PLEISTOCENE GEOLOGY OF MOOERS QUADRANGLE 



43 



and also for the reason that the ground south of " the Gulf " 

 along the line of the Stafford's and Blackman's rock spillways was 

 much higher than the path opened up as the ice retreated from the 

 Potsdam escarpment to the east of " the Gulf." 



That certain shore lines on the Mooers quadrangle and the area 

 west of it are contemporaneous with the drainage through " the 

 Gulf" notch and thus with the ice sheet frontage against the 

 northern slope of Covey bill, is shown by the absence of such 

 distinct wave marks on the northern slope of the hill between 

 the levels of at least 900 feet and GOO feet. An almost unmodi- 

 fied slope of till in the most favorable position for rearrangement 

 under the action of waves or lateral glacial streams covers this 

 important interval. The phenomena of " the Guff " demand an 

 ice barrier on the north to hold up the extraglacial waters so 

 as to cause them to flow over a col in the divide between the 

 head waters of the Chateaugay river. The water levels on the 

 south of " the Gulf," whose range is the same as that of the 

 depth of kk the Gulf," are, it has been shown, also contemporaneous 

 with the ice frontage in that field and therefore, I think, are 

 demonstrated to be independent of the sea in the Champlain and 

 St Lawrence valleys. 



The intervals between signs of water level on the Mooers 

 quadrangle thus appear to be associated with a glacial lake, sud- 

 den falls in which might arise from the opening of new spillways 

 as a consequence of the continued retreat of the ice sheet. 



There is, according to my observations, something like a periodic 

 recurrence in the vertical interval between these water levels; 

 thus there is, above the continuous series of lower beaches which 

 stop off between 520 feet and 540 feet, an interval up to 610 to 

 G20, another interval from that level to that of 720 to 725, followed 

 t>y another up to 810 or 820 feet, intervals approximately 100 feet. 

 This is I believe to be attributed to the nature of the ground about 

 the southern end of this glacial lake in the region of its outlet. 



Determination of the upper marine limit, benches and beaches on 

 the north slope of Covey hill. The accompanying sketch map gives 

 a general idea of the Covey hill district [see pi. 11]. The roads 

 and position of villages have been traced from Walling's Atlas of 

 Canada. The contour lines are mere approximations based on 



