PLEISTOCENE MARINE SUBMERGENCE I9 



Tapidly (or slowly, according to mental viewpoint) and the mechani- 

 cal conditions produced by the constant shifting of the zone of 

 wave attack were unfavorable for bar construction, especially in 

 tidal waters, the same as for erosional work. 



And there is another deterrent factor which has not been recog- 

 nized in this study, of perhaps even more effect than the change O'f 

 water level. Plates 3-5 show the location of beaches about the 

 Covey Hill salient. The summit marine shore is very strong on 

 the Champlain side of the highland, being represented in places by 

 remarkable vertical series of strong cobble bars and gravel banks 

 as far south as the parallel of Port Kent, the south edge of the 

 Dannemora quadrangle, plate 8. On the lower slope of Covey hill 

 at an elevation of 525 feet, 215 feet below the summit shore, is a 

 splendid series of heavy cobble bars, which was formerly thought 

 to represent the marine summit. The top of this inferior series of 

 bars lies at Covey Hill post office, and curves westward about the 

 hill at Stockwell, Maritana and Franklin Center, and enters New 

 York north of Chateaugay. When we follow this shore line south 

 from Covey hill we find a notable set o-f bars one mile south of the 

 international boundary, and a good display at Sciota and also west 

 of West Chazy. But as we pass farther south, on to the Danne- 

 mora quadrangle the shore features of the Franklin Center series 

 practically disappear. On the north edge of the sheet, 2 miles 

 northeast of West Plattsburg, this level of the lowering waters is 

 only a rolling plain of sand, like many other broad stretches in the 

 submerged Champlain region all devoid of beach phenomena. But 

 the waters stood here just as long as they did at Covey Hill post 

 office and Franklin Center, and the conditions of slope, exposure, 

 open sea, etc., were just as favorable for bar-building. What is 

 the explanation? Apparently the difference was due to the char- 

 acter of the material within the grasp of the waves. All the bars 

 in the district are coarse gravel or cobble, never sand. Along the 

 marine summit the glacial drainage built wide tracts of very coarse 

 material, which the waves quickly piled into bars. When the gravel 

 tracts were lifted above the waters and the waves found only sand 

 they were unable in the time permitted to bank it at any particular 

 level. 



All the strong beaches of the sea-level waters of the Hudson, 

 Champlain and St Lawrence valleys are coarse material, never 

 sand. Even the steadier level of Lake Iroquois produced only 

 cobble bars in the stretch of shorter lived waters between Water- 



