698 J. L. TILTOX STRATA NEAR STUART, IOWA 



of the Deer Creek 7 beds north of Stennett, but the Meadow and other beds 

 belonging above them stratigraphically are here removed by erosion. 



Position of the Fault 



The Thurman-Wilson fault, which had previously been located north- 

 west of Eed Oak, northwest of Briscoe, and near Bridgewater, thus lies 

 betAveen the center of section 13, Grove township, and the northeast quar- 

 ter of the southeast quarter of section 18, Harrison township ; and the 

 extension of it toward the northeast passes north of Earlham, between 

 the outcrop in the northwest quarter of the northwest quarter of section 

 31 (township 78 north, range 29 west) and the outcrop a mile and a half 

 west-southwest from that location. It should be noted that at both of the 

 locations of the fault in the area here considered the lines that cross the 

 fault run diagonally to it, so that the location of the fault is limited to a 

 much shorter distance, if measured in a direction at right angles to the 

 direction of the fault. As worked out in a previous report, 8 the fault is 

 a normal fault, with fault-plane dipping steeply to the southeast. In the 

 southwestern part of the State the locations made a straight line, but in 

 the region here considered there is a marked curve to the north. 



Stratigraphic Position of Beds on the upthrow Side of Fault 



What are the beds that lie on the west (upthrow) side of the fault 

 from section 18, Harrison township, to north of Earlham ? 



Bain, 9 in his report on Guthrie County beyond the supposed base of the 

 Missouri stage near Stuart, remarks on the "great similarity" of the ap- 

 parently upheaved beds found farther north "to those in the upper por- 

 tion of the Cherokee shales," but did not include in the comparison the 

 strata immediately north of Stuart. 



Leonard, 10 in his report on Dallas County, mentions both Clionetes 

 mesolobus and Marginifera (Productus) muricata as found near Adel, 

 which is in the Des Moines stage and on the upthrow side of the fault. 

 Clionetes mesolobus is also reported from strata well down in the Des 

 Moines stage in Polk 11 and Keokuk 11 counties. It is reported from the 



7 Deer Creek is here used in its geological sense, as the name of a purl ion of the 

 Shawnee division of the Missouri stage. Deer Creek, as previously used in this paper, 

 happens to be the name of a small stream north of Stuart and is without geological 

 significance. 



s John L. Tilton : Geology of Cass County, p. 211, and Geology of Adair County, p. 

 302. both reports in the Iowa Geological Survey, vol. xxvii. 



9 H. Foster Bain : Geology of Guthrie County. Iowa Geological Survey, vol. vii, 1S96, 

 pp. 429 and 445. 



10 A. G. Leonard : Geology of Dallas County. Iowa Geological Survey, vol. viii. 1S97. 

 p. 71. 



11 Iowa Geological Survey, vol. vii, p. 331, and vol. iv, p. 272. 



