272 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



part of the season of 1902 was spent in tEeir study bat the results were, in 

 many essential respects, very meagre. These rocks occur in one of the Cordil- 

 leran zones of maximum orogenic shearing and mashing, with complete 

 recrystallization. Numberless crumplings, overturnings and faultings 

 characterize the region, which, as already noted', has been the scene of repeated 

 igneous injections in the form of dikes., sills, stocks, and batholiths. Again and 

 again the region has been buried deeply in volcanic ejectamenta. In spite of 

 prolonged erosion these volcanics still cover hundreds of square miles and 

 conceal many desired facts concerning the sedimentary rocks. To such p fi- 

 <dpal difficulties in analyzing the complex assemblage of strata along the Pend 

 D'Oreille river there was added that common disadvantage of the geologist 

 on the Forty-ninth Parallel, the dense evergreen forest with its deep mat of 

 brush and fallen timber. (Plate 28.) 



At the time of the writer's exploration, the Commission trail on the south 

 side of the Pend D'Oreille river, had not been cult. The crossing of this 

 dangerous river above Waneta was effected only once; hence relatively little 

 is known of the rocks and structures on the left bank of. the river. In that 

 part of the belt, outcrops of rock are relatively few. Attention was therefore 

 concentrated on the strip of altered sediments lying between the river and the 

 Ptossland-Volcanic terrane to the north. 



The ancient Priest River rocks themselves are scarcely more baffling in 

 structural analysis than are these much younger schists along the Pend 

 D'Oreille. Their clean-cut mapping, their order of superposition and the 

 determination of thickness could not be thoroughly worked out. Nearly all 

 that is possible, as a result of the reconnaissance in 1902, is to give a general 

 qualitative description of the metamorphosed sediments. They are conveniently 

 referred to in the present report, under the name, Pend D'Oreille Group; 

 the wild canyon of the Pend D'Oreille river in the lower twenty miles of its 

 course has been excavated in the rocks of this group. Their distribution in the 

 Boundary belt is shown on the map though not with entire accuracy, 

 for it is extremely difficult if not impossible with existing exposures, to separate, 

 in several areas, the rocks of the group from the younger members of the 

 Summit series or from the old, schistose phases of the Rossland volcanics. 



The group may be divided into two parts, the Pend D'Oreille 

 schists (including greenstone and amphibolite, as well as phyllite and 

 quartzite), and the Pend D'Oreille marbles. The>y are primarily not strati- 

 graphic subdivisions so much as purely lithological ones. It wa<= ' '^nd imprac- 

 ticable to use the limestones as definite horizon-markers and eqi ally impossible 

 to be sure of the relative ages of the limestones and their non-calcareous 

 associates. Several of the larger bodies of limestone seem to form gigantic, 

 isolated pods which have been squeezed, like a truly plastic substance, through 

 the schists, to accumulate locally and with exaggerated thickness in these great 

 masses. On this view the limestone pods are, in part, exotic — they might be 

 called non-igneous intrusives — with reference to the enclosing schists. In 

 .any case, it has appeared unsafe to use the few legible records of original 



