1914] Buwalda: Tertiary Mammal Beds in West-Central Nevada 339 



The limestones and intercalated shales have been subjected to 

 intense deformation ; they are closely folded and are often intensely 

 crumpled. Small faults and slickensiding due to minor displacements 

 are common. The rock has also been minutely fractured in ^very 

 direction, and thin veins of calcite and quartz have filled these frac- 

 tures, giving the limestone a netted appearance on weathered surfaces. 

 General anticlinal and synclinal structures can still be plainly seen 

 in some of the larger areas. The axes of these structures lie obliquely 

 across the general trend of the present range. The angular divergence 

 in Cedar Mountain is usually forty-five degrees or greater; in some 

 cases the structural axes appear to lie at right angles to the present 

 range trend. Occasionally, in a view of the bolder parts of the range 

 from the valley, one may see these great arches and troughs of crum- 

 pled rocks in section. This divergence in orientation of the earlier 

 structural axes from the trend of the present range is similar to that 

 recorded by Professor Louderback 2 for the West Humboldt Range 

 lying about one hundred miles to the north. 



The limestones lie with marked unconformity below the lavas and 

 the lake-beds. They were intruded by the granular rocks of the range. 

 The evidence for this is their areal relation to the granular rocks, the 

 presence of considerable areas of marble lying in contact with the 

 granular rocks and grading into the limestones, and contact meta- 

 morphic minerals developed in the limestones near the contact. 



The age of the limestones was not ascertained from palaeontologic 

 evidence, the fossils obtained from them not being determinable. The 

 strike of these rocks would indicate, however, that they were once 

 areally continuous with the limestones in the northern Pilot Range, 

 some ten or twelve miles away, across Stewart Valley, in which Mr. 

 H. W. Turner 3 collected fossils determined by Professor J. P. Smith 

 to be of Jurassic age. 



The intense deformation of the limestones and the intrusion of the 

 granular rocks occurred, therefore, at the end of the Jurassic or in 

 post-Jurassic time, and was probably contemporaneous with the intense 

 deformation and intrusion of rocks of approximately the same age in 

 the Sierra Nevada seventy-five miles to the west. 



2 Louderback, G. D., Basin Eange Structure of the Humboldt Region, Bulk 

 Geol. Soc. Am., vol. 15, p. 300, 1904. 



3 American Geologist, vol. 27, p. 132, 1901. 



