346 B. WILLIS — LEWIS AND LIVINGSTON RANGES, MONTANA 



mated on the basis of observations near Swift Current falls and on North 

 fork of Kennedy. 



The writer concludes that the altitude of the Lewis range above the 

 Great plains is due to the vertical throw of the Lewis overthrust ; and 

 also conversely that the observed displacement on the Lewis thrust 

 nearly approaches the actual, since much greater displacement on the 

 probable dips would have resulted in greater elevation. 



Heights and anticlines. — In northern Lewis range and in Livingston 

 range greatest altitudes are in general related to anticlines. In Lewis 

 range an anticlinal axis already described is definite in mount Cleveland 

 (10,438 feet above sea), swings southeastward about the head of Belly 

 river near mount Merritt (9,944 feet), trends again southward through 

 mounts Wilbur (9,293) and Gould (9,541 feet), and is lost in an expanse 

 of nearly level strata centering about Citadel (9,024 feet). In mount 

 Cleveland, where the anticlinal is narrow and dips from the axis exceed 

 10 degrees, the altitude is the greatest of the range. In mount Merritt 

 the fold is broader and dips are 5 degrees or less. Farther south the 

 arch is merely a leveling of the southwesterly dip, with reference to 

 which it occupies a lower monoclinal position, and the heights named 

 above are also lower than others which lie farther east. Thus Siyeh 

 (10,004), Going-to-the-sun (9,594), and Little Chief (9,542 feet) lie east 

 of the anticlinal zone and are cut from elevated edges of hard strata dip- 

 ping southwest. The many heights slightly above or below 9,000 feet, 

 which are grouped between McDonald lake and the headwaters of Saint 

 Mary river, appear to correspond with the widening area of level strata. 

 The anticlinal axis winds from north-south to southeast and back to 

 south, and Lewis range trends with it. Where the axis widens' to a 

 bench in the southwest-dipping monocline the range also widens and 

 loses its distinctive crest. Thus there is a relation between altitude as 

 expressed in peaks and elevation due to folding, and there is also a 

 general relation of mountain belt to anticlinal zone. 



In Livingston range an anticlinal axis may be noted west of mount 

 Heavens (8994) and near the head of Logging lake, where a group of 

 nameless peaks reaches 8,500 feet. The arch crosses spurs jutting south- 

 westward from the crest, which is on the eastern anticlinal limb. Be- 

 yond Logging lake northwestward the mountains rise to heights between 

 9,000 and 10,000 feet, but the axis was not observed. It probably is cut 

 off and thrown down by the North Fork normal fault. The position of 

 the crest is an accident of erosion due to the work of streams and glaciers, 

 which under favoring conditions of slope and exposure have forced the 

 divide eastward till it is now from 1 to 4 miles east of the anticline. In 



