NONCONFORM ITY BELOW THE CIIICO. 193 



ceue seems as strictly conformable with the Tcjon as is this with the Chico. 

 So, too, along the flank of the Sierra Nevada, both Chico and Miocene re- 

 main almost perfectly horizontal. Had there bjen a great upheaval, accom- 

 panied l)y intense nu-tamorphism, between the IVjou and the Miocene, it 

 seems impossible that no Chico or IVjon strata should have been found 

 metamori)hosed. 



This indirect evidence alone would seem sufficient to establisli the fact 

 of a non-conformit\- between the close of the Knoxville and the beginning of 

 the Chico. Add to this the direct evidence at New Idria and Ft. Ross, and 

 tlie courlusion api)oars irresistible, irrespective of the paleontological argu- 

 ment, which, again, of itself would have sufifiaed to lead to the same result. 



Tlie paleontological argument for a non conformity between the Knox- 

 ville series and those which are found succeeding it may be very briefly 

 stated. Dr. White regards the fauna of the Knoxville group as lower Neo- 

 comian, or at any rate as not later than this. The Chico, in his opinion, rep- 

 resents the very latest portion of the Cretaceous formation. The exposures 

 at Mt. Diablo, for example, show that there, at least, no deposits now inter- 

 vene between the Knoxville and the Chico. Hence, tlie Knoxville beds at 

 this locality must have been above water in the interval. If this interval 

 had been a short one, the fticts could be explained on the assumption of a 

 mere, gentle oscillation of sea-level relatively to the land, and the non-con- 

 formit}^ might be one of erosion, or, in other words, would not necessarily 

 imply a movement of great structural importance. But the Knoxville beds 

 must either have been above water during the entire interval preceding the 

 Chico or during a sufficient part of it to allow of the removal by erosion 

 of any strata deposited subsequent to the close of the Knoxville. If one 

 supposes denudation to be as rapid as sedimentation, which could hardly 

 be the case with the class of sediments composing the Coast Ranges, the 

 region of Mt. Diablo must have been above water for at least one-half of 

 the interval between the close of the Knoxville and the beginning of the 



Marcou iu bis paper ou geological classificatiou, 1883, p. 49, asserts that there is a great break between 

 the Tejon and the Miocene near Ft. Ti^jou. In the description of the locality to which he refers (Ann. 

 R.-pt. Geog. Surv. West of the 100th M., 1876, p. 167), 1 find no mention of this non-conformity. In the 

 text I am concerned to show only that there was no disturbance at this epoch great enough to corre- 

 spond to the metamorphism. 



MON XIII 13 



