﻿GEOLOGY OF THOUSAND ISLANDS REGION 73 



8' Gray magnesian limestone, weathering whitish, fairly massive be- 



low, upper 2 to 3 feet thin bedded and earthy 



i' 6" Curdled looking intergrowth of blue limestone and gray, mag- 

 nesian limestone, the former weathering most rapidly with pro- 

 duction of fantastic weathered surface 

 19/ Alternating, gray, earthy, impure magnesian limestones, and thin, 



shaly looking partings, limestone weathering at times to a green- 

 ish tinge, at other times whitish 



2' Greenish to olive, calcareous shale 



2' Greenish, calcareous sandstone, coarse, well rounded sand grains 



set in calcite paste 



72' V2 



The lower 4 feet of the section belong with the basal, sandy por- 

 tion of the formation, .without any question, so that the actual 

 base is nearly reached. Above is a thickness of 28 feet of im- 

 pure, magnesian limestone before reaching the base of the fos- 

 siliferous black limestone, the most characteristic member of the 

 lower division. Plate 16 is a photograph of beds of this hori- 

 zon exposed in the creek bed just north of the road 1% miles east 

 of Perch lake. In the section here 14 feet only of gray magnesian 

 beds are found underneath the black limestone, as against the 28 

 feet of the Perch lake section. A mile further east these have dis- 

 appeared letting the black limestone down on the basal sand beds, or 

 rather bringing them up to it. 



Judging from other sections the concealed 10 feet of the section 

 is occupied by weak, earthy, thin bedded, whitish limestone, and 

 the section would be capped by a very massive, blue, subcrystalline 

 limestone which forms a strong shelf 'everywhere through the 

 district. 



The best sections of the upper division are all on the Clayton 

 quadrangle. One measured up the bed of the small creek which 

 tumbles down the bluff into the Chaumont river a mile southwest of 

 Depauville is as follows : 



Brittle, light gray, subcrystalline limestone 



Thin bedded, brittle limestone, mostly dove, but with beds of 



grayer limestone 

 Massive layer of dove limestone 

 Irregularly bedded, gray to white, earthy limestone, mostly thick 



bedded ; midway is somewhat sandy 

 Thick bedded, uneven, gray limestone 

 Thin bedded dove limestone in 3" to 6" layers 

 Gray white, earthy, irregular limestone, both thick and thin beds 

 Dark and light gray, brittle, subcrystalline limestone 

 Gray white, impure, earthy limestone 

 Brittle, blue gray, suberanular limestone 

 Impure, earthy, white limestone, irregularly bedded 

 Hard, blue gray, subcrystalline limestone 



1" 



I 



8" 



16' 



1" 







I 





10' 



8" 



5' 





3' 





4' 



2" 



5' 



4" 



1' 



8" 



1' 



8" 



5' 



10" 



1' 





