262 W. Cross — Denver Tertiary Formation. 



what is now commonly called the Laramie Group. Numerous 

 fossil leaves have been obtained in these vertical coal-measure 

 rocks, but they have been found much more abundantly in the 

 -horizontal strata of Table Mountain, and although the inter- 

 vening space is largely obscured by surface deposits, the plants 

 of the two horizons have always been treated collectively, by 

 both geologists and palaeontologists, as coming from a single 

 Formation, however that may have been designated. Among 

 those who have described the vicinity of Golden, with more or 

 less detail concerning the strata under consideration, may be 

 mentioned : John L. LeConte, F. Y. Hayden, Leo Lesquereux, 

 A. R. Marvine, C. A. White, and Lester F. Ward.* 



In the summer of 1881 the writer first observed that the 

 Table Mountain strata possessed characteristics proving them 

 to belong to a series distinct from the normal Laramie. In the 

 course of the field-work preliminary to a report upon the 

 geology of the Denver Coal Basin, under the direction of Mr. 

 S. F. Emmons, of the U. S. Geological Survey, it was found 

 that the beds of Table Mountain belonged to a series occupy- 

 ing a Tertiary basin extending eastward underneath and beyond 

 the city of Denver, — whence the name here applied. It was 

 further shown, by Mr. George H. Eldridge, my colleague in 

 this work, that there existed another distinct Tertiary Forma- 

 tion between the Denver and the Laramie, provisionally called 

 by him the " Willow Creek beds." Mr. Eldridge has more- 

 over identified this lower Tertiary Formation even at Golden, 

 in the gap between the coal beds and Table Mountain. 



This article can only treat of the more important facts pecu- 

 liar to, or best exhibited by, the beds in question, and 

 broader or more local relationships must be left for the final 

 report. 



A preliminary statement of the most important results of this 

 investigation was made in two papers read before the Colorado 

 Scientific Society, July 2, 1888, by Mr. Eldridge and the 

 writer. Aside from the identification of the two Tertiary 

 Formations, many important observations were made by Mr. 



* J. L. LeConte. — " Notes on the Geology of the Survey for the extension of 

 the Union Pacific Railway, from Smoky Hill River, Kansas, to the Rio Grande." 

 Phila., 1868, p. 51. F. V. Hayden.— Second Annual Report, U. S. G. & G. S., 

 1868. p. 135; Third Annual Report U. S. G. & G. S., 1869. p. 35; Bulletin 4, 

 Second Series, U. S. G. & G. S., p. 215 ; Sixth Annual Report, TJ. S. G. & G. S., 

 1872, p. 328. Leo Lesquereux. — Monographs of the TJ. S. G. & G. S., vol. vii, 

 "The Tertiary Mora," 1878; vol. viii, "The Cretaceous and Tertiary Floras," 

 1883. A. R. Marvine. — Seventh Annual Report, TJ. S. G. & G. S., 1873, pp. 109, 

 130. C. A. White.— Eleventh Annual Report, U. S. G. & G. S., 1877, p. 192. 

 L. F. Ward. — "Synopsis of the Flora of the Laramie Group." Extract from the 

 Sixth Annual Report of the Director, TJ. S. Geological Survey, Wash., 1886, p. 

 537. "Types of the Laramie Flora." Bulletin 37, TJ. S. Geological Survey. 

 Wash., 1887. 



