THE LARAMIE FORMATION AND THE SHOSHONE GROUP 3 1 



an upper theoretical limit which might nowhere be represented, 

 owing to the assumed pre-Tertiary erosion. It was to embrace the 

 upper group of conformable Cretaceous sediments, deposited in 

 brackish or fresh waters during gradual continental uplift. A long 

 period of non-deposition and great erosion in the Rocky Mountain 

 region was assumed by King and by other stratigraphers and paleon- 

 tologists of thirty years ago to mark the interval between Cretaceous 

 and Eocene sedimentation. Hayden's view as to the age of the Lara- 

 mie was largely due to Lesquereux's opinion that the flora was 

 Tertiary, but, as the quotation above given shows, he thought of the 

 Laramie in its fundamental stratigraphic relation as the brackish 

 water deposit succeeding the marine Cretaceous through gradual 

 uplift. 



Although the Laramie was simple in its essential definition and 

 conception, the strata referred to it included local deposits as well 

 as those of wide distribution, and knowledge concerning some of 

 these beds was very meager and untrustworthy when the group was 

 established. It is a most natural result of detailed studies during 

 the last thirty years that several formations at the top of the group 

 assumed to have the relations embodied in King's definition, have 

 been found to possess other relations. But there is still a large for- 

 mation or group answering to the fundamental part of King's defi- 

 nition, and to such beds it seems to me both most natural and most 

 expedient to apply the term Laramie in future. In the Laramie 

 Plains there are, according to Veatch, 6,500 feet of conformable 

 Cretaceous beds above the Montana marine strata and below the 

 break at the base of the Carbon beds. The geographic term is thus 

 still appropriate, even if the Carbon section be excluded from the 

 Laramie. The term has now been so widely applied and for such 

 a long time that it appears to me unwise to drop it even if there 

 should prove to be no true Laramie beds on the Laramie Plains, as 

 Veatch uses that designation. 



Among the districts named by King as exhibiting Laramie beds 

 in representative manner is the eastern foot hill zone of the Front 

 Range in Colorado, where they were known also to geologists of the 

 Hayden Survey. It was in this region that Eldridge and myself 

 discovered that the section referred to the Laramie by both Hayden 

 and King consisted of two parts: a lower one, conformable with the 



