62 



LARAMIE FLORA OF THE DENVER BASIN. 



and "a greater number of the described in- 

 vertebrate species of the Laramie than any 

 other single locality." 



As much of the early history of opinion 

 regarding Black Buttes has been given on 

 pages 8-9, it is only necessary to refer to it 

 in the briefest manner at this point. As is 

 well known, Lesquereux from his studies of 

 the fossil plants argued strenuously for the 

 Tertiary age of the coal and plant bearing beds 

 at Black Buttes. Hayden also regarded these 

 beds as Tertiary, or, after the establishment 

 of the Laramie, as in a measure transitional 

 between Cretaceous and Tertiary. In 1872 

 Meek and Bannister visited this region and 

 discovered the remains of the dinosaur which 

 has played so prominent a part in the discus- 

 sion of the age of these beds. These dino- 

 saurian remains were described the same year 

 by Cope, who of course referred the beds con- 

 taining them without hesitation to the Cre- 

 taceous, us he and other vertebrate paleon- 

 tologists considered the mere presence of 

 dinosaurs as proof positive of Cretaceous age. 

 Meek, in discussing the age of the deposits at 

 Blacli Buttes ("Bitter Creek beds" of Powell), 

 was extremely cautious, his statement being 

 as follows : 



As we discovered in these rocks between three and four 

 times as many species of fossils as had been previously 

 known from the same, it becomes a matter of some interest 

 to consider the whole with regard to their bearing on the 

 question as to the age of the group. The reptilian remains 

 found at Black Butte, near the top of the series, have, as 

 elsewhere stated, been investigated by Prof. Cope and by 

 him pronounced to be decidedly dinosaurian and there- 

 fore indicative of Cretaceous age; on the other hand, the 

 fossil plants from the same beds have been studied by 

 Frof. Lesquereux, who informs me that they are unques- 

 tionable Tertiary types. My own investigations haying 

 been confined to' the invertebrates, it is of these chiefly 

 that I will speak here. In the first place, it will be seen 

 that all of these yet known belong to a few genera of mol- 

 luscs, represented by some twelve or fourteen species. 

 And just.here it may be stated that, although partly com- 

 mitted in favor of the opinion that this formation belongs 

 to the Cretaceous and still provisionally viewing it as 

 most probably such, I do not wish to disguise or conceal 

 the fact that the evidence favoring this conclusion, to be 

 derived from the mollusks alone, as now known, is by no 

 means strong or, com incing. The genera are probably all 

 common both to the Cretaceous and Tertiary as well as 

 to the present epoch. 



Meek finally concluded that " aside from the 

 dinosaurian, the organic remains favor the con- 

 clusion that it is Tertiary." Later, however 



(1876), he recorded his impression that the 

 "Bitter Creek series" and the underlying 

 "Point of Rocks series" should probably be 

 considered a unit and hence were presum- 

 ably Cretaceous, though again he was far from 

 positive in his opinion. 



In 1876 J. W. Powell published his "Report 

 on the. geology of the eastern portion of the 

 Uinta Mountains," which contains also a chap- 

 ter on -the paleontology by C. A. White. In 

 this report the "Bitter Creek group" was 

 placed unqualifiedly in the Tertiary and was 

 described as resting with marked angular un- 

 conformity on the underlying " Point of Rocks 

 group." In commenting on this King 20 wrote 

 as follows : 



Powell and White draw the line below the Halh ille and 

 Black Butte coals, lea^ ing these upper beds, including the 

 dinosaurian and leaf beds of Black Butte, in the Tertiary. 

 They describe a slight "nonconformity of erosion," pro- 

 ducing little irregularities in the upper surface of the bed 

 directly above the horizon of the Anomia and Odontobasis 

 in the lower strata near Point of Bocks. This,. h owe >er, 

 draws an arbitrary line between the groups of fossils of 

 close relationship, some of the identical forms occurring 

 in their upper Cretaceous appearing in their lower Tertiary 

 at Black Butte. Moreover, they disregard entirely the 

 e idence of the dinosaurian, which -would seem to be con- 

 clusive proof of Cretaceous age. We prefer to draw the 

 line at the top of Black Butte, including the dinosaurian 

 and plant beds in the Cretaceous, believing also that in 

 tracing the contact between the beds next over the dino- 

 saurian series and the ashy beds which o\ erlie them we 

 detect a slight unconformity, which, when traced north, 

 seems both more persistent and more observable than the 

 unconformity of erosion noted by Powell, which we, fail to 

 folhJw north. 



Later (1877) White placed the beds at Black 

 Buttes in the Laramie, which he then regarded 

 as of post-Cretaceous age, though ultimately 

 he of course came to consider it as. Cretaceous. 

 In 1886 Lester F. Ward published his "Synop-., 

 sis of the flora of the Laramie group," in which 

 the plant beds at Black Buttes were discussed 

 and a few plants were described. He was not 

 able to decide from the data he employed 

 whether the Laramie is Cretaceous or Tertiary, 

 though he inclined to the then prevailing 

 opinion that it is Cretaceous. 



In 1896 T. W. Stanton and 1 21 spent several 

 days in studying the section at Black Buttes 

 and in collecting plants and invertebrates. We 



» King, Clarence, Systematic geology: U. S. Geol. Expl. 40th Par. 

 Rept., vol. 1, p, 338, 1878. ' "> : ' 



» Stanton, T. W., and Knowlton, F. H., Stratigraphy and paleon- 

 tology of the Laramie and related formations in Wyoming: Geol. Soc. 

 America Bull., vol. 8, pp. 127-156, 1907. 



