260 ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



On the west side of the Rocky Mountain barrier the deposits of the 

 Basin Province resemble those of the Plains Province and the environment 

 of life was the same, as far north as southwestern Colorado and southern 

 Utah; beyond, to the north, conditions were radically different through the 

 most of the Basin Province. Only in central Wyoming do the Permo- 

 Carboniferous deposits of the Basin Province shade again into red beds 

 typical of the Plains Province. 



The upper Pennsylvanian sea occupied the Basin Province, depositing 

 heavy limestones and, toward the end, receiving great quantities of sand 

 in its northern half, the present Weber quartzite and its equivalents. The 

 limestone may be traced with a fair degree of certainty into Canada and 

 the quartzite may be followed as far, from its first appearance in central 

 Utah, until the two apparently merge into the Cache Creek formation. 



In the southern part of the Basin Province the elevation permitted red 

 beds of Permo-Carboniferous age to accumulate directly upon the limestone, 

 but farther north the elevation of the barrier to the east must have been 

 somewhat earlier, and the sands of the Weber and its equivalents were 

 deposited under Pennsylvanian climatic conditions. The Permo-Carbon- 

 iferous deposits of the northern half of the Basin Province were laid down 

 in stagnant seas and under climatic conditions not greatly different from 

 those of the late Pennsylvanian. 



The difference in the sediments on the two sides of the barrier reveal 

 important climatic differences. The source of the Weber sands and the 

 limestones and fetid shales of the Park City formation must have been the 

 same as that of the red beds of the eastern side of the barrier, and the 

 structure and size of grain reveal no great difference in the shape or slope 

 of the two sides. The main erosion of the western side took place in late 

 Pennsylvanian under Pennsylvanian climatic conditions and of the eastern 

 side in Permo-Carboniferous time under Permo-Carboniferous climatic condi- 

 tions, but from the absence of red beds on the western side of the barrier, 

 except where it was probably broken down at the northern end, and from 

 the constant indications of the large size of the barrier, the question naturally 

 presents itself whether the barrier may not have interrupted prevailing 

 winds, or otherwise caused a difference in humidity and temperature upon 

 the two sides. 



The sum of accumulating evidence shows that marine conditions pre- 

 vailed in late Pennsylvanian from Alaska south along the Pacific coast to 

 northern California; in British Columbia the sea extended as far east as 

 the west side of the Canadian Rockies and south to the international boun- 

 dary, where it was continuous with the sea which occupied the Basin 



Fig. 8. — Map showing the distribution of late Paleozoic and Permo-Carboniferous deposits in 

 North America. The portion of Canada and the United States to the west of the heavy 

 broken line was the site of deposition in Gschelian time and elevation in late Paleozoic. 



