494 ''- '/'• />/'/ />/■/'- 



Claiborne sediments in other regions and appears not to have 

 greatly alTeeted that portion ot" our Claiborne belt l\ing between 

 the Guadalupe in Texas and the Conehos in Mexico. During 

 these oseillalioiis of (lu^ land il is evidenl thai Hie relief at any 

 linu^ was slight. 



Jackson. Beginning west ot Ciroveton, in Trinity County, 

 Texas, in {he \alley of the Neches. and stretching eastward to the 

 Sabine is a belt eight or ten miles in width in which are found 

 calcareous clays aud sands with nodules and baiuls of impure lime- 

 stone, carrxing fossils of Jackson age. Vov the most part these 

 (Icposits lie directi) uptMi the cia\s of the ^'egua, since only occa- 

 sionall\ are the Fayette sands to be found between them. 



The identity of these deposits is clearly evident frcvm the con- 

 siderable number of fossils found at various localities. 



Vhc Jai-kson sediments ha\e not been founil west of CIro^•eton. 

 in their place, however, the Fayette sands graduall\- assume their 

 normal position in the section, showing less and less erosion, until 

 the Colorailo drainage is reached. 



The Jackson shore line nia> ha\e extended westwarci as far 

 as the Brazos, for sands thought to be at the top of the Fayette 

 near Wellborn liaxe yielded fossils which are now said to be of 

 Jackson age, allhough originally tlie collections were classed as 

 l.owiM' Claiborne. 



These .\rc supposed to be. however, a lower horizon in the 

 Jackson than the deposits farther east. 



In southeastern Texas we ha\e found indications of the gulf- 

 ward extension of the Jackson deposits in fossils from oil wells 

 drilled at Saratoga ami Sour Lake, but southwest of the Brazos 

 no iniliealions wliatexer o\ any lu.Uerials oi this age are known 

 either in Texas or in Mexico. 



We haw, therefore, in this eastern Texas area simply the 

 western limit oi the Jackson deposition anil the materials them- 

 selves in many places gixe exidence o\ the near-shore conditions. 



Almost nothing has been found in this area that throws light 

 on the happenings between the close of the ATiddle and Upper 

 Eocene and the beginning o\ (Migocene deposition. \\'hate\er there 

 max ha\e been is coxered bx the succeedini;' beds of the (.'•akxille. 



