8 



University of California Publications. [Geology 



unaltered and metamorphosed intrusives of the Bedrock Com- 

 plex and rhyolite and hornblende andesite of the Superjacent 

 Series are represented. The bedrock is limestone and granite, 

 the latter being present in the lower half of the ridge and consti- 

 tuting the dominant rock. 



A few gold and copper bearing veins occur in the southeast 

 corner of the area of the map PL 1. 



Tertiary beds which yielded fossils are exposed at the eastern 

 base. Their exposure is not within the map, but about two miles 

 east of it, and about two-thirds of the distance from the top. 

 Their base is fine white rather sharp sandstone, and their top is 

 conglomerate, with well rounded pebbles. The intermediate 

 sandstone contains some hornblende and the pebbles are abun- 

 dantly rlryolitic. There is also a yellowish and whitish stratum 

 of chalky appearance. No test was made upon it to ascertain 

 its composition, either chemically or mineralogically. The 

 thickness of these beds was estimated to be twelve hundred feet. 



Figure 1.— Profile of a portion of Whirlwind Mountain along the line 

 £-F in PI. 2. The prominence on the right is a basaltic cap on sandstone. 

 Along the broken line this sandstone rests on rhyolite, which rises to a pyra- 

 mid on the left. 



Whirlwind Mountain. — This ridge is shown on PI. 2. It is 

 made up of rhyolite, sandstone and a basalt cap, all being of the 

 Superjacent Series. The relations of the basalt, sandstone and 



