Vol. VIII] DUMBLE— GEOLOGY TAMPICO EMBAYMENT AREA 145 



On the Conchos River and along the eastern face of the 

 Pomeranes Mountains to the north of that stream the only 

 beds recognized were those belonging to the uppermost part 

 of the formation. To the southward in the Martines and San 

 Jose de las Rusias ranges to the vicinity of Tordo Bay lower 

 beds than those of the Conchos predominate. South of the 

 Tamaulipas Range in the Panuco River drainage area a con- 

 siderable part of the fossil-bearing deposits seem to be of this 

 same age, while south of the Otontopec divide we find, in con- 

 nection with these deposits toward the coast, a considerable de- 

 velopment of later beds similar to those on the Conchos. 



The San Rafael, as here described, includes both the Eogene 

 and Neogene of Villarello's report. Of the former, he says : 



"The Sierra San Jose de las Rusias is made up of yellowish 

 colored nummulitic calcareous rocks which belong to the 

 Eogene and which extend to the north as far as the vicinity 

 of Santa Maria de las Ovejas. To the west they extend to the 

 plain of San Jose. To the east they pass under the Quaternary 

 and Recent formations of the Coast, and south they reach as 



far as the same Sierra of San Jose These beds belong 



to the Eogene and form slight folds : sometimes cross-folding. 

 The general structure is monoclinal." (P. 12.) 



The overlying beds, or "Neogene," are made up in this vicin- 

 ity of argillaceous shales, while around Ebano the beds he cor- 

 relates with these are thus described : 



"The Tertiary of this region is made up of yellow clay shales 

 and blue or bluish gray marls. Interpolated in these marls and 

 shales are sandstones with a clay and sometimes calcareous 

 cementing material. These rocks outcrop chiefly, although to a 

 very small extent, toward the west from Ebano and some por- 

 tions of the plain where generally they are covered by the 

 Quaternary and Recent formations of the Gulf Coast." 



Jeffreys' section of the Tampico Tertiaries shows at the base 

 semi-crystalline fossiliferous limestone with some shales, also 

 a coarse crystalline limestone and the blue calcareous sandy 

 marl. This is overlain by a soft calcareous sandy material 

 interbedded with white nodular forms. The succeeding beds 

 consist of coarse limestone weathering to yellow and carrying 

 oysters. The top bed is of sandy turritella limestone with cal- 

 careous sandstone beds containing white nodular forms. 



