[dowling] 



CRETACEOUS SEA IN ALBERTA 



31 



Some suggestions that may help clear the point can be drawn from 

 a study of the section of the deposits as found across the plains, which 

 is here represented in a general diagram instead of a table of formations. 



Idealized west-east section of the Cretaceous measures at the close of 

 the marine period. 



Continental 



Brackish 



Marine 



In the above diagram the vertical scale assumed is much greater 

 than the horizontal. The representation of a succession of beds 

 thickening westward, has emphasized the downwarping of the crust 

 that no doubt occurred. Later, during the mountain building period, 

 a time of folding and uplift, this movement was reversed and. much 

 of the evidence of former subsidence and deposition was removed by 

 erosion. Sufficient exposures, however, remain to establish the general 

 fact as well as to give an indication of the limits to which the sea 

 extended. 



GENERAL REMARKS ON CORRELATION. 



Deposits of marine origin were no doubt formed at the same time 

 as shore-wash brackish-water and even freshwater beds on the adjoin- 

 ing land areas. The correlation of individual members or parts would, 

 therefore, depend altogether on whether the deposition was during 

 the advance or retreat of the sea and on the relative speed of the two 

 movements. 



