162 J. L. Rich — Physiography and Glacial Geology 



Conesville lies between 1600 and 1620. At Manorkill, a little 

 farther east, what appears to be a delta lies just a little over 

 1600 feet. At Ashland, East Ashland, and Windham, the ele- 

 vations are between 1580 and 1600 feet. 



It has occurred to the writer that this progressive decrease in 

 elevation toward the east may be due to the lower deltas hav- 

 ing been developed at a somewhat later time than the higher 

 ones, when the lake level had been lowered slightly by the 

 downcutting* of the outlet channel through the Grand Gorge 



Fig. 13. 



~—rrr^ r- <^ x 







Fig. 13. Eastern end of delta at Windham. Foreground seems never to 

 have been filled by delta gravel. From a photograph. 



gap. Lack of synchronism in the building of the deltas might 

 well be due to the gradual eastward recession of the ice tongues 

 pushing out from the Hudson River lobe as that gradually 

 melted away. Such an explanation harmonizes well with evi- 

 dence of lowering of the lake level furnished by the wave-cut 

 front of the Flatter Kill delta. 



If differential tilting of the land has affected this water 

 plane, its effects cannot be determined without fuller investiga- 

 tions than it has been my privilege to make. Such an explana- 

 tion is opposed by the fact that the delta just north of Grand 

 Gorge Station and the Platter Kill delta lie at approximately 

 the same level in spite of the fact that they are so situated with 

 respect to each other that they ought to show the maximum 

 discordance. 



Apparent Absence of Deltas on the Upper Schoharie Creek 

 and its Tributaries. — All of the deltas thus far mentioned, 

 with the exception of that at Manorkill, have been visited. 

 The writer has not, however, had an opportunity to visit the 

 region to the south, except for one hurried trip down 



