192 The Tertiary Formations of the [March, 



horizon. 1 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 any my- 

 self have seen it in Northern and Western Kansas. There is a 

 near lithological resemblance between the strata at these local- 

 ities, and the fauna presents a common character as distinguished 

 from those which preceded and followed it; but sufficient care 

 has not always been exercised to distinguish its upper members 

 from the Eqmis beds above them. The latter contain a distinct 

 fauna. 2 



According to King, about .1500 feet of beds are included in 

 this formation. 



The water-shed between the South Platte river and the Lodge 

 Pole creek, Colorado, is composed superficially of formations of 

 the Loup Fork epoch, of Hayden. On its southern side is an 

 abrupt descent in the level of the country, which generally pre- 

 sents 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 bluffs 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 the Lodge Pole and South Platte 

 slopes of the water-shed, appear to be penetrated by numerous 

 tortuous friable silicious rods and stem-like bodies. They resem- 

 ble the roots of the vegetation of a swamp, and such they may 

 have been, as the stratum is frequently filled with remains of ani- 

 mals which have been buried while it was in a soft state. No 

 better preserved remains of plants were seen. 



This formation rests on a stratum of white friable argillaceous 

 rock of the White River epoch, as represented in Fig. 7. 



The lithological characters above described are precisely those 

 presented by the same formation in New Mexico. 3 



Mr. King employs the name Niobrara for this formation, but 

 Dr. Hayden's name 4 was introduced many years previously. The 



*Ann. Rep. Chief of Engineers, 1874, 11, p. 603. 



2 See Bulletin U. S. Geol. Surv. Terrs., iv, p. 389, and v, p. 47. 



3 See Report Lieut. G. M. Wheeler's Explorations west of iooth Meridian, Vol, 

 iv, p. 283. 



*See Dana's Manual of Geology, edit. 1864, p. 511. 



