I.AWSUN "I 



palacheJ 



The Berkeley Hills. 



disintegration, is ample evidence of an erosion interval competent 

 to remove not only nearly all of the once extensive rhyolite agglom- 

 erate but also the whole of other formations which may have 

 reposed upon it. 



RELATIONS OF CAMPAN AND BERKELEYAN SERIES. 



Post- Berkeleyan Deformation and Erosion. — It has been shown 

 that the Berkeleyan series of sedimentary beds and lavas occupies 

 a great synclinal trough, with some subordinate parallel flexures. 

 The development of this structure was probably inaugurated at the 

 close of the Lower Berkeleyan, for we have seen that the discrimi- 

 nation between Upper and Lower Berkeleyan is based upon the 

 recognition of the deformation of the Lower Berkeleyan, and the 

 erosion of the beds so deformed before the accumulation of the 

 Upper Berkeleyan beds and lavas upon them. It was, however, of 

 course not till the close of the Upper Berkeleyan that the synclinal 

 structure was fully established, although it was probably in prog- 

 ress of development during the Upper Berkeleyan epoch, as is 

 indicated by the persistence of the trough conditioning the loens of 

 accumulation, and by the somewhat steeper dip of the lower beds 

 as compared with that of the upper. 



Stratigrapluc Unconformity. — The stratigraphic relations of the 

 Campan beds and lavas to this great syncline are clear. The 

 Campan trough is discordant both in strike and dip to the 

 Berkeleyan strata. In simpler terms, it lies across the edges of 

 the Berkeleyan syncline. There is, therefore, an unconformity 

 between the two series. The mere discordance of the beds might, 

 however, be in part explained by the operation of the canon dis- 

 location. A study of the situation shows, however, that while 

 that fault accentuates the discordance, it neither masks nor adds to 

 the true unconformity if properly discriminated from the other 

 structural features. The Caiion fault when it dropped the lower 

 part of the Campan strata against the Berkeleyan, undoubtedly 

 carried down out of range of present observation the northwest end 

 of the Berkeleyan synclinal trough, since the fault cuts obliquely 

 across the axis of the syncline. But since neither the Berkeleyan 

 nor the Monterey rocks appear again from beneath the Campan on 



