40 THE ROYAL SOCIETY OF CANADA 



of this period remain from which to infer the original extent. Marine 

 fossils occur in the Bearpaw in the section on Oldman river, but on 

 Highwood river the formation is mostly of dark sandy shales with 

 considerable carbonaceous filaments between the beds and having 

 a coal seam at the base. This possibly indicates an approach here to 

 shallow water and an eastward bend in the shore-line. Whether the 

 area so affected formed a large delta of which this is the southern part 

 is problematical ; but it may be remarked that in the North Saskat- 

 chewan section these shales are not definitely recognized below the 

 Edmonton outcrops, while the same can be said of the exposures on 

 the upper Athabaska. The reference to these beds in the discussion 

 of the Smoky River shales was in connexion with the finding of Ino- 

 ceramus altus at the summit of Table mountain and was merely an 

 intimation that salt water deposition occurred in that locality after 

 the deposition of the Wapiti sandstones. The northern extension 

 of the Pierre sea is not known. Exposures in the MacKenzie valley 

 and elsewhere in the north show marine beds similar in fossil content 

 and appearance to the Benton shales, but above these, sandstone beds 

 of Tertiary age. There is, therefore, a probability that the Pierre sea 

 advanced from the south and did not cover the northern portion of 

 the continent. The beds at the summit of Table mountain on Pine 

 river may indicate possibly the extreme northwestern limit of this 

 advance. 



In the foothills north of the Bow river it is not definitely known 

 that marine deposits of the upper Pierre are to be found. This may 

 indicate land areas there during this last westward swing of the sea 

 coast. The deposits in these localities being of continental formation 

 may show by unconformities the land surfaces of this period or land 

 areas in proximity to sea-level may be marked by a carbonaceous 

 zone indicating the former rich vegetation. The division between 

 the continental formations of the Belly River group and those of the 

 succeeding Edmonton may be difficult to define in the foothills beyond 

 the western limit of the Upper Pierre sea. 



UPPER PIERRE SHORE DEPOSITS (PLATE VIIl). 



In all the sections across the beds remaining above the marine 

 shales of the Cretaceous and now filling the Alberta syncline it is 

 pointed out that a mingling of brackish and freshwater deposits forms 

 the lower members. These must naturally extend westward only 

 as far as the previous marine advance and were laid down on an ex- 

 tremely level plain in shallow water or marsh. From the extent and 

 thickness of these measures the width of this marshy tract was at all 



