524 IOWA ACADEMY OF SCIENCE Vol. XXV, 1918 



Bluffs for the lower one hundred and twenty-five feet reaching 

 from the Rulo to the Nodaway coal, thus returning to the orig- 

 inal use of the name as given by Broadhead. This is more cor- 

 rect than the former use of the name and is acceptable to the 

 writer. 



However, the Nemaha of Condra and Bengtson, and the Mc- 

 Kissicks Grove of Smith should have no standing in geology as 

 both of these formations are included in the Atchison county 

 Group of Broadhead, who in 1872 gave this name to a series of 

 strata in Atchison county, ^Missouri, exposed in the bluffs along 

 Missouri river. At the base of the exposure w^as a limestone, 

 number 28 of his section, now known to be the Burlingame, the 

 third limestone ledge below the Tarkio, and the section extended 

 upward to a red shale, his number 3, the latest of the Pennsyl- 

 vanian found east of IVIissouri river. Broadhead 's Atchison 

 county Group was accurately defined according to modern stand- 

 ards. This section has recently been reviewed in the field and 

 found to be correct in detail. No geologist of the present time 

 having any regard for the permanency of his own work can af- 

 ford to ignore the accurate work of his predecessors. Keyes' At- 

 chison formation has no application here as he places the lower 

 limit of his Atchison at the Forbes at least one himdred and fifty 

 feet lower than the base of the Atchison county Group. 



During the past summer several days were spent in tracing 

 the different outcrops and strata exposed in the base of the Mis- 

 souri river bluff's, from two miles south of Thurman along the 

 bluff road north to Wabonsie creek, a distance of nearly seven 

 miles. The utmost care was exercised to secure accurate results 

 in this work as the object was to definitely locate the fault line 

 north of Thurman and obtain a solution of one of the greatest 

 problems in Iowa geology. Some of the most intricate geologic 

 structure in the state is present in the vicinity of Lake Wabonsie 

 and requires additional study. The stratified rocks in this part 

 of Iowa are so obscured by heavy deposits of drift, and in the 

 vicinity of iMissouri river by loess, that the effect on the local ge- 

 olog>^ caused by the Jones Point deformation, the interpretation 

 of which is fraught with difficulty, is liable to be misconstrued. 

 The writer has not spared time and effort to give a correct solu- 

 tion to some of these problems but much remains for future in- 

 vestigation, and his present interpretations may be greatly modi- 

 fied. 



