SUEFACE DEPOSITS. 121 



of wood and twigs, all of which, so far as yet examined, 

 prove to possess the structure peculiar to conifers. It is 

 worthy of remark in this connection, that no conifers having 

 a wet habitat as these evidently had, are now to be found 

 living within the State. 



Several fragments of the elytra of a coleopterous insect 

 were found in the ancient peat of both Davenport and Iowa 

 City; but their specific and generic relations have not been 

 determined. 



The peat of both these localities is referred to the age of 

 the Terrace epoch, although at one time it was thought the 

 one near Iowa City might prove to be of pre-glacial origin. 



A small deposit of similar ancient peat was also discovered 

 in Adair county, and will be- found mentioned in the 

 description of the geology of that county in another part of 

 this report. 



It will be observed that in the foregoing discussion of all 

 that pertains to the post-tertiary geology of Iowa, it is 

 assumed that no appreciable changes in the elevation of the 

 surface above the sea, have taken place during that time. It 

 seems unmistakably evident that all our rivers have eroded 

 their own valleys, and produced their own terraces without 

 the aid of any elevation or depression of the surface. It is for 

 this reason that no reference is made to the Champlain epoch 

 in discussing Iowa geology. We date the Terrace epoch, 

 from the recedence of the glaciers to the present time. 



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