THE OROGENIC EPOCHS IN NORTH AMERICA 

 TABLE I — Continued 



637 



phenomena characteristic of it, and the distribution of the effects 

 in varying degree. 



THE INDIVIDUAL EPOCHS OF DEFORMATION 



Laurentide orogeny {late Archean). — -This may be included in 

 our table more for the sake of completeness than because much 

 information can be given concerning it. In the Lake Superior dis- 

 trict, and particularly north of Lake Superior, the Archean rocks 

 are generally more deformed and metamorphosed than the Algon- 

 kian strata which overhe them unconformably. In nearly all other 

 districts where the Archean has been identified the same condition 

 prevails. Whether these facts are to be interpreted as indicating 

 a single almost universal orogenic disturbance just before the 

 Algonkian deposits were laid down, or several, if not indeed many, 

 such disturbances affecting successive strips of the continent at 

 different times, is not now determinable. Considering the perio- 

 dicity and local effects of the foldings in later geologic times, the 

 latter view is perhaps the more favored one. 



Mesahian orogeny {late Middle Huronian). — In northeastern 

 Minnesota and adjacent portions of Canada the Upper Huronian 

 (Animikean) strata lie gently tilted upon the contorted and partly 

 metamorphosed beds of early Huronian and Archean age. The 

 interval during which these folds were made and truncated has 

 been termed the "Eparchean interval" by Lawson,^ and by him 



^ A. C. Lawson, Bull. Dept. of Geol. Univ. of Cal., Ill (1902), 51-62. 



