700 J. L. TILTON STRATA NEAR STUART, IOWA 



The present writer, having noted the evidence of a fault through the 

 region and knowing that the strata found did not reproduce any part of 

 the upper portion of the Des Moines stage, 14 visited the region north of 

 Centerville and near Eathbun 15 and there noted the same general relation 

 of strata found northwest of Earlham and north of Stuart and the same 

 assemblage and relative abundance of fossils in the upper portion of a 

 43/2-foot De( l of dense limestone. The entire section as found had at the 

 top a bed of red shale with iron concretions in it, above a bed of limestone 

 8 or 10 inches thick. Beneath this was a 12-foot bed of shale, chiefly 

 gray, including a 6-inch bed of decomposing limestone. Next, at the 

 base, came a 3-foot bed of fragmental, siliceous limestone, above 4% feet 

 of limestone the upper half of which was very fossiliferous, the list includ- 

 ing Hustedia mormoni, Composita sub t Hit a, many Reticulata perplexa, 

 Spirifer cameratus, large Fusulina cylindrica, Naticoysis, Euomphalus, 

 a pelecypod, Phillipsia major, and crinoid stems; no Marginifera muri- 

 cata were noted. This larger assemblage of fossils than found near Earl- 

 ham and Stuart may be due to the longer time spent in the search, though 

 the time was limited. The relative abundance of Reticularia perplexa 

 was certainly striking, even though that fossil does have a long range. 

 These beds are 80 miles from Stuart, but they are in the direction of 

 strike of the region and are the only beds that show a marked similarity 

 to those near Stuart. The similarity is such that the writer believes the 

 beds north of Stuart and northwest of Earlham should be correlated as 

 Henrietta (Appanoose) beds. The amount of throw along the Thurman- 

 Wilson fault, as determined by Smith, 16 near Thurman, is 300 feet; as 

 determined by Tilton, 17 for southeastern Cass County, it is 284 feet, a 

 displacement that is about right to bring beds near the base of the Des 

 Moines stage near the surface. At Van Meter, a few miles east of Earl- 

 ham, and on the downthrow side of the fault, Leonard 18 mentions a mine 

 300 feet deep which he judges stops 100 feet above the base of the Des 

 Moines stage. 



The anticline that Leonard notes in Dallas County and calls the Recl- 

 field anticline 19 has the same relation to the fault that the gentle anticline 



14 John L. Tilton : Geological section along Middle River, in Central Iowa. Iowa Geo- 

 logical Survey, vol. iii, p. 135 ; Geology of Warren County, idem, vol. v ; Geology of 

 Madison County, idem, vol. vii ; Geology of Clarke County, idem, vol. xxvii. 



15 H. Foster Bain : Geology of Appanoose County. Iowa Geological Survey, vol. v, 

 1895, p. 378. Unfortunately there is no list of fossils given. 



16 George L. Smith : Carboniferous section of southwestern Iowa. Iowa Geological 

 Survey, vol. xix. p. 612. 



17 John L. Tilton: Geology of Cass County. Iowa Geological Survey, vol. xxvii, p. 211. 



18 A. G. Leonard : Geology of Dallas County. Iowa Geological Survey, vol. viii, 1897, 

 pp. 92-94. 



10 Idem, p. 91. 



