THE PRECAAIBRIAN ROCKS OF THE CANTON QUADRANGLE 35 



interstratified sedimentary type first described, nor to the peripheral 

 or contact-metamorphic type. The formation is of greater magni- 

 tude than any other body of similar material found on the qilad- 

 rangle, and at the same time the structural phenomena exhibited 

 within its mass are of greater complexity than those of the cases 

 previously cited. 



The garnet gneiss (see colored map) occupies the larger part of 

 the prominent S-shaped isoclinal fold. This is some 6 miles in 

 longest dimension, extending from the eastern edge of the sheet to 

 within three-tenths of a mile of the Canton-Russell road. The 

 greatest exposed thickness of the formation is found by measuring 

 across the middle limb of the fold, along a line about one and two- 

 tenths miles east of the Beach Plains Church, in the vicinity of the 

 zigzag, north-south road. It would seem, judging from the struc- 

 tural conditions described later (see page 97), that the possibility of 

 duplication of the formation at this point is very remote. The 

 average dip being 30 degrees, and the breadth of outcrop 5200 

 feet, the maximum thickness is seen to be approximately 2600 

 feet : from this, however, must be deducted an indeterminable 

 amount (probably not over a tenth) to allow for the numerous 

 intercalated acid and basic sheets and sills of small indiv^idual 

 thickness ; although the stratigraphic thickness indicated here is 

 small in comparison with that measured in certain other Precam- 

 brian localities, as in Ontario (Adams and Barlow, 1910, page 33), 

 it is nevertheless interesting and encouraging to find measurable 

 remnants of stratigraphic units preserved in this part of the Adiron- 

 dacks in the midst of such widespread structural confusion. Al- 

 though, to summarize conclusions briefly, the writer interprets this 

 formation as a metamorphic member of the Grenville sedimentary^ 

 succession, it is to be pointed out that some of the features shown, 

 could be accounted for equally well on the hypothesis that it is an 

 igneous gneiss analogous to the pink granite. Its correlation with 

 the Grenville is nevertheless made on lithologic grounds, and the 

 pseudo-igneous phenomena can be accounted for satisfactorily on 

 this assumption (see pages 37-39). 



Its typical composition may be observed at several widely sepa- 

 rated points, located respectively on the lower, middle and upper 

 limbs of the sigmoid. The first locality is the ridge forming the 

 southeast wall of the garnet gneiss-limestone amphitheater already 

 described (page 20). It is in all essential respects a quartz-ortho- 

 clase-biotite gneiss, spotted irregularly with one-quarter to one-half 

 inch skeletal garnet crystals. Minor variation in the relative propor- 

 tions of these constituents results in darker and lighter bands and in 

 3 



