452 E. T. 1)1 MBLE PROBLEM OF TEXAS TERTIARY SANDS 



Duinble's collections from the sands in the jSTueces Eiver section, em- 

 i)racing five localities near Lipan Creek, below Campbellton, yielded: 



Ostrca ulahamicnsiH var. contracta Corhula aldrichi 



Modiola texana Corhula sp. a 



Vcncricnrdia planicosta HiateUa sp. 



Ci/thcrca hastropensis Turritella nasuta 



Cythcrca sp. a • I'scudoliva vctusta 



TclUnn scandula ConiuUna armigera 



Mactra sp. Terehra houstonia 



Corhula alabaniiensis Levifusus traheatoides 



Harris, on the basis of these collections, referred these sands to the 

 Lower Claiborne. 



The Frio furnished very few fossils, and those gave no hint of any 

 later age than that of the Lower Claiborne. 



Overlying these Frio clays was an extensive body of sandstones, to 

 which the name Oakville^^ was given. On tracing, these appeared to be 

 the same sands that occur at Eio Grande City and in La Grange Bluff. 

 Vertebrate fossils found at various places determined their age as Loup 

 Fork Miocene. 



Overlying the Miocene Oakville sands on the Nueces we found another 

 series of similar sands with vertebrate fossils. These were determined 

 by Cope as Pliocene and as of the same horizon as the Blanco beds of the 

 Staked Plains region. These were called Lapara. These were followed 

 by greenish gray clays which carried Plioc-ene fossils, but were later than 

 the Lapara. These were called the Lagarto. 



The name Fayette sands was then restricted to those sands and clays 

 of the original typical sections, which, with their light colors, sulphur 

 coatings, quartzite bands, petrified and opalized wood, were most promi- 

 nent in the earlier descriptions of Penrose and which had become most 

 closely associated with this name in the minds of those working on the 

 Texas Survey. 



We have, therefore, in southwest Texas three sands which, while similar 

 in character, are clearly differentiated by their fossils as Eocene, Miocene, 

 and Pliocene in age. 



Where we find the Oakville sands overlapping and resting upon the 

 Fayette, or find the Lapara in direct contact with the Oakville, as is 

 often the case, it is sometimes difficult, because of their similarity, to 

 separate them, unless fossils are present, and such conditions may inter- 

 fere with their being accurately mapped as separate fonnations. 



The typical sands at Grand Gulf, to which Wailes' name of Grand Gulf 



^ Journal of Geologj% 1894, p. 552 et seq. 



