186 Gould — Geology of Parts of the Seminole, 



southern line of the State sandstones have already begun to 

 appear. To the south these conditions obtain more and more 

 until the limestone is entirely replaced by sandstone. Even in 

 Kansas the rock east of the Flint hills is sandstone and shale. 

 To the west the limestones gradually thin out and give place 

 to shales (the Marion and Wellington formations) which farther 

 west are succeeded by the Red-beds. South of the State line 

 the sandstones from the east and the Red-beds from the west 

 begin to approach each other, while the limestone ledges be- 

 come thinner and thinner and the flint less pronounced. 



In Pawnee County, Oklahoma, there are still some heavy 

 ledges of limestone, although even here sandstones greatly pre- 

 dominate. In eastern Payne County, fifty miles south of the 

 Kansas line, the conditions have changed still more. The 

 following section taken at Ingalls will illustrate the succession 

 of the various rocks : 



Section at Ingalls, Oklahoma. 



No. Feet. 



13. Red clay and sandstone 20 



12. Red sandstone ' 2 



11. Red clay shale... 20 



10. Two ledges of hard, flinty, fossiliferous 

 limestone, 1 to 2 feet thick, sepa- 

 rated by 1 foot of greenish clay 5 



9. Red clay shale 50 



8. Sandstone 5 



7. Red and green shale 10 



6. Limestone ._ 1 



5. Shales 10 



4. Limestone 1 



3. Greenish shale 5 



2. Limestone 1 



1. Shales _ - 20 



Total 150 



~No. 10 forms the cap of the noted Twin Mounds, seven miles 

 east of Ingalls, as well as the tops of numerous bluffs and 

 escarpments in the vicinity. It is the most pronounced ledge 

 in the region and is the one that gives tone to the erosion forms. 

 It will be observed, however, that of the 150 feet of strata 

 represented but eight feet are limestones, the remainder being 

 either sandstone or shale, with the latter predominating. 

 Above the rocks represented in this section only shales and 

 sandstones of the Red-beds are to be found. The gradation 

 from the underlying Permian or Carboniferous to the super- 

 jacent Red-beds is so slow that when on the spot it is not easy 

 to tell just where the one leaves off and the other begins. At 



