648 



INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



G-H 13-14. COAHTJILA AND ZACATECAS, MEXICO. 



The Upper Cretaceous of northeastern Mexico contains important coal meas- 

 ures. The stratigraphy and structure of the State of Coahuila have been described 

 by Aguilera/" who tabulates the stratigraphy as follows : 



Tn describing the strata Aguilera says: 



The sedimentary rocks are marly sandstones, of bluish and reddish colors, and also lime- 

 stones of various tones of gray, including argdlaceous shales that are gray and black in the 

 upper part and bluish in the lower part of the entire mass of the formation. The sandstones 

 are in general of fine grain. There is a bed, varying in thickness from 5 to 30 meters, which 



consists of conglomerate of large limestone pebbles. 



** *** * * ** 



Throughout the broad region in which the coal-bearing strata of the Cretaceous are devel- 

 oped in Coahuila, one may distinguish the following divisions: At the base the Barroteran, 

 and then, following in succession upward, the Esperanzas formation comprising the fossdif- 

 erous beds of Esperanzas, Muzquiz, and other places upon the slopes of the mountains; the 

 Sabinas, consisting of the glauconitic sandstones of the village of Sabinas, and topped by the 

 shales which contain a bed of Ostrea cortex; the Arroyo Tulillo for the beds of Ostrea glabra 

 Meek. To these may be added the Peyotes division with beds containing Inoceramus labiatus 

 Schlotheim, etc. 



Burckhardt "** has classified and described the Jurassic and Cretaceous of the 

 Sierra de Mazapil district, in the States of Zacatecas and Coahuila, in the "Mesa 

 Central" of Mexico. (See table in Chapter XIII, pp. 552-553.) 



