I04 NEW YORK STATE MUSEUM 



which it is essentially parallel, while in the Pierrepont sigmoid the 

 two are almost at right angles. The difference, however, is one 

 which is wholly dependent upon the amount of tilting which the 

 beds and axes have undergone subsequent to their isoclinal compres- 

 sion; and being thus a matter of degree only, is not considered of 

 vital consequence. 



The structure which shows the greatest essential similarity to the 

 Canton folds is that which is very briefly described by P. J. Holm- 

 quist (1910, pages 104-6) as occurring on the Island of Uto, a short 

 distance southeast of Stockholm, Sweden. Here the beds are ver- 

 tical or nearly so, with the effect that the areal geological map is in 

 reality a cross section of the fold. The halletlintas and limestones 

 of the Archaean are seen to describe a tightly compressed C-curve 

 about 3 miles long, analogous to the Alpine fan-folds, but plunging 

 vertically into the ground. In regard to the history of this double 

 fold, Holmquist inclines to the view that it was compressed first and 

 uptilted later, rather than to the alternative view that it is due to 

 the buckling of an upright formation produced by horizontal 

 movement in a vertical plane. Holmquist's general explanation ap- 

 pears applicable to the transverse folds on the Canton sheet, wherein 

 one may discern a period of compression in which the isoclines were 

 formed through horizontal thrust, followed by a period in which 

 they were tilted to their present attitude. Referred to the scheme 

 proposed above, the folds at Franklin Furnace lie at about the stage 

 indicated by figure 26; the C-fold of the Island of Uto at about 

 figure 30, the most advanced of all. At the latter place, however, 

 the axial plane has not been tilted over beyond the vertical, or if so, 

 has, through subsequent readjustment been brought back to the up- 

 right position. 



The relations disclosed by this type of structure are admittedly 

 abnormal. In the statement, " Pitch is usually nearly parallel to the 

 dip of the axial plane," certainly an unusual type of structure is indi- 

 cated, so far as one may judge from current textbooks on tectonics, 

 such as those of Margerie and Heim (1888, pages 49-87) and 

 Wilckens (1912), in which no mention is made of such a possibility. 

 Nevertheless for the southeast part of the Canton sheet this relation- 

 ship is the normal or usual one, and from the point of view of 

 general post-Archaean tectonics, it seems to demand special explana- 

 tion. Not only have the older formations of the northwest Adiron- 

 dacks been subjected to intense compression Hke that characteristic 

 of the Alps, but subsequently buried beneath now vanished mountain 



