Geological Sections through the Andes of Peru and Bolivia: II—From the Port of Mollendo to the Inambari River

Abstract

I. Introduction. In a former communication to this Society, published in April 1914, I described a geological section through the South American Andes, from Arica on the Pacific coast of Northern Chile to the Bolivian Yungas. The present paper, the publication of which has been long delayed owing to the War, is a further contribution to the same series, the result of work undertaken on the Baiston Expedition to Peru. It deals with a second and parallel section drawn through the south of Peru from the port of Mollendo to the River Inambari, a tributary of the Madre de Dios, one of the head-waters of the Amazon. That part of the country illustrated in the western half of the section, which includes the important town of Arequipa and the port of Puno on Lake Titicaca, is accessible by the Southern Railway of Peru, of which we were enabled to make full use during the course of our work from Arequipa to the coast, through the kindness of Mr. McCulloch, manager for the Peruvian Corporation. I have also to thank Mr. F. A. Corry, chief engineer of the line, for the original from which the sketch-map (fig. 1) was taken. For the continuation of the section beyond Puno through the Eastern Cordillera, it was found necessary to proceed northwards as far as Tirapata, a station on the Puno-Cuzco railway, whence access could be gained, by the trail of the Inambari Rubber Company, to the forested region of the Montana. The railway