REPORT ON THE STRATIGRAPHY AND PLIOCENE VERTEBRATE PALEONTOLOGY 

 OF NORTHERN COLORADO. 



BY EDWARD D. COPE, A. M. 



The water-sbed between the South Platte Eiver and the Lodge-Pole 

 Creek, is composed superficially of formations of the Pliocene epoch, 

 as defined by Hayden. The latter stream flows eastwardly through the 

 southern parts of Wyoming and ISTebraska, and empties into the South 

 Platte near Julesburg, I^febraska. The Territorial and State boundaries 

 traverse this water-shed from west to east. The springs on its southern 

 slope, which form the sources of the northern tributaries of the South 

 Platte, issue from beneath the beds of the formation above named. At 

 or near this point is an abrupt descent in the level of the country, wbicli 

 generally presents the character of a line of bluft's varying from two to 

 nine hundred feet in height. This line forms the eastern border of the 

 valley of Crow Creek, until it bends to the eastward, when it extends in a 

 nearly east and west direction for at least sixty miles.* At various points 

 along it portions Lave become isolated through the action of erosion, form- 

 ing buttes. Two of these at the head of Little Pawnee Creek are espec- 

 ially conspicuous landmarks, forming truncate cones of about nine hun- 

 dred feet in elevation, as Mr. Stevenson of the survey informs me. 

 They are called the Pawnee or sometimes tlie White Buttes. Near 

 them stand two others, the Castle and Court-House Buttes. 



The upper portion of this line of bluffs and buttes is composed of the 

 Pliocene sandstone in alternating strata of harder and softer consist- 

 ency. It is usually of medium hardness, and such beds, where exposed, 

 on both the Lodge-Pole and South Platte slopes of the water-shed, ap- 

 pear to be penetrated by innumerable tortuous friable silicious rods and 

 stem-like bodies. They resemble the roots of the vegetation of a 

 swamp, and such they may have been, as the stratum is frequently 

 filled with remains of animals which have been buried while it was in 

 a soft state. No better preserved remains of plants were seen. The 

 depth of the entire formation is not more than seventy-five feet, of 

 which the softer beds are the lower and vary in depth from one foot to 

 twenty. The superior strata are either sandstone conglomerate or a 

 coarse sand, cf varying thickness, and alternating relations; the con- 

 glomerate contains white pebbles and rolled Pliocene mammalian re- 

 mains. 



This formation rests on a stratum of white friable argillaceous rock 

 of Miocene age, probably of the White River epoch, as I believe from 

 the presence of the following species which I detected in it: Hyaenodon 

 horridus, IT. crucians ] Oreodon culherisonii, 0. gracilis; Poebrotherium 

 vilsonii, Aceratherium Occident ale ^ Hyracodon nehrascensis, Anchitherium 

 hairdii, Palaeolagus liaydcnii, Ischyromys typvs, Miis elegans, etc. The for- 

 mation extends to a depth of several hundred feet, and rests on a stratum 

 of a fine grained, harder, argillaceous rock of a dark-brown color. Some 

 of its strata are carbonaceous, and contain vegetable remains badly 

 preserved ; others are filled with immense numbers of fresh and brack- 



*See Berthoud Proceed. Acad. Nat. Sci., Phil a., 1872, p. 48, where they are mentioned. 



