444 H. L. FAIRCHJLD— GLACIAL GENESEE LAKES. 



as the eastern or Ontario end of the Laurentian depression was filled with 

 ice. At the time which ayc have now reached in this history of the 

 Genesee valle}'' the Warren waters had forced their Avay eastward as far 

 as western New York. The heavy beaches have been traced ah)ng the 

 south side of lake Erie northeastward to Alden and Crittenden, west of 

 Batavia, where they have an altitude of 860 to 865 feet.-'^ 



During the seventh stage the Genesee waters had been draining over 

 the \ve.:jtern border of the valley into the Warren waters and gradually 

 approaching the level of the latter. Finally, when the western border of 

 the Genesee valle}' was uncovered down to about 860 to 870 feet, the 

 Genesee waters blended with lake Warren. This required the desertion 

 by the ice of the point of high land reaching north to Batavia. A termi- 

 nal moraine east and west of Batavia indicates a considerable lingering 

 of the ice-front at this line, but with the retreat of the ice the Warren 

 waters invaded the Genesee valley and spread far eastward. 



The lower Genesee valley was flooded U[) to an altitude as high or 

 higher than the beaches west of Batavia (865 feet). Tlie waters extended 

 up the vallc}'' as far as Mount Morris, where tlie river at its deljouchment 

 built a delta in the lake. The Dansville valley was also Hooded, and 

 indeed the Warren erosion and delta planes are to be found tiiroughout 

 the region between 850 and 900 feet altitude. 



There remains much uncertainty as to the eastward extent and alti- 

 tude of lake Warren. Many phenomena have been noted and strong 

 erosion planes found as far east as Ontario county, but a systematic study 

 of the Warren phenomena has not been made in this region, and further 

 discussion will be reserved for a future paper. 



When the Genesee waters fell to the Warren level a morainal lake was 

 left in the new portion of the river valley above Mount Morrisv and the 

 rock-cut at the '' high banks " was begun (see page 450). 



During the stage of Warren waters the low ])lain of the Salina and 

 Niagara terranes, lying north of the Devonian plateau and under 850feet 

 altitude, received a heavy burden of detritus derived from the reexcava- 

 tion of the higher river valley. Such depressions in that plain as were 

 not filled ])y ice-drift were silted up during this lacustrine stage, and the 

 leveling was subsequently com])leted by the waves and currents of the 

 receding margin of the falling lake. Along the present river-coarse each 

 point was also at one time the locus of the river-delta deposits. In 

 consequence of this filling and leveling of the Warren lake floor in the 



* For description and discussion of these phenomena the reader is referred to the writings of 

 Warren Upliam, J. W. Spencer, G. K. Gilbert, Frank Leverett and F. B. Taylor in various geological 

 journals. A condensed review of the extinct lakes of the Saint Lawrence basin, with bibliography, 

 will be found in the American Journal of Science, vol. xlix, January, 1895, pp. 1-18. 



