192 EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



bis Report on the Geology of the Uinta Mountains, and also noticed in 

 the American Journal of Science, vol. xi, 3d series, p. Kit. 



The Bijou Creek locality, the strata and fossils of which have been de- 

 scribed on previous pages, is the same one at which the marine fossils just 

 referred to were reported to have been obtained by Professor Powell, and 

 I visited it with specific information furnished by him.* That collection of 

 Professor Powell's was composed entirely of marine species, among which 

 was a coral, and they were referred by me to the age of the Eocene Tertiary 

 strata at Yicksburg, Miss. The fossils which I found at the Bijou Creek 

 locality were not only all of different species, but they were ali of either 

 brackish- or fresh-water origin, and identical with species especially char- 

 acteristic of the Laramie Group. The serial continuity of the strata 

 seems so perfect, from the uppermost strata of the Fox Hills Group as 

 seen in the valley of the South Platte and its branches, to those of the 

 Monument Creek Group upon Cherry Creek Plateau, that it is in the 

 highest degree improbable that a marine deposit could have been made 

 in this region between the close of the Fox Hills epoch and the begin- 

 ning or even the close of the Monument Creek epoch. If such a deposit 

 were made there at the close of the latter epoch we ought to find it, if 

 found at all, resting on the uppermost strata of the last-named epoch, 

 but none has been reported to exist there. If made at the beginning of 

 the Monument Creek epoch the conformity of its strata upon those of the 

 Laramie Group could not be either real or apparent as it is now. From the 

 explanation that has already been given of the character and condition 

 of the strata between the South Platte and Arkansas Elvers it is evident 

 that if a marine deposit later than the Cretaceous really exists there it 

 must rest unconformably upon the eroded surface of Laramie strata. 

 The great erosion that has left the strata of that region in their present 

 condition took place after the close of the Monument Creek epoch, and 

 that would bring the date of such an assumed marine deposit later than 

 that which is indicated by the character of the fossils of Professor Pow- 

 ell's collection. From these facts and considerations I am forced to the 

 conclusion that the marine Tertiary fossils referred to were collected in 

 some more eastern region and that they were inadvertently substituted 

 in the collections furnished me by Professor Powell for investigation 

 for fossils that he did collect in the valley of Bijou Creek. 



Scarcely any subject connected with the geological history of North 

 America could be of more absorbing interest than that of the exact 

 chronological relation of the marine Tertiary deposits of the sea-border 

 regions with the fresh- and brackish-water deposits of the western inte- 

 rior of the continent. It is to be hoped that this subject may yet receive 

 elucidation from discoveries similar to that which was supposed to have 

 been made in the valley of Bijou Creek ; but it now seems evident that 

 we need not look for them east of the Rocky Mountains in any district 

 west of Western Kansas. This subject is further referred to in discus- 

 sions upon later pages of this report. 



From the Cherry Creek Plateau I went to the neighborhood of Golden 

 City by way of Denver without adding any material geological or pale- 

 ontological facts to those already recorded. In my investigation of this 

 district I was accompanied by Mr. Arthur Lakes, of Golden City, and 

 our first examinations were made at the village of Morrison, seven miles 

 to the south of Golden. The strata here are exposed on a grand scale, 



* In Professor Powell's report on the geology of the Uinta Mountains the name of 

 the locality is given as "Bijou Basin," which was intended to mean the valley of the 

 Bijon Creek, and not a locality near the head of the creek to which that name is given 

 on some maps. 



