324 CENTRAL MINERAL REGION OF TEXAS. 



exposure there is a belt of higher beds, endyked as it were in a nearly ver- 

 tical dip with a northeast strike, breaking across the strikes of the earlier 

 uplifts. This trend of the Cretaceous upheaval is again visible in the form 

 of joints and special porphyry and quartz dykes, further northeast in the 

 Palisades upon Cache Creek, near Fort Sill. 



Upon the far north side of the Wichita range, some sixty miles north north- 

 west of Fort Sill, and perhaps forty miles northeast of Navajoe Town (G-reer 

 County) there is a very similar but more comprehensive exposure of the Silu- 

 rian beds, with the reverse dip of 1 6 degrees north, and broken escarpments of 

 the same character are visible along the flank of the range eastward. In the 

 outcrops visited by me there is a fine section of 250 feet of the Siliceous lime- 

 stones extending from below the horizon of the lowest stratum in the Fort 

 Sill quarry to a level equivalent to the summit of the Cold Creek Section of 

 Central Texas. The facies is in all respects identical with the Texas Silurian, 

 except that the beds of the Wichita foothills are more fossiliferous, contain- 

 ing corals, Brachiopods, etc., in addition to the meagre fauna of our district. 



In all these Silurian cliffs there are beautiful illustrations of sea shore ero- 

 sion subsequent to their elevation. The Fort Sill Beds run up horizontally to 

 the base of the escarpment and intrude within the irregular bays, which have 

 been cut into it by the waves of the Tertiary? sea in which they were formed. 

 Even in the crater-like basins, high up in the mountains themselves, lacus- 

 trine deposits of great thickness have been accumulated, and everywhere the 

 Tertiary and Quaternary sediments have deeply buried the ancient terranes, 

 so that, with the exception of the Silurian and the outlying Permian, there is 

 not a relic of any Paleozoic or earlier stratum of aqueous origin, or any of the 

 schists. The interpretation of the geologic history of the whole Wichita range 

 consequently hinges upon an accurate acquaintance with the meaning of each 

 orographic movement as tested by the character of the irruptives, chiefly 

 eruptive, which each trend displays. In treating the subject, it is assumed that 

 the details of the geology of the Central Texas complex, as outlined in this re- 

 port, are sufficient to prove the full value of these axial trends as elements in 

 diagnosis wherever the relative ages can be determined by their intersections. 

 This test is all that is left us in the Wichita chain, except, as stated in the 

 case of the Post-Carboniferous uplift, which has involved the Permian Beds 

 in one or two places where they are now uncovered. 



The Burnetan axis of the range is the most persistent of all the strikes. 

 If it be true that the Headquarters Mountains, in G-reer County, are of this 

 age, as is most probable, the line of peaks, from 200 feet to 1300 feet above 

 the plains at their bases, extends with few extensive gaps for a distance of 

 about 100 miles in a course parallel to the trend of the oldest Archaean rocks 

 of Central Texas. 



