650 H. L. ALLING GLACIAL LAKES OF CENTRAL ADIRONDACKS 



quartzite have been noted all over the four quadrangles. At Cascadeville, 

 between the two Cascade lakes, a boulder of Beekmantown limestone was 

 found. 



Large irregular slabs of Potsdam sandstone and quartzite are encoun- 

 tered in some of the brook valleys, where the drift is abnormally thick. 

 In the valley in which the old Weston iron mine is located, not far from 

 Keene Center, slabs are very common at an altitude of about 1,600 feet 

 and do not appear to be glaciated, the natural infeiencc being that a 

 ledge of the Potsdam existed there before the ice-invasion broke it up. 

 "The former extension of the Potsdam formation over all or the greater 

 portion of the Elizabethtown and Port Henry sheets is clearly demon- 

 strated by a small outlier observed by Professor Kemp." 5 . . . 



Dr. D. W. -Johnson, of Columbia, suggested to the writer that the saw- 

 tooth shape of the jSTiagara Mountain block fault in the southeast corner 

 of the Mount Marcy quadrangle may have been preserved by the deposit 

 in it of a ledge of Potsdam sandstone that was subsequently eroded and 

 destroyed by the ice, while most of the other faults, such as that contain- 

 ing the Cascade Lakes, have been completely leveled. 



Such phenomena lead directly to the conclusion that the Adirondacks 

 were submerged in the Cambrian sea to a much greater extent than was 

 formerly considered to be the case. 



CONSTRUCTIONAL WORK 



Moraines. — There is but little true morainal material 6 to be found in 

 the Adirondacks, nor have true drumlins been noted. Most of the drift 

 has been stratified by water. The movement of the ice during the maxi- 

 mum advance was too vigorous for deposition, and the material that was 

 deposited as the ice retreated was modified by the action of standing- 

 water. 7 



The recessional moraines appear to be largely confined to the fault 

 passes, being formed by the ice-tongues as they withdrew from the narrow 

 passes. At the southwestern ends in the broad valleys the rate of retreat 

 was slow and moraines were formed; but in the narrow defiles the ice 

 retreated faster, giving but little opportunity for the deposition of mate- 

 rial. Again, at the northeastern ends the ice-tongue paused long enough 

 to deposit another moraine. Other recessional moraines are to be found 

 in the more open valleys. Remnants of a crescent-shaped one are to be 

 noted in the southwestern corner of the Ausable sheet, where it has been 



5 Rudolf Ruedemann : IV. Y. State Mus. Bull., No. 138, p. 62. 

 8 H. P. dishing: N. T. State Mus. Bull., No. 115, p. 496. 

 7 I. H. Ogilvie : Jour. Geol., vol. 10, 1902, pp. 397-412, 



