74 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



of the Corniferous escarpment, sucli as characterizes the plain south of the 

 Niag-ara escarpment. On the contrary, a somewhat rapid rise is fomid in 

 passing from the Corniferous escarpment back to the base of the hills. 

 Much of the border stands 900 to 1,000 feet above tide, or 100 to 300 

 feet or more above the brow of the Corniferous escarpment. Notwithstand- 

 ing this rapid rise the surface of the lowland is markedly less hilly than 

 that of the region to the south. The central portion for a few miles on 

 either side of Batavia stands above the level of the glacial Lake Warren, 

 but the eastern and western portions were largely covered by the waters of 

 tliat lake. The portion not covered by Lake Warren is largely occupied by 

 a complex morainic system, which gives it a sharply undulatory expression. 

 It is probable that the ice sheet removed much material from this low- 

 land and obliterated the preglacial topography to a marked degree. The 

 amount of drift, however, is so great that it is difficult to ascertain the 

 topography of the underlying rock surface. The present rivers appear to 

 be largely independent of preglacial lines in their passage across the low- 

 land. 



GRAND RIVER BASIN. 



From near Buffalo, N. Y., westward to Cleveland, Ohio, there is a 

 narrow plain or strip of lowland on the south border of Lake Erie, extend- 

 ing back usually 5 to 10 miles from the lake shore. But in northeastern 

 Ohio an arm or extension of this plain, known as the Grand River Basin, 

 reaches back to the vicinity of Niles, a distance of about 40 miles from the 

 lake. It is only 8 to 12 miles in width, and stands 150 to 300 feet above 

 Lake Erie. If, however, the drift were removed, much of it would be level 

 with the lake. As indicated below, this basin appears to have been the old 

 line of discharge for a large part of the upper Ohio watershed. It is now 

 occupied throughout much of its length by the headwater portion of Grand 

 River, a small tributary of Lake Erie. Its southern end is crossed by the 

 Mahoning River, which belongs to the present drainage system of the Ohio. 

 This basin is excavated in the upper portion of the Ohio shales (the equiva- 

 lent of much of the Chemung formation) and in the Waverly, Berea, and 

 Cuyahoga shales and sandstones. The I'emainder of the plain bordering 

 Lake Erie between Buffalo and Cleveland is chiefly in the Portage and 

 Chemung formations, which are the equivalent of the lower portion of the 

 Ohio shales. The softness of these formations along the border of Lake 



