1 8 NEW YORK STATE MUSEUM 



At other places on the Saratoga plain a thickness of not less 

 than 40 feet of sand is shown. For example, the valley plain of 

 Coesa creek, where the more northerly of the two roads running 

 west from Saratoga Springs crosses the stream, is sunk about 40 

 feet below the level of the general plain and there are no boulders 

 in the bed of the creek, the stream not yet having cut through the 

 sand to the underlying till. Also the depth of the valley of the 

 outlet stream of Loughberry lake, northeast of Saratoga Springs, 

 shows a thickness of the sands of more than 40 feet. 



The Saratoga plain represents an accumulation of sediments 

 which were deposited in this portion of Lake Albany by currents 

 moving in the general body of the lake. It does not stand in re- 

 lation to the mouth of a large stream which discharged into the 

 lake as in the case of the Milton plain (described below) and the 

 Schenectady plain at the mouth of the Mohawk. In other words, 

 the plain was not built up as a marginal delta but by sedimentation 

 from the currents of the lake itself. In regard to their source and 

 the conditions of their deposition in the lake, the following con- 

 siderations may be pertinent : As Lake Albany formed, the gather- 

 ing waters spread over the materials left from the melting ice sheet. 

 These materials were in part the debris of the ground moraine and 

 in part the somewhat assorted deposits of the streams issuing from 

 the ice sheet at its front or from its surface. As these deposits 

 became covered by the waters of the lake they were subject to the 

 work of waves and currents. Shore waves leveled and spread 

 out the materials as the growing lake advanced its margin. The 

 inflow of waters from the flooded streams discharging into the 

 lake caused strong lake currents in the direction of the outlet of 

 the lake. Where these currents became established they degraded, 

 in places, the deposits forming the bed of the lake and transported 

 the finer materials to more quiet waters, filling bottom depressions 

 and lateral expansions of the lake. These currents were subject 

 to shif tings of position and fluctuations of volume and velocity 

 according to varying seasonal, climatic and other physical factors. 

 Thus the deposits derived from the ice sheet were generally redis- 

 tributed and through the sorting power of water laid down in 

 stratified arrangement. 



The sediments derived from the drainage of the land surfaces 

 surrounding the lake were, in part, also distributed by lake cur- 

 rents ; but the building of deltas at the mouths of the larger streams 

 was a notable fact in the history of Lake Albany. One of these 

 delta formations is now to be described. 





