230 E. T. DUMBLE — GEOLOGY OF THE RIO GRANDE. 



in it such fossils as Bulimus altematus, Say. and in showing that it is 

 stratigraphically higher than the Fayette sands. Dr. Penrose described 

 it in the first annual report of the geologic survey of Texas under the 

 name of the Reynosa limestone. The connection between this Reynosa 

 limestone and the tufaceous lime and gravel, however, was not recog- 

 nized until the past summer. Mr. J. A. Taff of the Texas survey, in his 

 examination along the line of the Texas-Mexican railway between 

 Corpus Christi and Laredo, observed the same lime and gravel with 

 Bulimus altematus overlying the Fayette sands at various places. I 

 joined his party in Cotulla, and during my work with them up the 

 valleys of the Nueces and henna rivers I found many exposures of the 

 gravel and lime and of the firmer limestone already described in such 

 connection as to prove conclusively that they are mere local variations 

 of one and the same deposit. I therefore extend the name Reynosa to 

 include the entire series of deposits for the present. These deposits 

 cover a very large area in western Texas and extend into Mexico. In 

 places the limestone reaches such thickness and hardness as to be used 

 as building material, as in the district south of Porferio Diaz, at Rey- 

 nosa, and elsewhere. As nearly as we have been able to ascertain, these 

 beds seem to be in part at least the equivalents of the Equus beds 

 described by Professors Cope and Leidy in southwestern Texas. They 

 appear to rest unconformably upon the underlying beds of Cretaceous, 

 Eocene and Neocene age. While the connection of the Reynosa beds 

 with the Lafayette formation toward the east has not been determined 

 by actually tracing one into the other, their similar stratigraphic position 

 above the Fayette sands and beneath the coastward clays of the Port 

 Hudson (Columbia formation of McGee) is strong evidence in favor of 

 their being different phases of the same formation. 



CORRELATION OF RIO GRANDE AND COLORADO RIVER SECTIONS. 



Rio Grande Section. Colorado Section. 



Neocene Reynosa beds Lafayette (?) 



Eocene Webb Bluff Tertiary Eocene 



( ( Escondido beds. . . . (Wanting i 



I Eagle Pass ! Coal scries (Wanting) 



rT ., division I San Miguel beds . ... Glauconitic beds 



1 PP er Cretaceous^ [ Upson days Ponderosa marls 



j Pinto limestone Austin limestone 



I. Val Verde flags Eagle Ford shales 



r ,, ( Vola limestone Vola limestone 



Lower ( retaceous j Jr/ . //;) „ dayg ^ ,,-,„ clayg 



