THE 



QUARTERLY JOURNAL 



OF 



THE GEOLOGICAL SOCIETY OF LONDON. 



Vol. LXX. 



1. Geological Sections through the Andes of Peru and 

 Bolivia : I — From the Coast at Arica in the North of 

 Chile to La Paz and the Bolivian" ' Yungas.' By 

 James Archibald Douglas, M.A., B.Sc, F.GLS. (Bead 

 November 5th, 1913.) 



[Plates I-X.] 



Contents. _ 



Page 



I. Introduction 1 



II. General Outline of the Physiography of the Peruvian and 



North Bolivian Andes 2 



III. Main Topographical Features of the Country included in 



the First Section (Arica to the Bolivian ' Yungas ') 3 



IV. Geological Description of the Section from Arica to the 



Bolivian ' Yungas ' 6 



(i) The Coastal Region and the Western Cordillera, 

 (ii) The Altaplanicie, or High-Level Bolivian Plateau, 

 (iii) The Eastern Cordillera and the Amazon Slopes. 



V. General Summary and Conclusions 46 



VI. Bibliography 49 



I. Introduction. 



This paper deals with the geological structure of a part of the 

 South American Andes, as illustrated by a horizontal section drawn 

 from the port of Arica in the extreme north of Chile (formerly 

 Peruvian territory), across the mountain -ranges or ' Cordilleras,' to 

 Q. J. G. S. No. 277. b 



