300 University of California Publications. [Geology 



bility was, however, not supported by the facts observed in the 

 course of detailed mapping. It was found for example that 

 there was no trace of a basal conglomerate or even of an arena- 

 ceous formation at the contact with the monzonite, such as 

 would have been expected had the Devonian rocks been depos- 

 ited in a sea transgressing a subsiding Archaean terrane of this 

 character. It was found further that the stratification planes 

 of the rocks nearest to the monzonite were not parallel to the 

 surface of the latter but were in several instances in striking 

 discordance with the locus of contact and appeared to abut 

 directly upon it. It became, moreover, very apparent that the 

 monzonite was in direct contact with quite different and widely 

 separated stratigraphic horizons. For example, the monzonite 

 appears, in quite satisfactory exposures on the west and south 

 sides of Weary Flat, to be in direct contact with both the White 

 Pine shale and the Nevada limestone ; and it appears to be 

 transverse to the entire thickness of the first named of these 

 formations. As such observations multiplied, it of course be- 

 came evident that the original hypothesis was entirely at fault, 

 and its rejection cleared the way for the adoption of the hypoth- 

 esis that the monzonite is an intrusive mass of later age than 

 the rocks with which it is in contact. The facts which served 

 to overthrow the first hypothesis are quite in harmony with, 

 and indeed, strongly support the second. They do not, however, 

 establish its correctness beyond question ; for there is still a third 

 hypothesis with which the same facts are not inconsistent. It 

 is possible that the relations subsisting between the monzonite 

 mass and the sedimentary rocks, in so far as they have been 

 described are due to complex faulting. The monzonite area 

 may be bounded by faults. The absence of the lower part of 

 the Palaeozoic section and of a basal conglomerate, the abutment 

 of the sedimentary beds at widely separated horizons upon the 

 monzonite mass, might all be brought about by faulting. As 

 between these two hypotheses, of intrusion and of faulting, the 

 field evidence distinctly favored the former. At the contact of 

 the monzonite with the White Pine formation the shales are 

 altered to a hard bluish hornfels which is in marked contrast 

 with the shales at a distance from the contact. The limestone 



