40 THE ROYAL SOCIETY OF CANADA 



ation, since the Ludlow changes from a series comparable to the Fort 

 Union in the southwestern part of South Dakota to a darker series 

 on the Little Missouri in western North Dakota, and to brackish and 

 marine at Bismarck without lignite seams. To the northwest, dark 

 beds are found beneath the Fort Union, south of Wood Mountain, 

 Longitude 106° 30', and a single brackish water shell is recorded 

 in the lower part of the Estevan exposures near the boundary line at 

 Longitude 103° ^ showing the extreme upper limit of possible salt 

 water. These changes in character are indicative of the subsidence 

 of a small area during the general uplift, and it would seem that there 

 is some evidence of the presence, on the northeast side of this area, of 

 beds derived from an eastern land area. The continuity of the upper 

 coal seams, and the doubtful continuation of the lower coal seams of 

 Turtle Mountain to the west all seem to point to the probable con- 

 tinuation of the Ludlow beds around the north end of the depression 

 in which was deposited the Cannonball marine beds of Dakota. 



The boring at Mandan is estimated to have penetrated to near 

 the Dakota, and at 470 feet to have passed through the Fox Hills. 

 The total depth attained was 2,000 feet. Comparing this boring 

 with the Deloraine well the Boissevain sandstone could be compared 

 with the Fox Hill by assuming that the Mandan well reached to within 

 about 200 feet of the Dakota sandstone. The rocks above the Bois- 

 sevain sand consisting of about 500 feet of beds contain numerous 

 coal seams so that the presence of the Cannonball marine formation 

 in this series seems, therefore, extremely unlikely as the coal seams 

 found at Redvers and Wauchope point to the probable presence of the 

 Ludlow lignitic member, which is in places decidedly Tertiary in aspect. 



An assumption, that any of these beds may belong to the period 

 of uprise in which the Belly River and Judith river deposits were 

 found, can with little doubt be negatived. The former series has 

 been traced eastward into Saskatchewan, and exposures are to be 

 found in the valley of South Saskatchewan river. It is there losing 

 any character pointing to fresh-water conditions, and is mainly 

 brackish. The fresh-water deposits are reported as continuing to the 

 north. In the Moosejaw well to the south of this valley certain beds 

 in the Pierre are found to be somewhat sandy in character, but they 

 would appear to be of marine origin. The base of this series in the 

 Moosejaw well appears to be about 1,340 feet below the Fort Union 

 of the Dirt Hills to the south. From the base of the exposed Belly 

 River in the Saskatchewan valley to the base of the Tertiary in 

 Cypress Hills is about 1,500 feet. These comparisons are across 



1 Annual Report, Vol. XV, p. 44F. 



