Vol, VIII] DUMBLE— GEOLOGY TAMPICO EMBAYMENT AREA 121 



tween Aquismon and Chiapas, the greater part of the San Juan 

 and Papagallos which constitute the Neo-Cretaceous of the 

 northern basin are either overlapped or replaced by these 

 Eocene-Tertiary beds, outcrops of which extend eastward 

 almost to the margin of the Gulf. 



The Coastal Slope lying east of this disturbed or foothill 

 zone is largely occupied by deposits of Oligocene age as far 

 north as the Tamaulipas Mountains and these Oligocene de- 

 posits extend along the eastern face of this range as far as the 

 Conchos River. The only other sedimentary deposits noted are 

 deposits of the Quaternary and Recent which are not very ex- 

 tensive. 



Basalts and other rocks of igneous origin occur as intrusive 

 peaks, dikes, and flows. 



Cretaceous 



The Mexican geologists have divided the Cretaceous, of 

 which they have a very complete section, into Eo-Cretaceous, 

 Meso-Cretaceous and Neo-Cretaceous in place of the two di- 

 visions. Lower Cretaceous and Upper Cretaceous, recognized 

 in the United States. 



The Meso-Cretaceous of the Mexican authors includes the 

 upper portion of our Lower Cretaceous and the lower portion 

 of our Upper Cretaceous. 



It will appear from a comparison of the fossils that the line 

 between our Lower and Upper Cretaceous — that is, between 

 the Vola or Buda limestone and the Woodbine or Dakota sands 

 — would be represented in the Meso-Cretaceous by a line drawn 

 below the Tamasopa limestone. 



While, therefore, the heavy limestones below the Tamasopa 

 may be properly correlated with our Comanche, it would not 

 seem allowable to include the Tamasopa in such reference. 



MESO-CRETACEOUS 



The Meso-Cretaceous limestones of the Tamasopa gorge, as 

 described by Bose", are considered by him to represent the 

 Cenomanian, Turonian, and possibly the Vraconian, but the 

 Tamasopa limestone of the various reports on this region, as 



" Guide Book Geological Congress. XXX, p. 10. 



