GLACIATION IX NEBRASKA 495 



"There followed two epochs of high water, with an interval during which 

 the basin was nearly or quite empty. The first of these epochs was at least 

 five times as long as the second. The second scored its water mark 90 feet 

 higher than the first, and would have encroached still farther on the basiD 

 sides had it not been checked by outflow. During the epoch of outflow, the 

 discharging current eroded the rim, and thus lowered the lake 375 feet; and 

 after the outflow had ceased, the water fell by desiccation, with one notable 

 interruption, to its present level in Great Salt Lake. The inter-Bonneville 

 epoch of low water was of greater duration than the time that has elapsed 

 since the final desiccation. 



"The history of the Bonneville oscillations is, moreover, closely paralleled 

 by that of the Lahontan oscillations, and it is believed that they belong to a 

 series of climatic changes affecting not only these two basins, but the adjacent 

 subdivisions of the Great Basin, . . . 



"The moraines of three Pleistocene glaciers descend from the Wasatch Moun- 

 tains to the level of the Bonneville shoreline ; the moraines of four glaciers 

 descend from the Sierra Nevada to the level of the old shoreline of Mono 

 Lake ; and the relations of these moraines to the shores of the lakes and the 

 associated deposits indicate that the maximum stage of the lakes coincided 

 closely with the epoch of maximum glaciation. 



"The phenomena sustain the theory that the Pleistocene lakes of the west- 

 ern United States were coincident with the Pleistocene glaciers of the same 

 district, and were produced by the same climatic changes. It follows as a 

 corollary that the glacial history of this region was bipartite, two maxima of 

 glaciation being separated, not by a mere variation in intensity, but by a 

 cessation of glaciation." 



Comparing the fluctuations of the western lakes and glaciers with those 

 of the North American ice-sheet, we may confidently refer the prolonged 

 first high stage of the lakes to the Xebraskan stage of far extended ice 

 accumulations ; the time when the lakes disappeared under a drier climate 

 is represented by the Aftonian stage of wide recession of the ice-sheet ; 

 and the second rise of the lakes occurred probably during the time of 

 culmination and final disappearance of the icefields. This second great 

 division of the Glacial period included the maximum Kansan and Illi- 

 noian stages and the later Iowan and Wisconsin glaciation, being termi- 

 nated when subsidence of the formerly high ice-covered land caused the 

 continental glacier to be melted away, with the formation of very remark- 

 able terminal and recessional moraines. 



The Aftoniax ixtekglacial Stage 



The present writer, in a paper read at the International Geological 

 Congress in Toronto in 1913, 4 referred the interval between the high 



4 Report of the Congress, published in 1914, pp. 455-466 



