1S97.] DRAKE — THE GEOLOGY OF IXDIAX TERRITORY. 329 



Mountain System in the Indian Territory, which further classified 

 the knowledge of this system. 



The work of the Arkansas and the Texas geological surveys, the 

 geologic investigations in southeastern Kansas by Prof. Charles S. 

 Prosser, and an unpublished sketch map kindly furnished by Prof. 

 Orestes St. John, showing the general distribution of the geologic 

 formations in the Indian Territory, further assisted in giving an 

 idea of the geology of this area. Taken as a whole, however, the 

 field was comparatively a new one to geologists and it is rather 

 remarkable that it should have so long remained so little known. 



Hydrography. — Nearly all of the area under consideration is 

 drained by the Arkansas river and its tributaries. A very little of 

 the southern part, however, is drained by streams tributary to tlie 

 Red river. The Arkansas river enters the country under discus- 

 sion a little south of the northwest corner, and runs in a south- 

 easterly direction, thus crossing it diagonally through the central 

 portion. To the nortli of this river the larger streams, the Illinois, 

 the Grand, the Verdigris, and the Little Verdigris or Caney rivers, 

 fiow nearly southward and empty into the Arkansas river. The 

 Illinois river, however, is somewhat deflected to the westward, and 

 the Verdigris and Caney rivers deflected to the eastward. The 

 streams on the north thus have a tendency to flow into the Arkansas 

 river at the same locality. 



To the south of the Arkansas river the Cimarron and the Cana- 

 dian rivers are its largest tributaries. The Cimarron, the most 

 northerly of the two, flows eastward into the Arkansas river, while 

 the Canadian river is slightly deflected to the north in its eastward 

 course, and enters the Arkansas river about twenty miles below the 

 collecting basin of the streams to the north. Between the Cimar- 

 ron and Canadian rivers, the Deep Fork and North Fork of Cana- 

 dian rivers, flow almost eastward and unite a short distance above 

 their confluence with the Canadian. 



Topography. — There are three general topographic groups in this 

 area. One is the elevated and folded area to the south, which is an 

 extension of the Ouachita mountain system ; a second group is 

 the elevated plateau area in the northeast, which widens slightly 

 southward to near the Arkansas and the Grand rivers. This belongs 

 to the Ozark plateau system. The third group is a broad plain-like 

 area that slopes gently eastward in terrace-like escarpments and 

 undulations, and narrows into the low depression between the Ozark 



