NEOCENE STRATIGRAPHY. 347 



of Japan finds similar beds with a similar fauna along- 

 that coast, and reasoning partly from the changes and 

 migrations which have taken place in the fauna, and partly 

 on the non-conformities which the beds there show in 

 places with overlying beds, he assigns them to the Plio- 

 cene period. 



4. THE QUATERNARY. 



The Santa Cruz Mountains are fringed around the base 

 with a belt of nearly horizontal deposits. Topographically 

 these extend from the edge of the foothills to sea-lev^l 

 with a very gentle slope. On the ocean side these de- 

 posits and the older deposits upon which they rest un- 

 conformably have been much eroded by the waves, so 

 that much of the distance the lower part of the slope has 

 been cut away and a vertical cliff is left to mark the ad- 

 vance of wave erosion. See plate xxii. As erosion is 

 strongest at about mean tide level, there are usually 

 numerous reefs exposed at lowest tide. At a few places 

 stacks, sea caves and natural bridges attest the rapidity 

 with which the erosion is progressing. At Point San 

 Pedro erosion has destroyed all trace of this old bench 

 or terrace. The upper edge of this bench, where it meets 

 the mountains or foothills, varies somewhat in height. A 

 study of this variation shows in the case of the Santa 

 Cruz Mountains that it is due to the character of the up- 

 lift, that is, the uplift has not been a general vertical rise 

 of so many feet, but has been strongest in the old axes of 

 uplift, the main ridges of the range. The result of this 

 is that the line of contact with the foothills has an eleva- 

 tion inversely proportional to its distance from the lines 

 of uplift. Thus at the Mussel Rock, the terrace is over 

 220 feet above sea-level. 



^uate7'na'?'y of Mussel Rock. — From Mussel Rock 



