CHERT FORMATIONS OF NOTRE DAME BAY 575 



structure. Such sections do not contain chert. These sections 

 are not simply different facies of the pillow lava series, but are 

 thought to represent a distinct series. As to the age of these two 

 series, evidence is scanty. That the first mentioned series contain- 

 ing chert is considerably older than the Upper Ordovician is indi- 

 cated by the relative degree of metamorphism, and particularly 

 by the finding of its characteristic green chert in conglomerates of 

 Upper Ordovician age. This series is probably of Cambrian age. 

 As to the other series which does not contain pillow lavas or chert, 

 we can only say that it is intermediate in age between that of the 

 old pillow lavas and the Middle Ordovician. 



ORDOVICIAN 



The known Ordovician rocks are represented in the lower sections 

 by volcanics and shales. The volcanics are principally pillow 

 lavas of andesitic composition and tuffs which are mostly acid. 

 Throughout Notre Dame Bay rhyolite flows are practically absent, 

 the rhyoHtic eruptives being clastic and represented principally by 

 tuffs which show somewhat waterworn fragments. Thin beds of 

 chert are often found associated with these tuffs. In some places, 

 the volcanics are wanting, and shales containing beds of chert take 

 their place, though a persistent black graptoUtic shale fixes the age 

 of these rocks as contemporaneous with sections showing volcanic 

 products. The graptoHtes are of Llandeilo age. In the higher 

 sections, there are sandstones and some conglomerates, both of 

 which are commonly red. In places on the east side of New 

 World Island, hmestones of Caradoc age are associated with 

 pillow lavas and volcanic breccias, some of which breccias have a 

 lime cement. At Burnt Arm, branching from Goldson Arm, a 

 pillow lava was seen with fossihferous Hmestone in the spaces 

 between the pillows. The lime mud must have been caught up 

 when the lava was extruded. Here, at least, the evidence for the 

 subaqueous nature of the pillow flows is clear. 



SILURIAN 



The Silurian rocks are principally sandstones and conglomerates, 

 usually red. Very thick sections are exposed, those studied being in 

 the extreme south of the bay and on the Exploits River. They are 



