452 abstracts: geology 



The lower formation, to which the name Verme jo is here apphed, con- 

 tains a Montana flora. It is distinct from the Laramie flora of the 

 Denver Basin, and proves that the Verme jo formation is older than 

 Laramie, and that it is more closely related to the Mesaverde of west- 

 ern New Mexico than to any other formation yet examined. 



The coal-bearing rocks of the Canon City field are correlated by 

 lithology, stratigraphic position, and fossil plants with the Vermejo of 

 the Raton Mesa region and are designated by the same name. The 

 character of the invertebrates found in the Vermejo of the Canon City 

 field in the midst of the plant-bearing beds suggests that this formation 

 is approximately equivalent in age to the Fox Hills of the Denver Basin. 



The upper formation of the Raton Mesa region, to which the name 

 Raton is here applied, is Eocene in age and contains a flora distinct 

 from that of the Laramie of the Denver Basin but similar to that of 

 the post-Laramie formations of that basin and to that of the Eocene 

 Wilcox group of the Gulf Coast. 



The unconformity between the Vermejo and Raton formations rep- 

 resents a time interval comparable to that described as separating the 

 Laramie from the Arapahoe of the Denver Basin. Separating, as it 

 does, the youngest Cretaceous of the region from the oldest Eocene, 

 it represents post-Cretaceous erosion and is correlated with the post- 

 Laramie unconformity of the Denver Basin. 



Lee's discussion of the geology of Raton Mesa is followed by Knowl- 

 ton's description of the fossil flora of the Vermejo and Raton forma- 

 tions. The flora is abundantly figured and some of the illustrations 

 are exceptionally large. That the age of the Vermejo formation is 

 Cretaceous is established by its stratigraphic position, its invertebrate 

 fossils, and especially by its plants, which correlate it with the Montana 

 in the approximate position of the Mesaverde formation. The Vermejo 

 is terminated by an unconformity, and so far as is at present known 

 only 4 of the 108 Vermejo species pass over the unconformity and are 

 fovmd in the Raton formation. 



The Raton formation is to be correlated with the Wilcox, and prob- 

 ably with the Midway formation of the Gulf region. The Tertiary 

 age of the Midway and Wilcox formations is not questioned. On the 

 basis of the plants the Raton formation is also correlated with the 

 Arapahoe and the Denver formations of the Denver Basin; and the 

 latter is now known to be correlated with, and in fact to be practically 

 continuous with, the Dawson arkose. The conclusion is reached that 

 all these formations are Tertiary (Eocene) in age. 



R. W. Stone. 



