30 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



PROMONTORY 

 RANGE (Olsen) 



WESTERN 

 UINTA WITS. 



ILARSEN) 

 € QTZ. 



RED PINE 

 SHALE 



\, 





x3 





\4_ 



S 



UTAH 



Fig. 4.5. Correlation chart of Precambrian formations in northern Utah. After Larson, 1957. 



orogenic belt, and its extent is assumed to be approximately that of the 

 Beltian trough. The conglomerates appear to have come from the west, 

 and if so, the orogeny was most severe along the western margin of the 

 trough. 



The age of the Beltian orogeny cannot be accurataely fixed with exist- 



ing data. A sample of illite from a shale in the Siyeh formation in Glacier 

 National Park (Goldich et al, 1959) yielded a date of 740 m.y. by the 

 potassium-argon method and 780 m.y. by the strontium-rubidium method. 

 Goldich et al. reason that this age is not a time of metamorphism but 

 more probably marks the time of deposition. The Siyeh formation is near 



