428 C. R. Keyes — Triassic System in New Mexico. 



times, or possibly in both, the Paleozoic formations and Tri- 

 assic beds were bowed np, somewhat folded and faulted and 

 then eroded off as a land surface. When Mid-Cretaceous 

 (basal part of "Upper") beds were laid down, they were 

 deposited largely on this old land surface worn out on the 

 bevelled edges of the older formations. 



In the east there are shown marked unconformable relation- 

 ships not only between the Cimarron Red Beds and the Tri- 

 assic Red Beds, but between the latter and the Comanche series, 

 between the last mentioned and the Dakota sandstone series, 

 and between all of these and the Tertiary formations. 



In central New Mexico, the Dakota series rests directly on 

 the Madera limestones of the Carboniferous. The Red Beds 

 of both the Cimarron series and the series of the Triassic have 

 been entirely removed through Early Cretaceous erosion. The 

 Comanche series, which had been constantly encroaching upon 

 the old land area from the beginning to the end of its period 

 of deposition, did not reach this far. In consequence the Mid- 

 Cretaceous sandstones (Dakota) were deposited directly upon 

 the Carboniferous limestones (Madera). 



In the west the sequence was very much as it was in the 

 east, except that the Early Cretaceous appears to be entirely 

 missing, the Triassic section very much thicker, and the Cim- 

 arron section very much reduced. 



It is a singular fact that the tripartite character of the Tri- 

 assic sections in the west has a triple counterpart in the east. 

 No direct connection between the two sections has been actu- 

 ally traced in this field, for in central New Mexico a wide 

 gap exists. 



Comparing the eastern section with the sections of the 

 adjoining portions of Texas, this agreement is very close. The 

 entire Triassic section is there called the Dockum beds. As 

 already stated, it is not believed that any portion of the Red 

 Beds of Kansas are represented by the Triassic formations of 

 New Mexico. 



In the Zuni uplift, where the Triassic beds are so well dis- 

 played, they come up from beneath the vast field of Cretaceous 

 sandstones. The sequence between the so-called Permian Red 

 Beds and the Dakota sandstones of the Cretaceous is very thick. 

 The data upon which the geological age has been determined 

 have been already given. Dutton, who a quarter of a century 

 ago had perhaps given the subject more attention than anyone 

 else, was unable to satisfactorily separate the two parts. He 

 says that the " Triassic system of New Mexico cannot be corre- 

 lated so easily with its cognate beds in southern Utah and the 

 Grand Canyon district as the Carboniferous and Permian. In 

 the former region it has yielded but few fossils, while in the 



