210 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



takes a northeastward course from eastern Niagara County across north- 

 western Orleans County, thus greatly increasing the distance to the lake. 

 Eighteenmile Creek flows for several miles in a southwestward course 

 before turning northward into the lake, its course being governed to some 

 extent by the Iroquois beach. 



TONA^/VANDA CREEK. 



Tonawanda Creek consists of two quite distinct poi'tions: First, a 

 north-flowing portion, leading from Wethersfield Township, Wyoming 

 County, northward in a deep valley through elevated uplands to Batavia, 

 near which it enters the lowlands that lie south of Lake Ontario ; second, 

 a west-flowing portion, leading from Batavia to the Niagara River at Tona- 

 wanda. Between Batavia and Indian Falls the stream flows on the plain 

 back of the Corniferous escarpment. It descends in a cascade at Indian 

 Falls to the plain lying between the Corniferous and Niagara escarpments, 

 and flows in that plain to its mouth. This lower portion of Tonawanda 

 Creek, the headwater portion of Oak Orchard Creek, and the entire basin 

 of Black Creet are thus controlled by the geologic structure. They follow 

 the lowest parts of the plains between the two escarpments and traverse a 

 region coated to considerable depth with drift. Whether the lower course 

 of the Tonawanda follows that of a preglacial line is not fully determined, 

 though it seems probable that a preglacial line had approximately the 

 same position as the present stream. The course from near Batavia to 

 Indian Falls is independent of preglacial lines and is determined apparently 

 by the accidents of drift filling. The north-flowing portion above Batavia 

 appears to correspond closely with that of a preglacial Hue, but the latter, 

 instead of turning westward near Batavia, is thought to have continued in 

 a course east of north into the Lake Ontario Basin, traversing a district 

 now drained in large part by Black Creek. 



The headwater portion of Tonawanda Creek was occupied by a gla- 

 cial lake, which, as found by Fairchild, discharged at first westward to 

 Buffalo Creek, a tributary of Lake Erie, from a point about 2 miles south 

 of Johnsonburg, and at an estimated altitude of 1,410 feet.^ A study of 

 stream deltas leads Fairchild to think that there are two water levels lower 

 than the one that discharged through the outlet, one being at about 1,300 



1 Bull. Geol. Soc. America, Vol. X, 1899, p. 33. 



