186 B. N. A. BOUNDARY COMMISSION. 
Uinta Mountains in Utah,* and the Placiére coals of New Mexico, des- 
eribed by Prof. Newberry, which are considered as Tertiary by Prof. 
Lesquereux, and have been stated to be so by Dr. Hayden.t With these 
exceptions, therefore, and leaving out of consideration a few localities in 
Utah and elsewhere, with regard to which there may still remain some 
slight doubt; the age of the whole of the valuable lignite deposits of the 
West depends on that assigned to the series of beds immediately over- 
lying Cretaceous No. 5, with which they are associated. 
438. The Tertiary age of the eastern representatives of these beds, 
in their typical localities, has never been directly questioned. It is 
only if the Lignite formation of the eastern base of the mountains be 
referred to the Cretaceous, that it becomes necessary, from the homo- 
geneity of the group, to consider these beds Cretaceous also. Prof. 
Newberry, however, has throughout maintained that these beds are 
Miocene, t while Prof. Meek more than hints at their ultimate inclusion 
in the Cretaceous, § and Prof. Cope now definitely classes them as 
Cretaceous; the two latter gentlemen arguing from the western beds 
eastward, in the manner above indicated. There seems little doubt, 
however, that the general tenor of the evidence of these beds, when 
considered alone, favours their Lower Eocene age. Their exact synchro- 
nism with the European Kocene is a question apart from the present 
inquiry. ) 
439. It is in the western extension of the beds of the Lignite formation, 
in the Rocky Mountain region,—where, though preserving the same 
entire conformity with the underlying well-marked Cretaceous, and non- 
conformity with the later Tertiary beds above them,—they have assumed 
preponderating salt and brackish-water characters; that the dispute 
with regard to their age has been closest, and the arguments on either 
side most equally balanced. The shells of marine and brackish-water 
type, instead of occurring merely in the lowest layers, here characterize 
a great thickness of the strata. At Hallville, in Utah, 3,000 to 4,000 
feet of coal-bearing beds were laid down before the sea waters were 
finally excluded. || Yet the tendency of the evidence seems to point 
to the necessary inclusion of these coals of Utah, in whatever series 
those of Colorado are ultimately placed, though Mr. Marvine appears 

*See Cope. U.S. Geol. Surv. Territ., 1873, p. 433, Prof. Dana in the last edition of hls Manual of 
Geology refers to those beds as belonging to the disputed Lignite formation, 
+t U. 8. Geol Surv. Territ., 1859. Am. Journ, Sci. and Arts, June, 1874. 
} Geological Report Yellowstone and Missouri Expedition, 1869. Am. Journ. Sci. and Arts, April, 1874. 
§ U. 8. Geol, Surv. Territ., 1872, p. 460, || Hayden, U. 8. Geol. Surv. Territ., 1870, p. 166. 
»* 
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