1U4 NEW YORK STATE MUSEUM 



1 to 2 inches in diameter overlie the clavs giving place above to 

 glacial sands. At the northern point, there is reason to believe 

 that the till' is banked up against tlie clays if it does not overtop 

 them. IM'obahle evidence of the action of the ice sheet is found 

 in the highly crnmi)led condition of many layers of clay; but 

 this crumpling and contortion may have taken place as the result 

 of the creeping of the clays when the overlying sands and gravels 

 became thickly dei)osited on them. It is a characteristic of the 

 outer clnys in deltas.^ 



At the northern margin of the North Ilaverstraw dissected delta 

 terrace and again at the northern extremity of Croton point 

 there are slopes composed of coarse deposits coming directly from 

 the ice sheet itself. These have been preserved as they were laid 

 down, without erosion on the one hand or a covering of newer 

 clays or silts on the other. They have suffered little from erosion 

 because streams have run elsewhere doing their work most effi- 

 ciently on the claye}^ deposits remote from the loose structured, 

 gravelly beds near the ice contact. That these slopes have not 

 been covered by newer deposits must be explained as in general 

 due to their not lying in a basin of deposition. Either streams 

 have not been directed toward them or if they have been sub- 

 merged such submergence was very short indeed and the waters 

 free from transported sediment. Indeed there has been no deposi- 

 tion above present sea level in this region since the ice retreated 

 from the successive stages. 



Cedar ])ond brook in cutting down through the North Haver- 

 straw deposit has left a subordinate terrace at about GO feet above 

 the sea. This is a narrow terrace traversed by the road which 

 leads southward from the village to the brook. The remnant of 

 the old delta on the south side of the stream rises to 60 feet or 

 over. The occurrence of a terrace at this hight made in the down 

 cutting of the stream is suggestive of a water level at about 60 

 feet. The dei)osit at Tarrytown was built up to 60 feet above sea 

 level. The full significance of these clues to a water level higher 

 than that of the sea at iirosent it is hoped to bi-iiijT out in the dis- 

 cussion closing this report. 



'RnRs<'ll, T. O. Lakes of North Amorica. 1895. p.50. Also in U. S. " 

 Geol. Sur. Monogr. XI. IS.sn. Kios, IT. N. Y. State Mus. Bui. 12. 1895. 

 p.lOS, 118-19. 



