38 NEW YORK STATE MUSEUM 



that strong currents swept away the western portion of the original 

 kames area, exposing and leveling the underlying till. 



4 The building of the Milton delta. Evidences that the Milton 

 plain is of delta origin have already been given (page 19). The 

 location of the plain with reference to the valley now occupied by 

 Kayaderosseras creek, shows clearly that the materials of the delta 

 were brought to Lake Albany by a stream occupying this valley. 

 The expanse of the delta and the thickness of its deposits (approxi- 

 mately 80 feet as measured by the difference in level between the 

 Milton plain and the Saratoga plain) indicate the volume and car- 

 rying power of the delta-forming currents. It is certain that a 

 stream of the magnitude of a large river, of high velocity of flow 

 and bearing a heavy load of sands, once coursed through the pres- 

 ent valley discharging into Lake Albany at West Milton. Its sedi- 

 ments were spread widely into the lake, building a fan-shaped delta 

 with, however, a prominent southward-extending lobe. The direc- 

 tion of growth of the latter, it may be inferred, was determined by 

 the general southward course of the currents moving in Lake 

 Albany. 



The Milton delta plain fixes the time of 'the epoch of flooded wa- 

 ters — as occurring in the drainage axis of the Saratoga quadrangle 

 — as subsequent to the withdrawal of the ice sheet and prior to 

 the time when Lake Albany began to subside. An idea of the length 

 of time represented by this epoch may be obtained from the dimen- 

 sions of the delta deposit. 



The elevation of the Milton delta plain, 400 feet above sea level, 

 is higher than that of the Mohawk delta plain at Schenectady. 

 Woodworth 1 places the latter at 350 feet, but from observations 

 made by the writer of exposures recently made in the grading of 

 streets, the stratified Lake Albany deposits occur at Schenectady 

 up to the level of 360 feet. This makes a difference in elevation 

 of 40 feet as between the two delta plains. As it is probable that 

 the deltas in both localties were originally built up to the surface of 

 the waters of Lake Albany, the present difference can be accounted 

 for only by postglacial deformation, or regional warping of the 

 earth's surface. The Milton plain, measured at its portion imme- 

 diately north of Ballston Spa, is about 16 miles northward from 

 Schenectady. This gives a deformation of 2^ feet a mile of north- 

 ward upwarping which agrees well with the estimate made by 





l O/>. cit., p. 130. 



