PLEISTOCENE MARINE SUBMERGENCE 47 



of Prospect hill (Willsboro sheet) good evidences of wave work 

 appear at 600 ieet. 



About Keeseville the Ausable river has laid down extensive 

 gravel plains at 500 feet altitude, with terraces declining to Lake 

 Champlain. The summit waters extended up the river 10 miles 

 from Keeseville, to Ausable Forks, and broad plains between there 

 and Clintonville, at 660 feet by the map, represent the higher delta. 



The Dannemora quadrangle carries some of the strongest, hand- 

 somest and most convincing shore features of the marine-level 

 waters of the State. As these are mapped in plate 8, detailed 

 description will be unnecessary. It will be seen on the map that the 

 bars have been plotted on the highways, but have not been traced 

 across country, which gives the beaches on the map a broken and 

 patchy appearance, untrue to fact. 



Along the meridian of Harkness, Clark School, Beckwith School, 

 and West Plattsburg the summit plane rises from about 660 at 

 Harkness to over 700 feet at the north edge of the map. The 

 deltas, glacial channels, and summit bars agree closely with this 

 plane. The only discrepancy noted is the excessive height of some 

 bars a mile southwest of Clark School which rise to 706 feet by 

 the map, or nearly 40 feet above the profile (plate 10). The 

 Harkness embayment was competent to hold broad glacial waters, 

 but these bars are so closely connected with the marine shore that 

 they are regarded in the same category as the high Port Henry bars. 



Three classes of features are depicted on the map: (i) the ice- 

 border drainage channels which terminate at or somewhat beneath 

 the static waters; (2) the cobble and gravel bars of wave con- 

 struction; (3) delta plains and terraces which occur at varied levels, 

 from somewhat above the static waters to low levels in the sub- 

 siding waters (plate 14). 



As is usually the case along all shore lines, the heaviest bars 

 are somewhat below the summit plane, where the waves had suf- 

 ficient accumulation of coarse material. The vertical series of 

 heavy bars are found on stony slopes, usually so rough and stony 

 as to be left uncultivated. Above and below the ground may be 

 tilled. All the strong, close-set bars, not only on the Dannemora 

 quadrangle but elsewhere, are on tracts of cobble or coarse gravel, 

 commonly the deltas of glacial streams. Over ground immersed 

 in sand the waves produce only smooth or rolling surfaces. On 

 the areas of rising land, with open sea and free wave action, the 

 construction of bars required coarse materials, at least for the 

 basis or framework. 



