gS NEW YORK STATE MUSEUM 



Precambrian structures, provided, however, that isochnal or recum- 

 bent folding on a large scale has not taken place. This principle 

 can therefore, in all probability, be applied to the Eddy vicinity; and 

 if so, the calcareous series of this district rests upon, and hence is 

 younger than, the sediments successively exposed on going north- 

 ward. The schists of the first Grenvilie belt west of Canton are free, 

 so far as the writer is aware, of intercalations of limestone. As 

 hinted earlier, there seem, therefore, to be two separate horizons, 

 or subordinate formations, in the Grenvilie of the western part of 

 the sheet, a lower predominantly micaceous, and an upper cal- 

 careous, which have been bulged apart by the introduction between 

 them of a bluntly lenticular body of granite. 



Passing to the southeast of the broad sill of granite which runs 

 from Eddy to Canton and beyond, one enters a region where ex- 

 treme simplicity and intricacy are found side by side. x\ short dis- 

 tance south of Martin's comers (the first crossroads north of Little 

 River, on the Canton-Russell road) the outcropping edge of a lime- 

 stone stratum crosses the road. The border of this formation is 

 marked by a zigzag line of low intermittent bluffs. The reentrant 

 angles, three in number as plotted on the map, indicate the outcrop- 

 pings of low-pitching anticlinal axes, between and adjacent to which, 

 corresponding to the salient curv^atures, there are similar shallow 

 spoonlike basins, the ends of which are marked by low, lo to 15 foot 

 escarpments. Although the exact direction of the pitch or axes of 

 these gentle folds could not be determined, on account of the absence 

 of discernible directions of elongation, there can be little doubt that 

 they pitch toward the northwest or west-northwest at a ver\' low- 

 angle, somewhat under 5 degrees. 



PIERREPONT SIGIMOID 

 It is interesting, by way of contrast, to pass from these gentle un- 

 dulations in limestone, to the unique Pierrepont sigmoidal isocline 

 which has already been referred to. Plate 18, upper figure, shows a 

 similar structure in miniature; the actual specimen photographed 

 came from the crumpled mass of garnet gneiss just southwest of the 

 Little River crossroads, being oriented approximately parallel to the 

 larger sigmoid under consideration. Though not directly connected 

 with the latter in the field, its smaller dimensions admirably 

 fit it to serve as a model round which the discussion as to the nature 

 and origin of this type of structure may be centered. Its genesis 

 and history are probably identical with those of the big sigmoid, and 



