ANCIKNT ItOCKS. 181 



place fur about one hundred and twenty-five miles, but this is probably 

 for want of exploration, since in some parts of Cache Creek, for example, 

 granite predominates among- the stream pebbles.^ According to Professor 

 Whitney^ the highest portions of the Trinity or Shasta Mountains are 

 granite. Tlie Wallala beds, too, though far from any known outcrop of 

 granite, are in large part granitic conglomerates and the sandstones of the 

 entire quicksilver belt are arcose. I have nowhere met granites along the 

 quicksilver belt which appeared to me to be intrusive. 



Gaviian limestone — 111 tlio Gavilau Raugo, somo sixt}' miles south of the 

 Bay of San Francisco, the lowest sedimentary formation encountered is in 

 part limestone, which at the points examined is extraordinarily crystalline, 

 oftentimes consisting of a loosely adherent mass of imperfect calcite crys- 

 tals. Associated with it are rocks of the Archa^au gneiss type. This 

 occurrence has been very little investigated and nothing further is known 

 of its age. It is possible that it is a member of the Knoxville series much 

 more metamorphosed than usual, but it appeal's to me more probable 

 that it is a remnant of some older formation which has perhaps under- 

 gone repeated metamorphism. For the purposes of this memoir an exact 

 _ determination of its character is not important. 



Before passing to a general characterization of the Knoxville beds, 

 which will be found to be the most important and most interesting in the 

 State of California, it seems best to present tlie somewhat complex evi- 

 dence obtained as to the distribution and affiliations of this series; indeed, 

 it appears hardly practicable to describe it without discussing its chemical 

 and structural relations, unless tlie results whicli I have reached as to these 

 are taken for granted. 



Metamorphism in the Coast Ranges.^ ThroUghoUt the Coast RallgCS of California 



there occur large, irregular areas in a somewhat peculiar condition of meta- 

 morphism, which has been discussed in a preceding chapter. Its prominent 

 macroscopical characteristics are the predomiiiiince of recrystallization, ser- 

 pentinization, and silicification. 



' A very large part of the coantry in this neigbborbooil is covered witb thickets (chaparral) which 

 are practically imijenetrable. 



' Geol. Survey California, Geology, vol. 1, p. 3-2:{. 



