360 GEOLOGY OF NORTHWESTERN TEXAS. 



The above table gives the geological formations of the northwestern part, 

 of the State as I now understand it. I have confined my work largely to the 

 Permian and Carboniferous formations, giving only such attention to the 

 other members of the section as was necessary to determine the relation of 

 the Permian and Carboniferous formations to the overlying and underlying 

 series, and to enable me to determine with accuracy the extent of these two 

 formations in this part of the State. 



On Plate VI, 1 have given a columnar section of the strata (higher than the 

 Devonian) in northwestern Texas, with the provisional divisions which I have 

 made of them. 



SILURIAN. 



The Silurian lies along the southwestern border of the Carboniferous, the 

 boundaries of which will be given in another place in this Report. It also 

 occurs on both sides of the Wichita Mountains in the Indian Territory. This 

 formation will be reported upon by Prof. Theo. B. Comstock, and needs no 

 further notice from me in this connection. 



DEVONIAN. 



The Devonian is entirely wanting along all the lines of contact between the 

 Carboniferous and the older rocks, so far as I have been able to determine. 

 1 have not seen this formation anywhere in the State, yet it may exist. 



SUB-CARBONIFEROUS. 



In 1879 Mr. Chas. D. Ashburner made a report to some capitalists, which 

 by permission was read before the American Institute of Mining Engineers, 

 at the Philadelphia meeting in February, 1881, and afterwards published in 

 in their proceedings, entitled "Brazos Coal Field, Texas." This paper was a 

 report made after personal examinations in Young and Stephens counties by 

 himself. He makes the thickness of the true Coal Measures in Texas three 

 hundred feet, and below that he says he found a limestone one hundred and 

 fifty feet thick that belonged to the Sub-Carboniferous, and made it the equi- 

 valent of the Chester Group. He gives as his reason for so believing that he 

 found a conglomerate above the limestone that belonged to the Millstone 

 Grit or the base of the Coal Measures. As there is more than one thousand 

 feet of the Coal Measures below the bed of conglomerate mentioned, and below 

 the limestone which he calls Sub-Carboniferous, there is no possible chance 

 for these limestones being Sub-Carboniferous. 



In 1885; in his report on the Mineral Resources of the United States, pub- 

 lished in 1886, Washington, he reiterates his former assertions in reference 



