Geol— Vol. II.] ANDERSON— CRETACEOUS DEPOSITS. 55 



Lower Chico, lying as they do near the low coastal border 

 of a large area of Knoxville which has been uplifted by this 

 intrusion, accords well with the unconformity which else- 

 where exists between them. 



On the other hand, the Chico beds, representing the 

 great overlap succeeding these intrusions, are known in 

 many cases to rest directly upon masses of serpentine in 

 an undisturbed position. This is particularly true in north- 

 ern California. Near Yreka, Siskiyou County, a belt of 

 serpentine and peridotite crosses the country in a south- 

 westerly direction, passing beneath the town. At a dis- 

 tance of one to three miles on either side of the town are 

 to be seen the fossiliferous and unaltered beds of the 

 Lower Chico, resting in nearly a horizontal position upon 

 the serpentine. Other similar occurrences have also been 

 noticed. South of Weaverville, in Trinity County, the 

 Lower Chico occurs, and appears to have some similar 

 relation to the serpentines lying to the north. Similar facts 

 have also been noticed in the southern Coast Ranges. 



Thus every class of evidence required to fully demonstrate 

 the post-Knoxville disturbance seems to have been satisfac- 

 torily shown to exist. Not only have the Chico deposits 

 been found resting unconformably upon the Knoxville, but 

 the Horsetown is evidently absent from wide regions in 

 which both of the other members occur; and at the same 

 time copious masses of eruptive rocks are found exactly in 

 the position to coincide with the intervening disturbance and 

 accordingly with the unconformity between them ; and it 

 has also been shown that beds of the Lower Chico rest in 

 an undisturbed position directly upon areas of the same 

 intrusion. 



Vn. Correlation of Deposits. 



Without attempting to settle the difficult problems of 

 correlation, there are a few observations that may be made 

 relative to results that are not beyond the range of data 

 already known. For distant and unrelated provinces pos- 

 sibly no correlation will ever be attained that is entirely 

 satisfactory; and that is not the aim of this paper. 



