122 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



Between Toronto and Moundsville there are occasional remnants of 

 gravel deposits, containing glacial pebbles, on slopes and narrow rock 

 shelves below the level of the g-radatiou plains and above the Wisconsin 

 gravel terrace, bnt the amount is small compared with that between Beaver 

 and Toronto. There are also small amounts of glacial gravel at higher 

 levels than the Wisconsin terrace south of the old divide, from Mounds- 

 ville down nearly to Marietta. In that part of the valley they are found on 

 the old gradation plain as well as on the slopes below it, but, as above 

 noted, the altitude of the gradation plain south from the old divide is much 

 lower than that of the best defined gradation plain of the north-flowing 

 system. 



The distribution of these deposits suggests that the valley at and above 

 the old divide had been opened down about to the level of the gradation 

 plain south of the di^dde prior to the culmination of the earliest glaciation, 

 with its attendant deposition of the valley gravel. 



This subject, however, should not be dismissed until attention has been 

 called to certain features which seem difficult to harmonize with the view 

 that considerable trenching across the old divide had occurred at the time 

 of the first glaciation. On high rock shelves lying within the limits of 

 the old north-flowing system south of Toronto there are scattering 

 pebbles and thin deposits of loamy clay and fine sand. These deposits 

 suggest a ponding of waters in the early stages of reversal, and there are 

 suggestions of the presence of glacial material in the ponded waters. A 

 deposit especially open to suspicion is a fine sand suitable for molders' use, 

 which has been obtained on the rock shelves near Wheeling and Bellaire at 

 about 1,000 feet above tide, but its glacial derivation has not as yet been 

 demonstrated. In this connection attention is directed to a feature that 

 seems somewhat inharmonious with this view. The pebbles found on these 

 rock shelves are usually of resistant sandstone, probably of local deriva- 

 tion, and are deeply weathered; but on a rock shelf in the north part of 

 Wheeling, standing 990 feet above tide, fresh-looking erratics were found. 

 They are mainly small pebbles, an inch or less in diameter, of granite, green- 

 stone, and quartzite. They are especially abundant in an open field south 

 of the waterworks reservoir. Their fresh appearance, when in such an 

 exposed situation, makes it seem doubtful if they were deposited by glacial 

 waters at that high level. Possibly they have been brought up from a 



