



B. N. A. BOUNDARY COMMISSION. 

ninth parallel have been referred to these periods. They enti, 
have been removed by denudation, along the eastern margin of wees 
previous to the Cretaceous period, or may never have been der 
there; as an elevation of the oceanic plateau to a sufficient height to al 
the formation of coarse sedimentary beds on its western margin, wou ‘i 
probably lay the eastern bordering region dry for a great breadth, = 
29. The Jurassic period, also, has left few records in the rocks of the — 
- North-west. It is hardly probable that strata of this age come to the ar 
surface in any part of the great interior continental valley north of the y 
aN 4 Line, though Richardson, when with Sir J. Franklin in 1826, obtained — * 
PF some fossils which Mr. Sowerby referred to the “ Oxford Oolite and i 
Cornbrash.”* As they came from the limestone beds of the Mackenzie, — 
oe : however, and if placed in the Jurassic series, would appear necessarily to. 
ee carry with them the bituminous shales now conclusively proved to he me 
am Devonian, there is no doubt some error in the reference. Prof. Meek : - 
ae writes, apparently with regard to the same fossils ; ‘from one of these 
beds Sir John Franklin collected in 1825 some fossils referred to Spirifer 
} acutus, and several Terebratale, resembling TJ. resupinata,’—“ Spirifer 
acutus, however, being a Carboniferous species, and Terebratula resupinata 
a Liassic form, it is evident there is some error in these identifications.”> _ 
Rocks known to be Jurassic by their fossils, are however, found in the _ 
Rocky Mountain region of Montana, and their equivalents—though not _ 
yielding fossils—appear among the highest rocks seen in the vicinity — 
of the South Kootanie Pass, and will probably be found above the carbon- 
iferous limestone much further north in the range. inhthe: 
30. The Cretaceous rocks, corresponding in age with the great chalk — 
formations of Europe, though very different from them in mineral 
character ; are those which spread over by far the greatest surface. 
Except in a few localities, and those chiefly in proximity to the Rocky _ 4 
Mountain region of uplift, they are still almost as perfectly horizontalas 
when originally deposited. The eastern edge of this formation partly i 4 
overlaps the underlying Silurian and Devonian beds, and runs nearly 
parallel with the base of the Laurentian range at a distance of about one — 
hundred and thirty miles, from the fifty-third to the fiftieth parallel of 
latitude. Southward it trends to the east, and probably crosses the forty- = 
ninth parallel east of Red River; while in south-western Minnesota ~ ae 
Cretaceous rocks repose directly in some places on granites, which are no — ‘ oe 







































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ly 
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4 
* Journal of a Boat Voyage, vol. I, p. 177. t Trans. Chieago Acad. Sci., vol. I, p. 66, 

