224 G. M. Daicson — Geology of British Columbia. 



important groups of rocks, which constitute tlie mass of the forma- 

 tions of the Province. Still older rocks, which may indeed represent 

 part of the Archeean of the 40th parallel area, are known to occur, 

 but about them little has yet been certainly determined. They 

 appear at intervals in the Gold Eange, and in the region between it 

 and the Rocky Mountains. The rocks appear to be gneisses and 

 granites, holding orthoclase felspar, and with abundant quartz and 

 mica, very often garnetiferous and coarsely crystalline. They were 

 originally classed with the schistose gold-bearing rocks of Cariboo 

 and their representatives elsewhere, but we have already found 

 reason to believe that these schists are much newer, and during the 

 past summer those on the Misinchinka have been found to be charged 

 w^ith half-rounded quartz and felspar from the old rocks above 

 mentioned, which must have been fully metamorphosed at the time 

 of their deposition. A small area of these oldest and possibly 

 Laurentian rocks occurs near Carp Lake in the northern part of the 

 Province. They also exist in the Cariboo district, though they have 

 not yet been defined there. They are described by Mr. Selwyn as 

 occurring on the upper part of the North Thompson, and the gneissic 

 rocks noted by Dr. Hector near the sources of the Athabasca, on the 

 western side of the Eocky Mountain axis, probably belong to the 

 same fundamental series. 



Physical Conditions implied by the Deposits. — This review of the 

 state of knowledge of the rock series of British Columbia may well 

 be concluded by glancing rapidly at the physical conditions implied 

 in the production of the different formations. The oldest land 

 surface of which we have any knowledge is that of the probably 

 Archasan rocks just described, and must have been in the region of 

 the Gold Eange of to-day. It may have extended farther westward 

 in early Palaeozoic time, forming a continental area like that 

 supposed by King to have stretched west from the Wahsatch 

 Mountains on the 40th parallel, but no trace of its existence to the 

 eastward of the western margin of the Eocky Mountain Eange has 

 yet been found. In Devonian and Carboniferous times the geography 

 of the region begins to outline itself more definitely. The probably 

 Archgean rocks at this time formed a more or less continuous barrier 

 of land along the line of the Gold Eange, between the interior con- 

 tinental basin to the north-east and the Carboniferous Pacific to the 

 south-west. In the eastern sea organic limestones with sandy and 

 shaly beds were being deposited, and in the vicinity of the 49th 

 parallel at least one well-marked flow of igneous material evidences 

 the existence of volcanic phenomena. In the west and south-west of 

 the land barrier the conditions were widely different. Here, too, 

 limestones were in process of formation, but extensive siliceous 

 deposits were also forming, while a great chain of volcanic vents — 

 submarine or partly subaerial — nearly coincident with the present 

 position of the Coast Eange and those of Vancouver and the Queen 

 Charlotte Islands. Trap and agglomerate rocks were thus added to the 

 series. Similar centres of volcanic activity may have existed in the 

 vicinity of the land barrier on the west, whilst the finer felspathic 



