4-02 



University of California. 



[Vol. 2 



tion is towards the fault, as the mapping in Strawberry Canon 

 clearly shows. This trough is cut off, as has been already pointed 

 out, by the important fault in the line of the south fork of Straw- 

 berry Creek, which was probably synchronous in formation with 

 the Canon fault. The effect of these two faults was to drop a block 

 or wedge of the early Campan basin down into the surrounding 

 country. In this fact we have the key to the geomorphogeny of 

 Strawberry Canon; for the diastrophic trough thus formed con- 

 tinued to be a basin of accumulation, and the formations there 

 deposited, as well as those originally faulted, proved subsequently 

 to be much more susceptible to erosion than the rocks of the 

 Shasta-Chico and Monterey series, which hemmed them in on all 

 sides; so that when Strawberry Creek reached them in the normal 

 process of head-water erosion, it rapidly worked out of them a wide 

 amphitheater-like, subsequent canon, while the consequent gorge is 

 still constricted. 



Probable Volcanic Vent. — At the quarry a little north of Such's 

 ranch-house there is a small area of volcanic rocks entirely sur- 

 rounded by a gravel conglomerate. It is about one and one- 

 quarter acres in extent. The quarry has cut into the mass to a 

 depth of about thirty feet, and in the bottom of the quarry there 

 was at one time a well to a depth of about twenty feet. These 

 excavations have revealed very clearly the character of the rock. 

 It is of a mixed character, being partly a vesicular basalt and 

 partly an agglomerate. The two are intimately mixed and the 

 agglomerate blocks are frequently large. The isolated occurrence 

 of the mass and the character of the material strongly suggest 

 that we have here one of the minor vents from which emanated 

 some of the later lavas and tuffs. The more or less open character 

 of the rock has permitted percolation of waters, so that the entire 

 mass is rather oxidized and ocherous. Small seams of calcite also 

 occur in it, and, what is more interesting, occasional deposits of 

 asphaltum in irregular spaces not exceeding a cubic centimeter in 

 size. 



The small area of basalt to the southwest of Such's ranch- 

 house evidently owes its position to the fact of its having been 

 dropped between two converging faults, alluded to above and indi- 



