PLEISTOCENE GEOLOGY OP MOOERS QUADRANGLE 9 



gorges, they have shallow beds in the drift coating with here and 

 there bottoms of bed rock, evidently along courses which have been 

 taken since the disappearance of the ice from the uplands and the 

 withdrawal of the bodies of water which submerged the lowlands 

 on the north and east. The earlier channels of these streams, if 

 such exist, have not been discovered. 



Glacial deposits 



The entire area of this quadrangle appears to have been covered 



with deposits by the ice sheet ; but in more than half of the area 



the drift has either been removed or worked over by waves and 



currents to such an extent that at least the upper visible portion 



of the surface material in the low grounds can hardly be called 



glacial drift. The unmodified glacial deposits occupy the higher 



grounds everywhere above the 900 foot level in Altona and the 



northeastern part of Dannemora and the northwestern part of 



Beekmantown. 



Till of the uplands 



In the elevated grounds above the zone of wave action the 

 glacial deposits are mainly unstratined and of the class denomi- 

 nated till or ice-laid drift. The material of this drift is largely 

 the Potsdam sandstone derived from the immediately underlying 

 and adjacent area of these rocks on the north. Angular slabs 

 of the sandstone are almost everywhere met with in the till area. 

 The finer debris between the slabs is also prevailingly of the 

 grayish white gravel or sand from the same rock. But fragments 

 of other rocks, more commonly of igneous origin occur, and evi- 

 dently have traveled from known outcrops of such rocks in 

 Canada. 



The till in the uplands varies much in thickness. A glance at 

 the accompanying map shows by the distribution of outcrops that 

 very slight excavations along certain roads have served to reveal 

 the rock. 



In the plateau of sandstone about Alder Bend, the till, so far 

 as can be determined for considerable areas, is probably over 20 

 feet in thickness, but except in certain restricted belts, where 

 it is heaped up, the till appears to be a relatively thin sheet. 



