632 /. E. SPURR 



Daggett or Calico region. — Southward, in the middle of the 

 Mojave Desert, at Daggett, or Calico (which is on the Mojave 

 River and also on the Santa Fe Railway), great masses of 

 rhyolite have been described, 1 underlying the borax-bearing lake 

 beds which are probably, in part at least, Upper Eocene. These 

 rhyolites are plainly the same as those in the Coso Range and in 

 the Randsburg region. 



SUCCESSION OF LAVAS IN THE GREAT BASIN REGION IN GENERAL 



In the field it is evident that the same lavas occur in many 

 different localities throughout the Great Basin region, in much 

 the same relative quantity, having nearly the same mineralogical 

 composition, and giving evidence of about the same relative 

 age. Moreover, where two or more of these lavas are found 

 close together, their order of succession is found to be in 

 general nearly the same, although at any given place certain 

 members of the series may be lacking. In no single locality 

 has the complete succession, as indicated by the correlation of 

 all the different sections, been observed ; but in order to find it 

 we may fill gaps in one place from the observations in another. 

 In correlating similar lavas erupted at different points, we must 

 consider not only the succession but the relative age of each, so 

 far as this is known. The evidence of this age will be briefly 

 outlined later on ; it is with this in mind, however, that the fol- 

 lowing table has been made. Many of the correlations are only 

 provisional, and will probably require adjustment and rearrange- 

 ment as the result of future investigation ; but it is believed that 

 the general deductions are correct. 



By this correlation we see that the succession of lavas seems 

 to have been roughly uniform over the whole region, although 

 minor variations have been numerous at many points. In general, 

 it appears possible to divide the lavas into five groups, in the 

 order of their eruption, as follows : 



1. Acid (type, biotite rhyolite). 



2. Siliceous intermediate (medium andesites). 



*W. H. Storms: Eleventh Rept. State Mineralogist California, p. 347. Sac- 

 ramento, 1893. 



