Bake — Episodes in Rocky Mountain Orogeny. 247 



It might be noted here that Fisher^ mentions and illus- 

 trates marked angular unconformity between the Wa- 

 satch and Laramie, near Hart Mountain, north of Cody, 

 but that he does not recognize Fort Union in his sequence, 

 where Hewett later differentiated it, — so that it is not 

 possible to say whether or not the Fort Union is involved 

 in this angular unconformity, as he describes it. 



Hewett and Lupton*^ describe the Fort Union as over- 

 lapping with angular unconformity from Lance (Ho) onto 

 Meteetsee, in other portions of the Big Horn Basin, 

 clearly indicating pre-Fort Union folding and erosion. 



The second episode of deformation followed the deposi- 

 tion of the pebbly (Fort Union 1) sandstone. Near the 

 Middle Palatte Ranch, on Greybull River, in the W. % 

 Township 48 N., Range 103 W., is a marked anticline, in 

 which the pebbly sandstone above mentioned partakes of 

 the folding, with dips up to 15 or 20 degrees, on the east 

 flank of the fold. Similarly, Hewetf^ reports the Fort 

 Union to be dipping about 37° in the Shoshone River Sec- 

 tion, and Hewett and Lupton^ refer to the Fort Union 

 beds as being involved in the folding. 



One of the most interesting features of this, or probably 

 of a still later episode of deformation is the association, 

 with the folding, of enormous over thrust faults. In the 

 locality first described. Sec. 21, T. 52 N., R. 104 W., and at 

 numerous nearby points, the large fault known as the 

 Hart Mountain Overthrust, has shoved Madison (Missis- 

 sippian) limestone out over the pebbly beds here referred 

 to as Fort Union ( ?). As the writer has already pointed 

 out,^ the Madison is not actually seen to rest on the sand- 

 stone, but at many points the sandstone occurs near the 

 foot of bold Madison scarps. If the beds had been laid 

 down against these cliffs, after faulting, they should con- 

 tain an abundance of pebbles and bowlders of the lime- 

 stone, such as now strew these slopes. Very careful 

 search fails to reveal any such pebbles, even where the 

 beds lie in closest proximity to the Madison scarps ; and 

 this fact alone constitutes practically positive proof that 



"Fisher, C. A.; Geology and Water Eesources of the Big Horn Basin, 

 U. S. Geol. Survey, Prof. Paper No. 53, pi. X, and p. 37. 



^Hewett, D. F., and Lupton, 0. T.; Anticlines in the Southern Part of 

 the Big Horn Basin, Wyoming, U. S. Geol. Survey, Bulletin 656, pp. 28-29. 



^Hewett, D. F.; op. cit., p. 110. 



^ Hewett, D. F., and Lupton, T. C. ; loc. cit. 



' Jour, of Geol., 26, pp. 53-54, 1918. 



Am. Jour. Sci.— Fifth Series, Vol. I, No. 3.— March, 1921. 

 17 



