154 



NEW YORK STATE MUSEUM 



quently formed clays were laid down in this district. Any great 

 depth of water would have made it difficult for a current either 

 in the ice or outside of it to transport such coarse materials at 

 the* bottom. From Dresden southward to Chubb's Dock, the so 

 called Champlain clays rest on the uneven and often kamelike 

 surface of these older gravels and sands. 



Such amassme-nts of gravel have already been noted in the 

 Hudson valley occupying a like subjacent position to the Albany 

 clays, as at North Albany aud in numerous sections from 

 north of Cohoes to the point where the stream draining Round 

 lake falls into the Hudson. The deposits are evidently glacier 

 margin deposits associated with the final melting out of the ice. 

 If the structures of these gravel deposits at North Albany and 

 Dresden have been correctly interpreted, it would seem as if for 

 a time at least the land must have been higher than it was during 

 the lake stages in which clays were deposited and high enough in 

 relation to the southern Hudson valley to permit a rather free 

 run off of the glacio-natant waters. The isolated facts cited from 

 the talus at the southern base of Skene mountain at White- 

 hall and the similar phenomena east of Saratoga lake [see p. 136] 

 strengthen this conclusion — that changes of level were taking 

 place during the retreat of the ice sheet. This particular move- 

 ment appears locally to have affected lands lying above sea level. 

 Its recognition carries with it, in view also of the marine deposits 

 which followed, the assumption that following the disappearance 

 of the ice from this portion of the valley a reversed movement set 

 in by which the land was lowered on the north relatively to the 

 southern part of the State so as to produce an uplifted barrier 

 in that direction capable of retaining the waters which formed the 

 lakes whose records are so clearly shown in the succeeding depos- 

 its of clays and marginal sand deltas. It must be borne in mind, 

 however, that these earlier movements preceding the clearer 

 records of the glacial lakes and the marine invasion depend on 

 scattered and fragmentary evidence which further study of the 

 district may prove in a better light to be capable of a different 

 interpretation. 



Street Road terrace [Ticonderoga quadrangle, pi. 15]. North 

 of Street Road and at the eastern base of Buck mountain there 



