[ells] interesting PROBLEMS IN NEW BRUNSWICK GEOLOGY 23 



bee, wliieh he had recently studied and had decided to be of pre- 

 Cambrian age, thus opposing the views long held by Sir William Logan 

 as to their geological position. The occurrence of Cambrian slates on 

 the flanks of this ridge in New Brunswick confirmed the opinion ex- 

 pressed by Dr. Hunt, that these rocks were much older than had been 

 supposed. They were in consequence removed from their position in 

 the l)e*vonian and placed in the pre-Cambrian series. 



In determining the exa.ct horizons of the Palœozoic formations, the 

 work was rendered diflicult from an almost entire absence of fossils in 

 most of the rocks outside the Cambrian and Devonian. Occasionally 

 when such were found they were too imperfect for determination, and 

 so were of but little value. Occasionally a patch of Silurian rocks show 

 the presence of organisms, but the larger areas are practically barren. 

 In lithological character there is a marked dissimilarity between the 

 supposed Silurian and Cambro-Silurian formations of this province as 

 compared with those found in Quebec and Ontario, which are regarded 

 as their equivalents, and where the nomenclature of the New York Sur- 

 vey has been closely followed. So great is this difference in the case 

 cf the New Brunswick rocks that in the absence of fossils the determina- 

 tion of actual horizons is often practically impossible. 



The oldest rock group in the southern part of the province has 

 already been referred to as probably of Laurentian^ age, under its old 

 designation, the " Portland group." This group, with another called 

 the Coldbrook, comprised what in 1865 was known as the Azoic. The 

 Portland included a considerable thicloiess of crystalline rocks with some 

 schists, and was easily traced for some miles to the north-east of the 

 city. But when in the course of this investigation other outcrops of 

 apparently similar rocks were foimd to the west in Charlotte county, 

 where there is no overlying Cambrian formation to fix the position de- 

 finitely, the attempted correlation of such groups of crystalline rocks, 

 M'ith the so-called Laurentian of St. John, could not be conclusively 

 effected. Still, largely on lithological grounds, such a correlation was 

 made, more particularly in regard to certain areas of crystalline lime- 

 stone and schist which occur on Frye's island and Letang, and this 

 classification remained in force for many years. 



During a recent detailed investigation of these crystalline rocks in 

 Charlotte county, it was found that the supposed Laurentian limestones 

 are merely highly altered Silurian sediments, with which are associated 

 a considerable thickness of squeezed eruptives, to which a schistose struc- 

 ture has been imparted, so that they now closely resemble the pre- 

 Cambrian schists near St. John. 



