NO. 4 PRE-DEVONIAN SEDIMENTATION I7I 



deposited in the Trough as they, now occur, after being faulted, up- 

 turned, and undulated by compression, extends from the western side 

 of Whiterabbit Creek at 52° north latitude, west-southwest, over the 

 ridge east of Siffleur River (D on map) and along the north side of 

 Mt. Sedgwick, Mt. Murchison, Mt. Sarbach, and Mt. Forbes to Alons 

 Peak on the Continental Divide west of Glacier Lake (B on map), 

 a distance of about 35 miles (56.3 km.). It is quite probable that it 

 should be continued still farther to the west to the pre-Cambrian in 

 the area at the head of Bush River on the western side of the Con- 

 tinental Divide. Unfortunately we have no knowledge of the forma- 

 tions there ; they may be displaced by faults with possibly one or 

 more troughs indicated, as in the Bow-Kicking Horse section, where 

 the formations of the Goodsir and Beaverfoot Troughs occur between 

 the Continental Divide and the Proterozoic Beltian formations. 



Glacier Lake Trough was of long duration. It was in existence 

 in middle Lower Cambrian time, and continued to receive deposits 

 until the close of the Sarbach Ordovician (Canadian) formation, and 

 possibly in Silurian and Devonian time. 



The continuity of deposition seems to have been largely uninter- 

 rupted except in Middle Cambrian time, when the calcareous sedi- 

 ments that formed the Eldon limestone, 2,728 feet (831.5 m.) thick 

 in the Bow Trough, 40 miles (64.4 km.) to the south-southeast, were 

 not deposited ; at least they have not been observed at any of the 

 outcrops where the Arctomys and Stephen are in contact. There were 

 also some minor interruptions, and certainly one great one (Mons), 

 Dccasioned presumably by a diminution of the supply of sediment or 

 a temporary raising of the level of the bottom of the trough. 



The sediments deposited may be summarized as follows : 



Calcareous shales and limestones 6,668 feet (2,032.4 m. ) 



Arenaceous and siliceous sandstones and shales 2,911 feet (887.3 m) 



On the eastern side the northwesterly extensions of the Bow and 

 Sawback Troughs were in open communication with the sea of the 

 Glacier Lake Trough except during Middle Cambrian Eldon time, 

 with possibly a few minor interruptions. 



On the western side, the Beaverfoot Trough presumably had an 

 open seaway to the Glacier Lake Trough, for the faunas of the Upper 

 Cambrian Sabine formation and the large faunas of the Ozarkian 

 Mons formation are essentially of the same type in the Stanford 

 Range {N on map) and the Glacier Lake section (B on map). The 

 fauna of the Ordovician (Canadian) Sarbach formation is of the 



