Section IV, 1922 [47] Trans. R.S.C. 



Some Outliers of the Monteregian Hills 



By W. V. Howard, B.A. 



Presented by Frank D. Adams, Ph.D., D.Sc, F.R.S., F.G.S., 



F.R.S.C. 



(Read May Meeting, 1922) 



Introduction 



During the summer of 1921 the writer investigated a series of 

 small basic intrusives which occur about twenty-five miles west of 

 Montreal, and a detailed pétrographie study of the rocks of which 

 they are composed has shown that they are closely allied to, and form 

 part of, the extensive series of alkaline rocks which have come to be 

 known as the Monteregian Petrographical Province. The work was 

 carried on under a grant from the Honorary Advisory Council for 

 Scientific and Industrial Research. 



It is the purpose of this thesis to describe the field occurrence 

 of these western outliers, and by a detailed description of their petro- 

 graphical and chemical composition to show I heir genetic relations 

 with the already accepted Monteregians. 



Previous Work 



The name Monteregian was given by Dr. F. D. Adams to a 

 series of hills, eight in number, which extend across the Eastern 

 Townships of the Province of Quebec, and which are members of a 

 single Petrographical Provin^ce.^ This province was originally con- 

 sidered by Logan to include Brome, Shefford, Yamaska, Rougemont, 

 Beloeil, Mount Johnson, St. Bruno, Mount Royal and Rigaud Moun- 

 tains.- O. E. Leroy showed, however, that Rigaud Mountain was 

 not a Monteregian, but was rather an outlier of the Laurentians. 

 Besides describing the main intrusions, Logan also noted the occur- 

 rence of a number of dykes, notably those at Chambly, Montreal, and 

 Lachine, as well as a number of breccias at St. Helen's Island and Isle 

 Ronde in the St. Lawrence River and at St. Anne de Bellevue and 

 Isle Bizard.^ 



^The Monteregian Hills, a Canadian Petrographical Province, by F. D. 

 Adams; Journ. of Geol., Vol. XI, p. 239, 1903. 

 =Geology of Canada, 1863, pp. 655-669. 

 ^Geology of Canada, 1863, pp. 355-358. 



