GLACIAL AND POST-GLACIAL HISTORY 



423 



body in the Hudson and Champlain Valleys as the ice was retreat- 

 ing after making the Brooklyn-Perth Amboy moraine. 



Below the level of the high-level gravel plateaus there are two 

 classes of deposits: (i) secondary deltas; (2) river terraces. The 

 former have been recognized with certainty only in the northern 

 Hudson. The latter occur in the northern Hudson Valley and in 

 tributary valleys both in the northern and southern parts of the 

 Hudson. In these lower terraces pebbles of clay occur rarely, evi- 

 dently derived from the erosion of the higher clay deposits. 



Fig. 5. — Diagrammatic sections: 



[A, of Haverstraw gravel plateau from west to east; B, of Newburg delta and moraine at the left and 

 Dutchess Junction gravel plateau with morainic east edge on the right; C, a section similar to and about one 

 mile south of D; D, Roseton on the left and the northern part of the Low Point deposits on the right. Par- 

 allel horizontal lines represent clay. 



In the Hudson Valley this old sea- or lake-floor plain is naturally 

 divided into three portions roughly corresponding with (i) the por- 

 tion south of the Highlands, (2) the Highlands, and (3) the Hudson 

 Valley north of the Highlands. Deposits in a lowland west of the 

 Palisade Ridge will be described in connection with Division i. 



HUDSON VALLEY SOUTH OF THE HIGHLANDS AND LOWLAND 

 WEST OF PALISADE RIDGE. 



From the narrows at Brooklyn northward to the Highlands the 

 land rises gradually, as a slightly rolling upland, best represented by 

 the even crest of the northern part of the Palisade Ridge, and by the 



