130 



GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



thence down Cattaraugus Creek to the lake. In favor of the route across 

 the divide between Conewango and Cattaraugus creeks there is not only 

 the greater width of the valley, but also its more direct course to the lake 

 basin and the presence of a channel deeper than is known to be present in 

 the Cassadaga Valley. Three wells along it penetrate drift to depths of 

 284, 814, and 330 feet, respectively, without reaching rock, while a fourth, 

 in Cattaraugus Valley, at the Indian Asylum near Versailles, penetrated 

 about 200 feet of drift. 



The northward slope of the rock floor and its wide departure from the 

 bed of the present sti'eams is in part shown diagramatically in fig. 4. On a 

 subsequent page it is shown that on this line, as well as on other ancient 

 drainage lines of this region, the northward slope of the rock floor may be 

 somewhat modified by surface warping. There may also have been consider- 



Randolph 



Dayti 

 /lis- 



Steamburg 



Conetvango River 



rocliJ-'S"-' 



flooj. . 



Level of Lake Erie (S73 A.T.) 



Fig. 4. — Diagram to show the relation between the present stream bed and the old rock floor along the preglacial Upper 

 Allegheny River. The numerals above the stream bed indicate surface altitudes, while those below show the depth 

 to which wells have penetrated. The sign (?) indicates that rock was not reached. 



able rock excavation by an interglacial stream along this line in the vicinity 

 of the lake basin, it being not improbable that an interglacial stream would 

 have had its source somewhat south of the present divide, which is a 

 moraine of Wisconsin or late glacial age. Both factors need to be elimi- 

 nated in determining the rate of slope of the rock floor of preglacial times. 

 The present rate seems too great for the nature of the valley. It may also 

 be necessary to make allowance for excavation by ice or by currents of 

 water underneath the ice in the portion of the valley within the glacial 

 boundary, but such an excavation could not have occurred in the portion 

 of the valley with northward-sloping floor which lies outside the glacial 

 boundary, i. e., between Kinzua and Cold Spring Creek. 



The general configuration of the drainage features of the region sup- 

 port this view of reversal or change in drainage, as may be seen by refer- 



