Vol. VIII] DUMBLE-GEOLOGY TAMPICO EMBAYMENT AREA 147 



The comparatively superficial character of these beds is well 

 shown in the Topila district. Here the Topila Hills, several 

 hundred feet high, seemingly show a section of more than 1000 

 feet of clays with interbedded sandstones and limestones carry- 

 ing fossils of San Rafael age, and yet wells drilled along their 

 western foot show none of them. 



In places these beds are very fossiliferous and based on the 

 fossil fauna they may be divided into three stages, although 

 possibly the two lower may be ultimately combined into one. 

 These, beginning with the lowest, will be called the Meson, San 

 Rafael and Tuxpam stages. 



Meson 



The type locality of the Meson beds is in the valleys lying 

 between Moralillo and Meson on the trail leading from Tamia- 

 hua to Alazan. These beds consist for the most part of yellow 

 sandy clays with some lime and sandstone. It is characterized 

 by the large foraminifer Orbit oides papyracece, Bou. These 

 fossils occur here in great number, but they have not been ob- 

 served higher in the series. These beds, with their characteristic 

 fossils, are also found near San Jose in the San Jose de las 

 Rusias region underlying the San Rafael. 



San Rafael 



The San Rafael, from which these beds are named, is located 

 on Zarzizal Creek, 65 miles north of Tampico. Four miles east 

 of the town a range of hills 300 to 400 feet high is composed 

 of beds of yellow clay alternating with bands of clayey lime- 

 stones^^ The fossils are abundant and include corals, moUusca, 

 echinoderms and foraminifera. The corals, echinoderms and 

 forams are quite distinctive and through them the beds of this 

 stage are easily distinguished for a considerable distance to the 

 north and south of the type locality. 



While considerable stress seems to be placed on the limestones 

 of this division, they are not the predominant materials, which 

 consist of gray, blue, and yellow clays, shales, and marls, with 

 occasional beds of sandstone. The limestones are more or less 

 local in thei r development. 



" Tertiary Deposits of Northeastern Mexico, Gal. Ac. Sc. Vol. 5, No. 6, p. 189. 



