NEW YORK STATE MUSEUM 



Chapter J/ 



GLACIAL DEPOSITS OF THE UPPER HUDSON VALLEY 



From Albany northward the precise position of the ice front 

 at its several successive stands in the retreat is frequently a 

 matter of conjecture in the immediate vicinity of the Hudson 

 gorge owing to the extensive water action which has followed 

 the retreat of the ice from this district. In the following notes 

 the geographic order is generally adopted as the basis of descrip- 

 tion. At many of the localities the deposits recorded and the 

 topographic features noted pertain to widely separated events. 



Hoosic delta. The Hoosic, the largest tributary of the Hudson 

 river from the mountainous belt on the east, enters the Hudson 

 gorge a few miles north of the month of the Mohawk and nearly 

 opposite the Round lake channel at Mechanicville. The approxi- 

 mate apex of this delta is at Schaghticoke at an elevation of 

 360 feet. The Hoosic has sunk its bed deeply within the delta 

 and the clays which border the Hudson gorge, turning to the 

 northwest, a course which it has pursued since dissection began. 

 There is a probable ancient temporary channel on the southeast 

 border of the delta followed by a railroad between Melrose and 

 East Schaghticoke stations. The bottom of this trench is about 

 350 feet above sea level. This rather marked deflection of the 

 stream as it now runs to the north can not conclusively be stated 

 to be due to the same cause as that which has been advanced for 

 the position of the Mohawk on the northern side of its ancient 

 delta. The dissection of the Hoosic delta is considered on page 200. 



Above Schaghticoke with the falls in the stream there are two 

 notable features : on the southeast the flats of Tomahawk creek 

 extending nearly to Raymertown and on the northeast the 

 glacial terraces bordering the Hoosic river to and beyond the 

 limits of the Cohoes quadrangle. These terraces with an eleva- 

 tion of about 400 feet at Valley Falls, 4 miles farther east rise 

 to 420 feet. They are sharply trenched by the Hoosic with lateral 

 gullies. They are evidently flood plain deposits or parts of a valley 

 train whose surface from Schaghticoke eastward lies above the 

 level of the water body into which the river at one time dis- 

 charged. Their levels have therefore been neglected in the con- 

 sideration of the problem of water levels in the Hudson valley. 



