WORK OF GLACIAL WATERS 153 



of the larger valleys declining toward Lake Erie exhibit broad terraces 

 at various levels. A fine display may be seen from the Pennsylvania 

 Railroad from East Aurora up to Machias. Evidently such lake plains 

 can occur only north of the divide. Some plains similar in appearance 

 in the valley south of the divide fall into the categories of outwash plains 

 or of river floodplains. 



Scores of examples of detrital plains built in glacial waters by the 

 land drainage might be cited. In the Erie Basin the great plain in the 

 Cattaraugus Valley below Gowanda and that built by Silver and Walnut 

 creeks between Forestville and Silver Creek villages may be mentioned. 

 A very fine illustration is found on the Rochester sheet. The area be- 

 tween the Genesee River and Irondequoit Bay and between Lake Ontario 

 and the Iroquois beach ("Ridge Road") is the submerged delta plain of 

 the Genesee River in Lake Iroquois, now much dissected by present-day 

 streams. The flat stretches about Irondequoit Bay bounded by the 400- 

 foot contour are remnants of the silt plain, which in Iroquois time filled 

 the whole breadth of the valley. 



Sand plains built by the ice-border glacial drainage are also numerous. 

 These include, for example, the plains on the west side of the Genesee 

 Valley opposite Avon, the eroded area north and northwest of Geneva, 

 the mesa-like plains in the Onondaga Valley at South Onondaga and 

 northwest by Cedarvale, and the plain on which stands the business part 

 of Syracuse. 



The very extensive and conspicuous sand plains and terraces on both 

 sides of the Champlain and Hudson valleys, including the great delta 

 plain between Schenectady and Albany contributed by the Iromohawk 

 River, were built in sealevel waters that occupied this depression during 

 the time of the ice removal. 



Clay plains. — Where the static waters were wide and deep, so as to 

 permit full assorting of the detritus, more or less clay was spread over the 

 bottom in the more quiet water. The best example is found in the Iro- 

 quois Lake Basin. Tn the St. Lawrence Valley east of Cape Vincent, 

 Alexandria Bay, and Ogdensburg are extensive stretches of finely lami- 

 nated and deep clays, the glacial origin of which is indicated by the 

 abundance of lime concretions. The heavy clay deposits of the Hudson 

 Valley belong in ibis class, but were deposited in sealevel waters. 



Morainal lalcex. — This class includes the hundreds of lakes and lake- 

 lets (so-called ponds) now in existence that are scattered over the State 

 and most numerous in the Adirondacks. They owe their existence to the 

 blockade of valleys or drainage courses by glacial drift. The term 

 drift-harrier lakes would he Hie more accurate name. Great numbers o( 



