PLEISTOCENE GEOLOGY OF MOOERS QUADRANGLE 31 



they are the traces of successive stages of water action along the 

 border of the ice. In a later part of this report the attempt is 

 made to correlate them with different levels of a glacial lake which 

 has left more definite traces over the southern border of the quad- 

 rangle, but whose tilting does not exceed 4.5 feet to the mile to the 

 south. In fact there ds no very definite upper limit to the signs 

 of water action in this field and certainly none that can be traced 

 continuously across the area. Far above this field to the west as 

 the ice withdrew from the district, streams of water coursed along 

 the ice border, building stream bars and plains of gravel and sand 

 wherever space was provided for temporary lakes; gradually as 

 the form of the ground favored the process larger lakes ending 

 in one large lake came into existence and this extended north- 

 ward over the Ohamplain valley as the ice front retreated. With 

 regard to the beaches and signs of wave action in the quadrangle, 

 the following account groups them roughly in two series. 



Upper series of beaches 



The upper series of beaches on the Mooers quadrangle comprise 

 those higher water level traces of the area of which no satisfactory 

 evidence has been found extending beyond the limits of the map 

 around the northern slope of Covey hill on the Canadian side of 

 the boundary line. These water levels are believed to be mainly 

 the margins of successive lower and lower stages of a glacial lake 

 which gradually extended northward in the Champlain valley 

 with the northward recession of the Wisconsin ice sheet. The 

 evidence on which the upper beaches are distinguished from a 

 lower group of marine origin is such as to make what is appar- 

 ently an arbitrary division of the beaches in this particular area. 



Along the northern edge of the quadrangle at the international 

 boundary, the upper series as here defined includes those traces of 

 water action which appear above 450 feet. It will be noted by an 

 inspection of the map [pi. 2G] on the rather steep slope between 

 the 380 and the 520 foot levels, averaging about 140 feet to the 

 mile, the beach ridges are well developed and closely crowded. 

 Above 538 feet no traces of beaches in the northern part of the 

 map are shown till the 620 foot level is reached, where scanty 

 evidences of possible beach action have been seen at one place in 



