[dowling] cretaceous SEA IN ALBERTA 33 



On the assumption that the advance of the sea was rapid the shore 

 deposits are to be considered as belonging, in age at least, to the shales 

 which they appear to overlap rather than to any part of the shales 

 which cover them. 



Going back to the question involving the age of the Edmonton, 

 if the brackish water beds shown in the upper part of the first diagram are 

 considered, their position conforms in the western part to that of the 

 Edmonton, the upper shale to the Bearpaw and the upper measures 

 at the eastern end to the Fox Hills sandstone. In each case the marine 

 sands representing the foreshore deposits vary in age of deposition 

 from the advance to the completion of the retirement of the sea. 

 At the eastern end the upper member only corresponds to the typical 

 Fox Hills formation in age. In the western section marine sands 

 with a Fox Hills fauna are found at several horizons, generally at the 

 base of the shore formations. Thus we have Fox Hills at the base of 

 the Lower Pierre, probably also at the base of the Upper Pierre, and 

 also beneath the Edmonton. The use of the term Fox Hills in the 

 nomenclature of any western marine sands would be doubtful, if 

 not improper, except in a descriptive sense. The correlation of the 

 western brackish water beds such as the Edmonton formation with 

 any but the marine part of the eastern section cannot, therefore, be 

 made without grave danger of error on account of the marine character 

 of some of the upper members of the Edmonton. The evidence of ver- 

 tebrate remains places the Edmonton well below the Lance and, there- 

 fore, it was formed at least as early as the close of the Pierre. 



The inclusion of the Edmonton in the Montana is assumed and 

 with it a probable series of freshwater beds to the west of the brackish- 

 water deposits which must have been formed at the same time beyond 

 the limits of the sea. 



The division of the Montana group into Pierre and Fox Hills 

 is applicable only to the eastern sections. The marine shales in Alberta 

 containing a Pierre fauna are found in two distinct beds or formations 

 separated in nearly all cases by shore deposits. The names in use at 

 the present time for these portions of the Pierre are Bearpaw for the 

 upper and Claggett for the lower. As the shore deposits, especially 

 during the retreating stage of each of the seas here indicated, form a 

 varying proportion of the deposits of each stage, the far western 

 marine beds may be assumed to represent but a portion of the deposi- 

 tion. Similarly to the east of any trace of shore formed beds, the shales 

 present represent a longer time interval than the sum of the Claggett 

 and Bearpaw shales, as represented in Alberta, although the thickness 

 of the deposits may be less. The divisions adopted here are, therefore : 



Sec. IV, 1915—3 



