Haj'den.] ' 421) fMay 6, 



Sections of Strata belonging to the "Bear Eiver Group," near 

 Bear Eiver City, Wyoming Territory. 



By F. V. Hayden, M. D. 



Read May 6, 1870. 



During my explorations along the line of the Union Pacific Railroad, 

 last autumn, my attention was attracted by two of the most remarkable 

 artificial cuts or excavations that I have ever seen in the West. They are 

 located about a mile west of Bear River City, or nearly 950 miles west of 

 Omaha. No such exhibitions of the strata can be found in the country, 

 formed by natural causes. Usually the rocks of the modern formations 

 are composed of such soft materials that they have readily decomposed on 

 the surface, covering it with a considerable thickness of debris, thus con- 

 cealing, in many instances, not only the true character of the underlying 

 rocks, but also many of the details of the stratification. 



At my request, Mr. H. R. Durkee, an excellent civil engineer, residing 

 at Bear River City, made a careful survey of the cuts, and noted the char- 

 acter of each layer, with its thickness in feet and inches. Some of the 

 layers are so crowded with fresh water sliells that they seem almost made 

 up of them. A list of them is given in Mr. Meek's Catalogue. 



Upon the surrounding hills, among the debris rock from these beds, the 

 fossil shells are so abundant that they may be gathered by the bushel, like 

 nuts in autumn, in a fine state of preservation. The strata are all re- 

 garded as of lower Tertiary age, and belong to what I have denominated 

 the Bear River Group. All the beds in this vicinity are very much dis- 

 turbed, holding a nearly vertical position, or inclining at a high angle. I 

 desire to call the attention of scientific men to these sections as they 

 travel along this portion of the road, and for that reason I regard them 

 of some value. I shall hereafter work up the geology of this district 

 more in detail, and simply wish to make a record of these facts at the 

 present time. 



Commencing at the Eastern Extremity op the Cut. 



No. Description. Feet. In. 



1. Clay, Greyish, Black, contains fragments of sandstone, 10 



2. Limestone, Blue, 2 



3. Clay, Greyish-black, 6 



4. Clay, Brown, hard, and in large fragments, 1 



5. Clay, Black, " " small " 1 



6. Limestone, Blue, Fossiliferous, 1 6 



7. Clay, Greyish-black, • 1 2 



8. Sandstone, Fragmentary, 2 



9. Clay shale. Grey, 1 



10. Clay, Gi'eyish-black, very compact, 1 



11. Clay shale. Black, 10 



12. Marl, shells in fragments, 8 



13. Clay shale. Black, 6 



14. Limestone, much shattered, and in angular pieces, 2 



