216 ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



It does not seem at all probable that the phosphates of the Permo- 

 Carboniferous may be referred to accumulations of guano, as the character 

 and, so far as we know, the habits of the animals of the time were not such 

 as to permit such accumulations. Nor does there seem any way in which 

 the phosphate may have accumulated by secondary enrichment to the 

 extent in which they now exist. The suggestion by Blackwelder of original 

 accumulation in a stagnant sea seems by far the most reasonable suggestion. 

 If this be so then we must add to our picture of the surface of the North 

 American continent at the end of the Paleozoic a great, shallow, stagnant 

 sea covering the greater part of the northern end of the Basin Province 

 within the limits of the United States and becoming gradually shallower 

 toward the north. As shown by the various sections given, the sea was not 

 stagnant through all of its history, for at intervals it received normal lime- 

 stone deposits and many series of normal shales and sandstones, but at least 

 twice it was reduced to this state. What its borders were to the north we 

 may not know, as the exposed material there is not yet exactly placed in 

 the geological series, and if, as seems probable, the deposits are older than 

 the phosphate beds, the record has been removed by erosion. To the south 

 the sea evidently terminated in shallower water and great flats and shores 

 upon which accumulated the typical red beds. 



The difference in the conditions of deposition on the two sides of the 

 northern end of the barrier which separated the Plains and the Basin 

 Provinces is not clear. It would appear that the red sediments of western 

 Wyoming gradually shaded into a sea, possibly a portion of the extension 

 from the Pacific Ocean which at times assumed the character of a relict sea. 

 The gradual elevation which was in progress from north to south, from 

 Alaska to northern California, extended its influence eastward and may 

 have been of large influence in cutting off and confining portions of this sea, 

 converting them at times into inclosed bodies of water which became 

 stagnant. 



G. INTERPRETATION OF CONDITIONS IN BRITISH COLUMBIA 



AND ALASKA. 



In attempting an interpretation of the condition at the close of the 

 Paleozoic in British Columbia and Alaska, it will be well to summarize 

 briefly certain conclusions expressed by Daly^ in his memoir on the geology 

 of the forty-ninth parallel. On page 6 he divides the entire cordillera into 

 an Eastern geosynclinal belt and a Western geosynclinal belt. The two 

 overlap in the vicinity of the Columbia River. The eastern belt extends 

 from the summit of the Selkirk Range, just east of the Columbia River, to 

 the Great Plains. The formations are almost entirely sedimentary and 

 are included in one general structure which Daly refers to as the Rocky 



1 Daly, R. A., Geology of the North American Cordillera at the Forty-ninth Parallel, 

 Canadian Geological Survey, Memoir 38, 1912. 



