WICHITA MOUNTAINS. 319 



ries and the Capitol granites at their junction, where they shade into each 

 other somewhat gradually. All the features of this character are, however, 

 very readily explainable upon the supposition that the material was in part 

 the result of the remelting of the older magma at its edges. 



THE POST-CRETACEOUS DEPOSITS. 



There are numerous local accumulations of travertine and tufaceous ag- 

 glomerates, besides alluvial sands and clays, which may be of some geologic 

 importance in future studies of the surface deposits. But at present very 

 few of these can be considered of much moment in the general history of 

 the country, nor are they of economic interest. There can be no doubt of 

 their Post-Cretaceous origin. Ln the bed of Cold Spring Creek, near Loyal 

 Valley, Mason County, we dug out a large tusk of a mastodon or mammoth, 

 which was imbedded in the conglomerate, and the material of these deposits 

 is always more or less restricted to the debris of adjacent rocks. Nowhere 

 in the Central Mineral Region have any extensive accumulations of this na- 

 ture been found, which may have represented a widespread terrane of Ter- 

 tiary or later date, except in a remarkable basin in the Llano River Valley, 

 about ten miles east of Junction City. 



RELATIONS OF THE WICHITA MOUNTAINS TO THE CENTRAL 



PALEOZOIC ERA. 



As stated at page 257 of this volume, the results of studies in the Central 

 Mineral Region left at least a possibility that one or other of the upheavals 

 hereinbefore described might have extended its influence to the little known 

 Wichita Mountains. As the key to our district gradually began to assume 

 definite form, and as the work of other members of the survey became ex- 

 plicit, the probability of the existence of some important relations between 

 the two areas grew more evident. The perusal of Marcy's and Shumard's 

 reports,* although these do not give much idea of the structure of the moun- 

 tains, indicated that a fair knowledge of that district would be very advan- 

 tageous in the study of our own. 



As, in the opinion of the State Geologist, the trip also promised results of 

 great value in their direct bearing upon the geology of the Coal Measures and 

 Permian beds of North Texas, especially in regard to artesian water conditions, 

 Mr. W. F. Cummins and the writer were instructed to make a reconnois- 



*Exploration of the Red River of Louisiana in the Tear 1852. By Randolph B. Marcy, 

 Captain Fifth Infantry, U. S. A.; assisted by George B. McClellan, Brevet Captain, United 

 States Engineers. With Reports on the Natural History of the Country and Numerous 

 Illustrations. Washington, 1854. (H. R. Exec. Doc., 33d Cong., 1st Session.) Appendix 

 D— Geology, Part II. By George G. Shumard, M. D. 



