392 
TURNER. 
retained sufficient water to deposit beds of the character de¬ 
scribed. Moreover, the Mohawk Post Office beds seem to 
continue north and abut against the andesitic barrier. The 
Grey Eagle Creek beds have an approximate elevation of 
4,600 feet, at least 100 feet higher than at Mohawk Post 
Office, to which they are so similar. It is possible the first- 
mentioned beds have attained their present position through 
differential elevation or subsidence, though as the beds at 
both exposures are approximately horizontal this does not 
seem likely. 
The beds from which the leaves came may simply record 
a quiet stage of the former Feather Elver. The river is 
probably now, in fact, depositing similar material in the 
numerous nearly quiet stretches between Mohawk and Sierra 
Valleys. 
Glacial Moraines in Relation to the Lake Beds. 
All about Johnsville are enormous accumulations of 
morainal material. Over an area of fifteen square miles 
none of the underlying formations are exposed, so deep is 
the morainal detritus. This is largely made up of diabase 
.and quartz, porphyrite boulders, and subangular fragments 
from the extensive areas of these rocks in the high ridge to 
the west and southwest, the east and north slopes of which 
formed the neve fields of the glaciers. Mounts Elwell, 
Bunker Hill, and Eureka Peak are prominent northward¬ 
trending spurs of this high ridge, and between these spurs 
the glaciers were nourished. 
The moraines merge into the lake deposits, and opposite 
Jamison, on the east side of Jamison Creek, there is an ex¬ 
posure of the moraine material at the point where the highest 
lake terrace begins. The underlying coarse gravel and sub- 
angular material are roughly stratified. This would suggest 
that the maximum period of the glaciers and that of the 
Pleistocene lake occurred at the same time, for if the water 
had terraced the moraines subsequent to their deposition it 
seems probable that there would be no internal stratification, 
but only a surface leveling of the material. 
