Section IV., 1914 [69] Trans. R.S.C. 



The Physics of the Cambrian Formation in Eastern Canada, and the 

 peculiarities of its Faunas. 



By G. F. Matthew, D.Sc, LL.D. 



(Read May 27, 1914.) 



Certain puzzling variations in the Cambrian faunas of eastern 

 Canada have been observed by the writer in the course of his study 

 of these faunas, that are worthy of more than a passing notice. These 

 are not easily explained as changes due to the vertical relations of the 

 faunas, but seems rather to be the result of special environment, leading 

 to the introduction of new types by migration or otherwise. It 

 seems, therefore, desirable to say something more than has hitherto 

 been attempted on the physics of the several Cambrian basins in 

 eastern Canada and their relation to faunal changes. 



Of the several basins of Cambrian rocks in eastern Canada, 

 one may take as the standard, those of southern New Brunswick, 

 as having the fullest representation of Cambrian forms of life ; and as 

 containing also several Ordovician faunas. It is only by the contained 

 animal remains that we know that certain faunas of the latter system 

 are present there, near the top of the terrane, but over large areas both 

 the upper Cambrian and the Ordovician faunas have been obscured 

 by metamorphism and not infrequently entirely removed by 

 denudation. 



The observer will note that there were three terranes or series 

 of deposits in this region very diverse in their aspect and probably 

 of different chronological value; these consecutive terranes have been 

 distinguished as the Coldbrookian and Etcheminian terranes and the 

 St. John Group. We propose to consider the faunas of the first and 

 second as giving the initial conditions prevalent at the opening of the 

 Palaeozoic Age in this region, and to refer briefly to some interesting 

 faunal groupings in the St. John group. 



COLDBROOKIAN TERRANE. 



The St. John basin is that which gives us most fully the physical 

 history of this region of the earth's surface in the earliest Palaeozoic 

 time. On both sides of this basin, and simultaneously or nearly so, 

 there bursts forth eruptions of basic and acid lavas, which were piled 

 up in the mountain masses that can be seen to run parallel to each 



Sec. IV, 1914—6 



