THE THURMAN-WILSON FAULT 389 



that Todd^ and Smith^ thought a continuation of the Thurman- 

 Wilson fault in Iowa. It seems strange that there should be a 

 displacement of 300 feet on the Iowa side of the river and of but a 

 few feet on the Nebraska side, and even more strange now that we 

 know that the fault continues to the northeast with but little 

 diminution of displacement to at least near the center of Iowa, 

 Perhaps there is a displacement further north or south in Nebraska 

 that has not yet been located. 



Why no oil has been found in southwestern Iowa, southeastern 

 Nebraska, and northeastern Kansas has received no satisfactory 

 explanation as yet in published reports. With the consent of 

 G. E. Condra, professor of geography and conservation at the 

 University of Nebraska, I call attention to his oral statement that 

 in the southeastern part of Nebraska granite was found at a depth 

 of five hundred feet from the surface and penetrated for a depth of 

 a thousand feet. This great mass of granite lies between south- 

 western Iowa and the oil fields further southwest, and, whatever 

 other conditions are involved, bars underground circulation through 

 formations that farther southwest are oil-bearing. 



Border of the Missouri stage. — ^North of the fault plane (the 

 upthrow side) erosion has given the east-west trend of the Missouri 

 stage in Guthrie County. South of the fault plane (the downthrow 

 side) the base of the Missouri stage extends far to the east. The 

 extension to the eastward is thus not simply an uneroded mass of a 

 highland region, as formerly supposed, but an uneroded portion 

 left protected on the downthrow side^ of a fault plane. Still further 

 to the northeast, even to the "Driftless Area," along the general 

 direction of the Thurman-Wilson fault may be noted east-west 

 extensions of the various formations as mapped, as if the effect 



'J. E. Todd, "On the Folding of the Carboniferous Strata in Southwestern 

 Iowa," Proc. of the Iowa Acad, of Set., I, Part I (1889), 61; also XIII (1906), 1S4. 



^ G. L. Smith, "Carboniferous Section of Southwestern Iowa," lo'wa Geol. Siirv., 

 XIX (1909), 612. 



* No one has as yet determined whether or not a continuation of Keyes's Cap-au- 

 Gres fault bounds the eastern side of the Missouri stage in Iowa. He describes the 

 fault as extending from Leon, Iowa, southeast to Vincennes, Indiana, but he gives no 

 data with reference to the Iowa end of the line ("Extent and Age of the Cap-au-Gres 

 Fault," Proc. of the Iowa Acad, of ScL, XXIV [1917], 61). 



