STRUCTURE 331 



west, and that of cleavage north 45 degrees west ; dip, 40 degrees south- 

 west. The structures in mount Stanton and above Logging Creek lake 

 are exceptional. Of a different type is a broad flexure, an anticlinal 

 swell within the syncline. The axis passes through mount Cleveland 

 (elevation, 10,438, the highest in the Lewis range), and thence south 30 

 degrees east through mount Merritt and mount Wilbur, where the fold 

 dies out. It is noteworthy that the axis carries the major heights of the 

 range. It is a very gentle rise of the strata, usually marked by opposing 

 dips of 5 degrees or less ; but in mount Cleveland the northeasterly dip 

 becomes as much as 10 degrees. Between mount Cleveland and Belly 

 river the westerly opposing dip is 20 to 35 degrees. 



LIVINGSTON ANTICLINE 



The western limit of the Front Ranges syncline is an anticlinal axis, 

 which may be traced just west of the summit of Livingston range in 

 spurs jutting out between Camas and Logging creeks. It is indicated 

 by southwest dips of 5 to 20 degrees, and thus appears to maintain the 

 comparatively gentle inclination of strata observed in the Lewis range 

 in the same direction. Between the high spurs the axis is buried be- 

 neath drift which fills the valleys, and northwest from Logging creek no 

 instance of southwesterly dip was observed. Conditions of normal fault- 

 ing and erosion appear to have resulted in removal of the western limb 

 above drainage lines throughout much of the range. 



LEWIS OVERTHRUST 



Character and extent. — The simple structure of the Algonkian series 

 overlies a great dislocation. Along the eastern front of the Lewis range 

 Altyn limestone rests upon Cretaceous rocks. This inverted relation 

 was noted from Saint Mary lakes to Waterton lake, a distance of 28 

 miles in a straight line northwest, and across the general trend the con- 

 tact was observed to have a width of 5 to 7 miles. The outcrop of Altyn 

 limestone over Cretaceous was observed in a sinuous course, as shown on 

 the map (plate 48 and also figure 4), from Single Shot around the val- 

 leys of Swift Current and Kennedy creeks, around the promontories of 

 Appekunny, Yellow, and Chief mountains, past the forks of Belly river 

 and into Canada. The surface of contact was actually seen only beneath 

 Chief mountain, but its position was determined within 20 feet or less at 

 several points. Each series near the contact has yielded fossils, which 

 afford conclusive evidence that in age they are separated by all of Paleo- 

 zoic and most of Mesozoic time, and that the older is on top. This rela- 

 tion is interpreted as an overthrust (figures 1 and 2, plate 52). A sim- 



