GLACIAL GEOLOGY OF THE SARATOGA QUADRANGLE 45 



outcrop of rock, judged to be a dike. I was unable to determine 

 whether the bed of the swamp is rock or till. 



In addition to the large swamps occurring in the Adirondack 

 highlands and shown on the topographic sheet, there are many small 

 areas of swampy or partially drained lands, occupying depressions 

 in the mantle of glacial deposits. They represent glacial lakes or 

 ponds which have been filled in by sediments and overrun by vegeta- 

 tion in the recent epoch. The location and areal extent of some of 

 these have been indicated on the map. 



REVIEW AND SUMMARY 



In the region within which is included the area of the Saratoga 

 quadrangle the glacial period, or Ice Age, was broken by at least 

 one interglacial epoch. This deduction is made from the fact that 

 the Hudson river in its course across the southeastern spur of the 

 Adirondack mountains occupies an indubitably geologically recent 

 valley of trenchlike form and yet one that is cut in till. 



The beginning of the interglacial epoch was marked by the with- 

 drawal to the north of the ice sheet which had covered the general 

 region. As the ice melted, it left behind the earthy materials which 

 had been carried at the bottom or inclosed in the ice mass. An 

 accumulation of this debris, or drift, across the Paleozoic basin 

 somewhere south of Corinth, caused a blocking of the drainage and 

 the waters coming from the north, as the ice front receded, found 

 a passage across the Adirondack country east of Corinth, following 

 a line of preglacial intermountain valleys. The location of the drift 

 dam can not be determined, but it may be supposed that the heavy 

 deposits in the Greenfield locality then extended westward across 

 the basin. 



The end of the interglacial epoch was marked by a readvance of 

 the ice. The mantle of debris, or ground moraine, left by the 

 melting of the earlier ice sheet, was now largely scraped from the 

 higher rock surfaces and redeposited in the valleys and depressions 

 that had developed, through weathering and stream erosion during 

 the time of absence of ice. The renewed abrasion by ice action also 

 furnished added materials. It is possible, too, that where the previ- 

 ous aggregations of drift lay over depressed areas, as in the basin, 

 the readvance of the ice sheet developed drumlins. This view of the 

 origin of drumlins is favored by the facts of their distribution on 

 the area of the Saratoga quadrangle considered in connection with 

 the evidences of a second advance of the ice. 



