BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 22, pp. 687-714 December 14, 1911 



MID-CONTINENTAL EOLATION^ 



BY CHARLES R. KEYES 



{Read by title before the Society December 27, 1910) 



CONTENTS 



Page 



Introductory 1 687 



Dominant characteristics of the Great Plains , 689 



Explanations of Plains formation 690 



General statement 690 



Marine deposition 690 



Lacustrine origin 691 



Stream planation 692 



Fluviatile aggradation 693 



Wind-scour and its effects 693 



Aeroposition east of the Rocky Mountains 694 



Origin of eolic continental deposits 695 



Relation of areas of denudation and deposition 695 



Climatic peculiarities 695 



Deflation in dry regions 690 



Disposition of exported dusts from desert tracts 007 



Characteristics of eolic deposits 699 



Relations of areas of deflation and aeroposition 702 



Eolic significance of certain Great Plains features 708 



Vastness and evenness of surface 703 



Dissonance of stratification 704 



Homogeneity of Plains deposits 705 



Similarity of Plains soils to loess 706 



Identity of Plains deposits with adobe 707 



Distribution of coarser detrital materials 707 



Mingling of eolic and aqueous effects 709 



Rock-floor of the Plains along the Rocky Mountain front 710 



Ruling gradient of Plains surface 710 



Objections to lacustrine theory 710 



Weakness of the fluviatile hypothesis 711 



Recapitulation 713 



Introductory 



In the recent considerations of siibaerial formations so many novelties 

 enter that in many an old and well known field a new interest is aroused. 



1 Manuscript received by the Secretary of the Society August 11, 1011. (687) 



