194 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. 



Chico. Now this interval is an enormous one, comprising nearly the whole 

 of the Cretaceous period. 



The Chico represents only a small portion of the Cretaceous, yet its 

 sediments are thousands of feet in thickness. The same is true of the 

 Wallala, which represents a different portion of the Cretaceous. On the 

 most unfavorable supposition, therefore, Mt. Diablo must have been ex- 

 posed for a sufficient time and at a sufficient elevation to allow of the ero- 

 sion of thousands of feet of strata between the Knoxville and the Chico 

 periods, thus indicating- not a gentle oscillation, but a great uplift. 



Applied to the quicksilver belt in general the argument is less precise 

 and indeed negative; for, while an enormous interval of time elapsed be- 

 tween the epochs at which the Knoxville and Chico faunas flourished, it 

 might be possible to find other intermediate groups as well as the Wallala. 

 To account for the conditions except on the theory of a non-conformity, 

 however, it would be essential to find such faunas in beds stratigraphically 

 intercalated between the Knoxville and tlie Cliico, and even such a discovery 

 would not disprove a non-conformity. Now, although the geology of the 

 Coast Ranges has by no means been exhaustively studied, they have been 

 carefully examined at a great number of points by many geologists hold- 

 ing diverse views, and no one of them has ever discovered a trace of fos- 

 siliferous beds stratigraphically intercalated between the Chico and the 

 Knoxville series. It is therefore very improbable that a substantially full 

 series filling the gap between the Knoxville and the Chico exists in any 

 one locality, and much more so that this is the general condition and that 

 Mt. Diablo is merely a local exception. 



The paleontological argument, though negative, is thus so strong as 

 to give to the hypothesis of a great non- conformity between the Knoxville 

 and the Chico a very high degree of probability without any aid from 

 direct observations of non-conformity or from observations on the age of 

 the metamorphosed rocks. 



A similar argument applies, thougli with less force, to the relations 

 existing between the Knoxville and the Wallala, for here, too, a long inter- 

 val is indicated between the eras of the respective faunas; but the relations 

 of the Knoxville and Horsetown beds cannot as yet be thus elucidated, be- 



