80 E. D. Miser — Llanoria, the Paleozoic Land 



Concealed rocks of the Gulf Coastal Plain. 



The relations of the rocks along the borders of the 

 Gulf Coastal Plain show that the pre-Cambrian, Cam- 

 brian, Ordovician, Silnrian, Devonian, Carboniferous 

 (including Mississippian, Pennsylvanian and Permian) 

 rocks are overlain by Cretaceous and younger beds. 

 Eocks of these ages underlie the entire Gulf Plain, but 

 their age and character at any particular place can be de- 

 termined only by deep wells that penetrate the basement 

 rocks, though their general character may be inferred at 

 some places with a fair degree of certainty for a short 

 distance from their outcrops. For example, the pre-Cam- 

 brian crystalline rocks that are exposed in the Appalach- 

 ian region of Alabama doubtless extend many miles 

 southwestward beneath Lower and Upper Cretaceous 

 beds, and similar rocks that are exposed in the Arbuckle 

 Mountains of southern Oklahoma doubtless extend at 

 least several miles southeastward beneath Lower Creta- 

 ceous beds. 



Rocks belonging to the Pennsylvanian series are, so far 

 as known, the youngest Paleozoic rocks that lie beneath 

 the Gulf Plain except those in a small area along Red 

 River in northern Texas and southern Oklahoma, where 

 the underlying rocks are Permian. Xo Triassic and 

 Jurassic rocks are knoAvn to underlie any part of the Gulf 

 Plain, but some geologists postulate the occurrence there 

 of Permian or Triassic rocks in order to explain the 

 source of the enormous quantities of salt and other miner- 

 als of the numerous salt domes of Texas and Louisiana. 



E. T. Dumble^^ says : 



"In all the region east of Llano [Central Mineral region of 

 Texas] * * * the latest Paleozoic rocks are those of the Bend 

 formation, which is basal Pennsylvanian, and these are only 

 known contiguous to the Llano border. 



"Along the southeastern border of the Llano region the Cre- 

 taceous in places overlaps the Bend and lies upon the older Pale- 

 ozoics. Along the southern Hue the Bend seems to be entirely 

 absent. The evidence of further westward extension of the un- 

 derlying Bend is found in its exposures along the western border 

 of the Llano area and is obtained from well drilling. A well 



^Dumble, E. T., The geology of east Texas, University of Texas Bull. No. 

 1869, pp. 11-13, Feb., 1920. 



