ROCKS OF THE ATLANTIC COAST OP CANADA, ETC- 811 



Of Ordovician rocks other than the Quehec group and nearer 

 to the Atlantic margin, perhaps the best example is that of the area 

 in Central and Western New Brunswick described by Prof. Bailey*. 

 This consists, in ascendiug order, of (1) gneiss and mica-schist with 

 chloritic and hornblendic schists, (2) grey and purplish micaceous 

 sandstones and slates with limestone and conglomerate and f elspathic 

 slates, (3) black graphitic and pyritous slates, (4) schistose felspathic 

 rocks and conglomerates, (5) amygdaloid and felsite with sandstone 

 and slate, (6) felsites capped with sandstones and slates, often 

 chloritic. These remarkable rocks, which are of great thickness and 

 have evidently experienced much metamorphism, have been found 

 at one locality to contain fossils of Trenton age equivalent to Bala 

 and Llandeilo. Similar rocks come out from beneath Silurian beds 

 in various parts of the hilly districts of Nova Scotia f. They 

 resemble the Cumberland Ordovician more nearly than other British 

 developments of these rocks. In the continuation of these beds in 

 Northern New Brunswick Graptolites were discovered some years 

 ago by Mr. Eobb and Dr. Ells, of the Canadian Geological Survey, 

 and are believed to be of Upper Ordovician age. 



Y. The Silueian System. 



In the inland plateau of North America this period begins with 

 shallow-water conditions passing into the great and long- continued 

 depression marked by the Niagara Limestone. There is then a second 

 elevation, that of the Salina, succeeded by the very widely distri- 

 buted Helderberg Limestones. There are thus two depressions sepa- 

 rated by an intervening elevation. 



In Newfoundland the Silurian rocks occur in a narrow trough 

 extending through the centre of the island, and, so far as can be 

 ascertained from the Eeports of the Survey of Newfoundland, are not 

 dissimilar from the exposures in Nova Scotia. 



In the latter province the great limestones are absent or repre- 

 sented by comparatively insignificant and impure bands. Shales 

 with some sandy beds (Lower Arisaig beds of previous papers) 

 represent the Clinton and contain GraptolitJms dintonensis ; coarse 

 impure limestone and shale (New Canaan beds of previous papers) 

 correspond to the Niagara, holding characteristic corals of this age, 

 and shaly beds with thin layers of limestone (Tipper Arisaig of pre- 

 vious papers) represent the Helderberg. In Nova Scotia these 

 occur in the New Canaan, Arisaig, and Pictou districts, and their 

 characters correspond to those seen in Newfoundland, New Bruns- 

 wick, and Maine. In the Cobequid Mountains of Nova Scotia, 

 however, and in New Brunswick, these beds, especially in their 

 upper part, show great contemporaneous emissions of igneous rock. 

 These are partly felsitic and partly doleritic and amygdaloidal. 

 They correspond in age with those isolated igneous masses of the 



* Report G-eological Survey of Canada, 1884-5. 



t Quart. Journ. Geo!. See. 1850. ' Acadian Geology ' and Supplement. 



