NEOCENE STRATIGRAPHY. 325 



exposed along Seven-Mile Beach. The section is not at 

 right angles to the strike, so that the dip does not appear 

 as high as it is. Some of the dips were 30° N. 9° E., 

 65° N. 9° E., 75° N. 14^^ E., 65° N. 24° E., 60° N. 14" 

 E., 65° N., 65° N. 4° E., 67° N. 4° E., 35° N. 4° E., 

 30° N. 9° E., the line of section varying from S. to a few 

 degrees E. of S. The bearings refer to the true meridian. 

 The section gives a good idea of the upheaval to which 

 these beds with the underl3dng beds were subjected. 



Plate xxiv gives also a section from Lake Merced to 

 Purissima. From this figure it is evident, if our conclu- 

 sions are correct, that the uplift along Seven-Mile Beach 

 is not a local uplift, but is intimately connected with the 

 main recent upheaval, and that we must assign the moun- 

 tains to an age later than the deposition of these beds. 



Where the Santa Cruz Range is cut by the Pacific its 

 structure would appear to be a simple anticline, rising 

 probably more by faulting than by folding, and the dif- 

 ferent ridges due merely to erosion as influenced by this 

 faulting. Thus, as already pointed out, there is a fault 

 of 825 feet downthrow at Wood's Gulch, and evidence of 

 this fault is found in the ravine which heads against 

 Wood's Gulch and flows to the bay. About in this same 

 line there is evidence of a fault in the north fork of Twelve- 

 Mile Creek, and in a cut near the Happy Valley House. 

 Just north of Mussel Rock a fault zone commences and 

 continues to Black Mountain. This is evidently not a 

 single fault, but seems to be a line of fracturing. The 

 contact between the Tertiary and older formations which 

 run southeast from Mussel Rock follows this fault line at 

 least to San Andreas Lake. The bluffs along the north- 

 east side of San Andreas, Crystal Springs and San Fran- 

 cisquito valleys appears to be due to faulting. 



If the streams running from the foothills to the bay be 



