152 GEOLOGICAL SURVEY OF THE TERRITORIES. 



It will be seen, on referring to the column headed Lesquereux, that 

 beds of the Bitter Creek series are in part under Miocene, and in part 

 under Eocene. The reason of this may be that the specimens are from 

 different horizons, or, if from the same horizon, it would seem to prove 

 that there is a mingling of forms in the flora of Eocene and Miocene 

 formations. It is probable that when more complete collections are 

 made, this will be found to be the case. That the coal-beds of these 

 localities, however, belong to the same horizon is evidently the opinion 

 of Dr. Hayden and Prof. F. B. Meek, who have studied the localities 

 strati graphically. (See references in tables). 



LIGNITIC GROUP. 



West of the continental divide the coal-bearing strata are not con- 

 fined to the Lignitic group (as named east of the mountains). As noted 

 in the preceding chapter, I found lignite in the sandstones of the Dakota 

 group. In 1873 Mr. Marvine* found a "thin seam of coal" "a few 

 hundred feet above the quartzitic sandstones of No. I, 7 ' at the "Hot 

 Springs" in Middle Park. During the season of 1874 Mr. Marvine 

 found coal in a horizon above fossils of No. 4 and below those referable 

 to No. 5. Dr. Endlich, in his district, recognized three distinct lignitic 

 layers in different horizons of the Cretaceous formation. The coal of 

 the Elk Mountains is probably of the age of the Fox Hills group. I 

 have already referred to the possibility of the upper part of the series 

 there, in which the coal is found, being apart of the Lignitic group, but, 

 until fossils are found, I refer it to Upper Cretaceous. 



Professor Newberry t found lignite in Lower Cretaceous and in Jurassic 

 strata in Northeastern Arizona. In Minnesota, also, coal has been found 

 in Lower Cretaceous rocks. 



The reason of the differences of opinion as to the age of the disputed 

 beds called lignitic seems to be that there are two sets of lignite- bearing 

 beds close together, one belonging to the horizon of the Fox Hills beds 

 of the Cretaceous or possibly a little above it, and the other belonging 

 to the horizon of the Fort Union group (Lower Eocene). As Prof. G. 

 M. Dawson:j: says, "An observer beginning his study of the beds on 

 their eastern margin, and proceeding westward, as Dr. Hayden has 

 done, would be completely justified in placing the whole series, at least 

 down to the top of Cretaceous No. 5, in the Tertiary; while a geologist 

 familiar in the first instance with the fossils of the underlying Cretaceous 

 formations, and following the lignite strata eastward from their appear- 

 ance in the Rocky Mountains, would in all probability include the whole 

 series in the upward extension of the Cretaceous, though doubts might 

 begin to assail him before he reached the upper or most eastern beds." 



In many places the coal of the upper part of the Cretaceous appears 

 to be absent. When present the sandstones have a transitional char- 

 acter, but this is also noticed where coal is found in the lower part of 

 the Cretaceous formation, and in the Jurassic, just beneath. Professor 

 Cope refers the lignite-beds to the Cretaceous formation from the dis- 

 covery of the reptilian fauna in them. He has described a Dinosaurian 

 reptile from the Bitter Creek series,§ and also from the Fort Union 

 group in Colorado.|| Professor Meek<jj says, "Aside from the Dino- 



' * Report of U. S. Geol. Survey, 1873, page 156. 



t Colorado Exploring Expedition, Geological Report, pp. 83, 85. 



X Geological Report on the Region in the Vicinity of the Forty-ninth Parallel, p. 202. 



§ Proceedings of the American Philosophical Society, 1872, p. 482. 



|| Report United States Geological Survey of the Territories, 1873, p. 444. 

 11 Report United States Geological Survey, 1872, p. 461. 



