26 NEW YORK STATE MUSEUM 



In the curved stratum of garnet gneiss which is intercalated in the 

 midst of a mass of quartz schist and quartz-mesh Hmestone north- 

 west of North Russell, a similar but much simpler structure is re- 

 peated twice on a smaller and a larger scale respectively. Near the 

 thin end of this layer, a jog is observed in the trace of the strike, 

 where an open northwesterly-pitching monoclinal fold is abruptly 

 developed. The formation thickens southward, and near the top 

 of the east shoulder of the hill it turns suddenly eastward as a result 

 of a pitching C-shaped flexure in the rock. The exposure of this 

 feature in the field is unsatisfactory, but not only is the interpreta- 

 tion in harmony with the tectonic features of adjacent areas, but the 

 observed outcrops admit of no other explanation. The formation in 

 all likelihood continues to thicken eastward and turning southeast- 

 w^ard joins the mass of gneiss mentioned above. 



Another considerable thickness of garnet rock, accompanied by 

 limestone and a variety of impure schists, is found northeast of 

 Pyrites occupying the northwest half of the reentrant in the promi- 

 nent granite boss near that village. The formation is thickest near 

 the middle, thinning out toward the southwest, and dividing into 

 two strata northeastward. The latter are separated by a layer of 

 limestone, and the lower horizon, near the center and at its northern 

 extremity, has become involved in the marginal contortions of the 

 adjacent granite intrusive. These structural features, however, are 

 more fully described on page lOO. 



The western end of the belt is underlain, or may in part be later- 

 ally replaced, by a succession of impure calcareous and quartzitic 

 schists, which apparently give place on the northeast side to a thick 

 mass of limestone. Unfortunately the marginal relations between 

 these sediments and the Pyrites gabbro are obscured by a heavy 

 deposit of Quaternary material, and the intervening area had to be 

 mapped simply as inferred Trecambrian. 



The garnet gneisses of which account has thus far been taken 

 have been considered without hesitation as true Grenville sediments ; 

 their general association with quartzitic and calcareous strata, and 

 their frequent alternation with thin laminae of limestone lend 

 strong support to this view. The origin of other garnet gneisses, 

 however, now to be described, is not so self-evident; but it is be- 

 lieved that the data at present obtainable favor the idea that they 

 are primarily of Grenville age. They have accordingly been mapped 

 with the others as one geologic formation, and no distinction has 

 been made on account of bulk or structure, or supposed contact 

 relationships. 



