708 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



In addition to the fui-rowing just mentioned, Gilbert has discovered an 

 interesting dislocation of the Medina shale at Thirtymile Point, which he 

 attributes to glacial thrust.-^ 



GLACIAL STRI^. 



Numerous observations of glacial striae have been made by the writer 

 and by others on the Corniferous escarpment from Batavia westward, and 

 on the Niagara escarpment from Rochester westward to the Niagara River, 

 all of which have a beai'ing west of south. They vary, however, from S. 

 5° W. to S. 60° W. A similar variation in trend is found in the drumlins 

 which appear between these escarpments and which are thought to indicate 

 the direction of ice movement. 



On the uplands south of the Corniferous escarpment two observations 

 of strise were made in western Wyoming County which bear east of south, 

 one being S. 20° E., and the other S. 30° to 35° E. They are near the point 

 of coimection of the Growanda moraine with the interlobate belt, the one 

 with bearing S. 20° E., being 1^ miles west of North Sheldon, while the 

 one with bearing S. 30° E., is 2 miles southwest of Sheldon Center. The 

 diversity in the bearing of the strise in the low country lying between Lakes 

 Ontario and Erie and of those on the uplands to the south, may simply 

 indicate a difference in the direction of movement of ice in the axial and the 

 peripheral portions. A southwestward axial movement is to be inferred 

 from the fact that in the late stage of glaciation the ice sheet moved from 

 the Ijake Ontario into the Lake Erie basin; but the margin need not 

 partake of this movement, for in crowding against the uplands on the south 

 of these basins it would be liable to move in a southeastward direction. 

 There is a possibility, however, that the strise on the uplands of Wyoming 

 County were formed at a much earlier date than those on lower land to the 

 north and northwest, and that at the time they were formed the ice sheet 

 had a general southeastward movement across the lake basins, its thickness 

 being so great that the basins then had little influence upon its course. 



Irving P. Bishop, of the New York survey, has brought to notice 

 several instances of striation on the bed and bluffs of Niagara River near 

 Buffalo, which show that the channel had nearly its present depth prior to 

 the. close of the Glacial epoch.^ A photograph of a striated ledge at the 



'Loc. cit., pp. 131-134. 



2 Fifteenth Ann. Kept. New York Geol. Survey, 1895, pp. 326, 326, 392, 



