Vol. VIII] DUMBLE-GEOLOGY TAMPICO EMBAYMENT AREA 129 



At the greater number of places where shales were ob- 

 served north of the railroad they have a considerable dip to 

 the north or west. The principal exceptions to this are cer- 

 tain hills lying around Victoria and Cruz, which, while com- 

 posed of similar materials, are horizontally bedded. This 

 apparent discordance of stratification may indicate that these 

 hills are not Papagallos but outliers of the Eocene sedimen- 

 tation occurring south of the Panuco River. 



No fossils have been reported from the Papagallos shales 

 but they are thought to contain foraminiferal remains and 

 should have microscopic study. 



In the Aquismon region south of the railroad line Villa- 

 rello classes all of the materials lying between the Tamasopa 

 and Quaternary as Neo-Cretaceous, which classification 

 would~ include both San Juan and Papagallos, and says of 

 them : 



"Unconformably upon the Meso-Cretaceous lie shales and 

 marls and sometimes slates between which are interpolated 

 limestones and sandstones cemented with calcareous material. 



All these beds belong to the Neo-Cretaceous and 



outcrop over a great extent of country. 



"The Neo-Cretaceous outcrops on the north of Xilitla from 

 the Huichihuayan Hacienda through the Tierras Coloradas, 

 Tocamon, Huihuitlan, Tampamolon, Tancanhuitz, Aquismon 

 and Tanquin to Valles. It extends on the west as far as the 

 base of the Temapache and Colmena mountains and east- 

 ward as far as the Tanchipa or Boca del Abra mountains. 



"The Neo-Cretaceous shales have a strike varying from 

 North 25° E. to N.E. with dips of 10 to 20° to the west of 

 northwest. These shales are slightly folded and sometimes 

 form cross folds, the arches of which are little raised and of 

 very gentle slope. 



"At Huihuitlan and Tierras Coloradas sheets of coal 5 cm. 

 thick are found interpolated with the beds of sands and 

 shales."' 



While some of the deposits of the Aquismon district are 

 Neo-Cretaceous, they cannot all be so referred. Jefifreys re- 

 fers the beds east of Aquismon, which he described as his 

 Tanalajas formation, to the upper Tertiary on the evidence 



