'I'.H) c. II. ciiADwicK — i'()s'r-()i;i)()\i(iAN 1)j:f()Umatj()X 



r(M)iii for tliL'm uii the Eaquette River between the known Theresa and 

 pre-Cambrian outcrops at Potsdam village.' and the formation presuma- 

 bly cuts out somewhere in the interval to reappear just east of Potsdam. 

 There can he no question of the interruption of the lower or typical red 

 sandstone^ since the white beds are seen to rest directly on the crystal- 

 lines in the more northerly outliers. 



FOBM AND CliARACTEU OF TIIJ-: FuLDS 



Scrutiny of the map (figure o) reveals an interesting relation betAveen 

 the folds there indicated and the belts of ])re-Cambrian rocks that are 

 seen disappearing beneath them. From the way in which the Paleozoics 

 here lap around the crystallines, the area is favorably located to exhibit 

 this relation, which became apparent to the writer while yet ignorant of 

 Logan's and unmindful of Cushing's contributions. Here, as in their 

 areas, the alinement of the major axes is northeast-southwest parallel 

 witli the valley. But instead of the secondary set being gridironed over 

 these at right angles in the fulcral direction of the Frontenac axis, the 

 minor distortions in this region are dominated Ijy the diagonal course of 

 the underlying pre-Cambrian belts. With less drift-mantle this would 

 likely become even more apparent. 



The question at once intrudes as to whether these very gentle undula- 

 tions are not initial dips of strata laid down on the uneven surface of the 

 much eroded crystallines or induced merely by \ertieal compression dur- 

 ing consolidation. But the proofs of actual deformation are also to be 

 i'omid. Figure 4 shows crumpling of the limestone layers in the old 

 quarry at Yaleville, on the west bank of the Raquette, a mile below Xor- 

 wood. Figure 5 is a remarkable inverted buckle (syncline) in these 

 same Bwkmantown dolomites two miles farther down the river at Nor- 

 folk; this crosses the stream, the water of which is seen reaching up into 

 its trough. Neither of these are conclusi\e, since similar structures are 

 often ascribed to glacial or other agencies, though nothing quite like the 

 latter instance has come to the writer's notice hitherto. But in the Pots- 

 dam outliers, in the southern half of the quadrangle, more convincing 

 phenomena are at hand. A notable chain of these outliers has been pre- 

 served from erosion in the Grrenville marble belt of Harrison Creek and 

 Grass Eiver (see figure 3). These occupy the middle of a pre-Potsdam 

 Valley, on either side of which the harder granite gneisses rise from -K) 

 to 100 feet above these Potsdam remnants. .\11 of these patches exhibit 



"The type locality iov the Potsdam i ivd i is luiir miles farther up the Raquette iu a 

 pre-Cambrian embayment. 



