60 b 



GEOLOGICAL SURVEY OF CANADA. 



Outlying 

 islands. 



Coarse agglo- 

 merate. 



Dolerite. 



Bitumen. 



Rocks of Sel- 

 wyE Inlet. 



west end of Logan Inlet, are found on the western ends of the three 

 first-mentioned islands. On the shore of Murchison Island these are 

 intimately associated with hardened blackish argillites, the section 

 being, however, hopelessly confused by the presence of a number of 

 fine grained pale felspathic and porphyritic dykes. The mass of the 

 argillites probably runs down the north-east side of Juan Perez Inlet, 

 but beneath the water. About the middle of the north-west side of 

 Ramsay Island, rocks differing somewhat from those generally found 

 in the series appear. They form the entire north-eastern part of the 

 island, the eastern part of Murchison Island, and probably the whole 

 of the Tar Islands. These rocks are somewhat more basic, and though 

 tilted in some places at high angles, of less altered appearance than 

 those of Logan Inlet. They include a great thickness of rough agglo- 

 merate which has evidently been formed in the immediate vicinity of 

 volcanic vents, as some of the included masses are over four feet in 

 diameter. These frequently project on surfaces exposed along the 

 shores by reason of the comparatively soft character of the matrix. 

 The matrix and its included fragments are apparently similar in 

 character. A microscopic section of one of the latter proved it to be 

 a dolerite which with a dark finely granular ground-mass is rendered 

 porphyritic by felspar and pyroxene crystals, which are frequently 

 more or less perfectly stellar aggregations. The rock has not suffered 

 much change, the minerals being clear and sharp. 



A bed apparently of porphyritic dolerite forming a small island off 

 the east shore of Ramsay island is nearly vertical and has a rude 

 columnar structure. The Tar Islands appear to mark the outcrop of 

 the most massive agglomerate bed. It is reported that on one of them 

 bitumen oozes out in small quantities among pebbles on the beach. 

 Agglomerates of a similar character are found on the east side of the 

 entrance to A-tli Inlet, on the north shore of Lyell Island. 



At the north entrance of the narrow passage inside Tal-un-kwan 

 Island detached masses of agglomerate and conglomerate are abundant, 

 and though the rocks were not seen in place, they probably represent 

 the northern continuation of the conglomerate described as lying at 

 the base of the upper igneous series on Logan Inlet. The promontory 

 south of Rock-fish Harbour is composed of much hardened and well 

 bedded felspathic rocks, occasionally agglomerates, nearly vertical, and 

 with a general east and west strike. Similar rocks appear to charac- 

 terize both shores of Selwyn Inlet up to the long western arm, where 

 the trough formed by these newer volcanic rocks runs inland to the 

 westward. The northern shore of this arm is composed, however, of 

 argillites, with some conglomerate, the latter probably representing 

 the horizon already several times referred to, and indicating that this 



