24 THE IRON ORE DISTRICT OF EAST TEXAS. 



"Sufficient data have not as yet been collected to warrant an attempt at a 

 detailed correlation of all the Texas Tertiary with that of the other Gulf 

 States, and therefore the various strata are provisionally divided as above. 

 The classification depends, first on their lithological character; and secondly, 

 on the very different and very characteristic topography that each of the 

 three divisions gives to the country underlaid by it. The Basal or Wills 

 Point Clays underlie a narrow strip of rich rolling prairie region, east of and 

 parallel to the great Cretaceous prairie of Central Texas. The Timber Belt 

 sands and clays underlie the great timber region of East Texas. Through- 

 out the whole of the Eocene area no evidence of any considerable break in 

 deposition can be seen. The lagoon and marine deposits appear to have al- 

 ternated with each other in an unbroken series. Frequently there are found 

 in one bed fragments of the stratum that underlies it, but no great amount 

 of erosion of these lower beds appears to have taken place, and the little that 

 has gone on is simply what might have been expected to accompany a grad- 

 ual transition from one kind of deposition to another. The paleontological 

 evidence on this point, though as yet somewhat meagre, all tends to show a 

 gradual and almost continuous deposition from bottom to top of the series, 

 and the few breaks in the fauna that have been observed can probably all be 

 explained by the interposition between the fossiliferous beds of the lignitic 

 and other non-marine strata. In this continuity of deposition the Texas 

 Eocene closely resembles that of Mississippi, the different stages of which, ac- 

 cording to Hilgard,* 'are intimately interconnected by community of species, 

 from Claiborne to Vicksburg.' " 



BASAL OR WILLS POINT CLAYS. 



" At the base of the Tertiary and immediately overlying the eroded surface 

 of the uppermost Cretaceous strata in East Texas is a great bed of stratified 

 clay, which, on account of its position as the lowermost bed of the Eocene in 

 this region, has been provisionally called the Basal Clays. These underlie a 

 stretch of interspersed prairie and timber lands, the country being composed 

 mostly of prairie, with occasional belts and groves of timber. The timber is 

 all hard wood, consisting mostly of post oak, blackjack, and hickory. The 

 belt is sometimes over ten miles wide, and runs between the western edge 

 of the timber and the Central Texas prairies, from the northern part of the 

 State to the Colorado River and beyond. The stratification of these beds is 

 very characteristic, and is very different from the massive structure of the 

 underlying Upper Cretaceous ' Ponderosa Marls,' but on a weathered surface, 

 where the stratification is not seen, the clays of the two formations are not 



*"The Old Tertiary of the Southwest," Am. Jour, of Science, Yol. XXX, Oct., 1885, p. 267. 



