320 CENTRAL MINERAL REGION OF TEXAS. 



sance of as much of the Wichita Range and outlying hills as was possible in 

 the limited time that could be given to it. This arrangement was made in 

 order that, by the knowledge already acquired by us, each in his own district, 

 we might more rapidly and certainly ascertain the exact relations of the 

 various formations. The results of this very interesting reconnoissance, as 

 they relate to the Central Mineral District, are embodied herein. 



We have had no knowledge heretofore of the age of the Wichitas. Mr. 

 Hill remarks:* 



"Concerning the latter [i. e., 'the red granites, basalts, porphyrites, and eruptives of the 

 Wichitas'], no more is now known than was expressed as follows by Dr. Edward Hitchcock 

 some years ago." [Here follows a quotation from pages 146, 14*7, of Marcy's Report] 



Mr. Hill, in the article quoted, j- has given a general statement based in part 

 upon his own observations at a distance, but excepting this, I know of no 

 other allusions in print to the geology of the Wichita Mountains. 



Dr. Hitchcock wrote in 1853 a portion of Appendix D to Marcy's report, 

 being "Notes Upon the Specimens of Rocks and Minerals Collected." As he 

 was not a member of the expedition and never visited the Wichitas, the con- 

 clusions drawn were necessarily of little importance. 



Dr. Shumard, in his own itinerary, gives very little more than a running 

 description of special occurrences of " granite, quartz, and greenstone por- 

 phyry," so far as the mountains themselves are concerned. 



The impressions gained from the reading of the papers quoted above were 

 about as follows: 



(1) That the Wichita Mountains are chiefly granitic, but that irruptives of 

 basic character occur in parts of the region. 



(2) That the Post- Carboniferous uplift (Ouachita orographic system of Hill) 

 is represented by a considerable portion of the range, especially eastward. 



(3) That unexplored portions of the chain might be found to be of Ar- 

 chaean age. 



The last conclusion, in the writer's mind, was based very largely upon the 

 belief that the Central Mineral tract is the key to a wide region upon all sides 

 of it; but the statements made to me by Messrs. Cummins and Hill, who had 

 examined intermediate territory, in addition to my own acquaintance with 

 some of the complicated geology of Arkansas, had much to do with confirm- 

 ing this opinion. 



Before proceeding to the discussion proper, it is only fair to quote from 

 Dr. Edward Hitchcock's paper, already referred to, the following generaliza- 



* American Geologist, vol. V, p. 73. February, 1890. 



f Classification and Origin of the Chief Geographic Features of the Texas Region. By Robt. 

 T. Hill. American Geologist, loc. tit, p. 12 et seq. 



