118 &E0LOGICAL HISTORY OF LAKE LAHONTAN. 



All tlie structures in this group were formed mainly by currents from 

 the south, which swept along the lake shore, carrying shore drift with them, 

 and were deflected from the land upon arriving at the place where deposi- 

 tion had been initiated. This is shown not only by the curvature of the 

 terraces as they approacli the bars, but also by the fact that the structures 

 are mucli the steeper on the north side. 



In these beaches and embankments, as in those at Buffalo Springs, two 

 clearl}^ defined divisions may be seen, which are of different age. The 

 long bar projecting into the valley and marked with the numbei's 95 to 100— 

 indicating depth of water in feet at the highest stage of the former lake— is of 

 older date than the group of V-shaped structures at a higher level. 



The main embankment has a broad, smooth top, which is covered in 

 places with lithoid and dendritic tufa, and is partially coated, especially on 

 the sides, with fine lacustral sediments. Below the point marked with the 

 figures 190, there is a steep scarp nearly a hundred feet high, from the base 

 of which the bar continues on in the same direction as at the higher levels, 

 but is more deeply covered with sediments, and finally becomes so com- 

 pletely inclosed that its presence is only indicated by the rise of the lacus- 

 tral beds as they arch over the bui'ied structure. The main embankment 

 is thus older than the stages of the lake during which lithoid and dendritic 

 tufa was precipitated, and was formed previous to a high- water period, during 

 which the lacustral beds covering the structure were deposited. 



Considering next the group of v-shaped bars at the north of the main 

 structure, we find that the base of this compound group, so far as is revealed 

 by the topography, is older than the highest portion of the main embank- 

 ment, which was built upon it. The structures that occur from the Lahon- 

 tan beach down to a horizon 75 feet below that level are of later date than 

 the bar which is prolonged into the valley, as is shown by their freedom from 

 both lacustral sediments and tufa deposits. 



The difference in age of the two main divisions of this group thus fur- 

 nishes evidence similar to that presented at the Buffalo Springs locality. 

 The higher structures in each case are the younger. These two groups are 

 the complement of each other, liowever, in the fact that the one at Buffalo 

 Sjjrings was built principally by currents from the north, while the second 



