32 



LARAMIE FLORA OF THE DENVER BASIN. 



relations of the ' Ceratops beds' of Wyoming 

 and Montana." The thesis of this paper was 

 stated as follows: 



The purpose of the present paper is to show that some 

 of the data already used in the discussion [by Knowlton, 

 Cross, and others] are capable of a different interpretation 

 and to call attention to some additional facts which 

 ought to be fully considered before a final verdict is 

 reached. All are agreed that the strata in question are 

 near the boundary between Cretaceous and Tertiary. 

 My opinion is that the greater weight of evidence places 

 them on the Cretaceous. side. 



Under the head of "local stratigraphy and 

 paleontology" Stanton reviewed a number of 

 the areas in Wyoming and Montana con- 

 sidered in my paper and set forth his own 

 field observations and interpretation of the 

 stratigraphic and paleontologic conditions. In 

 summarizing these data Stanton said : 



It has been shown that, within the large area considered, 

 the " Geratops beds" with the Triceratops fauna are always 

 pretty closely associated with the uppermost Cretaceous 

 strata or are separated from them by transitional brackish- 

 water beds. They are always overlain by a thick series 

 of rocks containing a Port Union flora in which no dino- 

 saurian remains have been found, and in the Pish Creek, 

 Mont., region this overlying series also contains primitive 

 mammals related to those of the Puerco and Torrejon 

 faunas. Throughout a large part of the area no evidence 

 of an unconformity beneath the " Ceratops beds" has been 

 found; while higher in the section unconformities have 

 been demonstrated or suggested at a number of places. 

 Unconformities have been reported below the " Ceratops 

 beds" on Hell Creek, Mont., on the Little Missouri, in 

 North Dakota, and in Weston County, Wyo., but in none 

 of these cases has any proof been furnished that the erosion 

 interval is important. 



The conclusions reached in this paper are 

 given as follows: 



In the interior region of North' America the formations 

 between the uppermost marine Cretaceous and the 

 Wasatch together constitute a real transition from the 

 Cretaceous to the Teritary. 



Notwithstanding the fact that there are several local 

 unconformities at various horizons and perhaps some of 

 more general distribution, there is no conclusive evidence 

 that any one of these represents a very long period of 

 erosion not represented by sediments elsewhere in the 

 region. 



The Fort Union formation, properly restricted, is of 

 early Eocene age, the determination resting chiefly on its 

 stratigraphic position and its primitive mammalian 

 fauna, which is related to the earliest Eocene fauna of 

 Europe. The very modern character of the flora tends 

 to confirm this correlation. 



The " Ceratops beds" are of Cretaceous age as decided 

 by stratigraphic relations, by the pronounced Mesozoic 



character of the vertebrate fauna with absence of all 

 Tertiary types, and by the close relations of the inverte- 

 brate fauna with the Cretaceous. The relation of the 

 flora with Eocene floras is believed to be less important 

 than this faunal and stratigraphic evidence. Taken in 

 their whole areal extent, they probably include equiva- 

 lents of the Laramie, Arapahoe, and Denver formations 

 of the Denver Basin. 



Hay' 10 also published a paper in 1909 on the 

 position and age of the "Ceratops beds," in 

 which, after comparing the fauna of these beds 

 with those of the Judith Kiver, Puerco, Torre- 

 jon, and several European formations, he con- 

 cluded as follows: 



1. The answer that the writer would give to the ques- 

 tion at the head of this paper is that the Lance Creek 

 beds belong to the Upper Cretaceous. 



2. In the Upper Cretaceous ought to be included also 

 the Puerco and not improbably also the Torrejon and 

 Fort Union. 



3. In case of a conflict between the evidence furnished 

 by the flora and the fauna of the Lance Creek beds and 

 .those of the Fort Union respectively, the evidence ob- 

 tained from the fauna is to be preferred, as being part of 

 a more complete and better understood history. Present 

 knowledge regarding plants seems to indicate that they 

 were precocious, having reached something like their 

 present stage of development long before mammals at- 

 tained anything like their present stages of differentia- 

 tion. There are also indications that the floras of the 

 western world were, during the Cretaceous, considerably 

 in advance of those of Europe. 



4. Even if it were concluded that the Fort Union be- 

 longs to the Tertiary, and that the fauna and flora of the 

 Lance Creek epoch are more closely related to those of 

 the Fort Union than they are to those of the Judith River, 

 it does not follow that the Lance Creek epoch must be 

 included in the Tertiary. A quarter before midnight on 

 Monday is much nearer to Tuesday than it is to the pre- 

 vious 6 o'clock; nevertheless, it is not yet Tuesday. 



The work of the United States Geological 

 Survey in classifying the coal lands was 

 continued in 1908, though the results of this 

 year's investigations were not published until 

 1910. 11 It is noteworthy that in the areas 

 falling within the scope of the present review 

 the Fort Union has come to be placed un- 

 qualifiedly in the Tertiary. 



In the volume cited R. W. Eichards has a 

 paper under the title "The central part of the 

 Bull Mountain coal field, Mont.," in which 

 the stratigraphic relations are set forth in the 

 following table: 



10 Hay, O. P., Where do the Lance Creek (" Ceratops") beds belong- 

 in the Cretaceous or in the Tertiary?: Indiana Acad. Sci. Proc, vol. 

 25, 1909. J| 



11 TJ. S. Geol. Survey Bull. 381, 1910. 



