40 NEW YORK STATE MUSEUM 



The Canastota channel is occupied by the two railroads, and the 

 south bank of the ancient river is the conspicuous bluff close to the 

 railroad station [see title 28. p. ^3]. 



The channels on the West Stockbridge hill are fewer than on the 

 Cranson hill, but stronger. The map shows that they have a de- 

 cided curvature about the nose of the hill, indicating that lobes of 

 ice front occupied the Cowaselon and Oneida valleys while the 

 drainage followed the reentrant angle in the ice front on the ridge. 

 The two southernmost channels lie on the crest of the ridge and on 

 the south-facing slope of a limestone knob, a relationship which is 

 singular and not understood. 



One large delta has been mapped, west of the Oneida Community 

 and south of Oneida Castle. This extensive deposit is composed 

 largely of debris from the Salina shale in which the lower channels 

 are cut, and the weathering and storm-wash have so dissolved and 

 eroded the delta that in form it resembles a moraine. It is very 

 possible that some moraine drift is buried in the delta. 



The Cowaselon vallev is so narrow and steep-walled that the 

 living creek has removed the material which must have been swept 

 into it by the Cranson hill drainage. However, the map is prob- 

 ablv deficient in not indicating some delta deposits at Lenox and 

 Wampsville. 



DELTAS 



Principles in delta construction 



The many detrital deposits built in quiet waters by the contri- 

 butions of the ice border drainage have been noted and briefly 

 described in the preceding pages in connection with their correlat- 

 ing channels and water bodies. A few points in theoretical dis- 

 cussion, with application to the field under present study, will be 

 helpful to students of the phenomena. 



Theoretically, delta deposits should be expected to occur where- 

 ever a vigorous stream debouched for considerable length of time 

 into standing water; but they are often lacking, and the question 

 arises whether the absence of the delta is due to failure of forma- 

 tion or to subsequent removal. 



In the study of deltas a variety and combination of modifying con- 

 ditions must be considered, which may be grouped under three heads : 



A Conditions relating to the stream work. 



B Conditions pertaining to the delta area, or the physiography 

 of the receiving basin. 



