506 INDEX TO THE STRATIGEAPHY OF NOETH AMERICA. 



the widespread granitic intrusions of the area occur farther east in the vicinity of Poloma and 

 Los Alamos valleys, in Riverside County. 



I 13-14. EASTERN NEW MEXICO AND WESTERN TEXAS. 



The Triassic of eastern New Mexico occurs in the escarpment along the valley 

 of Canadian River, and prob-ibly elsewhere as the uppermost part of the red beds 

 beneath strata which are believed to represent the Morrison formation (Jurassic or 

 Cretaceous). The strata a,re 100 to 200 feet thick and are sandstones of reddish 

 color with lighter-colored balls of clay." Triassic vertebrate remains have been 

 found by Stanton ''^^^ near Folsom and by Lee *^^ at a point southeast of 

 Tucumcari. 



The original section of Mount Tucumcari ("Pyramid Mountain") was observed 

 by Marcou and is thus described by Blake : *^ 



Pyramid Mountain. — The finest and most complete section of the horizontal strata of the 

 bluffs along the route was obtained at this mountain by Mr. Marcou. The point was peculiarly 

 favorable, being one of the isolated mounds, a remnant of the Llano, and exposing the strata on 

 all sides. It is only one of the many mounds dotted over the wide space eroded by the river 

 from the Llano, and called Plaza Larga by the Mexicans. This mound was ascended by Mr. 

 Marcou, and others of the party, and we find the following record of the succession of the strata 

 in the notes under date of September 22 : 



Section at Pyramid Mountain. 

 "Jurassic:" 



White limestone. 



Yellow limestone witli bluish-gray bed at ttie bottom. 



Bed containing Ostrea (?).& 



White sandstone. 



Yellow sandstone. 



White sandstone. 

 "Triassic:" 



Gray and green bed in contact with the superior Trias. 



Red and green sandstone. 



White marls with concretions. 



Red and green marls. 



White. 



Red. 

 [Thickness,] 500 feet. 



Mr. Marcou considers that the base of this mound is formed of the beds of the superior 

 Trias, the upper portion being Jurassic. It does not appear to me that the evidences are quite 

 sufl&cient to warrant this decision, but the discussion of this subject wiU be left for a subsequent 

 portion of the report. 



A sketch of this mound was carefuUy taken in colors by Mr. Mollhausen, tha tints agreeing 

 as nearly as possible with those presented by the strata. The sketch has been lithographed 

 and is appended. It wiU serve to convey an idea of the relations of the strata, especially the 

 white and red series, and may be received as an exhibit of the general aspect of the bluffs of 

 the Llano, where the beds are exposed. The section and locality derives great interest from 

 the occurrence of fossils. The bed containing the Ostrea is said to be of grayish-blue clay and 

 subschistose, and 2 inches thick. The Ostrea is subsequently called Ostrea dilatata, and is 

 again mentioned in the rfeume. ' This is the fossil called Gryphsea tucumcarii in the collection 

 (No. 133) from Pjrramid Mountain, and referred to in the r6sum6 under the same name, it 



"■ Lee, W. T., personal communication. 



& The specific name can not be deciphered in the original. It looks like comanche. — W. P. B. 



