Vol. 4] K iiopf-Tkelen. — Geology of Mineral King. 



259 



carved out in the clay slates, and it is doubtless due to this de- 

 pression beneath the zone of most vigrous erosion that the rocks 

 of this belt owe their preservation. The sides of the trough are 

 occasionally visible, especially upon the cirque walls on the 

 eastern side, and at Silver Lake the contact is revealed to a 

 depth of over 500 feet. The exposure shows that the granite 

 abuts upon the sedimentary rocks in a locally uneven and irregu- 

 lar surface, but one which, in general, approximates vertically, 

 or even inclines slightly to the east. At other points it could 

 be seen dipping to the west. Detailed mapping on the contour 

 sheet shows that the contact planes depart indifferently from 

 the vertical. The fact that the belt becomes narrow on low 

 ground indicates, however, that the planes tend to converge, 

 rather than diverge, with increasing depth. The map shows the 

 close relation between the dimensions of the belt and its internal 

 structure. The great narrowness across the strike and the rela- 

 tively great length are immediately apparent. The correspond- 

 ence between strike and prolongation is complete south of Fare- 

 well Gap, but to the north a divergence sets in, amounting to as 

 much as 20°. In spite of the close accordance between the length 

 of the belt and the strike of the strata, it will be noted that the 

 course of the contact is often dii'ectly across the edges of the 

 schists. Along the entire periphery evidences of the intrusive 

 nature of the granites are abundant, and the various criteria for 

 the discrimination of irruptive contacts are everywhere visible 

 in the form of intrusion breccias, apophyses, marmorization of 

 the limestones, and the formation of hornfels zones. Numerous 

 fragments of schists included in the granites show that the 

 schistification of the series preceded the ascension of the plutonic 

 magmas, and this evidence is in confirmation of the relations 

 found to hold true throughout the Sierra Nevada that the 

 schistosity of the invaded formations is independent of the con- 

 tact planes, and was not produced by the intrusive igneous 

 rocks.* 



The post-granitic invasion of the sedimentary series on 

 Monarch Creek by the tonalitic magma has produced a deep 

 * Turner, however, cites an exception from the Bidwell Bar Quadrangle. 



