62 



G. M. DAWSON — ROCKY MOUNTAIN REGION IN CANADA 



rocks principally comprised in this outer mountain system range from 

 the Carboniferous to the Cretaceous in age. 



Table of Geological Formations 



Attention may now be directed to the general table of geological for- 

 mations recognized in the region under review. This is arranged in two 

 main columns, representing what I conceive to be the two great geosyn- 

 clines of this part of the Cordillera. These are separated by what has 

 alread}'^ been referred to as an Archean axis. A further explanation of 

 these main structural features will be given subsequently, but it is first 

 proposed to define and briefly note the character of each of the geological 

 units, beginning with the oldest. 



Western Geosyncline 



Pliocene Horsefly Ki':>vels 



Ciuiirtz drift of Klondike, 

 etc. 



Laramide Geosyncline 



F(ft 



Miocene Upper volcanic group 3,100 



Tnmquille Iteds 1,000 



Lower volcanic group 5,300 



Oligocene Coldwater group (Siinilka- 5,000 



nieen beds, etc.). 



Pvoccne Puget group (on coast onlv 



3,000' +). 



Cretaceous Nanairno group •J,7(X) 



Queen Charlotte Island group 

 (in Queen Charlotte isl- 

 ands) 0,500 



Triassic Nicola group 13,.500 



Carhoniferous .... Cache Creek group (i, .")()() 



Devonian (?) 



Silurian (7) 



Ordoviciaii 



.. (?) 



Feet 



Upper Laramie 3,000 



Lower Laramie 2,500 



Montana ) „ ,,» 



Colorado / '*'^'*" 



Dakota.... 

 Kootauie. 



9,750 



( Red beds to south, marine to 



north) say 000 



Banff series 5,100 



Intermediate series 1,500 



Halysites beds 1,300 



HTraptolithic shales 1,500 



-' Castle Mountain gi 

 ( per part). 



group (up-^ 



^.^^ 



Cambrian -J 



r .Adams Lake series 25,000 P' 2 — Castle Mountain group i 



I ^ ? S' (lower part). J 



I 



I. Nisoonlith 15,000 



How River series. 



Archean. 



80,C,00 

 Shuswap series 5,000' + 



.000 



10,000 

 46,390 



Archean 



In 1881 it was possible only to allude to the existence of crystalline 

 rocks probably referable to the Archean. The rocks referred to were 

 those originally described by Dr Selwyn as the " Granite, gneiss, and 



