DIKES ALONG COAST WEST OF SAXTA CRUZ 245 



waves, which have cut it back 20 or 30 feet into the shale, forming a 

 trench 5 or 6 feet across. 



A short distance west of 40 at 41 is an intrusion of soft sandstone, 

 brown at the top and 3^ellowish green with peculiar diagonal, slightly 

 faulted bands at the bottom. It is 6 feet thick at the bottom, 8 feet 

 thick at the top, and reaches to tlie top of the cliff, which is only 18 feet 

 high at this place. This intrusion is softer than the adjacent shales, and 

 since it is in an exposed position the waves have worn it back through 

 the shales for a distance of 40 feet, leaving an open trench. The surfaces 

 of the sandstone and the shales where these come in contact are smooth 

 and sharpl}^ defined. 



The diagonal banding is indistinctly shown in the lower part of the 

 dike in plate 27. The dark bands that pass across from the lower right 

 hand corner upward and to the left are slightly bituminized. These 

 bands are from 1 inch to 2 inches thick, from 4 to 6 inches apart, and are 

 themselves broken by a series of small faults. The fault planes cut the 

 bands at right angles and run off at angles of about 45 degrees to the 

 hanging wall of the dike. 



The lower half of the intrusion is slightly bituminized, especially 

 along the diagonal bands, while the upper part is free from bitumen, 

 possibly because it has been more weathered than the lower part. 



Immediately west of 41 is a two-foot intrusion of soft, slightly bitumi- 

 nized gray sandstone which extends to the top of the bank. It contains 

 shale inclusions and bands of sand that are more highly bituminized 

 than the mass of the dike. 



Figure 2, plate 26, shows the way in which the waves have cut the 

 sand of this intrusion out from the shale which inclosed it. The shale 

 here has a dip of from 12 to 20 degrees to the west. The intrusion is 

 vertical and trends north 25 degrees east. 



At 43 are a number of thin vertical stringers along a fractured zone, 

 cutting from the bottom to the top of the sea cliff, which is about 50 feet 

 high at this place. At 44, 45, 46, and 47 are small intrusions of soft, 

 brown, fine grained sandstone, dipping about 50 degrees south, 65 degrees 

 east. 



At 48 is a vertical intrusion made up of two more or less lens-shaped 

 parallel parts, which are united a little less than half of the way to the 

 top of the exposure. The lenses, which vary in thickness from 1 to 10 

 inches, thin down and disappear before the top of the cliff is reached. 

 This dike is composed of soft, gray, unbituminized sand and contains 

 inclusions of shale. Figure 15 is a diagram of this dike. 



At 49, in a cove just northwest of 48, is an intrusion of soft, yellowish 

 gray and brown sandstone. The sand mass is exposed for 225 feet along 



