25i Dalxe — Episodes in Rocky Mountain Orogeny. 



* * * but also thej are separated from the ^Laramie* 

 (^ Lower Laramie') by an unconformity, which, according 

 to Veatch, is profound and has involved the removal of 

 perhaps as much as 20,000 feet of sediments.'' He also 

 says that the Lance is ^ ^ stratigraphically, structurally, 

 and paleontologically inseparable from the Fort Union. ' ' 

 This latter statement will certainly not hold for the Lance 

 and Fort Union, as those terms are used in the Big Horn 

 Basin by Lupton and Hewett. 



Concerning an area between Cheyenne E-iver and Can- 

 nonball River, Knowlton further says, '^ Above the Fox 

 Hills, but as will be shown later, with the intervention in 

 places of a distinct unconformity, comes the Lance forma- 

 tion, above which, but without unconformity or other 

 observed break, is the acknowledged Fort Union. ' ' Stat- 

 ing the proposition more generally, he says of the rela- 

 tions of the Lance to the Fort Union, ^^ There is yet to be 

 observed a single locality at which unconformable rela- 

 tions have even been suspected." This also is contrary 

 to the Big Horn Basin conditions. There, Hewett and 

 Lupton"^^ call attention to angular unconformity between 

 Lance and Fort Union, but mention no unconformity at 

 all at the base of the Lance. Similarly, Hewett^^ fails to 

 mention any unconformity at the base of his Ho (Lance) 

 formation. 



The data presented above favor the conclusion that the 

 Lance and Arapahoe beds are correctly correlated and 

 that there is a true pre-Lance epoch of deformation in 

 both the Eastern Wyoming- Western Dakota area and in 

 Colorado. ^A^at then is the answer to the apparent ex- 

 ception in the Big Horn Basin, where all the epochs of 

 folding appear to be post-Lance? We can probably not 

 answer that question, until the correlation between the 

 Big Horn Basin and the type Lance is more thoroughly 

 w^orked out. 



Incidentally it may here be noted that the occurrence of 

 a typically marine Fox Hills fauna in undoubted Lance 

 beds^^ tends to tie the Lance more closely with marine 

 Cretaceous than with the terrestrial Tertiary beds. 



2" Hewett, D. F., and Lupton, C. T. ; loe. cit. 



^^ Hewett, D. F. ; loc. cit. 



^ Lloyd, E. R., and Hares, C, J. ; loe. cit. 



