DIKES XEAK SAXTA CRUZ 



239 





r--^^- 





Near the middle of the south side of the Point quarry is a thin dike 

 fvhich branches and cuts the overlying shales in an interesting manner. 

 Its base is connected with the underlying sandstone from which it is 

 evidently derived; in thickness it varies from a thread to a thickness of 



about a foot, and it 



penetrates the shale 

 for 30 feet. 



In figure 7 a por- 

 tion of this dike is 

 represented, though 

 the top of it is not 

 shown. 



In figure 8 a dike at 

 the west side of Point 

 quarry is shown. At 

 this place the lower 

 layers of the overly- 

 ing shale have been 

 broken down and the 



FiGUBE 2,.— Intrusion of Bituminous Sand in Diatom Shales. 



'i'he view is at the west side of the Point quarry (24, figure G) of the 

 City Street Improvement Company, near Santa Cruz, California. 



fasf 



sands have been pushed up behind them. The derivation of this in- 

 trusion is obvious from its relations to the overlying shales and its con- 

 nection with the underlying bituminous sands. 



At the north end of Point quarry (25, figure 6; a large intrusion cuts 



the shales at angles 

 varying from to 90 

 degrees. The main 

 part of this dike, 

 X-Y, is about 6 feet 

 thick. The top of the 

 vertical portion. A, is 

 about 4 feet thick. 

 The dike reaches the 

 surface at A, and its 

 bituminous matter 

 has been leached out, 

 leaving more or less 

 barren sand and de- 

 In going down from A to Y. the sand 

 bituminized. The main bodv of the 



Figure 9. — Dike 25, at North End of Point Quarry. 



bris in the fissure at that place. 



becomes more and more highly 



dike, A-F, is quite highly charged with bitumen. 



At 1, 2, 3, 4, 5 in figure 9 are inclusions of diatomaceous shale in the 

 sandstone, while at 6-7 the dike has apparently been slightly faulted. 



