May II, 1911] 



NATURE 



61 



GEOLOGICAL WORK IN BRITISH LANDS.' 



« III. — In Canada. 



'P HE Geological Survey Branch of the Canadian Depart- 

 ment of Mines has a large amount of pioneer work 

 before it. In a publication numbered 1097, issued in 1910, 

 Mr. J. Keele describes his reconnaissance across the 

 Mackenzie Mountains in Yukon and North-West Terri- 

 tories, involving much personal risk and often dependence 

 on hunting for a supply of food. The country that he 



Fic. 1.— Mount Sheldon, Mackenzie Mts., a granite mass intruded into Pateozoic sediment;, 



explored along its rivers lies betwet-n the Mackenzie Moun- 

 tains, a part of the Rocky Mountain axis, and the St. Elias 

 Range. The valley bottoms are practically free from frost 

 during June, July, and August ; but the temperature varies 

 from well below zero in January to 00° F. during llie 

 almost continuous daylight of June. Cambrian, Silurian, 

 Devonian, Triassic, and Cretaceous strata have l)iin ri rog- 

 nised, and Mr. R. G. McConnell has described a ba-in of 

 Cainozoic rocks, including basalt. Granite, iniriKicd in 

 local " stocks or [)il!ars " (p. 41) into old sfdiments, is 

 responsible for Slount Sheldon and 

 other upstanding peaks of the Mack- 

 enzie Mountains (Fig. i). The map 

 accompanying the memoir, like the 

 illustrations, is a fresh contribution to 

 geographv. 



Mr. \V. M.Inne's rr|,>,r^. (NO. 1008) 

 on a part of the North-West '!< rritories 



unexplored area of 15,000 square miles in extent, to the 

 west of that examined by Mr. Mclnnes. The rocks consist 

 of amphibolites and mica-schists, penetrated by granitoid 

 gneisses on the south, the latter containing inclusions of 

 amphibolites. Here, as so often happens, the schistose 

 rocks, with their metamorphosed basic associates of igneous 

 origin, are the oldest recognised in the district. 



Mr. W. H. Collins's account (No. 1059) of the geology 

 between Lake Nipigon and Clay Lake, Ontario, is remark- 

 able for its clear acceptance (p. 52, &c.) of the intrusive 

 relation, over wide areas, of the Laur- 

 entian to the Keewatin and Huronian 

 series. Inclusions of the latter in the 

 gneisses, far away from any junction of 

 the two typ>es of material, are used as 

 an argument for the former extension 

 of a schistose mantle over the whole 

 area. It may be confidently stated that 

 in our islands such inclusions wotild be 

 often treated under the mysterious title 

 of " basic segregations." 



The Survey now {1910) issues a 



definite series of publications styled 



Memoirs, No. i being by Mr. A. Wilson 



on the grology of the Nipigon Basin. 



In Lake Nipigon we are glad to note 



the occiirr''nei' of Mm-chiston, Geikie. 



and Kelvin Inlands, all constructed of 



firm crystalline rock. These are parts 



of the great and almost horizontal 



sheets of diabase which cover a wide 



an a, and which remind one of similar 



oeeurrcnces in the Karroo systems of 



South Africa. After a full discussion. 



the author concludes that the capping 



diabase' in his area represents a lava 



that flowed over a land-surfaci' cf great exirni, to wluch it 



is unconformable, and from which, at certain point-;, it ha< 



gathered boulders (p. 94). The sedimentary -.1 r^ < of 



shales, sandstones, and dolomites, in which ihi' i;^rM ous 



sheets are intercalated, are at present classed as 



Keeweenawan, but Mr. Wilson thinks (p. 71) that they 



may be younger than even the Potsdam siries farther 



east. The gneis-r. iliat occur below tln' llur(>nian series 



include basic types that " probably represent highly iiieta- 



1 portions of the cover, or rather are new roek- 



niorplK 



drained by the Winisk and 

 piskat Rivers, with a large m, 



■!•■ of OIL- inrh to ei^lli 



At 



iwa- 



the 



a versed. Topographical 

 lade (luting journeys by 



^ion, hin;' imrlli III 



.rder, lia 

 lia'an |)la 



siir\ ' 

 caim 



tie- 



i willi hould' 

 streams now cut r 

 cliffs. Post-glacial 

 Pccicn islaml''"^ 

 Mytiltis edti 

 molluscs of 



Olltalii. 

 r.IIef; (lie 

 -aio,,lhe,l l.v 

 h ol the lowland i-- 

 r-ela\-, in which the 

 iaraele|-i,i i(^ yert ieal 

 inariiie elavs, with 



a/,/ 



pi 



Li 



sli 



he-i. w, 



outlook 



Memoir 

 marine 

 bonn 



de- 



Willi- 

 innr>w 



|>: > ,mii.i 

 m litid- 



and will h 



A Ih. 



M-\, 



.lue.i ,,11 \' 



11|> w 



llli thai 



Wini-k 



■ ,^ , and a 



j 11, MIS 11: pai 1 were (l,-i 1\, ,1 tioiii 111- eov-r. 



I;i,;m !'"■ :'i-aiiite m.-igiiia" ip. 571. Mail} 



■eli; lia\e !„ ,11 attributed to 



, s inid' r tie diabase sheets, 



,i,,,. ,1, in tlii'- an .1 .is coinparatively 



:ii a moiilirm;; iioinl of vie\\\ 



uiiiiii ; 



:\I, . •,■,, ill Me;, loir 5, writ 



ti-ict ol liie i.-we-. .lie! N,.i d-ii-l;:.'!'! 



vll I 



ISO. J id; 



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