DEVELOPMENT OF COMPLEX STRUCTURE BY ICE-SHEET 



429 



The absence of marked infolding of glacial material is due to the fact 

 that glacial deposits are largely found in the valley and that the hills 

 were probably truncated by the movement of the ice-sheet across their 

 tops. Thus the hills as seen today may be only the roots of former hills 

 of which the strata comprising them have been jumbled up and their 

 tops cut off by the planing action of the ice-sheet. 



Figure 10. — Development of Structure of Mud Suites 



Sketches a, t, c, d represent hypothetical stages in the development of the complex 



structure of Mud Buttes 



Summary 



Briefly stated, then, there is a belt in eastern Alberta where the upper 

 member of the Belly Eiver formation outcrops, and in some of the hilly 

 portions of this belt the soft incompetent strata are intensely folded with- 

 out bringing to the surface the older more deeply buried beds. There is 

 no disturbed region outside of this belt from which stresses, such as are 

 indicated by the folding at Mud Buttes, might have been transmitted. 

 There is no apparent change in the width of the outcrop of the Belly 

 Eiver formation in the vicinity of these intensely folded areas such as 

 might be expected to result from such folding. 



Nowhere in eastern Alberta do the river sections exhibit or indicate 

 folding, but wherever the dip is determinable the strata are nearly hori- 

 zontal, dipping at the rate of only a, few feet per mile toward the south- 

 west. Corroborative evidence of this gentle dip toward the southwest is 

 found in the records of deep wells drilled in the region. 



