454 GEOLOGICAL SURVEY OF THE TEERITOKIES. 



age of the railroad, one of the most interesting series of beds (division 

 28) anywhere to be seen on the whole line of the Union Pacific Rail- 

 road.* This cut is about 150 to 200 yards in length, and passes through 

 the strata nearly at right angles to their strike. The beds thus exposed 

 consist of numerous thin seams of dark and liglit grayish colors alternat- 

 ing, so as to present a banded or striped appearance, the darker bands 

 being more or less Carbonaceous, or even in some cases containing thin 

 streaks of coal ; while the lighter layers are more arenaceous, calcareous, 

 or argillaceous. All of these beds and seams are tilted up so as to dip 

 nearly eastward at an angle of about 75"^ below the horizon, being thus 

 not exactly conformable to any of the other divisions of the section, 

 though apparently upheaved at the same time. They contain immense 

 numbers of fossil shells, belonging to a few species of fresh and brackish 

 water types, some of which are closely allied to European Lower Eocene 

 si)ecies. 



Toward the western extremity of this cut the upper ends of the strata 

 are suddenly flexed westward, as if they had been struck, after their up- 

 heaval, by an iceberg, or some other tremendous force, coming from the 

 east. There is no evidence, however, that this flexure was produced by 

 any agency of this kind : on the contrary, it is almost certainly a mere 

 fragment, as it were, of one of the folds of the strata, caused by the powerful 

 forces to which they have been subjected, by the combined action of 

 upheavals and lateral pressure. 



This division of the section, I have alivays referred provisionally to 

 the Lower Eocene, though I have, at the same time, intimated that it 

 may yet be found to belong more i^roperly to the Upper Cretaceous. I 

 will return to this subject again, however, in another place, further on, 

 when speaking of Tertiary collections. 



In regard to the coal beds 7 and 12, in the Cretaceous formation here 

 at Bear Eiver, I should think that there can scarcely be any reasonable 

 doubt that they will be of considerable value. The mines had, however, 

 apparently been worked but little, and as nothing had been done in 

 them for some time before our visit, the entrances were partly filled by 

 the falling of the adjacent rocks and shale, so that we could not exam- 

 ine them very carefully. We were informed by Mr. Thorpe, however, 

 the owner of the property, that each of the beds seen there is 7^ feet in 

 thickness, and that the coal is of excellent quality. It is doubtless simi- 

 lar to that mined in the same formation at Coalville. The mines are 

 exceedingly convenient to the railroad, which passes along so close to 

 that in the bed 7, that the miners' carts can run out upon a j)latform at 

 the entrance of the mine and tip directlj^ into coal-cars on the railroad ; 

 while the opening into the other bed, 12, is only about 100 to 150 yards 

 from the road. 



Below Gallatin City. — The fossils from near the Missouri River, below 

 Gallatin City, Montana, belong clearly and beyond doubt to the Cre- 

 taceous, and about to the horizon of the Fort Benton group or subdi- 

 vision of the Upper Missouri Cretaceous series. A few of the bivalves 

 appear to belong to the fresh or brackish water type, Veloritina, 

 but all of the others are marine forms. It is an interesting fact that a 

 Trigonia, in this collection, is so near T. Eransi from the Cretaceous 

 beds of Vancouver's Island, that no reliable differences can be seen 

 from the imperfect specimens found. So far as I have been able to de- 



* For a very minutely detailed section of this cut, prepared by H. R. Durkee, esq., 

 one of the engineers of the Union Pacific Railroad, see Dr. llaydeu's rej)()rt of 1870, p. 

 153, It only illustrates the beds seen in the cut, however, without showing their rela- 

 tions to the other beds seen in our section. 



