IDDINOfi.] 



LIVINGSTON TO CINNABAR. 331 



(10,960 feet—3340 m.) The limestone is exposed at the northwestern 



base of Chico Mountain, the main mass of igneous rock having been 

 intruded in shale that lies near the base of the Cambrian deposits near 

 the gneiss. From this point southward to Yankee Jim canyon, and 

 beyond the great mass of the mountains east of the river, is gneiss and 

 schist, upon the ancient surface of which volcanic ejectamenta have 

 accumulated. The extremely uneven character of the gneissio country 

 at the time of the volcanic outbreaks ami the irregularities of subse- 

 quent erosion explain the present geological structure of this part of 

 tin 1 region. 



Emigrant Gulch, near its mouth, cuts 2,000 feet into crystalline schists 

 that are exposed in a low belt around the northwestern base of Emi- 

 grant Peak. Above this andesitic tull' breccia or agglomerate rises for 

 5,000 feet to the summit of the mountain; while on the southern side 

 gneiss rises to within 1.200 feet of the summit. The andesitic breccia 

 at the summit is traversed by dikes of pot phyrite with a general north- 

 west and southeast trend. The more prominent may be seen from the 

 railroad. The breccia has been indurated by the proximity of great 

 bodies of intruded porphyrite which form mountains east of Emigrant 

 Peak, which accounts for its having withstood erosion and having 

 become one of the loftiest peaks in the region. (Fig. L4-B and 0.) 



South of Emigrant Peak. Six-Mile Creek has cut deeply into crystal- 

 line schists and granite. The mountain ridges surrounding its drain- 

 age basin consist of andesitic breccia, tuffs, and lava (lows, which cap 

 the granite at about 7.000 i'eet along the east side of the valley. The 

 crystalline schists are well exposed in the narrow gorge through which 

 the river runs at the southern end of its broad valley, and which is 

 known as Yankee dim canyon. The gneisses cross to the western side 

 of the river, and are overlaid by volcanic lavas, as on the eastern side. 



The cross section of the country through Mount Cowen and Emigrant 

 Peak (Fig. 14-B) exhibits the geological structure of the region just 

 described, winch needs no further comment except to note that the 

 section crosses the faults at the base of Mount Cowen about 3 miles 

 west of where the first section crosses them, and intersects a large body 

 of intruded porphyrite. 



From Yankee dim canyon south for several miles, knobs of chocolate- 

 colored breccia may be seen on both sides of tin; river resting upon 

 gneiss. The light-colored rocks east of the river, opposite Cinnabar 

 Mountain, are mainly decomposed gneiss overlaid by some igneous rocks 

 and cut by dikes of the same. The gneiss has been greatly fractured 

 by joints representing the termination of a profound fault which exists 

 farther south. 



The high mass of Sheep Mountain opposite Cinnabar station is crys- 

 talline schist from base to summit, which is 10,028 feet in altitude. 



