The Sierra Nevada Range 171 



be referred to as granite, though this is not strictly accurate. 

 The aggregate of these granitic rocks forms a great complex 

 mass which is spoken of in geological literature as the Bed Rock 

 Series, or Basement Complex. 



E. 



After F. E. Matthes, U. S. Geol. Survey 



FIG. 54. Idealized cross section of Sierra block showing the composition 

 of the interior. The folded beds in the foothill belt (A, B) and different 

 points on the western slope (C, C) and on the crest (D) are the remnants 

 of a formerly continuous roof of (mostly) sedimentary rocks. Under these 

 the granitic materials of the great batholith welled up in a molten state. They 

 are the "roots" of the mountain systems that occupied the place of the present 

 range in time past. 



Batholith Confined under Roof of 

 Sedimentary Rocks 



The outstanding fact regarding this granitic batholith is 

 that it is now exposed at the surface of the block over large 

 areas, despite its deep-seated origin. Granitic rocks form the 

 surface almost everywhere in the High Sierra region. Most of 

 the prominent peaks, domes and cliffs are carved from such 

 rocks. Yet it is clear from their crystalline structure that 

 these igneous materials did not flow out upon the surface but 

 cooled very slowly, under the pressure of a confining crust or 

 roof of other rocks. The explanation is that they have become 

 uncovered that they now appear at the surface because the 

 roof under which they crystallized has been in large part re- 

 moved. The slate, quartzite, and limestone mentioned are the 

 materials of which the ancient roof was made. The old roof 

 rocks were originally thousands of feet thick, but in the course 

 of the ages since Jurassic time, they have been gradually worn 

 away. It is thought that as much as 5,000 feet of rock forma- 

 tions have been removed from the great dome of the Sierra 

 range. 



