GEOLOGICAL PAPERS. 117 



with sandy accumulations, which in places form sand-hills and in other 

 localities are spread out as a thin mantle. The Equus Beds, in Mc- 

 Pherson county, belong to this formation. The eastern boundary of 

 the lowland is the line of intersection of the structural plain of the 

 western slope of the Flint hills with the level country of the Arkan- 

 sas valley, and is not strongly marked by any topographic features. 

 It may be drawn with reference to the occurrence of the limestones, 

 on the surface of which the Flint Hills upland is developed. The 

 Great Bend lowland, considering its elevation and general surface 

 features and its relations to the other divisions of the prairie plains, 

 is a natural part of them, although it forms an arm extending be- 

 tween the uplands of the Great plains. 



The explanation of the origin of the great bend of the Arkansas river, 

 given in the following quotation, was outlined by the writer when in the field, 

 and was subsequently embodied by Haworth in his report: "One of the most 

 notable features in connection with the Arkansas river is the great and unusual 

 bend it makes in passing from eastern Ford county so far to the north to Great 

 Bend, and back so far to the south. ... It would seem that when the river 

 reached the Dakota formation, a formation so easily corraded, it immediately be- 

 gan acting upon it with great vigor. As the general inclination of the strata of 

 the Dakota is to the northeast, . . . and the Dakota sandstones are easily 

 corraded, it would seem that this was the cause of the river's great bend to the 

 north. We may safely believe that at an early period in the history of the river it 

 passed eastward from Ford county across the north of Kiowa, Pratt and King- 

 man counties, probably passing out of the state not far from its present location. 

 If this explanation is correct, one cannot help inquiring why the river did not 

 break through the upland, in the vicinity of McPherson county, and ultimately 

 join the Cottonwood river through Marion and Chase counties. To answer this 

 clearly, we only have to look at the general geologic character of the southern 

 part of the Flint Hills in Butler and Cowley counties to find an adequate reason. 

 The great Flint hills area has its surface rising to points considerably higher 

 than the main uplands of Sumner and Sedgwick counties. Evidently these high 

 elevations in the the early Tertiary times deflected the river southward, and pre- 

 vented it from crossing the Flint Hillsfregion when the drainage was first changed 

 to an easterly direction by elevation of the Rocky Mountains. The same Flint 

 Hills area has continuously remained higher than the uplands in Sumner, Sedg- 

 wick and adjoining counties. Therefore, with the river once flowing out of the 

 state near where it now does, it would be impossible for it to pass eastward across 

 the Flint hills so long as the elevations remain as they now are." (Haworth, 

 Univ. Geol. Surv. Kan., vol. II, pp. 30-32.) 



GREAT PLAINS KEGION. 



The Great Plains region, or, as it might properly be called, the 

 Great Plains plateau, lies between the Prairie plains and the Rocky 

 Mountains, its limit not being marked by sharp differences of eleva- 

 tion or changes in topographic features. It is crossed by a number 

 of streams which head in the mountains and in their lower portions 

 unite to form the great river system of the Mississippi valley and the 

 drainage of the western Gulf coast. The Great plains extend north 



