ANCIENT WATER LEVELS OF CII A M PL A I N— II UDSON VALLEYS 125 



Hudson valley in the manner shown in the accompanying dia- 

 gram [fig. 15} « 



It will be noted from the account which follows that these two 

 terraces accord closely with the level of free deltas farther north. 

 If these terraces were made in open water, it must have been 

 during a temporary retreat of the ice tongue which lay in the 

 valley, a readvance of which produced those aspects of the de- 

 posits as they now exist which point to deposition of the 

 materials about their outer margins in the presence of ice. The 

 limit of construction by water action in the South Bethlehem 

 terrace was apparently a local affair. This appears evident 

 from tracing this ice mass around the base of the hills bordering 



S. BETHLEHEM. 1CE.-SHEET. SCHOOACK DEPOT 



iLsf-K V - " 4, E 



Fig. 15 Cross-section of glacial deposit in Hudson valley from Schodack Depot to South 

 Bethlehem, showing glacial terraces where the Moordener kill and Oniskethau creek 

 mouthed on the ice border. The rock terrace is covered by clays of later deposition. 



the west side of the Hudson valley past Feura Bush and New 

 Scotland to the upper valley of Vly creek southwest of Voorhees- 

 ville. In this region the escarpment of the west wall is in- 

 dented by the New Salem valley drained by the creek named. 

 When the ice retreated from the upland and its southern margin 

 lay at this point, a barrier was created across the northward 

 drainage of the Vly creek, holding up its waters in a temporary 

 lake probably to the hight of the divide between it and the 

 Oniskethau, about 430 feet above the present sea level. The 

 west branch of Vly creek (see the Albany quadrangle) flows in a 

 depression approximately along the line of the ice front at this 

 stage. From the south bank of the creek, rises a terrace of 

 glacial materials which attains an elevation of 400 feet, at a 

 point west of the junction with the south branch of the same 

 stream. This plain is a rude delta built into the lake at this 

 stage. The outflow of this lake took place apparently through 

 the Oniskethau and thence contributed somewhat to the terrace 

 building at South Bethlehem. These trivial details have been 

 presented as showing that deposits which are here indicative of 



