20 



LARAMIE FLORA OF THE DENVER BASIN. 



up along the west side. His results were set 

 forth in a paper published in 1912. 75 



COLORADO SPRINGS AREA. 



Although the Colorado Springs area is in 

 practical connection with the Denver Basin 

 and in fact is considered a part of the basin in 

 the present study, there are reasons that make 

 it desirable to treat this area separately and 

 specifically. 



The first fairly comprehensive account of the 

 geology of this area was given in 1869, by F. V. 

 Hayden, 76 who made a reconnaissance study 

 from Cheyenne, Wyo., through the Denver 

 Basin, Colorado Springs, Canon City, and 

 Raton fields. At that time he considered the 

 coal-bearing rocks as belonging to the "Lig- 

 nitic" and of Tertiary age. 



In 1872 Leo Lesquereux " visited this region 

 and gave a brief account of the geologic rela- 

 tions of the coal-bearing rocks, including a sec- 

 tion of the rocks at the Gehrung coal mine ; 

 north of Colorado Springs, which he considered 

 as similar to the section in the Raton Moun- 

 tains. A list of the fossil plants collected is 

 given on page 375 of his report. 



In the following year A. C. Peale 78 also gave 

 a short account of the geology of the Colorado 

 Springs area, but it was mainly a confirmation 

 of the, work of Lesquereux, whose section at the 

 Gehrung mine he quoted. Peale also visited 

 the Franceville coal mines, about 12 miles east 

 of Colorado Springs, and identified portions of 

 the section with that at the Gehrung mine. 

 The fossil plants he obtained at this locality are 

 enumerated on pages 326-375 of his report. 



At this point it is necessary to speak of the 

 so-called Monument Creek group, on account 

 of the part it played in the elucidation of the 

 geologic history of this region. The term 

 "Monument Creek group" was established by 

 Hayden 79 for a series of "variegated beds of 

 sands and arenaceous clays, nearly horizontal, 



'* Lee, W. T., Stratigraphy of the coal fields of northern central New 

 Mexico: Geol. Soc. America Bull., vol. 23, pp. 571-686, 1912. . As already 

 indicated, the complete report on the Raton Mesa region hy Lee and 

 Knowlton was published in 1918 as U. S. Geol. Survey Prof. Paper 101; 

 ' to this report the reader is referred for details of the geology and paleo- 

 botany. 



»* Preliminary field report of the United States geological survey of 

 Colorado and New Mexico, pp. 37-46, 1869; reprint, pp. 137-146, 1873. 



n The Lignitic formation and its fossil flora: U. S. Geol. and Geog. 

 Survey Terr. Ann. Eept. for 1872, pp. 325-327, 1873. 



« Peale, A. C, TJ. S. Geol. and Geog. Survey Terr. Ann. Rept. for 1873, 

 pp. 202-203, 1874. 



™ Op. cit., p. 40. 



resting on the upturned edges of the older 

 rocks, * * * of various colors * * * 

 and of various degrees of texture." This series 

 occurs along the Front Range on the divide be- 

 tween the Platte and Arkansas drainage, where 

 it covers an area "of about 40 miles in width 

 from east to west, and 50 mrles in length north 

 and south." From its modern appearance 

 Hayden concluded that it was of "either late 

 Miocene or Pliocene age." 



In 1873 Cope 80 referred to the "Monument 

 Creek" as follows: 



The age of the Monument Creek formation in relation to 

 the other Tertiaries not having been definitely deter- 

 mined, I sought for vertebrate fossils. The most charac- 

 teristic one I procured was the hind leg and foot of an 

 artiodactyl of the Oreodon type, which indicated conclu- 

 sively that the formation is newer than the Eocene. From 

 the same neighborhood and Btratum, as I have every reason 

 for believing, the fragment of the Megaceratops [obvious 

 error for Megacerops] coloradoensis was obtained. This fos- 

 sil is equally conclusive against the Pliocene age of the 

 formation, so that it may be referred to the Miocene until 

 further discoveries enable us to be more exact. 



In the following year (1874) Hayden 81 again 

 referred to the "Monument Creek group." 

 After describing it at some length, and alluding 

 to Cope's statement regarding the vertebrate 

 evidence, he said: "As to the real age of this 

 group, I am inclined to regard it as Miocene, 

 perhaps upper Miocene." 



The next publication that it is necessary to 

 notice is the Denver Basin monograph, 82 by 

 Emmons, Cross, and Eldridge, though in that 

 work the discussion of these rocks was brief, as 

 they occur in the series of beds mapped only 

 as projecting tongues forming the divide be- 

 tween the Platte and Arkansas waters. Em- 

 mons gave first a brief summary (p. 38) in 

 which, although calling the beds the "Monu- 

 ment Creek formation," he. noted that "two 

 divisions have been distinguished, marked by 

 an apparent unconformity and period of 

 erosion." The lower division was referred 

 tentatively to the Miocene on the basis of the 

 previous vertebrate work of Cope, while the 

 upper division was thought probably to be 

 referable to the Pliocene. 



Eldridge devoted several pages to a general 

 description of the stratigraphic relations, lith- 



80 Cope, E. D., Report on the vertebrate paleontology of Colorado: 

 U. S. Geol. and Geog. Survey Terr. Ann Rept. for 1873, p. 430, 1874. 



» Hayden, F. V., U. S. Geol. and Geog. Survey Terr. Ann. Rept. 

 for 1874, pp. 36, 37, 1876. 



™ Emmons, S. F., Cross, Whitman, and Eldridge, G. H., U. S. Geol. 

 Survey Mon. 27, pp. 38, 39, 252-254, 1896. 



