ANCIENT WATER LEVELS OF CIIAMPLAIN-HUDSON VALLEYS 207 



surrounding flat as a shallow water sea bottom deposit. The hill, 

 at least one slope of it. is frequently left strewn with boulders from 

 the washing out of the material which could be more readily 

 removed by the waves and currents. The annexed diagram show- 

 ing the cross-section of one of these shoals north of Mooers Junc- 

 tion illustrates a typical case. 



It is a noteworthy fact that in a few cases in this area, heavy 

 beaches of rolled pebbles occasion the western flanks of these 

 northsouth glacial hills, while on the eastern slope large boulders 

 lie out on a surface which exhibits otherwise no marine action 

 other than probable erosion. This peculiarity is brought out in 

 the diagrammatic section given below. 



Subdivision of the marine beds. The marine beds frequently 

 exhibit in limited sections a passage from clays below through 



W E. 



Fig. 24 Modified glacial hill with a beach. This hill has been successively a 

 shoal and an islet 



sands upward into gravels or even much coarser deposits. Par- 

 ticularly is this often the case in the sand zone. Xearer the 

 present lake shore or on the inner borders of the clay zone sections 

 reveal sands alone overlying clays. It is evident from the various 

 sections and from the history of the changing sea level that the 

 clays of the middle of the valley represent the deposits made there 

 through the episode of marine invasion ; that the lowest of these 

 marine clays correspond in age to the highest marine beaches; 

 that the highest of the clays correspond nearly to the lowest 

 beaches now above the lake and clay levels. Pebble beds, gravels 

 and sand, as well as clays must have been making during the 

 entire epoch ; it is therefore not feasible to establish time divisions 

 on these lithologic characters. There is no such time division in 

 the Champlain area as that of the Leda clay and the Saxicava 

 sand but these biologic terms may be applied to facies of the 

 deposits occurring in zones of more or less contemporaneous 

 development. 



