WICHITA MOUNTAINS. 321 



tion which my recent observations have shown to be correct. He re- 

 marks:* 



Taking all the facts into the account, I can not but feel that there is reason to presume 

 that volcanic agency has been active in that region more recently, than the trap dykes. 



Of this more in due time. The route selected took us across the Permian 

 plain northwestward from Henrietta, Texas, by the most direct road to Fort 

 Sill, Indian Territory. Crossing Red River by the ferry below the mouth of 

 the Big Wichita, our course lay along the valley of the East Fork of Cache 

 Creek. Along this line no evidences of any rocks except the Permian sand- 

 stones and overlying red clays were seen until reaching a point fifteen miles 

 south of Fort Sill, where fragments of Silurian limestone and a porphyrytic 

 rock appear in the drift. Back of this, at the stage stand about twenty-six 

 miles from Fort Sill, there is an exposure of false-bedded Permian sandstone, 

 apparently dipping south 1 6 degrees. This is the first indication of an east- 

 west strike which was observed. Black sand occurs in the wash at the south- 

 ern limit of the drift, and this becomes very abundant nearer the mountains. 

 It is fine grained, crystalline magnetite, and probably also ilmenite. 



About one mile southeast of Fort Sill one of the hills has been cut down 

 upon two sides, and much rock has been taken from the quarry for use in 

 building at the post. This affords a fair section of Silurian limestone very 

 similar to that above mentioned as "float." The horizon is nearly that of the 

 typical section on Cold Creek, Llano County, the fossils being somewhat 

 abundant, but chiefly fucoids and non-characteristic markings. It is exceed- 

 ingly interesting to find here the same master- joints as in the Central Texas 

 area. The dip is 1 1 degrees, south 65 degrees east, locally, but the east- west 

 (Post-Carboniferous) trend is well pronounced. The Silurian break of north 

 25 degrees east is very prominent. 



At the southeastern portion of the Wichita range, near Fort Sill, the trap- 

 pean ridge referred to by Marcy and Shumard presents a marked topographic 

 and geologic feature. \ It was evidently not understood by these explorers, and 

 in fact it would be next to impossible to work out the Wichita structure in 

 detail without some such historical key as is furnished by the stratigraphy 

 of the Central Texas Region. 



Upon Marcy's Itinerary Map some of this portion of the mountains is 

 marked as "Trap Bluffs," and Shumard's diary has the following entries: 



July 17. — Many of the mountains presented a marked difference in character and com- 

 position from any that had been previously observed; instead of displaying a rough and 



*Marcy's Report, p. 147. 



f For these important elevations, extending from the target grounds at Fort Sill westward 

 to the main Wichita range, near Mount Sheridan, I propose the name of " Carlton Mountains," 

 in honor of Colonel Carlton, the present commandant at Fort Sill. 

 U 



