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University of California Publications in Geology [ VoL 11 



Sauta Ynez Mountains, the sandstone rests on an irregular surface 

 of black shale and contains several blocks of shale, apparently torn 

 from the bed below (fig. 4). 



Fig. 4. Irregular contact of Franciscan sandstone and shale with slabs of shale 



in sandstone 



In certain cases isolated lenses of shale ten to fifteen feet long 

 may show a peculiar disruption as indicated in figure 5. No indica- 



Fig. 5. Broken lens of shale in Franciscan sandstone 



tion of faulting or shearing can be seen in the sandstone between 

 the blocks ; it is as massive there as elsewhere. The only conclusion 

 the observer can draw is that the shale must have been first hardened 

 and then broken up by some disturbance which occurred at a time 

 when the sand, in which it was embedded, was still unconsolidated. 



Veins 



The Franciscan sandstone is in many localities cut by veins of 

 quartz and ealcite, most of them small and many of them very irregu- 

 lar. Their general character is indicated in the photographs (plates 

 1b and 2a). 



At Point Richmond some peculiar veins of quartz were found. 

 The walls of these veins have been impregnated with silica in unusual 

 amount, so that the resiilting rock bordering the vein resembles green 

 chert, save that it contains sand grains. Some of the veins are very 

 narrow, and show very little or no quartz, yet there is an impregna- 

 tion of the wall of the fissure for an inch or more on each side. A few 

 of them show very little evidence of an original fissure, looking like 

 dykes of cherty rock running through the sandstone. At this locality 

 there are great numbers of these veins with silicified walls and irregu- 

 lar branching courses, inclined to the bedding. 



