DAWSON ON THE LOWEIt CARBONIFEROUS ROCKS. 33 



Shubenacadie. 



Having thus described the Lower Carboniferous rocks, as they 

 appear in some of the best sections near the Gulf of St. Lawrence, 

 it may be interesting to compare their arrangement and lithological 

 character with those of the Gypsiferous formations of the central 

 part of the province, formerly supposed to be newer than the coal- 

 formation, but referred by Mr. Lyell, principally on the ground of 

 its fossils, to the lower part of the Carboniferous system. The 

 rocks seen on the estuary of the Shubenacadie furnish a good spe- 

 cimen of these deposits for the purpose of comparison. The sec- 

 tions on this estuary show several extensive masses of stratified 

 deposits, differing considerably in their mineral character, and 

 separated by faults in such a manner that their true relations do 

 not appear. Most of these masses consist of Red sandstones and 

 marls, with beds of gypsum and limestone. These, when compared 

 with the corresponding rocks in the Pictou and Antigonish sec- 

 tions, appear to differ only in their apparently greater mass, and 

 especially in the thickness of the deposits of red sandstone and 

 marl. The upper bed of gypsum on Right's River is succeeded by 

 a level tract affording no section ; and from the two sections, repre- 

 senting the outline of the surface near the gypsum of Ogden's 

 lake and the East River, it will be seen that the present outline of 

 the surface is caused by a great removal of the softer beds. 



Section VI. 

 Near Ogden's Lake, Antigonish (showing denudation). 



N. S. 



c. Gypsum and limestone. 



6. Grey and soft red sandstones. 



a. Syenite and greenstone. 



One of the most remarkable rocks on the banks of the Shubena- 

 cadie is a great bed of compact and laminated non-fossiliferous 

 limestone, near the mouth of the estuary. This bed has its upper 

 surface broken up into a kind of breccia, and supports a great 

 thickness of soft red sandstone and conglomerate, with beds of 

 gypsum. It is also traversed by fissures filled with haematite and 

 ores of manganese. It rests upon a great thickness of hard, 

 brownish grits and shales, which appear in different places on the 

 road from Shubenacadie to Truro. The horizontal red sandstone 

 of Truro rests on the edges of these grits, which, near Truro, be- 

 come either vertical or dip rapidly to the north-east, and perhaps 

 also underlie some of the gypsiferous rocks of the Onslow hills. 

 From a consideration of all these circumstances, it appears probable 

 that these hard grits are the equivalents of the lower grits and 

 conglomerates of Antigonish ; and that the bed of limestone which 



VOL. I. D 



