GLACIAL GEOLOGY OF THE SCHENECTADY QUADRANGLE IQ 



what in the different localities. The Mohawk river has cut into the 

 materials of the sand plain at Schenectady forming the crescentic 

 line of bluff bordering the Mohawk flats. This bluff consists of 

 evenly stratified clays below grading into stratified sands above. 

 These have been partially disarranged by weathering at the summit 

 but a little south of the top of the bluff horizontally stratified sands 

 and fine gravels were observed in cuttings made in grading a street. 

 According to the contour lines the elevation at this place is not less 

 than 350 feet. The general elevation of the plain farther to the 

 south is slightly lower but it has clearly suffered from wind denu- 

 dation. 



In the southeast portion of the sheet east and south of Watervliet 

 Center the surface of the clay deposits is at a lower elevation than 

 that of the plain south of Schenectady. Crossing the river to the 

 north the deposits, largely of sand at the surface, rise to a gradually 

 higher altitude. North of Round lake on the flat sand tract east of 

 Malta the 38o-foot contour lines are shown. In the Ballston Spa 

 area, at the northern edge of the sheet, horizontally stratified sands 

 at 380 feet elevation were seen in an excavation made in the con- 

 struction of macadamized road. 



Regarding the elevation of the Mohawk delta deposited in Lake 

 Albany, Woodworth says i 1 " The average elevation of the surface 

 from Albany southward at the brink of the gorge (Hudson) is 

 now 200 feet. The surfaces rise northwestward to an elevation of 

 about 350 feet near Schenectady." The data above reported show 

 that there is a continuation of this rise as far north as the northern 

 edge of the Schenectady sheet. 



COMPOSITION AND ARRANGEMENT OF THE DEPOSITS 



i Near Schenectady. As already stated the Lake Albany deposits 

 near Schenectady consist of clays grading into sands. As a general 

 condition the clays predominate up to the level of 300 feet. The 

 grading of streets has afforded opportunity to observe these clays, 

 in their upper levels, through about 100 feet of exposure. They 

 are of dark color, very fine grained, highly plastic when wet and cut 

 with smooth shining surface. When exposed they become slightly 

 indurated so that their edges at a distance appear like shale rock 

 with even horizontal stratification. If the dried layers are cut with a 

 knife fine laminations are shown. They weather from a dark to a 

 gray color. 



1 Ancient Water Levels, N. Y. State Mus. Bui. 84, 1905, p. 130. 



