THE PRECAMBRIAN ROCKS OF THE CANTON QUADRANGLE 95 



A study of the local pitch relations leads to consideration of the 

 larger tectonic features of the crystalline formations. That which 

 is true of the smaller crenulations holds good in general for the 

 larger folds of any region of structural unity. This principle was 

 enunciated by T. Nelson Dale as early as 1894 (see Pumpelly et al., 

 1894, pages 157-58). It was successfully employed by him and 

 his coworkers in the elucidation of the tectonics of the Green 

 mountains, and has since proved of universal application. In the 

 present study the key to the larger relationships was found in the 

 crenulations of siliceous, impure layers in the limestones, such as 

 is shown in plate 2, upper figure, and in the crumplings of thin peg- 

 matite stringers at the points of flexure of the large Pierrepont 

 sigmoid. 



This relationship can be recognized in each of the two parts into 

 which from this point of view the Precambrian area may be divided. 

 Northwest of the Pyrites gabbro-amphibolite formation, the west to 

 southwest pitch of the crumplings is reflected in the attitude of the 

 large folds where these are discernible, as, for example, one-half 

 of a mile north of Little River crossroads, and at the reentrant in 

 the granite south of Eddy. Similarly the northwest to west-north- 

 west pitch which determines the attitude of the minute puckerings 

 throughout the remainder of the Precambrian area, was learned to 

 control the orientation of northwest-pitching folds which measure 

 many miles across. Pitch is the one dependable structural element 

 to be found, the only feature common in one place or another to all 

 the crystalline formations within the quadrangle. 



In the area of Grenville gneisses north of Eddy, the pitch points 

 quite uniformly to the southwest, almost at right angles to its direc- 

 tion throughout the second or southeast portion of the quadrangle; 

 in other words, it is approximately parallel to the regional forma- 

 tional trend, and ordinarily departs but a few degrees from the strike 

 of the schistosity. This, indeed, in other regions of compressed 

 crystallines, as at Eranklin Furnace, New Jersey (see Spencer et 

 al., 1908, pages 24-25), is the normal relation between the pitch and 

 the foliation. It is abnormal nevertheless for the Canton quad- 

 rangle, but as to the ultimate cause of the discrepancy in these two 

 directions on adjacent portions of the quadrangle, the writer is c|uite 

 at a loss. 



Among folds of the Appalachian type, the true order of strati- 

 graphic sequence can be determined by measuring from below up- 

 ward in the direction of the pitch ; the same rule can be applied to 



