DESCRIPTIONS OF FORMATIONS 465 



these carry plant fragments. The volcanic ash beds give a good working 

 horizon, as they are fairly continuous west of Groveton. 



Sections in Walker and Grimes counties are very similar to that on the 

 Trinity. At one locality, near the line between these two coimties, a bed 

 of laminated chocolate clays was found, in which there were balls and 

 masses of Grahamite 8 to 10 inches in diameter. 



Fossils were found in colonies in sandstones near the base of the Jack- 

 son series at a nimiber of localities west of the International & Great 

 Northern Eailway, and the upper carbonaceous clays of the Manning 

 stage also furnished a few fossil-bearing localities similar to those further 

 east. At one localit}^, 2^^ miles west of Bedias, Suman reports the sand- 

 stone packed with fossil casts apparently identical with those from 2 

 miles north of Corrigan. The fossils collected from these have not yet 

 been studied. 



Unfortunately, the work was suspended before the exact connection of 

 these beds and the Wellborn of Kennedy was determined. The proba- 

 bility, however, is that they are the same, and that Vaughan's reference 

 of the Wellborn to the Jackson is correct. In this case the name Well- 

 born, instead of being a synonym for Fayette, would characterize the 

 basal beds of Jackson age in Texas. 



The Jackson is distinguished by the fact that in it the clay ironstone 

 and limonitic concretions of the underlying Yegua are replaced by cal- 

 careous concretions and by a greater proportion of sands and sandstones. 

 Some of the Jackson sands are very hard, even quartzitic, but are always 

 light gray in color and are fossiliferous in places. Volcanic ash beds are 

 also characteristic. The top of the Jackson is placed where the chocolate 

 laminated clays and carbonaceous sands give place to coarse "rice" sands 

 or sandstones and yellowish green, structureless clays and claystones. 



CORRIGAI} 



The name Catahoula has been proposed by Veatch for the sands over- 

 lying the Jackson and underlying the Fleming, but expressly limited its 

 use to such as were of true Grand Gulf age. Deussen used the name in 

 a mucli wider sense to include a large part of the Jackson as well. It 

 is here proposed to use Kennedjr's older term Corrigan sands for the 

 group of deposits lying between the known Jackson and the Fleming, 

 which, while forming the only mapable unit, prol)ably includes beds of 

 later age than the Catahoula of Veatch, which name should be retained 

 for that portion of the Corrigan to which it strictly applies. 

 XXXVI— Boll. Geol. Soc. Am., Vol. 26, 1914 



