l88 ROCHESTER ACADEMY OF SCIENCE. [Oct. I4, 



THE LACUSTRINE HISTORY OF THE GENESEE VALLEY. 



By Herman LeRoy Fairchild. 



(Abstract. )=^ 



The Genesee Valley has a slope from its head in Pennsylvania to 

 Lake Ontario of about 2000 feet. During the Glacial period the 

 receding ice front formed a barrier which obstructed northward the 

 drainage we find at present. The waters, not only from precipitation but 

 derived from the melting ice body, were consequently impounded in 

 the valley south of the glacier and forced into some southward outlet. 

 In the lake history ten stages were described. During the four 

 earliest stages the outflow was to the Allegany river — Mississippi 

 system ; the latest and largest of the outlet channels being at 

 Cuba, N. Y. , traversed by lines of railway. The fifth and sixth stages 

 correlated with the great channel past Arkport and Hornellsville and 

 contributed waters to the Susquehanna system. The seventh stage 

 had outlet westward across the divide in the neighborhood of 

 Bethany, N. Y. , to the great glacial Lake Warren which poured its 

 waters past the site of Chicago to the Mississippi. The eighth stage 

 was the level of Warren waters which invaded the region and occupied 

 the valley up as far as Mt. Morris and Dansville. The ninth stage 

 was Lake Iroquois, with its shore line at the " Ridge Road" and its 

 outlet to the Mohawk — Hudson. This ninth (Iroquois) stage was 

 the last of the glacial waters in the valley, as the tenth or Ontario 

 stage is non-glacial, f 



The several water levels have left conspicuous evidences in their 

 eroded outlet channels, deltas of inflowing streams, etc. 



All the rock cuttings or ravines in the valley are post glacial, 

 showing diversion of the streams from their preglacial channels which 

 had been filled with drift. The largest examples are the canyons of 

 the Genesee at Portage, Mt. Morris and Rochester. The history of 

 the glacial waters, with the stream activity, is a complex but fascin- 

 ating and romantic story. 



•The substance of this paper, with map and illustrations, is published in the Bulletin of the 

 Geological Society of America, Vol. 7, pages 423-452, April, i8q6. 



tSince the above was written the author has discovered phenomena of another water plane 

 below the Warren and above the Iroquois. This was first described as the Geneva Beach in Bull. 

 Geol. Soc. Am. Vol. 8, pp. 281-284. f" * later paper, in Bull. Geol. Soc. Am. Vol. 10, p. 56, the 

 water body was called Lake Dana and was correlated with the outlet channel leading southeast 

 from Marcellus village. It was a long pause in the lowering of the hypo- Warren waters by east- 

 ward escape to the Mohawk. In the lake succession in the Genesee valley Lake Dana is the ninth 

 stage, making Iroqaois the tenth stage. 



