NO. 4 PRE-DEVONIAN SEDIMENTATION 1 57 



side ' the faultinj:;- and eastward thrusting of the sedimentary forma- 

 tions has forced the rocks, representing deposits in originally distinct 

 troughs, eastward over each other until all evidences of land or shal- 

 low sea barriers between the troughs have been destroyed or deeply 

 buried. On the western side the strata of the Beaverfoot Trough have 

 been forced into overturned folds at the north end of the Beaverfoot 

 Range west of the Kootenay fault, also faulted and possibly folded 

 at the south in the Brisco and Stanford Range. The strata of the 

 Goodsir Trough were also deeply affected, as shown by Allan's fine 

 sections accompanying Map 142A of the Kootenay District.* These 

 movements were usually, if not always, accompanied by displacements 

 that are now recorded by profound faults and the juxtaposition of 

 unlike formations containing faunas that are not in their normal 

 stratigraphic order. The more or less irregular thrusting with con- 

 current and later erosion are accountable for the present position and 

 exposures of the buried sections of the original troughs and. the dis- 

 appearance of their intervening barriers. 



Examples of the overthrust of the sedimentary contents of a for- 

 mer trough are the thrust of the Cambrian and later limestones of 

 the Bow Trough of the Rocky Mountain Front over on the Cre- 

 taceous formations, and the thrust of the Ozarkian, Ordovician, and 

 Silurian rocks of the Beaverfoot Trough against, and probably on, 

 the Upper Cambrian rocks of the Goodsir Trough. The great Lewis 

 fault now marks the eastern limit of the Bow Trough, and the 

 Kootenay fault the eastern limit of the Beaverfoot Trough. 



A number of fine sections accompanying the report of Dr. D. B. 

 Dowling of the Geological Survey of Canada' illustrate the effect of 

 the eastward pressure that displaced and compressed the strata of 

 the Bow Trough and the superjacent Cretaceous and Jurassic strata. 

 A section a little south of Panther River is outlined by text figure 17. 



The section on the line of the Bow-Kicking Horse Rivers illustrates 

 the geological structure, as determined by McConnell and Allan, from 

 the Rocky Mountain Front to the Columbia River, a distance of yz 

 miles (115.8 km.). The broad features of this section are shown by 

 figure 18. 



A typical section displaying the overthrust of the strata of the Bow 

 Trough on the Devonian of the Sawback Trough is shown by figure 



^ See sections accompanying McConnell's Report D. Rept. Geol. Surv Canada, 

 Vol. II, for 1886 (1887). Also sections of Dowling on maps of Cascade Coal 

 Basin, Sheets i-io, Geol. Surv. Canada, No. 26b, 1907, No. 949. 



^ Geol. Surv. Canada, 1915. Accompanying memoir No. 55 by J. A. Allan 



' Cascade Coal Basin of Alberta, 1907. 



