PAET II. 



GENERAL GEOLOGY 



EXPLANATORY REMARKS. 



The outline of surface occupied by each formation or group 

 is indicated upon a geological map accompanying this report, 

 with as mnch precision as it has been practicable to attain, 

 and to illustrate upon so small a map. The Drift Deposit of 

 Iowa is so deep, especially in its northern and northwestern 

 parts, and has there so completely hidden the underlying 

 strata from view, that it has been found impossible to lay 

 down upon the map the exact boundaries of each formation 

 or group which exists in that part of the State. Therefore, in 

 the preparation of this map, those boundaries alone are 

 indicated concerning the correctness of which little or no 

 doubt is felt, while the large stoneless region referred to in 

 Part I, is left uncolored. 



Three general sections, constructed upon lines, traversing 

 the State in different directions, also accompany the map. 

 That part of those sections which traverses the stoneless 

 region is given in dotted lines, to show that doubt exists as 

 to the real position of the formations there. 



In the preparation of the map-model which accompanies 

 Part I, and which is intended for purposes of general illustra- 

 tion only, the sheets are cut for the northern and northwestern 

 part of the State as, after considering all the evidence it has 



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