February io, 1916] 



NATURE 



661 



establishes, under C. W. Knight's name of "blair- 

 morite," a trachytic type consisting of analcite crystals 

 up to an inch in diameter, embedded in a green and 

 sometimes aphanitic matrix. Orthoclase (sanidine), 

 pyroxene, and melanite also occur. The analcite arose 

 at an early stage in the consolidation of the rock, and 

 may amount to 75 per cent, by volume. No. 15 is- 

 also a petrographic paper, on "The Gay Gulch and 

 Skookum Meteorites," by R. A. A. Johnston, describ- 

 ing and illustrating two specimens, probably from the 

 same fall, which contain about 80 per cent, of iron 

 and an unusual proportion of nickel, from 15 to 18 per 

 cent. 



In both Nos. 17 and 18, attention is* directed to the 

 relics of early Palaeozoic strata that occur within the 

 broad pre-Cambrian area of Ontario and Quebec. In 

 some cases (Bull. 18, p. 22) patches of Paleeozoic lime- 

 stone have been preserved by down-faulting, and 

 E. M. Kindle and L. D. Burling show that the sea in 

 which they were formed spread very widely over the 

 Laurentian upland south-east and east of Hudson 

 Bay. The scarp-like southern face of the Laurentian 

 plateau, which is so marked a feature of eastern 

 Canada, is attributed to post-Cambrian faulting. The 

 Palaeozoic rocks have been dropped about 1000 ft. over 

 a stretch of 300 miles, forming the lowland fringe 

 along which the Canadian Pacific Railway runs from 

 Ottawa to Quebec. No feature of such magnitude has 

 been traced in the topography of the old undulating 

 plateau on which the Cambrian strata were laid down. 

 In Bull. 17 M. Y. Williams describes an outlier of 

 Lower Ordovician dolomite, containing pebbles worn 

 from the Huronian, near Haileybury, on Lake Timis- 

 kaming. Patches of Niagara strata also occur farther 

 north, and the pre-Cambrian surface was evidently 

 " washed by both Trenton and Niagaran seas." 



In Memoir 39 of the Geological Survey of Canada 

 M. E. Wilson describes the " Kewagama Lake Map- 

 Area, Quebec," which lies north of Lake Timiskaming, 

 on the watershed between the Ottawa system and 

 Hudson Bay. Pillow-structure, the origin of which 

 is once more reviewed, occurs very commonly in the 

 Abitibi (Keewatin?) volcanic series. The name Laur- 

 entian is wisely rejected for the granite and gneiss of 

 the district, since they are intrusive in the Abitibi 

 rocks, though older than the Cobalt series. A great 

 Quaternary lake, named Lake Ojibway by A. P. Cole- 

 man (p. 104), occupied the region during the retreat 

 of the Labradorian ice-sheet, and laid down season- 

 ally stratified beds of clay and " calcium carbonate," 

 which are well illustrated on plate xxvi. The clay is 

 assigned to the summer, and the calcium carbonate 

 to the winter seasons. It would be interesting to have 

 an explanation of the deposit of the latter material. 

 From remarks on p. 105 we may be led to infer that 

 the spring, when water flowed abundantly from the 

 melting snows, was followed by a season of drought 

 and evaporation ; but was this dry season necessarily 

 postponed until the winter? 



Several memoirs have been recently issued dealing 

 with British Columbia. Their photographic illustra- 

 tions emphasise the frequency of great uplifted plains, 

 in which post-Glacial streams have cut deep V-shaped 

 notches. The Cretaceous sea, and the Eocene sea 

 which continued it in places, were driven out of the 

 region by an uplift accompanied by folding, after 

 which, probably during Miocene times, " a long period 

 of crustal stability ensued, during which what is now 

 the Yukon plateau, as well, possibly, as the coast 

 range and other adjoining tracts, were reduced to a 

 nearly featureless plain " (D. D. Cairnes, Mem. 37, 

 iqT3, p. 45). The same author (Mem. 67, 1914, on 

 "The Yukon-Alaska International Boundary, p. 27) 

 states that the elevation of this plain took place 

 " during late Miocene, Pliocene, or early Pleistocene 

 NO. 2415, VOL. 96] 



time." The steep excavations made in the peneplane 

 of the Keele Mountains, shown in plates iv. and v. of 

 this memoir, and the continuity ot much of the up- 

 j land, suggest a late date for the elevation. In opposi- 

 tion to the older views of R. A. Daly, C. W. Drysdale 

 I (Mem. 56, 1915, " Geology of Franklin Mining Camp," 

 t p. 44) recognises the peneplane well within the Cor- 

 dillera of British Columbia, and attributes its develop- 

 ment to the Pliocene rather than to earlier epochs of 

 i denudation. On the other hand, L. Reinecke (Museum 

 I Bull., No. II, 1915, p. 39) finds no evidence of the 

 I formation of peneplanes in the southern part of the 

 j interior plateaus of British Columbia since the Oligo- 

 , cene lavas were poured out. " Differences of elevation 

 I of 2000 ft. are of constant occurrence within 10 miles 

 I of each other"; the average slopes of the plateau-sur- 

 I faces measure between 160 and 300 ft. to the mile ; and 

 the author states that the country before its uplift 

 j reached a stage of late maturity rather than old 

 age. He sustains this position by a number of interest- 

 j ing sections. 



An important petrographic detail occurs in C. W. 

 Drysdale 's memoir on Franklin Camp (No. 56). In- 

 trusive alkalic rocks of Miocene age have penetrated 

 at the Kettle River a conglomerate that is either Eocene 

 or Oligocene. This was unconsolidated at the time of 

 the intrusion, and (p. 82) "the syenite has permeated 

 and saturated the conglomerate and fine grit for at 

 least 50 ft. from the main contact. . . . Pseudomorphs 

 i of syenite after the more permeable pebbles and matrix 

 I occur." Even quartzite pebbles show "the presence of 

 minute alkalic feldspars with characteristic trachytic 

 I structure." This replacement of the Kettle River 

 I pebbles has been tested by microscopic sections, and no 

 I original pebbles of alkalic rocks occur in the con- 

 I glomerate. The syenite has elsewhere given rise to 

 ( trachytic flows at the surface, and the trachyte, 

 where it overlies the Kettle River formation, has pene- 

 trated at least 5 ft. down into the grit. On plate xi. 

 a junction of trachyte and sediment is shown, where 

 contorted films of silt are seen included in the lava as 

 portions of a composite rock. 



R. A. Daly, in Memoir 68 (1915), describes "a geo- 

 logical reconnaissance between Golden and Kamloops, 

 B.C., along the Canadian Pacific Railway." He finds 

 that the oldest known rocks of British Columbia are 

 the Shuswap sediments, which were originally muds 

 and sands, with some gravels, washed from a lost 

 land-surface of quartzose, granitic, or gneissose char- 

 acter. The existing gneisses result from the intrusion 

 of granitoid magmas, also pre-Cambrian, into the 

 Shuswap series. The composite mass became uplifted 

 and denuded, and a geosynclinal was then developed 

 (p. 154) in the eastern belt of the present Cordilleran 

 region. In this hollow accumulations went on from 

 late pre-Cambrian (Beltian) to Lower Carboniferous 

 (Mississippian) times. The sea, however, did not 

 reach the western belt until the Upper Carboniferous 

 epoch. The Canadian Cordillera attained its full 

 length and breadth as a result of folding at the end 

 of the Cretaceous period. The author (p. 157) hesitates 

 to refer the final uplift to late Pliocene times, in face 

 of the deformation of the Lower Miocene and older 

 strata that took place before the Pliocene period 

 opened. One of his most important conclusions is the 

 continuity of deposition (p. 03) in the Beltian and 

 Cambrian sediments of the Selkirks. The schistose 

 nature of the Shuswap sediments leads the author 

 (p. 44) to a useful discussion of " statical meta- 

 morphism," as recognised by Judd. The sediments 

 I were affected by the superincumbent load before their 

 I further metamorphism by lit par lit injections of 

 granite. Dynamic metamorphism further modified 

 them, and the composite gneisses associated with them, 

 in post-Cambrian time (p. 50). The mountain-land- 



