608 



SCIENCE 



[N. S. Vol. XLIII. No. U13 



Another important contribution to Cordil- 

 leran stratigraphy is that of Dr. S. J. Scho- 

 field.^ Intensive studies of a large portion of 

 the Pureell range south of the Canadian Pa- 

 cific railway have been carried on for a period 

 of five years. The area mapped includes 

 about 2,500 square miles immediately north of 

 the International Boundary, but the problems 

 encountered involved reconnaissance work ex- 

 tending over much greater areas. The region 

 includes a part of the section traversed by Dr. 

 Daly in 1901 to 1906 and discussed by him in 

 his report upon the geology of the Forty- 

 ninth Parallel.^ The detailed examinations of 

 the more recent survey make necessary a num- 

 ber of changes in the somewhat tentative cor- 

 relations and structure determinations of the 

 earlier reconnaissance work. 



The bed-rock of the Cranbrook area may be 

 referred to two systems. By far the greater 

 part belongs to the Belt terrane which is un- 

 conformably overlain by remnants of Devono- 

 Carboniferous limestones. Neither the base 

 nor the summit of the Beltian system, as de- 

 termined in the Eocky Mountains, is exposed 

 in the Pureell range. The Pureell series is 

 composed of 22,500 feet of sediments, largely 

 clastic, which by their numerous horizons of 

 mud cracks, ripple marks, easts of salt crys- 

 tals, and red beds suggest a continental rather 

 than marine origin for most of the strata. 

 Near the top of the series are recurrent basaltic 

 flows whose extrusion was accompanied by the 

 intrusion of gabbro sills. Probably the most 

 significant "departure from Dr. Daly's conclu- 

 sions is that relative to the age of the upper- 

 most of the Pureell formations. In the Forty- 

 ninth Parallel report nearly 11,000 feet of 

 strata were regarded as of Lower and Middle 

 Cambrian age. The later survey has resulted 

 in determining that the entire series is of pre- 

 Cambrian age and that the uppermost beds 

 were deposited some time before the close of 

 Proterozoic times. 



Throughout the entire Paleozoic and Meso- 



2 ' ' Geology of Cranbrook Map-Area, British Co- 

 lumbia," S. J. Schofield, Geological Survey, Can- 

 ada, Memoir 76, 1915. 



3 Geological Survey, Canada, Memoir 38, 1913. 



zoic eras, with the exception of the interval 

 during which marine limestones of Devonian 

 and Mississippian age were deposited, the 

 region seems to have been subject to erosion. 

 Orogenie movements, possibly at the close of 

 the Jurassic period, formed a great series of 

 anticlines and synclines and were followed or 

 accompanied by intrusions of granite bosses 

 and batholiths. Subsequently erosion reduced 

 the area to an old-age topography, which was 

 later uplifted and is now represented by the 

 summit levels of the mountain range. Here, 

 again, Dr. Schofield differs from Dr. Daly, who 

 attempted to explain the present topography 

 in terms of one-cycle erosion. From the excel- 

 lent illustrations accompanying the report, as 

 well as from the facts cited, the reviewer would 

 agree with the author of the recent memoir. 

 However, the reference of the peneplain to the 

 Cretaceous period does not seem to be justified 

 by the meager data available. The present 

 topography may well have been developed by 

 the dissection of the graded surface since late 

 Tertiary times. A study of the relations of the 

 summit peneplains of the adjacent ranges to 

 the mid-Tertiary lavas of the Interior Pla- 

 teaus should yield evidence enabling the deter- 

 mination of the dates of rejuvenation. 



Quaternary deposits include fossiliferous 

 sands and gravels overlain by glacial drift. 

 The former are presumably of interglacial age 

 and indicate a climate as warm as that of the 

 southern United States at the present time. 

 These are found in the Eocky Mountain 

 Trench, a topographic feature extending from 

 the International Boundary northward into 

 Alaska, which is believed to be the result of 

 erosion controlled by fault planes. 



Paleozoic Strata of Central Canada 

 The " Hudson Bay Exploring Expedition " 

 of 1912, under the leadership of J. B. Tyrrell, 

 secured collections of fossils from the little- 

 known region which forms the southerni shore of 

 Hudson bay. The collections include a large 

 number of fossils from the Silurian outcrops 

 along the Severn and Fawn rivers as well as 

 certain Ordovician species from the region 

 southeast of Port Nelson in northern Mani- 

 toba. These have been described recently by 



