188 QUICKSILVEll DEPOSITS OP THE PACIFIC SLOPE. 



maintained that the violent npheaval and metamorpliisni which followed 

 the Knoxville left the .snpposed older areas nndisturbed. This would con- 

 flict with all analogy. 



The foregoing facts and the necessary inferences from them appear to 

 justify the statement that the silicified and serpentinized metamorphic rocks 

 of the Coast Ranges include a portion of the Knoxville beds, and do not 

 include any portion either of the Chico or of the Wallala series, while if 

 there were pre-Knoxville rocks within tlie metamorphic areas they must 

 have undergone at least a fresh disturbance at the time when tlie Knoxville 

 beds were broken up and metamorphosed. 



Non conformity between the Knoxville beds and the Chico. Had tllG prOof of tllis UOU- 



conformity been a simple matter, it could not have escaped the attention of 

 some one of the able geologists who have worked in the Coast Ranges. 

 The difficulty is in part due to the rarity of fossils in the older groups over 

 a great portion of the area in question, wliich often leaves the observer 

 without absolute proof of the age of the rocks about him; but complexity 

 of structure is the main obstacle. Few geological phenomena are more 

 striking than a non-conformitv where the overlving strata are nearly hori- 

 zontal, the underlying rocks greatly inclined, and tlie exposure tolerable. 

 This combination is rare in the Coast Ranges, and no such case is known 

 where the Shasta and Chico beds meet. The Post-Miocene uplift traced 

 by Professor Whitney has folded, faulted, and broken the later Cretaceous 

 and the Tertiary rocks, as well as the earlier strata upon which these were 

 unconformably deposited; so that it is usually f;xr from easy to make out 

 the effects due to the earlier and later disturbances, respectively, and still 

 more difficult to prove that no explanation except that of a non-conformity 

 beneath the Chico will account for the facts. I believe that the structural 

 evidence to be presented clearly establishes this non-conformity, but the 

 proof, though convincing, is less abundant than could be wished. The 

 evidence will first be presented from a purely structural point of view and 

 will then be re-enforced by an independent, paleontological argument. 



In the neighborhood of the New Idria mine the metamorphic rocks 

 have been greatly disturbed, while the Chico strata, though tilted at a high 

 angle, are remarkably regular. Owing to the steepness of the contact, how- 



