BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 VOL. 17, PP. 275-284, PLS. 32-34 JUNE 23, 1906 



GEOLOGY OF THE LOWER COLORADO RIVER* 



BY WILLIS T. LEE 



(Presented in abstract before the Society December 29, 1905) 



CONTENTS 



Page 



Introduction 275 



Geographic distribution of detritus 270 



Character of the detrital formations 270 



Means of correlation 277 



General description of the lower part of the Colorado river 277 



Early geologic events 277 



Recent geologic events 279 



Introductory statements 27?. 



Canyon cutting (1 ) 280 



Gravel deposits and lava flows 280 



Canyon cutting (2) 280 



Deposition of gravels 282 



Canyon cutting (3) 282 



Formation of flood-plains '. 282 



Correlations 283 



Tabular resume 284 



Introduction 



The purpose of this paper is to describe in a general way the occur- 

 rence of certain detrital accumulations in the southwestern part of the 

 United States, and to suggest a line of investigation which apparently 

 makes clear the recent geologic history of that region. The statements 

 contained in the paper are supported by evidence which must be here 

 omitted for want of space. On the other hand, the fact is recognized that 

 in a region so extensive and so little known as that in which the detrital 

 accumulations occur, much more work must be done before final conclu- 

 sions can be reached. The observations on which this paper is based were 

 made mainly during rapid reconnaissance trips in western Arizona, 

 although detailed work was done in a number of places in the Southwest, 



* Published by permission of the Director of the United States Geological Survey. 

 XXIII — Bull. Geol. Soc. Am., Vol. 17. 1905 (275) 



