588 



INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



Bose's description includes lists of fossils and a study of the relations of the 

 Cretaceous of Orizaba with that of Texas and northern Mexico and that of Europe. 

 His correlation table is translated as follows: 



Bose's paper has been reviewed by Stanton/^" who has also contributed th& 

 following notes in regard to the relations of the limestones in the vicinity of Orizaba : 



The faunas of the two limestones indicate correlation with the Comanche series, and the 

 underlying slates, though unfossiliferous, are correlated by lithology and stratigraphic position, 

 with the Lower Cretaceous of Zapotitlan, in Puebla. 



The section at Zapotitlan and San Juan Raya has been described by Aguilera (Guide 

 gfiologique au Mexique) , who states that the Escamela and Maltrata limestones, which he refers- 

 to the Cenomanian, are represented here by a single unfossiliferous limestone called the Cipiapa. 

 division. The underlying Eo-Cretaceous includes the San Juan Raya and Zapotitlan divisions, 

 which together are correlated by their faunas with the European Lower Cretaceous horizon from, 

 the upper Barremian to the Aptien, inclusive. 



E 15. ISTHMUS OP TEHnJANTEPEC. 



Bose published for the Tenth International Congress an account of the geology 

 of the Isthmus of Tehuantepec. He said in part: ^"^ 



Before commencing the description of the excursion in the isthmus, we will summarily 

 describe the geology of the terranes which extend from east to west in this region. West of the 

 isthmus there is the mountain chain of Mexico, and on the left the chain of Central America. 

 The former consists of the following formations: At the base there is a series of gneisses and 

 mica schists, with ancient diorites and granites. Upon these rocks there rests in general the 

 Cretaceous, but there are also islands of Rhsetic, Liassic, and Upper Jurassic. The series is- 

 rarely complete, and the Paleozoic is always absent. The Cretaceous is composed of the lower 

 and middle Cretaceous and covers probably the larger part of the country. In the north [of 

 Mexico as a whole] these are supplemented by the upper Cretaceous. 



From this distribution of the Cretaceous Bose infers an early elevation of 

 southern Mexico, to which he attributes the absence of marine Tertiary in the 

 high plateaus, and he says further : 



In the plateaus we encountered deposits from extensive lakes which belong in part to the 

 Eocene ,and Miocene, the Pliocene, or Quaternary. Their age has been determined in many 



