HISTORICAL REVIEW OF THE LARAMIE PROBLEM. 



15 



studies of the fossil plants, was strenuous in his 

 claim that the "Lignitic" and later the Lara- 

 mie were of Tertiary age. 



In 188^-85 Lester F. Ward M instituted an 

 elaborate investigation and comparison of the 

 fossil plants, in the hope of throwing conclu- 

 sive light on its age. Ward was undoubtedly 

 influenced by the prevailing opinion, chiefly 

 that of White, as to what should be regarded 

 as Laramie, with the result, as is now known, 

 of referring to it beds later proved to belong 

 to the Montana, Laramie, Arapahoe, Denver, 

 Lance, and Fort Union, and it is small wonder 

 that he was unable to reach definite conclu- 

 sions. 



From this point on it will be inexpedient to 

 follow 'the strictly chronologic method of 

 treatment, for the reason that the literature is 

 so very extensive and scattered, and conse- 

 quently it will be taken up by regions or 

 special horizons that have, for one reason or 

 another, come into prominence. Each of these, 

 particularly those of special interest as bearing 

 on the problem, will be followed through to 

 the present time. It is to be remembered that 

 the area over which the Laramie was believed 

 to be more or less continuously exposed 

 reached its maximum extension about 1890, 

 since when, by a process of elimination or 

 subtraction, it has constantly been diminishing 

 until at the present time only a comparatively 

 small area remains to support the name. 



RELATIONS BETWEEN THE LABAMIE OF THE 

 DENVER BASIN, TAKEN AS A STANDARD, AND 

 THE REPORTED LARAMIE IN THAT AND 

 OTHER AREAS. 



As set forth in the preceding pages, the his- 

 tory of the Laramie formation shows that it 

 has had what may be called a rise and fall. 

 From the date of the introduction of the term 

 into geologic literature and usage, in 1875, to 

 about 1890 its application was undergoing a 

 process of expansion, until the formation was 

 believed to have covered a vast area extending 

 from northern Mexico to the Arctic Circle and 

 many hundreds of miles in width. In part con- 

 current with this expansion, or from about 1888 

 to the present time, the application of the term 

 has been subjected to a process of elimination 

 or curtailment, until, as was long ago so aptly 



« Ward, L. F., Synopsis of the flora of the Laramie group: U. S. Geol. 

 Survey Sixth Ann. Kept., for 1884-85, pp. 401-557, 1886. 



stated, the problem became not so much "To 

 what age does the Laramie belong ? " as " A hat 

 belongs to the Laramie ? " 



As time went on, it was again and again in- 

 con testably shown that beds supposed to ful- 

 fill the requirements of the definition of the 

 Laramie had been incorrectly so placed for one 

 reason or another, and reasonable doubt had 

 been cast upon the right of many other beds 

 to be considered as typical Laramie. 



It is proposed in the following pages to re- 

 view the several stratigraphic units or geo- 

 graphic areas to which or within which the 

 term Laramie is no longer considered applic- 

 able or at least requires a^greater or less meas- 

 ure of qualification. So far as possible the 

 sequence is chronologic, but naturally it has 

 not been expedient to adhere strictly to the 

 chronologic order, so far as that would lead to 

 needless repetition or to the breaking up of the 

 discussion of a natural geographic unit. Never- 

 theless, it has been impossible to avoid some 

 repetition and overlapping in the treatment, 

 owing to the fact that results obtained in one 

 field may have a more or less important bearing 

 on another field. 



ARAPAHOE AND DENVER FORMATIONS. 



The area about the city of Denver, Colo., 

 now well known as the Denver Basin, is in a 

 way classic ground for geology. It had been 

 visited and studied in greater or less detail by 

 a number of geologists and paleontologists, 

 including J. L. LeConte, F. V. Hayden, Leo 

 Lesquereux, A. R. Marvine, C. A. White, S. F. 

 Emmons, Whitman Cross, G. H. Eldridge, and 

 L. F. Ward. The coal-bearing rocks conform- 

 ably above the marine Cretaceous Fox Hills 

 formation were at first believed to be a southern 

 extension of the "Lignitic group" of the upper 

 Missouri River region and were held by Hayden, 

 Lesquereux, and others to be of Tertiary 

 age. When the Laramie "group" was estab- 

 lished by King, this portion of the section in 

 the Denver Basin and adjacent areas along the 

 Front Range fell within its limits, and the 

 beds Were regarded by him and by those who 

 accepted his views as Cretaceous. This so- 

 called Laramie was for many years regarded 

 as a unit, notwithstanding the fact that at 

 certain points along the base of the moun- 

 tains, notably at Golden, the lower or coal- 

 bearing portion of the section was vertical, 



