LOUP FOEK EPOCH. 17 



same horizon * Messrs Hayden and King have discovered it west of the 

 Wasatch Range in Utah and Nevada, and Marsh has observed it in Oregon. 

 Messrs. Dana and Grinnell found it occupying the valley of Deep River in 

 Montana, and Professor Mudge and myself have seen it in Northern and 

 Western Kansas. There is a near lithological resemblance between the 

 strata at these localities, and the fauna presents a common character as dis- 

 tinguished from those which preceded and followed it; but sufficient care 

 has not always been exercised to distinguish its upper members from the 

 Equus beds above them. The latter contain a distinct fauna.f 



According to King, about 1,500 feet of beds are included in this 

 formation. Hayden found 300 to 400 feet on the Loup Fork and Niobrara 

 Rivers. The following is his section, beginning at the top: 



It consists of, "1st. Drab-gray or brown sand, loose, incoherent, with 

 remains of mastodon, elephant, etc. 2d. Sand and gravel, incoherent. 

 3d. Yellowish-white grit, with many calcareous arenaceous concretions. 

 4th Gray sand with a greenish tinge ; contains the greater part of the or- 

 ganic remains. 5th. Deep yellowish-red arenaceous marl. 6th. Yellowish- 

 gray grit, sometimes quite calcareous, with numerous layers of concretion- 

 ary limestone from 2 to 6 inches in thickness, containing fresh-water and 

 land shells, Succinea, Limnfea, Paludina, Helix, etc., closely allied and per- 

 haps identical with living species ; also much wood of a coniferous charac- 

 ter." The White River section appears at the upper part of the table, on 

 page 14. 



The water-shed between the South Platte River and the Lodge Pole 

 Creek is composed superficially of formations of the Loup Fork epoch, as 

 defined by Hayden. On its southern side is an abrupt descent in the level 

 of the country, which generally presents the character of a line of bluffs 

 varying from 200 to 900 feet in height. This line bends to the eastward, 

 and extends in a nearly east and west direction for at least sixty miles. 



The upper portion of this line of blufi's and buttes is composed of the 

 Loup Fork sandstone in alternating strata of harder and softer consistency. 

 It is usually of medium hardness, and such beds, where exposed, on both 



•Ann. Eep. Chief of Engineers, 1874, 11, p. 603. 



t See Bulletin U. S. Geol. Surv. Terrs, Iv, p. 389, and v, p. 47. 



2 c 



