THE SUPERJACENT SERIES 301 



highly crumpled, and commonly faulted and even overthrust. A certain 

 amount of metamorphism is prevalent. The axes of dislocation are 

 rarely greatly but generally distinctly oblique to the range front. 



THE SUPERJACENT SERIES 



General composition and character. — The superjacent series consists of 

 freshwater sediments and of volcanic lavas and tuffs. The latter are 

 distributed widely over the range, where they are sometimes quite thick, 

 while in the valleys they are found only on occasional low hills or ridges- 

 As will be shown later, they have proved of the greatest value in deter- 

 mining the nature and extent of the movements which have given rise to 

 the Humboldt Lake range. The sediments — non-volcanic, lacustral, or 

 fluviatile — are almost entirely confined to the intermontane valleys, and 

 are of interest as possible indicators of the periods at which the various 

 dynamic agents were actfve. 



No marine sediments of later age than the Jurassic have ever been 

 found in these mountains or in any of the surrounding country. 



Sedimentary rocks — Truckee beds. — The presence of strata of the Truckee 

 group was determined at the west base of the mountains, about 3 or 4 

 miles east of Lovelock, where they are exposed in a stream-cut in a 

 terrace situated in front of the range. They consist of slightly consoli- 

 dated granitic sands, diatomaceous earth, etcetera, and dip west at about 

 35 degrees. Basalt overlies them unconformably. There is a straight 

 stretch of valley between them and the type locality at " Kawsoh "moun- 

 tain. No other outcrops were met by the writer. They are, however, 

 reported from the south end of the Star Peak range by the Fortieth 

 Parallel Survey. 



Lahontan beds. — Lake Lahontan* occupied the valleys on both sides 

 of the Humboldt Lake mountains, and the shorelines are traceable with- 

 out difficulty, and terraces, cliffs, tufa domes, pebbles on beaches, and 

 other shore features are common. These phenomena are best developed 

 and preserved where the mountains are low and with gentle slope; best 

 developed because the work of littoral erosion was least burdensome '■> 

 best preserved because the atmospheric and stream influences have been 

 least active since the disappearance of the lake waters. On some low 

 slopes, uncut by drainage lines, 6 or 7 fine long terraces with correspond- 

 ing cliffs can be counted, and seem practically unaltered since they were 

 deserted; but where the main stream lines pass into the valley, great 

 alluvial cones, unnotched by any horizontal lines, extend out for hun- 

 dreds of yards or for miles into the valley. Hard rocks, like basalt, 



* See also Russell : Monograph xi, U. S. Geol. Survey. 



