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74 NEW YORK STATE MUSEUM 



disappears toward Leroy and the creek falls over the limestone in 

 a mere notch. Seventh, the Onondaga limestone has a practically 

 continuous outcrop from east of Batavia to the Genesee east of 

 Caledonia, and no heavy stream ever crossed its scarp in that region 

 in preglacial time. 



In attempting to locate the ancient valley for the interval from 

 Portage to Mount Morris we must apply the criteria as noted above 

 and use the principles and argument as in the Rochester district. 

 Assembling the topographic sheets it becomes apparent that only one 

 valley is found on the map which meets the conditions. The valley 

 of Nunda, now occupied by Keshequa 1 creek, and lying east of the 

 present river, has fair direction, sufficient size and the proper depth 

 where unfilled. The extensive moraine between Portage and Oak- 

 land is evidently the barrier between the Portageville and Nunda sec- 

 tions of the great valley. North and northeast of Portageville the 

 walls of the valley are only drift and no rock is found anywhere in 

 that district. On the steep slope south of Hunt (cut by the outflow 

 of the fifth stage of the glacial waters as described below), in the 

 creek gorge at Hunt's Hollow, and on the slope northeast, the rocks 

 appear, but they mark only the eastern wall of the ancient valley. 

 On the north no rock is found until the hill is reached north of 

 Oakland. The old valley is very wide here and was probably broad- 

 ened by the junction of four streams: (i) the Genesee, passing 

 northeast; (2) the Silver lake-Castile affluent, from the north- 

 west; (3) the St Helena tributary, from the north; and (4) the 

 Dalton or upper Keshequa waters, from the southeast. This re- 

 lation is indicated in the accompanying map. 



Downstream, or northeast of Nunda, toward Tuscarora and 

 Sonyea the higher and broader cross-section of the old valley is very 

 satisfactory. From Nunda to Union Corners the eastern wall is 

 plainly the slope of a great valley. The western wall is equally 

 conspicuous though partially dissected by a shallow north and south 

 valley northwest of Tuscarora. From Tuscarora to Sonyea the bot- 

 tom section of the old valley is obscured by drift and is not so 

 satisfactory. Rock appears at Sonyea station and half a mile east, 

 on the 600 feet contour, and in the 23^ miles of the creek canyon 

 south of Sonyea. Rock also appears north and south of Tuscarora, 

 but probably leaves a channel a mile wide. 2 



1 See footnote on page 53. 



2 Mr. Charles Haggardorn of Tuscarora, who has bored many wells in the Nunda district, 

 informs the writer that borings at Nunda were in the drift to deDth of 103, 97 and 73 

 feet. A mile east of Nunda Junction wells go to depths of 80 and 100 feet without 

 reaching rock; and in Tuscarora the drift is not less than 100 feet deep. 



