154 



University of California Publications. 



[Geology 



northeast canon of Pranktown Creek. The second lies between 

 this canon and the important east-west line that bounds Washoe 

 Valley on the south ; the third occurs between the second and 

 the northeast-southwest fault at the southwest corner of Washoe 

 Valley. The fourth block lies to the south of the third, and may 

 be considered as extending to the south limits of Little Valley. 

 Block 1 has been relatively elevated and a part forced westward. 

 Block 2 is lowest of all. Block 3 has suffered differential eleva- 

 tion, with tilting to the north and a movement of its south end to 

 the eastward. Block 4 has likewise suffered differential eleva- 

 tion, with a partial rotation of its north end to the east. This 

 differential elevation has been effected not by tilting but by a 

 series of step faults, with maximum rise at the south end. The 

 peculiarities of the floor of Little Valley have been described, 

 but a few of these need emphasis. An east-west section across 

 the valley just north of Franktown shows the plateau surface 

 extending unbroken to the foot of the high west scarp. The val- 

 ley structure here consists of but the one main north-south fault, 

 and a true valley does not exist. From this point south two 

 faults diverge, the main one at the base of the high west scarp, 

 and the other at the base of the comparatively low scarp on the 

 east of the valley. The latter scarp is not continuous, but some- 

 what broken and irregular, due to the broken condition of the 

 low east ridge itself. Furthermore, on the west side of this 

 northern block there appear not one but two lines of longitudinal 

 movements, as described before. 



It is next to be noted on the map that the point at which the 

 plateau remnant touches the foot of the high west scarp is just 

 south of an east-west fault crossing block 1. South of this fault- 

 line the sub-block has moved westward, and it is the northwest 

 corner of this sub-block forced against the west scarp that has 

 made the juxtaposition of this topographic element and the 

 plateau remnant. From this point the two main fault-lines di- 

 verge for about a mile, when they become approximately parallel. 

 Block 1 ends at the canon of Franktown Creek. Along this fault- 

 line the physiography indicates that the north side has moved 

 relatively to the west and upward. The floor of north Little 

 Valley, between the divergent fault-lines, is characterized by the 



