PLEISTOCENE HISTORY OF THE GENESEE VALLEY 73 



that a few miles north of Avon the channel bent eastward along 

 the outcrop of the very soft Salina shale, similar to the present 

 streams on the latitude parallel between Buffalo and Syracuse. 

 This east and west stretch of the ancient valley, lying athwart the 

 direction of the ice movement, was the part most filled by the 

 glacial drift. 



Portage-Mount Morris district. The canyons at Portage and 

 Mount Morris together with the 8 miles of narrow intervening 

 valley represent a single diversion of the river. Evidently the ravine- 

 like valley from St Helena to Gibsonville is older than the canyons 

 at the two ends, being V-shaped and flaring, although the rocks 

 are as resistant as those of the Mount Morris canyon, locally 

 called the " High Banks." Yet this valley is decidedly too narrow 

 to have been a part of the Genesee valley, and is entirely out of 

 harmony with the open valley above Portage and below Mount 

 Morris. We must conclude that the St Helena valley belonged to 

 some smaller or tributary stream. 



The St Helena creek, as we may name the preglacial tributary, 

 probably flowed south and entered the Genesee river 2 miles east 

 of the Portage viaduct, near the Lewis corners [see map]. In a 

 similar relation the depression followed by the Erie Railroad north 

 to Silver Springs and including the valley of Silver lake probably 

 drained south and joined the Genesee valley north of Portage by 

 the break in the west wall at that point. This gap in the rock wall 

 is too small to represent the old valley of the river, as suggested 

 by Grabau, 1 but undoubtedly is the junction of a tributary valley. 

 His suggestion that the old valley led northwest and comprised the 

 Warsaw- Wyoming or Oatka creek valley can not be maintained. 

 First, the break in the rock wall at Portage is insufficient to repre- 

 sent the river valley. Second, the gross topography indicates no 

 sufficiently capacious valley leading toward Warsaw, and the ob- 

 scuring drift is scanty. Third, while the Oatka has a handsome 

 valley from Warsaw to Pavilion this has neither the size, form nor 

 altitude that would represent the lower stretch of the river valley on 

 that meridian, in soft shales. Fourth, rock appears at Castile in 

 the bed of Wolf creek, at about 1260 feet altitude; and at the rail- 

 road station rock underlies the surface at near 1400 feet, thus 

 effectually closing any river escape in that direction. Fifth, the head 

 of the Warsaw valley, at Rock Glen, is in rock on both sides of the 

 valley axis, at 1200 and 1300 feet. Sixth, the Oatka valley quite 





Bost. Soc. Nat. Hist. Proc. 1894. 26: 359-69- 



