t)IKES ALONG COAST WEST OF SANTA CRUZ 249 



a rough and pitted appearance b}^ the leaching away of one or the other 

 sets of these layers, at some places the brown proving the softer, while at 

 others the gray layers are the softer. Some of the sand layers have a 

 very faint bituminous odor, but the intrusion for the most part is free 

 from that substance. 



Near the base of the intrusion and at its east side is a large included 

 fragment of diatom shale. The sand layers slope toward the center of 

 the exposure, forming a trough, with a smaller trough at the west side, 

 as shown in figure 17. Figure 2, plate 30, is from a photograph of the 

 central portion of the exposure, and shows the la3^ered structure of the 

 dike. The diatomaceous shale at the east side of the dike dips 15 degrees 



m;^£^;___^_______^^__^^ 



East 



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:5. 



- DIATOM SHALES ^..^--y : ^yy,:y/y^/<>^^^^ 



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Figure 17. — Diagram Showing Structure of Dike 52. 



This dike is just north of the mouth of Respini creek. 



south, 50 degrees west, while that at the west side dips 15 degrees south, 

 30 degrees west. 



The structure exposed in the cross-section of dike 52 (figure 17, and 

 plate 30, figure 2) is such as would be exposed by a vertical plane cutting 

 a mass of sand which had been deposited by a current of water or pe- 

 troleum coming up from below ^ and depositing its burden of sand in 

 layers at the angle of repose if the plane were to cut the mass at one side 

 of the vertical channel through which the sand and liquid medium came. 



It is believed that this is the ex])lanation of the remarkable sand mass 

 at 52. It should be noted that 52 is but a hundred yards from the large 

 intrusion at 51, with which it is probably connected, the connection 

 being concealed by the sand which covers the space between the two 

 dikes at the mouth of Respini creek. 



Dike number 57 is about 200 yards southeast of the mouth of Scott 

 creek, 13 miles west of Santa Cruz. It is the westernmost dike that has 



* In this connection the remarks of M. Van den Broeck concerning " le Boulant " are of interest. 

 Bulletin de la Societ6 Beige de Geologic, etc., Bruxelles, tome xv, 19(H, pp. 149, 150. See also: 

 Quelques experiences sur I'lmbibition du sable par les liquids et le gas, par W. Spring. Ibid., 

 tome xvii, pp. 13-33. 



