30 THREE GEOLOGICAL PROVINCES. 



Simple Anticlinals, the Uinta structure, and Zones of Diverse Displacement 

 are found as exceptional types. 



In the Park Province the Uinta structure prevails and its primary and 

 concomitant topographic forms are grandly shown. Doubtless a more thor- 

 ough study of this region will result in the discovery of exceptional types. 



THESE PROVINCES NOT SEPARATED BY WELL DEFINED 



LINES. 



No line of demarcation can be drawn between the Plateau Province 

 and the Park Province. There is an irregular belt of country separating 

 the better defined portions of the two provinces, which is complicated by 

 characteristics belonging to each. The Kaibab structure of the plateaus 

 does not change abruptly into the Uinta structure, which prevails in the 

 latter province. In fact there are many areas lying along the border sepa- 

 rating the two provinces which are characterized by a great development 

 of eruptive beds, which serve to a greater or less extent to mask the oro- 

 graphic structure of the sedimentary beds. 



In like manner on the south and west of the Plateau Province there is 

 a belt of country separating it from the Basin Province, itself forming a sub- 

 province of great interest. This region has already been the subject of much 

 study, and although these studies have not been completed, many facts have 

 been discovered from which we can with safety make some important de- 

 ductions. Through late Mesozoic and earlier Tertiary times there was an 

 old shore line here, now retreating eastward, now advancing westward. It 

 is a region of many movements by faulting and flexing, and during these 

 movements, in Tertiary times at least, many lavas were poured out, so that 

 we have many unconformities both abrupt and gentle, many shore deposits, 

 many faults and flexures and many beds of eruptive matter. But the north- 

 ern portion of the Basin Province is separated geographically as well as 

 geologically from the Plateau Province by the Wasatch Mountains which 

 constitute a distinct geographic system; but geologically it is but a northern 

 extension of the intervening belt which I have already described, charac- 

 terized as distinct from that by the fact that the movements of displacement 



