680 DESCRIPTIVE GEOLOGY. 



In the eastern member of the synclinal, irregular dips, twists in the 

 strike, and all manner of local short flexures are observed in the calcareous 

 shales and blue slates, which, however, have a general western dip. At their 

 eastern base, to the south ot the Emigrant Road, there is a tabular outcrop of 

 black, vesicular basalt, which is highly cr3^stalline, and contains unusually 

 large cavities, which sometimes reach two inches in diameter. The western 

 member of the synclinal presents the same features- of local contortion and 

 irregular metamorphism, but has a prevailing easterly dip, with a strike 

 about 15° to 20° east of north. The rocks of this series are best seen in the 

 canon of the Humboldt River between Iron Point and Golconda Stations. 

 Here they dfp at an angle of 45° to the eastward, and cross the canon 

 diagonally, so that it is difficult to make an accurate estimate of the thick- 

 ness exposed. The lower beds are fissile shales, generally of yellowish 

 color, much stained by iron, of which there are about 500 feet in thickness 

 exposed at the eastern mouth of the canon. Above this are 50 feet of blue, 

 earthy limestones, seamed with veins of white calcite. These are succeeded 

 by 150 feet of partly calcareous, iron-stained shales, wdiich are overlaid by 

 1 00 feet of black, compact limestone, and succeeded by another series of 

 shales and other blue limestones, whose thickness could not be determined. 

 No fossils were found in these beds ; but, from their lithological character 

 and position, they undoubtedly represent the Star Peak Triassic. Their 

 general dip is 45° to the eastward. They are underlaid in the hills to the 

 north of the river by greenish clay slates, very much contorted, to a thickness 

 of several hundred feet,^ below which is 1,000 feet of greenish-white 

 quartzite, in compact, heavy strata, referred to the Koipato series. 



These q^iartzites are covered on the western flanks of the range by 

 broad, tabular flows of basalt, which slope gently to the westward. In the 

 broady open valley to the west of these hills are occasional outcrops of basalt, 

 which, near the mouth of the Little Humboldt River, just east of Winne- 

 mucca, form a little canon, through which the river flows before it joins the 

 main stream. This rock is a rather porous, crystalline dolerite, having some- 

 what of a reddish tinge, and normal composition, together with numerous 

 small crystals of olivine and magnetite. To the naked eye, it seems to be an 

 entirely crystalline mass, but an examination with the microscope shows a 



