THE HURONIAN SYSTEM. CGI 



" Of these beds, Nos. 1, 2, and 3 do not extend so far west as St 

 John, and No. 4 diminishes very much in bulk in the rear of the 

 city, where it fills inequalities in the uppermost beds of the Portland 

 (Laurentian) series." 



Professor Bailey makes the following remarks on the age of these 

 rocks : — 



" The facts upon which depend the determination of this question 

 have already been given in the remarks on the age of the Portland 

 series, where also a parallelism is suggested between the Coldbrook 

 rocks and those of the Huronian scries of Canada. The parallelism is 

 apparent, partly in the fact that the former, like the latter, underlie 

 the rocks of the Potsdam group (of which the St John slates are here 

 the representatives), and partly in their mineral characters and the 

 absence of fossils. 



" It is impossible to read the description given of the Huronian 

 series in the reports of the Canadian Survey, without being struck by 

 the close resemblance which exists between the members of that 

 series, and what has been termed in New Brunswick the Lower Cold- 

 brook group. In both the prevailing rock is a hard compact slate, 

 almost universally of a dull grayish-green colour, with which are 

 associated pink and white, or greenish-white felspathic quartzites, 

 and at the base of the series, dark gray sandstones and conglomerates. 

 In both, also, dioritic or greenstone dykes are common, as well as 

 stratified amygdaloidal traps, the igneous outflows penetrating the 

 rocks as well as lying in regular beds among the strata, in which 

 they have produced excessive alteration. It will thus be seen that 

 the two formations are alike in their general character, as well as in 

 the conditions under which they were produced. Indeed, the resem- 

 blance is much stronger than would naturally be expected in series 

 so widely separated. 



" In passing to the upper member of the Coldbrook group, the task 

 of establishing a parallelism with either of the Canadian series is 

 much more difficult. Unless we regard the red quartzites and jasper 

 conglomerates of the Huronian rocks (Nos. 7 and 8 of the section 

 given in the Canadian Reports, near the Thessalon River), as the 

 equivalents of the red conglomerates and sandstones of the New 

 Brunswick group, no rocks approaching the latter in character are 

 I found, with the exception of the red sediments associated with the 

 copper-bearing rocks of Lake Siqjcrior. As these, however, have 

 been shown to be the probable equivalents of the Chazy group, which 

 occupies a higher horizon than the Potsdam beds, which here overlie 

 the rocks of Coldbrook, we must, for the present, be content to con- 



