PALEOZOIC ROCKS OF THE CANTON QUADRANGLE 49 



Preglacial and Glacial 



Preglacial erosion and drainage. Wihatever form erosion took 

 during the long stretches of later Paleozoic, Mesozoic and Tertiary 

 time, whether canyon-cutting through rapidly uplifted strata with 

 subsequent reduction of the divides, or slow, continuous, base- 

 leveling of a slowly rising surface, its net preglacial product could 

 not have differed much from that of today. Professor Fairchild 

 believes that the stream adjustment on this northwestern side of 

 the Adirondacks was similar to that now existing on their south- 

 western flank, namely, that a major valley was developed in a 

 tangential direction along the surface contact of the crystallines 

 with the edge of the overlapping Paleozoics, and that this received 

 the radial flow from the highland within.^ Our concealed zone 

 with its absence of outcrops along the Paleozoic frontier may be 

 a local remnant of the course of this ancient trunk valley through 

 this heavily ice-scoured trough. More certain is it that the ancient 

 rock-valley of the Raquette past South Colton continues northwest 

 from Higley Falls into the southeast corner of our sheet, where 

 it is now occupied by only tiny Conner (Leonard) brook. The 

 present deflection of the Raquette toward Colton and Potsdam is 

 maintained merely by a weak remnant of its gravelly delta built 

 in Lake Iroquois (see beyond). Since the other known rock-valleys 

 on the map, except that of the Grass at and above Pyrites, are in 

 belts of weak rock accordant with the direction of glacial flow, it 

 seems unsafe to assert for them any preglacial significance. Some 

 are more truly resurrected pre-Potsdam. Over the Paleozoic area 

 the rock surface appears to be almost featureless, the present relief 

 being wholly that of the glacial drift. 



Glaciation. The Pleistocene glaciation of this district was 

 from the northeast, and the heavier movement seems always to have 

 been influenced, at least the basal currents, by the course of the 

 St Lawrence trough and its included strike ridges. The thin edge 

 of the waning ice appears, however, to have had a spreading flow, 

 and as this gave the rocks their final polishing, the compass direc- 

 tion of the striations is generally about south, frequently two or 

 three degrees east of south. The drumlinized hills show a similar 

 orientation, as they too were the product of this thin spreading 

 ice margin. The drumlins in particular reveal a curving aline- 

 ment, swinging slowly and regularly from southwest in the northern 



' N. Y. State Mus. Bui. 145, p. 141-45. 



