ANCIENT WATER LEVELS OF CHAMPLAIN-HUDSON VALLEYS 107 



glacial rock terrace of the Hudson river. No detailed study of 

 it has yet been made in this survey. 



Terrace at Jones Point. On the southern side of Dunderberg 

 mountain at Jones Point or Caldwell there occurs a well defined 

 terrace of sand and gravel of glacial origin, the original outlines 

 of which have now been nearly destroyed in the course of excava- 

 tion of sand and gravel for masons' supplies. This terrace 

 extends along the mountain wall for about half a mile, being 

 widest on the south where the mountain recedes from the river. 

 On the north near Jones Point, the terrace springs out from 

 the mountain side at an elevation of about 100 feet as a rather 

 coarse cobbly gravel deposit and declines southward to about GO 

 feet of altitude. On the south it is separated from the mountain 

 rock wall by a narrow gully which must either have been kept 

 open during the period of deposition or have been excavated 

 since by running water. 



The slopes of the deposit are now altogether destroyed except 

 for a small length of frontage near the northern end, but this 

 portion of the bank is not very well defined — it may or may not 

 have been filled in against a mass of ice lying in the river in 

 the manner of terraces contemporaneous with glacial tongues 

 filling a fiord or gorge. Its structure is more definitely shown. 



The southern broad part of the deposit gave the following 

 partial section in one pit from the top down : 



Feet 



Fine loam with gravel 4 



Gravel, egg sized 2 



Sand 15 



Gravel, very coarse 30+ 



Sand . exposed 4 



The face of a large opening at the southern end of the terrace 

 in July 1900 showed the following instructive section [fig. 10], 

 from which the mode of development of the terrace may be com- 

 pared to that of the glacial deltas described on page 80. 



The structure of the Jones Point terrace sio far as revealed isi 

 that of a gravel bar building southward by the carriage of 

 gravels over the surface of an embankment which must have 

 begun to form where the terrace is tied on to the mountain side 



