BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 33, pp. 605-616 September 30, 1922 



VOLCANIC ASH BED IN THE OBDOVICIAN OF TENNESSEE, 

 KENTUCKY, AND ALABAMA 1 



BY WILBUR A. NELSON 



{Read before the Society December 29, 1921) 



CONTENTS 



Page 



Introduction 605 



Extent of ash deposit 606 



Description of bentonite outcrops 606 



Conditions existing at the time of ash deposition 608 



Thickness of bentonite layer , 609 



Location of ancient volcano 610 



Amount of ash ejected 610 



Ash falls from historic volcanoes 611 



Ash falls from prehistoric volcanoes 611 



Extent of ash falls during Lowville time 611 



Settling of volcanic ash in salt and fresh water 612 



Evidence of igneous activity in eastern Kentucky 613 



Report of E. S. Larsen on Tennessee bentonite 613 



Analyses of bentonite and leverrierite 614 



A new theory of the formation of bauxite deposits 615 



Introduction 



The determination of a greenish, sticky, clay forming bed about two 

 feet thick, observed in Bedford County, Tennessee, in 1920, as bentonite, 

 an altered volcanic ash, 2 started a search for additional outcrops of this 

 deposit and the collection of data that would bear on its origin, extent, 

 and method of deposition. This paper is primarily a progress report on 

 this subject, on which it is hoped much additional work will be done. 

 The first observation of this clay deposit was made at the settlement of 

 Singleton, in Bedford County, Tennessee, at which place it measured 21 

 inches thick. 



1 Manuscript received by the Secretary of the Society February 23, 1922. 



2 E. S. Larsen : Personal letter, 1921. 



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