[ells] interesting PROBLEMS IN NEW BRUNSWICK GEOLOGY 27 



To the north of this phice there is a broad belt of argillites, which 

 extends across the country from the vicinity of Millto^\^l on the St. 

 Croix into Queen's county. It is interrupted in pLaces by the large 

 granite mass of the eastern part of Charlotte county. Portions of this 

 slate series, as developed near the head of Oak bay, were at one time 

 regarded as possibly representing the Cambrian slates of St. John, but 

 of this no evidence could be found. As a whole the slates and 

 associated rocks of this series, to which the name " Dark argillite " was 

 given, was regarded in 1877 as possibly of Upper Silurian age, but in 

 default of definite evidence, in the final colouring it was decided to place 

 tiiem provisionally in the Cambro-Silurian system, until more definite 

 information could be obtained. Certain portions, however, in which 

 Silurian fossils were detected were separated. 



In this Upper Silurian portion, however, at that time were included 

 considerable areas of felspathic and other igneous rocks, the relations 

 of which to the fossiliferous Silurian were supposed to be such as to 

 warrant their inclusion in that system. These felsites are as a mass, 

 clearly intrusive. They cut across Silurian and Devonian sediments 

 at many points, and though they sometimes present an apparently bedded 

 aspect, this feature is due rather to flow structure than to true bedding. 

 In places these rocks are highly crystalline and porphyritic. 



They form a somewhat prominent series of hills along the north 

 side of Passamaquoddy bay, among which are the Chamcook moun- 

 tains. Mount Blair, and several others to the north and west of St. 

 George. A large area of these rocks extends eastward from the line 

 of St. Andrews railway at Chamcook lake, past the head of Bocabee 

 bay, till it connects with the great granite mass of the interior. The 

 masses of felsite which occur at many points are probably of the same 

 age as these granites, since they appear to pass into one another. Dyke- 

 like masses cut the formations below the Perry group and the basal 

 beds are largely made up of masses and pebbles of all sizes from the 

 felsite hills, the conglomerate often flanking their bases. 



From the fact that these volcanics, as a group, are evidently more 

 recent in age than the Upper Silurian, there is no valid reason why 

 tJiey should remain as an integral part of that system. In the revision 

 of the geology of this district, therefore, they have been separated from 

 the Silurian proper, and coloured as a portion of the volcanics series. 



About St. Stephen and for several miles along the St. Croix on 

 the Xew Brunswick side, and at Calais in [Maine across the river, there 

 are large masses of a greenish-grey rock, for the most part at least a 

 gabbro, which in 1870 was regarded as a gneiss, and referred to the 

 Laurentian. These rocks are surrounded by a series of altered black 



