52 NEW YORK STATE MUSEUM 



and with an indeterminable percentage of the unmapped black: 

 amphibolitic xenoliths so abundantly inclosed in the granite gneisses 

 of the western part of the quadrangle, the possibility of whose two- 

 fold origin seems to be particularly well favored in this area. But 

 the arnbiguity is always between a contemporaneous age, if the 

 schists are sedimentary or metamorphic, and a later, if they are 

 igneous ; they can not be older than the Grenville. 



From what was earHer stated incidental to the discussion of the 

 marginal garnet gneisses in the southwestern part of the quadrangle, 

 it is recalled that it was pointed out that certain amphibolites of 

 this vicinity held a significant median position with respect to the 

 sediments and the granite gneiss. The evidence was regarded as 

 favoring the view that such amphibolites are a final product of igne- 

 ous contact action upon the Grenville limestones' or calcareous 

 schists. 



It is noteworthy, however, that peripheral schists of such extreme 

 composition are not always present along the borders of the granite 

 area. Thus the southeast margin of the broad belt of granite which 

 passes through Canton village is not known to be actually bounded 

 by a continuous belt of rock of this character ; this lack may be due 

 in part to the failure of such a formation, if present, to crop out, 

 but in particular instances can be shown to be due to its absence 

 from the section. 



For example, at a distance of a mile or so upstream from the Har- 

 rison Creek bridge, a granite escarpment is intermittently shown, 

 which is underlain in all cases where the base of the igneous rock 

 is exposed, not by a black amphibolite like that described at Wood- 

 cock's rapids, but by a garnetiferous mica schist, which gives place, 

 below, to normal crystalline limestone. For the rest of the distance 

 to the corner of the sheet, as well as from Woodcock's rapids north- 

 ward to Canton village, no marginal amphibolite is to be observed. 

 Further, the oval granite area southwest of Canton, though it is 

 bordered by the same kind of Grenville rocks as enter the problem 

 elsewhere, does not exhibit a marginal amphibolite zone. Similarly 

 along the edge of the north half of the Pyrites granite, inclusions of 

 amphibolite are present, but there is no distinct aureole of horn- 

 blende schist, so far as can be judged by the outcrops; and finally, 

 the granite area southwest of Pyrites shows no amphibolite border, 

 except locally at points already described. 



From these data it is evident that if the marginal strips of horn- 

 blende gneiss at Eddy (see plate 5, upper figure), Woodcock's 

 rapids, and south of Pyrites are regarded as exomorphic contact 

 effects, the general absence of similar changes elsewhere against 



