PREGLACIAL CONDITIONS AND LIFE 199 



channel cut thru the Niagara peninsula about fifteen miles west of the present 

 Niagara River. This main channel has several buried tributary channels, one 

 of which is in the form of a crescent and connects with the Whirlpool canyon 

 of the present Niagara gorge and with the drift-filled Whirlpool-St. David 

 Valley. Other buried river valleys occur at Port Stanley and Victoria in the 

 Erie basin and at Dundas and Hamilton in the west end of the Ontario basin. 

 Lakes Seneca and Cayuga 5 are believed to be ancient river valleys cut in the 

 bed rock and connected with the Laurentian River by buried channels. At 

 Cleveland a preglacial channel has been found in the Cuyahoga Valley, and the 

 ancient river has been christened the Newberry. 



Ortmann 6a believes that the north and south portions of the United States 

 were separated by a divide consisting of the Allegheny Mountains and the 

 Cumberland Plateau, which are thought to have joined the Ozarks and the high 

 western plains in front of the Rocky Mountains. North of this divide the 

 drainage was into the old St. Lawrence system and south of the divide the 

 drainage was into the Atlantic and the Gulf of Mexico. The Tennessee and 

 Cumberland rivers are thot to be the old headwaters of the Lower Mississippi 

 River in preglacial times. The ice sheet is believed to have dammed up the 

 rivers, forming lakes, and the Upper Mississippi system cut through the divide 

 between the Ozark Mountains and the Cumberland Plateau. The present 

 distribution of the fresh water mussels and the crawfishes suggest such a pre- 

 glacial and postglacial history, these groups of animals being strongly affected 

 in their distribution by the glacial changes. 



b. ANCIENT RIVERS WITH REVERSED OR ALTERED MODERN DRAINAGE 



Several modern rivers are made up in part of the reversed tributaries of 

 this ancient Laurentian River. 6 The upper Allegheny has been shown to be 

 the upper portion of an ancient river which flowed northward and entered the 

 Erie basin east of Dunkirk, New York( Carll River). The upper Ohio, includ- 

 ing the Monongahela and the lower Allegheny, also flowed northward thru the 

 Grand River and entered the Erie Valley. This old stream has been named 

 the Spencer River. 7 The Genesee River is a preglacial stream (one of the few 

 retaining the preglacial northward direction of flow) which has been forced 

 by the drift deposits to cut a new canyon -like channel at Portage and Rochester. 

 Irondequoit Bay is believed to be the outlet of the preglacial Genesee River. 8 



In Ohio, Indiana, and Illinois, ancient, now buried, river channels have been 

 discovered by means of well borings. In Ohio a wide area has been studied 



* Tarr, Bull. Geol. Soc. Amer., V, pp. 339-356. 



« Chamberlin and Leverett, Amer. Journ. Sci., (iii), XL VII, pp. 247-283, 1894. 



M Topog. Geol. Surv. Penn., 1910, 1912, Appendix E, p. 138, 1912. 



7 Forshay, Amer. Jour. Sci., (iii), XL, pp. 397-403, 1890. 



8 Fairchild, Proc. Roch. Acad. Sci., Ill, pp. 236-239, 1906; Chadwick, Proc. Roch. Acad . 

 Sci., V, pp. 123-160,1917. 



