BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 33, pp. 689-702 November 2. 1922 



STRATA NEAR STUART, IOWA 1 



BY JOHN L. TILTON 



(Read before the Society December 28, 1921) 



CONTENTS 



Page 

 Introduction 689 



Area near Earlham and south of fault 691 



Area near Earlham and northwest of fault 691 



Contrasts on the two sides of fault 693 



Area north of Stuart, along Deer Creek, north of fault 695 



Area southwest of Stuart, along Middle River, north side of fault to fault- 

 line 697 



Position of the fault 698 



Stratigraphic position of beds on the upthrow side of fault 698 



Bearing of fault on position of coal and on lay of strata to the north 701 



Bearing of fault on position of coal west of Stuart 701 



Effect on the interpretation of deep-well records, and geological map of 

 Iowa 701 



Introduction 



The Thurman- Wilson fault has already received some attention in the 

 geologic literature of Iowa. 2 Todd recognized it close to Missouri River 

 in 1889; Smith computed its throw (300 feet) at that point in 1909, and 

 expressed the opinion that it changed into an anticline farther to the 

 northeast, near Red Oak and Stennett; Keyes, in 1916, mentions its pres- 



1 Manuscript received by the Secretary of the Society January 23, 1922. 

 Published with the approval of the Director of the Iowa Geological Survey. 



2 J. E. Todd: On the folding of the Carboniferous strata in southwestern Iowa. Pro- 

 ceedings of the Iowa Academy of Science, vol. i, part i, 1889, p. 61 ; Some varied con- 

 clusions in Iowa geology, ibid., vol. xiii, 1906, p. 184. 



G. L. Smith : Carboniferous section of southwestern Iowa. Iowa Geological Survey, 

 vol. xix. 1909, p. 612. 



C. R. Keyes : Controlling fault systems of Iowa. Proceedings of the Iowa Academy 

 of Science, vol. xxiii, 1916, p. 103. 



John L. Tilton : The Thurman-Wilson fault through southwestern Iowa, and its bear- 

 ing. The Journal of Geology, vol. xxvii, 1919. p. 383 ; Geology of Cass County. Iowa 

 Geological Survey, vol. xxvii, 1916, published in 1920-1921, p. 211; Geology of Adah- 

 County, ibid., p. 301 ; Carboniferous strata of the Missouri stage in southwestern Iowa, 

 manuscript not yet published, Iowa Geological Survey. 



(689) 



