98 T. FT. Stanton — Stratigraphic Position 



Art. X1Y. — The Stratigraphic Position of the Bear River 

 Formation ; by T. W. Stanton. 



The Bear River formation has been defined and the history 

 of opinion concerning its age and position have been given in 

 the preceding article by Dr. C. A. White. During July and 

 August, 1891, nearly all the well known localities where this 

 formation occurs were reexamined for the purpose of deter- 

 mining if possible its relations to other formations in the same 

 region. The results of this examination are now presented, 

 and as they differ materially from the conclusions reached by 

 a number of geologists who have visited the region it is 

 thought necessary to give somewhat in detail the facts on 

 which they are based. 



The areas studied were (1) at Bear River City,* on the 

 Union Pacific railway twelve miles southeast of Evanston, 

 Wyoming ; (2) on Bear River seven miles north of Evanston ; 

 (3) near the mouth of Twin Creek and on Ham's Fork, both 

 on the Oregon Short Line ; (4) the valley of Smith's Fork 

 from Cokeville, Wyo., twenty miles northward. These locali- 

 ties are scattered over a narrow belt in western Wyoming 

 nearly one hundred miles long extending from latitude 41° 10' 

 to 42° 20'. They will be discussed in the order in which they 

 are named. 



The Bear River City Area. — This is the place of the origi- 

 nal discovery of these strata, as mentioned in Dr. White's 

 article, and nearly all of the discussions of them and their 

 equivalents have been based on observations and collections of 

 fossils made at this place. There is here a small area of highly 

 inclined, folded and faulted Cretaceous and other strata 

 surrounded and overlapped by nearly horizontal Wasatch Ter- 

 tiary beds. The structure of these older beds is very compli- 

 cated and many of the softer beds of shale are not satisfac- 

 torily exposed. It is not claimed, therefore, that all the 

 structural details of this area have been worked out, but suf- 

 ficient has been learned to enable us to assign most of the 

 exposed strata to their proper relative positions in the section. 



The accompanying sketch map which shows the observed 

 dips and strikes of some of the harder strata will render the 

 descriptions more intelligible. Immediately east of Hilliard 

 station there is a ridge of hard light-colored sandstone formed 

 by a faulted anticlinal fold which at this point trends nearly 

 north. The dip on the west side of the fold is about 30° west. 



* This is the site of one of the temporary terminal towns on the Union Pacific 

 railway, at one stage in its construction. It is long since abandoned and the 

 place is now locally known as Bear Town. 



