250 CENTRAL MINERAL REGION OF TEXAS. 



Again, in discussing North American Cretaceous history,* referring to the 

 " Paleozoic area of Central Texas," he remarks: 



It is also evident that it was completely covered by sediments during the two great sub- 

 sidences in Cretaceous time, etc. 



In the same paper (p. 284) he repeats his assertion in the following words: 



The Trinity formation * * * clearly marks the interior shore line of the oldest Ameri- 

 can Cretaceous, as well as the beginning of a great subsidence which initiated that epoch 

 and gradually covered the whole of the Texas Paleozoic area. . 



The same idea is reiterated in a later paper, giving details of his observa- 

 tions in Burnet County. In this paperf many interesting observations are 

 recorded, and a sketch map and section are appended. The general conclu- 

 sions announced are as follows: 



The absence of the Devonian is probable. I made a section at Marble Falls to conclu- 

 sively settle the question, and, as final authority, sent the faunas to Prof. H. S. Williams for 

 determination. In my opinion the alleged Devonian is identically the Carboniferous lime- 

 stone of North Texas, which has here been intensely metamorphosed by igneous contact. 



* * * The presence of Spirophyton, * * * and of Ghonetes and other forms, indicates a 

 lower Carboniferous position for these limestones, * * * while there is a complete un- 

 conformity between them and the overlying shales, sandstones, and conglomerates of the 

 coal measures. * * * 



The Lower Cretaceous rests directly upon the metamorphosed limestones of the Carbonif- 

 erous at Burnet. 



Mr. Hill is, I believe, the first authority who has assigned dates to the 

 granite outburts, other than the earliest " extrusions" referred to by Walcott. 

 He says (loc. cit., p. 291): 



Perhaps the two most remarkable features of this section are the great igneous disturb- 

 ances at the close of the Paleozoic and Cretaceous respectively. The one at the close of the 

 Carboniferous is most beautifully recorded in the southwest corner of Burnet County. * *• * 



This great granite outcrop, from which the material was secured for the State Capitol, oc- 

 cupies a circular area ten miles in diameter, and is of late Carboniferous or Post-Carbon- 

 iferous age. 



In a foot note Hill adds: 



The writer believes that Mr. Walcott was justifiable from his observations to the west- 

 ward in concluding that all the granite of Burnet County was Cambrian, but the evidence 

 here described, which I think he did not see, shows it to be of later age. 



The pages of this report will, I think, demonstrate that neither Mr. Hill 

 nor Mr. Walcott have yet seen enough of the complicated geology of the 



*Events in North American Cretaceous History, illustrated in the Arkansas-Texas division 

 of the Southwestern region of the United States. By Robert T. Hill. Amer. Jour. Science, 

 vol. XXXVII, April, 1889, p. 283. 



f A Portion of the Geological Story of the Colorado River of Texas. By Robert T. Hill. 

 American Geologist, vol. Ill, 1889, pp. 287-299. 



