NEOCENE STRATIGRAPHY. 32I 



from the south, the structure is seen to be anticlinal, so 

 that the beds that make up the foothills run down on the 

 north side of the anticline in the ridge through which the 

 tunnel is cut. The gravelly deposits in Los Angeles give 

 good evidence of being shore deposits, for the gravel 

 seems to to be largely derived from the underlying forma- 

 tion and the boulders are pierced and sometimes almost 

 honey-combed with borings of one of the rock boring 

 mollusks. 



Distribution. — The Merced series, antedating as it did 

 the upheaval which gives the Santa Cruz Mountains its 

 present topographic position, was probably originally laid 

 down over all or most of the region now occupied by those 

 mountains. The upheaval, however, seems to have op- 

 erated largely by faulting, which resulted in some parts 

 having been elevated and exposed to erosion more than 

 others, so that the beds left now were probably under 

 water during the Quaternary and thus preserved, and it 

 is only the post- Quaternary uplift which has exposed 

 them. As we might expect if this theory is true, we only 

 find these Merced series beds on the lower flanks of the 

 mountains probably not over looo feet above sea-level. 

 They are exposed in the bluffs along the sea- coast from 

 two miles north of Mussel Rock to Capitola at least, not 

 continuously, however, for between Mussel Rock and 

 Point Montara, at Spanish Town, and along the stretch 

 north of Santa Cruz this formation is lacking, erosion 

 having exposed the underlying strata or cut down the 

 bluffs. 



How far back into the mountains the Merced series 

 extends was not accurately determined. In Purissima, 

 Lobetas, Tunitas, San Gregoria and Pomponia creeks it 

 was found to extend back at least four or five miles from 

 the coast. 



2d Ser., Vol. V. ( 21 ) August 1, 1895. 



