352 



THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



?j 



jj 



The rocks of Division B, as Mr. Vennor says, were 



" seen to rest iiumediately upon the gneisses, Nos. 2 and 3 of Division A^ but 

 ■wlietbcr conformably or not is a question yet to be investigated, as in the locali- 

 ties where they are best represented, the massive diorites and greenstones, which 

 form the base of this division, do not offer any clear marks of stratification. 



The rocks of this division wore thought to closely resemble the 

 Huronian. Division C contained Eozo'&ii Canadense, but no evidence of 

 importance was brought forward to prove its relations to A and B. 

 Overlying all, Trenton limestones were found. 



In the lleport of Progress for 1870--71, Division A was regarded by 

 Mr. Yennor as Laurentian,.and B as probably Huronian. He further 

 states : — 



" The dolomites and schists of division C lie unconformably upon the gneiss 

 and crystalline limestones of A, while the true position of tlie diorites and 

 chloritic schists of division B, appears to be at the base of C; Avhcre, however, 

 they are not un frequently wanting, suggesting a probable unconformity of 

 these both with the upper and lower divisions." C is mentioned as being " seen 

 in contact with the chloritic schists of B, without any apparent unconfonnity. 

 Q. c, pp. 310, 311.) 



In the lleport of Progress for 1871-72, Mr. Yennor remarks of Di- 

 vision A : — 



*' The age of the granite [A], on which these gold-bearing rocks [B] rest, is 

 not yet satisfactorily <leteruiiued. That it is of more ancient date tlian the 

 latter, k I think clearly shown by the manner in which they repose upon its 

 flanks, and conform to its general outline. My own conviction is, that this, 

 and other like masses of granite, met throughout the Hasthigs district, repre- 

 sent eruptions which probably took place towards the close of the Laureutian 

 period, or at some time prior to the deposition of the greenstones, schists, dolo- 

 mites and limestones of Divisions B. and C." (I. c, p. 130.) 



In the Report for 1872-73, Mr. Yennor remarks : - 



<^ The red granites [A] also occur in many localities throughout the area just 

 described, but in a very irregular manner, so as to render it difficult to deter- 

 mine their age in relation to the other rocks In the vicinity of the East 



and West Mountains in Grimsthorpe, they are unstratified, and often appear 

 to be of more recent date than the white mica granites, and even than the dio- 

 rites of division B." (I. c, p. 140.) 



In the Report of Progress for 1874-75, Mr, Yennor groups the rocks 

 of Lanark County as follows : 



I. Mica Schist Group. 

 IL Dolomite and Slate Group. 



