26 



NEW YORK STATE MUSEUM 



beach ridges at the eastern margin of the bared rock areas 

 denominated spillways. 



In the low grounds there are other deposits — beds of gravel 

 sand, and clay sometimes in the form of - deltas, often occur- 

 ing as flats. Marine fossils occur well up toward 350 feet in 

 the area from Plattsburg northward and shells afford decisive 

 evidence of marine submergence up to 340 feet near Mooers. 



In general, the glacial deposits which have been worked over 

 by waves occur in three fairly well defined belts or zones, viz : 



1 A cobbly beach zone, several miles in width and ranging 

 from an elevation of over 700 feet on the north to 640 feet on 

 the south and thence down to about 250 feet. 



2 A sandy zone looping up into the area of the first zone but 

 lying mainly lower and somewhat farther east; and often char- 

 acterized by glacial erratics of small size not definitely arranged 

 by wave action. 



3 Nearer the shore of Lake Ohamplain a clay zone more or 

 less overlapped by the eastward extension of the sand zone. 

 This clay zone lies almost altogether to the east of the Mooers 

 quadrangle, but ramifications of it extend up the valleys of the 

 rivers as high as the 250 foot level as near Mooers. 



Shore lines of the area 



The area covered by this atlas sheet displays the greatest 

 array of abandoned and elevated beaches to be seen anywhere on 

 the New York side of the Champlain valley. In the vicinity of 

 West Chazy, unquestionable wave action can be traced up to an 

 elevation of 675 feet above the present sea level. Along the inter- 

 national boundary unquestionable wave action can be traced 

 within the limits of the map, from 280 feet up to about 540 feet. 

 Above this hight in the northwest corner of the area in the dis- 

 trict known as Armstrong's Bush, probable wave action appears 

 at 620 feet to 630 feet, and again at 720 feet above the present 

 sea level. 



The accompanying map [pi. 26] shows the beach ridges where 

 they have been seen. Except near the larger streams, where sandy 

 deltas are developed, the slopes between the 450 foot contour and 

 the 360 foot line are thickly beset with wave marks. The beach 



