[schofield] rocky MOUNTAIN TRENCH 83 



It is rather unfortunate that the age of the Kishinena formation 

 cannot be dated more closely. Mackenzie gives the following infor- 

 mation : "Fossils collected by the writer have been determined by Dr. 

 W. H. Dall, who reports finding 'Two species of Planorhis, crushed 

 flat .... and the remains of a species of Physa. The shells are 

 specifically indeterminable owing to their bad state of preservation, 

 but the larger one recalls Planorbis utahensis White, and the smaller 

 multispiral one Plajiorhis cirratus White, the former from the Bridger 

 group, and the latter from the Green River beds of Wyoming. Only 

 a guess is permissible, yet a probability of Eocene age is existent so 

 far as I dare express an opinion.' " 



Fossils collected by Daly^ were examined by Dr. T. W. Stanton, 

 who reported the collection to "consist entirely of freshwater shells 

 belonging to the genera Sphaerium, Valvata ( ?) Physa, Planorbis, 

 and Limnaea. Similar forms occur as early as Fort Union, now 

 regarded as earliest Eocene, but there is nothing in the fossils them- 

 selves to prevent their reference to a much later horizon in the Tertiary, 

 because they all belong to modern types that have persisted to the 

 present day, though it should be stated that their nearest known 

 relatives among the western fossil species are in the Eocene." From 

 the above statements concerning the fossil evidence, the age of the 

 Kishinena formation can only be stated as probably Eocene. Hence 

 the normal faulting in the Flathead valley is probably Eocene in age, 

 and since it is very probable that the normal faulting which succeeded 

 the period of compression in the Rocky Mountains is of one general 

 age, the faulting along the line of the Rocky Mountain trench is also of 

 probable early Eocene age. 



FiNLAY River Section 



"The Finlay River section is much inferior to that afforded by 

 the Omineca, as the direction of the river for long distances is parallel 

 or nearly so to the strike of the rocks. No exposures occur along the 

 lower part of the river. From its mouth up to the Omineca, the Finlay 

 winds through a low alluvial plain without touching the bordering 

 highlands or mountains. Above the mouth of the Omineca the 

 banks increase in height, and where cut into by the stream, show 

 glacial sands, gravels and clays, holding numerous scratched and 

 polished boulders. 



"A mile and a half below Fort Grahame, an exposure of hard 

 grayish contorted limestone appears on the west bank of the river, 

 underlying mica-schists and gneisses. The limestone strikes N.40°W., 

 and dips to the west at an angle of 70° or over. 

 1 Geol. Surv., Can., Mem. 38, 1912, p. 87. 



