92 H. W. FAIRBANKS — GEOLOGY OF THE COAST RANGES. 



the time interval which intervened before the deposition of the lowest 

 Cretaceous, occurred the peculiar chemical metamorphism which is ap- 

 parent in rocks of this series wherever they outcrop. The silicious waters, 

 the circulation and mineralization of which was due to the heat and 

 chemical action existing during the mountain-making movements, per- 

 meated the rocks through the innumerable fissures which the strain had 

 produced. This silicification was more pronounced in those strata suffi- 

 ciently consolidated to be fractured ; less so in the yielding argillaceous 

 ones. As was shown in the sections of jasper, the numberless minute 

 veins are largely formed of chalcedonic silica, and they were probably 

 filled by infiltration from the jasper itself. The large veins in the jasper 

 and all those in the other rocks have been filled from below in the man- 

 ner described. With local exceptions, this silicification can be detected 

 over the whole area occupied by this series from the most southerly out- 

 crop to the northern boundary of the state. As the Cretaceous is free 

 from this chemical metamorphism, even on the slopes of the Yallo Bally 

 mountains, where it is the most pronounced in the older rocks, we have 

 the strongest proof for its having taken place prior to the deposition of 

 the Cretaceous. Moreover, this silicification of rocks known to be older 

 than the Cretaceous in the Klamath mountains is traceable without any 

 break, appearing only in less degree, through the whole extent of the 

 Coast ranges. The lower Cretaceous, wherever it appears in the central 

 and southern Coast ranges, is wholly free from any regional metamor- 

 phism, showing much the same character as on the eastern slope of the 

 Yallo Ball}^ mountains. Everywhere the deformation and metamor- 

 phism was strongly marked when the Cretaceous began to be deposited. 



Correlation of the Quartz-veins. 



It seems probable that the great quartz veins of the Sierra Nevada 

 date from this same time; that is, posterior to the later granitic irrup- 

 tion. In the Sierra Nevada the regularity and size of the veins is due, 

 in part at least, to the comparatively uniform strike and dip of the strata, 

 while in the Coast ranges the extreme irregularity of the stratification 

 made such quartz deposits impossible. Gold-bearing quartz-veins, small 

 and irregular, are to be found from Santa Barbara county north to the 

 rich gold-bearing areas of Shasta county. Small veins have been pros- 

 pected for gold in the canyon of the Cuyama river, in northern Santa 

 Barbara county. In Monterey county, in rocks of the same age, are 

 located the deposits of the Cruikshank mining district. Here are rich 

 but bunchy gold-bearing quartz-veins in crushed sandstone and shale. 

 In many other portions of this county, as well as in San Luis Obispo 



