GEOLOGY OF THE EUREKA DISTRICT. 



By Arnold Hague. 



CHAPTER I. 



GENERAL DESCRIPTION. 



The Eureka District is situated on the Nevada phiteau in the central 

 part of the state of Nevada, midway between the ])asin of Lake Lahontan 

 westward and the basin of Lake l^()nne\nlle eastward. The area covered 

 by the geological and to])ographical survey embraces a region t)f coimtry 

 20 miles square, lying partly in the county of Eureka and partly in the 

 county of White Pine. 



The meridian of 116° west from Greenwich passes just westward of 

 the center of the examined area, and the 39° 30' parallel of north latitude 

 crosses Ruby Hill, the seat of the present activity in precious-metal 

 mining. 



Nevada Plateau.— Ou the Nevada plateau the bi-oad central north and 

 soutli valleys, lying between meridional mountain ranges, reach an aver- 

 age altitude of (i,00() feet above sea-level, the country falling away grad- 

 ually on both sides till at Salt Lake, in Utah, the altitude is 4,250 feet, and 

 at Carson and Humboldt Lakes, in Nevada, 3,<S00 feet above sea level. 

 These valleys, however, com[)ared with those of the depressed areas adjoin- 

 ing the plateau, are relatively narrow, with few marked exceptions, seldom 

 measuring more than 10 or 12 nules in widtli. In general the broader 

 phvsical features of the Great Basin ranges are much the same all the way 



