434 University of California. [Vol. 2. 



Analyses of Basalts. 





I. 



II. 



III. 



IV. 



V. 



VI. 



Si G 2 



Ti 2 



48 0^ 

 trace 

 21.81 

 2.25 

 6.04 

 trace 



9-15 

 6.11 

 4-58 

 .44 

 •33 

 2.16 



^0.77 



.28 



TO AO 



4- 43 



5- 59 



48. IO 



A 7 ft T 



4/.ou 



cS if 

 D°'/ D 



trace 

 19.40 



1-43 

 4.09 

 trace 

 5-44 



3- 55 



4- 38 

 1. 10 



•25 



1.96 



Al 2 O 









Fe 2 U 3 ... 

 Fe O 















Mn O 









Ca O 



9.81 



5-25 

 2.64 



•30 



.18 



f i.3o@no° 

 I -4i ig- 









Mg O 









Na 2 O . 









K 2 O 









p 2 o 5 









H 2 O 

















Total 



100.90 



100.36 









100.37 











Sp- g 



2.82 



2 79 



2.83 



2.88 



2.80 



2.67 



I. First basalt above Siestan formation % ml - S. F- of Grizzly Peak. 

 Analyst, Palache. 



II. Basalt Quarry E. of Pie Knob. Analyst, Blasdale. 



III. Summit of Bald Peak. Analyst, Palache. 



IV. Basalt of Frowning Ridge escarpment beneath Grizzly Peak andesite. 

 Analyst, Palache. 



V. Basalt of Frowning Ridge escarpment beneath first rhyolite tuff. 

 Analyst, Palache. 



VI. Average of three analyses of andesite I, II, III. See p. 426. 



THE PYROCLASTIC KOCKS. 



The pyroclastic rocks of our field fall into two general classes, 

 viz., (1) light-colored tuffs and agglomerates of rhyolitic composi- 

 tion generally fairly free from ordinary detrital admixtures, and 

 (2) darker-colored tuffs, generally decomposed and associated with 

 or admixed with detrital material. The latter tuffs are basic in the 

 sense that they contain no quartz fragments, but it is not clear in 

 most cases whether they should be ascribed to basaltic or to ande- 

 sitic eruptions. The rhyolitic tuffs are found chiefly in the Lower 

 Berkeleyan and in the Campan basins, while the more basic tuffs 

 occur at more numerous horizons in both Upper and Lower Berke- 

 leyan and in the Campan. A few words of description are here 

 given of these two classes of tuffs to supplement what was said of 

 them in speaking of their field occurrence. 



/ 



