CHAPTER I 



GEOLOGY OF SOUTHWESTERN IOWA. 

 1. GENERAL DESCRIPTION. 



This region comprises the following fourteen counties of 

 the three southern tiers, namely: Madison, Clarke, Decatur, 

 Adair, Union, Binggold, Cass, Adams, Taylor, Pottawatta- 

 mie, Montgomery, Page, Mills, and Fremont. It has the 

 Iowa and Missouri State line for its southern, and the 

 Missouri river for its western boundary. It is about one 

 hundred and fourteen miles long from east to west, and 

 almost sixty -five miles wide from north to south, and contains 

 more than seven thousand five hundred square miles of 

 surface. 



Although the region is so large, its geology is nevertheless 

 very simple; for with the exception of the presence of the 

 southern extremity of the Cretaceous formations, exposures 

 of which are occasionally seen in Cass, Montgomery, Mills, 

 and Pottawattamie counties, the whole region is occupied 

 by the Upper coal-measure formation alone, a general 

 description of which has been given upon previous pages. 

 That is, with the exception named, this formation immedi- 

 ately underlies the Drift and Bluff Deposits. These last named 

 deposits, which have also been described, constitute the soil 

 and subsoil of the regions they respectively occupy. 



With the exception of parts of Madison, Adair, and 

 Clarke counties, the whole region is drained by tributaries 



of the Missouri river; while the other portions of the three 



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