Gregory — Volcanic Rocks from Temiscouata Lake. 15 



its somewhat araygdaloidal aspect."* During the summer of 

 1897, the region was studied by Prof. H. S. Williams, and the 

 specimens then collected were turned over to the writer for 

 examination. The outcrops visited extend along the lake for 

 a distance of "20 miles, as shown on the accompanying map. 



Mount Wissick.— The rocks examined from Mt. Wissick 

 and the east shore of the lake are fossiliferous limestones, 

 sandstones and shales, without admixture of volcanic materials. 

 The shales and sandstones do not differ from similar rocks 

 found elsewhere. The arenaceous limestone in places is sep- 

 arated into hexagonal prisms, probably from shrinkage, and 

 appears as if composed of vertical columns with quite regular 

 outline. The thin layers of limestone in the slates at the 

 north of Mt. Wissick show under the microscope well-defined 

 oolitic structure in which the little spheres are broken by 

 numerous minute faults. 



West Shore. — The section on the West Shore extends from 

 Burnt Point, below Fort Ingalls, to the outlet of the lake. 



At Burnt Point the rocks are coarse conglomerates made up 

 of materials not much water worn, and show evidence of rapid 

 deposition. Slates and limestones form the most abundant 

 pebbles, and occasionally attain a diameter of 1-2 feet. The 

 total thickness of the conglomerate at this point is about 1000', 

 but such great thickness of the beds is reported to be quite 

 local. Succeeding the Burnt Point conglomerate, to the south, 

 occur thin-bedded shales and sandstones, which contain fossils 

 of Niagara age.f 



At Point aux Trembles, the rocks, both along the railroad 

 and on the lake shore, appear at first sight to be greenish sand- 

 stones and coarse brown conglomerates. They are interstrati- 

 fied with the other beds of the region, and have practically 

 the same dip and strike. A closer examination, however, 

 shows them to be volcanic. The finer, more sandy beds, con- 

 tain quantities of volcanic ash, and the coarser ones are con- 

 glomerates of typical andesitic fragments, with scarcely any, 

 foreign material. Parts of the rock contain very prominent 

 rounded fragments of amygdaloidal andesite. As with the 

 volcanics of northern Maine,;}: so here the gradation from the 

 sandstones of the region to pure volcanic material can be 

 traced, and like the Maine breccias and tuffs, these rocks show 

 more or less rounding of their pebbles and sorting by water. 

 It is believed that the volcanic vents were near some body of 

 water, and that the material fell in or near the water and 

 received a limited amount of wearing before final consoli- 

 dation. 



*G-eol. Survey of Canada — Annual Report, 1887, p. 33m. 



\ G-eol. Survey Canada, Annual Report, 1887, p. 33m. 



J U.S. a. S. Bulletin 165. 



