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NEW YORK STATE MUSEUM 



The relation of the clays to the older gravels shows that the 

 gravels were cut off on the south by running water so as to form 

 a well defined hank. Down this bank cobbles and boulders rolled. 

 Subsequently clays began to deposit in horizontal layers against 

 the bank, indicating a change from powerful streams of water 

 running over the surface and cutting deeply into its drift deposits 

 to a time of quiet silt-laden waters. 



Further indications of the mode of building of these older 

 gravels occur in a pit in the same vicinity. The structure is that 

 of an aggraded deposit of gravels with extremely coarse lenses 



Fig. 16 Cross-section of aggraded glacial gravel deposit at North Albany, showing- 

 lenses of coarse gravel in old stream bed. [See also pi. 9] 



showing where the stream bed as it wandered from point to point 

 in the building up of the deposit happens to appear in the cut. 

 The above figure illustrates the general cross-section of the pit. 



Mohawk delta. The extensive sand and clay plains developed 

 on the Albany and Schenectady quadrangles in the towns of 

 Bethlehem, Guilderland, Watervliet, Niskayuna and Rotterdam, 

 south of the Mohawk river, form an ancient delta of that river 

 and are the most extensive deposits of this nature in the Hudson 

 if not also in the Champlain valleys. The deposit, clayey below 

 and near the Hudson gorge, gives way to sands toward the north- 

 west and in the upper sections. Along the Hudson gorge the 

 deposit fills in depressions in the rock bench and mantles this 

 older topography except at such localities as the Abbey at Glen- 

 mont. The average elevation of the surface from Albany south- 



