Vol. VIII] DUMBLE— GEOLOGY TAMPICO EMBAYMENT AREA 123 



mon, and Micos and in the Colmena or Abra de Cabelleros 

 mountains. To the east of these outcroppings and to the east 

 of Valles the Meso-Cretaceous outcrops from the Rancho 

 Nuevo and fraction of the Pujal on the Tampaon River to Abra 

 and Las Palmas stations on the Mexican Central Raih'oad and 

 from there extends to Tanchipa Mountains. In this range the 

 Meso-Cretaceous hmestones are covered in various places by 

 shales and marls of Neo-Cretaceous age which come in between 

 Valles and Abra 



"The Meso-Cretaceous is highly folded forming anti- 

 clines and synclines sometimes very close and in general un- 

 symmetrical." 



Jeffreys describes a section in the San Dieguito Range in this 

 region as showing at the base four feet of a dolomitized lime- 

 stone with minute particles of petroleum, overlain by three feet 

 of gray crystalline limestone which had a distinct petroliferous 

 odor, while the overlying bed of about one foot thickness is a 

 dark gray to almost black limestone well saturated with oil. 

 The limestone is more or less fossiliferous throughout, hippu- 

 rites and various lamellibranchs seeming to predominate. 



Similar impregnations are found in heavily bedded and 

 folded Tamasopa limestone on the eastern slopes of the Tema- 

 pache mountains. 



The Tamasopa limestone has been subjected to heavy fold- 

 ing which has formed anticlines and synclines sometimes very 

 close and, in general, unsymmetrical, and strikes vary from 30 

 to 60 deg. N. of E. in the region along the railway. 



Except the statement that the Meso-Cretaceous limestone 

 forms the main body of the Sierra Madre toward the south, 

 there is almost nothing said about it in the region between 

 Aquismon and Orizaba. 



Cummins, in his work between the Panuco and Tuxpam 

 rivers, did not get far enough west to reach the Tamasopa lime- 

 stone and saw no exposures of limestones similar to the San 

 Juan. The most westerly exposures he observed were of ma- 

 terials which he believed to be Tertiary. 



De Golyer, in writing of the Tamasopa south of Tuxpam, 

 says that the main mass of the outcrop is in the Sierra Madres, 

 the front range of which passes 28 miles west and 16 miles 

 south of the Furbero field. The Tamasopa limestone has not 

 been reached in any well yet drilled in this field. 



