250 Dake — Episodes in Rocky Mountain Orogeny. 



not characteristic of Wasatch. Nevertheless it must be 

 remembered that both red clay beds, and conglomeratic 

 beds, of similar character, are known in the Wasatch for- 

 mation. 



The large concretions noted so abundantly in these 

 pebbly sandstones are apparently not described by either 

 Hewett or Hewett and Lupton, in the above papers. 

 Fisher^ ^ mentions similar concretions in the Laramie 

 (which formation, as he used the term, includes present 

 Mesa Verde, Meteetsee, and Lance), but does not indicate 

 their horizon. The w^riter noted concretions of the same 

 sort at two horizons in Fisher's Laramie, one near the 

 base, probably in what is now mapped as Gebo or Mesa 

 Verde, the other near the top, in pebbly beds quite cer- 

 tainly corresponding with the Fort Union. These obser- 

 vations w^ere made on Frost Ridge and west into the val- 

 ley of Sage Creek. Similar concretions are described 

 from the Dakota sandstone near Minneapolis, Kansas.^^ 



Lloyd and Hares^^ also report abundant concretions 

 from the Fox Hills, also from the Lance formation, in 

 South Dakota. According to Wegemann,-^ one of the 

 most characteristic features of the Lance formation in the 

 Powder River Basin is the presence of *^ large round con- 

 cretionary masses that weather from the sandstone beds. 

 These masses resemble great bowlders, and some of them 

 are as much as 10 or 15 feet in diameter. '^ In plate 

 XXII A, of the above quoted paper, are shown several 

 such concretions, and it must be admitted that from the 

 photographs they closely resemble those found by the 

 writer. While they point to possible correlation with the 

 Lance, their evidence is probably offset by the other evi- 

 dence cited, and by the occurrence of similar concretions 

 at several different horizons. 



In view of the above facts, the writer is reasonably con- 

 vinced of the equivalence of the pebbly sandstones of this 

 paper with the generally recognized Fort Union of the 

 Big Horn Basin, as described by Hewett and Lupton, 

 though this does not by any means make certain their 



^^ Fisher, C. A.; op. cit., p. 31. 



" Chamberlin, T. Q., and Salisbury, E. D. ; Geology, vol. II, p. 147. 



" Lloyd, E. E., and Hares, C. J. ; The Cannonball Marine Member of the 

 Lance Formation, Jour. Geol., 23, pp. 523-547, 1915. 



20 Wegemann, C. H. ; Wasatch Fossils in So-Called Fort Union Beds of 

 the Powder Eiver Basin, Wyoming, U. S. Geol. Survev, Prof. Paper 108 D, 

 1918. 



