﻿I46 NEW YORK STATE MUSEUM 



tuffs, permeated by thin seams and sheets of gypsum and fol- 

 lowed along their faces by enormous gypsum deposits. The 

 rock geology of the islands has received attention only once 

 and then in a careful though brief report made by Mr James 

 Richardson for the Dominion Survey during the summer of 

 1880, just 30 years ago, and published in the Geological Survey 

 of Canada, report for 1881. 1 Mr Richardson's keen insight into 

 the relations of these rock masses is a noteworthy characteristic 

 of his work, even though he frankly left many questions to be 

 illuminated. 



Stratigraphy. The only detailed section of these rocks given 

 by Richardson is taken from the sea front of Amherst island on 

 Pleasant bay and extending along the escarpment of Demoiselle 

 hill. This section of 856 feet (measured) shows that the hard 

 gray and mottled sandstones lie at the bottom and the soft deep- 

 colored red sandstones above. Yet a change of dip between the 

 lower and upper masses suggests a disconformity and necessarily 

 qualifies the assumption of vertical succession. At the base of 

 this whole sedimentary series lies a mass of partly compact but 

 for the most part badly broken volcanics with an extensive de- 

 posit of gypseous clay and an agglomeration of both together. 

 This seems to make the base of the section and produces the 

 curves of Demoiselle hill. 



This section of the sedimentaries is typical for the islands Grind- 

 stone and Alright, where there is opportunity for adequate exposure. 

 Probably the east shore of Grindstone affords a more favorable and 

 longer section than any other as here is a clean coast line from 

 House Harbor at the north to and beyond Red cape at the south. 

 Here it is seen that the red sandstones which cover all the shore 

 section from just south of Cape aux Meules to Red cape, are, as 

 everywhere else, quite horizontal, and they make a broad flat fringe 

 about the rather distant elevated interior. The sea has cut into them 

 like a mouse into a cheese, carving their frontage into marvelous 

 and bewildering zigzags, aisles and obelisks. Following these red 

 beds north to the cape, they pass without evident loss of conformity 

 or continuity into the gray hard sandstones which make the 

 " Meules." This apparent continuity of the soft red and hard gray 

 series is often seen and I am disposed to believe an approximate 

 explanation of it is to be found in the almost invariable presence with 

 the gray sandstones, when elevated into demoiselle hills, of the vol- 



1 Report of a Geological Exploration of the Magdalen Islands, p. 1-11 G. 



