154 SMITHSONIAN MISCKLf.ANEOUS COLLFXTIONS VOL. 75 



cline. This was followed to the west by the ( ioodsir and finally the 

 Beaverfoot Trough. The Bow Trough had open connection with 

 the Glacier Lake Trough on the north {B, C, D on map and fig. 14) 

 and with troughs or broad seaways -to the south more or less inter- 

 mittently all through Paleozoic time. The Goodsir Trough, as we 

 now recognize it. did not have a direct connection with either the 

 Bow or Beaverfoot Troughs, and except during a relatively short 

 period in late Lower Carnbrian time there was no connection between 

 the areas of the Bow and Beaverfoot Troughs by which the fauna 

 in one could have access to the other. The Goodsir Trough had no 

 known connection with the Glacier Lake Trough and only very slight 

 and short connections in L^pper Cambrian time with the seaways to 

 the south. The Beaverfoot Trough was in open connection with the 

 Glacier Lake Trough on the north and at intervals with the seaways 

 to the south. Deposition in the Sawback Trough a])pears to have 

 been active at about the same time as in the Beaverfoot Trough, and 

 there was an open seaway connection on the north into the broad 

 Glacier Lake Trough that permitted the Sabine and ^lons faunas to 

 pass freely between the south end of the Beaverfoot Trough at Sabine 

 Mountain (O on map) to Ranger Canyon {H on map) in the Saw- 

 back Trough, a distance of approximately 225 miles ( 362.0 km. ) . 

 The probability is that the faunas mentioned passed from the Glacier 

 Lake Trough south into the Sawback Trough, but they may have 

 come in from the south through a seaway of which as yet we have 

 no information. There was nowhere a regular uninterrupted sequence 

 of deposits in any of these troughs from the beginning to the end of 

 Paleozoic time. This was prevented by diastrophic movements of 

 greater or less extent that occurred in the Cordilleran Geosyncline. 

 from its inception until the " high Ancestral Rocky Mountain gean- 

 ticline '' blotted out its eastern side and later its median portion.' 



Usually the boundaries of the troughs were low and afforded little 

 mechanical sediment for deposition and, as determined by the faunas 

 that lived in the seaways, we learn that they were not all of the same 

 age and that the diastrophic movements afifecting the geosyncline 

 were subject to long periods of quiescence, in which accumulation of 

 sediments may have caused deepening, and local tilting caused both 

 deepening and shallowing of the troughs. 



At present it is very difficult to form a clear conception of the 

 original condition of the troughs in pre-Devonian time. On the eastern 



^ Schuchert, loc. cit.. pp. 186, 187. 



