CENTURY OF IOWA GEOLOGY 425 



Nevertheless, in Iowa, in spite of an adverse consensus of opin- 

 ion, the pecuHar distribution of the loess loams appeared to be such 

 as seriously to call into question the verity of the accepted notion. 

 On Capitol Hill, in Des Moines, thick loess deposits were displayed 

 interbedded with tills. Later these sections gave first intimation of 

 the possible wind-born character of the formation. 



In after years loess was observed in the actual process of forma- 

 tion by means of the dusts blown off the Missouri river sandbars 

 and from the dry upland plains of Kansas.-^ Still later the loess 

 was identified with the adobe soils of western deserts. 



It was on Capitol Hill, also, that first clues were found pointing 

 to that wonderful interlocking of the continuous adobe mantle of the 

 Southwest with the glacial till sheets of the Northeast.-*. 



DIASTROPHIC TAXONOMY OF ROCK TERRANES 



One of the larger problems connected with the coal investigations 

 undertaken by the state survey was following the strand-line of the 

 continental interior seas. The usual criteria of fossils proved un- 

 available partly because of the relative shortness of the time in- 

 volved and partly for reason of the constant recurrence of the 

 faunas. Although the reappearance of organic forms at successive 

 horizons was no doubt a direct function of the oscillation of the 

 old shore-line the nature of the biotic changes admitted of no defi- 

 nite characteristics upon which classificatory schemes could be 

 established. 



Recourse, therefore,- had to be made directly to the coal measures 

 themselves for testimony concerning their history. It so chanced 

 that upon the epicontinental sea area the episodes of stratigraphical 

 development proved to be unusually well marked. The practical 

 outcome of the new plan was strongly contrasted by comparison of 

 the resulting summary-^ of the Iowa formations with the general 

 sections previously outlined. 



The principles involved promised to be more than merely local in 

 application. In recent years they were widely applied to distant 

 parts of our continent. They were finally recognized the world over. 

 It is probable that before many years have passed they will have 

 entirely supplanted the usual criteria of the organic remains. In 

 stratigraphy, therefore, diastrophism takes on a fundamental and 

 genetic character. 



"Am. Jour. Sci., (3), Vol. VI, pp. 299-304, 1898. 

 "Am. Jour. Sci., (4), Vol. XXXIII, pp. 32-34, 1912. 

 "Iowa Geol. Surv., Vol. XXII, pp. 154-155, 1913. 



