


4 Ze ‘a4 + “f bf ’ ; 
4 i oy. ete tn 6 
‘ rr | 
» ¢ . 4 ~ 
* ve Tul net Bye 
Abb Sar Sieg ici mae 
iP ee io 
AGE OF THE LIGNITE FORMATION. 
oe to believe that they represent a different horizon.* The lignite- 
bearing rocks of the forty-ninth parallel, from about longitude 110° 30’ 
westward, belong with few exceptions to the salt and brackish water 
series, and closely resemble those of the eastern and western flanks of 
the Rocky Mountains further south, both lithologically and paleeonto- 
logically. Specific identity probably obtains between molluscs from the 
vicinity of the Buttes, and both those of the Coalville and Bitter Creek 
series of Dr. Hayden. 
440. Dr. Hayden, whose authority with regard to the stratigraphical 
relations of the western beds can scarcely «be disputed, in all his earlier 
publications and reports, refers the whole of the lignite-bearing rocks,— 
which as already stated he considers as an unbroken series,—to the 
Tertiary, and attaches them to the Miocene division. Writing in 1857, in 
conjunction with Prof. Meek, he says :—‘‘ We have no evidence that 
any of the Tertiary deposits now known in Nebraska are older than the 
Miocene. The great lignitic basin, and the Mauvaises Terres of White 
River, though probably both Miocene, are not exactly on a parallel.” + 
Again, in the same year, in his Notes explanatory of a Map and Section, 
he writes of these beds. “ The collections of fossils now obtained show 
most conclusively that it posesses the mixed character ofa fresh-water 
and estuary deposit, and that it cannot be older than the Miocene 
period.” = In the-published results of the Yellowstone and Missouri 
Expedition of 1859-60,$ we find the entire formation still retained 
in the Tertiary, but placed doubtfully on the horizon of the Eocene of 
Europe. The doubt seeming to obtain chiefly with regard to the pro- 
priety of its separation from the Miocene, and to be based on Dr. 
Newberry’s opinion on the plants. The comparison by Prof. Liedy of 
the animal remains with “types.even older than the Tertiary” is, 
however, mentioned. In 1868 Dr. Hayden still maintains the Tertiary 
age of the formation, and mentions especially the coal-bearing beds 
of the Laramie Plains, although in this locality, as he says, “ some 
marine fossils are found in strata connected with the coal.’’|| The 
admission is also made that there may here be ‘some thin seams 
of impure coal in the upper Cretaceous beds.” In 1870, Dr. Hayden 
refers to the Lower Eocene, the coal formation of the Green River and 
Bridger regions, but designates his classification of the beds there as 
‘* U.S. Geol. Surv. Territ., 1873, p. 107. 7 Description, New Species and Genera Fossils, &c. p. 19. 
t Notes Explanatory of a Map ‘and Section of the Country Borderirg on the Missouri River. p. 9. 
§ Geological Report Yellowstone and Missouri Expedition. p. 29, et seq. 
|| U. S, Geol. Surv. Territ,, 1867-69. p. 100. 


i; 
4 
