GLACIAL GEOLOGY OF THE SARATOGA QUADRANGLE 3 1 



Corinth. Also we have the facts, above stated, that constitute evi- 

 dence, hardly to be questioned, that the valley is of recent geological 

 origin. 



2 The Adirondack^Hudson valley is wholly postglacial, that is, 

 has been formed and occupied by the river only since the withdrawal 

 of the ice of the latest, or Wisconsin, epoch. It may be supposed 

 that in preglacial times a stream heading somewhere in the course 

 of the present Adirondack-Hudson flowed westward and emptied 

 into the Luzerne river at Corinth and that a correlative stream 

 heading in the same locality and separated from the former by a 

 divide, flowed eastward to the Hudson plain. The courses of both 

 these streams were in the lines of intermountain depressions, due 

 to rock structure and rock weathering such as occur generally in 

 the Adirondack region. Thus a continuous valley, except as inter- 

 rupted by a low divide, extended from Corinth to the Hudson plain. 

 At the close of the Wisconsin epoch the Luzerne river became di- 

 verted into the course of this valley and reduced the divide, thus 

 initiating the present conditions. We have to note that according to 

 this view there should occur in the course of the present river a rock 

 gorge at the place where the divide was located. At Spiers falls, 

 which is near the middle portion of the course of the Adirondack- 

 Hudson, a rock channel occurs, as already described. The elevation 

 of the bed of the river at this place is 320 feet, or about 200 feet 

 below that at Corinth. We should therefore expect to find a rock 

 gorge with walls having a height of 200 feet plus the elevation of 

 the divide above that of the river at Corinth. No gorge of this 

 character occurs. 



The lower slopes of the valley at Spiers falls, moreover, are cov- 

 ered with till, and below Spiers falls where the valley widens, form- 

 ing relatively broad terraces, the bed of the river is on till. The till 

 in this locality is unquestionably in situ and was laid down on a 

 rock floor lower than the bed of the present river at that place. 



3 The Adirondack-Hudson Valley is inter glacial in origin. 

 During an interglacial epoch a stream from the north, follow- 

 ing the course of the preglacial Luzerne river, was diverted from 

 the old channel at Corinth and initiated the present Hudson valley 

 from Corinth eastward. The conditions determining this change of 

 course of the interglacial stream are unknown but may be assumed 

 to be heavy accumulations of drift south of Corinth. With the re- 

 advance of the ice sheet, at the close of the interglacial epoch, this 

 newly excavated valley became partially filled in with till. With 



