PALEOBOTANICAL EVIDENCE 333 



known to be common to the Eaton and Wilcox formations, and when Mr. 

 Berry's work is available it will be found that there are probably not less 

 than 50 common or closely related species. Mr. Berry is of the opinion 

 that the Wilcox may be slightly younger than the Eaton, and it may be 

 that it is the equivalent of the upper part or perhaps the whole of the 

 Midway, as well as a portion of the Wilcox. 



This correlation of the Eaton formation with the Wilcox and Midway 

 is important, since it ties the Eocky Mountain section with the marine 

 section of the Gulf, where the geologic relations are definitely known. 

 This correlation was first pointed out by Lesquereux more than 40 years 

 ago, when he had at his disposal only a handful of specimens from either 

 area, and it is a pleasure to attest its correctness, which is not changed, 

 with the fullest collections ever brought together for any Eocky Moun- 

 tain area. 



The Eaton formation, as already indicated, contains a flora of 148 

 species, only four of which are known to occur in the Vermejo formation 

 immediately below. This flora is especially characterized by vast num- 

 bers of palms, some with leaves 6 or 8 feet in diameter, and is rich in 

 figs, cinnamons, magnolias, bread-fruit trees, etcetera, and indicates a 

 moist, warm, possibly subtropical climate. The Eatoji formation is cor- 

 related by its flora, as well as by its stratigraphic relations, with the 

 Denver formation of the Denver basin. The latter— the Denver — has a 

 published flora of 98 species, over 40 per cent of which are common to 

 the Eaton, and there is a large mass of unworked material, which when 

 elaborated will undoubtedly increase the number of species common to 

 these two formations. 



The Arapahoe formation has a flora of 32 species, nearly all of which 

 have been found also in the Denver. The flora certainly lends support to 

 the view that they are not greatly different. 



On the south and southeast of the Denver basin is the area occupied by 

 the Dawson arkose, which, as already stated, is believed to be strati- 

 graphically continuous with the Denver and Arapahoe formations, the 

 difference between them being largely lithological, the Denver being ande- 

 sitic and the Dawson arkosic. The flora of the Dawson numbers between 

 30 and 40 species, nearly all of which are typical and well known Denver 

 species. There can be no doubt, therefore, that the two are of the same 

 age. The correlation of the Denver and the Eaton is also well attested 

 by the flora. 



The plant-bearing beds in North Park, Colorado, may next be consid- 

 ered. There is very little topographic relief within this area, with the 

 result that exposures of the strata are few and usually poor. The ooal- 



XXIV — Bull. Geol. Soc. Am., Vol. 25, 1913 



