ARE THE BOWLDER CLAYS OF THE GREAT 



PLAINS MARINE? 

 Several trains of evidence show that the western plains, as 

 well as the CordiUeran region, have been affected by great 

 changes in elevation relatively to the sea level and to that of the 

 eastern parts of the continent in later Tertiary and Pleistocene 

 times. Facts bearing upon these changes have been detailed by 

 the writer in previous papers and more particularly in those 

 entitled respectively "Later physiographical geology of the 

 Rocky Mountain region," and "Glacial deposits of southwestern 

 Alberta in the vicinity of the Rocky Mountains.'" 



The observations made are in effect such as to lead the wri- 

 ter to believe that the bowlder clays and other deposits of the 

 glacial period covering a large part, at least, of the Great Plains 

 in Canada, are glacio-natant deposits, not directly due to an ice- 

 sheet and not calling for an extension of glacier ice as such to 

 this part of the continent. He has further ventured to suggest 

 that the water covering the western plains at this time may have 

 been at the level of that of the sea and in more or less direct 

 communication with it. The present note relates, however, to 

 the discovery in the bowlder clays of the Great Plains of marine 

 organisms which appear to be contemporaneous with their deposi- 

 tion, and the general observations above alluded to need only 

 be mentioned in introducing the subject. 



Some time ago Mr. T. Mellard Reade, writing in comment 

 on the paper last referred to above, and in the light of his own 

 investigations and those of Mr. Joseph Wright on the bowlder 

 clays of Great Britian,^ suggested that a search should be made for 



'Trans. Royal Soc. Can., Vol. VIII, Sec. 4 (iSQo). Bull. Geol. See. Am., Vol. VII, 



= Cf. Present Aspects of Glacial Geology, T. M. Reade, Geol. Mag.. (IV,) 

 Vol. Ill, p. 542. Bowlder Clay a Marine Deposit, J. Wright, Trans. Geol. Soc. Glas- 

 gow, Dec. 1894 and May 1895. 



257 



