UNIVERSITY OF CALIFORNIA PUBLICATIONS 



BULLETIN OF THE DEPARTMENT OF 



GEOLOGY 



Vol. 9, No. 3, pp. 23-48, pis. 1-2, 4 text figs. Issued November 6, 1915 



THE EPIGENE PROFILES OF THE DESERT 



BY 



ANDREW C. LAW SON 



CONTENTS 



PAliE 



Rainless Regions : 23 



Arid Regions 25 



Elements of the Profile 25 



Degradation 28 



Alluviation 30 



Truncation 31 



The Resulting Surface 32 



The Panfan stage of the Geomorphic Cycle of the Desert 33 



The Suballuvial Bench 34 



The Alluvial Embankment 38 



The Subaerial Front 42 



The Ultimate Stage 44 ■ 



RAINLESS REGIONS 



In a rainless region an uplifted land-mass, an orogenic block, is 

 subject to degradation by : 



1. The process of mechanical disintegration at the surface due to 

 differential dilations and contractions under varying temperatures ; (2) 

 the gravitational transportation of the fragments thus detached from 

 higher to lower levels; (3) the transportation by the wind of such of 

 these detached fragments as may be small enough to be removed: (4) 

 the corrasive action of wind-moved detritus and the removal of the 

 products of such corrasion by the wind. 



The relative efficacy of these processes in a purely a priori dis- 

 cussion depends altogether upon what assumptions are made. If. for 



* Read before Geological Society of America at the Berkeley Meeting, Aug., 

 1915. 



AT 



( NOV 16 1915 



