niLLS :noeth of bumboldt riveei. 737 



a southeast direction until what would constitute the western side of the 

 anticlinal is thrown into apposition with the axis. The necessary crum- 

 pling which would result from the originally folded condition prior to the 

 faulting would make the southern end of the range complicated enough by 

 itself; but it is rendered still more difficult to read by great local changes 

 of metamorphism, and masked by the overlying masses of Tertiary rhyo- 

 lites and basalts, which break out along the lines of greatest weakness, and 

 wherever the strata plunge rapidly downward. 



Hills north of Humboldt River. — ^North and Avest of where the Hum- 

 boldt River makes its great bend to the south, and intermediate between the 

 Havallah and Montezuma Ranges, lies a group of disconnected mountain 

 masses separated by low depressions, which are occupied by Quaternary 

 accumulations largely made up of drifting sands. These sand-beds are 

 frequently of such an extent as to cover large areas and to foim elevated 

 dunes, more or less concealing the lower hills of the earlier uplifted strata. In 

 general, the mountains present much the same geological appearance, with 

 the same stnictural features, consisting of a nucleus of crystalline rock, 

 against which rest unconformably a mass of uplifted slates with interstratified 

 sandstones and limestones like the Jurassic slates of the Pah-Ute and West 

 Humboldt Ranges. The prevailing dip is to the northwest, away from the 

 course of the river; a number of recorded strikes and dips indicating from 

 the southern end of the Eugene Mountains a gradual curving of the strata 

 more and more to the northeast, until at Winnemucca Peak they strike a 

 few degrees north of east, still dipping to the northwest. Structurally, 

 therefore, they strike and dip quite unlike the north and south ranges south 

 of the river, and doubtless are the determining cause of the great bend 

 formed by the river, which wraps closely around the abrupt slopes of the 

 Triassic uplifts. 



From this region no organic remains have as yet been collected to aid 

 in identifying the strata, and as the continuity of beds with the ranges to 

 the south cannot be clearly made out, their reference to the Jurassic is based 

 entirely upon lithological comparisons. 



Winnemucca Peak. — The mountain mass of Winnemucca Peak is made 

 up of highly metamorphosed blue limestones, seamed with white calcite, 

 47 D G 



