15 NEW YORK STATE MUSEUM 



topography and elevation as the Albany deposits elsewhere. The 

 source of the materials is believed to have been from the Alplaus 

 drainage basin to the northwest. It is true that this portion of the 

 lake was in communication with the main body of its waters through 

 the open Ballston channel near where the latter joins the Mohawk 

 channel. Woodworth has expressed the opinion that at the time the 

 Mohawk delta was making south of Schenectady, no deposits were 

 made in Lake Albany north of the Mohawk because that area was 

 then covered with ice. I have found nothing incompatible with this 

 view. As the ice retreated to the north, the Alplaus basin became 

 open earlier than the Ballston channel to the north and the part of 

 Lake Albany in question became silted up by inflows from the 

 Alplaus basin. 



RELATION OF THE LAKE ALBANY DEPOSITS TO THE TILL 



Till underlies the Lake Albany deposits generally, as they occur on 

 the area of the Schenectady sheet. Where streams have cut through 

 the sands and clays, boulders lie in their beds. In a few instances 

 the stream bottoms are in part boulder clays. For example, the 

 stream that flows into Saratoga lake from the Malta plain region 

 has its bed, in a part of its course, on a compact blue clay. The 

 same stream, where it emerges from the Albany deposits onto the flat 

 swampy area bordering the lake, shows blue clay in its banks and 

 boulders in its bed. 



The stream that, flows into Round lake from the west has like- 

 wise cut through the Lake Albany deposits and exhibits both boulder 

 clay and boulders in its bed. 



As already stated the streams that flow northerly from the sand 

 plain near Schenectady have their beds on the Albany clays, not hav- 

 ing cut through this deposit. Poentic kill farther to the west has 

 a boulder-strewn bed and on its bank, in a railroad cutting near the 

 new station of South Schenectady (just off the edge of the sheet), 

 till is exposed underlying the lacustrine deposits. In a 

 boring made by the Deep Water Survey^ on the sand plain, 

 near South Schenectady, cobblestones were found as the surface 

 of the underlying rock was approached. 



Similar observations with regard to the stratigraphic relation of 

 the Lake Albany deposits to the till were made in the other localities, 

 where the deposits are distributed, as described above. 



Elevation. The elevation of these lacustrine deposits varies some- 



1 Deep Waterways Report, p-540, House Doc. v.71, 1900. 



