88 GLACIAL FOEMATIONS OF ERIE AND OHIO BASINS. 



UPPER OHIO OR OLD MONONGAHELA SYSTEM. 



THE OLD DIVIDE. 



For some years it has been considered liighly probable that the Ohio 

 has been thrown across an old divide somewhere on the projecting portion 

 or "Panhandle" of West Virginia, but the precise position of the divide has 

 remained in question. It has also been held as probable that the portion 

 of the Ohio above this supposed divide, together with the Monongahela 

 and the lower part of the Allegheny, had their former discharge northward, 

 along a line leading through the Beaver and Grand river valleys of western 

 Pennsylvania and northeastern Ohio, to the basin of Lake Erie, forming 

 what has been aptly termed the old Monongahela system of drainage, the 

 Monongahela being the main affluent.' The apparent extent of this old 

 drainage system is indicated in fig. 1. 



The portion of the Ohio Valley in the 80 miles along the Panhandle 

 and for 50 miles farther down receives no large tributaries, the sources of 

 the streams, from both Ohio and West Virginia, being usually within 25 to 

 30 miles of the river. This feature of itself should arouse suspicion that 

 this tract has been the headwaters of old drainage systems. An examination 

 of the altitudes of its bluffs and of the bordering uplands confirms the 

 suspicion, for they are found tu be higher than the bluff's and the uplands 

 bordering the Monongahela to the east and the Muskingum to the west, and 



' The following reports and papers discuss or touch upon this siwect: 



Discovery of the preglacial outlet of the basin of Lake Erie into Lake Ontario, by J. W. Spencer: 

 Second Geol. Survey Pennsylvania, Kept. Q*, 1881, pp. 357-406, especially pp. 387 and 405-406. 

 Same paper appears in Proc. Am. Philos. See, Vol. XIX, 1882, pp. 300-337. 



Preglacial drainage and recent geologic history of western Pennsylvania, by P. Max Foshay: Am. 

 Jour. Sci., 3d series, Vol. XL, 1890, pp. 397-403. 



Pleistocene fluvial plains of western Pennsylvania, by Frank Leverett: Am. Jour. Set., 3d series. 

 Vol. XLIl, 1891, pp. 200-212. 



Further studies of the drainage features of the Upper Ohio Basin, by T. C. Chamberlin and Frank 

 Leverett: Am. Jour. Sci., 3d series, Vol. XLVII, 1894, pp. 247-283. 



Origin of the high terrace deposits of the Monongahela River, by I. C. White: Am. Geologist, 

 Vol. XVIII, 1896, pp. 368-379. 



Descriptions of terraces in that region may be found in the following reports and papers by 

 J. J. Stevenson: Second Geol. Survey Pennsylvania, Repts. K, 18/6, pp. 11-19, and K^ 1878, pp. 251- 

 263; Am. Jour. Sci., 3d series. Vol. XV, 1878, pp. 245-250; Proc. Am. Philos. Soc, Vol. XVIII, 1880, 

 pp. 283-316. Also in the following reports and papers Isy I. C. AVhite: Second Geol. Survey Penn- 

 sylvania, Rept. Q, 1878, pp. 9-17; and Rept. QS 1879, pp. 10-20; Am. Jour. -Sci., 3d series. Vol. 

 XXXIV, 1887, pp. 374-381; also discussions of drainage features incorporated in the detailed geology 

 of the several counties of western Pennsylvania covered by Repts. Q, Q^ Q', and Q* of the Second 

 Geol. Survey Pennsylvania. 



