ABSTRACTS OF PAPERS 



55 



PREGLACIAL SLOPE AND CREST OF THE NIAGARA ESCARPMENT 

 BY J. W. SPENCER 



In the construction of the Welland Ship Canal at Tliorold, Ontario, beneath 

 20 to 50 feet of sandy clay (laminated), the ancient rock surface has been 

 exposed on the slope and face of the Niagara escarpment. Almost everywhere 

 the clay rests directly on heavy bedded Niagara limestone — smoothed, polished 

 and grooved — but in one depression was preserved a small mass of stony till, 

 a scanty evidence of an earlier glacial deposit. 



Figure 2. — Rock Face of Niagara Escarpment 



The rock was exposed in constructing the ship canal at Thorold, Ontario. The glacier 

 moved at right angles to the rock face. 



There had been no further erosion of either the harder or softer strata than 

 the truncation, smoothing, and grooving of their edges, as the glaciers of all 

 the epochs were pushing up the slope of the escarpment (which now rises to 

 330 feet above Lake Ontario), in direction some 10 degrees west of south, the 

 general course of the -escarpment being nearly east and west. The two later 

 and fainter sets of striations trend southwestward. Here was seen the most 

 perfect example of weak effects of glacial erosion in the lake region. 



In my original contribution on the origin of the lake ba.sins being due to 

 preglacial valleys, published under the inspiration of Prof. J. P. Lesley, the 

 obliquity of the glaciation was one, of the lines of evidence which I then set 

 forth, but here we have also the more direct proof of the absence of any real 

 work perfoi'med. The photographs were taken just before the crest was blasted 

 away, in October, 1919. 



