78 THE ROYAL SOCIETY OF CANADA 



graptolites. The Arenig of Wales has been built up with fine mud 

 deposits, like those of the St. John, but there is also much effusive 

 materials of volcanic origin, but in the Canadian rocks of equivalent 

 age there are no volcanic rocks whatever. The graptolite beds are 

 not the highest beds of the St. John group, for there are overlying 

 shales with thin sandstone seams that contain a higher fauna of 

 the Ordovician, but still in the lower part of that System. 



The enormous denudation to which this region has been sub- 

 jected since early Palaeozoic times, has left remains of this highest 

 division of the St. John group only in the deep synclines into which 

 its strata have been thrown, and in many cases and over large areas 

 these strata have been so much altered that the abundant remains of 

 marine animals which it once contained, have to a great extent been 

 obliterated; we only know from the scattered patches with fossils 

 which it still holds, that it was accumulated very slowly, and 

 marks the passage of a long period of time, roughly represented by 

 the Upper Cambrian and the Lower Ordovician. 



The black color which characterizes much of the fine shales of 

 this division is to be attributed to the large amount of organic matter 

 set free by the decomposition of the great number of Hydrozoan organ- 

 isms which flourished in the protected waters of these Cambrian 

 basins. 



Except in the St. John basin this upper part of the St. John group 

 has been much attenuated or failed of deposition as it has not been 

 recognized in the others. However, it recurs in Cape Breton where 

 the shales with Dictyonema have been found and also the overlying 

 Tremadoc fauna. The strata, however, had not been so saturated 

 with bitumen as the rocks of corresponding age in the St. John basin. 



CONCLUSIONS. 



From what has been said in the preceding pages the following 

 conclusions may be drawn as to the physical conditions that prevailed 

 in the southern part of New Brunswick during Cambrian and early 

 Ordovician times. 



The Cambrian Age was preceded or ushered in by wide-spread 

 volcanic eruptions on a partly or wholly emerged land. 



Complementary to the building up of volcanic ridges came the 

 sinking of adjacent parts of the earth's crust, producing sea-basins 

 in which the Etcheminian and St. John strata accumulated. The 

 first beds of the St. John group were gray sandstones now strongly 

 cemented by interstitial si.ica. These were followed by glauconiferous 

 sandstones and sandy shales (Protolenus beds) ; then pure gray shales 



