EXPLANATION OF PLATE 46 



Fig. 1. Looking west from the divide in the "Pass" on road between 

 Sutter City and West Butte. The "Pass" is cut in the soft tuffs of the 

 Sutter formation. The hills in the middle ground are composed of the 

 Sutter formation and possibly Tejon and Chico strata also occur here. The 

 hill on the right is a rhyolitic neck. The slope of the outer rim of the 

 andesitic lava flow is seen in the hill on the left. 



Fig. 2. A view showing the geological relations of the Sutter formation 

 to the overlying andesitic lava flow and the underlying Chico. West Butte 

 is the high peak on the right. The peak in the center is a rhyolitic neck 

 surrounded on all sides by the Sutter formation. The even sky-line on the 

 left is due to the gently dipping andesitic lava flow, the outer rim of the 

 old volcano. The steeply clipping westward strata on the left are Chico 

 rocks and their mantling cover is the tuffs of the Sutter formation which in 

 the hill just west of West Butte clip ten degrees west. The Tejon shales 

 outcrop at a point to the left of the picture. 



[524] 



