 

 more complicated history for the beds of this section than that now 

 known may yet be demonstrated. 



The lowest or Basal Breccia member in the south limb of the 

 Barstow Syncline rests upon the eroded surface of both granodiorite 

 and a basic andesite or acid basalt. The Basal Breccia contains frag- 

 ments of the rocks below it. The fragments are mostly angular or 

 subangular. The rocks of this member evidently represent a type 

 recently designated as fanglomerate by A. C. Lawson. 19 This division 

 is at least several hundred feet in thickness. 



is Univ. Calif. Publ., Bull. Dept. Geol., vol. 7, pp. 325-334, 1913. 



