THE FAYETTE BEDS. 47 



we place their inland limit below Roma, the line of separation on the Rio 

 Grande between the Fayette Beds and Timber Belt Beds would curve out- 

 ward toward the Gulf of Mexico, whereas we should expect it to curve in- 

 ward, just as the line between the Cretaceous and the Timber Belt Beds does, 

 on account of the probable embayment on the Rio Grande at the time of their 

 deposition. These beds lying between here and the coastal region will be 

 treated under the heading of "Fayette Beds." A more detailed discussion 

 of the Rio Grande strata is reserved until the fossils have been thoroughly 

 studied. 



THE FAYETTE BEDS. 



These beds underlie the interior part of the coast plains of East Texas, and 

 as we near the Gulf shore they are seen to gradually dip under the Post- 

 Tertiary deposits. The surface of the country consists of a rolling prairie, 

 and parts of it are undoubtedly destined to become very rich agricultural 

 regions, combining as they do all the advantages of a rich soil, a well-watered 

 country, and the temperate climate of the sea coast. 



The thickness of these strata is at the minimum 350 feet, and probably 

 nearer 400. They consist of a series of clays and sands, very characteristic in 

 their color, mode of occurrence, and associations, and are easily distinguished 

 from any other beds in the Tertiary series of Texas. They include all those 

 beds found on the Brazos, Colorado, and Rio Grande which lie between the 

 uppermost fossiliferous strata of the marine Tertiary below and the Post- 

 Tertiary clays, limestones, and pebble beds above. Above the uppermost of the 

 marine Tertiary already described on the Brazos and Colorado rivers, occurs 

 a series of clay and sandy strata, the clay rapidly becoming more and more 

 predominant as we go up the series, until the beds are composed almost ex- 

 clusively of it. Then again the sandy beds suddenly assume predominance 

 and extend upward to the Post-Tertiary beds. The lower or clayey part of 

 this series composes a little over half of the formation, and the sandy beds 

 compose the rest. 



These beds represent the u Grand Gulf" series of Hilgard's Mississippi sec- 

 tion. Professor Angelo Heilprin, in speaking of the Grand Gulf Beds, says: 

 " No unequivocal deposits of Miocene age have thus far been detected on the 

 Gulf slope, although strong grounds exist for the supposition that the forma- 

 tion designated by Hilgard as Grand Gulf Group belongs to this period of 

 geologic time, but to which division or horizon of the same it is as yet impos- 

 sible to state."* In Mississippi and Louisiana, as in Texas, the base of this 

 formation is composed of clays with lignite beds, and the upper part consists 



*" Contributions to the Tertiary Geology and Paleontology of the United States," Prof. 

 Angelo Heilprin, 1884, p. 4. 



