NO. I FORMATIONS OF BEAVERFOOT-BRISCO-STANFORD RANGE 45 



(226.2 m.) thick at Sabine Mountain is 3,826 feet (1,166.2 m.) at 

 Sinclair Canyon and i,4?Q feet (451.1 m.) at Glacier Lake, 100 miles 

 (160.9 km.) north-northwest. 



The above examples serve to indicate the irregular areal deposition 

 of sediments in this section of the " Cordilleran Trough," and others 

 will be given in a future paper dealing with the pre-Devonian forma- 

 tions to the northwest of Bow River Valley. 



PRE-PLEISTOCENE FORMATIONS OF THE FLOOR OF THE 



COLUMBIA RIVER VALLEY ("ROCKY MOUNTAIN 



TRENCH") FROM CANAL FLATS TO GOLDEN 



From our present information it is probable that the Ozarkian Mons 

 formation is subjacent to the greater part of the present Pleistocene 

 deposits of the Valley, and that the pre-Pleistocene Valley from Canal 

 Flats to Golden and north was mainly eroded : 



(i) In folded, plicated and faulted Devonian and Silurian lime- 

 stones. 



(2) The subjacent Lower Ordovician grapolite shales of the Glen- 

 ogle and Sinclair formations. 



(3) The shales and interbedded limestones of the Ozarkian Mons 

 formation. 



Usually on the western side of the Valley the pre-Cambrian Beltian 

 strata are subjacent to the Pleistocene deposits, but in Spillimacheen 

 Mountain a block of Silurian limestone has been dropped by faulting 

 and left by subsequent erosion so that now it adjoins the Beltian on 

 the west and northwest of the north end of Spillimacheen Mountain 

 and stands out as a reminder that the Silurian sea extended over and 

 probably beyond the western limits of the location of the " Rocky 

 Mountain Trench." 



The Mons limestones and shales outcrop at intervals on the east 

 side of the valley from Sabine Alountain above Canal Flats at the 

 head of Columbia Lake on the south to and beyond Golden and 

 Kicking Horse Canyon, but they are only remnants that have been 

 left by pre-Pleistocene erosion abutting against the cliffs of massive 

 Silurian limestone or out-cropping from beneath them, as at Sabine 

 Mountain and the northern portion of the Beaverfoot Range ; some- 

 times conformably but more frequently upturned and displaced. 



On the west side of the valley, the lower Mons (Briscoia zone) 

 occurs where canyon of Canyon Creek 5 miles (8 km.) south of 

 Golden cuts through the plicated and folded shales and interbedded 

 limestones and these beds continue to the northwest to and beyond 

 Beavermouth and south probably to Spillimacheen Mountain. The 



