Section IV, 1920 [35] Trans. R.S.C. 



The Turtle Mountain Coal Measures 

 By D. B. DowLiNG, B.Sc, F.R.S.C. 



(Read May Meeting, 1920) 



The deposits which were formed during the later phases of the 

 retreat of the Cretaceous sea from the central part of the North 

 American continent, are of special interest in that by their variation 

 between brackish, fresh and salt water conditions of deposition, they 

 denote a long period of oscillation for the shore line, or of variation in 

 the depth of the sea. In the western States the direction of retreat 

 appears to have been mainly to the eastward. In Canada the latest 

 marine deposit of any considerable extent reaches a former shore line 

 within the border of the plains and it is supposed did not extend 

 beyond the limits of Alberta, so that the withdrawal of the sea is 

 considered as having been toward the southeast. 



The non advance of the later Cretaceous sea beyond the confines 

 of Alberta would naturally suggest a greater elevation of the crust to 

 the north, or if this elevation was relatively small, there would be 

 provided a large area with extremely shallow water in the northern 

 extension. This condition would give rise to the formation of lagoons 

 and the growth of moisture loving plants. 



The Edmonton formation, which is a brackish water formation 

 and contains coal seams, reflects the kind of deposit which would be 

 expected over this flat plain within reach of the sea. These deposits 

 extend apparently toward the northeast, but are eroded from the 

 surface east of Edmonton. Deposits of a period of shallowing, which 

 preceded the Edmonton period of deposition are found projected 

 partly across Saskatchewan, and as these originated from the action 

 of similar forces, it may be assumed that the direction of retreat 

 indicated in the deposits of the Belly River Series, and also in the 

 sandy beds of the overlying marine shales, may be considered as 

 resumed in the later uplift. In this way the final contraction of the 

 marine area appears to have been toward the southeast. In North 

 Dakota the latest marine deposits that are not eroded are to be found 

 near Bismarck near the centre of the state, and are cited as evidence 

 of a direction of retreat toward the northeast or east. If the passage 

 beds that lie to the west of this area could be considered as being of 

 the same age as the Edmonton, the withdrawal of the sea could be 

 considered as the formation of an inlet to Hudson's Bay. As the 

 faunal evidence of the Edmonton formation and of the Lance forma- 



