484 E. T. DUMBLE 



This movement was marked in the Texas area by Pilot Knob 

 and other volcanoes south of Austin, which were active during the 

 close of the Chalk deposition and the beginning of the Taylor 

 marls, as is shown by the ash from them, which is interstratified 

 with, and included in, these deposits. 



At the close of the Cretaceous the movement was intensified 

 and resulted in a land barrier which is now marked by the discon- 

 nected ranges and groups of hills that form the eastern border of 

 the valley lying at the foot of the Mexican Cordilleras. 



These groups and ranges include the San Antonio, San Juan, 

 Vallecillo, Picachos, Papagallos, San Carlos, and Tamaulipas, for 

 which, as a whole. Professor Cummins has proposed the name of 

 the Tamaulipas range. Since the trend of the coast in this region 

 is a little west of south, the southeast course of this Tamaulipas 

 Range brings it rapidly nearer the Gulf. At Tordo Bay, some 

 fifty miles north of Tampico, the main body of the hills is within 

 ten miles of the coast, while outliers extend almost to the water's 

 edge. 



This range is made up of shales and limestones, more or less 

 altered and disturbed by folding and by igneous rocks. No 

 fossils have been found in the shales, but the limestones yielded 

 a few inocerami and fragments of Ammonites. Dr. Stanton, who 

 examined these, states that these limestones are not younger 

 than the Taylor marls and may not be younger than the Austin 

 Chalk. 



The Tamaulipas Range represents the extension southward 

 and culmination of the movement creating the Sabinas barrier, 

 and just as the Sabinas barrier forms the southern limit and border 

 of the Gulf Coast Cretaceous deposits, so does the Tamaulipas 

 Range form the southern border and limit of the Gulf Coast 

 Eocene. The difference in the character of deposits laid down in 

 late Cretaceous time to the north and south of the Sabinas barrier 

 is just as strongly shown in the difference between the Eocene 

 deposits east of the Tamaulipas Range and those of the same age 

 which are found to the west and south of it, since not only are the 

 deposits themselves of different character, but even the fossils 

 which the latter carry are entirely unlike those to the north. 



